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Sample records for 1-aminocyclopropane-1-carboxylic acid transported

  1. Transport and Metabolism of 1-Aminocyclopropane-1-carboxylic Acid in Sunflower (Helianthus annuus L.) Seedlings 1

    PubMed Central

    Finlayson, Scott A.; Foster, Kenneth R.; Reid, David M.

    1991-01-01

    Transport and metabolism of [2,3-14C] 1-aminocyclopropane-1-carboxylic acid (ACC) from roots to shoots in 4-day-old sunflower (Helianthus annuus L.) seedlings were studied. [14C]ACC was detected in, and 14C2H4 was evolved from, shoots 0.5 hours after [14C]ACC was supplied to roots. Ethylene emanation from the shoots returned to normal levels after 6 hours. The roots showed a similar pattern, although at 24 hours ethylene emanation was still slightly higher than in those plants that did not receive ACC. [14C]N-malonyl-ACC (MACC) was detected in both tissues at all times sampled. [14C]MACC levels surpassed [14C]ACC levels in the shoot at 2 hours, whereas [14C]MACC levels in the root remained below [14C]ACC levels until 6 hours, after which they were higher. Thin-layer chromatography analysis identified [14C] ACC in 1-hour shoot extracts, and [14C]MACC was identified in root tissues at 1 and 12 hours after treatment. [14C]ACC and [14C] MACC in the xylem sap of treated seedlings were identified by thin-layer chromatography. Xylem transport of [14C]ACC in treated seedlings, and transport of ACC in untreated seedlings, was confirmed by gas chromatography-mass spectrometry. Some evidence for the presence of [14C]MACC in xylem sap in [14C]ACC-treated seedlings is presented. A substantial amount of radioactivity in both ACC and MACC fractions was detected leaking from the roots over 24 hours. A second radiolabeled volatile compound was trapped in a CO2-trapping solution but not in mercuric perchlorate. Levels of this compound were highest after the peak of ACC levels and before peak MACC levels in both tissues, suggesting that an alternate pathway of ACC metabolism was operating in this system. PMID:16668342

  2. 1-Aminocyclopropane-1-Carboxylic Acid Transported from Roots to Shoots Promotes Leaf Abscission in Cleopatra Mandarin (Citrus reshni Hort. ex Tan.) Seedlings Rehydrated after Water Stress.

    PubMed

    Tudela, D; Primo-Millo, E

    1992-09-01

    The effect of water stress and subsequent rehydration on 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase activity, ethylene production, and leaf abscission was studied in Cleopatra mandarin (Citrus reshni Hort. ex Tan.) seedlings. Leaf abscission occurred when drought-stressed plants were allowed to rehydrate, whereas no abscission was observed in plants under water stress conditions. In roots of water-stressed plants, a high ACC accumulation and an increase in ACC synthase activity were observed. Neither increase in ACC content nor significant ethylene production were detected in leaves of water-stressed plants. After rehydration, a sharp rise in ACC content and ethylene production was observed in leaves of water-stressed plants. Content of ACC in xylem fluid was 10-fold higher in plants rehydrated for 2 h after water stress than in nonstressed plants. Leaf abscission induced by rehydration after drought stress was inhibited when roots or shoots were treated before water stress with aminooxyacetic acid (AOA, inhibitor of ACC synthase) or cobalt ion (inhibitor of ethylene-forming enzyme), respectively. However, AOA treatments to shoots did not suppress leaf abscission. The data indicate that water stress promotes ACC synthesis in roots of Cleopatra mandarin seedlings. Rehydration of plants results in ACC transport to the shoots, where it is oxidized to ethylene. Subsequently, this ethylene induces leaf abscission.

  3. Genetic identification of ACC-RESISTANT2 reveals involvement of LYSINE HISTIDINE TRANSPORTER1 in the uptake of 1-aminocyclopropane-1-carboxylic acid in Arabidopsis thaliana.

    PubMed

    Shin, Kihye; Lee, Sumin; Song, Won-Yong; Lee, Rin-A; Lee, Inhye; Ha, Kyungsun; Koo, Ja-Choon; Park, Soon-Ki; Nam, Hong-Gil; Lee, Youngsook; Soh, Moon-Soo

    2015-03-01

    1-Aminocyclopropane-1-carboxylic acid (ACC) is a biosynthetic precursor of ethylene, a gaseous plant hormone which controls a myriad of aspects of development and stress adaptation in higher plants. Here, we identified a mutant in Arabidopsis thaliana, designated as ACC-resistant2 (are2), displaying a dose-dependent resistance to exogenously applied ACC. Physiological analyses revealed that mutation of are2 impaired various aspects of exogenous ACC-induced ethylene responses, while not affecting sensitivity to other plant hormones during seedling development. Interestingly, the are2 mutant was normally sensitive to gaseous ethylene, compared with the wild type. Double mutant analysis showed that the ethylene-overproducing mutations, eto1 or eto3, and the constitutive ethylene signaling mutation, ctr1 were epistatic to the are2 mutation. These results suggest that the are2 mutant is not defective in ethylene biosynthesis or ethylene signaling per se. Map-based cloning of ARE2 demonstrated that LYSINE HISTIDINE TRANSPORTER1 (LHT1), encoding an amino acid transporter, is the gene responsible. An uptake experiment with radiolabeled ACC indicated that mutations of LHT1 reduced, albeit not completely, uptake of ACC. Further, we performed an amino acid competition assay and found that two amino acids, alanine and glycine, known as substrates of LHT1, could suppress the ACC-induced triple response in a LHT1-dependent way. Taken together, these results provide the first molecular genetic evidence supporting that a class of amino acid transporters including LHT1 takes part in transport of ACC, thereby influencing exogenous ACC-induced ethylene responses in A. thaliana. PMID:25520403

  4. 1-aminocyclopropane-1-carboxylic acid (ACC) in plants: more than just the precursor of ethylene!

    PubMed Central

    Van de Poel, Bram; Van Der Straeten, Dominique

    2014-01-01

    Ethylene is a simple two carbon atom molecule with profound effects on plants. There are quite a few review papers covering all aspects of ethylene biology in plants, including its biosynthesis, signaling and physiology. This is merely a logical consequence of the fascinating and pleiotropic nature of this gaseous plant hormone. Its biochemical precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) is also a fairly simple molecule, but perhaps its role in plant biology is seriously underestimated. This triangularly shaped amino acid has many more features than just being the precursor of the lead-role player ethylene. For example, ACC can be conjugated to three different derivatives, but their biological role remains vague. ACC can also be metabolized by bacteria using ACC-deaminase, favoring plant growth and lowering stress susceptibility. ACC is also subjected to a sophisticated transport mechanism to ensure local and long-distance ethylene responses. Last but not least, there are now a few exciting studies where ACC has been reported to function as a signal itself, independently from ethylene. This review puts ACC in the spotlight, not to give it the lead-role, but to create a picture of the stunning co-production of the hormone and its precursor. PMID:25426135

  5. Ethylene Production and 1-Aminocyclopropane-1-Carboxylic Acid Conjugation in Thermoinhibited Cicer arietinum L. Seeds.

    PubMed

    Gallardo, M; Delgado, M del M; Sánchez-Calle, I M; Matilla, A J

    1991-09-01

    The effect of supraoptimal temperatures (30 degrees C, 35 degrees C) on germination and ethylene production of Cicer arietinum (chick-pea) seeds was measured. Compared with a 25 degrees C control, these temperatures inhibited both germination and ethylene production. The effect of supraoptimal temperatures could be alleviated by treating the seeds with ethylene. It was concluded that one effect of high temperature on germination was due to its negative effect on ethylene production. This inhibitory effect of high temperature was due to increased conjugation of 1-aminocyclopropane-1-carboxylic acid to 1-(malonylamino)cyclopropane-1-carboxylic acid and to an inhibition of ethylene-forming enzyme activity.

  6. 1-Aminocyclopropane-1-carboxylic acid oxidase: insight into cofactor binding from experimental and theoretical studies.

    PubMed

    Brisson, Lydie; El Bakkali-Taheri, Nadia; Giorgi, Michel; Fadel, Antoine; Kaizer, József; Réglier, Marius; Tron, Thierry; Ajandouz, El Hassan; Simaan, A Jalila

    2012-08-01

    1-Aminocyclopropane-1-carboxylic acid oxidase (ACCO) is a nonheme Fe(II)-containing enzyme that is related to the 2-oxoglutarate-dependent dioxygenase family. The binding of substrates/cofactors to tomato ACCO was investigated through kinetics, tryptophan fluorescence quenching, and modeling studies. α-Aminophosphonate analogs of the substrate (1-aminocyclopropane-1-carboxylic acid, ACC), 1-aminocyclopropane-1-phosphonic acid (ACP) and (1-amino-1-methyl)ethylphosphonic acid (AMEP), were found to be competitive inhibitors versus both ACC and bicarbonate (HCO(3)(-)) ions. The measured dissociation constants for Fe(II) and ACC clearly indicate that bicarbonate ions improve both Fe(II) and ACC binding, strongly suggesting a stabilization role for this cofactor. A structural model of tomato ACCO was constructed and used for docking experiments, providing a model of possible interactions of ACC, HCO(3)(-), and ascorbate at the active site. In this model, the ACC and bicarbonate binding sites are located close together in the active pocket. HCO(3)(-) is found at hydrogen-bond distance from ACC and interacts (hydrogen bonds or electrostatic interactions) with residues K158, R244, Y162, S246, and R300 of the enzyme. The position of ascorbate is also predicted away from ACC. Individually docked at the active site, the inhibitors ACP and AMEP were found coordinating the metal ion in place of ACC with the phosphonate groups interacting with K158 and R300, thus interlocking with both ACC and bicarbonate binding sites. In conclusion, HCO(3)(-) and ACC together occupy positions similar to the position of 2-oxoglutarate in related enzymes, and through a hydrogen bond HCO(3)(-) likely plays a major role in the stabilization of the substrate in the active pocket. PMID:22711330

  7. Isolation and Molecular Characterization of 1-Aminocyclopropane-1-carboxylic Acid Synthase Genes in Hevea brasiliensis

    PubMed Central

    Zhu, Jia-Hong; Xu, Jing; Chang, Wen-Jun; Zhang, Zhi-Li

    2015-01-01

    Ethylene is an important factor that stimulates Hevea brasiliensis to produce natural rubber. 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a rate-limiting enzyme in ethylene biosynthesis. However, knowledge of the ACS gene family of H. brasiliensis is limited. In this study, nine ACS-like genes were identified in H. brasiliensis. Sequence and phylogenetic analysis results confirmed that seven isozymes (HbACS1–7) of these nine ACS-like genes were similar to ACS isozymes with ACS activity in other plants. Expression analysis results showed that seven ACS genes were differentially expressed in roots, barks, flowers, and leaves of H. brasiliensis. However, no or low ACS gene expression was detected in the latex of H. brasiliensis. Moreover, seven genes were differentially up-regulated by ethylene treatment.These results provided relevant information to help determine the functions of the ACS gene in H. brasiliensis, particularly the functions in regulating ethylene stimulation of latex production. PMID:25690030

  8. A strategy for promoting astaxanthin accumulation in Haematococcus pluvialis by 1-aminocyclopropane-1-carboxylic acid application.

    PubMed

    Lee, Changsu; Choi, Yoon-E; Yun, Yeoung-Sang

    2016-10-20

    The green algae Haematococcus pluvialis is a freshwater unicellular microalga belonging to Chlorophyceae. It is one of the best natural sources of astaxanthin, a secondary metabolite commonly used as an antioxidant and anti-inflammatory agent. Due to the importance of astaxanthin, various efforts have been made to increase its production. In this study, we attempted to develop a strategy for promoting astaxanthin accumulation in H. pluvialis using 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene (normally known as an aging hormone in plants). Our results demonstrated that ACC could enhance the growth of H. pluvialis, thereby promoting astaxanthin accumulation. Therefore, ACC has an indirect influence on astaxanthin production. We further verified the effect of ACC with a direct treatment of ethylene originated from banana peels. These results indicate that ethylene could be applied as an indirect method for enhancing growth and astaxanthin biosynthesis in H. pluvialis. PMID:27544287

  9. In vitro germination of Striga hermonthica and Striga aspera seeds by 1-aminocyclopropane-1-carboxylic acid.

    PubMed

    Rugutt, Kipngeno J; Rugutt, Joseph K; Berner, Dana K

    2003-01-01

    Treatment of conditioned seeds of four isolates of Striga hermonthica and one isolate of Striga aspera with various concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), caused complex stimulation of germination patterns. GR 24, the strigol analogue served as a positive control and its stimulatory activity was comparable to that of ACC. When conditioned Striga seeds were treated with negative control that did not contain ACC, the stimulatory effect was lost. Overall, the germination data suggested a hormonal mode of action by ACC, which involves indirect stimulation of biosynthesis of ethylene that then triggers seed germination. The various mechanisms that have been proposed for the chemical and biological oxidation of ACC to generate ethylene are discussed.

  10. Tolerance of transgenic canola expressing 1-aminocyclopropane-1-carboxylic acid deaminase to growth inhibition by nickel.

    PubMed

    Stearns, Jennifer C; Shah, Saleh; Greenberg, Bruce M; Dixon, D George; Glick, Bernard R

    2005-07-01

    Plant growth-promoting bacteria are useful to phytoremediation strategies in that they confer advantages to plants in contaminated soil. When plant growth-promoting bacteria contain the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, the bacterial cell acts as a sink for ACC, the immediate biosynthetic precursor of the plant growth regulator ethylene thereby lowering plant ethylene levels and decreasing the negative effects of various environmental stresses. In an effort to gain the advantages provided by bacterial ACC deaminase in the phytoremediation of metals from the environment two transgenic canola lines with the gene for this enzyme were generated and tested. In these transgenic canola plants, expression of the ACC deaminase gene is driven by either tandem constitutive cauliflower mosaic virus (CaMV) 35S promoters or the root specific rolD promoter from Agrobacterium rhizogenes. Following the growth of transgenic and non-transformed canola in nickel contaminated soil, it was observed that the rolD plants demonstrate significantly increased tolerance to nickel compared to the non-transformed control plants.

  11. Ethylene-Enhanced 1-Aminocyclopropane-1-carboxylic Acid Synthase Activity in Ripening Apples 1

    PubMed Central

    Bufler, Gebhard

    1984-01-01

    Apples (Malus sylvestris Mill, cv Golden Delicious) were treated before harvest with aminoethoxyvinylglycine (AVG). AVG is presumed to reversibly inhibit 1-aminocyclopropane-1-carboxylic acid (ACC) activity, but not the formation of ACC synthase. AVG treatment effectively blocked initiation of autocatalytic ethylene production and ripening of harvested apples. Exogenous ethylene induced extractable ACC synthase activity and ripening in AVG-treated apples. Removal of exogenous ethylene caused a rapid decline in ACC synthase activity and in CO2 production. The results with ripened, AVG-treated apples indicate (a) a dose-response relationship between ethylene and enhancement of ACC synthase activity with a half-maximal response at approximately 0.8 μl/l ethylene; (b) reversal of ethylene-enhanced ACC synthase activity by CO2; (c) enhancement of ACC synthase activity by the ethylene-activity analog propylene. Induction of ACC synthase activity, autocatalytic ethylene production, and ripening of preclimacteric apples not treated with AVG were delayed by 6 and 10% CO2, but not by 1.25% CO2. However, each of these CO2 concentrations reduced the rate of increase of ACC synthase activity. PMID:16663569

  12. Changes in 1-aminocyclopropane-1-carboxylic-acid content of cut carnation flowers in relation to their senescence.

    PubMed

    Bufler, G; Mor, Y; Reid, M S; Yang, S F

    1980-12-01

    The rise in ethylene production accompanying the respiration climacteric and senescence of cut carnation flowers (Dianthus caryophyllus L. cv. White Sim) was associated with a 30-fold increase in the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in the petals (initial content 0.3 nmol/g fresh weight). Pretreatment of the flowers with silver thiosulfate (STS) retarded flower senescence and prevented the increase in ACC concentration in the petals. An increase in ACC in the remaining flower parts, which appeared to precede the increase in the petals, was only partially prevented by the STS pretreatment. Addition of aminoxyacetic acid (2 mM) to the solution in which the flowers were kept completely inhibited accumulation of ACC in all flower parts.

  13. Kinetin Enhanced 1-Aminocyclopropane-1-Carboxylic Acid Utilization during Alleviation of High Temperatures Stress in Lettuce Seeds.

    PubMed

    Khan, A A; Prusinski, J

    1989-10-01

    The thermoinhibition at 35 and 32 degrees C of pregermination ethylene production and germination in lettuce (Lactuca sativa L. cv Mesa 659) seeds was synergistically or additively alleviated by 0.05 millimolar kinetin (KIN) and 10 millimolar 1-aminocyclopropane-1-carboxylic acid (ACC). The synergistic effect of KIN + ACC on ethylene production and germination at 35 degrees C was inhibited by Co(2+) (44-46%) but not by aminoethoxyvinyl glycine (AVG). The uptake of ACC by the seed was not influenced by KIN. Upon slitting of the seed coats (composed of pericarp, testa and endosperm), following the uptake of chemicals, ACC was readily converted into ethylene at all temperatures, and the synergistic effects of KIN + ACC at 35 degrees C were lost. At 35 degrees C, KIN acted synergistically with ACC or ethephon (ETH) in alleviating the osmotic restraint. At 25 degrees C, ETH was more active than KIN or KIN + ACC in overcoming the osmotic restraint. Thus, the integrity of the seed coats, the KIN-enhanced ACC utilization, and an interaction of KIN with the ethylene produced may be the basis for the synergistic or additive effects of KIN + ACC at high temperature.

  14. Differential expression of two 1-aminocyclopropane-1-carboxylic acid oxidase genes in broccoli after harvest.

    PubMed Central

    Pogson, B J; Downs, C G; Davies, K M

    1995-01-01

    Broccoli (Brassica oleracea L.) floral tissues rapidly differentiate and grow before harvest and then senesce rapidly after harvest. Associated with this postharvest deterioration is an increase in ethylene production by florets. Two cDNA clones having high nucleotide identity to sequences encoding 1-amino-cyclopropane-1-carboxylic acid (ACC) oxidase were isolated from senescing florets. The cDNAs, ACC Ox1 and ACC Ox2, apparently encode mRNAs from different genes. ACC Ox1 transcripts were found at low levels in whole florets at the time of harvest and increased markedly in abundance after harvest. ACC Ox1 transcript abundance also increased in sepals after harvest and in excised yellowing leaves. Transcripts corresponding to ACC Ox2 were found exclusively within the reproductive structures. These ACC Ox2 transcripts were absent at harvest but started to increase in abundance within 2 h of harvest and then accumulated to high levels. Hormone treatment did not alter the abundance of ACC Ox1 transcripts, whereas ACC Ox2 transcripts increased in abundance after treatment with abscisic acid and propylene. Wounding did not affect the levels of ACC Ox1 or Ox2 transcripts after harvest. At harvest, individual broccoli florets were closed and remained unpollinated. We propose a model whereby the rapid increase in ACC Ox1 and Ox2 transcript abundance after harvest contributes to increased ethylene production by florets. This ethylene may regulate aspects of postharvest senescence, in particular chlorophyll loss. PMID:7610162

  15. A fifth member of the tomato 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene family harbours a leucine zipper and is anaerobically induced.

    PubMed

    Sell, Simone; Hehl, Reinhard

    2005-02-01

    Using the leucine zipper domain of a small anaerobically induced bZIP transcription factor in a yeast two hybrid screen, anaerobically induced genes were identified. One peptide corresponds to an anaerobically induced IDS4-like protein that maybe involved in G-protein signaling. Surprisingly, another interacting peptide corresponds to a novel anaerobically induced 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, designated ACO5. ACO5 harbours a leucine zipper and transcription is mainly induced in fruits and to a lesser extend in leaves. The role of ACO5 in the low oxygen response of tomato is discussed. PMID:16040352

  16. RNA interference of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1 and ACO2) genes expression prolongs the shelf life of Eksotika (Carica papaya L.) papaya fruit.

    PubMed

    Sekeli, Rogayah; Abdullah, Janna Ong; Namasivayam, Parameswari; Muda, Pauziah; Abu Bakar, Umi Kalsom; Yeong, Wee Chien; Pillai, Vilasini

    2014-06-19

    The purpose of this study was to evaluate the effectiveness of using RNA interference in down regulating the expression of 1-aminocyclopropane-1-carboxylic acid oxidase gene in Eksotika papaya. One-month old embryogenic calli were separately transformed with Agrobacterium strain LBA 4404 harbouring the three different RNAi pOpOff2 constructs bearing the 1-aminocyclopropane-1-carboxylic acid oxidase gene. A total of 176 putative transformed lines were produced from 15,000 calli transformed, selected, then regenerated on medium supplemented with kanamycin. Integration and expression of the targeted gene in putatively transformed lines were verified by PCR and real-time RT-PCR. Confined field evaluation of a total of 31 putative transgenic lines planted showed a knockdown expression of the targeted ACO1 and ACO2 genes in 13 lines, which required more than 8 days to achieve the full yellow colour (Index 6). Fruits harvested from lines pRNAiACO2 L2-9 and pRNAiACO1 L2 exhibited about 20 and 14 days extended post-harvest shelf life to reach Index 6, respectively. The total soluble solids contents of the fruits ranged from 11 to 14° Brix, a range similar to fruits from non-transformed, wild type seed-derived plants.

  17. Complementary DNA cloning of the pear 1-aminocyclopropane-1-carboxylic acid oxidase gene and agrobacterium-mediated anti-sense genetic transformation.

    PubMed

    Qi, Jing; Dong, Zhen; Zhang, Yu-Xing

    2015-12-01

    The aim of the present study was to genetically modify plantlets of the Chinese yali pear to reduce their expression of ripening-associated 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and therefore increase the shelf-life of the fruit. Primers were designed with selectivity for the conserved regions of published ACO gene sequences, and yali complementary DNA (cDNA) cloning was performed by reverse transcription quantitative polymerase chain reaction (PCR). The obtained cDNA fragment contained 831 base pairs, encoding 276 amino acid residues, and shared no less than 94% nucleotide sequence identity with other published ACO genes. The cDNA fragment was inversely inserted into a pBI121 expression vector, between the cauliflower mosaic virus 35S promoter and the nopaline synthase terminator, in order to construct the anti‑sense expression vector of the ACO gene; it was transfected into cultured yali plants using Agrobacterium LBA4404. Four independent transgenic lines of pear plantlets were obtained and validated by PCR analysis. A Southern blot assay revealed that there were three transgenic lines containing a single copy of exogenous gene and one line with double copies. The present study provided germplasm resources for the cultivation of novel storage varieties of pears, therefore providing a reference for further applications of anti‑sense RNA technology in the genetic improvement of pears and other fruit.

  18. Differential Expression of 1-Aminocyclopropane-1-Carboxylate Synthase Genes during Orchid Flower Senescence Induced by the Protein Phosphatase Inhibitor Okadaic Acid1

    PubMed Central

    Wang, Ning Ning; Yang, Shang Fa; Charng, Yee-yung

    2001-01-01

    Applying 10 pmol of okadaic acid (OA), a specific inhibitor of type 1 or type 2A serine/threonine protein phosphatases, to the orchid (Phalaenopsis species) stigma induced a dramatic increase in ethylene production and an accelerated senescence of the whole flower. Aminoethoxyvinylglycine or silver thiosulfate, inhibitors of ethylene biosynthesis or action, respectively, effectively inhibited the OA-induced ethylene production and retarded flower senescence, suggesting that the protein phosphatase inhibitor induced orchid flower senescence through an ethylene-mediated signaling pathway. OA treatment induced a differential expression pattern for the 1-aminocyclopropane-1-carboxylic acid synthase multigene family. Accumulation of Phal-ACS1 transcript in the stigma, labelum, and ovary induced by OA were higher than those induced by pollination as determined by “semiquantitative” reverse transcriptase-polymerase chain reaction. In contrast, the transcript levels of Phal-ACS2 and Phal-ACS3 induced by OA were much lower than those induced by pollination. Staurosporine, a protein kinase inhibitor, on the other hand, inhibited the OA-induced Phal-ACS1 expression in the stigma and delayed flower senescence. Our results suggest that a hyper-phosphorylation status of an unidentified protein(s) is involved in up-regulating the expression of Phal-ACS1 gene resulting in increased ethylene production and accelerated the senescence process of orchid flower. PMID:11351088

  19. 1-Aminocyclopropane-1-carboxylic acid (ACC) deaminase-containing rhizobacteria protect Ocimum sanctum plants during waterlogging stress via reduced ethylene generation.

    PubMed

    Barnawal, Deepti; Bharti, Nidhi; Maji, Deepamala; Chanotiya, Chandan Singh; Kalra, Alok

    2012-09-01

    Ocimum sanctum grown as rain-fed crop, is known to be poorly adapted to waterlogged conditions. Many a times the crop suffers extreme damages because of anoxia and excessive ethylene generation due to waterlogging conditions present under heavy rain. The usefulness of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-containing plant growth promoting rhizobacteria was investigated under waterlogging stress. The comparison of herb yield and stress induced biochemical changes of waterlogged and non-waterlogged plants with and without ACC deaminase-containing microbiological treatments were monitored in this study. Ten plant growth promoting rhizobacteria strains containing ACC-deaminase were isolated and characterized. Four selected isolates Fd2 (Achromobacter xylosoxidans), Bac5 (Serratia ureilytica), Oci9 (Herbaspirillum seropedicae) and Oci13 (Ochrobactrum rhizosphaerae) had the potential to protect Ocimum plants from flood induced damage under waterlogged glass house conditions. Pot experiments were conducted to evaluate the potential of these ACC deaminase-containing selected strains for reducing the yield losses caused by waterlogging conditions. Bacterial treatments protected plants from waterlogging induced detrimental changes like stress ethylene production, reduced chlorophyll concentration, higher lipid peroxidation, proline concentration and reduced foliar nutrient uptake. Fd2 (A. xylosoxidans) induced maximum waterlogging tolerance as treated waterlogged plants recorded maximum growth and herb yield (46.5% higher than uninoculated waterlogged plants) with minimum stress ethylene levels (53% lower ACC concentration as compared to waterlogged plants without bacterial inoculation) whereas under normal non-waterlogged conditions O. rhizosphaerae was most effective in plant growth promotion. PMID:22846334

  20. 1-Aminocyclopropane-1-carboxylic acid (ACC) deaminase-containing rhizobacteria protect Ocimum sanctum plants during waterlogging stress via reduced ethylene generation.

    PubMed

    Barnawal, Deepti; Bharti, Nidhi; Maji, Deepamala; Chanotiya, Chandan Singh; Kalra, Alok

    2012-09-01

    Ocimum sanctum grown as rain-fed crop, is known to be poorly adapted to waterlogged conditions. Many a times the crop suffers extreme damages because of anoxia and excessive ethylene generation due to waterlogging conditions present under heavy rain. The usefulness of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-containing plant growth promoting rhizobacteria was investigated under waterlogging stress. The comparison of herb yield and stress induced biochemical changes of waterlogged and non-waterlogged plants with and without ACC deaminase-containing microbiological treatments were monitored in this study. Ten plant growth promoting rhizobacteria strains containing ACC-deaminase were isolated and characterized. Four selected isolates Fd2 (Achromobacter xylosoxidans), Bac5 (Serratia ureilytica), Oci9 (Herbaspirillum seropedicae) and Oci13 (Ochrobactrum rhizosphaerae) had the potential to protect Ocimum plants from flood induced damage under waterlogged glass house conditions. Pot experiments were conducted to evaluate the potential of these ACC deaminase-containing selected strains for reducing the yield losses caused by waterlogging conditions. Bacterial treatments protected plants from waterlogging induced detrimental changes like stress ethylene production, reduced chlorophyll concentration, higher lipid peroxidation, proline concentration and reduced foliar nutrient uptake. Fd2 (A. xylosoxidans) induced maximum waterlogging tolerance as treated waterlogged plants recorded maximum growth and herb yield (46.5% higher than uninoculated waterlogged plants) with minimum stress ethylene levels (53% lower ACC concentration as compared to waterlogged plants without bacterial inoculation) whereas under normal non-waterlogged conditions O. rhizosphaerae was most effective in plant growth promotion.

  1. Gibberellic Acid, Synthetic Auxins, and Ethylene Differentially Modulate α-l-Arabinofuranosidase Activities in Antisense 1-Aminocyclopropane-1-Carboxylic Acid Synthase Tomato Pericarp Discs1

    PubMed Central

    Sozzi, Gabriel O.; Greve, L. Carl; Prody, Gerry A.; Labavitch, John M.

    2002-01-01

    α-l-Arabinofuranosidases (α-Afs) are plant enzymes capable of releasing terminal arabinofuranosyl residues from cell wall matrix polymers, as well as from different glycoconjugates. Three different α-Af isoforms were distinguished by size exclusion chromatography of protein extracts from control tomatoes (Lycopersicon esculentum) and an ethylene synthesis-suppressed (ESS) line expressing an antisense 1-aminocyclopropane-1-carboxylic synthase transgene. α-Af I and II are active throughout fruit ontogeny. α-Af I is the first Zn-dependent cell wall enzyme isolated from tomato pericarp tissues, thus suggesting the involvement of zinc in fruit cell wall metabolism. This isoform is inhibited by 1,10-phenanthroline, but remains stable in the presence of NaCl and sucrose. α-Af II activity accounts for over 80% of the total α-Af activity in 10-d-old fruit, but activity drops during ripening. In contrast, α-Af III is ethylene dependent and specifically active during ripening. α-Af I released monosaccharide arabinose from KOH-soluble polysaccharides from tomato cell walls, whereas α-Af II and III acted on Na2CO3-soluble pectins. Different α-Af isoform responses to gibberellic acid, synthetic auxins, and ethylene were followed by using a novel ESS mature-green tomato pericarp disc system. α-Af I and II activity increased when gibberellic acid or 2,4-dichlorophenoxyacetic acid was applied, whereas ethylene treatment enhanced only α-Af III activity. Results suggest that tomato α-Afs are encoded by a gene family under differential hormonal controls, and probably have different in vivo functions. The ESS pericarp explant system allows comprehensive studies involving effects of physiological levels of different growth regulators on gene expression and enzyme activity with negligible wound-induced ethylene production. PMID:12114586

  2. Gibberellic acid, synthetic auxins, and ethylene differentially modulate alpha-L-Arabinofuranosidase activities in antisense 1-aminocyclopropane-1-carboxylic acid synthase tomato pericarp discs.

    PubMed

    Sozzi, Gabriel O; Greve, L Carl; Prody, Gerry A; Labavitch, John M

    2002-07-01

    Alpha-L-Arabinofuranosidases (alpha-Afs) are plant enzymes capable of releasing terminal arabinofuranosyl residues from cell wall matrix polymers, as well as from different glycoconjugates. Three different alpha-Af isoforms were distinguished by size exclusion chromatography of protein extracts from control tomatoes (Lycopersicon esculentum) and an ethylene synthesis-suppressed (ESS) line expressing an antisense 1-aminocyclopropane-1-carboxylic synthase transgene. alpha-Af I and II are active throughout fruit ontogeny. alpha-Af I is the first Zn-dependent cell wall enzyme isolated from tomato pericarp tissues, thus suggesting the involvement of zinc in fruit cell wall metabolism. This isoform is inhibited by 1,10-phenanthroline, but remains stable in the presence of NaCl and sucrose. alpha-Af II activity accounts for over 80% of the total alpha-Af activity in 10-d-old fruit, but activity drops during ripening. In contrast, alpha-Af III is ethylene dependent and specifically active during ripening. alpha-Af I released monosaccharide arabinose from KOH-soluble polysaccharides from tomato cell walls, whereas alpha-Af II and III acted on Na(2)CO(3)-soluble pectins. Different alpha-Af isoform responses to gibberellic acid, synthetic auxins, and ethylene were followed by using a novel ESS mature-green tomato pericarp disc system. alpha-Af I and II activity increased when gibberellic acid or 2,4-dichlorophenoxyacetic acid was applied, whereas ethylene treatment enhanced only alpha-Af III activity. Results suggest that tomato alpha-Afs are encoded by a gene family under differential hormonal controls, and probably have different in vivo functions. The ESS pericarp explant system allows comprehensive studies involving effects of physiological levels of different growth regulators on gene expression and enzyme activity with negligible wound-induced ethylene production.

  3. 1-Aminocyclopropane-1-carboxylic acid and abscisic acid during the germination of sugar beet (Beta vulgaris L.): a comparative study of fruits and seeds.

    PubMed

    Hermann, Katrin; Meinhard, Juliane; Dobrev, Peter; Linkies, Ada; Pesek, Bedrich; Hess, Barbara; Machácková, Ivana; Fischer, Uwe; Leubner-Metzger, Gerhard

    2007-01-01

    The control of sugar beet (Beta vulgaris L.) germination by plant hormones was studied by comparing fruits and seeds. Treatment of sugar beet fruits and seeds with gibberellins, brassinosteroids, auxins, cytokinins, and jasmonates or corresponding hormone biosynthesis inhibitors did not appreciably affect radicle emergence of fruits or seeds. By contrast, treatment with ethylene or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) promoted radicle emergence of fruits and seeds. Abscisic acid (ABA) acted as an antagonist of ethylene and inhibited radicle emergence of seeds, but not appreciably of fruits. High endogenous contents of ACC and of ABA were evident in seeds and pericarps of dry mature fruits, but declined early during imbibition. ABA-treatment of seeds and fruits induced seed ACC accumulation while ACC-treatment did not affect the seed ABA content. Transcripts of ACC oxidase (ACO, ethylene-forming enzyme) and ABA 8'-hydroxylase (CYP707A, ABA-degrading enzyme) accumulate in fruits and seeds upon imbibition. ABA and ACC and the pericarp did not affect the seed CYP707A transcript levels. By contrast, seed ACO transcript accumulation was promoted by ABA and by pericarp removal, but not by ACC. Quantification of the endogenous ABA and ACC contents, ABA and ACC leaching, and ethylene evolution, demonstrate that an embryo-mediated active ABA extrusion system is involved in keeping the endogenous seed ABA content low by 'active ABA leaching', while the pericarp restricts ACC leaching during imbibition. Sugar beet radicle emergence appears to be controlled by the pericarp, by ABA and ACC leaching, and by an ABA-ethylene antagonism that affects ACC biosynthesis and ACO gene expression.

  4. 1-Aminocyclopropane-1-carboxylic acid (ACC) concentration and ACC synthase expression in soybean roots, root tips, and soybean cyst nematode (Heterodera glycines)-infected roots.

    PubMed

    Tucker, Mark L; Xue, Ping; Yang, Ronghui

    2010-01-01

    Colonization of plant roots by root knot and cyst nematodes requires a functional ethylene response pathway. However, ethylene plays many roles in root development and whether its role in nematode colonization is direct or indirect, for example lateral root initiation or root hair growth, is not known. The temporal requirement for ethylene and localized synthesis of ethylene during the life span of soybean cyst nematode (SCN) on soybean roots was further investigated. Although a significant increase in ethylene evolution was not detected from SCN-colonized roots, the concentration of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), was higher in SCN-colonized root pieces and root tips than in other parts of the root. Moreover, expression analysis of 17 ACC synthase (ACS) genes indicated that a select set of ACS genes is expressed in SCN-colonized root pieces that is clearly different from the set of genes expressed in non-colonized roots or root tips. Semi-quantitative real-time PCR indicated that ACS transcript accumulation correlates with the high concentration of ACC in root tips. In addition, an ACS-like sequence was found in the public SCN nucleotide database. Acquisition of a full-length sequence for this mRNA (accession GQ389647) and alignment with transcripts for other well-characterized ACS proteins indicated that the nematode sequence is missing a key element required for ACS activity and therefore probably is not a functional ACS. Moreover, no significant amount of ACC was found in any growth stage of SCN that was tested.

  5. Synergistic enhancement of ethylene production and germination with kinetin and 1-aminocyclopropane-1-carboxylic Acid in lettuce seeds exposed to salinity stress.

    PubMed

    Khan, A A; Huang, X L

    1988-08-01

    Relief of salt (0.1 molar NaCl) stress on germination of lettuce (Lactuca sativa L., cv Mesa 659) seeds occurred with applications of 0.05 millimolar kinetin (KIN) and 1 to 10 millimolar 1-aminocyclopropane 1-carboxylic acid (ACC). Treatment with KIN enhanced the pregermination ethylene production under saline condition. A synergistic or an additive enhancement of pregermination ethylene production and germination occurred under saline condition in the presence of KIN and a saturating dose (10 millimolar) of ACC. No KIN-ACC synergism was noted in ethylene production or germination under nonsaline condition. Addition of 1 millimolar aminoethoxyvinylglycine (AVG) inhibited the KIN-enhanced pregermination ethylene production (85 to 89%) and germination (58%) under saline condition but not the synergistic effect of KIN + ACC on ethylene production. Under nonsaline condition, AVG had no effect on germination even though ethylene production was strongly inhibited. Alleviation of salt stress by KIN was inhibited in a competitive manner by 2,5-norbornadiene (NBD) (0.02-0.2 milliliter per liter), and the addition of ACC and/or ethylene reduced this inhibition. An increase in the pregermination ethylene production and germination occurred also by cotylenin E (CN) under saline condition. However, neither AVG (1 millimolar) nor NBD (0.02 to 0.2 milliliter per liter) prevented the relief of salt stress by CN. Thus, KIN may alleviate salt stress on germination by promoting both ACC production and its conversion to ethylene. Rapid utilization of ACC may be the basis for the synergistic or the additive effect of KIN plus ACC. The need for ethylene production and action for the relief of salt stress is circumvented by a treatment with CN.

  6. A Ser/Thr protein kinase phosphorylates MA-ACS1 (Musa acuminata 1-aminocyclopropane-1-carboxylic acid synthase 1) during banana fruit ripening.

    PubMed

    Choudhury, Swarup Roy; Roy, Sujit; Sengupta, Dibyendu N

    2012-08-01

    1-Aminocyclopropane-1-carboxylic acid synthase (ACS) catalyzes the rate-limiting step in ethylene biosynthesis during ripening. ACS isozymes are regulated both transcriptionally and post-translationally. However, in banana, an important climacteric fruit, little is known about post-translational regulation of ACS. Here, we report the post-translational modification of MA-ACS1 (Musa acuminata ACS1), a ripening inducible isozyme in the ACS family, which plays a key role in ethylene biosynthesis during banana fruit ripening. Immunoprecipitation analyses of phospholabeled protein extracts from banana fruit using affinity-purified anti-MA-ACS1 antibody have revealed phosphorylation of MA-ACS1, particularly in ripe fruit tissue. We have identified the induction of a 41-kDa protein kinase activity in pulp at the onset of ripening. The 41-kDa protein kinase has been identified as a putative protein kinase by MALDI-TOF/MS analysis. Biochemical analyses using partially purified protein kinase fraction from banana fruit have identified the protein kinase as a Ser/Thr family of protein kinase and its possible involvement in MA-ACS1 phosphorylation during ripening. In vitro phosphorylation analyses using synthetic peptides and site-directed mutagenized recombinant MA-ACS1 have revealed that serine 476 and 479 residues at the C-terminal region of MA-ACS1 are phosphorylated. Overall, this study provides important novel evidence for in vivo phosphorylation of MA-ACS1 at the molecular level as a possible mechanism of post-translational regulation of this key regulatory protein in ethylene signaling pathway in banana fruit during ripening. PMID:22419220

  7. Silicon-mediated changes in polyamine and 1-aminocyclopropane-1-carboxylic acid are involved in silicon-induced drought resistance in Sorghum bicolor L.

    PubMed

    Yin, Lina; Wang, Shiwen; Liu, Peng; Wang, Wenhua; Cao, Dan; Deng, Xiping; Zhang, Suiqi

    2014-07-01

    The fact that silicon application alleviates drought stress has been widely reported, but the mechanism it underlying remains unclear. Here, morphologic and physiological changes were investigated in sorghum (Sorghum bicolor L.) seedlings treated with silicon and exposed to PEG-simulated drought stress for seven days. Drought stress dramatically decreased growth parameters (biomass, root/shoot ratio, leaf area, chlorophyll concentration and photosynthetic rate), while silicon application reduced the drought-induced decreases in those parameters. Leaf relative water content and transpiration rate were maintained at high levels compared to those in seedlings without silicon. The soluble sugar contents were increased, but the proline contents and the osmotic potential were decreased, showing that osmotic adjustment did not contribute to the silicon induced-drought resistance. Furthermore, levels of both free and conjugated polyamines (PAs) levels, including putrescine, spermidine and spermine, were all found to be increased by silicon under drought stress both in leaf and root. Meanwhile, 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, was markedly decreased by supplemental silicon. Several key PA synthesis genes were upregulated by silicon under drought stress. These results suggest that silicon improves sorghum drought resistance by mediating the balance of PAs and ethylene levels. In leaf, the increased PAs and decreased ACC help to retard leaf senescence. In root, the balance between PAs and ACC participates in the modulation of root plasticity, increases the root/shoot ratio, and contributes to an increase in water uptake. These results suggest that silicon increases drought resistance through regulating several important physiological processes in plants.

  8. The Effect of Ethylene and Propylene Pulses on Respiration, Ripening Advancement, Ethylene-Forming Enzyme, and 1-Aminocyclopropane-1-carboxylic Acid Synthase Activity in Avocado Fruit.

    PubMed

    Starrett, D A; Laties, G G

    1991-03-01

    When early-season avocado fruit (Persea americana Mill. cv Hass) were treated with ethylene or propylene for 24 hours immediately on picking, the time to the onset of the respiratory climacteric, i.e. the lag period, remained unchanged compared with that in untreated fruit. When fruit were pulsed 24 hours after picking, on the other hand, the lag period was shortened. In both cases, however, a 24 hour ethylene or propylene pulse induced a transient increase in respiration, called the pulse-peak, unaccompanied by ethylene production (IL Eaks [1980] Am Soc Hortic Sci 105: 744-747). The pulse also caused a sharp rise in ethylene-forming enzyme activity in both cases, without any increase in the low level of 1-aminocyclopropane-1-carboxylic acid synthase activity. Thus, the shortening of the lag period by an ethylene pulse is not due to an effect of ethylene on either of the two key enzymes in ethylene biosynthesis. A comparison of two-dimensional polyacrylamide gel electrophoresis polypeptide profiles of in vitro translation products of poly(A(+)) mRNA from control and ethylene-pulsed fruit showed both up- and down-regulation in response to ethylene pulsing of a number of genes expressed during the ripening syndrome. It is proposed that the pulse-peak or its underlying events reflect an intrinsic element in the ripening process that in late-season or continuously ethylene-treated fruit may be subsumed in the overall climacteric response. A computerized system that allows continuous readout of multiple samples has established that the continued presentation of exogeneous ethylene or propylene to preclimacteric fruit elicits a dual respiration response comprising the merged pulse-peak and climacteric peak in series. The sequential removal of cores from a single fruit has proven an unsatisfactory sampling procedure inasmuch as coring induces wound ethylene, evokes a positive respiration response, and advances ripening.

  9. Dissecting the role of climacteric ethylene in kiwifruit (Actinidia chinensis) ripening using a 1-aminocyclopropane-1-carboxylic acid oxidase knockdown line.

    PubMed

    Atkinson, Ross G; Gunaseelan, Kularajathevan; Wang, Mindy Y; Luo, Luke; Wang, Tianchi; Norling, Cara L; Johnston, Sarah L; Maddumage, Ratnasiri; Schröder, Roswitha; Schaffer, Robert J

    2011-07-01

    During climacteric fruit ripening, autocatalytic (Type II) ethylene production initiates a transcriptional cascade that controls the production of many important fruit quality traits including flavour production and softening. The last step in ethylene biosynthesis is the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by the enzyme ACC oxidase (ACO). Ten independent kiwifruit (Actinidia chinensis) lines were generated targeting suppression of fruit ripening-related ACO genes and the fruit from one of these lines (TK2) did not produce detectable levels of climacteric ethylene. Ripening behaviour in a population of kiwifruit at harvest is asynchronous, so a short burst of exogenous ethylene was used to synchronize ripening in TK2 and control fruit. Following such a treatment, TK2 and control fruit softened to an 'eating-ripe' firmness. Control fruit produced climacteric ethylene and softened beyond eating-ripe by 5 d. In contrast, TK2 fruit maintained an eating-ripe firmness for >25 d and total volatile production was dramatically reduced. Application of continuous exogenous ethylene to the ripening-arrested TK2 fruit re-initiated fruit softening and typical ripe fruit volatiles were detected. A 17 500 gene microarray identified 401 genes that changed after ethylene treatment, including a polygalacturonase and a pectate lyase involved in cell wall breakdown, and a quinone oxidoreductase potentially involved in volatile production. Many of the gene changes were consistent with the softening and flavour changes observed after ethylene treatment. However, a surprisingly large number of genes of unknown function were also observed, which could account for the unique flavour and textural properties of ripe kiwifruit.

  10. Identification of a 1-aminocyclopropane-1-carboxylic acid synthase gene linked to the female (F) locus that enhances female sex expression in cucumber.

    PubMed Central

    Trebitsh, T; Staub, J E; O'Neill, S D

    1997-01-01

    Sex determination in cucumber (Cucumis sativus L.) is controlled largely by three genes: F, m, and a. The F and m loci interact to produce monoecious (M_f_) or gynoecious (M_f_) sex phenotypes. Ethylene and factors that induce ethylene biosynthesis, such as 1-aminocyclopropane-1-carboxylate (ACC) and auxin, also enhance female sex expression. A genomic sequence (CS-ACS1) encoding ACC synthase was amplified from genomic DNA by a polymerase chain reaction using degenerate oligonucleotide primers. Expression of CS-ACS1 is induced by auxin, but not by ACC, in wounded and intact shoot apices. Southern blo hybridization analysis of near-isogenic gynoecious (MMFF) and monoecious (MMff) lines derived from divers genetic backgrounds revealed the existence of an additional ACC synthase (CS-ACS1G) genomic sequence in the gynoecious lines. Sex phenotype analysis of a segregating F2 population detected a 100% correlation between the CS-ACS1G marker and the presence of the F locus. The CS-ACS1G gene is located in linkage group B coincident with the F locus, and in the population tested there was no recombination between the CS-ACS1G gene and the F locus. Collectively, these data suggest that CS-ACS1G is closely linked to the F locus and may play a pivotal role in the determination of sex in cucumber flowers. PMID:9085580

  11. Expression and regulation of pear 1-aminocyclopropane-1-carboxylic acid synthase gene (PpACS1a) during fruit ripening, under salicylic acid and indole-3-acetic acid treatment, and in diseased fruit.

    PubMed

    Shi, Hai-Yan; Zhang, Yu-Xing

    2014-06-01

    In plants, the level of ethylene is determined by the activity of the key enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS). A gene encoding an ACC synthase protein was isolated from pear (Pyrus pyrifolia). This gene designated PpACS1a (GenBank accession no. KC632526) was 1488 bp in length with an open reading frame (ORF) encoding a protein of 495 amino acids that shared high similarity with other pear ACC synthase proteins. The PpACS1a was grouped into type-1 subfamily of plant ACS based on its conserved domain and phylogenetic status. Real-time quantitative PCR indicated that PpACS1a was differentially expressed in pear tissues and predominantly expressed in anthers. The expression signal of PpACS1a was also detected in fruit and leaves, but no signal was detected in shoots and petals. Furthermore, the PpACS1a expression was regulated during fruit ripening. In addition, the PpACS1a gene expression was regulated by salicylic acid (SA) and indole-3-acetic acid (IAA) in fruit. Moreover, the expression of the PpACS1a was up-regulated in diseased pear fruit. These results indicated that PpACS1a might be involved in fruit ripening and response to SA, IAA and disease.

  12. The female-specific Cs-ACS1G gene of cucumber. A case of gene duplication and recombination between the non-sex-specific 1-aminocyclopropane-1-carboxylate synthase gene and a branched-chain amino acid transaminase gene.

    PubMed

    Knopf, Ronit Rimon; Trebitsh, Tova

    2006-09-01

    Cucumber (Cucumis sativus L.) is a monoecious plant in which female sex expression (gynoecy) is controlled by the Female (F) locus that can be modified by other sex-determining genes as well as by environmental and hormonal factors. As in many other cucurbits, ethylene is the major plant hormone regulating female sex expression. Previously we isolated the Cs-ACS1 (ACS, 1-aminocyclopropane-1-carboxylate synthase) gene that encodes the rate-limiting enzyme in the ethylene biosynthetic pathway. We proposed that Cs-ACS1 is present in a single copy in monoecious (ffMM) plants whereas gynoecious plants (FFMM) contain an additional copy Cs-ACS1G that was mapped to the F locus. To study the origin of Cs-ACS1G, we cloned and analyzed both the gynoecious-specific Cs-ACS1G gene and the non-sex-specific Cs-ACS1 gene. Our results indicate that Cs-ACS1G is the result of a relatively recent gene duplication and recombination, between Cs-ACS1 and a branched-chain amino acid transaminase (BCAT) gene. Taking into consideration that the Cs-ACS1G gene was mapped to the F locus, we propose that this duplication event gave rise to the F locus and to gynoecious cucumber plants. Computer analysis of the 1 kb region upstream of the transcription initiation site revealed several putative cis-acting regulatory elements that can potentially confer the responsiveness of Cs-ACS1G to developmental and hormonal factors and thereby control female sex determination in cucumber. These findings lead us to a model explaining the action of Cs-ACS1 and Cs-ACS1G in cucumber floral sex determination. PMID:16887844

  13. Differential expression of two genes for 1-aminocyclopropane-1-carboxylate synthase in tomato fruits

    SciTech Connect

    Olson, D.C.; White, J.A.; Edelman, L.; Kende, H. ); Harkins, R.N. )

    1991-06-15

    1-Aminocyclopropane-1-carboxylate synthase is the regulated enzyme in the biosynthetic pathway of the plant hormone ethylene. A full-length cDNA encoding this enzyme has been cloned from tomato fruits. The authors report here the complete nucleotide and derived amino acid sequences of a cDNA encoding a second isoform of ACC synthase from tomato fruits. The cDNAs coding for both isoforms contain highly conserved regions that are surrounded by regions of low homology, especially at the 5{prime} and 3{prime} ends. Gene-specific probes were constructed to examine the expression of transcripts encoding the two ACC synthase isoforms under two conditions of enhanced ethylene formation--namely, during fruit ripening and in response to mechanical stress (wounding). The level of mRNA encoding both isoforms, ACC synthase 1 and 2, increased during ripening. In contrast, wounding caused an increase in only the level of mRNA coding for ACC synthase 1. Blot analysis of genomic DNA digested with restriction enzymes confirmed that ACC synthase 1 and 2 are encoded by different genes.

  14. Isolation and characterization of a potato cDNA corresponding to a 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene differentially activated by stress.

    PubMed

    Zanetti, María Eugenia; Terrile, María Cecilia; Arce, Débora; Godoy, Andrea Verónica; Segundo, Blanca San; Casalongué, Claudia

    2002-12-01

    1-Aminocyclopropane-1-carboxylate (ACC) oxidase enzyme catalyses the final step in ethylene biosynthesis, converting 1-aminocyclopropane-1-carboxylic acid to ethylene. A cDNA clone encoding an ACC oxidase, ST-ACO3, was isolated from potato (Solanum tuberosum L.) by differential screening of a Fusarium eumartii infected-tuber cDNA library. The deduced amino acid sequence exhibited similarity to other ACC oxidase proteins from several plants species. Northern blot analysis revealed that the ST-ACO3 mRNA level increased in potato tubers upon inoculation with F. eumartii, as well as after treatment with salicylic acid and indole-3-acetic acid, suggesting a cross-talk between different signalling pathways involved in the defence response of potato tubers against F. eumartii attack.

  15. Characterization and sequencing of the active site of 1-aminocyclopropane-1-carboxylate synthase

    SciTech Connect

    Yip, Wing-Kin; Dong, Jian-Guo; Yang, S.F. ); Kenny, J.W.; Thompson, G.A. )

    1990-10-01

    The pyridoxal phosphate (PLP)-dependent 1-aminocyclopropane-1-carboxylic acid (ACC) synthase the key enzyme in ethylene biosynthesis, is inactivated by its substrate S-adenosylmethionine (AdoMet). Apple ACC synthase was purified with an immunoaffinity gel, and its active site was probed with NaB{sup 3}H{sub 4} or Ado({sup 14}C)Met. Peptide sequencing of both {sup 3}H- and {sup 14}C-labeled peptides revealed a common dodecapeptide of Ser-Leu-Ser-Xaa-Asp-Leu-Gly-Leu-Pro-Gly-Phe-Arg, where Xaa was the modified, radioactive residue in each case. Acid hydrolysis of the {sup 3}H-labeled enzyme released radioactive N-pyridoxyllysine, indicating that the active-site peptide contained lysine at position 4. Mass spectrometry of the {sup 14}C-labeled peptide indicated a protonated molecular ion at m/z 1390.6, from which the mass of Xaa was calculated to be 229, a number that is equivalent to the mass of a lysine residue alkylated by the 2-aminobutyrate portion of AdoMet, as we previously proposed. These results indicate that the same active-site lysine binds the PLP and convalently links to the 2-aminobutyrate portion of AdoMet during inactivation. The active site of tomato ACC synthase was probed in the same manner with Ado ({sup 14}C)Met. Sequencing of the tomato active-site peptide revealed two highly conserved dodecapeptides; the minor peptide possessed a sequence identical to that of the apple enzyme, whereas the major peptide differed from the minor peptide in that methionine replaced leucine at position 6.

  16. Glutathione Regulates 1-Aminocyclopropane-1-Carboxylate Synthase Transcription via WRKY33 and 1-Aminocyclopropane-1-Carboxylate Oxidase by Modulating Messenger RNA Stability to Induce Ethylene Synthesis during Stress.

    PubMed

    Datta, Riddhi; Kumar, Deepak; Sultana, Asma; Hazra, Saptarshi; Bhattacharyya, Dipto; Chattopadhyay, Sharmila

    2015-12-01

    Glutathione (GSH) plays a fundamental role in plant defense-signaling network. Recently, we have established the involvement of GSH with ethylene (ET) to combat environmental stress. However, the mechanism of GSH-ET interplay still remains unexplored. Here, we demonstrate that GSH induces ET biosynthesis by modulating the transcriptional and posttranscriptional regulations of its key enzymes, 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). Transgenic Arabidopsis (Arabidopsis thaliana) plants with enhanced GSH content (AtECS) exhibited remarkable up-regulation of ACS2, ACS6, and ACO1 at transcript as well as protein levels, while they were down-regulated in the GSH-depleted phytoalexin deficient2-1 (pad2-1) mutant. We further observed that GSH induced ACS2 and ACS6 transcription in a WRKY33-dependent manner, while ACO1 transcription remained unaffected. On the other hand, the messenger RNA stability for ACO1 was found to be increased by GSH, which explains our above observations. In addition, we also identified the ACO1 protein to be a subject for S-glutathionylation, which is consistent with our in silico data. However, S-glutathionylation of ACS2 and ACS6 proteins was not detected. Further, the AtECS plants exhibited resistance to necrotrophic infection and salt stress, while the pad2-1 mutant was sensitive. Exogenously applied GSH could improve stress tolerance in wild-type plants but not in the ET-signaling mutant ethylene insensitive2-1, indicating that GSH-mediated resistance to these stresses occurs via an ET-mediated pathway. Together, our investigation reveals a dual-level regulation of ET biosynthesis by GSH during stress.

  17. Molecular characterization and expression analysis of 1-aminocyclopropane-1-carboxylate oxidase homologs from potato under abiotic and biotic stresses.

    PubMed

    Nie, Xianzhou; Singh, Rudra P; Tai, George C C

    2002-10-01

    In this work, we report cloning of two full-length 1-aminocyclopropane-1-carboxylate oxidase (ACO) cDNAs (ACO1 and ACO2) from potato (Solanum tuberosum) and their expression in potato tissues. The sequence data indicate that the two cDNAs share a high degree of homology with each other, and with known ACO genes from other plant species, including monocots and dicots. However, these potato genes lack homology at the 5' and 3' ends, despite similarities in their open reading frames and encoded amino acids. Phylogenetic analysis places them in two subfamilies of ACOs. The genes are tissue specific: expression is high in leaves and low in roots and tubers. In sprouts and tubers, ACO1 is induced by heat (40 degrees C) and cold (0 degrees C) stresses, whereas ACO2 is induced only by cold (0 degrees C). ACO1 is markedly induced in leaves by wounding, soil-flooding, and exogenous application of 1-aminocyclopropane-1-carboxylic acid (ACC). In contrast, ACO2 induction is lower under these treatments. ACO1 and ACO2 are regulated very differently in potato leaves with respect to senescence. ACO2 expression is unaffected by senescence, whereas that of ACO1 is closely related to the age and senescence in both attached and detached leaves. Exogenous ACC not only induces ACO1, but also accelerates leaf senescence. ACO1 transcripts are induced significantly in leaves, stems, and tubers in the Potato virus A (PVA)-resistant potato cultivar Shepody when graft inoculated with PVA. PMID:12416623

  18. Molecular cloning and expression analysis of an 1-aminocyclopropane-1-carboxylate synthase gene from Oncidium Gower Ramsey.

    PubMed

    Shi, Le-Song; Liu, Jin-Ping

    2016-01-01

    1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) is a rate-limiting enzyme in the biosynthesis of ethylene which regulates many aspects of the plant development and responses to biotic and abiotic stresses. In this study, a full-length cDNA of ACC synthase, OnACS2, was cloned from the senescing flower of Oncidium Gower Ramsey by RACE. The full-length cDNA of OnACS2 (GenBank accession no. JQ822087) was 1557 bp in length with an open reading frame (ORF) of 1308 bp encoding for a protein of 435 amino acid residues. The predicted OnACS2 protein had a molecular mass of 49.1 kDa with pI value of 7.51. Phylogenetic analysis indicated its evolutionary relationships with corresponding orthologous sequences in orchids, Hosta ventricosa and monocots. Real-time PCR assay demonstrated that OnACS2 was constitutively expressed in all tested organs with the highest transcript level in the gynandria. Differential expression pattern of OnACS2 gene correlated to the ethylene production and the subsequent occurrence of senescent symptoms in flower suggested that OnACS2 probably played an important role in the initiation of flower senescence. PMID:26631967

  19. Increased 1-aminocyclopropane-1-carboxylate deaminase activity enhances Agrobacterium tumefaciens-mediated gene delivery into plant cells

    PubMed Central

    Someya, Tatsuhiko; Nonaka, Satoko; Nakamura, Kouji; Ezura, Hiroshi

    2013-01-01

    Agrobacterium-mediated transformation is a useful tool for the genetic modification in plants, although its efficiency is low for several plant species. Agrobacterium-mediated transformation has three major steps in laboratory-controlled experiments: the delivery of T-DNA into plant cells, the selection of transformed plant cells, and the regeneration of whole plants from the selected cells. Each of these steps must be optimized to improve the efficiency of Agrobacterium-mediated plant transformation. It has been reported that increasing the number of cells transformed by T-DNA delivery can improve the frequency of stable transformation. Previously, we demonstrated that a reduction in ethylene production by plant cells during cocultivation with A. tumefaciens-expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase resulted in increased T-DNA delivery into the plant cells. In this study, to further improve T-DNA delivery by A. tumefaciens, we modified the expression cassette of the ACC deaminase gene using vir gene promoter sequences. The ACC deaminase gene driven by the virD1 promoter was expressed at a higher level, resulting in a higher ACC deaminase activity in this A. tumefaciens strain than in the strain with the lac promoter used in a previous study. The newly developed A. tumefaciens strain improves the delivery of T-DNA into Solanum lycopersicum (tomato) and Erianthus ravennae plants and thus may be a powerful tool for the Agrobacterium-mediated genetic engineering of plants. PMID:24000136

  20. An insight into the sequential, structural and phylogenetic properties of banana 1-aminocyclopropane-1-carboxylate synthase 1 and study of its interaction with pyridoxal-5'-phosphate and aminoethoxyvinylglycine.

    PubMed

    Choudhury, Swarup Roy; Singh, Sanjay Kumar; Roy, Sujit; Sengupta, Dibyendu N

    2010-06-01

    In banana, ethylene production for ripening is accompanied by a dramatic increase in 1-aminocyclopropane-1-carboxylate (ACC) content, transcript level of Musa acuminata ACC synthase 1 (MA-ACS1) and the enzymatic activity of ACC synthase 1 at the onset of the climacteric period. MA-ACS1 catalyses the conversion of S-adenosyl-L-methionine (SAM) to ACC, the key regulatory step in ethylene biosynthesis. Multiple sequence alignments of 1-aminocyclopropane-1-carboxylate synthase (ACS) amino acid sequences based on database searches have indicated that MA-ACS1 is a highly conserved protein across the plant kingdom. This report describes an in silico analysis to provide the first important insightful information about the sequential, structural and phylogenetic characteristics of MA-ACS1. The three-dimensional structure of MA-ACS1, constructed based on homology modelling, in combination with the available data enabled a comparative mechanistic analysis of MA-ACS1 to explain the catalytic roles of the conserved and non-conserved active site residues. We have further demonstrated that, as in apple and tomato, banana- ACS1 (MA-ACS1) forms a homodimer and a complex with cofactor pyridoxal-5'-phosphate (PLP) and inhibitor aminoethoxyvinylglycine (AVG). We have also predicted that the residues from the PLP-binding pocket, essential for ligand binding, are mostly conserved across the MA-ACS1 structure and the competitive inhibitor AVG binds at a location adjacent to PLP. PMID:20689184

  1. An insight into the sequential, structural and phylogenetic properties of banana 1-aminocyclopropane-1-carboxylate synthase 1 and study of its interaction with pyridoxal-5'-phosphate and aminoethoxyvinylglycine.

    PubMed

    Choudhury, Swarup Roy; Singh, Sanjay Kumar; Roy, Sujit; Sengupta, Dibyendu N

    2010-06-01

    In banana, ethylene production for ripening is accompanied by a dramatic increase in 1-aminocyclopropane-1-carboxylate (ACC) content, transcript level of Musa acuminata ACC synthase 1 (MA-ACS1) and the enzymatic activity of ACC synthase 1 at the onset of the climacteric period. MA-ACS1 catalyses the conversion of S-adenosyl-L-methionine (SAM) to ACC, the key regulatory step in ethylene biosynthesis. Multiple sequence alignments of 1-aminocyclopropane-1-carboxylate synthase (ACS) amino acid sequences based on database searches have indicated that MA-ACS1 is a highly conserved protein across the plant kingdom. This report describes an in silico analysis to provide the first important insightful information about the sequential, structural and phylogenetic characteristics of MA-ACS1. The three-dimensional structure of MA-ACS1, constructed based on homology modelling, in combination with the available data enabled a comparative mechanistic analysis of MA-ACS1 to explain the catalytic roles of the conserved and non-conserved active site residues. We have further demonstrated that, as in apple and tomato, banana- ACS1 (MA-ACS1) forms a homodimer and a complex with cofactor pyridoxal-5'-phosphate (PLP) and inhibitor aminoethoxyvinylglycine (AVG). We have also predicted that the residues from the PLP-binding pocket, essential for ligand binding, are mostly conserved across the MA-ACS1 structure and the competitive inhibitor AVG binds at a location adjacent to PLP.

  2. 1-Aminocyclopropane-1-Carboxylate Oxidase Activity Limits Ethylene Biosynthesis in Rumex palustris during Submergence

    PubMed Central

    Vriezen, Wim H.; Hulzink, Raymond; Mariani, Celestina; Voesenek, Laurentius A.C.J.

    1999-01-01

    Submergence strongly stimulates petiole elongation in Rumex palustris, and ethylene accumulation initiates and maintains this response in submerged tissues. cDNAs from R. palustris corresponding to a 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene (RP-ACO1) were isolated from elongating petioles and used to study the expression of the corresponding gene. An increase in RP-ACO1 messenger was observed in the petioles and lamina of elongating leaves 2 h after the start of submergence. ACC oxidase enzyme activity was measured in homogenates of R. palustris shoots, and a relevant increase was observed within 12 h under water with a maximum after 24 h. We have shown previously that the ethylene production rate of submerged shoots does not increase significantly during the first 24 h of submergence (L.A.C.J. Voesenek, M. Banga, R.H. Thier, C.M. Mudde, F.M. Harren, G.W.M. Barendse, C.W.P.M. Blom [1993] Plant Physiol 103: 783–791), suggesting that under these conditions ACC oxidase activity is inhibited in vivo. We found evidence that this inhibition is caused by a reduction of oxygen levels. We hypothesize that an increased ACC oxidase enzyme concentration counterbalances the reduced enzyme activity caused by low oxygen concentration during submergence, thus sustaining ethylene production under these conditions. Therefore, ethylene biosynthesis seems to be limited at the level of ACC oxidase activity rather than by ACC synthase in R. palustris during submergence. PMID:10482674

  3. Mechanistic studies of 1-aminocyclopropane-1-carboxylate deaminase: characterization of an unusual pyridoxal 5'-phosphate-dependent reaction.

    PubMed

    Thibodeaux, Christopher J; Liu, Hung-Wen

    2011-03-22

    1-Aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that cleaves the cyclopropane ring of ACC, to give α-ketobutyric acid and ammonia as products. The cleavage of the C(α)-C(β) bond of an amino acid substrate is a rare event in PLP-dependent enzyme catalysis. Potential chemical mechanisms involving nucleophile- or acid-catalyzed cyclopropane ring opening have been proposed for the unusual transformation catalyzed by ACCD, but the actual mode of cyclopropane ring cleavage remains obscure. In this report, we aim to elucidate the mechanistic features of ACCD catalysis by investigating the kinetic properties of ACCD from Pseudomonas sp. ACP and several of its mutant enzymes. Our studies suggest that the pK(a) of the conserved active site residue, Tyr294, is lowered by a hydrogen bonding interaction with a second conserved residue, Tyr268. This allows Tyr294 to deprotonate the incoming amino group of ACC to initiate the aldimine exchange reaction between ACC and the PLP coenzyme and also likely helps to activate Tyr294 for a role as a nucleophile to attack and cleave the cyclopropane ring of the substrate. In addition, solvent kinetic isotope effect (KIE), proton inventory, and (13)C KIE studies of the wild type enzyme suggest that the C(α)-C(β) bond cleavage step in the chemical mechanism is at least partially rate-limiting under k(cat)/K(m) conditions and is likely preceded in the mechanism by a partially rate-limiting step involving the conversion of a stable gem-diamine intermediate into a reactive external aldimine intermediate that is poised for cyclopropane ring cleavage. When viewed within the context of previous mechanistic and structural studies of ACCD enzymes, our studies are most consistent with a mode of cyclopropane ring cleavage involving nucleophilic catalysis by Tyr294.

  4. New Insights into 1-Aminocyclopropane-1-Carboxylate (ACC) Deaminase Phylogeny, Evolution and Ecological Significance

    PubMed Central

    Nascimento, Francisco X.; Rossi, Márcio J.; Soares, Cláudio R. F. S.; McConkey, Brendan J.; Glick, Bernard R.

    2014-01-01

    The main objective of this work is the study of the phylogeny, evolution and ecological importance of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, the activity of which represents one of the most important and studied mechanisms used by plant growth–promoting microorganisms. The ACC deaminase gene and its regulatory elements presence in completely sequenced organisms was verified by multiple searches in diverse databases, and based on the data obtained a comprehensive analysis was conducted. Strain habitat, origin and ACC deaminase activity were taken into account when analyzing the results. In order to unveil ACC deaminase origin, evolution and relationships with other closely related pyridoxal phosphate (PLP) dependent enzymes a phylogenetic analysis was also performed. The data obtained show that ACC deaminase is mostly prevalent in some Bacteria, Fungi and members of Stramenopiles. Contrary to previous reports, we show that ACC deaminase genes are predominantly vertically inherited in various bacterial and fungal classes. Still, results suggest a considerable degree of horizontal gene transfer events, including interkingdom transfer events. A model for ACC deaminase origin and evolution is also proposed. This study also confirms the previous reports suggesting that the Lrp-like regulatory protein AcdR is a common mechanism regulating ACC deaminase expression in Proteobacteria, however, we also show that other regulatory mechanisms may be present in some Proteobacteria and other bacterial phyla. In this study we provide a more complete view of the role for ACC deaminase than was previously available. The results show that ACC deaminase may not only be related to plant growth promotion abilities, but may also play multiple roles in microorganism's developmental processes. Hence, exploring the origin and functioning of this enzyme may be the key in a variety of important agricultural and biotechnological applications. PMID:24905353

  5. Glutathione Regulates 1-Aminocyclopropane-1-Carboxylate Synthase Transcription via WRKY33 and 1-Aminocyclopropane-1-Carboxylate Oxidase by Modulating Messenger RNA Stability to Induce Ethylene Synthesis during Stress1[OPEN

    PubMed Central

    Kumar, Deepak; Hazra, Saptarshi; Chattopadhyay, Sharmila

    2015-01-01

    Glutathione (GSH) plays a fundamental role in plant defense-signaling network. Recently, we have established the involvement of GSH with ethylene (ET) to combat environmental stress. However, the mechanism of GSH-ET interplay still remains unexplored. Here, we demonstrate that GSH induces ET biosynthesis by modulating the transcriptional and posttranscriptional regulations of its key enzymes, 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). Transgenic Arabidopsis (Arabidopsis thaliana) plants with enhanced GSH content (AtECS) exhibited remarkable up-regulation of ACS2, ACS6, and ACO1 at transcript as well as protein levels, while they were down-regulated in the GSH-depleted phytoalexin deficient2-1 (pad2-1) mutant. We further observed that GSH induced ACS2 and ACS6 transcription in a WRKY33-dependent manner, while ACO1 transcription remained unaffected. On the other hand, the messenger RNA stability for ACO1 was found to be increased by GSH, which explains our above observations. In addition, we also identified the ACO1 protein to be a subject for S-glutathionylation, which is consistent with our in silico data. However, S-glutathionylation of ACS2 and ACS6 proteins was not detected. Further, the AtECS plants exhibited resistance to necrotrophic infection and salt stress, while the pad2-1 mutant was sensitive. Exogenously applied GSH could improve stress tolerance in wild-type plants but not in the ET-signaling mutant ethylene insensitive2-1, indicating that GSH-mediated resistance to these stresses occurs via an ET-mediated pathway. Together, our investigation reveals a dual-level regulation of ET biosynthesis by GSH during stress. PMID:26463088

  6. Recent developments in use of 1-aminocyclopropane-1-carboxylate (ACC) deaminase for conferring tolerance to biotic and abiotic stress.

    PubMed

    Gontia-Mishra, Iti; Sasidharan, Shaly; Tiwari, Sharad

    2014-05-01

    Ethylene is an essential plant hormone also known as a stress hormone because its synthesis is accelerated by induction of a variety of biotic and abiotic stress. The plant growth promoting bacteria containing the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase enhances plant growth by decreasing plant ethylene levels under stress conditions. The expression of ACC deaminase (acdS) gene in transgenic plants is an alternative approach to overcome the ethylene-induced stress. Several transgenic plants have been engineered to express both bacterial/plant acdS genes which then lowers the stress-induced ethylene levels, thus efficiently combating the deleterious effects of environmental stresses. This review summarizes the current knowledge of various transgenic plants overexpressing microbial and plant acdS genes and their potential under diverse biotic and abiotic stresses. Transcription regulation mechanism of acdS gene from different bacteria, with special emphasis to nitrogen fixing bacteria is also discussed in this review.

  7. Mutation in the gene encoding 1-aminocyclopropane-1-carboxylate synthase 4 (CitACS4) led to andromonoecy in watermelon.

    PubMed

    Ji, Gaojie; Zhang, Jie; Zhang, Haiying; Sun, Honghe; Gong, Guoyi; Shi, Jianting; Tian, Shouwei; Guo, Shaogui; Ren, Yi; Shen, Huolin; Gao, Junping; Xu, Yong

    2016-09-01

    Although it has been reported previously that ethylene plays a critical role in sex determination in cucurbit species, how the andromonoecy that carries both the male and hermaphroditic flowers is determined in watermelon is still unknown. Here we showed that the watermelon gene 1-aminocyclopropane-1-carboxylate synthase 4 (CitACS4), expressed specifically in carpel primordia, determines the andromonoecy in watermelon. Among four single nucleotide polymorphism (SNPs) and one InDel identified in the coding region of CitACS4, the C364W mutation located in the conserved box 6 was co-segregated with andromonoecy. Enzymatic analyses showed that the C364W mutation caused a reduced activity in CitACS4. We believe that the reduced CitACS4 activity may hamper the programmed cell death in stamen primordia, leading to the formation of hermaphroditic flowers. PMID:26839981

  8. Characterization of plant growth promoting rhizobacteria isolated from polluted soils and containing 1-aminocyclopropane-1-carboxylate deaminase.

    PubMed

    Belimov, A A; Safronova, V I; Sergeyeva, T A; Egorova, T N; Matveyeva, V A; Tsyganov, V E; Borisov, A Y; Tikhonovich, I A; Kluge, C; Preisfeld, A; Dietz, K J; Stepanok, V V

    2001-07-01

    Fifteen bacterial strains containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase were isolated from the rhizoplane of pea (Pisum sativum L.) and Indian mustard (Brassica juncea L.) grown in different soils and a long-standing sewage sludge contaminated with heavy metals. The isolated strains were characterized and assigned to various genera and species, such as Pseudomonas brassicacearum, Pseudomonas marginalis, Pseudomonas oryzihabitans, Pseudomonas putida, Pseudomonas sp., Alcaligenes xylosoxidans, Alcaligenes sp., Variovorax paradoxus, Bacillus pumilus, and Rhodococcus sp. by determination of 16S rRNA gene sequences. The root elongation of Indian mustard and rape (Brassica napus var. oleifera L.) germinating seedlings was stimulated by inoculation with 8 and 13 isolated strains, respectively. The bacteria were tolerant to cadmium toxicity and stimulated root elongation of rape seedlings in the presence of 300 microM CdCl2 in the nutrient solution. The effect of ACC-utilising bacteria on root elongation correlated with the impact of aminoethoxyvinylglycine and silver ions, chemical inhibitors of ethylene biosynthesis. A significant improvement in the growth of rape caused by inoculation with certain selected strains was also observed in pot experiments, when the plants were cultivated in cadmium-supplemented soil. The biomass of pea cv. Sparkle and its ethylene sensitive mutant E2 (sym5), in particular, was increased through inoculation with certain strains of ACC-utilising bacteria in pot experiments in quartz sand culture. The beneficial effect of the bacteria on plant growth varied significantly depending on individual bacterial strains, plant genotype, and growth conditions. The results suggest that plant growth promoting rhizobacteria containing ACC deaminase are present in various soils and offer promise as a bacterial inoculum for improvement of plant growth, particularly under unfavourable environmental conditions.

  9. Characterization of plant growth promoting rhizobacteria isolated from polluted soils and containing 1-aminocyclopropane-1-carboxylate deaminase.

    PubMed

    Belimov, A A; Safronova, V I; Sergeyeva, T A; Egorova, T N; Matveyeva, V A; Tsyganov, V E; Borisov, A Y; Tikhonovich, I A; Kluge, C; Preisfeld, A; Dietz, K J; Stepanok, V V

    2001-07-01

    Fifteen bacterial strains containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase were isolated from the rhizoplane of pea (Pisum sativum L.) and Indian mustard (Brassica juncea L.) grown in different soils and a long-standing sewage sludge contaminated with heavy metals. The isolated strains were characterized and assigned to various genera and species, such as Pseudomonas brassicacearum, Pseudomonas marginalis, Pseudomonas oryzihabitans, Pseudomonas putida, Pseudomonas sp., Alcaligenes xylosoxidans, Alcaligenes sp., Variovorax paradoxus, Bacillus pumilus, and Rhodococcus sp. by determination of 16S rRNA gene sequences. The root elongation of Indian mustard and rape (Brassica napus var. oleifera L.) germinating seedlings was stimulated by inoculation with 8 and 13 isolated strains, respectively. The bacteria were tolerant to cadmium toxicity and stimulated root elongation of rape seedlings in the presence of 300 microM CdCl2 in the nutrient solution. The effect of ACC-utilising bacteria on root elongation correlated with the impact of aminoethoxyvinylglycine and silver ions, chemical inhibitors of ethylene biosynthesis. A significant improvement in the growth of rape caused by inoculation with certain selected strains was also observed in pot experiments, when the plants were cultivated in cadmium-supplemented soil. The biomass of pea cv. Sparkle and its ethylene sensitive mutant E2 (sym5), in particular, was increased through inoculation with certain strains of ACC-utilising bacteria in pot experiments in quartz sand culture. The beneficial effect of the bacteria on plant growth varied significantly depending on individual bacterial strains, plant genotype, and growth conditions. The results suggest that plant growth promoting rhizobacteria containing ACC deaminase are present in various soils and offer promise as a bacterial inoculum for improvement of plant growth, particularly under unfavourable environmental conditions. PMID:11547884

  10. An auxin-responsive 1-aminocyclopropane-1-carboxylate synthase is responsible for differential ethylene production in gravistimulated Antirrhinum majus L. flower stems.

    PubMed

    Woltering, Ernst J; Balk, Peter A; Nijenhuis-Devries, Mariska A; Faivre, Marilyne; Ruys, Gerda; Somhorst, Dianne; Philosoph-Hadas, Sonia; Friedman, Haya

    2005-01-01

    The regulation of gravistimulation-induced ethylene production and its role in gravitropic bending was studied in Antirrhinum majus L. cut flower stems. Gravistimulation increased ethylene production in both lower and upper halves of the stems with much higher levels observed in the lower half. Expression patterns of three different 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) genes, an ACC oxidase (ACO) and an ethylene receptor (ETR/ERS homolog) gene were studied in the bending zone of gravistimulated stems and in excised stem sections following treatment with different chemicals. One of the ACS genes (Am-ACS3) was abundantly expressed in the bending zone cortex at the lower side of the stems within 2 h of gravistimulation. Am-ACS3 was not expressed in vertical stems or in other parts of (gravistimulated) stems, leaves or flowers. Am-ACS3 was strongly induced by indole-3-acetic acid (IAA) but not responsive to ethylene. The Am-ACS3 expression pattern strongly suggests that Am-ACS3 is responsible for the observed differential ethylene production in gravistimulated stems; its responsiveness to IAA suggests that Am-ACS3 expression reflects changes in auxin signalling. Am-ACS1 also showed increased expression in gravistimulated and IAA-treated stems although to a much lesser extent than Am-ACS3. In contrast to Am-ACS3, Am-ACS1 was also expressed in non-bending regions of vertical and gravistimulated stems and in leaves, and Am-ACS1 expression was not confined to the lower side cortex but evenly distributed over the diameter of the stem. Am-ACO and Am-ETR/ERS expression was increased in both the lower and upper halves of gravistimulated stems. Expression of both Am-ACO and Am-ETR/ERS was responsive to ethylene, suggesting regulation by IAA-dependent differential ethylene production. Am-ACO expression and in vivo ACO activity, in addition, were induced by IAA, independent of the IAA-induced ethylene. IAA-induced growth of vertical stem sections and bending of

  11. Effect of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid on different growth stages of Haematococcus pluvialis.

    PubMed

    Vo, Thi-Thao; Lee, Changsu; Han, Sang-Il; Kim, Jee Young; Kim, Sok; Choi, Yoon-E

    2016-11-01

    In this study, we explored the effects of ACC on other stages of H. pluvialis. Interestingly, even though ACC displayed a dose-dependent effect on astaxanthin production, it is evident that astaxanthin production could be facilitated whenever the cells were treated at the early red stage. The transcriptional levels of BKT, CHY, SOD, and CAT genes supported enhanced astaxanthin biosynthesis upon ACC treatment at the early red stage. The combinatorial synergistic effect of ACC and light intensity was also confirmed. Finally, two-step application of ACC at the vegetative phase to increase biomass production and at the early-red stage to promote astaxanthin biosynthesis was proposed to maximize the efficiency of ACC treatment. PMID:27566516

  12. Inhibition by 1-aminocyclobutane-1-carboxylate of the activity of 1-aminocyclopropane-1-carboxylate oxidase obtained from senescing petals of carnation (Dianthus caryophyllus L.) flowers.

    PubMed

    Kosugi, Y; Oyamada, N; Satoh, S; Yoshioka, T; Onodera, E; Yamada, Y

    1997-03-01

    We partially purified 1-aminocyclopropane-1-carboxylate (ACC) oxidase from senescing petals of carnation (Dianthus caryophyllus L. cv. Nora) flowers and investigated its general characteristics, and, in particular, the inhibition of its activity by ACC analogs. The enzyme had an optimum pH at 7-7.5 and required Fe2+, ascorbate and NaHCO3 for its maximal activity. The Km for ACC was calculated as 111-125 microM in the presence of NaHCO3. Its M(r) was estimated to be 35 and 36 kDa by gel-filtration chromatography on HPLC and SDS-PAGE, respectively, indicating that the enzyme exists in a monomeric form. These properties were in agreement with those reported previously with ACC oxidases from different plant tissues including senescing carnation petals. Among six ACC analogs tested, 1-aminocyclobutane-1-carboxylate (ACBC) inhibited most severely the activity of ACC oxidase from carnation petals. ACBC acted as a competitive inhibitor with the Ki of 20-30 microM. The comparison between the Km for ACC and the Ki for ACBC indicated that ACBC had an affinity which was ca. 5-fold higher than that of ACC. Whereas ACC inactivated carnation ACC oxidase in a time-dependent manner during incubation, ACBC did not cause the inactivation of the enzyme. Preliminary experiments showed that ACBC and its N-substituted derivatives delayed the onset of senescence in cut carnation flowers.

  13. Expression of an exogenous 1-aminocyclopropane-1-carboxylate deaminase gene in Mesorhizobium spp. reduces the negative effects of salt stress in chickpea.

    PubMed

    Brígido, Clarisse; Nascimento, Francisco X; Duan, Jin; Glick, Bernard R; Oliveira, Solange

    2013-12-01

    Our goal was to study the symbiotic performance of two Mesorhizobium ciceri strains, transformed with an exogenous 1-aminocyclopropane-1-carboxylate deaminase gene (acdS), in chickpea plants under salinity stress. The EE-7 (salt-sensitive) and G-55 (salt-tolerant) M. ciceri strains were transformed with an acdS gene present on plasmid pRKACC. Salinity significantly reduced the overall growth of plants inoculated with either wild-type strains. Although the growth of plants inoculated with either salt-sensitive or salt-tolerant strain was reduced under salinity, the salt-tolerant strain showed a higher ability to nodulate chickpea under salt stress compared with the salt-sensitive strain. The shoot dry weight was significantly higher in plants inoculated with the acdS-transformed salt-sensitive strain compared with the plants inoculated with the native strain in the presence of salt. The negative effects of salt stress were also reduced in nodulation when using acdS-transformed strains in comparison with the wild-type strains. Interestingly, by expressing the exogenous acdS gene, the salt-sensitive strain was able to induce nodules in the same extent as the salt-tolerant strain. Although preliminary, these results suggest that genetic modification of a Mesorhizobium strain can improve its symbiotic performance under salt stress and indicate that ACC deaminase can play an important role in facilitating plant-rhizobium interaction under salinity conditions.

  14. 1-Aminocyclopropane-1-Carboxylate Deaminase from Pseudomonas stutzeri A1501 Facilitates the Growth of Rice in the Presence of Salt or Heavy Metals.

    PubMed

    Han, Yunlei; Wang, Rui; Yang, Zhirong; Zhan, Yuhua; Ma, Yao; Ping, Shuzhen; Zhang, Liwen; Lin, Min; Yan, Yongliang

    2015-07-01

    1-Aminocyclopropane-1-carboxylate (ACC) deaminase, which is encoded by some bacteria, can reduce the amount of ethylene, a root elongation inhibitor, and stimulate the growth of plants under various environmental stresses. The presence of ACC deaminase activity and the regulation of ACC in several rhizospheric bacteria have been reported. The nitrogen-fixing Pseudomonas stutzeri A1501 is capable of endophytic association with rice plants and promotes the growth of rice. However, the functional identification of ACC deaminase has not been performed. In this study, the proposed effect of ACC deaminase in P. stutzeri A1501 was investigated. Genome mining showed that P. stutzeri A1501 carries a single gene encoding ACC deaminase, designated acdS. The acdS mutant was devoid of ACC deaminase activity and was less resistant to NaCl and NiCl2 compared with the wild-type. Furthermore, inactivation of acdS greatly impaired its nitrogenase activity under salt stress conditions. It was also observed that mutation of the acdS gene led to loss of the ability to promote the growth of rice under salt or heavy metal stress. Taken together, this study illustrates the essential role of ACC deaminase, not only in enhancing the salt or heavy metal tolerance of bacteria but also in improving the growth of plants, and provides a theoretical basis for studying the interaction between plant growth-promoting rhizobacteria and plants. PMID:25674802

  15. 1-Aminocyclopropane-1-Carboxylate Deaminase from Pseudomonas stutzeri A1501 Facilitates the Growth of Rice in the Presence of Salt or Heavy Metals.

    PubMed

    Han, Yunlei; Wang, Rui; Yang, Zhirong; Zhan, Yuhua; Ma, Yao; Ping, Shuzhen; Zhang, Liwen; Lin, Min; Yan, Yongliang

    2015-07-01

    1-Aminocyclopropane-1-carboxylate (ACC) deaminase, which is encoded by some bacteria, can reduce the amount of ethylene, a root elongation inhibitor, and stimulate the growth of plants under various environmental stresses. The presence of ACC deaminase activity and the regulation of ACC in several rhizospheric bacteria have been reported. The nitrogen-fixing Pseudomonas stutzeri A1501 is capable of endophytic association with rice plants and promotes the growth of rice. However, the functional identification of ACC deaminase has not been performed. In this study, the proposed effect of ACC deaminase in P. stutzeri A1501 was investigated. Genome mining showed that P. stutzeri A1501 carries a single gene encoding ACC deaminase, designated acdS. The acdS mutant was devoid of ACC deaminase activity and was less resistant to NaCl and NiCl2 compared with the wild-type. Furthermore, inactivation of acdS greatly impaired its nitrogenase activity under salt stress conditions. It was also observed that mutation of the acdS gene led to loss of the ability to promote the growth of rice under salt or heavy metal stress. Taken together, this study illustrates the essential role of ACC deaminase, not only in enhancing the salt or heavy metal tolerance of bacteria but also in improving the growth of plants, and provides a theoretical basis for studying the interaction between plant growth-promoting rhizobacteria and plants.

  16. Expression and characterization of 1-aminocyclopropane-1-carboxylate deaminase from the rhizobacterium Pseudomonas putida UW4: a key enzyme in bacterial plant growth promotion.

    PubMed

    Hontzeas, Nikos; Zoidakis, Jérôme; Glick, Bernard R; Abu-Omar, Mahdi M

    2004-12-01

    The enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACCD) converts ACC, the precursor of the plant hormone ethylene, to alpha-ketobutyrate and ammonium. This enzyme has been identified in soil bacteria and has been proposed to play a key role in microbe-plant association. A soluble recombinant ACCD from Pseudomonas putida UW4 of molecular weight 41 kDa has been cloned, expressed, and purified. It showed selectivity and high activity towards the substrate ACC: K(M)=3.4+/-0.2 mM and k(cat)=146+/-5 min(-1) at pH 8.0 and 22 degrees C. The enzyme displayed optimal activity at pH 8.0 with a sharp decline to essentially no activity below pH 6.5 and a slightly less severe tapering in activity at higher pH resulting in loss of activity at pH>10. The major component of the enzyme's secondary structure was determined to be alpha-helical by circular dichroism (CD). P. putida UW4 ACCD unfolded at 60 degrees C as determined by its CD temperature profile as well as by differential scanning microcalorimetry (DSC). Enzyme activity was knocked out in the point mutant Gly44Asp. Modeling this mutation into the known yeast ACCD structure shed light on the role this highly conserved residue plays in allowing substrate accessibility to the active site. This enzyme's biochemical and biophysical properties will serve as an important reference point to which newly isolated ACC deaminases from other organisms can be compared. PMID:15588698

  17. Novel Rhizosphere Soil Alleles for the Enzyme 1-Aminocyclopropane-1-Carboxylate Deaminase Queried for Function with an In Vivo Competition Assay

    PubMed Central

    Jin, Zhao; Di Rienzi, Sara C.; Janzon, Anders; Werner, Jeff J.; Angenent, Largus T.; Dangl, Jeffrey L.; Fowler, Douglas M.

    2015-01-01

    Metagenomes derived from environmental microbiota encode a vast diversity of protein homologs. How this diversity impacts protein function can be explored through selection assays aimed to optimize function. While artificially generated gene sequence pools are typically used in selection assays, their usage may be limited because of technical or ethical reasons. Here, we investigate an alternative strategy, the use of soil microbial DNA as a starting point. We demonstrate this approach by optimizing the function of a widely occurring soil bacterial enzyme, 1-aminocyclopropane-1-carboxylate (ACC) deaminase. We identified a specific ACC deaminase domain region (ACCD-DR) that, when PCR amplified from the soil, produced a variant pool that we could swap into functional plasmids carrying ACC deaminase-encoding genes. Functional clones of ACC deaminase were selected for in a competition assay based on their capacity to provide nitrogen to Escherichia coli in vitro. The most successful ACCD-DR variants were identified after multiple rounds of selection by sequence analysis. We observed that previously identified essential active-site residues were fixed in the original unselected library and that additional residues went to fixation after selection. We identified a divergent essential residue whose presence hints at the possible use of alternative substrates and a cluster of neutral residues that did not influence ACCD performance. Using an artificial ACCD-DR variant library generated by DNA oligomer synthesis, we validated the same fixation patterns. Our study demonstrates that soil metagenomes are useful starting pools of protein-coding-gene diversity that can be utilized for protein optimization and functional characterization when synthetic libraries are not appropriate. PMID:26637602

  18. Expression of an exogenous 1-aminocyclopropane-1-carboxylate deaminase gene in psychrotolerant bacteria modulates ethylene metabolism and cold induced genes in tomato under chilling stress.

    PubMed

    Subramanian, Parthiban; Krishnamoorthy, Ramasamy; Chanratana, Mak; Kim, Kiyoon; Sa, Tongmin

    2015-04-01

    The role of stress induced ethylene under low temperature stress has been controversial and hitherto remains unclear. In the present study, 1-aminocyclopropane-1-carboxylate deaminase (ACCD) gene, acdS expressing mutant strains were generated from ACCD negative psychrotolerant bacterial strains Flavobacterium sp. OR306 and Pseudomonas frederiksbergensis OS211, isolated from agricultural soil during late winter. After transformation with plasmid pRKACC which contained the acdS gene, both the strains were able to exhibit ACCD activity in vitro. The effect of this ACCD under chilling stress with regards to ethylene was studied in tomato plants inoculated with both acdS expressing and wild type bacteria. On exposing the plants to one week of chilling treatment at 12/10 °C, it was found that stress ethylene, ACC accumulation and ACO activity which are markers of ethylene stress, were significantly reduced in plants inoculated with the acdS gene transformed mutants. In case of plants inoculated with strain OS211-acdS, ethylene emission, ACC accumulation and ACO activity was significantly reduced by 52%, 75.9% and 23.2% respectively compared to uninoculated control plants. Moreover, expression of cold induced LeCBF1 and LeCBF3 genes showed that these genes were significantly induced by the acdS transformed mutants in addition to reduced expression of ethylene-responsive transcription factor 13 (ETF-13) and ACO genes. Induced expression of LeCBF1 and LeCBF3 in plants inoculated with acdS expressing mutants compared to wild type strains show that physiologically evolved stress ethylene and its transcription factors play a role in regulation of cold induced genes as reported earlier in the literature.

  19. Inducing salt tolerance in mung bean through coinoculation with rhizobia and plant-growth-promoting rhizobacteria containing 1-aminocyclopropane-1-carboxylate deaminase.

    PubMed

    Ahmad, Maqshoof; Zahir, Zahir A; Asghar, H Naeem; Asghar, M

    2011-07-01

    Twenty-five strains of plant-growth-promoting rhizobacteria (PGPR) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase and 10 strains of rhizobia were isolated from rhizosphere soil samples and nodules of mung bean. They were screened in separate trials under salt-stressed axenic conditions. The three most effective strains of PGPR (Mk1, Pseudomonas syringae ; Mk20, Pseudomonas fluorescens ; and Mk25, Pseudomonas fluorescens biotype G) and Rhizobium phaseoli strains M1, M6, and M9 were evaluated in coinoculation for their growth-promoting activity at three salinity levels (original, 4 dS·m(-1), and 6 dS·m(-1)) under axenic conditions. The results showed that salinity stress significantly reduced plant growth but inoculation with PGPR containing ACC deaminase and rhizobia enhanced plant growth, thus reducing the inhibitory effect of salinity. However, their combined application was more effective under saline conditions, and the combination Mk20 × M6 was the most efficient for improving seedling growth and nodulation. The effect of high ethylene concentrations on plant growth and the performance of these strains for reducing the negative impact of saline stress was also evaluated by conducting a classical triple-response bioassay. The intensity of the classical triple response decreased owing to inoculation with these strains, with the root and shoot lengths of inoculated mung bean seedlings increasing and stem diameter decreasing, which is a typical response to the dilution in a classical triple response bioassay. Thus, coinoculation with PGPR containing ACC deaminase and Rhizobium spp. could be a useful approach for inducing salt tolerance and thus improving growth and nodulation in mung bean under salt-affected conditions.

  20. ACC (1-aminocyclopropane-1-carboxylate) deaminase activity, a widespread trait in Burkholderia species, and its growth-promoting effect on tomato plants.

    PubMed

    Onofre-Lemus, Janette; Hernández-Lucas, Ismael; Girard, Lourdes; Caballero-Mellado, Jesús

    2009-10-01

    The genus Burkholderia includes pathogens of plants and animals and some human opportunistic pathogens, such as the Burkholderia cepacia complex (Bcc), but most species are nonpathogenic, plant associated, and rhizospheric or endophytic. Since rhizobacteria expressing ACC (1-aminocyclopropane-1-carboxylate) deaminase may enhance plant growth by lowering plant ethylene levels, in this work we investigated the presence of ACC deaminase activity and the acdS gene in 45 strains, most of which are plant associated, representing 20 well-known Burkholderia species. The results demonstrated that ACC deaminase activity is a widespread feature in the genus Burkholderia, since 18 species exhibited ACC deaminase activities in the range from 2 to 15 mumol of alpha-ketobutyrate/h/mg protein, which suggests that these species may be able to modulate ethylene levels and enhance plant growth. In these 18 Burkholderia species the acdS gene sequences were highly conserved (76 to 99% identity). Phylogenetic analysis of acdS gene sequences in Burkholderia showed tight clustering of the Bcc species, which were clearly distinct from diazotrophic plant-associated Burkholderia species. In addition, an acdS knockout mutant of the N(2)-fixing bacterium Burkholderia unamae MTl-641(T) and a transcriptional acdSp-gusA fusion constructed in this strain showed that ACC deaminase could play an important role in promotion of the growth of tomato plants. The widespread ACC deaminase activity in Burkholderia species and the common association of these species with plants suggest that this genus could be a major contributor to plant growth under natural conditions.

  1. Possible Role of 1-Aminocyclopropane-1-Carboxylate (ACC) Deaminase Activity of Sinorhizobium sp. BL3 on Symbiosis with Mung Bean and Determinate Nodule Senescence.

    PubMed

    Tittabutr, Panlada; Sripakdi, Sudarat; Boonkerd, Nantakorn; Tanthanuch, Waraporn; Minamisawa, Kiwamu; Teaumroong, Neung

    2015-01-01

    Sinorhizobium sp. BL3 forms symbiotic interactions with mung bean (Vigna radiata) and contains lrpL-acdS genes, which encode the 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme that cleaves ACC, a precursor of plant ethylene synthesis. Since ethylene interferes with nodule formation in some legumes and plays a role in senescence in plant cells, BL3-enhancing ACC deaminase activity (BL3(+)) and defective mutant (BL3(-)) strains were constructed in order to investigate the effects of this enzyme on symbiosis and nodule senescence. Nodulation competitiveness was weaker in BL3(-) than in the wild-type, but was stronger in BL3(+). The inoculation of BL3(-) into mung bean resulted in less plant growth, a lower nodule dry weight, and smaller nodule number than those in the wild-type, whereas the inoculation of BL3(+) had no marked effects. However, similar nitrogenase activity was observed with all treatments; it was strongly detected 3 weeks after the inoculation and gradually declined with time, indicating senescence. The rate of plant nodulation by BL3(+) increased in a time-dependent manner. Nodules occupied by BL3(-) formed smaller symbiosomes, and bacteroid degradation was more prominent than that in the wild-type 7 weeks after the inoculation. Changes in biochemical molecules during nodulation were tracked by Fourier Transform Infrared (FT-IR) microspectroscopy, and the results obtained confirmed that aging processes differed in nodules occupied by BL3 and BL3(-). This is the first study to show the possible role of ACC deaminase activity in senescence in determinate nodules. Our results suggest that an increase in ACC deaminase activity in this strain does not extend the lifespan of nodules, whereas the lack of this activity may accelerate nodule senescence.

  2. Novel Rhizosphere Soil Alleles for the Enzyme 1-Aminocyclopropane-1-Carboxylate Deaminase Queried for Function with an In Vivo Competition Assay.

    PubMed

    Jin, Zhao; Di Rienzi, Sara C; Janzon, Anders; Werner, Jeff J; Angenent, Largus T; Dangl, Jeffrey L; Fowler, Douglas M; Ley, Ruth E

    2015-12-04

    Metagenomes derived from environmental microbiota encode a vast diversity of protein homologs. How this diversity impacts protein function can be explored through selection assays aimed to optimize function. While artificially generated gene sequence pools are typically used in selection assays, their usage may be limited because of technical or ethical reasons. Here, we investigate an alternative strategy, the use of soil microbial DNA as a starting point. We demonstrate this approach by optimizing the function of a widely occurring soil bacterial enzyme, 1-aminocyclopropane-1-carboxylate (ACC) deaminase. We identified a specific ACC deaminase domain region (ACCD-DR) that, when PCR amplified from the soil, produced a variant pool that we could swap into functional plasmids carrying ACC deaminase-encoding genes. Functional clones of ACC deaminase were selected for in a competition assay based on their capacity to provide nitrogen to Escherichia coli in vitro. The most successful ACCD-DR variants were identified after multiple rounds of selection by sequence analysis. We observed that previously identified essential active-site residues were fixed in the original unselected library and that additional residues went to fixation after selection. We identified a divergent essential residue whose presence hints at the possible use of alternative substrates and a cluster of neutral residues that did not influence ACCD performance. Using an artificial ACCD-DR variant library generated by DNA oligomer synthesis, we validated the same fixation patterns. Our study demonstrates that soil metagenomes are useful starting pools of protein-coding-gene diversity that can be utilized for protein optimization and functional characterization when synthetic libraries are not appropriate.

  3. Possible Role of 1-Aminocyclopropane-1-Carboxylate (ACC) Deaminase Activity of Sinorhizobium sp. BL3 on Symbiosis with Mung Bean and Determinate Nodule Senescence

    PubMed Central

    Tittabutr, Panlada; Sripakdi, Sudarat; Boonkerd, Nantakorn; Tanthanuch, Waraporn; Minamisawa, Kiwamu; Teaumroong, Neung

    2015-01-01

    Sinorhizobium sp. BL3 forms symbiotic interactions with mung bean (Vigna radiata) and contains lrpL-acdS genes, which encode the 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme that cleaves ACC, a precursor of plant ethylene synthesis. Since ethylene interferes with nodule formation in some legumes and plays a role in senescence in plant cells, BL3-enhancing ACC deaminase activity (BL3+) and defective mutant (BL3−) strains were constructed in order to investigate the effects of this enzyme on symbiosis and nodule senescence. Nodulation competitiveness was weaker in BL3− than in the wild-type, but was stronger in BL3+. The inoculation of BL3− into mung bean resulted in less plant growth, a lower nodule dry weight, and smaller nodule number than those in the wild-type, whereas the inoculation of BL3+ had no marked effects. However, similar nitrogenase activity was observed with all treatments; it was strongly detected 3 weeks after the inoculation and gradually declined with time, indicating senescence. The rate of plant nodulation by BL3+ increased in a time-dependent manner. Nodules occupied by BL3− formed smaller symbiosomes, and bacteroid degradation was more prominent than that in the wild-type 7 weeks after the inoculation. Changes in biochemical molecules during nodulation were tracked by Fourier Transform Infrared (FT-IR) microspectroscopy, and the results obtained confirmed that aging processes differed in nodules occupied by BL3 and BL3−. This is the first study to show the possible role of ACC deaminase activity in senescence in determinate nodules. Our results suggest that an increase in ACC deaminase activity in this strain does not extend the lifespan of nodules, whereas the lack of this activity may accelerate nodule senescence. PMID:26657304

  4. Effect of drought and high solar radiation on 1-aminocyclopropane-1-carboxylic acid and abscisic acid concentrations in Rosmarinus officinalis plants.

    PubMed

    Munné-Bosch, Sergi; López-Carbonell, Marta; Alegre, Leonor; Van Onckelen, Harry A

    2002-03-01

    The endogenous concentrations of ACC and ABA were measured, at predawn and at maximum solar radiation, during a summer drought, and recovery after autumn rainfalls, in rosemary (Rosmarinus officinalis L.), a drought-tolerant species, growing under Mediterranean field conditions. During the summer, plants were subjected to both water deficit and high solar radiation. Plants showed severe reductions in shoot water potential to -3 MPa, which were associated with drastic stomatal closure (73%), a decrease in net photosynthesis, reaching almost zero, and a severe chlorophyll loss (74%). Despite the severity of the stress, plants recovered after the autumn rainfalls. The concentration of ACC was not enhanced by drought, and at predawn these concentrations remained constant at approximately 600 pmol ACC-1 DW throughout the experiment. Thus, ethylene did not regulate the response of rosemary to drought. However, a sharp increase in ACC levels between predawn and midday was observed. This increase was positively correlated to the intensity of the incident solar radiation. ACC levels recorded in June at midday reached 16 000 pmol g DW and in October values of 1000 pmol g-1 DW were observed. In contrast, in drought-stressed plants predawn concentrations of ABA were up to 130-fold those of recovered plants, and the levels of ABA scored at midday were double of those scored at predawn. In conclusion, although drought-stressed rosemary plants showed a relatively moderate ABA accumulation (approximately 500 pmol g-1 DW#, at predawn), it seems to be an essential factor for the regulation of the plant response to stress, thereby enabling a rapid recovery after stress release, although other mechanisms can not be excluded. As drought stress did not induce ACC accumulation, it was concluded that ethylene production was not a major factor in the drought stress resistance of rosemary plants. The increased ACC and ABA concentrations at midday were correlated with day length and light intensity and not with the water status of the plant.

  5. The final step of the ethylene biosynthesis pathway in turnip tops (Brassica rapa): molecular characterization of the 1-aminocyclopropane-1-carboxylate oxidase BrACO1 throughout zygotic embryogenesis and germination of heterogeneous seeds.

    PubMed

    Del Carmen Rodríguez-Gacio, María; Nicolás, Carlos; Matilla, Angel Jesús

    2004-05-01

    In a previous report from the present authors, it was shown that the 1-aminocyclopropane-1-carboxylate (ACC) oxidation may play a crucial role during zygotic embryogenesis of turnip tops seeds. The present study was performed to elucidate the contribution of the silique-wall and seeds in ethylene production during this developmental process. ACC content in the silique wall is only higher than in seeds during the middle phases of zygotic embryogenesis. The ACC-oxidase (ACO) activity peaks in the silique-wall and seeds during the onset of embryogenesis, declining gradually afterwards, being undetectable during desiccation period. Using reverse transcriptase-polymerase chain reaction, one cDNA clone coding for an ACO and called BrACO1, was isolated. The deduced protein for BrACO1 has a molecular weight of 36.8 kDa and a high homology with other crucifer ACOs. The heterologous expression of this cDNA confirmed that BrACO1 is an ACO. The expression of this gene was high during the first phases of silique-wall development, low during the middle phases and undetectable during desiccation. By contrast, BrACO1 transcript was accumulated only in the earliest phases of seed embryogenesis and may participate in the highest ACO activity and ethylene production by seeds at the beginning of embryogenesis. Finally, in this work a correlation between the heterogeneity of Brassica rapa L. cv. Rapa seeds and the ability to oxidize the ACC to ethylene has been demonstrated.

  6. Expression characteristics of CS-ACS1, CS-ACS2 and CS-ACS3, three members of the 1-aminocyclopropane-1-carboxylate synthase gene family in cucumber (Cucumis sativus L.) fruit under carbon dioxide stress.

    PubMed

    Mathooko, F M; Mwaniki, M W; Nakatsuka, A; Shiomi, S; Kubo, Y; Inaba, A; Nakamura, R

    1999-02-01

    We investigated the expression pattern of three 1-aminocyclopropane-1-carboxylate (ACC) synthase genes, CS-ACS1, CS-ACS2 and CS-ACS3 in cucumber (Cucumis sativus L.) fruit under CO2 stress. CO2 stress-induced ethylene production paralleled the accumulation of only CS-ACS1 transcripts which disappeared upon withdrawal of CO2. Cycloheximide inhibited the CO2 stress-induced ethylene production but superinduced the accumulation of CS-ACS1 transcript. At higher concentrations, cycloheximide also induced the accumulation of CS-ACS2 and CS-ACS3 transcripts. In the presence of CO2 and cycloheximide, the accumulation of CS-ACS2 transcript occurred within 1 h, disappeared after 3 h and increased greatly upon withdrawal of CO2. Inhibitors of protein kinase and types 1 and 2A protein phosphatases which inhibited and stimulated, respectively, CO2 stress-induced ethylene production had little effect on the expression of these genes. The results presented here identify CS-ACS1 as the main ACC synthase gene responsible for the increased ethylene biosynthesis in cucumber fruit under CO2 stress and suggest that this gene is a primary response gene and its expression is under negative control since it is expressed by treatment with cycloheximide. The results further suggest that the regulation of CO2 stress-induced ethylene biosynthesis by reversible protein phosphorylation does not result from enhanced ACC synthase transcription. PMID:10202812

  7. Analysis of genomic DNA of DcACS1, a 1-aminocyclopropane-1-carboxylate synthase gene, expressed in senescing petals of carnation (Dianthus caryophyllus) and its orthologous genes in D. superbus var. longicalycinus.

    PubMed

    Harada, Taro; Murakoshi, Yuino; Torii, Yuka; Tanase, Koji; Onozaki, Takashi; Morita, Shigeto; Masumura, Takehiro; Satoh, Shigeru

    2011-04-01

    Carnation (Dianthus caryophyllus) flowers exhibit climacteric ethylene production followed by petal wilting, a senescence symptom. DcACS1, which encodes 1-aminocyclopropane-1-carboxylate synthase (ACS), is a gene involved in this phenomenon. We determined the genomic DNA structure of DcACS1 by genomic PCR. In the genome of 'Light Pink Barbara', we found two distinct nucleotide sequences: one corresponding to the gene previously shown as DcACS1, designated here as DcACS1a, and the other novel one designated as DcACS1b. It was revealed that both DcACS1a and DcACS1b have five exons and four introns. These two genes had almost identical nucleotide sequences in exons, but not in some introns and 3'-UTR. Analysis of transcript accumulation revealed that DcACS1b is expressed in senescing petals as well as DcACS1a. Genomic PCR analysis of 32 carnation cultivars showed that most cultivars have only DcACS1a and some have both DcACS1a and DcACS1b. Moreover, we found two DcACS1 orthologous genes with different nucleotide sequences from D. superbus var. longicalycinus, and designated them as DsuACS1a and DsuACS1b. Petals of D. superbus var. longicalycinus produced ethylene in response to exogenous ethylene, accompanying accumulation of DsuACS1 transcripts. These data suggest that climacteric ethylene production in flowers was genetically established before the cultivation of carnation.

  8. Ethylene Biosynthesis Is Promoted by Very-Long-Chain Fatty Acids during Lysigenous Aerenchyma Formation in Rice Roots.

    PubMed

    Yamauchi, Takaki; Shiono, Katsuhiro; Nagano, Minoru; Fukazawa, Aya; Ando, Miho; Takamure, Itsuro; Mori, Hitoshi; Nishizawa, Naoko K; Kawai-Yamada, Maki; Tsutsumi, Nobuhiro; Kato, Kiyoaki; Nakazono, Mikio

    2015-09-01

    In rice (Oryza sativa) roots, lysigenous aerenchyma, which is created by programmed cell death and lysis of cortical cells, is constitutively formed under aerobic conditions, and its formation is further induced under oxygen-deficient conditions. Ethylene is involved in the induction of aerenchyma formation. reduced culm number1 (rcn1) is a rice mutant in which the gene encoding the ATP-binding cassette transporter RCN1/OsABCG5 is defective. Here, we report that the induction of aerenchyma formation was reduced in roots of rcn1 grown in stagnant deoxygenated nutrient solution (i.e. under stagnant conditions, which mimic oxygen-deficient conditions in waterlogged soils). 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a key enzyme in ethylene biosynthesis. Stagnant conditions hardly induced the expression of ACS1 in rcn1 roots, resulting in low ethylene production in the roots. Accumulation of saturated very-long-chain fatty acids (VLCFAs) of 24, 26, and 28 carbons was reduced in rcn1 roots. Exogenously supplied VLCFA (26 carbons) increased the expression level of ACS1 and induced aerenchyma formation in rcn1 roots. Moreover, in rice lines in which the gene encoding a fatty acid elongase, CUT1-LIKE (CUT1L; a homolog of the gene encoding Arabidopsis CUT1, which is required for cuticular wax production), was silenced, both ACS1 expression and aerenchyma formation were reduced. Interestingly, the expression of ACS1, CUT1L, and RCN1/OsABCG5 was induced predominantly in the outer part of roots under stagnant conditions. These results suggest that, in rice under oxygen-deficient conditions, VLCFAs increase ethylene production by promoting 1-aminocyclopropane-1-carboxylic acid biosynthesis in the outer part of roots, which, in turn, induces aerenchyma formation in the root cortex.

  9. Ethylene Biosynthesis Is Promoted by Very-Long-Chain Fatty Acids during Lysigenous Aerenchyma Formation in Rice Roots1

    PubMed Central

    Yamauchi, Takaki; Shiono, Katsuhiro; Nagano, Minoru; Fukazawa, Aya; Ando, Miho; Takamure, Itsuro; Mori, Hitoshi; Nishizawa, Naoko K.; Kawai-Yamada, Maki; Tsutsumi, Nobuhiro; Kato, Kiyoaki; Nakazono, Mikio

    2015-01-01

    In rice (Oryza sativa) roots, lysigenous aerenchyma, which is created by programmed cell death and lysis of cortical cells, is constitutively formed under aerobic conditions, and its formation is further induced under oxygen-deficient conditions. Ethylene is involved in the induction of aerenchyma formation. reduced culm number1 (rcn1) is a rice mutant in which the gene encoding the ATP-binding cassette transporter RCN1/OsABCG5 is defective. Here, we report that the induction of aerenchyma formation was reduced in roots of rcn1 grown in stagnant deoxygenated nutrient solution (i.e. under stagnant conditions, which mimic oxygen-deficient conditions in waterlogged soils). 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a key enzyme in ethylene biosynthesis. Stagnant conditions hardly induced the expression of ACS1 in rcn1 roots, resulting in low ethylene production in the roots. Accumulation of saturated very-long-chain fatty acids (VLCFAs) of 24, 26, and 28 carbons was reduced in rcn1 roots. Exogenously supplied VLCFA (26 carbons) increased the expression level of ACS1 and induced aerenchyma formation in rcn1 roots. Moreover, in rice lines in which the gene encoding a fatty acid elongase, CUT1-LIKE (CUT1L; a homolog of the gene encoding Arabidopsis CUT1, which is required for cuticular wax production), was silenced, both ACS1 expression and aerenchyma formation were reduced. Interestingly, the expression of ACS1, CUT1L, and RCN1/OsABCG5 was induced predominantly in the outer part of roots under stagnant conditions. These results suggest that, in rice under oxygen-deficient conditions, VLCFAs increase ethylene production by promoting 1-aminocyclopropane-1-carboxylic acid biosynthesis in the outer part of roots, which, in turn, induces aerenchyma formation in the root cortex. PMID:26036614

  10. Leaf Abscission Induced by Ethylene in Water-Stressed Intact Seedlings of Cleopatra Mandarin Requires Previous Abscisic Acid Accumulation in Roots.

    PubMed

    Gomez-Cadenas, A.; Tadeo, F. R.; Talon, M.; Primo-Millo, E.

    1996-09-01

    The involvement of abscisic acid (ABA) in the process of leaf abscission induced by 1-aminocyclopropane-1-carboxylic acid (ACC) transported from roots to shoots in Cleopatra mandarin (Citrus reshni Hort. ex Tan.) seedlings grown under water stress was studied using norflurazon (NF). Water stress induced both ABA (24-fold) and ACC (16-fold) accumulation in roots and arrested xylem flow. Leaf bulk ABA also increased (8-fold), although leaf abscission did not occur. Shortly after rehydration, root ABA and ACC returned to their prestress levels, whereas sharp and transitory increases of ACC (17-fold) and ethylene (10-fold) in leaves and high percentages of abscission (up to 47%) were observed. NF suppressed the ABA and ACC accumulation induced by water stress in roots and the sharp increases of ACC and ethylene observed after rewatering in leaves. NF also reduced leaf abscission (7-10%). These results indicate that water stress induces root ABA accumulation and that this is required for the process of leaf abscission to occur. It was also shown that exogenous ABA increases ACC levels in roots but not in leaves. Collectively, the data suggest that ABA, the primary sensitive signal to water stress, modulates the levels of ethylene, which is the hormonal activator of leaf abscission. This assumption implies that root ACC levels are correlated with root ABA amounts in a dependent way, which eventually links water status to an adequate, protective response such as leaf abscission.

  11. Differential Expression and Internal Feedback Regulation of 1-Aminocyclopropane-1-Carboxylate Synthase, 1-Aminocyclopropane-1-Carboxylate Oxidase, and Ethylene Receptor Genes in Tomato Fruit during Development and Ripening1

    PubMed Central

    Nakatsuka, Akira; Murachi, Shiho; Okunishi, Hironori; Shiomi, Shinjiro; Nakano, Ryohei; Kubo, Yasutaka; Inaba, Akitsugu

    1998-01-01

    We investigated the feedback regulation of ethylene biosynthesis in tomato (Lycopersicon esculentum) fruit with respect to the transition from system 1 to system 2 ethylene production. The abundance of LE-ACS2, LE-ACS4, and NR mRNAs increased in the ripening fruit concomitant with a burst in ethylene production. These increases in mRNAs with ripening were prevented to a large extent by treatment with 1-methylcyclopropene (MCP), an ethylene action inhibitor. Transcripts for the LE-ACS6 gene, which accumulated in preclimacteric fruit but not in untreated ripening fruit, did accumulate in ripening fruit treated with MCP. Treatment of young fruit with propylene prevented the accumulation of transcripts for this gene. LE-ACS1A, LE-ACS3, and TAE1 genes were expressed constitutively in the fruit throughout development and ripening irrespective of whether the fruit was treated with MCP or propylene. The transcripts for LE-ACO1 and LE-ACO4 genes already existed in preclimacteric fruit and increased greatly when ripening commenced. These increases in LE-ACO mRNA with ripening were also prevented by treatment with MCP. The results suggest that in tomato fruit the preclimacteric system 1 ethylene is possibly mediated via constitutively expressed LE-ACS1A and LE-ACS3 and negatively feedback-regulated LE-ACS6 genes with preexisting LE-ACO1 and LE-ACO4 mRNAs. At the onset of the climacteric stage, it shifts to system 2 ethylene, with a large accumulation of LE-ACS2, LE-ACS4, LE-ACO1, and LE-ACO4 mRNAs as a result of a positive feedback regulation. This transition from system 1 to system 2 ethylene production might be related to the accumulated level of NR mRNA. PMID:9847103

  12. 1-aminocyclopropane-1-carboxylate deaminase from Pseudomonas fluorescens promoting the growth of Chinese cabbage and its polyclonal antibody.

    PubMed

    Soh, Byoung Yul; Lee, Gun Woong; Go, Eun Byeul; Kim, Byeo-Ri; Lee, Kui-Jae; Chae, Jong-Chan

    2014-05-01

    Bacterial 1-aminocyclopropane-1-carboxlyate (ACC) deaminase (AcdS) is an enzyme that cleaves ACC, a precursor of the plant hormone ethylene, into α-ketobutyrate and ammonia. The acdS gene was cloned from Pseudomonas fluorescens, which was capable of improving the seedling of Chinese cabbage under salinity condition. The recombinant AcdS (rAcdS) exhibited optimal activity at pH 8.5 and 30°C. Strong activity was sustained at up to 100 mM NaCl. The polyclonal anti-P. fluorescens AcdS antibody was produced in a rabbit that had been immunized with the purified rAcdS. This antibody successfully recognized the homologous antigens derived from the total proteins of isolated plant growth-promoting microorganisms. A statistically significant correlation was observed between the intensity of hybridization signal and AcdS activity measured by a biochemical method, suggesting its application as a useful indicator for active deaminases.

  13. Southern blight disease of tomato control by 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing Paenibacillus lentimorbus B-30488

    PubMed Central

    Dixit, Ritu; Agrawal, Lalit; Gupta, Swati; Kumar, Manoj; Yadav, Sumit; Chauhan, Puneet Singh; Nautiyal, Chandra Shekhar

    2016-01-01

    abstract Tomato cultivation is highly susceptible for soil born diseases and among them southern blight disease caused by Scelerotium rolfsii is very common. For its management use of chemical fungicides is not very successful as their spores are able to survive for many years in the soil. As an alternative eco-friendly approach to control the disease antagonistic microbes are being characterized.Among them plant growth promoting rhizobacteria Paenibacillus lentimorbus B-30488 (B-30488) with antagonistic properties, multiple PGP attributes stress tolerance and ACC deaminase enzyme activity is characterized to decipher its mode of action against S. rolfsii under in vitro and in vivo conditions. In vitro results obtained from this study clearly demonstrate that B-30488 has ability to show antagonistic properties under different abiotic stresses against S. rolfsii. Similar results were also obtained from in vivo experiments where B-30488 inoculation has efficiently controlled the disease caused by S. rolfsii and improve the plant growth. Deleterious enhanced ethylene level in S. rolfsii infected plants was also ameliorated by inoculation of ACC deaminase producing B-30488. The ACC accumulation, ACO and ACS activities were also modulated in S. rolfsii infected plants. Results from defense enzymes and other biochemical attributes were also support the role of B-30488 inoculation in ameliorating the biotic stress caused by S. rolfsii in tomato plants. These results were further validated by pathogen related gene expression analysis by real time PCR. Overall results from the present study may be concluded that ACC deaminase producing B-30488 has ability to control the southern blight disease caused by S. rolfsii and commercial bioinoculant package may be developed. PMID:26825539

  14. Enhanced ethylene emissions from red and Norway spruce exposed to acidic mists

    SciTech Connect

    Chen, Yimin; Wellburn, A.R. )

    1989-09-01

    Acidic cloudwater is believed to cause needle injury and to decrease winter hardiness in conifers. During simulations of these adverse conditions, rates of ethylene emissions from and levels of 1-aminocyclopropane-1-carboxylic acid (ACC) in both red and Norway spruce needles increased as a result of treatment with acidic mists but amounts of 1-malonyl(amino)cyclopropane-1-carboxylic acid remained unchanged. However, release of significant quantities of ethylene by another mechanism independent of ACC was also detected from brown needles. Application of exogenous plant growth regulators such as auxin, kinetic, abscisic acid and gibberellic acid (each 0.1 millimolar) had no obvious effects on the rates of basal or stress ethylene production from Norway spruce needles. The kinetics of ethylene formation by acidic mist-stressed needles suggest that there is no active inhibitive mechanism in spruce to prevent stress ethylene being released once ACC has been formed.

  15. Burst of ethylene upon horizontal placement of tomato seedlings

    NASA Technical Reports Server (NTRS)

    Harrison, M.; Pickard, B. G.

    1984-01-01

    Seedlings of Lycopersicon esculentum Mill. cv Rutgers emit a pulse of ethylene during the first 2 to 4 minutes following horizontal placement. Because this burst appears too rapid and brief to be mediated by increase in net activity of 1-aminocyclopropane-1-carboxylic acid synthase, it might result form accelerated transformation of vacuolar 1-aminocyclopropane-1-carboxylic acid to ethylene.

  16. Determination of 1-aminocycopropane-1-carboxylic acid (ACC) to assess the effects of ACC deaminase-containing bacteria on roots of canola seedlings.

    PubMed

    Penrose, D M; Moffatt, B A; Glick, B R

    2001-01-01

    Previously, it was proposed that plant growth-promoting bacteria that possess the enzyme, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, can reduce the amount of ethylene produced by a plant and thereby promote root elongation. To test this model, canola seeds were imbibed in the presence of the chemical ethylene inhibitor, 2-aminoethoxyvinyl glycine (AVG), various strains of plant growth-promoting bacteria, and a psychrophilic bacterium containing an ACC deaminase gene on a broad host range plasmid. The extent of root elongation and levels of ACC, the immediate precursor of ethylene, were measured in the canola seedling roots. A modification of the Waters AccQ.Tag Amino Acid Analysis Method was used to quantify ACC in the root extracts. It was found that, in the presence of the ethylene inhibitor, AVG, or any one of several ACC deaminase-containing strains of bacteria, the growth of canola seedling roots was enhanced and the ACC levels in these roots were lowered.

  17. Bile acid transporters

    PubMed Central

    Dawson, Paul A.; Lan, Tian; Rao, Anuradha

    2009-01-01

    In liver and intestine, transporters play a critical role in maintaining the enterohepatic circulation and bile acid homeostasis. Over the past two decades, there has been significant progress toward identifying the individual membrane transporters and unraveling their complex regulation. In the liver, bile acids are efficiently transported across the sinusoidal membrane by the Na+ taurocholate cotransporting polypeptide with assistance by members of the organic anion transporting polypeptide family. The bile acids are then secreted in an ATP-dependent fashion across the canalicular membrane by the bile salt export pump. Following their movement with bile into the lumen of the small intestine, bile acids are almost quantitatively reclaimed in the ileum by the apical sodium-dependent bile acid transporter. The bile acids are shuttled across the enterocyte to the basolateral membrane and effluxed into the portal circulation by the recently indentified heteromeric organic solute transporter, OSTα-OSTβ. In addition to the hepatocyte and enterocyte, subgroups of these bile acid transporters are expressed by the biliary, renal, and colonic epithelium where they contribute to maintaining bile acid homeostasis and play important cytoprotective roles. This article will review our current understanding of the physiological role and regulation of these important carriers. PMID:19498215

  18. Altered Cultivar Resistance of Kimchi Cabbage Seedlings Mediated by Salicylic Acid, Jasmonic Acid and Ethylene

    PubMed Central

    Lee, Young Hee; Kim, Sang Hee; Yun, Byung-Wook; Hong, Jeum Kyu

    2014-01-01

    Two cultivars Buram-3-ho (susceptible) and CR-Hagwang (moderate resistant) of kimchi cabbage seedlings showed differential defense responses to anthracnose (Colletotrichum higginsianum), black spot (Alternaria brassicicola) and black rot (Xanthomonas campestris pv. campestris, Xcc) diseases in our previous study. Defense-related hormones salicylic acid (SA), jasmonic acid (JA) and ethylene led to different transcriptional regulation of pathogenesis-related (PR) gene expression in both cultivars. In this study, exogenous application of SA suppressed basal defenses to C. higginsianum in the 1st leaves of the susceptible cultivar and cultivar resistance of the 2nd leaves of the resistant cultivar. SA also enhanced susceptibility of the susceptible cultivar to A. brassicicola. By contrast, SA elevated disease resistance to Xcc in the resistant cultivar, but not in the susceptible cultivar. Methyl jasmonate (MJ) treatment did not affect the disease resistance to C. higginsianum and Xcc in either cultivar, but it compromised the disease resistance to A. brassicicola in the resistant cultivar. Treatment with 1-aminocyclopropane-1-carboxylic acid (ACC) ethylene precursor did not change resistance of the either cultivar to C. higginsianum and Xcc. Effect of ACC pretreatment on the resistance to A. brassicicola was not distinguished between susceptible and resistant cultivars, because cultivar resistance of the resistant cultivar was lost by prolonged moist dark conditions. Taken together, exogenously applied SA, JA and ethylene altered defense signaling crosstalk to three diseases of anthracnose, black spot and black rot in a cultivar-dependent manner. PMID:25289020

  19. Comparative Indole-3-Acetic Acid Levels in the Slender Pea and Other Pea Phenotypes 1

    PubMed Central

    Law, David M.; Davies, Peter J.

    1990-01-01

    Free indole-3-acetic acid levels were measured by gas chromatography-mass spectrometry in three ultra-tall `slender' Pisum sativum L. lines differing in gibberellin content. Measurements were made for apices and stem elongation zones of light-grown plants and values were compared with wild-type, dwarf, and nana phenotypes in which internode length is genetically regulated, purportedly via the gibberellin level. Indole-3-acetic acid levels of growing stems paralleled growth rates in all lines, and were high in all three slender genotypes. Growth was inhibited by p-chlorophenoxyisobutyric acid, demonstrating the requirement of auxin activity for stem elongation, and also by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. It is concluded that the slender phenotype may arise from constant activation of a gibberellin receptor or transduction chain event leading directly or indirectly to elevated levels of indole-3-acetic acid, and that increased indole-3-acetic acid levels are a significant factor in the promotion of stem elongation. PMID:16667653

  20. Abscisic acid inhibits root growth in Arabidopsis through ethylene biosynthesis.

    PubMed

    Luo, Xingju; Chen, Zhizhong; Gao, Junping; Gong, Zhizhong

    2014-07-01

    When first discovered in 1963, abscisic acid (ABA) was called abscisin II because it promotes abscission. Later, researchers found that ABA accelerates abscission via ethylene. In Arabidopsis, previous studies have shown that high concentrations of ABA inhibit root growth through ethylene signaling but not ethylene production. In the present study in Arabidopsis, we found that ABA inhibits root growth by promoting ethylene biosynthesis. The ethylene biosynthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine reduces ABA inhibition of root growth, and multiple mutants of ACS (1-aminocyclopropane-1-carboxylate synthase) are more resistant to ABA in terms of root growth than the wild-type is. Two ABA-activated calcium-dependent protein kinases, CPK4 and CPK11, phosphorylate the C-terminus of ACS6 and increase the stability of ACS6 in ethylene biosynthesis. Plants expressing an ACS6 mutant that mimics the phosphorylated form of ACS6 produce more ethylene than the wild-type. Our results reveal an important mechanism by which ABA promotes ethylene production. This mechanism may be highly conserved among higher plants.

  1. Ethylene limits abscisic acid- or soil drying-induced stomatal closure in aged wheat leaves.

    PubMed

    Chen, Lin; Dodd, Ian C; Davies, William J; Wilkinson, Sally

    2013-10-01

    The mechanism of age-induced decreased stomatal sensitivity to abscisic acid (ABA) and soil drying has been explored here. Older, fully expanded leaves partly lost their ability to close stomata in response to foliar ABA sprays, and soil drying which stimulated endogenous ABA production, while young fully expanded leaves closed their stomata more fully. However, ABA- or soil drying-induced stomatal closure of older leaves was partly restored by pretreating plants with 1-methylcyclopropene (1-MCP), which can antagonize ethylene receptors, or by inoculating soil around the roots with the rhizobacterium Variovorax paradoxus 5C-2, which contains 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase. ACC (the immediate biosynthetic precursor of ethylene) sprays revealed higher sensitivity of stomata to ethylene in older leaves than younger leaves, despite no differences in endogenous ACC concentrations or ethylene emission. Taken together, these results indicate that the relative insensitivity of stomatal closure to ABA and soil drying in older leaves is likely due to altered stomatal sensitivity to ethylene, rather than ethylene production. To our knowledge, this is the first study to mechanistically explain diminished stomatal responses to soil moisture deficit in older leaves, and the associated reduction in leaf water-use efficiency.

  2. TGA Transcription Factors Activate the Salicylic Acid-Suppressible Branch of the Ethylene-Induced Defense Program by Regulating ORA59 Expression.

    PubMed

    Zander, Mark; Thurow, Corinna; Gatz, Christiane

    2014-07-01

    Salicylic acid (SA), a hormone essential for defense against biotrophic pathogens, triggers increased susceptibility of plants against necrotrophic attackers by suppressing the jasmonic acid-ethylene (ET) defense response. Here, we show that this disease-promoting SA effect is abolished in plants lacking the three related TGACG sequence-specific binding proteins TGA2, TGA5, and TGA6 (class II TGAs). After treatment of plants with the ET precursor 1-aminocyclopropane-1-carboxylic acid (ACC), activation of all those genes that are suppressed by SA depended on class II TGAs. Rather than TGA binding sites, GCC-box motifs were significantly enriched in the corresponding promoters. GCC-box motifs are recognized by members of the superfamily of APETALA2/ETHYLENE RESPONSE FACTORs (ERFs). Of 11 activating ACC-induced APETALA2/ERFs, only ORA59 (for OCTADECANOID-RESPONSIVE ARABIDOPSIS APETALA2/ETHYLENE RESPONSE FACTOR domain protein59) and ERF96 were strongly suppressed by SA. ORA59 is the master regulator of the jasmonic acid-ET-induced defense program. ORA59 transcript levels do not reach maximal levels in the tga2 tga5 tga6 triple mutant, and this residual activity cannot be suppressed by SA. The ORA59 promoter contains an essential TGA binding site and is a direct target of class II TGAs as revealed by chromatin immunoprecipitation experiments. We suggest that class II TGAs at the ORA59 promoter constitute an important regulatory hub for the activation and SA suppression of ACC-induced genes.

  3. TGA Transcription Factors Activate the Salicylic Acid-Suppressible Branch of the Ethylene-Induced Defense Program by Regulating ORA59 Expression1[C][W

    PubMed Central

    Zander, Mark; Thurow, Corinna; Gatz, Christiane

    2014-01-01

    Salicylic acid (SA), a hormone essential for defense against biotrophic pathogens, triggers increased susceptibility of plants against necrotrophic attackers by suppressing the jasmonic acid-ethylene (ET) defense response. Here, we show that this disease-promoting SA effect is abolished in plants lacking the three related TGACG sequence-specific binding proteins TGA2, TGA5, and TGA6 (class II TGAs). After treatment of plants with the ET precursor 1-aminocyclopropane-1-carboxylic acid (ACC), activation of all those genes that are suppressed by SA depended on class II TGAs. Rather than TGA binding sites, GCC-box motifs were significantly enriched in the corresponding promoters. GCC-box motifs are recognized by members of the superfamily of APETALA2/ETHYLENE RESPONSE FACTORs (ERFs). Of 11 activating ACC-induced APETALA2/ERFs, only ORA59 (for OCTADECANOID-RESPONSIVE ARABIDOPSIS APETALA2/ETHYLENE RESPONSE FACTOR domain protein59) and ERF96 were strongly suppressed by SA. ORA59 is the master regulator of the jasmonic acid-ET-induced defense program. ORA59 transcript levels do not reach maximal levels in the tga2 tga5 tga6 triple mutant, and this residual activity cannot be suppressed by SA. The ORA59 promoter contains an essential TGA binding site and is a direct target of class II TGAs as revealed by chromatin immunoprecipitation experiments. We suggest that class II TGAs at the ORA59 promoter constitute an important regulatory hub for the activation and SA suppression of ACC-induced genes. PMID:24989234

  4. Ethylene interacts with abscisic acid to regulate endosperm rupture during germination: a comparative approach using Lepidium sativum and Arabidopsis thaliana.

    PubMed

    Linkies, Ada; Müller, Kerstin; Morris, Karl; Turecková, Veronika; Wenk, Meike; Cadman, Cassandra S C; Corbineau, Françoise; Strnad, Miroslav; Lynn, James R; Finch-Savage, William E; Leubner-Metzger, Gerhard

    2009-12-01

    The micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae.

  5. Ethylene Interacts with Abscisic Acid to Regulate Endosperm Rupture during Germination: A Comparative Approach Using Lepidium sativum and Arabidopsis thaliana[W][OA

    PubMed Central

    Linkies, Ada; Müller, Kerstin; Morris, Karl; Turečková, Veronika; Wenk, Meike; Cadman, Cassandra S.C.; Corbineau, Françoise; Strnad, Miroslav; Lynn, James R.; Finch-Savage, William E.; Leubner-Metzger, Gerhard

    2009-01-01

    The micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae. PMID:20023197

  6. Determination and stereochemistry of proteinogenic and non-proteinogenic amino acids in Saudi Arabian date fruits.

    PubMed

    Ali, Hatem Salama Mohamed; Alhaj, Omar Amin; Al-Khalifa, Abdulrahman Saleh; Brückner, Hans

    2014-09-01

    Whereas an abundance of literature is available on the occurrence of common proteinogenic amino acids (AAs) in edible fruits of the date palm (Phoenix dactylifera L.), recent reports on non-proteinogenic (non-coded) AAs and amino components are scarce. With emphasis on these components we have analyzed total hydrolysates of twelve cultivars of date fruits using automated ion-exchange chromatography, HPLC employing a fluorescent aminoquinolyl label, and GC-MS of total hydrolysates using the chiral stationary phases Chirasil(®)-L-Val and Lipodex(®) E. Besides common proteinogenic AAs, relatively large amounts of the following non-proteinogenic amino acids were detected: (2S,5R)-5-hydroxypipecolic acid (1.4-4.0 g/kg dry matter, DM), 1-aminocyclopropane-1-carboxylic acid (1.3-2.6 g/kg DM), γ-amino-n-butyric acid (0.5-1.2 g/kg DM), (2S,4R)-4-hydroxyproline (130-230 mg/kg DM), L-pipecolic acid (40-140 mg/kg DM), and 2-aminoethanol (40-160 mg/kg DM) as well as low or trace amounts (<70 mg/kg DM) of L-ornithine, 5-hydroxylysine, β-alanine, and in some samples (<20 mg/kg DM) of (S)-β-aminoisobutyric acid and (<10 mg/kg DM) L-allo-isoleucine. In one date fruit, traces of α-aminoadipic acid could be determined. Enantiomeric analysis of 6 M DCl/D2O hydrolysates of AAs using chiral capillary gas chromatography-mass spectrometry revealed the presence of very low amounts of D-Ala, D-Asp, D-Glu, D-Ser and D-Phe (1.2-0.4%, relative to the corresponding L-enantiomers), besides traces (0.2-1%) of other D-AAs. The possible relevance of non-proteinogenic amino acids in date fruits is briefly addressed.

  7. Acid rain: chemistry and transport.

    PubMed

    Irwin, J G; Williams, M L

    1988-01-01

    This review describes the more important features of the emission, chemistry, transport and deposition of pollutants involved in acid deposition. Global emissions, both natural and man-made, of sulphur and nitrogen oxides are discussed and examples of spatial distributions and trends over the last century presented. The more significant chemical and physical processes involved in the transformation of the primary emissions into their acidic end products are described, including a summary of the approximate timescales of the processes involved. Measurements and modelled calculations of spatial and temporal patterns in the deposition of acidic pollutants by both wet and dry pathways are presented.

  8. Uric acid transport and disease

    PubMed Central

    So, Alexander; Thorens, Bernard

    2010-01-01

    Uric acid is the metabolic end product of purine metabolism in humans. It has antioxidant properties that may be protective but can also be pro-oxidant, depending on its chemical microenvironment. Hyperuricemia predisposes to disease through the formation of urate crystals that cause gout, but hyperuricemia, independent of crystal formation, has also been linked with hypertension, atherosclerosis, insulin resistance, and diabetes. We discuss here the biology of urate metabolism and its role in disease. We also cover the genetics of urate transport, including URAT1, and recent studies identifying SLC2A9, which encodes the glucose transporter family isoform Glut9, as a major determinant of plasma uric acid levels and of gout development. PMID:20516647

  9. Draft Genome Sequence of Endophytic Bacterium Enterobacter asburiae PDA134, Isolated from Date Palm (Phoenix dactylifera L.) Roots.

    PubMed

    Yaish, Mahmoud W

    2016-01-01

    In this report, a draft of the Enterobacter asburiae strain PDA134 genome was sequenced. This bacterial strain was isolated from the root tissue of a date palm, where it has the ability to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and indole-3-acetic acid (IAA) under salinity stress. PMID:27540071

  10. Draft Genome Sequence of Endophytic Bacterium Enterobacter asburiae PDA134, Isolated from Date Palm (Phoenix dactylifera L.) Roots

    PubMed Central

    2016-01-01

    In this report, a draft of the Enterobacter asburiae strain PDA134 genome was sequenced. This bacterial strain was isolated from the root tissue of a date palm, where it has the ability to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and indole-3-acetic acid (IAA) under salinity stress. PMID:27540071

  11. The formation of ACC and competition between polyamines and ethylene for SAM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ethylene biosynthesis involves the conversion of S-adenosylmethionine (SAM) to 1-aminocyclopropane-1-carboxylic acid (ACC) by ACC synthase (ACS). ACC is then converted to ethylene. The genes that encode enzymes in this pathway all belong to a family of genes. Differential transcriptional regulation ...

  12. Genome Sequence of the Banana Plant Growth-Promoting Rhizobacterium Pseudomonas fluorescens PS006.

    PubMed

    Gamez, Rocío M; Rodríguez, Fernando; Ramírez, Sandra; Gómez, Yolanda; Agarwala, Richa; Landsman, David; Mariño-Ramírez, Leonardo

    2016-05-05

    Pseudomonas fluorescens is a well-known plant growth-promoting rhizobacterium (PGPR). We report here the first whole-genome sequence of PGPR P. fluorescens evaluated in Colombian banana plants. The genome sequences contains genes involved in plant growth and defense, including bacteriocins, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and genes that provide resistance to toxic compounds.

  13. Genome Sequence of the Banana Plant Growth-Promoting Rhizobacterium Pseudomonas fluorescens PS006.

    PubMed

    Gamez, Rocío M; Rodríguez, Fernando; Ramírez, Sandra; Gómez, Yolanda; Agarwala, Richa; Landsman, David; Mariño-Ramírez, Leonardo

    2016-01-01

    Pseudomonas fluorescens is a well-known plant growth-promoting rhizobacterium (PGPR). We report here the first whole-genome sequence of PGPR P. fluorescens evaluated in Colombian banana plants. The genome sequences contains genes involved in plant growth and defense, including bacteriocins, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and genes that provide resistance to toxic compounds. PMID:27151797

  14. Transepithelial transport of ferulic acid by monocarboxylic acid transporter in Caco-2 cell monolayers.

    PubMed

    Konishi, Yutaka; Shimizu, Makoto

    2003-04-01

    Our previous study (Biosci. Biotechnol. Biochem., 66, 2449-2457 (2002)), suggested that ferulic acid was transported via a monocarboxylic acid transporter (MCT). Transepithelial transport of ferulic acid was examined in this study by directly measuring the rate of its transport across Caco-2 cell monolayers. Ferulic acid transport was dependent on pH, and in a vectorical way in the apical-basolateral direction. The permeation of ferulic acid was concentration-dependent and saturable; the Michaelis constant was 16.2 mM and the maximum velocity was 220.4 nmol min-1 (mg protein)-1. Various substrates for MCTs, such as benzoic acid and acetic acid, strongly inhibited the permeation of ferulic acid, demonstrating that ferulic acid is obviously transported by MCT. Antioxidative phenolic acid compounds from dietary sources like ferulic acid would be recognized and transported by MCT by intestinal absorption.

  15. Foliar Abscisic Acid-To-Ethylene Accumulation and Response Regulate Shoot Growth Sensitivity to Mild Drought in Wheat

    PubMed Central

    Valluru, Ravi; Davies, William J.; Reynolds, Matthew P.; Dodd, Ian C.

    2016-01-01

    Although, plant hormones play an important role in adjusting growth in response to environmental perturbation, the relative contributions of abscisic acid (ABA) and ethylene remain elusive. Using six spring wheat genotypes differing for stress tolerance, we show that young seedlings of the drought-tolerant (DT) group maintained or increased shoot dry weight (SDW) while the drought-susceptible (DS) group decreased SDW in response to mild drought. Both the DT and DS groups increased endogenous ABA and ethylene concentrations under mild drought compared to control. The DT and DS groups exhibited different SDW response trends, whereby the DS group decreased while the DT group increased SDW, to increased concentrations of ABA and ethylene under mild drought, although both groups decreased ABA/ethylene ratio under mild drought albeit at different levels. We concluded that SDW of the DT and DS groups might be distinctly regulated by specific ABA:ethylene ratio. Further, a foliar-spray of low concentrations (0.1 μM) of ABA increased shoot relative growth rate (RGR) in the DS group while ACC (1-aminocyclopropane-1-carboxylic acid, ethylene precursor) spray increased RGR in both groups compared to control. Furthermore, the DT group accumulated a significantly higher galactose while a significantly lower maltose in the shoot compared to the DS group. Taken all together, these results suggest an impact of ABA, ethylene, and ABA:ethylene ratio on SDW of wheat seedlings that may partly underlie a genotypic variability of different shoot growth sensitivities to drought among crop species under field conditions. We propose that phenotyping based on hormone accumulation, response and hormonal ratio would be a viable, rapid, and an early–stage selection tool aiding genotype selection for stress tolerance. PMID:27148292

  16. Methylarsonous acid transport by aquaglyceroporins.

    PubMed

    Liu, Zijuan; Styblo, Miroslav; Rosen, Barry P

    2006-04-01

    Many mammals methylate trivalent inorganic arsenic in liver to species that are released into the bloodstream and excreted in urine and feces. This study addresses how methylated arsenicals pass through cell membranes. We have previously shown that aquaglyceroporin channels, including Escherichia coli GlpF, Saccharomyces cerevisiae Fps1p, AQP7, and AQP9 from rat and human, conduct trivalent inorganic arsenic [As(III)] as arsenic trioxide, the protonated form of arsenite. One of the initial products of As(III) methylation is methylarsonous acid [MAs(III)], which is considerably more toxic than inorganic As(III). In this study, we investigated the ability of GlpF, Fps1p, and AQP9 to facilitate movement of MAs(III) and found that rat aquaglyceroporin conducted MAs(III) at a higher rate than the yeast homologue. In addition, rat AQP9 facilitates MAs(III) at a higher rate than As(III). These results demonstrate that aquaglyceroporins differ both in selectivity for and in transport rates of trivalent arsenicals. In this study, the requirement of AQP9 residues Phe-64 and Arg-219 for MAs(III) movement was examined. A hydrophobic residue at position 64 is not required for MAs(III) transport, whereas an arginine at residue 219 may be required. This is similar to that found for As(III), suggesting that As(III) and MAs(III) use the same translocation pathway in AQP9. Identification of MAs(III) as an AQP9 substrate is an important step in understanding physiologic responses to arsenic in mammals, including humans.

  17. Spatio-temporal expression of patatin-like lipid acyl hydrolases and accumulation of jasmonates in elicitor-treated tobacco leaves are not affected by endogenous levels of salicylic acid.

    PubMed

    Dhondt, Sandrine; Gouzerh, Guillaume; Müller, Axel; Legrand, Michel; Heitz, Thierry

    2002-12-01

    We have previously isolated three tobacco genes (NtPat) encoding patatin-like proteins, getting rapidly induced during the hypersensitive response (HR) to tobacco mosaic virus, in advance to jasmonate accumulation. NtPAT enzymes are lipid acyl hydrolases that display high phospholipase A2 (PLA2) activity and may mobilize fatty acid precursors of oxylipins. Here, we performed a detailed study of NtPat gene regulation under various biotic and abiotic stresses. PLA2 activity was poorly induced in response to drought, wounding, reactive oxygen intermediates, salicylic acid (SA) or methyl-jasmonate (MJ) whereas the ethylene (ET) precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), provoked a moderate induction. In contrast, PLA2 activity was strongly induced when ACC was combined with MJ, and in response to the bacterium Erwinia carotovora or to the fungus Botrytis cinerea, as well as to treatment with beta-megaspermin, a cell death-inducing protein elicitor. A simplified system based on the infiltration of beta-megaspermin into leaves was used to dissect the spatio-temporal activation of PLA2 activity with regards to the accumulation of jasmonates and to the influence of endogenous SA. NtPat-encoded PLA2 activity was rapidly induced in the infiltrated zone before the appearance of cell death and with some delay in the surrounding living cells. A massive accumulation of 12-oxo-phytodienoic and jasmonic acids occurred in the elicitor-infiltrated zone, but only low levels were detectable outside this area. A similar picture was found in SA-deficient plants, showing that in tobacco, accumulation of jasmonates is not affected by the concomitant HR-induced build-up of endogenous SA. Finally, ET-insensitive plants showed a weakened induction of PLA2 activity outside the elicitor-infiltrated tissue.

  18. After-ripening induced transcriptional changes of hormonal genes in wheat seeds: the cases of brassinosteroids, ethylene, cytokinin and salicylic acid.

    PubMed

    Chitnis, Vijaya R; Gao, Feng; Yao, Zhen; Jordan, Mark C; Park, Seokhoon; Ayele, Belay T

    2014-01-01

    Maintenance and release of seed dormancy is regulated by plant hormones; their levels and seed sensitivity being the critical factors. This study reports transcriptional regulation of brassinosteroids (BR), ethylene (ET), cytokinin (CK) and salicylic acid (SA) related wheat genes by after-ripening, a period of dry storage that decays dormancy. Changes in the expression of hormonal genes due to seed after-ripening did not occur in the anhydrobiotic state but rather in the hydrated state. After-ripening induced dormancy decay appears to be associated with imbibition mediated increase in the synthesis and signalling of BR, via transcriptional activation of de-etiolated2, dwarf4 and brassinosteroid signaling kinase, and repression of brassinosteroid insensitive 2. Our analysis is also suggestive of the significance of increased ET production, as reflected by enhanced transcription of 1-aminocyclopropane-1-carboxylic acid oxidase in after-ripened seeds, and tight regulation of seed response to ET in regulating dormancy decay. Differential transcriptions of lonely guy, zeatin O-glucosyltransferases and cytokinin oxidases, and pseudo-response regulator between dormant and after-ripened seeds implicate CK in the regulation of seed dormancy in wheat. Our analysis also reflects the association of dormancy decay in wheat with seed SA level and NPR independent SA signaling that appear to be regulated transcriptionally by phenylalanine ammonia lyase, and whirly and suppressor of npr1 inducible1 genes, respectively. Co-expression clustering of the hormonal genes implies the significance of synergistic and antagonistic interaction between the different plant hormones in regulating wheat seed dormancy. These results contribute to further our understanding of the molecular features controlling seed dormancy in wheat.

  19. 2,4-dichlorophenoxyacetic acid-induced leaf senescence in mung bean (Vigna radiata L. Wilczek) and senescence inhibition by co-treatment with silver nanoparticles.

    PubMed

    Karuppanapandian, Thirupathi; Wang, Hong Wei; Prabakaran, Natarajan; Jeyalakshmi, Kandhavelu; Kwon, Mi; Manoharan, Kumariah; Kim, Wook

    2011-02-01

    Leaf senescence induced by 2,4-dichlorophenoxyacetic acid (2,4-D) and senescence inhibition caused by supplementation with silver (Ag(+)) ions in the form of silver nitrate (AgNO(3)) or silver nanoparticles (AgNPs) were investigated in 8-day-old mung bean (Vigna radiata L. Wilczek) seedlings. Inhibition of root and shoot elongation were observed in mung bean seedlings treated with 500μM 2,4-D. Concomitantly, the activity of 1-aminocyclopropane-1-carboxylic acid synthase was significantly induced in leaf tissue. Leaf senescence induced by 2,4-D was closely associated with lipid peroxidation as well as increased levels of cytotoxic hydrogen peroxide (H(2)O(2)) and superoxide radicals (O(2)(·-)). Despite decreased catalase activity, the activities of peroxidase, superoxide dismutase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase were increased during 2,4-D-induced leaf senescence. Further, the levels of reduced ascorbate, oxidized ascorbate, and reduced glutathione were markedly decreased, whereas the level of oxidized glutathione increased. 2,4-D-induced leaf senescence in mung bean was accompanied by an increase in positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, nuclear DNA fragmentation, and the activity of a 15-kDa Ca(2+)-dependent DNase. Supplementation with 100μM AgNO(3) or AgNPs inhibited 2,4-D-induced leaf senescence. The present results suggest that increased oxidative stress (O(2)(·-) and H(2)O(2)) led to senescence in mung bean leaves. Furthermore, significantly induced antioxidative enzymes are not sufficient to protect mung bean cells from 2,4-D-induced harmful ROS.

  20. Ethylene Upregulates Auxin Biosynthesis in Arabidopsis Seedlings to Enhance Inhibition of Root Cell Elongation[W

    PubMed Central

    Swarup, Ranjan; Perry, Paula; Hagenbeek, Dik; Van Der Straeten, Dominique; Beemster, Gerrit T.S.; Sandberg, Göran; Bhalerao, Rishikesh; Ljung, Karin; Bennett, Malcolm J.

    2007-01-01

    Ethylene represents an important regulatory signal for root development. Genetic studies in Arabidopsis thaliana have demonstrated that ethylene inhibition of root growth involves another hormone signal, auxin. This study investigated why auxin was required by ethylene to regulate root growth. We initially observed that ethylene positively controls auxin biosynthesis in the root apex. We subsequently demonstrated that ethylene-regulated root growth is dependent on (1) the transport of auxin from the root apex via the lateral root cap and (2) auxin responses occurring in multiple elongation zone tissues. Detailed growth studies revealed that the ability of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid to inhibit root cell elongation was significantly enhanced in the presence of auxin. We conclude that by upregulating auxin biosynthesis, ethylene facilitates its ability to inhibit root cell expansion. PMID:17630275

  1. Expression of the patatin-related phospholipase A gene AtPLA IIA in Arabidopsis thaliana is up-regulated by salicylic acid, wounding, ethylene, and iron and phosphate deficiency.

    PubMed

    Rietz, Steffen; Holk, André; Scherer, Günther F E

    2004-09-01

    In Arabidopsis thaliana (L.) Heynh., the cytosolic, patatin-related phospholipase A enzymes comprise a family of ten genes designated AtPLAs thought to be involved in auxin and pathogen signalling [A. Holk et al. (2002) Plant Physiol 130:90-101]. One of these, AtPLA IIA, is investigated here by studying its transcriptional regulation through transgenic Arabidopsis plants containing the AtPLA IIA promoter (PIIA) fused to the beta-glucuronidase (GUS) gene. GUS activity appeared in leaves at 10-12 days and became increasingly stronger with age in all leaves. From the same age on, strong GUS activity was visible in the basal stipules of the rosette leaves. PIIA-dependent GUS activity was found in the older parts of the primary root (from 10 days on) and, later in development, in older parts of side roots, and the root cap. No GUS activity was detected in flower organs. PIIA-dependent GUS expression in 12-day-old plants was up-regulated after treatment by salicylic acid, Bion, wounding, 1-aminocyclopropane-1-carboxylic acid (ACC) and jasmonic acid. When transgenic PIIA:: uidA plants were grown devoid of iron, 9-day-old plants exhibited increased GUS activity in the leaves and, when devoid of phosphate, 11-day-old plants had increased GUS activity in the roots. In conclusion, this member of the patatin-related phospholipase A gene family showed properties of a defence and iron-stress and phosphate-stress gene, being transcriptionally up-regulated within hours or days.

  2. Ascorbic acid transport into cultured pituitary cells

    SciTech Connect

    Cullen, E.I.; May, V.; Eipper, R.A.

    1986-05-01

    An amidating enzyme designated peptidyl-glycine ..cap alpha..-amidating monooxygenase (PAM) has been studied in a variety of tissues and is dependent on molecular oxygen and stimulated by copper and ascorbic acid. To continue investigating the relationship among cellular ascorbic acid concentrations, amidating ability, and PAM activity, the authors studied ascorbic acid transport in three cell preparations that contain PAM and produce amidated peptides: primary cultures of rat anterior and intermediate pituitary and mouse AtT-20 tumor cells. When incubated in 50 ..mu..M (/sup 14/C)ascorbic acid all three cell preparations concentrated ascorbic acid 20- to 40-fold, producing intracellular ascorbate concentrations of 1 to 2 mM, based on experimentally determined cell volumes. All three cell preparations displayed saturable ascorbic acid uptake with half-maximal initial rates occurring between 9 and 18 ..mu..M ascorbate. Replacing NaCl in the uptake buffer with choline chloride significantly diminished ascorbate uptake in all three preparations. Ascorbic acid efflux from these cells was slow, displaying half-lives of 7 hours. Unlike systems that transport dehydroascorbic acid, the transport system for ascorbic acid in these cells was not inhibited by glucose. Thus, ascorbate is transported into pituitary cells by a sodium-dependent, active transport system.

  3. Role of fatty acid transporters in epidermis

    PubMed Central

    Miner, Jeffrey H; Jahnsen, Frode

    2011-01-01

    Skin epidermis is an active site of lipid synthesis. The intercellular lipids of human stratum corneum (SC) are unique in composition and quite different from the lipids found in most biological membranes. The three major lipids in the SC are free fatty acids, cholesterol and ceramides. Fatty acids can be synthesized by keratinocytes de novo and, in addition, need to be taken up from the circulation. The latter process has been shown to be protein mediated, and several fatty acid transporters are expressed in skin. Recent studies of transgenic and knockout animal models for fatty acid transporters and the identification of fatty acid transport protein 4 (FATP4 or SLC27A4) mutations as causative for Ichthyosis Prematurity Syndrome highlight the vital roles of fatty acid transport and metabolism in skin homeostasis. This review provides an overview of our current understanding of the role of fatty acids and their transporters in cutaneous biology, including their involvement in epidermal barrier generation and skin inflammation. PMID:21695012

  4. Quinone-amino acid conjugates targeting Leishmania amino acid transporters.

    PubMed

    Prati, Federica; Goldman-Pinkovich, Adele; Lizzi, Federica; Belluti, Federica; Koren, Roni; Zilberstein, Dan; Bolognesi, Maria Laura

    2014-01-01

    The aim of the present study was to investigate the feasibility of targeting Leishmania transporters via appropriately designed chemical probes. Leishmania donovani, the parasite that causes visceral leishmaniasis, is auxotrophic for arginine and lysine and has specific transporters (LdAAP3 and LdAAP7) to import these nutrients. Probes 1-15 were originated by conjugating cytotoxic quinone fragments (II and III) with amino acids (i.e. arginine and lysine) by means of an amide linkage. The toxicity of the synthesized conjugates against Leishmania extracellular (promastigotes) and intracellular (amastigotes) forms was investigated, as well their inhibition of the relevant amino acid transporters. We observed that some conjugates indeed displayed toxicity against the parasites; in particular, 7 was identified as the most potent derivative (at concentrations of 1 µg/mL and 2.5 µg/mL residual cell viability was reduced to 15% and 48% in promastigotes and amastigotes, respectively). Notably, 6, while retaining the cytotoxic activity of quinone II, displayed no toxicity against mammalian THP1 cells. Transport assays indicated that the novel conjugates inhibited transport activity of lysine, arginine and proline transporters. Furthermore, our analyses suggested that the toxic conjugates might be translocated by the transporters into the cells. The non-toxic probes that inhibited transport competed with the natural substrates for binding to the transporters without being translocated. Thus, it is likely that 6, by exploiting amino acid transporters, can selectively deliver its toxic effects to Leishmania cells. This work provides the first evidence that amino acid transporters of the human pathogen Leishmania might be modulated by small molecules, and warrants their further investigation from drug discovery and chemical biology perspectives. PMID:25254495

  5. Identification of a novel system L amino acid transporter structurally distinct from heterodimeric amino acid transporters.

    PubMed

    Babu, Ellappan; Kanai, Yoshikatsu; Chairoungdua, Arthit; Kim, Do Kyung; Iribe, Yuji; Tangtrongsup, Sahatchai; Jutabha, Promsuk; Li, Yuewei; Ahmed, Nesar; Sakamoto, Shinichi; Anzai, Naohiko; Nagamori, Seishi; Endou, Hitoshi

    2003-10-31

    A cDNA that encodes a novel Na+-independent neutral amino acid transporter was isolated from FLC4 human hepatocarcinoma cells by expression cloning. When expressed in Xenopus oocytes, the encoded protein designated LAT3 (L-type amino acid transporter 3) transported neutral amino acids such as l-leucine, l-isoleucine, l-valine, and l-phenylalanine. The LAT3-mediated transport was Na+-independent and inhibited by 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, consistent with the properties of system L. Distinct from already known system L transporters LAT1 and LAT2, which form heterodimeric complex with 4F2 heavy chain, LAT3 was functional by itself in Xenopus oocytes. The deduced amino acid sequence of LAT3 was identical to the gene product of POV1 reported as a prostate cancer-up-regulated gene whose function was not determined, whereas it did not exhibit significant similarity to already identified transporters. The Eadie-Hofstee plots of LAT3-mediated transport were curvilinear, whereas the low affinity component is predominant at physiological plasma amino acid concentration. In addition to amino acid substrates, LAT3 recognized amino acid alcohols. The transport of l-leucine was electroneutral and mediated by a facilitated diffusion. In contrast, l-leucinol, l-valinol, and l-phenylalaninol, which have a net positive charge induced inward currents under voltage clamp, suggesting these compounds are transported by LAT3. LAT3-mediated transport was inhibited by the pretreatment with N-ethylmaleimide, consistent with the property of system L2 originally characterized in hepatocyte primary culture. Based on the substrate selectivity, affinity, and N-ethylmaleimide sensitivity, LAT3 is proposed to be a transporter subserving system L2. LAT3 should denote a new family of organic solute transporters. PMID:12930836

  6. Intestinal transport and metabolism of bile acids

    PubMed Central

    Dawson, Paul A.; Karpen, Saul J.

    2015-01-01

    In addition to their classical roles as detergents to aid in the process of digestion, bile acids have been identified as important signaling molecules that function through various nuclear and G protein-coupled receptors to regulate a myriad of cellular and molecular functions across both metabolic and nonmetabolic pathways. Signaling via these pathways will vary depending on the tissue and the concentration and chemical structure of the bile acid species. Important determinants of the size and composition of the bile acid pool are their efficient enterohepatic recirculation, their host and microbial metabolism, and the homeostatic feedback mechanisms connecting hepatocytes, enterocytes, and the luminal microbiota. This review focuses on the mammalian intestine, discussing the physiology of bile acid transport, the metabolism of bile acids in the gut, and new developments in our understanding of how intestinal metabolism, particularly by the gut microbiota, affects bile acid signaling. PMID:25210150

  7. Role of amino acid transporters in amino acid sensing1234

    PubMed Central

    2014-01-01

    Amino acid (AA) transporters may act as sensors, as well as carriers, of tissue nutrient supplies. This review considers recent advances in our understanding of the AA-sensing functions of AA transporters in both epithelial and nonepithelial cells. These transporters mediate AA exchanges between extracellular and intracellular fluid compartments, delivering substrates to intracellular AA sensors. AA transporters on endosomal (eg, lysosomal) membranes may themselves function as intracellular AA sensors. AA transporters at the cell surface, particularly those for large neutral AAs such as leucine, interact functionally with intracellular nutrient-signaling pathways that regulate metabolism: for example, the mammalian target of rapamycin complex 1 (mTORC1) pathway, which promotes cell growth, and the general control non-derepressible (GCN) pathway, which is activated by AA starvation. Under some circumstances, upregulation of AA transporter expression [notably a leucine transporter, solute carrier 7A5 (SLC7A5)] is required to initiate AA-dependent activation of the mTORC1 pathway. Certain AA transporters may have dual receptor-transporter functions, operating as “transceptors” to sense extracellular (or intracellular) AA availability upstream of intracellular signaling pathways. New opportunities for nutritional therapy may include targeting of AA transporters (or mechanisms that upregulate their expression) to promote protein-anabolic signals for retention or recovery of lean tissue mass. PMID:24284439

  8. Modeling Electrical Transport through Nucleic Acids

    NASA Astrophysics Data System (ADS)

    Qi, Jianqing

    Nucleic acids play a vital role in many biological systems and activities. In recent years, engineers and scientists have been interested in studying their electrical properties. The motivation for these studies stems from the following facts: (1) the bases, which form the building blocks of nucleic acids, have unique ionization potentials. Further, nucleic acids are one of the few nanomaterials that can be reproducibly manufactured with a high degree of accuracy (though admittedly their placement at desired locations remains a challenge). As a result, designed strands with specific sequences may offer unique device properties; (2) electrical methods offer potential for sequencing nucleic acids based on a single molecule; (3) electrical methods for disease detection based on the current flowing through nucleic acids are beginning to be demonstrated. While experiments in the above mentioned areas is promising, a deeper understanding of the electrical current flow through the nucleic acids needs to be developed. The modeling of current flowing in these molecules is complex because: (1) they are based on atomic scale contacts between nucleic acids and metal, which cannot be reproducibly built; (2) the conductivity of nucleic acids is easily influenced by the environment, which is constantly changing; and (3) the nucleic acids by themselves are floppy. This thesis focuses on the modeling of electrical transport through nucleic acids that are connected to two metal electrodes at nanoscale. We first develop a decoherent transport model for the double-stranded helix based on the Landauer-Buttiker framework. This model is rationalized by comparison with an experiment that measured the conductance of four different DNA strands. The developed model is then used to study the: (1) potential to make barriers and wells for quantum transport using specifically engineered sequences; (2) change in the electrical properties of a specific DNA strand with and without methylation; (3

  9. Portage transport of sulfanilamide and sulfanilic acid.

    PubMed

    Hwang, S Y; Berges, D A; Taggart, J J; Gilvarg, C

    1989-03-01

    Sulfanilic acid, in contrast to sulfanilamide, has poor in vitro antibacterial activity. Paradoxically, it has been shown to be a more effective inhibitor than sulfanilamide of dihydropteroic acid synthase. In order to circumvent the presumed permeability barrier to sulfanilic acid, advantage was taken of the technique of portage transport. Derivatives of the compound were prepared in which it was linked via its primary amino group to the alpha-carbon of glycine residues in di- and tripeptides. L-Alanyl-L-alanyl-L-2-[(4-sulfophenyl)amino]glycine proved to be 207 times more potent than sulfanilic acid and 8 times more active than either sulfanilamide or L-alanyl-L-alanyl-L-2-[[4-(aminosulfonyl)-phenyl]amino]glycine when tested against Escherichia coli. These findings confirm that the weak in vitro activity of sulfanilic acid is due to its limited ability to penetrate the bacterial membrane. They also emphasize the ability of portage transport to reveal therapeutic capability that had been attenuated by poor drug permeation.

  10. Reactive solute transport in acidic streams

    USGS Publications Warehouse

    Broshears, R.E.

    1996-01-01

    Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

  11. Abscisic acid transport in human erythrocytes.

    PubMed

    Vigliarolo, Tiziana; Guida, Lucrezia; Millo, Enrico; Fresia, Chiara; Turco, Emilia; De Flora, Antonio; Zocchi, Elena

    2015-05-22

    Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [(3)H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [(3)H]ABA and [(35)S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone.

  12. Differential expression of ethylene biosynthesis genes in drupelets and receptacle of raspberry (Rubus idaeus).

    PubMed

    Fuentes, Lida; Monsalve, Liliam; Morales-Quintana, Luis; Valdenegro, Mónika; Martínez, Juan-Pablo; Defilippi, Bruno G; González-Agüero, Mauricio

    2015-05-01

    Red Raspberry (Rubus idaeus) is traditionally classified as non-climacteric, and the role of ethylene in fruit ripening is not clear. The available information indicates that the receptacle, a modified stem that supports the drupelets, is involved in ethylene production of ripe fruits. In this study, we report receptacle-related ethylene biosynthesis during the ripening of fruits of cv. Heritage. In addition, the expression pattern of ethylene biosynthesis transcripts was evaluated during the ripening process. The major transcript levels of 1-aminocyclopropane-1-carboxylic acid synthase (RiACS1) and 1-aminocyclopropane-1-carboxylic acid oxidase (RiACO1) were concomitant with ethylene production, increased total soluble solids (TSS) and decreased titratable acidity (TA) and fruit firmness. Moreover, ethylene biosynthesis and transcript levels of RiACS1 and RiACO1 were higher in the receptacle, sustaining the receptacle's role as a source of ethylene in regulating the ripening of raspberry.

  13. Reciprocity between abscisic acid and ethylene at the onset of berry ripening and after harvest

    PubMed Central

    2010-01-01

    Background The ripening of grape berry is generally regulated by abscisic acid (ABA), and has no relationship with ethylene function. However, functional interaction and synergism between ABA and ethylene during the beginning of grape berry ripening (véraison) has been found recently. Results The expressions of VvNCED1 encoding 9-cis-epoxycarotenoid dioxygenase (NCED) and VvGT encoding ABA glucosyltransferase were all increased rapidly at the stage of véraison and reached the highest level at 9th week after full bloom. However, VvCYP1 encoding ABA 8'-hydroxylase and VvβG1 encoding berry β-glucosidase are different, whose expression peak appeared at the 10th week after full bloom and in especial VvβG1 remained at a high level till harvest. The VvACO1 encoding 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, the VvETR2 (ethylene response 2) and VvCTR1 (constitutive triple response 1) had a transient expression peak at pre-véraison, while the VvEIN4 (ethylene insensitive 4) expression gradually increased from the véraison to one week before harvest stage. The above mentioned changes happened again in the berry after harvest. At one week before véraison, double block treatment with NiCl2 plus 1-methylcyclopropene (1-MCP) not only inhibited the release of ethylene and the expression of related genes but also suppressed the transcription of VvNCED1 and the synthesis of ABA which all might result in inhibiting the fruit ripening onset. Treatment with ABA could relieve the double block and restore fruit ripening course. However, after harvest, double block treatment with NiCl2 plus 1-MCP could not suppress the transcription of VvNCED1 and the accumulation of ABA, and also could not inhibit the start of fruit senescence. Conclusion The trace endogenous ethylene induces the transcription of VvNCED1 and then the generation of ABA followed. Both ethylene and ABA are likely to be important and their interplaying may be required to start the process of berry ripening

  14. Boramino acid as a marker for amino acid transporters

    PubMed Central

    Liu, Zhibo; Chen, Haojun; Chen, Kai; Shao, Yihan; Kiesewetter, Dale O.; Niu, Gang; Chen, Xiaoyuan

    2015-01-01

    Amino acid transporters (AATs) are a series of integral channels for uphill cellular uptake of nutrients and neurotransmitters. Abnormal expression of AATs is often associated with cancer, addiction, and multiple mental diseases. Although methods to evaluate in vivo expression of AATs would be highly useful, efforts to develop them have been hampered by a lack of appropriate tracers. We describe a new class of AA mimics—boramino acids (BAAs)—that can serve as general imaging probes for AATs. The structure of a BAA is identical to that of the corresponding natural AA, except for an exotic replacement of the carboxylate with -BF3−. Cellular studies demonstrate strong AAT-mediated cell uptake, and animal studies show high tumor-specific accumulation, suggesting that BAAs hold great promise for the development of new imaging probes and smart AAT-targeting drugs. PMID:26601275

  15. Intestinal transport of sulfanilic acid in rats immunized with protein-sulfanilic acid conjugate.

    PubMed

    Yamamoto, A; Kawaratani, T; Kawashima, K; Hashida, M; Sezaki, H

    1990-07-01

    Intestinal transport of sulfanilic acid was examined by means of an in vitro everted sac technique in rats immunized with a bovine gamma-globulin-sulfanilic acid conjugate. At a low concentration of sulfanilic acid, the intestinal transport of sulfanilic acid was decreased in rats immunized with bovine gamma-globulin-sulfanilic acid conjugate. This phenomenon was dose dependent and antigen specific, since there was no difference in the transport of sulfanilic acid at a high concentration and of an unrelated hapten. These results suggested that parenteral immunization impaired not only the intestinal transport of macromolecular antigens, as previously shown, but also the transport of the low molecular weight hapten, sulfanilic acid.

  16. Complete Genome Sequence of the Rhizobacterium Pseudomonas trivialis Strain IHBB745 with Multiple Plant Growth-Promoting Activities and Tolerance to Desiccation and Alkalinity

    PubMed Central

    Swarnkar, Mohit Kumar; Vyas, Pratibha; Rahi, Praveen; Thakur, Rishu; Thakur, Namika; Singh, Anil Kumar

    2015-01-01

    The complete genome sequence of 6.45 Mb is reported here for Pseudomonas trivialis strain IHBB745 (MTCC 5336), which is an efficient, stress-tolerant, and broad-spectrum plant growth-promoting rhizobacterium. The gene-coding clusters predicted the genes for phosphate solubilization, siderophore production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole-3-acetic acid (IAA) production, and stress response. PMID:26337878

  17. Complete Genome Sequence of the Rhizobacterium Pseudomonas trivialis Strain IHBB745 with Multiple Plant Growth-Promoting Activities and Tolerance to Desiccation and Alkalinity.

    PubMed

    Gulati, Arvind; Swarnkar, Mohit Kumar; Vyas, Pratibha; Rahi, Praveen; Thakur, Rishu; Thakur, Namika; Singh, Anil Kumar

    2015-01-01

    The complete genome sequence of 6.45 Mb is reported here for Pseudomonas trivialis strain IHBB745 (MTCC 5336), which is an efficient, stress-tolerant, and broad-spectrum plant growth-promoting rhizobacterium. The gene-coding clusters predicted the genes for phosphate solubilization, siderophore production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole-3-acetic acid (IAA) production, and stress response. PMID:26337878

  18. Acid rain and transported air pollutants

    SciTech Connect

    Not Available

    1985-01-01

    This book considers aspects of the air pollutant controversy. It discusses the following: the policy dilemma - including impact on terrestrial and aquatic eco-systems, effects on human health, diplomatic issues, and how control would benefit some industries and hurt others; scientific uncertainties about the extent and location of current damage, future damage, the origin of transported air pollutants, and the efficacy of current and proposed emissions control programs; how three major pollutants - sulfur dioxide, nitrous oxide, and reactive hydrocarbons - are distributed geographically; the effect of current legislation on acid rain and its distribution; how geographic and economic risks are dispersed throughout the United States; and other risks, such as potential damage to buildings and metals.

  19. Targeted systems biology profiling of tomato fruit reveals coordination of the Yang cycle and a distinct regulation of ethylene biosynthesis during postclimacteric ripening.

    PubMed

    Van de Poel, Bram; Bulens, Inge; Markoula, Aikaterina; Hertog, Maarten L A T M; Dreesen, Rozemarijn; Wirtz, Markus; Vandoninck, Sandy; Oppermann, Yasmin; Keulemans, Johan; Hell, Ruediger; Waelkens, Etienne; De Proft, Maurice P; Sauter, Margret; Nicolai, Bart M; Geeraerd, Annemie H

    2012-11-01

    The concept of system 1 and system 2 ethylene biosynthesis during climacteric fruit ripening was initially described four decades ago. Although much is known about fruit development and climacteric ripening, little information is available about how ethylene biosynthesis is regulated during the postclimacteric phase. A targeted systems biology approach revealed a novel regulatory mechanism of ethylene biosynthesis of tomato (Solanum lycopersicum) when fruit have reached their maximal ethylene production level and which is characterized by a decline in ethylene biosynthesis. Ethylene production is shut down at the level of 1-aminocyclopropane-1-carboxylic acid oxidase. At the same time, 1-aminocyclopropane-1-carboxylic acid synthase activity increases. Analysis of the Yang cycle showed that the Yang cycle genes are regulated in a coordinated way and are highly expressed during postclimacteric ripening. Postclimacteric red tomatoes on the plant showed only a moderate regulation of 1-aminocyclopropane-1-carboxylic acid synthase and Yang cycle genes compared with the regulation in detached fruit. Treatment of red fruit with 1-methylcyclopropane and ethephon revealed that the shut-down mechanism in ethylene biosynthesis is developmentally programmed and only moderately ethylene sensitive. We propose that the termination of autocatalytic ethylene biosynthesis of system 2 in ripe fruit delays senescence and preserves the fruit until seed dispersal.

  20. Novel Lactate Transporters from Carboxylic Acid-Producing Rhizopus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The fungus Rhizopus is frequently used for fermentative production of lactic acid, but little is known about the mechanisms or proteins for transporting this carboxylic acid. Since transport of the lactate anion across the plasma membrane is critical to prevent acidification of the cytoplasm, we ev...

  1. Ascorbic acid transport and accumulation in human neutrophils

    SciTech Connect

    Washko, P.; Rotrosen, D.; Levine, M. )

    1989-11-15

    The transport, accumulation, and distribution of ascorbic acid were investigated in isolated human neutrophils utilizing a new ascorbic acid assay, which combined the techniques of high performance liquid chromatography and coulometric electrochemical detection. Freshly isolated human neutrophils contained 1.0-1.4 mM ascorbic acid, which was localized greater than or equal to 94% to the cytosol, was not protein bound, and was present only as ascorbic acid and not as dehydroascorbic acid. Upon addition of ascorbic acid to the extracellular medium in physiologic amounts, ascorbic acid was accumulated in neutrophils in millimolar concentrations. Accumulation was mediated by a high affinity and a low affinity transporter; both transporters were responsible for maintenance of concentration gradients as large as 50-fold. The high affinity transporter had an apparent Km of 2-5 microns by Lineweaver-Burk and Eadie-Hofstee analyses, and the low affinity transporter had an apparent Km of 6-7 mM by similar analyses. Each transporter was saturable and temperature dependent. In normal human blood the high affinity transporter should be saturated, whereas the low affinity transporter should be in its linear phase of uptake.

  2. Differential regulation of placental amino acid transport by saturated and unsaturated fatty acids.

    PubMed

    Lager, Susanne; Jansson, Thomas; Powell, Theresa L

    2014-10-15

    Fatty acids are critical for normal fetal development but may also influence placental function. We have previously reported that oleic acid (OA) stimulates amino acid transport in primary human trophoblasts (PHTs). In other tissues, saturated and unsaturated fatty acids have distinct effects on cellular signaling, for instance, palmitic acid (PA) but not OA reduces IκBα expression. We hypothesized that saturated and unsaturated fatty acids differentially affect trophoblast amino acid transport and cellular signaling. To test this hypothesis, PHTs were cultured in docosahexaenoic acid (DHA; 50 μM), OA (100 μM), or PA (100 μM). DHA and OA were also combined to test whether DHA could counteract the OA stimulatory effect on amino acid transport. The effects of fatty acids were compared against a vehicle control. Amino acid transport was measured by isotope-labeled tracers. Activation of inflammatory-related signaling pathways and the mechanistic target of rapamycin (mTOR) pathway were determined by Western blot analysis. Exposure of PHTs to DHA for 24 h reduced amino acid transport and phosphorylation of p38 MAPK, STAT3, mTOR, eukaryotic initiation factor 4E-binding protein 1, and ribosomal protein (rp)S6. In contrast, OA increased amino acid transport and phosphorylation of ERK, mTOR, S6 kinase 1, and rpS6. The combination of DHA with OA increased amino acid transport and rpS6 phosphorylation. PA did not affect amino acid transport but reduced IκBα expression. In conclusion, these fatty acids differentially regulated placental amino acid transport and cellular signaling. Taken together, these findings suggest that dietary fatty acids could alter the intrauterine environment by modifying placental function, thereby having long-lasting effects on the developing fetus.

  3. Amino acid transporters: roles in amino acid sensing and signalling in animal cells.

    PubMed Central

    Hyde, Russell; Taylor, Peter M; Hundal, Harinder S

    2003-01-01

    Amino acid availability regulates cellular physiology by modulating gene expression and signal transduction pathways. However, although the signalling intermediates between nutrient availability and altered gene expression have become increasingly well documented, how eukaryotic cells sense the presence of either a nutritionally rich or deprived medium is still uncertain. From recent studies it appears that the intracellular amino acid pool size is particularly important in regulating translational effectors, thus, regulated transport of amino acids across the plasma membrane represents a means by which the cellular response to amino acids could be controlled. Furthermore, evidence from studies with transportable amino acid analogues has demonstrated that flux through amino acid transporters may act as an initiator of nutritional signalling. This evidence, coupled with the substrate selectivity and sensitivity to nutrient availability classically associated with amino acid transporters, plus the recent discovery of transporter-associated signalling proteins, demonstrates a potential role for nutrient transporters as initiators of cellular nutrient signalling. Here, we review the evidence supporting the idea that distinct amino acid "receptors" function to detect and transmit certain nutrient stimuli in higher eukaryotes. In particular, we focus on the role that amino acid transporters may play in the sensing of amino acid levels, both directly as initiators of nutrient signalling and indirectly as regulators of external amino acid access to intracellular receptor/signalling mechanisms. PMID:12879880

  4. Expression of heteromeric amino acid transporters along the murine intestine.

    PubMed

    Dave, Mital H; Schulz, Nicole; Zecevic, Marija; Wagner, Carsten A; Verrey, Francois

    2004-07-15

    Members of the new heterodimeric amino acid transporter family are composed of two subunits, a catalytic multitransmembrane spanning protein (light chain) and a type II glycoprotein (heavy chain). These transporters function as exchangers and thereby extend the transmembrane amino acid transport selectivity to specific amino acids. The heavy chain rBAT associates with the light chain b degrees (,+)AT to form a cystine and cationic amino acid transporter. The other heavy chain, 4F2hc, can interact with seven different light chains to form various transporters corresponding to systems L, y(+)L, asc or x(-)(c). The importance of some of these transporters in intestinal and renal (re)absorption of amino acids is highlighted by the fact that mutations in either the rBAT or b degrees (,+)AT subunit result in cystinuria whereas a defect in the y(+)-LAT1 light chain causes lysinuric protein intolerance. Here we investigated the localization of these transporters in intestine since both diseases are also characterized by altered intestinal amino acid absorption. Real time PCR showed organ-specific expression patterns for all transporter subunit mRNAs along the intestine and Western blotting confirmed these findings on the protein level. Immunohistochemistry demonstrated basolateral coexpression of 4F2hc, LAT2 and y(+)-LAT1 in stomach and small intestine, whereas rBAT and b degrees (,+)AT were found colocalizing on the apical side of small intestine epithelium. In stomach, 4F2hc and LAT2 were localized in H(+)/K(+)-ATPase-expressing parietal cells. The abundant expression of several members of the heterodimeric transporter family along the murine small intestine suggests their involvement in amino acids absorption. Furthermore, strong expression of rBAT, b degrees (,+)AT and y(+)-LAT1 in the small intestine explains the reduced intestinal absorption of some amino acid in patients with cystinuria or lysinuric protein intolerance.

  5. Identification and application of keto acids transporters in Yarrowia lipolytica.

    PubMed

    Guo, Hongwei; Liu, Peiran; Madzak, Catherine; Du, Guocheng; Zhou, Jingwen; Chen, Jian

    2015-01-30

    Production of organic acids by microorganisms is of great importance for obtaining building-block chemicals from sustainable biomass. Extracellular accumulation of organic acids involved a series of transporters, which play important roles in the accumulation of specific organic acid while lack of systematic demonstration in eukaryotic microorganisms. To circumvent accumulation of by-product, efforts have being orchestrated to carboxylate transport mechanism for potential clue in Yarrowia lipolytica WSH-Z06. Six endogenous putative transporter genes, YALI0B19470g, YALI0C15488g, YALI0C21406g, YALI0D24607g, YALI0D20108g and YALI0E32901g, were identified. Transport characteristics and substrate specificities were further investigated using a carboxylate-transport-deficient Saccharomyces cerevisiae strain. These transporters were expressed in Y. lipolytica WSH-Z06 to assess their roles in regulating extracellular keto acids accumulation. In a Y. lipolytica T1 line over expressing YALI0B19470g, α-ketoglutarate accumulated to 46.7 g·L(-1), whereas the concentration of pyruvate decreased to 12.3 g·L(-1). Systematic identification of these keto acids transporters would provide clues to further improve the accumulation of specific organic acids with higher efficiency in eukaryotic microorganisms.

  6. Identification and application of keto acids transporters in Yarrowia lipolytica

    PubMed Central

    Guo, Hongwei; Liu, Peiran; Madzak, Catherine; Du, Guocheng; Zhou, Jingwen; Chen, Jian

    2015-01-01

    Production of organic acids by microorganisms is of great importance for obtaining building-block chemicals from sustainable biomass. Extracellular accumulation of organic acids involved a series of transporters, which play important roles in the accumulation of specific organic acid while lack of systematic demonstration in eukaryotic microorganisms. To circumvent accumulation of by-product, efforts have being orchestrated to carboxylate transport mechanism for potential clue in Yarrowia lipolytica WSH-Z06. Six endogenous putative transporter genes, YALI0B19470g, YALI0C15488g, YALI0C21406g, YALI0D24607g, YALI0D20108g and YALI0E32901g, were identified. Transport characteristics and substrate specificities were further investigated using a carboxylate-transport-deficient Saccharomyces cerevisiae strain. These transporters were expressed in Y. lipolytica WSH-Z06 to assess their roles in regulating extracellular keto acids accumulation. In a Y. lipolytica T1 line over expressing YALI0B19470g, α-ketoglutarate accumulated to 46.7 g·L−1, whereas the concentration of pyruvate decreased to 12.3 g·L−1. Systematic identification of these keto acids transporters would provide clues to further improve the accumulation of specific organic acids with higher efficiency in eukaryotic microorganisms. PMID:25633653

  7. Carboxylic Acids Plasma Membrane Transporters in Saccharomyces cerevisiae.

    PubMed

    Casal, Margarida; Queirós, Odília; Talaia, Gabriel; Ribas, David; Paiva, Sandra

    2016-01-01

    This chapter covers the functionally characterized plasma membrane carboxylic acids transporters Jen1, Ady2, Fps1 and Pdr12 in the yeast Saccharomyces cerevisiae, addressing also their homologues in other microorganisms, as filamentous fungi and bacteria. Carboxylic acids can either be transported into the cells, to be used as nutrients, or extruded in response to acid stress conditions. The secondary active transporters Jen1 and Ady2 can mediate the uptake of the anionic form of these substrates by a H(+)-symport mechanism. The undissociated form of carboxylic acids is lipid-soluble, crossing the plasma membrane by simple diffusion. Furthermore, acetic acid can also be transported by facilitated diffusion via Fps1 channel. At the cytoplasmic physiological pH, the anionic form of the acid prevails and it can be exported by the Pdr12 pump. This review will highlight the mechanisms involving carboxylic acids transporters, and the way they operate according to the yeast cell response to environmental changes, as carbon source availability, extracellular pH and acid stress conditions.

  8. Assessing the allelotypic effect of two aminocyclopropane carboxylic acid synthase-encoding genes MdACS1 and MdACS3a on fruit ethylene production and softening in Malus.

    PubMed

    Dougherty, Laura; Zhu, Yuandi; Xu, Kenong

    2016-01-01

    Phytohormone ethylene largely determines apple fruit shelf life and storability. Previous studies demonstrated that MdACS1 and MdACS3a, which encode 1-aminocyclopropane-1-carboxylic acid synthases (ACS), are crucial in apple fruit ethylene production. MdACS1 is well-known to be intimately involved in the climacteric ethylene burst in fruit ripening, while MdACS3a has been regarded a main regulator for ethylene production transition from system 1 (during fruit development) to system 2 (during fruit ripening). However, MdACS3a was also shown to have limited roles in initiating the ripening process lately. To better assess their roles, fruit ethylene production and softening were evaluated at five time points during a 20-day post-harvest period in 97 Malus accessions and in 34 progeny from 2 controlled crosses. Allelotyping was accomplished using an existing marker (ACS1) for MdACS1 and two markers (CAPS866 and CAPS870) developed here to specifically detect the two null alleles (ACS3a-G289V and Mdacs3a) of MdACS3a. In total, 952 Malus accessions were allelotyped with the three markers. The major findings included: The effect of MdACS1 was significant on fruit ethylene production and softening while that of MdACS3a was less detectable; allele MdACS1-2 was significantly associated with low ethylene and slow softening; under the same background of the MdACS1 allelotypes, null allele Mdacs3a (not ACS3a-G289V) could confer a significant delay of ethylene peak; alleles MdACS1-2 and Mdacs3a (excluding ACS3a-G289V) were highly enriched in M. domestica and M. hybrid when compared with those in M. sieversii. These findings are of practical implications in developing apples of low and delayed ethylene profiles by utilizing the beneficial alleles MdACS1-2 and Mdacs3a. PMID:27231553

  9. Assessing the allelotypic effect of two aminocyclopropane carboxylic acid synthase-encoding genes MdACS1 and MdACS3a on fruit ethylene production and softening in Malus

    PubMed Central

    Dougherty, Laura; Zhu, Yuandi; Xu, Kenong

    2016-01-01

    Phytohormone ethylene largely determines apple fruit shelf life and storability. Previous studies demonstrated that MdACS1 and MdACS3a, which encode 1-aminocyclopropane-1-carboxylic acid synthases (ACS), are crucial in apple fruit ethylene production. MdACS1 is well-known to be intimately involved in the climacteric ethylene burst in fruit ripening, while MdACS3a has been regarded a main regulator for ethylene production transition from system 1 (during fruit development) to system 2 (during fruit ripening). However, MdACS3a was also shown to have limited roles in initiating the ripening process lately. To better assess their roles, fruit ethylene production and softening were evaluated at five time points during a 20-day post-harvest period in 97 Malus accessions and in 34 progeny from 2 controlled crosses. Allelotyping was accomplished using an existing marker (ACS1) for MdACS1 and two markers (CAPS866 and CAPS870) developed here to specifically detect the two null alleles (ACS3a-G289V and Mdacs3a) of MdACS3a. In total, 952 Malus accessions were allelotyped with the three markers. The major findings included: The effect of MdACS1 was significant on fruit ethylene production and softening while that of MdACS3a was less detectable; allele MdACS1–2 was significantly associated with low ethylene and slow softening; under the same background of the MdACS1 allelotypes, null allele Mdacs3a (not ACS3a-G289V) could confer a significant delay of ethylene peak; alleles MdACS1–2 and Mdacs3a (excluding ACS3a-G289V) were highly enriched in M. domestica and M. hybrid when compared with those in M. sieversii. These findings are of practical implications in developing apples of low and delayed ethylene profiles by utilizing the beneficial alleles MdACS1-2 and Mdacs3a. PMID:27231553

  10. Characterization of 2-aminoisobutyric acid transport in Neurospora crassa: a general amino acid permease-specific substrate.

    PubMed Central

    Ogilvie-Villa, S; DeBusk, R M; DeBusk, A G

    1981-01-01

    We report the characterization of an amino acid 2-aminoisobutyric acid was transported solely by the general amino acid permease and not by the neutral amino acid permease. Furthermore, this substrate was not metabolized after transport. The potential for a system-specific nonmetabolizable substrate as a tool in the analysis of amino acid transport and its regulation is discussed. PMID:6456264

  11. Nucleic acids encoding metal uptake transporters and their uses

    DOEpatents

    Schroeder, Julian I.; Antosiewicz, Danuta M.; Schachtman, Daniel P.; Clemens, Stephan

    1999-01-01

    The invention provides LCT1 nucleic acids which encode metal ion uptake transporters. The invention also provides methods of modulating heavy metal and alkali metal uptake in plants. The methods involve producing transgenic plants comprising a recombinant expression cassette containing an LCT1 nucleic acid linked to a plant promoter.

  12. Molecular Evolution of Plant AAP and LHT Amino Acid Transporters.

    PubMed

    Tegeder, Mechthild; Ward, John M

    2012-01-01

    Nitrogen is an essential mineral nutrient and it is often transported within living organisms in its reduced form, as amino acids. Transport of amino acids across cellular membranes requires proteins, and here we report the phylogenetic analysis across taxa of two amino acid transporter families, the amino acid permeases (AAPs) and the lysine-histidine-like transporters (LHTs). We found that the two transporter families form two distinct groups in plants supporting the concept that both are essential. AAP transporters seem to be restricted to land plants. They were found in Selaginella moellendorffii and Physcomitrella patens but not in Chlorophyte, Charophyte, or Rhodophyte algae. AAPs were strongly represented in vascular plants, consistent with their major function in phloem (vascular tissue) loading of amino acids for sink nitrogen supply. LHTs on the other hand appeared prior to land plants. LHTs were not found in chlorophyte algae Chlamydomonas reinhardtii and Volvox carterii. However, the characean alga Klebsormidium flaccidum encodes KfLHT13 and phylogenetic analysis indicates that it is basal to land plant LHTs. This is consistent with the hypothesis that characean algae are ancestral to land plants. LHTs were also found in both S. moellendorffii and P. patens as well as in monocots and eudicots. To date, AAPs and LHTs have mainly been characterized in Arabidopsis (eudicots) and these studies provide clues to the functions of the newly identified homologs. PMID:22645574

  13. Molecular Evolution of Plant AAP and LHT Amino Acid Transporters

    PubMed Central

    Tegeder, Mechthild; Ward, John M.

    2012-01-01

    Nitrogen is an essential mineral nutrient and it is often transported within living organisms in its reduced form, as amino acids. Transport of amino acids across cellular membranes requires proteins, and here we report the phylogenetic analysis across taxa of two amino acid transporter families, the amino acid permeases (AAPs) and the lysine–histidine-like transporters (LHTs). We found that the two transporter families form two distinct groups in plants supporting the concept that both are essential. AAP transporters seem to be restricted to land plants. They were found in Selaginella moellendorffii and Physcomitrella patens but not in Chlorophyte, Charophyte, or Rhodophyte algae. AAPs were strongly represented in vascular plants, consistent with their major function in phloem (vascular tissue) loading of amino acids for sink nitrogen supply. LHTs on the other hand appeared prior to land plants. LHTs were not found in chlorophyte algae Chlamydomonas reinhardtii and Volvox carterii. However, the characean alga Klebsormidium flaccidum encodes KfLHT13 and phylogenetic analysis indicates that it is basal to land plant LHTs. This is consistent with the hypothesis that characean algae are ancestral to land plants. LHTs were also found in both S. moellendorffii and P. patens as well as in monocots and eudicots. To date, AAPs and LHTs have mainly been characterized in Arabidopsis (eudicots) and these studies provide clues to the functions of the newly identified homologs. PMID:22645574

  14. Metabolism and transport of gamma-carboxyglutamic acid.

    PubMed

    Shah, D V; Tews, J K; Harper, A E; Suttie, J W

    1978-03-01

    gamma-Carboxyglutamic acid residues have beeh shown to be present in prothrombin, the other vitamin K-dependent clotting factors, and more recently in bone and kidney proteins. This amino acid is formed by a posttranslational vitamin K-dependent carboxylation of glutamyl residues in polypeptide precursors of these protens. It has now been demonstrated that this amino acid, either in the free or peptide-bound form, is not metabolically degraded by the rat, but is quantitatively excreted in the urine. In nephrectomized rats, the tissue concentration of intravenously administered gamma-carboxyglutamic acid is increased, but there is still no evidence of any oxidative metabolism of this amino acid. These amino acid is transported by kidney slices against a concentration gradient, but does not accumulate in liver, intestinal or brain tissues. Preliminary data suggest that gamma-carboxyglutamic acid may be concentrated by a carrier system different from that utilized by other amino acids. PMID:629998

  15. Role of the Intestinal Bile Acid Transporters in Bile Acid and Drug Disposition

    PubMed Central

    Dawson, Paul A.

    2011-01-01

    Membrane transporters expressed by the hepatocyte and enterocyte play critical roles in maintaining the enterohepatic circulation of bile acids, an effective recycling and conservation mechanism that largely restricts these potentially cytotoxic detergents to the intestinal and hepatobiliary compartments. In doing so, the hepatic and enterocyte transport systems ensure a continuous supply of bile acids to be used repeatedly during the digestion of multiple meals throughout the day. Absorption of bile acids from the intestinal lumen and export into the portal circulation is mediated by a series of transporters expressed on the enterocyte apical and basolateral membranes. The ileal apical sodium-dependent bile acid cotransporter (abbreviated ASBT; gene symbol, SLC10A2) is responsible for the initial uptake of bile acids across the enterocyte brush border membrane. The bile acids are then efficiently shuttled across the cell and exported across the basolateral membrane by the heteromeric Organic Solute Transporter, OSTα-OSTβ. This chapter briefly reviews the tissue expression, physiology, genetics, pathophysiology, and transport properties of the ASBT and OSTα-OSTα. In addition, the chapter discusses the relationship between the intestinal bile acid transporters and drug metabolism, including development of ASBT inhibitors as novel hypocholesterolemic or hepatoprotective agents, prodrug targeting of the ASBT to increase oral bioavailability, and involvement of the intestinal bile acid transporters in drug absorption and drug-drug interactions. PMID:21103970

  16. The interaction with arbuscular mycorrhizal fungi or Trichoderma harzianum alters the shoot hormonal profile in melon plants.

    PubMed

    Martínez-Medina, Ainhoa; Roldán, Antonio; Albacete, Alfonso; Pascual, Jose A

    2011-02-01

    Arbuscular mycorrhizal fungi (AMF) and Trichoderma harzianum are known to affect plant growth and disease resistance through interaction with phytohormone synthesis or transport in the plant. Cross-talk between these microorganisms and their host plants normally occurs in nature and may affect plant resistance. Simultaneous quantification in the shoots of melon plants revealed significant changes in the levels of several hormones in response to inoculation with T. harzianum and two different AMF (Glomus intraradices and Glomus mosseae). Analysis of zeatin (Ze), indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylic acid (ACC), salicylic acid (SA), jasmonic acid (JA) and abscisic acid (ABA) in the shoot showed common and divergent responses of melon plants to G. intraradices and G. mosseae. T. harzianum effected systemic increases in Ze, IAA, ACC, SA, JA and ABA. The interaction of T. harzianum and the AMF with the plant produced a characteristic hormonal profile, which differed from that produced by inoculation with each microorganism singly, suggesting an attenuation of the plant response, related to the hormones SA, JA and ethylene. These results are discussed in relation to their involvement in biomass allocation and basal resistance against Fusarium wilt. PMID:21145086

  17. Xenobiotic, bile acid, and cholesterol transporters: function and regulation.

    PubMed

    Klaassen, Curtis D; Aleksunes, Lauren M

    2010-03-01

    Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting beta polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) alpha and beta] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of

  18. Xenobiotic, Bile Acid, and Cholesterol Transporters: Function and Regulation

    PubMed Central

    Aleksunes, Lauren M.

    2010-01-01

    Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting β polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) α and β] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory

  19. Intestinal dehydroascorbic acid (DHA) transport mediated by the facilitative sugar transporters, GLUT2 and GLUT8.

    PubMed

    Corpe, Christopher P; Eck, Peter; Wang, Jin; Al-Hasani, Hadi; Levine, Mark

    2013-03-29

    Intestinal vitamin C (Asc) absorption was believed to be mediated by the Na(+)-dependent ascorbic acid transporter SVCT1. However, Asc transport across the intestines of SVCT1 knock-out mice is normal indicating that alternative ascorbic acid transport mechanisms exist. To investigate these mechanisms, rodents were gavaged with Asc or its oxidized form dehydroascorbic acid (DHA), and plasma Asc concentrations were measured. Asc concentrations doubled following DHA but not Asc gavage. We hypothesized that the transporters responsible were facilitated glucose transporters (GLUTs). Using Xenopus oocyte expression, we investigated whether facilitative glucose transporters GLUT2 and GLUT5-12 transported DHA. Only GLUT2 and GLUT8, known to be expressed in intestines, transported DHA with apparent transport affinities (Km) of 2.33 and 3.23 mm and maximal transport rates (Vmax) of 25.9 and 10.1 pmol/min/oocyte, respectively. Maximal rates for DHA transport mediated by GLUT2 and GLUT8 in oocytes were lower than maximal rates for 2-deoxy-d-glucose (Vmax of 224 and 32 pmol/min/oocyte for GLUT2 and GLUT8, respectively) and fructose (Vmax of 406 and 116 pmol/min/oocyte for GLUT2 and GLUT8, respectively). These findings may be explained by differences in the exofacial binding of substrates, as shown by inhibition studies with ethylidine glucose. DHA transport activity in GLUT2- and GLUT8-expressing oocytes was inhibited by glucose, fructose, and by the flavonoids phloretin and quercetin. These studies indicate intestinal DHA transport may be mediated by the facilitative sugar transporters GLUT2 and GLUT8. Furthermore, dietary sugars and flavonoids in fruits and vegetables may modulate Asc bioavailability via inhibition of small intestinal GLUT2 and GLUT8.

  20. Transport Function of Rice Amino Acid Permeases (AAPs).

    PubMed

    Taylor, Margaret R; Reinders, Anke; Ward, John M

    2015-07-01

    The transport function of four rice (Oryza sativa) amino acid permeases (AAPs), OsAAP1 (Os07g04180), OsAAP3 (Os06g36180), OsAAP7 (Os05g34980) and OsAAP16 (Os12g08090), was analyzed by expression in Xenopus laevis oocytes and electrophysiology. OsAAP1, OsAAP7 and OsAAP16 functioned, similarly to Arabidopsis AAPs, as general amino acid permeases. OsAAP3 had a distinct substrate specificity compared with other rice or Arabidopsis AAPs. OsAAP3 transported the basic amino acids lysine and arginine well but selected against aromatic amino acids. The transport of basic amino acids was further analyzed for OsAAP1 and OsAAP3, and the results support the transport of both neutral and positively charged forms of basic amino acids by the rice AAPs. Cellular localization using the tandem enhanced green fluorescent protein (EGFP)-red fluorescent protein (RFP) reporter pHusion showed that OsAAP1 and OsAAP3 localized to the plasma membrane after transient expression in onion epidermal cells or stable expression in Arabidopsis. PMID:25907566

  1. Early steps of adventitious rooting: morphology, hormonal profiling and carbohydrate turnover in carnation stem cuttings.

    PubMed

    Agulló-Antón, María Ángeles; Ferrández-Ayela, Almudena; Fernández-García, Nieves; Nicolás, Carlos; Albacete, Alfonso; Pérez-Alfocea, Francisco; Sánchez-Bravo, José; Pérez-Pérez, José Manuel; Acosta, Manuel

    2014-03-01

    The rooting of stem cuttings is a common vegetative propagation practice in many ornamental species. A detailed analysis of the morphological changes occurring in the basal region of cultivated carnation cuttings during the early stages of adventitious rooting was carried out and the physiological modifications induced by exogenous auxin application were studied. To this end, the endogenous concentrations of five major classes of plant hormones [auxin, cytokinin (CK), abscisic acid, salicylic acid (SA) and jasmonic acid] and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid were analyzed at the base of stem cuttings and at different stages of adventitious root formation. We found that the stimulus triggering the initiation of adventitious root formation occurred during the first hours after their excision from the donor plant, due to the breakdown of the vascular continuum that induces auxin accumulation near the wounding. Although this stimulus was independent of exogenously applied auxin, it was observed that the auxin treatment accelerated cell division in the cambium and increased the sucrolytic activities at the base of the stem, both of which contributed to the establishment of the new root primordia at the stem base. Further, several genes involved in auxin transport were upregulated in the stem base either with or without auxin application, while endogenous CK and SA concentrations were specially affected by exogenous auxin application. Taken together our results indicate significant crosstalk between auxin levels, stress hormone homeostasis and sugar availability in the base of the stem cuttings in carnation during the initial steps of adventitious rooting. PMID:24117983

  2. Early steps of adventitious rooting: morphology, hormonal profiling and carbohydrate turnover in carnation stem cuttings.

    PubMed

    Agulló-Antón, María Ángeles; Ferrández-Ayela, Almudena; Fernández-García, Nieves; Nicolás, Carlos; Albacete, Alfonso; Pérez-Alfocea, Francisco; Sánchez-Bravo, José; Pérez-Pérez, José Manuel; Acosta, Manuel

    2014-03-01

    The rooting of stem cuttings is a common vegetative propagation practice in many ornamental species. A detailed analysis of the morphological changes occurring in the basal region of cultivated carnation cuttings during the early stages of adventitious rooting was carried out and the physiological modifications induced by exogenous auxin application were studied. To this end, the endogenous concentrations of five major classes of plant hormones [auxin, cytokinin (CK), abscisic acid, salicylic acid (SA) and jasmonic acid] and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid were analyzed at the base of stem cuttings and at different stages of adventitious root formation. We found that the stimulus triggering the initiation of adventitious root formation occurred during the first hours after their excision from the donor plant, due to the breakdown of the vascular continuum that induces auxin accumulation near the wounding. Although this stimulus was independent of exogenously applied auxin, it was observed that the auxin treatment accelerated cell division in the cambium and increased the sucrolytic activities at the base of the stem, both of which contributed to the establishment of the new root primordia at the stem base. Further, several genes involved in auxin transport were upregulated in the stem base either with or without auxin application, while endogenous CK and SA concentrations were specially affected by exogenous auxin application. Taken together our results indicate significant crosstalk between auxin levels, stress hormone homeostasis and sugar availability in the base of the stem cuttings in carnation during the initial steps of adventitious rooting.

  3. Transported acid aerosols measured in southern Ontario

    NASA Astrophysics Data System (ADS)

    Keeler, Gerald J.; Spengler, John D.; Koutrakis, Petros; Allen, George A.; Raizenne, Mark; Stern, Bonnie

    During the period 29 June 1986-9 August 1986, a field health study assessing the acute health effects of air pollutants on children was conducted at a summer girls' camp on the northern shore of Lake Erie in SW Ontario. Continuous air pollution measurements of SO 2, O 3, NO x, particulate sulfates, light scattering, and meteorological measurements including temperature, dew point, and wind speed and direction were made. Twelve-hour integrated samples of size fractioned particles were also obtained using dichotomous samplers and Harvard impactors equipped with an ammonia denuder for subsequent hydrogen ion determination. Particulate samples were analyzed for trace elements by X-ray fluorescence and Neutron Activation, and for organic and elemental carbon by a thermal/optical technique. The measured aerosol was periodically very acidic with observed 12-h averaged H + concentrations in the range < 10-560 nmoles m -3. The aerosol H + appeared to represent the net strong acidity after H 2SO 4 reaction with NH 3(g). Average daytime concentrations were higher than night-time for aerosol H +, sulfate, fine mass and ozone. Prolonged episodes of atmospheric acidity, sulfate, and ozone were associated with air masses arriving at the measurement site from the west and from the southwest over Lake Erie. Sulfate concentrations measured at the lakeshore camp were more than twice those measured at inland sites during extreme pollution episodes. The concentration gradient observed with onshore flow was potentially due to enhanced deposition near the lakeshore caused by discontinuities in the meteorological fields in this region.

  4. Fatty acid transport and utilization for the developing brain.

    PubMed

    Edmond, J; Higa, T A; Korsak, R A; Bergner, E A; Lee, W N

    1998-03-01

    To determine the transport and utilization of dietary saturated, monounsaturated, and n-6 and n-3 polyunsaturated fatty acids for the developing brain and other organs, artificially reared rat pups were fed a rat milk substitute containing the perdeuterated (each 97 atom% deuterium) fatty acids, i.e., palmitic, stearic, oleic, linoleic, and linolenic, from day 7 after birth to day 14 as previously described. Fatty acids in lipid extracts of the liver, lung, kidney, and brain were analyzed by gas chromatography-mass spectrometry to determine their content of each of the deuterated fatty acids. The uptake and metabolism of perdeuterated fatty acid lead to the appearance of three distinct groups of isotopomers: the intact perdeuterated, the newly synthesized (with recycled deuterium), and the natural unlabeled fatty acid. The quantification of these isotopomers permits the estimation of uptake and de novo synthesis of these fatty acids. Intact perdeuterated palmitic, stearic, and oleic acids from the diet were found in liver, lung, and kidney, but not in brain. By contrast, perdeuterated linoleic acid was found in all these organs. Isotopomers of fatty acid from de novo synthesis were observed in palmitic, oleic, and stearic acids in all tissues. The highest enrichment of isotopomers with recycled deuterium was found in the brain. The data indicate that, during the brain growth spurt and the prelude to myelination, the major saturated and monounsaturated fatty acids in brain lipids are exclusively produced locally by de novo biosynthesis. Consequently, the n-6 and n-3 polyunsaturated fatty acids must be transported and delivered to the brain by highly specific mechanisms.

  5. Primordial transport of sugars and amino acids via Schiff bases

    NASA Astrophysics Data System (ADS)

    Stillwell, William; Rau, Aruna

    1981-09-01

    Experimental support is given for a model concerning the origin of a primordial transport system. The model is based on the facilitated diffusion of amino acids stimulated by aliphatic aldehyde carriers and sugars stimulated by aliphatic amine carriers. The lipid-soluble diffusing species is the Schiff base. The possible role of this simple transport system in the origin of an early protocell is discussed.

  6. Regulation of amino acid metabolic enzymes and transporters in plants.

    PubMed

    Pratelli, Réjane; Pilot, Guillaume

    2014-10-01

    Amino acids play several critical roles in plants, from providing the building blocks of proteins to being essential metabolites interacting with many branches of metabolism. They are also important molecules that shuttle organic nitrogen through the plant. Because of this central role in nitrogen metabolism, amino acid biosynthesis, degradation, and transport are tightly regulated to meet demand in response to nitrogen and carbon availability. While much is known about the feedback regulation of the branched biosynthesis pathways by the amino acids themselves, the regulation mechanisms at the transcriptional, post-transcriptional, and protein levels remain to be identified. This review focuses mainly on the current state of our understanding of the regulation of the enzymes and transporters at the transcript level. Current results describing the effect of transcription factors and protein modifications lead to a fragmental picture that hints at multiple, complex levels of regulation that control and coordinate transport and enzyme activities. It also appears that amino acid metabolism, amino acid transport, and stress signal integration can influence each other in a so-far unpredictable fashion.

  7. Effect of inhibitors of arachidonic acid metabolism on alpha-aminoisobutyric acid transport in human lymphocytes.

    PubMed

    Udey, M C; Parker, C W

    1982-02-01

    The role of arachidonic acid metabolism (or metabolites) in the modulation of alpha-aminoisobutyric acid transport in resting and concanavalin A-stimulated human peripheral blood lymphocytes was evaluated using previously characterized inhibitors of arachidonic acid metabolism. Nordihydroguairetic acid (a nonselective antioxidant), 5,8,11,14-eicosatetraynoic acid (an inhibitor of lipoxygenase and cyclooxygenase activities), indomethacin and acetylsalicylic acid (selective cyclooxygenase inhibitors), and 1-benzylimidazole, Ro-22-3581 and Ro-22-3582 (thromboxane synthetase inhibitors) proved to be potent inhibitors of amino acid transport activity in normal resting and lectin-activated lymphocytes at concentrations known to decrease thromboxane A2 production. The rank order of effectiveness of these various inhibitors compared favorably with their relative potencies as inhibitors of thromboxane B2 synthesis under the same conditions, as determined by radioimmunoassay. Inhibitory effects noted were not due to overt cytotoxicity and seemed to involve changes primarily in the Vmax and not the Km of the transport process. Drug-induced alterations in the magnitude of concanavalin A binding were not observed. These results suggest that the activity of amino acid transport systems can be influenced by certain arachidonic acid metabolites, probably thromboxanes, in both stimulated and unstimulated lymphocytes. In addition, these findings may provide a partial explanation for the observation that inhibitors of thromboxane formation prevent lymphocyte mitogenesis.

  8. Substrate specificity of amino acid transport in sheep erythrocytes.

    PubMed Central

    Young, J D; Ellory, J C

    1977-01-01

    The specificity of amino acid transport in normal (high-glutathione) sheep erythrocytes was investigated by studying the interaction of various neutral and dibasic amino acids in both competition and exchange experiments. Apparent Ki values were obtained for amino acids as inhibitors of L-alanine influx. Amino acids previously found to be transported by high-glutathione cells at fast rates (L-cysteine, L-alpha-amino-n-butyrate) were the most effective inhibitors. D-Alanine and D-alpha-amino-n-butyrate were without effect. Of the remaining amino acids studied, only L-norvaline, L-valine, L-norleucine, L-serine and L-2,4-diamino-n-butyrate significantly inhibited L-alanine uptake. L-Alanine efflux from pre-loaded cells was markedly stimulated by extracellular L-alanine. Those amino acids that inhibited L-alanine influx also stimulated L-alanine efflux. In addition, D-alanine, D-alpha-amino-n-biutyrate, L-threonine, L-asparagine, L-alpha, beta-diaminoproprionate, L-ornithine, L-lysine and S-2-aminoethyl-L-cysteine also significantly stimulated L-alanine efflux. L-Lysine uptake was inhibited by L-alanine but not by D-alanine, and the inhibitory potency of L-alanine was not influenced by the replacement of Na+ in the incubation medium with choline. L-Lysine efflux from pre-loaded cells was stimulated by L-alanine but not by D-alanine. It is concluded that these cells possess a highly selective stero-specific amino acid-transport system. Although the optimum substrates are small neutral amino acids, this system also has a significant affinity for dibasic amino acids. PMID:849280

  9. Acid-base transport in pancreas—new challenges

    PubMed Central

    Novak, Ivana; Haanes, Kristian A.; Wang, Jing

    2013-01-01

    Along the gastrointestinal tract a number of epithelia contribute with acid or basic secretions in order to aid digestive processes. The stomach and pancreas are the most extreme examples of acid (H+) and base (HCO−3) transporters, respectively. Nevertheless, they share the same challenges of transporting acid and bases across epithelia and effectively regulating their intracellular pH. In this review, we will make use of comparative physiology to enlighten the cellular mechanisms of pancreatic HCO−3 and fluid secretion, which is still challenging physiologists. Some of the novel transporters to consider in pancreas are the proton pumps (H+-K+-ATPases), as well as the calcium-activated K+ and Cl− channels, such as KCa3.1 and TMEM16A/ANO1. Local regulators, such as purinergic signaling, fine-tune, and coordinate pancreatic secretion. Lastly, we speculate whether dys-regulation of acid-base transport contributes to pancreatic diseases including cystic fibrosis, pancreatitis, and cancer. PMID:24391597

  10. Hydrofluoric and nitric acid transport through lipid bilayer membranes.

    PubMed

    Gutknecht, J; Walter, A

    1981-06-01

    Hydrofluoric and nitric acid transport through lipid bilayer membranes were studied by a combination of electrical conductance and pH electrode techniques. Transport occurs primarily by nonionic diffusion of molecular HF and HNO3. Membrane permeabilities to HF and HNO3 ranged from 10(-4) to 10(-3) cm . s-1, five to seven orders of magnitude higher than the permeabilities to NO-3, F- and H+. Our results are consistent with the hypothesis that F- transport through biological membranes occurs mainly by nonionic diffusion of HF. Our results also suggest that of the two principal components of 'acid rain', HNO3 may be more toxic than H2SO4.

  11. A type III ACC synthase, ACS7, is involved in root gravitropism in Arabidopsis thaliana

    PubMed Central

    Chang, Ing-Feng

    2013-01-01

    Ethylene is an important plant hormone that regulates developmental processes in plants. The ethylene biosynthesis pathway is a highly regulated process at both the transcriptional and post-translational level. The transcriptional regulation of these ethylene biosynthesis genes is well known. However, post-translational modifications of the key ethylene biosynthesis enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) are little understood. In vitro kinase assays were conducted on the type III ACS, AtACS7, fusion protein and peptides to determine whether the AtACS7 protein can be phosphorylated by calcium-dependent protein kinase (CDPK). AtACS7 was phosphorylated at Ser216, Thr296, and Ser299 by AtCDPK16 in vitro. To investigate further the function of the ACS7 gene in Arabidopsis, an acs7-1 loss-of-function mutant was isolated. The acs7-1 mutant exhibited less sensitivity to the inhibition of root gravitropism by treatment with the calcium chelator ethylene glycol tetraacetic acid (EGTA). Seedlings were treated with gradient concentrations of ACC. The results showed that a certain concentration of ethylene enhanced the gravity response. Moreover, the acs7-1 mutant was less sensitive to inhibition of the gravity response by treatment with the auxin polar transport inhibitor 1-naphthylphthalamic acid, but exogenous ACC application recovered root gravitropism. Altogether, the results indicate that AtACS7 is involved in root gravitropism in a calcium-dependent manner in Arabidopsis. PMID:23943848

  12. Transport of phytanic acid on lipoproteins in Refsum disease.

    PubMed

    Wierzbicki, A S; Sankaralingam, A; Lumb, P J; Hardman, T C; Sidey, M C; Gibberd, F B

    1999-02-01

    Patients with Refsum disease accumulate significant quantities of phytanic acid in adipose and neural tissue. The accumulation can be reversed by following a diet low in phytanic acid, yet the mechanism of transport of this fatty acid is obscure. We investigated the distribution of phytanic acid in different lipoprotein subfractions in 11 patients with Refsum disease and 9 unaffected siblings. Plasma phytanic acid was distributed on VLDL (16.2% +/- 12.2%), IDL (1.77% +/- 1.64%), LDL (34.8% +/- 12.6%) and HDL (14.3% +/- 7.87%). No correlations with any parameter were seen with total phytanic acid content. Weak nonsignificant correlations were found with the fractional distribution of phytanic acid and VLDL triglyceride (r = 0.35; p = 0.12) and plasma HDL-cholesterol (r = 0.32; p = 0.16) and with LDL:HDL cholesterol ratio (r = 0.33; p = 0.14). Significant correlation of the fractional distribution of phytanic acid on lipoprotein particles was noted with the ratio of apolipoprotein B: apolipoprotein A1-containing particles (r = 0.46; p = 0.03) and apolipoprotein B: apolipoprotein A1 in HDL2 (r = 0.53; p = 0.01). This suggests that the import-export balance for phytanic acid in plasma is related to forward and reverse cholesterol transport on lipoprotein particles, and only weakly to plasma cholesterol and triglycerides. These ratios of apolipoprotein particles may play a significant role in determining the rate of phytanic acid elimination in patients with Refsum disease.

  13. Vertebrate gastrointestinal fermentation: transport mechanisms for volatile fatty acids.

    PubMed

    Titus, E; Ahearn, G A

    1992-04-01

    Symbiotic microbial fermentation of plant polysaccharides can potentially provide significant levels of nutrients to host organisms in the form of volatile fatty acids (VFAs). Microbial fermentation can account for as much as 10% of maintenance energy requirements in carnivores and omnivores, and up to 80% in ruminant herbivores. In this review epithelial transport processes for the products of microbial fermentation are described in various mammalian and lower vertebrate species. Studies of transepithelial movement of VFA in vertebrate gastrointestinal systems have mostly been investigated in the mammals. In these it is widely held that the transmural movement of VFA is a concentration-dependent passive diffusion process whereby VFA is transported in the protonated form. A different model is described in this paper for carrier-mediated VFA transport, by way of anionic exchange with intracellular bicarbonate, in the intestine of a fermenting herbivorous teleost. These models for diffusive and carrier-mediated transport are compared and discussed from both physiological and experimental viewpoints.

  14. Characterization of a broad-scope amino acid transport system in sand dollars

    SciTech Connect

    Davis, J.P.; Bellis, S.; Stephens, G.C. )

    1988-03-01

    Both echinoderm embryos and adults take up {sup 14}C-labelled-{alpha}-amino acids by an apparent broad-scope transport system. This transporter can be characterized as follows: alanine transport is not blocked by {alpha}-(methylamino)isobutyric acid. Leucine and other lipophilic neutral amino acids are preferentially transported. Transport is sodium dependent and blocked by 2-aminobicyclo-(2,2,1)heptane-2-carboxyclic acid. Lysine and aspartate transport is inhibited by lipophilic neutral amino acids. Taurine, a {beta}-neutral amino acid is translocated via a second and independent carrier.

  15. A branched-chain amino acid metabolite drives vascular fatty acid transport and causes insulin resistance.

    PubMed

    Jang, Cholsoon; Oh, Sungwhan F; Wada, Shogo; Rowe, Glenn C; Liu, Laura; Chan, Mun Chun; Rhee, James; Hoshino, Atsushi; Kim, Boa; Ibrahim, Ayon; Baca, Luisa G; Kim, Esl; Ghosh, Chandra C; Parikh, Samir M; Jiang, Aihua; Chu, Qingwei; Forman, Daniel E; Lecker, Stewart H; Krishnaiah, Saikumari; Rabinowitz, Joshua D; Weljie, Aalim M; Baur, Joseph A; Kasper, Dennis L; Arany, Zoltan

    2016-04-01

    Epidemiological and experimental data implicate branched-chain amino acids (BCAAs) in the development of insulin resistance, but the mechanisms that underlie this link remain unclear. Insulin resistance in skeletal muscle stems from the excess accumulation of lipid species, a process that requires blood-borne lipids to initially traverse the blood vessel wall. How this trans-endothelial transport occurs and how it is regulated are not well understood. Here we leveraged PPARGC1a (also known as PGC-1α; encoded by Ppargc1a), a transcriptional coactivator that regulates broad programs of fatty acid consumption, to identify 3-hydroxyisobutyrate (3-HIB), a catabolic intermediate of the BCAA valine, as a new paracrine regulator of trans-endothelial fatty acid transport. We found that 3-HIB is secreted from muscle cells, activates endothelial fatty acid transport, stimulates muscle fatty acid uptake in vivo and promotes lipid accumulation in muscle, leading to insulin resistance in mice. Conversely, inhibiting the synthesis of 3-HIB in muscle cells blocks the ability of PGC-1α to promote endothelial fatty acid uptake. 3-HIB levels are elevated in muscle from db/db mice with diabetes and from human subjects with diabetes, as compared to those without diabetes. These data unveil a mechanism in which the metabolite 3-HIB, by regulating the trans-endothelial flux of fatty acids, links the regulation of fatty acid flux to BCAA catabolism, providing a mechanistic explanation for how increased BCAA catabolic flux can cause diabetes. PMID:26950361

  16. Amino acid transport in the intestine of the caiman.

    PubMed

    Coulson, R A; Hernandez, T

    1983-01-01

    Seventeen amino acids were fed singly to small caimans and the rates of their disappearance from the gut lumen, and of their appearance in intestinal mucosa, whole intestine, whole stomach, and plasma were determined. The results were compared with those in which massive amounts of protein were fed. When single amino acids were fed, only traces of arginine, ornithine, lysine, aspartate and asparagine were absorbed intact. Glycine, alanine and serine were absorbed rapidly reaching mucosal concentrations as high as 40 mM. The others were not concentrated as highly and most were absorbed by the mucosa more slowly than the glycine group. Protein feeding did not result in high amino acid concentrations in the mucosa. Whether amino acids were ingested as protein or in the free state, glycine, alanine and glutamine increased in the mucosa, suggesting these three incorporate nitrogen released from the others. It appeared that several transport systems operate if amino acids are given singly, and that a different more efficient transport system operates during protein digestion.

  17. Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats.

    PubMed Central

    Zhou, A; Nielsen, J H; Farver, O; Thorn, N A

    1991-01-01

    Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper. Images Fig. 6. PMID:2012602

  18. Aging differentially affects human skeletal muscle amino acid transporter expression when essential amino acids are ingested after exercise

    PubMed Central

    Dickinson, Jared M.; Drummond, Micah J.; Coben, Jennifer R.; Volpi, Elena; Rasmussen, Blake B.

    2012-01-01

    Background & Aims Amino acid transporters have been proposed as regulators of protein synthesis. The primary aim of this study was to determine whether amino acid transporter expression is increased in human muscle following resistance exercise (RE) coupled with essential amino acid (EAA) ingestion, and whether a differential response occurs with aging. Secondly, we aimed to compare this response to a previous study examining RE alone. Methods Young (n=7, 30±2yr) and older men (n=6, 70±2yr) ingested EAA 1h after RE. Muscle biopsies were obtained at rest and 3 and 6h postexercise to examine amino acid transporter mRNA and protein expression. Results In both age groups, RE+EAA increased mRNA of L-type amino acid transporter 1 (LAT1)/solute linked carrier (SLC)7A5, sodium-coupled neutral amino acid transporter 2 (SNAT2)/SLC38A2, and cationic amino acid transporter 1/SLC7A1 (p<0.05). SNAT2 protein increased in young at 3 and 6h (p<0.05), whereas old maintained higher LAT1 protein (p<0.05). Compared to RE alone, RE+EAA enhanced amino acid transporter expression only in young (p<0.05). Conclusions RE increases muscle amino acid transporter expression in young and older adults, however, postexercise EAA ingestion enhances amino acid transporter expression only in young indicating that aging may influence the function of specific amino acid transporters. PMID:22889597

  19. Abscisic acid transporters cooperate to control seed germination

    PubMed Central

    Kang, Joohyun; Yim, Sojeong; Choi, Hyunju; Kim, Areum; Lee, Keun Pyo; Lopez-Molina, Luis; Martinoia, Enrico; Lee, Youngsook

    2015-01-01

    Seed germination is a key developmental process that has to be tightly controlled to avoid germination under unfavourable conditions. Abscisic acid (ABA) is an essential repressor of seed germination. In Arabidopsis, it has been shown that the endosperm, a single cell layer surrounding the embryo, synthesizes and continuously releases ABA towards the embryo. The mechanism of ABA transport from the endosperm to the embryo was hitherto unknown. Here we show that four AtABCG transporters act in concert to deliver ABA from the endosperm to the embryo: AtABCG25 and AtABCG31 export ABA from the endosperm, whereas AtABCG30 and AtABCG40 import ABA into the embryo. Thus, this work establishes that radicle extension and subsequent embryonic growth are suppressed by the coordinated activity of multiple ABA transporters expressed in different tissues. PMID:26334616

  20. Transport in Halobacterium Halobium: Light-Induced Cation-Gradients, Amino Acid Transport Kinetics, and Properties of Transport Carriers

    NASA Technical Reports Server (NTRS)

    Lanyi, Janos K.

    1977-01-01

    Cell envelope vesicles prepared from H. halobium contain bacteriorhodopsin and upon illumination protons are ejected. Coupled to the proton motive force is the efflux of Na(+). Measurements of Na-22 flux, exterior pH change, and membrane potential, Delta(psi) (with the dye 3,3'-dipentyloxadicarbocyanine) indicate that the means of Na(+) transport is sodium/proton exchange. The kinetics of the pH changes and other evidence suggests that the antiport is electrogenic (H(+)/Na(++ greater than 1). The resulting large chemical gradient for Na(+) (outside much greater than inside), as well as the membrane potential, will drive the transport of 18 amino acids. The I9th, glutamate, is unique in that its accumulation is indifferent to Delta(psi): this amino acid is transported only when a chemical gradient for Na(+) is present. Thus, when more and more NaCl is included in the vesicles glutamate transport proceeds with longer and longer lags. After illumination the gradient of H+() collapses within 1 min, while the large Na(+) gradient and glutamate transporting activity persists for 10- 15 min, indicating that proton motive force is not necessary for transport. A chemical gradient of Na(+), arranged by suspending vesicles loaded with KCl in NaCl, drives glutamate transport in the dark without other sources of energy, with V(sub max) and K(sub m) comparable to light-induced transport. These and other lines of evidence suggest that the transport of glutamate is facilitated by symport with Na(+), in an electrically neutral fashion, so that only the chemical component of the Na(+) gradient is a driving force.

  1. Molecular basis of essential amino acid transport from studies of insect nutrient amino acid transporters of the SLC6 family (NAT-SLC6)

    PubMed Central

    Boudko, Dmitri Y.

    2012-01-01

    Two protein families that represent major components of essential amino acid transport in insects have been identified. They are annotated as the SLC6 and SLC7 families of transporters according to phylogenetic proximity to characterized amino acid transporters (HUGO nomenclature). Members of these families have been identified as important apical and basolateral parts of transepithelial essential amino acid absorption in the metazoan alimentary canal. Synergistically, they play critical physiological roles as essential substrate providers to diverse metabolic processes, including generic protein synthesis. This review briefly clarifies the requirements for amino acid transport and a variety of amino acid transport mechanisms, including the aforementioned families. Further it focuses on the large group of Nutrient Amino acid Transporters (NATs), which comprise a recently identified subfamily of the Neurotransmitter Sodium Symporter family (NSS or SLC6). The first insect NAT, cloned from the caterpillar gut, has a broad substrate spectrum similar to mammalian B0 transporters. Several new NAT-SLC6 members have been characterized in an effort to explore mechanisms for the essential amino acid absorption in model dipteran insects. The identification and functional characterization of new B0-like and narrow specificity transporters of essential amino acids in fruit fly and mosquitoes leads to a fundamentally important insight: that NATs evolved and act together as the integrated active core of a transport network that mediates active alimentary absorption and systemic distribution of essential amino acids. This role of NATs is projected from the most primitive prokaryotes to the most complex metazoan organisms, and represents an interesting platform for unraveling the molecular evolution of amino acid transport and modeling amino acid transport disorders. The comparative study of NATs elucidates important adaptive differences between essential amino acid transportomes

  2. Neutralizing Aspartate 83 Modifies Substrate Translocation of Excitatory Amino Acid Transporter 3 (EAAT3) Glutamate Transporters*

    PubMed Central

    Hotzy, Jasmin; Machtens, Jan-Philipp; Fahlke, Christoph

    2012-01-01

    Excitatory amino acid transporters (EAATs) terminate glutamatergic synaptic transmission by removing glutamate from the synaptic cleft into neuronal and glial cells. EAATs are not only secondary active glutamate transporters but also function as anion channels. Gating of EAAT anion channels is tightly coupled to transitions within the glutamate uptake cycle, resulting in Na+- and glutamate-dependent anion currents. A point mutation neutralizing a conserved aspartic acid within the intracellular loop close to the end of transmembrane domain 2 was recently shown to modify the substrate dependence of EAAT anion currents. To distinguish whether this mutation affects transitions within the uptake cycle or directly modifies the opening/closing of the anion channel, we used voltage clamp fluorometry. Using three different sites for fluorophore attachment, V120C, M205C, and A430C, we observed time-, voltage-, and substrate-dependent alterations of EAAT3 fluorescence intensities. The voltage and substrate dependence of fluorescence intensities can be described by a 15-state model of the transport cycle in which several states are connected to branching anion channel states. D83A-mediated changes of fluorescence intensities, anion currents, and secondary active transport can be explained by exclusive modifications of substrate translocation rates. In contrast, sole modification of anion channel opening and closing is insufficient to account for all experimental data. We conclude that D83A has direct effects on the glutamate transport cycle and that these effects result in changed anion channel function. PMID:22532568

  3. Aluminum in acidic surface waters: chemistry, transport, and effects.

    PubMed Central

    Driscoll, C T

    1985-01-01

    Ecologically significant concentrations of Al have been reported in surface waters draining "acid-sensitive" watersheds that are receiving elevated inputs of acidic deposition. It has been hypothesized that mineral acids from atmospheric deposition have remobilized Al previously precipitated within the soil during soil development. This Al is then thought to be transported to adjacent surface waters. Dissolved mononuclear Al occurs as aquo Al, as well as OH-, F-, SO4(2-), and organic complexes. Although past investigations have often ignored non-hydroxide complexes of Al, it appears that organic and F complexes are the predominant forms of Al in dilute (low ionic strength) acidic surface waters. The concentration of inorganic forms of Al increases exponentially with decreases in solution pH. This response is similar to the theoretical pH dependent solubility of Al mineral phases. The concentration of organic forms of Al, however, is strongly correlated with variations in organic carbon concentration of surface waters rather than pH. Elevated concentrations of Al in dilute acidic waters are of interest because: Al is an important pH buffer; Al may influence the cycling of important elements like P, organic carbon, and trace metals; and Al is potentially toxic to aquatic organisms. An understanding of the aqueous speciation of Al is essential for an evaluation of these processes. PMID:3935428

  4. Aluminum in acidic surface waters: chemistry, transport, and effects.

    PubMed

    Driscoll, C T

    1985-11-01

    Ecologically significant concentrations of Al have been reported in surface waters draining "acid-sensitive" watersheds that are receiving elevated inputs of acidic deposition. It has been hypothesized that mineral acids from atmospheric deposition have remobilized Al previously precipitated within the soil during soil development. This Al is then thought to be transported to adjacent surface waters. Dissolved mononuclear Al occurs as aquo Al, as well as OH-, F-, SO4(2-), and organic complexes. Although past investigations have often ignored non-hydroxide complexes of Al, it appears that organic and F complexes are the predominant forms of Al in dilute (low ionic strength) acidic surface waters. The concentration of inorganic forms of Al increases exponentially with decreases in solution pH. This response is similar to the theoretical pH dependent solubility of Al mineral phases. The concentration of organic forms of Al, however, is strongly correlated with variations in organic carbon concentration of surface waters rather than pH. Elevated concentrations of Al in dilute acidic waters are of interest because: Al is an important pH buffer; Al may influence the cycling of important elements like P, organic carbon, and trace metals; and Al is potentially toxic to aquatic organisms. An understanding of the aqueous speciation of Al is essential for an evaluation of these processes.

  5. MATE Transporter-Dependent Export of Hydroxycinnamic Acid Amides.

    PubMed

    Dobritzsch, Melanie; Lübken, Tilo; Eschen-Lippold, Lennart; Gorzolka, Karin; Blum, Elke; Matern, Andreas; Marillonnet, Sylvestre; Böttcher, Christoph; Dräger, Birgit; Rosahl, Sabine

    2016-02-01

    The ability of Arabidopsis thaliana to successfully prevent colonization by Phytophthora infestans, the causal agent of late blight disease of potato (Solanum tuberosum), depends on multilayered defense responses. To address the role of surface-localized secondary metabolites for entry control, droplets of a P. infestans zoospore suspension, incubated on Arabidopsis leaves, were subjected to untargeted metabolite profiling. The hydroxycinnamic acid amide coumaroylagmatine was among the metabolites secreted into the inoculum. In vitro assays revealed an inhibitory activity of coumaroylagmatine on P. infestans spore germination. Mutant analyses suggested a requirement of the p-coumaroyl-CoA:agmatine N4-p-coumaroyl transferase ACT for the biosynthesis and of the MATE transporter DTX18 for the extracellular accumulation of coumaroylagmatine. The host plant potato is not able to efficiently secrete coumaroylagmatine. This inability is overcome in transgenic potato plants expressing the two Arabidopsis genes ACT and DTX18. These plants secrete agmatine and putrescine conjugates to high levels, indicating that DTX18 is a hydroxycinnamic acid amide transporter with a distinct specificity. The export of hydroxycinnamic acid amides correlates with a decreased ability of P. infestans spores to germinate, suggesting a contribution of secreted antimicrobial compounds to pathogen defense at the leaf surface. PMID:26744218

  6. Mfsd2a is a transporter for the essential omega-3 fatty acid docosahexaenoic acid.

    PubMed

    Nguyen, Long N; Ma, Dongliang; Shui, Guanghou; Wong, Peiyan; Cazenave-Gassiot, Amaury; Zhang, Xiaodong; Wenk, Markus R; Goh, Eyleen L K; Silver, David L

    2014-05-22

    Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is essential for normal brain growth and cognitive function. Consistent with its importance in the brain, DHA is highly enriched in brain phospholipids. Despite being an abundant fatty acid in brain phospholipids, DHA cannot be de novo synthesized in brain and must be imported across the blood-brain barrier, but mechanisms for DHA uptake in brain have remained enigmatic. Here we identify a member of the major facilitator superfamily--Mfsd2a (previously an orphan transporter)--as the major transporter for DHA uptake into brain. Mfsd2a is found to be expressed exclusively in endothelium of the blood-brain barrier of micro-vessels. Lipidomic analysis indicates that Mfsd2a-deficient (Mfsd2a-knockout) mice show markedly reduced levels of DHA in brain accompanied by neuronal cell loss in hippocampus and cerebellum, as well as cognitive deficits and severe anxiety, and microcephaly. Unexpectedly, cell-based studies indicate that Mfsd2a transports DHA in the form of lysophosphatidylcholine (LPC), but not unesterified fatty acid, in a sodium-dependent manner. Notably, Mfsd2a transports common plasma LPCs carrying long-chain fatty acids such LPC oleate and LPC palmitate, but not LPCs with less than a 14-carbon acyl chain. Moreover, we determine that the phosphor-zwitterionic headgroup of LPC is critical for transport. Importantly, Mfsd2a-knockout mice have markedly reduced uptake of labelled LPC DHA, and other LPCs, from plasma into brain, demonstrating that Mfsd2a is required for brain uptake of DHA. Our findings reveal an unexpected essential physiological role of plasma-derived LPCs in brain growth and function.

  7. Mfsd2a is a transporter for the essential omega-3 fatty acid docosahexaenoic acid.

    PubMed

    Nguyen, Long N; Ma, Dongliang; Shui, Guanghou; Wong, Peiyan; Cazenave-Gassiot, Amaury; Zhang, Xiaodong; Wenk, Markus R; Goh, Eyleen L K; Silver, David L

    2014-05-22

    Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is essential for normal brain growth and cognitive function. Consistent with its importance in the brain, DHA is highly enriched in brain phospholipids. Despite being an abundant fatty acid in brain phospholipids, DHA cannot be de novo synthesized in brain and must be imported across the blood-brain barrier, but mechanisms for DHA uptake in brain have remained enigmatic. Here we identify a member of the major facilitator superfamily--Mfsd2a (previously an orphan transporter)--as the major transporter for DHA uptake into brain. Mfsd2a is found to be expressed exclusively in endothelium of the blood-brain barrier of micro-vessels. Lipidomic analysis indicates that Mfsd2a-deficient (Mfsd2a-knockout) mice show markedly reduced levels of DHA in brain accompanied by neuronal cell loss in hippocampus and cerebellum, as well as cognitive deficits and severe anxiety, and microcephaly. Unexpectedly, cell-based studies indicate that Mfsd2a transports DHA in the form of lysophosphatidylcholine (LPC), but not unesterified fatty acid, in a sodium-dependent manner. Notably, Mfsd2a transports common plasma LPCs carrying long-chain fatty acids such LPC oleate and LPC palmitate, but not LPCs with less than a 14-carbon acyl chain. Moreover, we determine that the phosphor-zwitterionic headgroup of LPC is critical for transport. Importantly, Mfsd2a-knockout mice have markedly reduced uptake of labelled LPC DHA, and other LPCs, from plasma into brain, demonstrating that Mfsd2a is required for brain uptake of DHA. Our findings reveal an unexpected essential physiological role of plasma-derived LPCs in brain growth and function. PMID:24828044

  8. Application of MS Transport Assays to the Four Human γ-Aminobutyric Acid Transporters.

    PubMed

    Schmitt, Sebastian; Höfner, Georg; Wanner, Klaus T

    2015-09-01

    γ-Aminobutyric acid (GABA) transporters (GATs) are promising drug targets for various diseases associated with imbalances in GABAergic neurotransmission. For the development of new drugs or pharmacological tools addressing GATs, screening techniques to identify new inhibitors and to characterize their potency at each GAT subtype are indispensable. By now, the technique by far dominating is based on radiolabeled GABA. We recently described "MS Transport Assays" for hGAT-1 by employing ((2) H6 )GABA as the substrate. In the present study, we applied this approach to all four human GAT subtypes and determined the KM values for GAT-mediated transport of ((2) H6 )GABA at each subtype. Furthermore, a comprehensive set of GAT inhibitors reflecting the whole range of potency and subtype selectivity known so far was evaluated for their potency. The comparison of pIC50 values obtained in conventional [(3) H]GABA uptake assays with those obtained in MS Transport Assays indicated the reliability of the latter. The MS Transport Assays enable a throughput similar to that of conventional radiometric transport assays performed in a 96-well format but avoid the use of radiolabeled substrates.

  9. Vesicular Inhibitory Amino Acid Transporter Is a Cl−/γ-Aminobutyrate Co-transporter*

    PubMed Central

    Juge, Narinobu; Muroyama, Akiko; Hiasa, Miki; Omote, Hiroshi; Moriyama, Yoshinori

    2009-01-01

    The vesicular inhibitory amino acid transporter (VIAAT) is a synaptic vesicle protein responsible for the vesicular storage of γ-aminobutyrate (GABA) and glycine which plays an essential role in GABAergic and glycinergic neurotransmission. The transport mechanism of VIAAT remains largely unknown. Here, we show that proteoliposomes containing purified VIAAT actively took up GABA upon formation of membrane potential (Δψ) (positive inside) but not ΔpH. VIAAT-mediated GABA uptake had an absolute requirement for Cl− and actually accompanied Cl− movement. Kinetic analysis indicated that one GABA molecule and two Cl− equivalents were transported during one transport cycle. VIAAT in which Glu213 was specifically mutated to alanine completely lost the ability to take up both GABA and Cl−. Essentially the same results were obtained with glycine, another substrate of VIAAT. These results demonstrated that VIAAT is a vesicular Cl− transporter that co-transports Cl− with GABA or glycine in a Δψ dependent manner. It is concluded that Cl− plays an essential role in vesicular storage of GABA and glycine. PMID:19843525

  10. Perfluorocarboxylic acid (PFCA) atmospheric formation and transport to the Arctic.

    NASA Astrophysics Data System (ADS)

    Pike-thackray, C.; Selin, N. E.

    2015-12-01

    Perfluorocarboxylic acids (PFCAs) are highly persistent and toxic environmental contaminants that have been found in remote locations such as the Arctic, far from emission sources. These persistent organic pollutants are emitted directly to the atmosphere as well as being produced by the degradation of precursor compounds in the atmosphere, but recent trends towards increasing precursor emissions and decreasing direct emissions raise the importance of production in the atmosphere. Our work aims to improve understanding of the atmospheric degradation of fluorotelomer precursor compounds to form the long-chain PFCAs PFOA (C8) and PFNA (C9).Using the atmospheric chemical transport model GEOS-Chem, which uses assimilated meteorology to simulate the atmospheric transport of trace gas species, we investigate the interaction of the atmospheric formation of PFCAs and the atmospheric transport of their precursor species. Our simulations are a first application of the GEOS-Chem framework to PFCA chemistry. We highlight the importance of the spatial and temporal variability of background atmospheric chemical conditions experienced during transport. We find that yields and formation times of PFOA and PFNA respond differently and strongly to the photochemical conditions of the atmosphere, such as the abundance of NO, HO2, and other photochemical species.

  11. Effect of plant growth regulators on leaf anatomy of the has mutant of Arabidopsis thaliana.

    PubMed

    Janosević, D; Uzelac, B; Budimir, S

    2008-12-01

    In this study, the effect of plant growth regulators on leaf morphogenesis of the recessive T-DNA insertion mutant of Arabidopsis thaliana was analyzed. The morpho-anatomical analysis revealed that leaves of the has mutant are small and narrow, with lobed blades and disrupted tissue organization. When has plants were grown on the medium supplied with plant growth regulators: benzylaminopurine (BAP) or ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), the leaf anatomy was partially restored to the wild type, although plants still exhibited morphological abnormalities.

  12. A conserved mutation in an ethylene biosynthesis enzyme leads to andromonoecy in melons.

    PubMed

    Boualem, Adnane; Fergany, Mohamed; Fernandez, Ronan; Troadec, Christelle; Martin, Antoine; Morin, Halima; Sari, Marie-Agnes; Collin, Fabrice; Flowers, Jonathan M; Pitrat, Michel; Purugganan, Michael D; Dogimont, Catherine; Bendahmane, Abdelhafid

    2008-08-01

    Andromonoecy is a widespread sexual system in angiosperms characterized by plants carrying both male and bisexual flowers. In melon, this sexual form is controlled by the identity of the alleles at the andromonoecious (a) locus. Cloning of the a gene reveals that andromonoecy results from a mutation in the active site of 1-aminocyclopropane-1-carboxylic acid synthase. Expression of the active enzyme inhibits the development of the male organs and is not required for carpel development. A causal single-nucleotide polymorphism associated with andromonoecy was identified, which suggests that the a allele has been under recent positive selection and may be linked to the evolution of this sexual system.

  13. Regulation of hepatic bile acid transporters Ntcp and Bsep expression

    PubMed Central

    Cheng, Xingguo; Buckley, David; Klaassen, Curtis D.

    2009-01-01

    Sodium-taurocholate cotransporting polypeptide (Ntcp) and bile salt export pump (Bsep) are two key transporters for hepatic bile acid uptake and excretion. Alterations in Ntcp and Bsep expression have been reported in pathophysiological conditions. In the present study, the effects of age, gender, and various chemicals on the regulation of these two transporters were characterized in mice. Ntcp and Bsep mRNA levels in mouse liver were low in the fetus, but increased to its highest expression at parturition. After birth, mouse Ntcp and Bsep mRNA decreased by more than 50%, and then gradually increased to adult levels by day 30. Expression of mouse Ntcp mRNA and protein exhibit higher levels in female than male livers, which is consistent with the trend of human NTCP mRNA expression between men and women. No gender difference exists in BSEP/Bsep expression in human and mouse livers. Hormone replacements conducted in gonadectomized, hypophysectomized, and lit/lit mice indicate that female-predominant Ntcp expression in mouse liver is due to the inhibitory effect of male-pattern GH secretion, but not sex hormones. Ntcp and Bsep expression are in general resistant to induction by a large battery of microsomal enzyme inducers. Administration of cholestyramine increased Ntcp, whereas chenodeoxycholic acid increased Bsep mRNA expression. In silico analysis indicates that female-predominant mouse and human Ntcp/NTCP expression may be due to GH. In conclusion, mouse Ntcp and Bsep are regulated by age, gender, cholestyramine, and bile acid, but resistant to induction by most microsomal enzyme inducers. PMID:17897632

  14. Heteromeric amino acid transporters. In search of the molecular bases of transport cycle mechanisms.

    PubMed

    Palacín, Manuel; Errasti-Murugarren, Ekaitz; Rosell, Albert

    2016-06-15

    Heteromeric amino acid transporters (HATs) are relevant targets for structural studies. On the one hand, HATs are involved in inherited and acquired human pathologies. On the other hand, these molecules are the only known examples of solute transporters composed of two subunits (heavy and light) linked by a disulfide bridge. Unfortunately, structural knowledge of HATs is scarce and limited to the atomic structure of the ectodomain of a heavy subunit (human 4F2hc-ED) and distant prokaryotic homologues of the light subunits that share a LeuT-fold. Recent data on human 4F2hc/LAT2 at nanometer resolution revealed 4F2hc-ED positioned on top of the external loops of the light subunit LAT2. Improved resolution of the structure of HATs, combined with conformational studies, is essential to establish the structural bases for light subunit recognition and to evaluate the functional relevance of heavy and light subunit interactions for the amino acid transport cycle.

  15. Transport of the two natural auxins, indole-3-butyric acid and indole-3-acetic acid, in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Rashotte, Aaron M.; Poupart, Julie; Waddell, Candace S.; Muday, Gloria K.; Brown, C. S. (Principal Investigator)

    2003-01-01

    Polar transport of the natural auxin indole-3-acetic acid (IAA) is important in a number of plant developmental processes. However, few studies have investigated the polar transport of other endogenous auxins, such as indole-3-butyric acid (IBA), in Arabidopsis. This study details the similarities and differences between IBA and IAA transport in several tissues of Arabidopsis. In the inflorescence axis, no significant IBA movement was detected, whereas IAA is transported in a basipetal direction from the meristem tip. In young seedlings, both IBA and IAA were transported only in a basipetal direction in the hypocotyl. In roots, both auxins moved in two distinct polarities and in specific tissues. The kinetics of IBA and IAA transport appear similar, with transport rates of 8 to 10 mm per hour. In addition, IBA transport, like IAA transport, is saturable at high concentrations of auxin, suggesting that IBA transport is protein mediated. Interestingly, IAA efflux inhibitors and mutations in genes encoding putative IAA transport proteins reduce IAA transport but do not alter IBA movement, suggesting that different auxin transport protein complexes are likely to mediate IBA and IAA transport. Finally, the physiological effects of IBA and IAA on hypocotyl elongation under several light conditions were examined and analyzed in the context of the differences in IBA and IAA transport. Together, these results present a detailed picture of IBA transport and provide the basis for a better understanding of the transport of these two endogenous auxins.

  16. Acid rain and transported air pollutants: implications for public policy

    SciTech Connect

    Not Available

    1984-06-01

    Acid rain, ozone, and fine particles in the air are endangering US resources, but controlling these pollutants will be expensive. These air pollutants harm lakes and streams, lower crop yields, damage manmade materials, decrease visibility and pose a threat to forests and human health. The costs to control these pollutants include higher electricity rates, fewer jobs for high-sulfur coal miners and financial strain to utilities and industries. Acid rain and other transported air pollutants pose a special problem for policymakers: how to balance the concerns of those who bear the risk of damage with those who will pay for the control. Scientific uncertainty about many aspects of the problem complicates the decision of whether or when to control. Additional scientific research will not provide an unambiguous answer in the near future, nor will it ever resolve value conflicts. The report synthesizes what is known about pollutant emissions, movements, and effects, and estimates the risk of potential damages to resources. OTA focuses on the public policy implications of the acid rain problems and estimates the costs and potential effectiveness of various control options.

  17. Increased Rat Placental Fatty Acid, but Decreased Amino Acid and Glucose Transporters Potentially Modify Intrauterine Programming.

    PubMed

    Nüsken, Eva; Gellhaus, Alexandra; Kühnel, Elisabeth; Swoboda, Isabelle; Wohlfarth, Maria; Vohlen, Christina; Schneider, Holm; Dötsch, Jörg; Nüsken, Kai-Dietrich

    2016-07-01

    Regulation of placental nutrient transport significantly affects fetal development and may modify intrauterine growth restriction (IUGR) and fetal programming. We hypothesized that placental nutrient transporters are differentially affected both by utero-placental insufficiency and prenatal surgical stress. Pregnant rats underwent bilateral uterine artery and vein ligation (LIG), sham operation (SOP) or no operation (controls, C) on gestational day E19. Placentas were obtained by caesarean section 4 h (LIG, n=20 placentas; SOP, n=24; C, n=12), 24 h (LIG, n=28; SOP, n=20; C, n=12) and 72 h (LIG, n=20; SOP, n=20; C, n=24) after surgery. Gene and protein expression of placental nutrient transporters for fatty acids (h-FABP, CD36), amino acids (SNAT1, SNAT2) and glucose (GLUT-1, Connexin 26) were examined by qRT-PCR, western blot and immunohistochemistry. Interestingly, the mean protein expression of h-FABP was doubled in placentas of LIG and SOP animals 4, 24 (SOP significant) and 72 h (SOP significant) after surgery. CD36 protein was significantly increased in LIG after 72 h. SNAT1 and SNAT2 protein and gene expressions were significantly reduced in LIG and SOP after 24 h. Further significantly reduced proteins were GLUT-1 in LIG (4 h, 72 h) and SOP (24 h), and Connexin 26 in LIG (72 h). In conclusion, placental nutrient transporters are differentially affected both by reduced blood flow and stress, probably modifying the already disturbed intrauterine milieu and contributing to IUGR and fetal programming. Increased fatty acid transport capacity may affect energy metabolism and could be a compensatory reaction with positive effects on brain development. J. Cell. Biochem. 117: 1594-1603, 2016. © 2015 Wiley Periodicals, Inc.

  18. Effects of dibutyryl cyclic AMP and papaverine on intrahepatocytic bile acid transport. Role of vesicle transport.

    PubMed

    Hoshino, M; Ohiwa, T; Hayakawa, T; Kamiya, Y; Tanaka, A; Hirano, A; Kumai, T; Katagiri, K; Miyaji, M; Takeuchi, T

    1993-09-01

    The secondary messenger cyclic AMP plays an important role in regulating biliary excretory function by stimulating the transcytotic vesicle transport system, whereas papaverine exerts an inhibitory effect on this system. We therefore investigated their effects on bile acid-induced cytotoxicity and intrahepatocytic content of bile acid in primary cultured rat hepatocytes. Simultaneous addition of 1 mM dibutyryl cyclic AMP (DBcAMP), an analogue of cAMP, with 1 mM taurochenodeoxycholic acid (TCDCA) significantly decreased the release of lactate dehydrogenase (LDH) as compared with the case with 1 mM TCDCA alone (7.1 +/- 0.13% of total versus 10.7 +/- 0.3%). In contrast, 0.1 mM papaverine approximately doubled the amount of LDH (22.0 +/- 0.6% of total versus 10.7 +/- 0.3%; P < 0.01). The intracellular content of TCDCA 180 min after the administration of 1 mM TCDCA alone was 20.8 +/- 0.7 nmol/mg protein, that after simultaneous administration of 1 mM DBcAMP, 16.2 +/- 1.0 nmol/mg protein, and that after the simultaneous administration of 0.1 mM papaverine, 38.5 +/- 1.9 nmol/mg protein. A clear correlation between the release of LDH from hepatocytes and the intracellular content of TCDCA was thus observed. When given together with 1 mM taurocholic acid (TCA) or 1 mM tauroursodeoxycholic acid (TUDCA), papaverine exerted little effect on cytotoxicity or intrahepatocytic bile acid content. When cells were bathed in a medium free of bile acid after pretreatment with 1 mM TCDCA and 1 mM DBcAMP, additional exposure to DBcAMP for 30 min significantly stimulated reduction of intracellular TCDCA content (30.2 +/- 0.4% of total versus 44.0 +/- 1.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Amino Acid Transporters and Release of Hydrophobic Amino Acids in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120.

    PubMed

    Pernil, Rafael; Picossi, Silvia; Herrero, Antonia; Flores, Enrique; Mariscal, Vicente

    2015-04-23

    Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can use inorganic compounds such as nitrate or ammonium as nitrogen sources. In the absence of combined nitrogen, it can fix N2 in differentiated cells called heterocysts. Anabaena also shows substantial activities of amino acid uptake, and three ABC-type transporters for amino acids have been previously characterized. Seven new loci encoding predicted amino acid transporters were identified in the Anabaena genomic sequence and inactivated. Two of them were involved in amino acid uptake. Locus alr2535-alr2541 encodes the elements of a hydrophobic amino acid ABC-type transporter that is mainly involved in the uptake of glycine. ORF all0342 encodes a putative transporter from the dicarboxylate/amino acid:cation symporter (DAACS) family whose inactivation resulted in an increased uptake of a broad range of amino acids. An assay to study amino acid release from Anabaena filaments to the external medium was set up. Net release of the alanine analogue α-aminoisobutyric acid (AIB) was observed when transport system N-I (a hydrophobic amino acid ABC-type transporter) was engaged in the uptake of a specific substrate. The rate of AIB release was directly proportional to the intracellular AIB concentration, suggesting leakage from the cells by diffusion.

  20. Amino Acid Transporters and Release of Hydrophobic Amino Acids in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

    PubMed Central

    Pernil, Rafael; Picossi, Silvia; Herrero, Antonia; Flores, Enrique; Mariscal, Vicente

    2015-01-01

    Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can use inorganic compounds such as nitrate or ammonium as nitrogen sources. In the absence of combined nitrogen, it can fix N2 in differentiated cells called heterocysts. Anabaena also shows substantial activities of amino acid uptake, and three ABC-type transporters for amino acids have been previously characterized. Seven new loci encoding predicted amino acid transporters were identified in the Anabaena genomic sequence and inactivated. Two of them were involved in amino acid uptake. Locus alr2535-alr2541 encodes the elements of a hydrophobic amino acid ABC-type transporter that is mainly involved in the uptake of glycine. ORF all0342 encodes a putative transporter from the dicarboxylate/amino acid:cation symporter (DAACS) family whose inactivation resulted in an increased uptake of a broad range of amino acids. An assay to study amino acid release from Anabaena filaments to the external medium was set up. Net release of the alanine analogue α-aminoisobutyric acid (AIB) was observed when transport system N-I (a hydrophobic amino acid ABC-type transporter) was engaged in the uptake of a specific substrate. The rate of AIB release was directly proportional to the intracellular AIB concentration, suggesting leakage from the cells by diffusion. PMID:25915115

  1. Amino Acid Transporters and Release of Hydrophobic Amino Acids in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120.

    PubMed

    Pernil, Rafael; Picossi, Silvia; Herrero, Antonia; Flores, Enrique; Mariscal, Vicente

    2015-01-01

    Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can use inorganic compounds such as nitrate or ammonium as nitrogen sources. In the absence of combined nitrogen, it can fix N2 in differentiated cells called heterocysts. Anabaena also shows substantial activities of amino acid uptake, and three ABC-type transporters for amino acids have been previously characterized. Seven new loci encoding predicted amino acid transporters were identified in the Anabaena genomic sequence and inactivated. Two of them were involved in amino acid uptake. Locus alr2535-alr2541 encodes the elements of a hydrophobic amino acid ABC-type transporter that is mainly involved in the uptake of glycine. ORF all0342 encodes a putative transporter from the dicarboxylate/amino acid:cation symporter (DAACS) family whose inactivation resulted in an increased uptake of a broad range of amino acids. An assay to study amino acid release from Anabaena filaments to the external medium was set up. Net release of the alanine analogue α-aminoisobutyric acid (AIB) was observed when transport system N-I (a hydrophobic amino acid ABC-type transporter) was engaged in the uptake of a specific substrate. The rate of AIB release was directly proportional to the intracellular AIB concentration, suggesting leakage from the cells by diffusion. PMID:25915115

  2. Induction of amino acid transporters expression by endurance exercise in rat skeletal muscle

    SciTech Connect

    Murakami, Taro Yoshinaga, Mariko

    2013-10-04

    Highlights: •Regulation of amino acid transporter expression in working muscle remains unclear. •Expression of amino acid transporters for leucine were induced by a bout of exercise. •Requirement of leucine in muscle cells might regulate expression of its transporters. •This information is beneficial for understanding the muscle remodeling by exercise. -- Abstract: We here investigated whether an acute bout of endurance exercise would induce the expression of amino acid transporters that regulate leucine transport across plasma and lysosomal membranes in rat skeletal muscle. Rats ran on a motor-driven treadmill at a speed of 28 m/min for 90 min. Immediately after the exercise, we observed that expression of mRNAs encoding L-type amino acid transporter 1 (LAT1) and CD98 was induced in the gastrocnemius, soleus, and extensor digitorum longus (EDL) muscles. Sodium-coupled neutral amino acid transporter 2 (SNAT2) mRNA was also induced by the exercise in those three muscles. Expression of proton-assisted amino acid transporter 1 (PAT1) mRNA was slightly but not significantly induced by a single bout of exercise in soleus and EDL muscles. Exercise-induced mRNA expression of these amino acid transporters appeared to be attenuated by repeated bouts of the exercise. These results suggested that the expression of amino acid transporters for leucine may be induced in response to an increase in the requirement for this amino acid in the cells of working skeletal muscles.

  3. Electrical Transport Properties of Au-Doped Deoxyribonucleic Acid Molecules

    NASA Astrophysics Data System (ADS)

    Hwang, Jong Seung; Hong, Su Heon; Kim, Hyung Kwon; Kwon, Young Whan; Jin, Jung Il; Hwang, Sung Woo; Ahn, Doyeol

    2005-04-01

    Deoxyribonucleic acid (DNA) molecules were doped with Au atoms and their electrical transport properties were measured. The Au doping was carried out by incubating a mixture of HAuCl4\\cdot3H2O and DNA solutions. The binding of Au atoms to DNA bases was identified using Fourier transform infrared spectroscopy and X-ray photoemission spectroscopy. The Au-doped DNA molecules were deposited on nanoelectrodes and the presence of the molecules between the electrodes was determined by both scanning electron microscopy and atomic force microscopy. Measurement of the current-voltage characteristics showed that the Au-doped DNA molecules exhibited a higher conductivity than undoped DNA molecules. Detailed analysis of the chemical composition shows that there is a strong possibility of reliably controlling the conductivity of DNA molecules using this method.

  4. Acid-base transport by the renal proximal tubule

    PubMed Central

    Skelton, Lara A.; Boron, Walter F.; Zhou, Yuehan

    2015-01-01

    Each day, the kidneys filter 180 L of blood plasma, equating to some 4,300 mmol of the major blood buffer, bicarbonate (HCO3−). The glomerular filtrate enters the lumen of the proximal tubule (PT), and the majority of filtered HCO3− is reclaimed along the early (S1) and convoluted (S2) portions of the PT in a manner coupled to the secretion of H+ into the lumen. The PT also uses the secreted H+ to titrate non-HCO3− buffers in the lumen, in the process creating “new HCO3−” for transport into the blood. Thus, the PT – along with more distal renal segments – is largely responsible for regulating plasma [HCO3−]. In this review we first focus on the milestone discoveries over the past 50+ years that define the mechanism and regulation of acid-base transport by the proximal tubule. Further on in the review, we will summarize research still in progress from our laboratory, work that addresses the problem of how the PT is able to finely adapt to acid–base disturbances by rapidly sensing changes in basolateral levels of HCO3− and CO2 (but not pH), and thereby to exert tight control over the acid–base composition of the blood plasma. PMID:21170887

  5. Butyric acid increases transepithelial transport of ferulic acid through upregulation of the monocarboxylate transporters SLC16A1 (MCT1) and SLC16A3 (MCT4).

    PubMed

    Ziegler, Kerstin; Kerimi, Asimina; Poquet, Laure; Williamson, Gary

    2016-06-01

    Ferulic acid is released by microbial hydrolysis in the colon, where butyric acid, a major by-product of fermentation, constitutes the main energy source for colonic enterocytes. We investigated how varying concentrations of this short chain fatty acid may influence the absorption of the phenolic acid. Chronic treatment of Caco-2 cells with butyric acid resulted in increased mRNA and protein abundance of the monocarboxylate transporters SLC16A1 (MCT1) and SLC16A3 (MCT4), previously proposed to facilitate ferulic acid absorption in addition to passive diffusion. Short term incubation with butyric acid only led to upregulation of MCT4 while both conditions increased transepithelial transport of ferulic acid in the apical to basolateral, but not basolateral to apical, direction. Chronic treatment also elevated intracellular concentrations of ferulic acid, which in turn gave rise to increased concentrations of ferulic acid metabolites. Immunofluorescence staining of cells revealed uniform distribution of MCT1 protein in the cell membrane, whereas MCT4 was only detected in the lateral plasma membrane sections of Caco-2 cells. We therefore propose that MCT1 may be acting as an uptake transporter and MCT4 as an efflux system across the basolateral membrane for ferulic acid, and that this process is stimulated by butyric acid. PMID:26854723

  6. The D-amino acid transport by the invertebrate SLC6 transporters KAAT1 and CAATCH1 from Manduca sexta.

    PubMed

    Vollero, Alessandra; Imperiali, Francesca G; Cinquetti, Raffaella; Margheritis, Eleonora; Peres, Antonio; Bossi, Elena

    2016-02-01

    The ability of the SLC6 family members, the insect neutral amino acid cotransporter KAAT1(K(+)-coupled amino acid transporter 1) and its homologous CAATCH1(cation anion activated amino acid transporter/channel), to transport D-amino acids has been investigated through heterologous expression in Xenopus laevis oocytes and electrophysiological techniques. In the presence of D-isomers of leucine, serine, and proline, the msKAAT1 generates inward, transport-associated, currents with variable relative potencies, depending on the driving ion Na(+) or K(+). Higher concentrations of D-leucine (≥1 mmol/L) give rise to an anomalous response that suggests the existence of a second binding site with inhibitory action on the transport process. msCAATCH1 is also able to transport the D-amino acids tested, including D-leucine, whereas L-leucine acts as a blocker. A similar behavior is exhibited by the KAAT1 mutant S308T, confirming the relevance of the residue in this position in L-leucine binding and the different interaction of D-leucine with residues involved in transport mechanism. D-leucine and D-serine on various vertebrate orthologs B(0)AT1 (SLC6A19) elicited only a very small current and singular behavior was not observed, indicating that it is specific of the insect neutral amino acid transporters. These findings highlight the relevance of D-amino acid absorption in the insect nutrition and metabolism and may provide new evidences in the molecular transport mechanism of SLC6 family. PMID:26884475

  7. Intestinal transport of zinc and folic acid: a mutual inhibitory effect

    SciTech Connect

    Ghishan, F.K.; Said, H.M.; Wilson, P.C.; Murrell, J.E.; Greene, H.L.

    1986-02-01

    Recent observations suggest an inverse relationship between folic acid intake and zinc nutriture and indicate an interaction between folic acid and zinc at the intestinal level. To define that interaction, we designed in vivo and in vitro transport studies in which folic acid transport in the presence of zinc, as well as zinc transport in the presence of folic acid was examined. These studies show that zinc transport is significantly decreased when folate is present in the intestinal lumen. Similarly folic acid transport is significantly decreased with the presence of zinc. To determine whether this intestinal inhibition is secondary to zinc and folate-forming complexes, charcoal-binding studies were performed. These studies indicate that zinc and folate from complexes at pH 2.0, but that at pH 6.0, these complexes dissolve. Therefore, our studies suggest that under normal physiological conditions a mutual inhibition between folate and zinc exists at the site of intestinal transport.

  8. Reactive Transport Modeling of Acid Gas Generation and Condensation

    SciTech Connect

    G. Zhahg; N. Spycher; E. Sonnenthal; C. Steefel

    2005-01-25

    Pulvirenti et al. (2004) recently conducted a laboratory evaporation/condensation experiment on a synthetic solution of primarily calcium chloride. This solution represents one potential type of evaporated pore water at Yucca Mountain, Nevada, a site proposed for geologic storage of high-level nuclear waste. These authors reported that boiling this solution to near dryness (a concentration factor >75,000 relative to actual pore waters) leads to the generation of acid condensate (pH 4.5) presumably due to volatilization of HCl (and minor HF and/or HNO{sub 3}). To investigate the various processes taking place, including boiling, gas transport, and condensation, their experiment was simulated by modifying an existing multicomponent and multiphase reactive transport code (TOUGHREACT). This code was extended with a Pitzer ion-interaction model to deal with high ionic strength. The model of the experiment was set-up to capture the observed increase in boiling temperature (143 C at {approx}1 bar) resulting from high concentrations of dissolved salts (up to 8 m CaCl{sub 2}). The computed HCI fugacity ({approx} 10{sup -4} bars) generated by boiling under these conditions is not sufficient to lower the pH of the condensate (cooled to 80 and 25 C) down to observed values unless the H{sub 2}O mass fraction in gas is reduced below {approx}10%. This is because the condensate becomes progressively diluted by H{sub 2}O gas condensation. However, when the system is modeled to remove water vapor, the computed pH of instantaneous condensates decreases to {approx}1.7, consistent with the experiment (Figure 1). The results also show that the HCl fugacity increases, and calcite, gypsum, sylvite, halite, MgCl{sub 2}4H{sub 2}O and CaCl{sub 2} precipitate sequentially with increasing concentration factors.

  9. L-aspartic acid transport by cat erythrocytes

    SciTech Connect

    Chen, C.W.; Preston, R.L.

    1986-03-01

    Cat and dog red cells are unusual in that they have no Na/K ATPase and contain low K and high Na intracellularly. They also show significant Na dependent L-aspartate (L-asp) transport. The authors have characterized this system in cat RBCs. The influx of /sup 3/H-L-asp (typically 2..mu..M) was measured in washed RBCs incubated for 60 s at 37/sup 0/C in medium containing 140 mM NaCl, 5 mM Kcl, 2 mM CaCl/sub 2/, 15 mM MOPS pH 7.4, 5 mM glucose, and /sup 14/C-PEG as a space marker. The cells were washed 3 times in the medium immediately before incubation which was terminated by centrifuging the RBCs through a layer of dibutylphthalate. Over an L-asp concentration range of 0.5-1000..mu..M, influx obeyed Michaelis-Menten kinetics with a small added linear diffusion component. The Kt and Jmax of the saturable component were 5.40 +/- 0.34 ..mu..M and 148.8 +/- 7.2 ..mu..mol 1. cell/sup -1/h/sup -1/ respectively. Replacement of Na with Li, K, Rb, Cs or choline reduce influx to diffusion. With the addition of asp analogues (4/sup +/M L-asp, 40/sup +/M inhibitor), the following sequence of inhibition was observed (range 80% to 40% inhib.): L-glutamate > L-cysteine sulfonate > D-asp > L-cysteic acid > D-glutamate. Other amino acids such as L-alanine, L-proline, L-lysine, L-cysteine, and taurine showed no inhibition (<5%). These data suggest that cat red cells contain a high-affinity Na dependent transport system for L-asp, glutamate, and closely related analogues which resembles that found in the RBCs of other carnivores and in neural tissues.

  10. Designing Novel Nanoformulations Targeting Glutamate Transporter Excitatory Amino Acid Transporter 2: Implications in Treating Drug Addiction

    PubMed Central

    Rao, PSS; Yallapu, Murali M.; Sari, Youssef; Fisher, Paul B.; Kumar, Santosh

    2015-01-01

    Chronic drug abuse is associated with elevated extracellular glutamate concentration in the brain reward regions. Deficit of glutamate clearance has been identified as a contributing factor that leads to enhanced glutamate concentration following extended drug abuse. Importantly, normalization of glutamate level through induction of glutamate transporter 1 (GLT1)/ excitatory amino acid transporter 2 (EAAT2) expression has been described in several in vivo studies. GLT1 upregulators including ceftriaxone, a beta-lactam antibiotic, have been effective in attenuating drug-seeking and drug-consumption behavior in rodent models. However, potential obstacles toward clinical translation of GLT1 (EAAT2) upregulators as treatment for drug addiction might include poor gastrointestinal absorption, serious peripheral adverse effects, and/or suboptimal CNS concentrations. Given the growing success of nanotechnology in targeting CNS ailments, nanoformulating known GLT1 (EAAT2) upregulators for selective uptake across the blood brain barrier presents an ideal therapeutic approach for treating drug addiction. In this review, we summarize the results obtained with promising GLT1 (EAAT2) inducing compounds in animal models recapitulating drug addiction. Additionally, the various nanoformulations that can be employed for selectively increasing the CNS bioavailability of GLT1 (EAAT2) upregulators are discussed. Finally, the applicability of GLT1 (EAAT2) induction via central delivery of drug-loaded nanoformulations is described. PMID:26635971

  11. Regulatory signals for intestinal amino acid transporters and peptidases

    SciTech Connect

    Ferraris, R.P.; Kwan, W.W.; Diamond, J. )

    1988-08-01

    Dietary protein ultimately regulates many processes involved in protein digestion, but it is often unclear whether proteins themselves, peptides, or amino acids (AAs) are the proximate regulatory signal. Hence the authors compared several processes involved in protein digestion in mice adapted to one of three rations, identical except for containing 54% of either casein, a partial hydrolysate of casein, or a free AA mixture simulating a complete hydrolysate of casein. The authors measured brush-border uptakes of seven AAs that variously serve as substrates for four AA transporters, and brush-border and cytosolic activities of four peptidases. The three rations yielded essentially the same AA uptake rates. Peptidase activities tended to be lower on the AA ration than on the protein ration. In other studies, all three rations yielded the same rates of brush-border peptide uptake; protein is only modestly more effective than AAs at inducing synthesis of pancreatic proteases; and, depending on the animal species, protein is either much less or much more effective than AAs at stimulating release of cholecystokinin and hence of pancreatic enzymes. Thus the regulators of each process involved in protein digestion are not necessarily that process's substrate.

  12. Fatty Acid-Binding Protein 5 Facilitates the Blood-Brain Barrier Transport of Docosahexaenoic Acid.

    PubMed

    Pan, Yijun; Scanlon, Martin J; Owada, Yuji; Yamamoto, Yui; Porter, Christopher J H; Nicolazzo, Joseph A

    2015-12-01

    The brain has a limited ability to synthesize the essential polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA) from its omega-3 fatty acid precursors. Therefore, to maintain brain concentrations of this PUFA at physiological levels, plasma-derived DHA must be transported across the blood-brain barrier (BBB). While DHA is able to partition into the luminal membrane of brain endothelial cells, its low aqueous solubility likely limits its cytosolic transfer to the abluminal membrane, necessitating the requirement of an intracellular carrier protein to facilitate trafficking of this PUFA across the BBB. As the intracellular carrier protein fatty acid-binding protein 5 (FABP5) is expressed at the human BBB, the current study assessed the putative role of FABP5 in the brain endothelial cell uptake and BBB transport of DHA in vitro and in vivo, respectively. hFAPB5 was recombinantly expressed and purified from Escherichia coli C41(DE3) cells and the binding affinity of DHA to hFABP5 assessed using isothermal titration calorimetry. The impact of FABP5 siRNA on uptake of (14)C-DHA into immortalized human brain microvascular endothelial (hCMEC/D3) cells was assessed. An in situ transcardiac perfusion method was optimized in C57BL/6 mice and subsequently used to compare the BBB influx rate (Kin) of (14)C-DHA between FABP5-deficient (FABP5(-/-)) and wild-type (FABP5(+/+)) C57BL/6 mice. DHA bound to hFABP5 with an equilibrium dissociation constant of 155 ± 8 nM (mean ± SEM). FABP5 siRNA transfection decreased hCMEC/D3 mRNA and protein expression of FABP5 by 53.2 ± 5.5% and 44.8 ± 13.7%, respectively, which was associated with a 14.1 ± 2.7% reduction in (14)C-DHA cellular uptake. By using optimized conditions for the in situ transcardiac perfusion (a 1 min preperfusion (10 mL/min) followed by perfusion of (14)C-DHA (1 min)), the Kin of (14)C-DHA was 0.04 ± 0.01 mL/g/s. Relative to FABP5(+/+) mice, the Kin of (14)C-DHA decreased 36.7 ± 12.4% in FABP5(-/-) mice

  13. Transport mechanism and regulatory properties of the human amino acid transporter ASCT2 (SLC1A5).

    PubMed

    Scalise, Mariafrancesca; Pochini, Lorena; Panni, Simona; Pingitore, Piero; Hedfalk, Kristina; Indiveri, Cesare

    2014-11-01

    The kinetic mechanism of the transport catalyzed by the human glutamine/neutral amino acid transporter hASCT2 over-expressed in P. pastoris was determined in proteoliposomes by pseudo-bi-substrate kinetic analysis of the Na(+)-glutamineex/glutaminein transport reaction. A random simultaneous mechanism resulted from the experimental analysis. Purified functional hASCT2 was chemically cross-linked to a stable dimeric form. The oligomeric structure correlated well with the kinetic mechanism of transport. Half-saturation constants (Km) of the transporter for the other substrates Ala, Ser, Asn and Thr were measured both on the external and internal side. External Km were much lower than the internal ones confirming the asymmetry of the transporter. The electric nature of the transport reaction was determined imposing a negative inside membrane potential generated by K(+) gradients in the presence of valinomycin. The transport reaction resulted to be electrogenic and the electrogenicity originated from external Na(+). Internal Na(+) exerted a stimulatory effect on the transport activity which could be explained by a regulatory, not a counter-transport, effect. Native and deglycosylated hASCT2 extracted from HeLa showed the same transport features demonstrating that the glycosyl moiety has no role in transport function. Both in vitro and in vivo interactions of hASCT2 with the scaffold protein PDZK1 were revealed.

  14. Intracellular boron accumulation in CHO-K1 cells using amino acid transport control.

    PubMed

    Sato, Eisuke; Yamamoto, Tetsuya; Shikano, Naoto; Ogura, Masato; Nakai, Kei; Yoshida, Fumiyo; Uemae, Yoji; Takada, Tomoya; Isobe, Tomonori; Matsumura, Akira

    2014-06-01

    BPA used in BNCT has a similar structure to some essential amino acids and is transported into tumor cells by amino acid transport systems. Previous study groups have tried various techniques of loading BPA to increase intracellular boron concentration. CHO-K1 cells demonstrate system L (LAT1) activity and are suitable for specifying the transport system of a neutral amino acid. In this study, we examined the intracellular accumulation of boron in CHO-K1 cells by amino acid transport control, which involves co-loading with L-type amino acid esters. Intracellular boron accumulation in CHO-K1 cells showed the greatest increased upon co-loading 1.0mM BPA, with 1.0mM l-Tyr-O-Et and incubating for 60min. This increase is caused by activation of a system L amino acid exchanger between BPA and l-Tyr. The amino acid esters are metabolized to amino acids by intracellular hydrolytic enzymes that increase the concentrations of intracellular amino acids and stimulate exchange transportation. We expect that this amino acid transport control will be useful for enhancing intracellular boron accumulation.

  15. The SLC32 transporter, a key protein for the synaptic release of inhibitory amino acids.

    PubMed

    Gasnier, Bruno

    2004-02-01

    The SLC32 family comprises a single member: the vesicular inhibitory amino acid transporter (VIAAT) or vesicular GABA transporter (VGAT). It belongs to a eukaryotic-specific superfamily of H(+)-coupled amino acid transporters, which also comprises the mammalian SLC36 and SLC38 transporters. VIAAT exchanges GABA or glycine for protons. It is present on synaptic vesicles of GABAergic and glycinergic neurons, and in some endocrine cells, where it ensures the H(+)-ATPase-driven uptake, and subsequent exocytotic release, of inhibitory amino acids. Despite a similar function in vesicular neurotransmitter loading, VIAAT is not related to the vesicular glutamate transporter (VGLUT, SLC17) or the vesicular monoamine transporter/vesicular acetylcholine transporter (VMAT/VACHT, SLC18) proteins.

  16. Adsorption and transport of polymaleic acid on Callovo-Oxfordian clay stone: Batch and transport experiments

    NASA Astrophysics Data System (ADS)

    Durce, Delphine; Landesman, Catherine; Grambow, Bernd; Ribet, Solange; Giffaut, Eric

    2014-08-01

    Dissolved Organic Matter (DOM) can affect the mobility of radionuclides in pore water of clay-rich geological formations, such as those intended to be used for nuclear waste disposal. The present work studies the adsorption and transport properties of a polycarboxylic acid, polymaleic acid (PMA, Mw = 1.9 kDa), on Callovo-Oxfordian argillite samples (COx). Even though this molecule is rather different from the natural organic matter found in clay rock, the study of its retention properties on both dispersed and intact samples allows assessing to which extent organic acids may undergo sorption under natural conditions (pH 7) and what could be the impact on their mobility. PMA sorption and desorption were investigated in dispersed systems. The degree of sorption was measured after 1, 8 and 21 days and for a range of PMA initial concentrations from 4.5 × 10- 7 to 1.4 × 10- 3 mol.L- 1. The reversibility of the sorption process was estimated by desorption experiments performed after the sorption experiments. At the sorption steady state, the sorption was described by a two-site Langmuir model. A total sorption capacity of COx for PMA was found to be 1.01×10- 2 mol.kg- 1 distributed on two sorption sites, one weak and one strong. The desorption of PMA was incomplete, independently of the duration of the sorption phase. The amount of desorbable PMA even appeared to decrease for sorption phases from 1 to 21 days. To describe the apparent desorption hysteresis, two conceptual models were applied. The two-box diffusion model accounted for intraparticle diffusion and more generally for nonequilibrium processes. The two-box first-order non-reversible model accounted for a first-order non-reversible sorption and more generally for kinetically-controlled irreversible sorption processes. The use of the two models revealed that desorption hysteresis was not the result of nonequilibrium processes but was due to irreversible sorption. Irreversible sorption on the strong site was

  17. Transport and catabolism of the sialic acids N-glycolylneuraminic acid and 3-keto-3-deoxy-D-glycero-D-galactonononic acid by Escherichia coli K-12.

    PubMed

    Hopkins, Adam P; Hawkhead, Judith A; Thomas, Gavin H

    2013-10-01

    Escherichia coli can transport and catabolize the common sialic acid, N-acetylneuraminic acid (Neu5Ac), as a sole source of carbon and nitrogen, which is an important mucus-derived carbon source in the mammalian gut. Herein we demonstrate that E. coli can also grow efficiently on the related sialic acids, N-glycolylneuraminic acid (Neu5Gc) and 3-keto-3-deoxy-D-glycero-D-galactonononic acid (KDN), which are transported via the sialic acid transporter NanT and catabolized using the sialic acid aldolase NanA. Catabolism of Neu5Gc uses the same pathway as Neu5Ac, likely producing glycolate instead and acetate during its breakdown and catabolism of KDN requires NanA activity, while other components of the Neu5Ac catabolism pathway are non-essential. We also demonstrate that these two sialic acids can support growth of an E. coli ∆nanT strain expressing sialic acid transporters from two bacterial pathogens, namely the tripartite ATP-independent periplasmic transporter SiaPQM from Haemophilus influenzae and the sodium solute symport transporter STM1128 from Salmonella enterica ssp. Typhimurium, suggesting that the ability to use Neu5Gc and KDN in addition to Neu5Ac is present in a number of human pathogens.

  18. Transporters in Arabidopsis roots mediating uptake of amino acids at naturally occurring concentrations.

    PubMed

    Svennerstam, Henrik; Jämtgård, Sandra; Ahmad, Iftikhar; Huss-Danell, Kerstin; Näsholm, Torgny; Ganeteg, Ulrika

    2011-07-01

    Recent studies of Arabidopsis have identified several transporters as being important for amino acid uptake. We used Arabidopsis plants with altered expression of lysine histidine transporter 1 (LHT1), amino acid permease 1 (AAP1) and amino acid permease 5 (AAP5) with the aim of disentangling the roles of each transporter in the uptake of different amino acids at naturally occurring concentrations (2-50 μM). LHT1 mutants displayed reduced uptake rates of L-Gln, L-Ala, L-Glu and L-Asp but not of L-Arg or L-Lys, while AAP5 mutants were affected in the uptake of L-Arg and L-Lys only. Double mutants (lht1aap5) exhibited reduced uptake of all tested amino acids. In the concentration range tested, AAP1 mutants did not display altered uptake rates for any of the studied amino acids. Expression analysis of amino acid transporter genes with important root functions revealed no major differences in the individual mutants other than for genes targeted for mutation. We conclude that LHT1 and AAP5, but not AAP1, are crucial for amino acid uptake at concentrations typically found in soils. LHT1 and AAP5 displayed complementary affinity spectra, and no redundancy with respect to gene expression was found between the two transporters, suggesting these two transporters have separate roles in amino acid uptake.

  19. Identification and characterization of an amino acid transporter expressed differentially in liver

    PubMed Central

    Gu, Sumin; Roderick, Hywel Llewelyn; Camacho, Patricia; Jiang, Jean X.

    2000-01-01

    Cellular metabolic needs are fulfilled by transport of amino acids across the plasma membrane by means of specialized transporter proteins. Although many of the classical amino acid transporters have been characterized functionally, less than half of these proteins have been cloned. In this report, we identify and characterize a cDNA encoding a plasma membrane amino acid transporter. The deduced amino acid sequence is 505 residues and is highly hydrophobic with the likely predicted structure of 9 transmembrane domains, which putatively place the amino terminus in the cytoplasm and the carboxy terminus on the cell surface. Expression of the cRNA in Xenopus laevis oocytes revealed strong transport activities specific for histidine and glutamine. This protein is a Na+- and pH-dependent transporter and tolerates substitution of Na+ by Li+. Furthermore, this transporter is not an obligatory exchanger because efflux occurs in the absence of influx. This transporter is expressed predominantly in the liver, although it is also present in the kidney, brain, and heart. In the liver, it is located in the plasma membrane of hepatocytes, and the strongest expression was detected in those adjacent to the central vein, gradually decreasing towards the portal tract. Because this protein displays functional similarities to the N-system amino acid transport, we have termed it mNAT, for murine N-system amino acid transporter. This is the first transporter gene identified within the N-system, one of the major amino acid transport systems in the body. The expression pattern displayed by mNAT suggests a potential role in hepatocyte physiology. PMID:10716701

  20. Mitochondrial transporters involved in oleic acid utilization and glutamate metabolism in yeast.

    PubMed

    Trotter, Pamela J; Adamson, Amy L; Ghrist, Angela C; Rowe, Lindsay; Scott, Lori R; Sherman, Matthew P; Stites, Nicole C; Sun, Yue; Tawiah-Boateng, Mary Anne; Tibbetts, Anne S; Wadington, Megan C; West, Aaron C

    2005-10-01

    Utilization of fatty acids such as oleic acid as sole carbon source by the yeast Saccharomyces cerevisiae requires coordinated function of peroxisomes, where the fatty acids are degraded, and the mitochondria, where oxidation is completed. We identified two mitochondrial oxodicarboxylate transporters, Odc1p and Odc2p, as important in efficient utilization of oleic acid in yeast [Tibbetts et al., Arch. Biochem. Biophys. 406 (2002) 96-104]. Yet, the growth phenotype of odc1delta odc2delta strains indicated that additional transporter(s) were also involved. Here, we identify two putative transporter genes, YMC1 and YMC2, as able to suppress the odc1delta odc2delta growth phenotype. The mRNA levels for both are elevated in the presence of glycerol or oleic acid, as compared to glucose. Ymc1p and Ymc2p are localized to the mitochondria in oleic acid-grown cells. Deletion of all four transporters (quad mutant) prevents growth on oleic acid as sole carbon source, while growth on acetate is retained. It is known that the glutamate-sensitive retrograde signaling pathway is important for upregulation of peroxisomal function in response to oleic acid and the oxodicarboxylate alpha-ketoglutarate is transported out of the mitochondria for synthesis of glutamate. So, citric acid cycle function and glutamate synthesis were examined in transporter mutants. The quad mutant has significantly decreased citrate synthase activity and whole cell alpha-ketoglutarate levels, while isocitrate dehydrogenase activity is unaffected and glutamate dehydrogenase activity is increased 10-fold. Strains carrying only two or three transporter deletions exhibit intermediate affects. 13C NMR metabolic enrichment experiments confirm a defect in glutamate biosynthesis in the quad mutant and, in double and triple mutants, suggest increased cycling of the glutamate backbone in the mitochondria before export. Taken together these studies indicate that these four transporters have overlapping activity, and

  1. Transporter-targeted cholic acid-cytarabine conjugates for improved oral absorption.

    PubMed

    Zhang, Dong; Li, Dongpo; Shang, Lei; He, Zhonggui; Sun, Jin

    2016-09-10

    Cytarabine has a poor oral absorption due to its rapid deamination and poor membrane permeability. Bile acid transporters are highly expressed both in enterocytes and hepatocytes and to increase the oral bioavailability and investigate the potential application of cytarabine for liver cancers, a transporter- recognizing prodrug strategy was applied to design and synthesize four conjugates of cytarabine with cholic acid (CA), chenodeoxycholic acid (CDCA), hyodeoxycholic acid (HDCA) and ursodeoxycholic acid (UDCA). The anticancer activities against HepG2 cells were evaluated by MTT assay and the role of bile acid transporters during cellular transport was investigated in a competitive inhibition experiment. The in vitro and in vivo metabolic stabilities of these conjugates were studied in rat plasma and liver homogenates. Finally, an oral bioavailability study was conducted in rats. All the cholic acid-cytarabine conjugates (40μM) showed potent antiproliferative activities (up to 70%) against HepG2 cells after incubation for 48h. The addition of bile acids could markedly reduce the antitumor activities of these conjugates. The N(4)-ursodeoxycholic acid conjugate of cytarabine (compound 5) exhibited optimal stability (t1/2=90min) in vitro and a 3.9-fold prolonged half-life of cytarabine in vivo. More importantly, compound 5 increased the oral bioavailability 2-fold compared with cytarabine. The results of the present study suggest that the prodrug strategy based on the bile acid transporters is suitable for improving the oral absorption and the clinical application of cytarabine. PMID:27377011

  2. Auxin and Ethylene Induce Flavonol Accumulation through Distinct Transcriptional Networks1[C][W][OA

    PubMed Central

    Lewis, Daniel R.; Ramirez, Melissa V.; Miller, Nathan D.; Vallabhaneni, Prashanthi; Ray, W. Keith; Helm, Richard F.; Winkel, Brenda S.J.; Muday, Gloria K.

    2011-01-01

    Auxin and ethylene are key regulators of plant growth and development, and thus the transcriptional networks that mediate responses to these hormones have been the subject of intense research. This study dissected the hormonal cross talk regulating the synthesis of flavonols and examined their impact on root growth and development. We analyzed the effects of auxin and an ethylene precursor on roots of wild-type and hormone-insensitive Arabidopsis (Arabidopsis thaliana) mutants at the transcript, protein, and metabolite levels at high spatial and temporal resolution. Indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) differentially increased flavonol pathway transcripts and flavonol accumulation, altering the relative abundance of quercetin and kaempferol. The IAA, but not ACC, response is lost in the transport inhibitor response1 (tir1) auxin receptor mutant, while ACC responses, but not IAA responses, are lost in ethylene insensitive2 (ein2) and ethylene resistant1 (etr1) ethylene signaling mutants. A kinetic analysis identified increases in transcripts encoding the transcriptional regulators MYB12, Transparent Testa Glabra1, and Production of Anthocyanin Pigment after hormone treatments, which preceded increases in transcripts encoding flavonoid biosynthetic enzymes. In addition, myb12 mutants were insensitive to the effects of auxin and ethylene on flavonol metabolism. The equivalent phenotypes for transparent testa4 (tt4), which makes no flavonols, and tt7, which makes kaempferol but not quercetin, showed that quercetin derivatives are the inhibitors of basipetal root auxin transport, gravitropism, and elongation growth. Collectively, these experiments demonstrate that auxin and ethylene regulate flavonol biosynthesis through distinct signaling networks involving TIR1 and EIN2/ETR1, respectively, both of which converge on MYB12. This study also provides new evidence that quercetin is the flavonol that modulates basipetal auxin transport

  3. Hormonal changes in relation to biomass partitioning and shoot growth impairment in salinized tomato (Solanum lycopersicum L.) plants

    PubMed Central

    Albacete, Alfonso; Ghanem, Michel Edmond; Martínez-Andújar, Cristina; Acosta, Manuel; Sánchez-Bravo, José; Martínez, Vicente; Lutts, Stanley; Dodd, Ian C.; Pérez-Alfocea, Francisco

    2008-01-01

    Following exposure to salinity, the root/shoot ratio is increased (an important adaptive response) due to the rapid inhibition of shoot growth (which limits plant productivity) while root growth is maintained. Both processes may be regulated by changes in plant hormone concentrations. Tomato plants (Solanum lycopersicum L. cv Moneymaker) were cultivated hydroponically for 3 weeks under high salinity (100 mM NaCl) and five major plant hormones (abscisic acid, ABA; the cytokinins zeatin, Z, and zeatin-riboside, ZR; the auxin indole-3-acetic acid, IAA; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, ACC) were determined weekly in roots, xylem sap, and leaves. Salinity reduced shoot biomass by 50–60% and photosynthetic area by 20–25% both by decreasing leaf expansion and delaying leaf appearance, while root growth was less affected, thus increasing the root/shoot ratio. ABA and ACC concentrations strongly increased in roots, xylem sap, and leaves after 1 d (ABA) and 15 d (ACC) of salinization. By contrast, cytokinins and IAA were differentially affected in roots and shoots. Salinity dramatically decreased the Z+ZR content of the plant, and induced the conversion of ZR into Z, especially in the roots, which accounted for the relative increase of cytokinins in the roots compared to the leaf. IAA concentration was also strongly decreased in the leaves while it accumulated in the roots. Decreased cytokinin content and its transport from the root to the shoot were probably induced by the basipetal transport of auxin from the shoot to the root. The auxin/cytokinin ratio in the leaves and roots may explain both the salinity-induced decrease in shoot vigour (leaf growth and leaf number) and the shift in biomass allocation to the roots, in agreement with changes in the activity of the sink-related enzyme cell wall invertase. PMID:19036841

  4. Auxin Transport in Zea mays Coleoptiles II. Influence of Light on the Transport of Indoleacetic Acid-2-14C

    PubMed Central

    Naqvi, S. M.; Gordon, S. A.

    1967-01-01

    The effect of bilateral irradiation with white light (1000 Meter Candle Sec) on the basipetal transport of auxin has been investigated. Illumination of either the intact shoot or the excised coleoptile tip of the Zea seedling, decreased the amount of diffusible auxin obtained from the tip, and decreased Avena curvature response to unilaterally applied indoleacetic acid. Irradiation of the intact Zea seedling did not affect the absorption of 14C-labeled indoleacetic acid from an agar block subsequently placed on the decapitated coleoptile. However, light caused a significant decrease in the amount of labeled auxin basipetally transported, without affecting materially the velocity of that transport. These and other observations are interpreted as support for the hypothesis that the primary hormonal phenomenon in first-positive phototropism is a light-induced impairment in the basipetal transport of auxin. PMID:16656477

  5. Ethylene is Involved in Brassinosteroids Induced Alternative Respiratory Pathway in Cucumber (Cucumis sativus L.) Seedlings Response to Abiotic Stress

    PubMed Central

    Wei, Li-Jie; Deng, Xing-Guang; Zhu, Tong; Zheng, Ting; Li, Peng-Xu; Wu, Jun-Qiang; Zhang, Da-Wei; Lin, Hong-Hui

    2015-01-01

    Effects of brassinosteroids (BRs) on cucumber (Cucumis sativus L.) abiotic stresses resistance to salt, polyethylene glycol (PEG), cold and the potential mechanisms were investigated in this work. Previous reports have indicated that BRs can induce ethylene production and enhance alternative oxidase (AOX) pathway. The mechanisms whether ethylene is involved as a signal molecule which connected BR with AOX in regulating stress tolerance are still unknown. Here, we found that pretreatment with 1 μM brassinolide (BL, the most active BRs) relieved stress-caused oxidative damage in cucumber seedlings and clearly enhanced the capacity of AOX and the ethylene biosynthesis. Furthermore, transcription level of ethylene signaling biosynthesis genes including ripening-related ACC synthase1 (CSACS1), ripening-related ACC synthase2 (CSACS2), ripening-related ACC synthase3 (CSACS3), 1-aminocyclopropane-1-carboxylate oxidase1 (CSACO1), 1-aminocyclopropane-1-carboxylate oxidase2 (CSACO2), and CSAOX were increased after BL treatment. Importantly, the application of the salicylhydroxamic acid (SHAM, AOX inhibitor) and ethylene biosynthesis inhibitor aminooxyacetic acid (AOA) decreased plant resistance to environmental stress by blocking BRs-induced alternative respiration. Taken together, our results demonstrated that ethylene was involved in BRs-induced AOX activity which played important roles in abiotic stresses tolerance in cucumber seedlings. PMID:26617622

  6. Biochemical plant responses to ozone. 1. Differential induction of polyamine and ethylene biosynthesis in tobacco

    SciTech Connect

    Langebartels, C.; Kerner, K.; Leonardi, S.; Schraudner, M.; Trost, M.; Heller, W.; Sandermann, H. Jr. )

    1991-03-01

    Polyamine metabolism was examined in tobacco (Nicotiana tabacum L.) exposed to a single ozone treatment (5 or 7 hours) and then postcultivated in pollutant-free air. The levels of free and conjugated putrescine were rapidly increased in the ozone-tolerant cultivar Bel B and remained high for 3 days. This accumulation was preceded by a transient rise of L-arginine decarboxylase (ADC, EC 4.1.1.19) activity. The ozone-sensitive cultivar Bel W3 showed a rapid production of ethylene and high levels of 1-aminocyclopropane-1-carboxylic acid after 1 to 2 hours of exposure. Induction of putrescine levels and ADC activity was weak in this cultivar and was observed when necrotic lesions developed. Leaf injury occurred in both lines when the molar ratio of putrescine to 1-aminocyclopropane-1-carboxylic acid or ethylene fell short of a certain threshold value. Monocaffeoyl-putrescine, an effective scavenger for oxyradicals, was detected in the apoplastic fluid of the leaves of cv Bel B and increased upon exposure to ozone. This extracellular localization could allow scavenging of ozone-derived oxyradicals at the first site of their generation. Induction of either polyamine or ethylene pathways may represent a control mechanism for inhibition or promotion of lesion formation and thereby contribute to the disposition of plants for ozone tolerance.

  7. Ethylene-Mediated Programmed Cell Death during Maize Endosperm Development of Wild-Type and shrunken2 Genotypes.

    PubMed Central

    Young, T. E.; Gallie, D. R.; DeMason, D. A.

    1997-01-01

    We characterized the progression of programmed cell death during maize (Zea mays L.) endosperm development of starchy (Su; wild-type) and shrunken2 (sh2) genotypes and tested the involve ment of ethylene in mediating this process. Histological and viability staining demonstrated that endosperm cell death was initiated earlier and progressed more rapidly in sh2 endosperm compared with Su endosperm. Internucleosomal DNA fragmentation accompanied endosperm cell death and occurred more extensively in sh2 endosperm. 1-Aminocyclopropane-1-carboxylic acid levels peaked approximately 16 d after pollination (dap) in Su endosperm and gradually decreased during subsequent development, whereas two large 1-aminocyclopropane-1-carboxylic acid peaks were observed in sh2 endosperm, the first between 16 and 20 dap and the second at 36 dap. Ethylene levels were elevated in sh2 kernels compared with Su kernels, with an initial peak 20 dap approximately 3-fold higher than in Su kernels and a second peak 36 dap approximately 5-fold higher than that in Su kernels. Ethylene treatment of Su kernels resulted in earlier and more extensive endosperm cell death and DNA fragmentation. Aminoethoxyvinylglycine treatment of sh2 kernels reduced the extent of DNA fragmentation. We conclude that ethylene is involved in triggering programmed cell death in developing maize endosperm and is responsible for the aberrant phenotype of sh2 kernels. PMID:12223841

  8. Ethylene is Involved in Brassinosteroids Induced Alternative Respiratory Pathway in Cucumber (Cucumis sativus L.) Seedlings Response to Abiotic Stress.

    PubMed

    Wei, Li-Jie; Deng, Xing-Guang; Zhu, Tong; Zheng, Ting; Li, Peng-Xu; Wu, Jun-Qiang; Zhang, Da-Wei; Lin, Hong-Hui

    2015-01-01

    Effects of brassinosteroids (BRs) on cucumber (Cucumis sativus L.) abiotic stresses resistance to salt, polyethylene glycol (PEG), cold and the potential mechanisms were investigated in this work. Previous reports have indicated that BRs can induce ethylene production and enhance alternative oxidase (AOX) pathway. The mechanisms whether ethylene is involved as a signal molecule which connected BR with AOX in regulating stress tolerance are still unknown. Here, we found that pretreatment with 1 μM brassinolide (BL, the most active BRs) relieved stress-caused oxidative damage in cucumber seedlings and clearly enhanced the capacity of AOX and the ethylene biosynthesis. Furthermore, transcription level of ethylene signaling biosynthesis genes including ripening-related ACC synthase1 (C S ACS1), ripening-related ACC synthase2 (C S ACS2), ripening-related ACC synthase3 (C S ACS3), 1-aminocyclopropane-1-carboxylate oxidase1 (C S ACO1), 1-aminocyclopropane-1-carboxylate oxidase2 (C S ACO2), and C S AOX were increased after BL treatment. Importantly, the application of the salicylhydroxamic acid (SHAM, AOX inhibitor) and ethylene biosynthesis inhibitor aminooxyacetic acid (AOA) decreased plant resistance to environmental stress by blocking BRs-induced alternative respiration. Taken together, our results demonstrated that ethylene was involved in BRs-induced AOX activity which played important roles in abiotic stresses tolerance in cucumber seedlings.

  9. Ethylene Regulates the Arabidopsis Microtubule-Associated Protein WAVE-DAMPENED2-LIKE5 in Etiolated Hypocotyl Elongation1[OPEN

    PubMed Central

    Sun, Jingbo; Ma, Qianqian; Mao, Tonglin

    2015-01-01

    The phytohormone ethylene plays crucial roles in the negative regulation of plant etiolated hypocotyl elongation. The microtubule cytoskeleton also participates in hypocotyl cell growth. However, it remains unclear if ethylene signaling-mediated etiolated hypocotyl elongation involves the microtubule cytoskeleton. In this study, we functionally identified the previously uncharacterized microtubule-associated protein WAVE-DAMPENED2-LIKE5 (WDL5) as a microtubule-stabilizing protein that plays a positive role in ethylene-regulated etiolated hypocotyl cell elongation in Arabidopsis (Arabidopsis thaliana). ETHYLENE-INSENSITIVE3, a key transcription factor in the ethylene signaling pathway, directly targets and up-regulates WDL5. Etiolated hypocotyls from a WDL5 loss-of-function mutant (wdl5-1) were more insensitive to 1-aminocyclopropane-1-carboxylic acid treatment than the wild type. Decreasing WDL5 expression partially rescued the shorter etiolated hypocotyl phenotype in the ethylene overproduction mutant eto1-1. Reorganization of cortical microtubules in etiolated hypocotyl cells from the wdl5-1 mutant was less sensitive to 1-aminocyclopropane-1-carboxylic acid treatment. These findings indicate that WDL5 is an important participant in ethylene signaling inhibition of etiolated hypocotyl growth. This study reveals a mechanism involved in the ethylene regulation of microtubules through WDL5 to inhibit etiolated hypocotyl cell elongation. PMID:26134166

  10. Ethylene Regulates the Arabidopsis Microtubule-Associated Protein WAVE-DAMPENED2-LIKE5 in Etiolated Hypocotyl Elongation.

    PubMed

    Sun, Jingbo; Ma, Qianqian; Mao, Tonglin

    2015-09-01

    The phytohormone ethylene plays crucial roles in the negative regulation of plant etiolated hypocotyl elongation. The microtubule cytoskeleton also participates in hypocotyl cell growth. However, it remains unclear if ethylene signaling-mediated etiolated hypocotyl elongation involves the microtubule cytoskeleton. In this study, we functionally identified the previously uncharacterized microtubule-associated protein WAVE-DAMPENED2-LIKE5 (WDL5) as a microtubule-stabilizing protein that plays a positive role in ethylene-regulated etiolated hypocotyl cell elongation in Arabidopsis (Arabidopsis thaliana). ETHYLENE-INSENSITIVE3, a key transcription factor in the ethylene signaling pathway, directly targets and up-regulates WDL5. Etiolated hypocotyls from a WDL5 loss-of-function mutant (wdl5-1) were more insensitive to 1-aminocyclopropane-1-carboxylic acid treatment than the wild type. Decreasing WDL5 expression partially rescued the shorter etiolated hypocotyl phenotype in the ethylene overproduction mutant eto1-1. Reorganization of cortical microtubules in etiolated hypocotyl cells from the wdl5-1 mutant was less sensitive to 1-aminocyclopropane-1-carboxylic acid treatment. These findings indicate that WDL5 is an important participant in ethylene signaling inhibition of etiolated hypocotyl growth. This study reveals a mechanism involved in the ethylene regulation of microtubules through WDL5 to inhibit etiolated hypocotyl cell elongation.

  11. Biochemical Plant Responses to Ozone 1

    PubMed Central

    Langebartels, Christian; Kerner, Kristina; Leonardi, Silvio; Schraudner, Martina; Trost, Monika; Heller, Werner; Sandermann, Heinrich

    1991-01-01

    Polyamine metabolism was examined in tobacco (Nicotiana tabacum L.) exposed to a single ozone treatment (5 or 7 hours) and then postcultivated in pollutant-free air. The levels of free and conjugated putrescine were rapidly increased in the ozone-tolerant cultivar Bel B and remained high for 3 days. This accumulation was preceded by a transient rise of l-arginine decar-boxylase (ADC, EC 4.1.1.19) activity. The ozone-sensitive cultivar Bel W3 showed a rapid production of ethylene and high levels of 1-aminocyclopropane-1-carboxylic acid after 1 to 2 hours of exposure. Induction of putrescine levels and ADC activity was weak in this cultivar and was observed when necrotic lesions developed. Leaf injury occurred in both lines when the molar ratio of putrescine to 1-aminocyclopropane-1-carboxylic acid or ethylene fell short of a certain threshold value. Monocaffeoyl-putrescine, an effective scavenger for oxyradicals, was detected in the apo-plastic fluid of the leaves of cv Bel B and increased upon exposure to ozone. This extracellular localization could allow scavenging of ozone-derived oxyradicals at the first site of their generation. Induction of either polyamine or ethylene pathways may represent a control mechanism for inhibition or promotion of lesion formation and thereby contribute to the disposition of plants for ozone tolerance. PMID:16668067

  12. Mitochondrial ascorbic acid transport is mediated by a low-affinity form of the sodium-coupled ascorbic acid transporter-2.

    PubMed

    Muñoz-Montesino, Carola; Roa, Francisco J; Peña, Eduardo; González, Mauricio; Sotomayor, Kirsty; Inostroza, Eveling; Muñoz, Carolina A; González, Iván; Maldonado, Mafalda; Soliz, Carlos; Reyes, Alejandro M; Vera, Juan Carlos; Rivas, Coralia I

    2014-05-01

    Despite the fundamental importance of the redox metabolism of mitochondria under normal and pathological conditions, our knowledge regarding the transport of vitamin C across mitochondrial membranes remains far from complete. We report here that human HEK-293 cells express a mitochondrial low-affinity ascorbic acid transporter that molecularly corresponds to SVCT2, a member of the sodium-coupled ascorbic acid transporter family 2. The transporter SVCT1 is absent from HEK-293 cells. Confocal colocalization experiments with anti-SVCT2 and anti-organelle protein markers revealed that most of the SVCT2 immunoreactivity was associated with mitochondria, with minor colocalization at the endoplasmic reticulum and very low immunoreactivity at the plasma membrane. Immunoblotting of proteins extracted from highly purified mitochondrial fractions confirmed that SVCT2 protein was associated with mitochondria, and transport analysis revealed a sigmoidal ascorbic acid concentration curve with an apparent ascorbic acid transport Km of 0.6mM. Use of SVCT2 siRNA for silencing SVCT2 expression produced a major decrease in mitochondrial SVCT2 immunoreactivity, and immunoblotting revealed decreased SVCT2 protein expression by approximately 75%. Most importantly, the decreased protein expression was accompanied by a concomitant decrease in the mitochondrial ascorbic acid transport rate. Further studies using HEK-293 cells overexpressing SVCT2 at the plasma membrane revealed that the altered kinetic properties of mitochondrial SVCT2 are due to the ionic intracellular microenvironment (low in sodium and high in potassium), with potassium acting as a concentration-dependent inhibitor of SVCT2. We discarded the participation of two glucose transporters previously described as mitochondrial dehydroascorbic acid transporters; GLUT1 is absent from mitochondria and GLUT10 is not expressed in HEK-293 cells. Overall, our data indicate that intracellular SVCT2 is localized in mitochondria, is

  13. Potency of individual bile acids to regulate bile acid synthesis and transport genes in primary human hepatocyte cultures.

    PubMed

    Liu, Jie; Lu, Hong; Lu, Yuan-Fu; Lei, Xiaohong; Cui, Julia Yue; Ellis, Ewa; Strom, Stephen C; Klaassen, Curtis D

    2014-10-01

    Bile acids (BAs) are known to regulate their own homeostasis, but the potency of individual bile acids is not known. This study examined the effects of cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA) and ursodeoxycholic acid (UDCA) on expression of BA synthesis and transport genes in human primary hepatocyte cultures. Hepatocytes were treated with the individual BAs at 10, 30, and 100μM for 48 h, and RNA was extracted for real-time PCR analysis. For the classic pathway of BA synthesis, BAs except for UDCA markedly suppressed CYP7A1 (70-95%), the rate-limiting enzyme of bile acid synthesis, but only moderately (35%) down-regulated CYP8B1 at a high concentration of 100μM. BAs had minimal effects on mRNA of two enzymes of the alternative pathway of BA synthesis, namely CYP27A1 and CYP7B1. BAs increased the two major target genes of the farnesoid X receptor (FXR), namely the small heterodimer partner (SHP) by fourfold, and markedly induced fibroblast growth factor 19 (FGF19) over 100-fold. The BA uptake transporter Na(+)-taurocholate co-transporting polypeptide was unaffected, whereas the efflux transporter bile salt export pump was increased 15-fold and OSTα/β were increased 10-100-fold by BAs. The expression of the organic anion transporting polypeptide 1B3 (OATP1B3; sixfold), ATP-binding cassette (ABC) transporter G5 (ABCG5; sixfold), multidrug associated protein-2 (MRP2; twofold), and MRP3 (threefold) were also increased, albeit to lesser degrees. In general, CDCA was the most potent and effective BA in regulating these genes important for BA homeostasis, whereas DCA and CA were intermediate, LCA the least, and UDCA ineffective.

  14. Sialic acid catabolism and transport gene clusters are lineage specific in Vibrio vulnificus.

    PubMed

    Lubin, Jean-Bernard; Kingston, Joseph J; Chowdhury, Nityananda; Boyd, E Fidelma

    2012-05-01

    Sialic or nonulosonic acids are nine-carbon alpha ketosugars that are present in all vertebrate mucous membranes. Among bacteria, the ability to catabolize sialic acid as a carbon source is present mainly in pathogenic and commensal species of animals. Previously, it was shown that several Vibrio species carry homologues of the genes required for sialic acid transport and catabolism, which are genetically linked. In Vibrio cholerae on chromosome I, these genes are carried on the Vibrio pathogenicity island-2 region, which is confined to pathogenic isolates. We found that among the three sequenced Vibrio vulnificus clinical strains, these genes are present on chromosome II and are not associated with a pathogenicity island. To determine whether the sialic acid transport (SAT) and catabolism (SAC) region is universally present within V. vulnificus, we examined 67 natural isolates whose phylogenetic relationships are known. We found that the region was present predominantly among lineage I of V. vulnificus, which is comprised mainly of clinical isolates. We demonstrate that the isolates that contain this region can catabolize sialic acid as a sole carbon source. Two putative transporters are genetically linked to the region in V. vulnificus, the tripartite ATP-independent periplasmic (TRAP) transporter SiaPQM and a component of an ATP-binding cassette (ABC) transporter. We constructed an in-frame deletion mutation in siaM, a component of the TRAP transporter, and demonstrate that this transporter is essential for sialic acid uptake in this species. Expression analysis of the SAT and SAC genes indicates that sialic acid is an inducer of expression. Overall, our study demonstrates that the ability to catabolize and transport sialic acid is predominately lineage specific in V. vulnificus and that the TRAP transporter is essential for sialic acid uptake.

  15. The role of L-type amino acid transporter 1 in human tumors

    PubMed Central

    Zhao, Yu; Wang, Lin; Pan, Jihong

    2015-01-01

    Summary L-type amino acid transporter 1 (LAT1) is an L-type amino acid transporter and transports large neutral amino acids such as leucine, isoleucine, valine, phenylalanine, tyrosine, tryptophan, methionine, and histidine. LAT1 was found to be highly expressed especially in human cancer tissues, and up-regulated LAT1 can lead to dysfunction in human tumor cells. These findings suggest that LAT1 plays an important role in human tumors. This review provides an overview of the current understanding of LAT1 expression and its clinical significance and function in tumors. PMID:26668776

  16. Structural basis of the alternating-access mechanism in a bile acid transporter

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoming; Levin, Elena J.; Pan, Yaping; McCoy, Jason G.; Sharma, Ruchika; Kloss, Brian; Bruni, Renato; Quick, Matthias; Zhou, Ming

    2014-01-01

    Bile acids are synthesized from cholesterol in hepatocytes and secreted through the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for resecretion. In humans, there are two Na+-dependent bile acid transporters involved in enterohepatic recirculation, the Na+-taurocholate co-transporting polypeptide (NTCP; also known as SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT; also known as SLC10A2) expressed on enterocytes in the terminal ileum. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolaemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. However, a lack of three-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data. The crystal structure of an ASBT homologue from Neisseria meningitidis (ASBTNM) in detergent was reported recently, showing the protein in an inward-open conformation bound to two Na+ and a taurocholic acid. However, the structural changes that bring bile acid and Na+ across the membrane are difficult to infer from a single structure. To understand the structural changes associated with the coupled transport of Na+ and bile acids, here we solved two structures of an ASBT homologue from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives the conserved `crossover' region, where two discontinuous helices cross each other, alternating accessibility from either side of the cell membrane. This result has implications

  17. Oleic acid stimulates system A amino acid transport in primary human trophoblast cells mediated by toll-like receptor 4.

    PubMed

    Lager, Susanne; Gaccioli, Francesca; Ramirez, Vanessa I; Jones, Helen N; Jansson, Thomas; Powell, Theresa L

    2013-03-01

    Obese women have an increased risk to deliver large babies. However, the mechanisms underlying fetal overgrowth in these pregnancies are not well understood. Obese pregnant women typically have elevated circulating lipid levels. We tested the hypothesis that fatty acids stimulate placental amino acid transport, mediated via toll-like receptor 4 (TLR4) and mammalian target of rapamycin (mTOR) signaling pathways. Circulating NEFA levels and placental TLR4 expression were assessed in women with varying prepregnancy body mass index (BMI). The effects of oleic acid on system A and system L amino acid transport, and on the activation of the mTOR (4EBP1, S6K1, rpS6), TLR4 (IĸB, JNK, p38 MAPK), and STAT3 signaling pathways were determined in cultured primary human trophoblast cells. Maternal circulating NEFAs (n = 33), but not placental TLR4 mRNA expression (n = 16), correlated positively with BMI (P < 0.05). Oleic acid increased trophoblast JNK and STAT3 phosphorylation (P < 0.05), whereas mTOR activity was unaffected. Furthermore, oleic acid doubled trophoblast system A activity (P < 0.05), without affecting system L activity. siRNA-mediated silencing of TLR4 expression prevented the stimulatory effect of oleic acid on system A activity. Our data suggest that maternal fatty acids can increase placental nutrient transport via TLR4, thereby potentially affecting fetal growth.

  18. Bacteria in combination with fertilizers promote root and shoot growth of maize in saline-sodic soil.

    PubMed

    Zafar-Ul-Hye, Muhammad; Farooq, Hafiz Muhammad; Hussain, Mubshar

    2015-03-01

    Salinity is the leading abiotic stress hampering maize ( Zea mays L.) growth throughout the world, especially in Pakistan. During salinity stress, the endogenous ethylene level in plants increases, which retards proper root growth and consequent shoot growth of the plants. However, certain bacteria contain the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which converts 1-aminocyclopropane-1-carboxylic acid (an immediate precursor of ethylene biosynthesis in higher plants) into ammonia and α-ketobutyrate instead of ethylene. In the present study, two Pseudomonas bacterial strains containing ACC-deaminase were tested separately and in combinations with mineral fertilizers to determine their potential to minimize/undo the effects of salinity on maize plants grown under saline-sodic field conditions. The data recorded at 30, 50 and 70 days after sowing revealed that both the Pseudomonas bacterial strains improved root and shoot length, root and shoot fresh weight, and root and shoot dry weight up to 34, 43, 35, 71, 55 and 68%, respectively, when applied without chemical fertilizers: these parameter were enhanced up to 108, 95, 100, 131, 100 and 198%, respectively, when the strains were applied along with chemical fertilizers. It can be concluded that ACC-deaminase Pseudomonas bacterial strains applied alone and in conjunction with mineral fertilizers improved the root and shoot growth of maize seedlings grown in saline-sodic soil.

  19. Exogenously induced expression of ethylene biosynthesis, ethylene perception, phospholipase D, and Rboh-oxidase genes in broccoli seedlings.

    PubMed

    Jakubowicz, Małgorzata; Gałgańska, Hanna; Nowak, Witold; Sadowski, Jan

    2010-07-01

    In higher plants, copper ions, hydrogen peroxide, and cycloheximide have been recognized as very effective inducers of the transcriptional activity of genes encoding the enzymes of the ethylene biosynthesis pathway. In this report, the transcriptional patterns of genes encoding the 1-aminocyclopropane-1-carboxylate synthases (ACSs), 1-aminocyclopropane-1-carboxylate oxidases (ACOs), ETR1, ETR2, and ERS1 ethylene receptors, phospholipase D (PLD)-alpha1, -alpha2, -gamma1, and -delta, and respiratory burst oxidase homologue (Rboh)-NADPH oxidase-D and -F in response to these inducers in Brassica oleracea etiolated seedlings are shown. ACS1, ACO1, ETR2, PLD-gamma1, and RbohD represent genes whose expression was considerably affected by all of the inducers used. The investigations were performed on the seedlings with (i) ethylene insensitivity and (ii) a reduced level of the PLD-derived phosphatidic acid (PA). The general conclusion is that the expression of ACS1, -3, -4, -5, -7, and -11, ACO1, ETR1, ERS1, and ETR2, PLD-gamma 1, and RbohD and F genes is undoubtedly under the reciprocal cross-talk of the ethylene and PA(PLD) signalling routes; both signals affect it in concerted or opposite ways depending on the gene or the type of stimuli. The results of these studies on broccoli seedlings are in agreement with the hypothesis that PA may directly affect the ethylene signal transduction pathway via an inhibitory effect on CTR1 (constitutive triple response 1) activity.

  20. Plasmodium falciparum malaria elicits inflammatory responses that dysregulate placental amino acid transport.

    PubMed

    Boeuf, Philippe; Aitken, Elizabeth H; Chandrasiri, Upeksha; Chua, Caroline Lin Lin; McInerney, Bernie; McQuade, Leon; Duffy, Michael; Molyneux, Malcolm; Brown, Graham; Glazier, Jocelyn; Rogerson, Stephen J

    2013-02-01

    Placental malaria (PM) can lead to poor neonatal outcomes, including low birthweight due to fetal growth restriction (FGR), especially when associated with local inflammation (intervillositis or IV). The pathogenesis of PM-associated FGR is largely unknown, but in idiopathic FGR, impaired transplacental amino acid transport, especially through the system A group of amino acid transporters, has been implicated. We hypothesized that PM-associated FGR could result from impairment of transplacental amino acid transport triggered by IV. In a cohort of Malawian women and their infants, the expression and activity of system A (measured by Na⁺-dependent ¹⁴C-MeAIB uptake) were reduced in PM, especially when associated with IV, compared to uninfected placentas. In an in vitro model of PM with IV, placental cells exposed to monocyte/infected erythrocytes conditioned medium showed decreased system A activity. Amino acid concentrations analyzed by reversed phase ultra performance liquid chromatography in paired maternal and cord plasmas revealed specific alterations of amino acid transport by PM, especially with IV. Overall, our data suggest that the fetoplacental unit responds to PM by altering its placental amino acid transport to maintain adequate fetal growth. However, IV more profoundly compromises placental amino acid transport function, leading to FGR. Our study offers the first pathogenetic explanation for FGR in PM.

  1. Transporters for ammonium, amino acids and peptides are expressed in pitchers of the carnivorous plant Nepenthes.

    PubMed

    Schulze, W; Frommer, W B; Ward, J M

    1999-03-01

    Insect capture and digestion contribute substantially to the nitrogen budget of carnivorous plants. In Nepenthes, insect-derived nitrogenous compounds are imported from the pitcher fluid and transported throughout the plant via the vascular tissue to support growth. Import and distribution of nutrients may require transmembrane nitrogen transporters. Representatives of three classes of genes encoding transporters for the nitrogenous compounds ammonium, amino acids and peptides were identified in Nepenthes pitchers. The expression at the cellular level of an ammonium transporter gene, three amino acid transporter genes, and one peptide transporter gene were investigated in the insect trapping organs of Nepenthes. Expression of the ammonium transporter gene NaAMT1 was detected in the head cells of digestive glands in the lower part of the pitcher where NaAMT1 may function in ammonium uptake from the pitcher fluid. One amino acid transporter gene, NaAAP1, was expressed in bundle sheath cells surrounding the vascular tissue. To understand the locations where transmembrane transport could be required within the pitcher, symplasmic and apoplasmic continuity was probed using fluorescent dyes. Symplasmic connections were not found between cortical cells and vascular bundles. Therefore, the amino acid transporter encoded by NaAAP1 may be involved in transport of amino acids into the vascular tissue. In contrast, expression of the peptide transporter gene NaNTR1 was detected in phloem cells of the vascular tissue within pitchers. NaNTR1 may function in the export of nitrogen from the pitcher by loading peptides into the phloem. PMID:10230062

  2. Regulation of amino acid transporters in pluripotent cell populations in the embryo and in culture; novel roles for sodium-coupled neutral amino acid transporters.

    PubMed

    Tan, Boon Siang Nicholas; Rathjen, Peter D; Harvey, Alexandra J; Gardner, David K; Rathjen, Joy

    2016-08-01

    The developmental outcomes of preimplantation mammalian embryos are regulated directly by the surrounding microenvironment, and inappropriate concentrations of amino acids, or the loss of amino acid-sensing mechanisms, can be detrimental and impact further development. A specific role for l-proline in the differentiation of embryonic stem (ES) cells, a cell population derived from the blastocyst, has been shown in culture. l-proline acts as a signalling molecule, exerting its effects through cell uptake and subsequent metabolism. Uptake in ES cells occurs predominantly through the sodium-coupled neutral amino acid transporter 2, Slc38a2 (SNAT2). Dynamic expression of amino acid transporters has been shown in the early mammalian embryo, reflecting functional roles for amino acids in embryogenesis. The expression of SNAT2 and family member Slc38a1 (SNAT1) was determined in mouse embryos from the 2-cell stage through to the early post-implantation pre-gastrulation embryo. Key changes in expression were validated in cell culture models of development. Both transporters showed temporal dynamic expression patterns and changes in intracellular localisation as differentiation progressed. Changes in transporter expression likely reflect different amino acid requirements during development. Findings include the differential expression of SNAT1 in the inner and outer cells of the compacted morula and nuclear localisation of SNAT2 in the trophectoderm and placental lineages. Furthermore, SNAT2 expression was up-regulated in the epiblast prior to primitive ectoderm formation, an expression pattern consistent with a role for the transporter in later developmental decisions within the pluripotent lineage. We propose that the differential expression of SNAT2 in the epiblast provides evidence for an l-proline-mediated mechanism contributing to the regulation of embryonic development. PMID:27373508

  3. Characteristics of the transport of ascorbic acid into leucocytes

    SciTech Connect

    Raghoebar, M.; Huisman, J.A.M.; van den Berg, W.B.; van Ginneken, C.A.M.

    1987-02-02

    The degree and the mode of association of (/sup 14/C)-ascorbic acid with leucocytes are examined. The degree of association of ascorbic acid with polymorphonuclear leucocytes (1-3 %) is dependent on cell type, extracellular concentration of ascorbic acid, incubation temperature, intactness of the cells and the extracellular pH. All experiments are performed according to strict protocols as these compounds are labile in aqueous solutions. Further it is noticed that in all experiments an outward gradient of leucocyte endogenic ascorbic acid exists. The results suggest that the association process comprises at least one saturable pathway. The activation of polymorphonuclear leucocytes by phorbol myristate acetate increases the accumulation of ascorbic acid threefold. 30 references, 7 figures, 3 tables.

  4. Aphid amino acid transporter regulates glutamine supply to intracellular bacterial symbionts.

    PubMed

    Price, Daniel R G; Feng, Honglin; Baker, James D; Bavan, Selvan; Luetje, Charles W; Wilson, Alex C C

    2014-01-01

    Endosymbiotic associations have played a major role in evolution. However, the molecular basis for the biochemical interdependence of these associations remains poorly understood. The aphid-Buchnera endosymbiosis provides a powerful system to elucidate how these symbioses are regulated. In aphids, the supply of essential amino acids depends on an ancient nutritional symbiotic association with the gamma-proteobacterium Buchnera aphidicola. Buchnera cells are densely packed in specialized aphid bacteriocyte cells. Here we confirm that five putative amino acid transporters are highly expressed and/or highly enriched in Acyrthosiphon pisum bacteriocyte tissues. When expressed in Xenopus laevis oocytes, two bacteriocyte amino acid transporters displayed significant levels of glutamine uptake, with transporter ACYPI001018, LOC100159667 (named here as Acyrthosiphon pisum glutamine transporter 1, ApGLNT1) functioning as the most active glutamine transporter. Transporter ApGLNT1 has narrow substrate selectivity, with high glutamine and low arginine transport capacity. Notably, ApGLNT1 has high binding affinity for arginine, and arginine acts as a competitive inhibitor for glutamine transport. Using immunocytochemistry, we show that ApGLNT1 is localized predominantly to the bacteriocyte plasma membrane, a location consistent with the transport of glutamine from A. pisum hemolymph to the bacteriocyte cytoplasm. On the basis of functional transport data and localization, we propose a substrate feedback inhibition model in which the accumulation of the essential amino acid arginine in A. pisum hemolymph reduces the transport of the precursor glutamine into bacteriocytes, thereby regulating amino acid biosynthesis in the bacteriocyte. Structural similarities in the arrangement of hosts and symbionts across endosymbiotic systems suggest that substrate feedback inhibition may be mechanistically important in other endosymbioses.

  5. Modulating effect of ascorbic Acid on transport-induced immunosuppression in goats.

    PubMed

    Minka, Ndazo Salka; Ayo, Joseph Olusegun

    2011-01-01

    The effect of 12 h road transportation on some basic blood cells and the modulating role of ascorbic acid were investigated in 40 adult Red Sokoto goats during the hot dry season. The animals were divided into two groups, GI (experimental; n = 20) and GII (control; n = 20). Group 1 was administered with ascorbic acid (AA) per os at a dosage rate of 100 mg/kg body weight, while GII was given 10 mL of sterile water per goat. Forty minutes after the administration and loading, the goats were transported for 12 h. The result obtained in GII goats showed that loading, transportation, high ambient temperature (AT), and relative humidity (RH) encountered during transportation induced lymphopenia, neutrophilia, and eosinopenia, which can cause immunosuppression. In GI goats, the administration of AA prior to loading and transportation ameliorated the adverse effects of loading and transportation stress on neutrophil/lymphocyte ratio and eosinopenia of the goats.

  6. Canine amino acid transport system Xc(-): cDNA sequence, distribution and cystine transport activity in lens epithelial cells.

    PubMed

    Maruo, Takuya; Kanemaki, Nobuyuki; Onda, Ken; Sato, Reiichiro; Ichihara, Nobuteru; Ochiai, Hideharu

    2014-04-01

    The cystine transport activity of a lens epithelial cell line originated from a canine mature cataract was investigated. The distinct cystine transport activity was observed, which was inhibited to 28% by extracellular 1 mM glutamate. The cDNA sequences of canine cysteine/glutamate exchanger (xCT) and 4F2hc were determined. The predicted amino acid sequences were 527 and 533 amino acid polypeptides, respectively. The amino acid sequences of canine xCT and 4F2hc showed high similarities (>80%) to those of humans. The expression of xCT in lens epithelial cell line was confirmed by western blot analysis. RT-PCR analysis revealed high level expression only in the brain, and it was below the detectable level in other tissues.

  7. The role of the neutral amino acid transporter SNAT2 in cell volume regulation.

    PubMed

    Franchi-Gazzola, R; Dall'Asta, V; Sala, R; Visigalli, R; Bevilacqua, E; Gaccioli, F; Gazzola, G C; Bussolati, O

    2006-01-01

    Sodium-dependent neutral amino acid transporter-2 (SNAT2), the ubiquitous member of SLC38 family, accounts for the activity of transport system A for neutral amino acids in most mammalian tissues. As the transport process performed by SNAT2 is highly energized, system A substrates, such as glutamine, glycine, proline and alanine, reach high transmembrane gradients and constitute major components of the intracellular amino acid pool. Moreover, through a complex array of exchange fluxes, involving other amino acid transporters, and of metabolic reactions, such as the synthesis of glutamate from glutamine, SNAT2 activity influences the cell content of most amino acids, thus determining the overall size and the composition of the intracellular amino acid pool. As amino acids represent a large fraction of cell organic osmolytes, changes of SNAT2 activity are followed by modifications in both cell amino acids and cell volume. This mechanism is utilized by many cell types to perform an effective regulatory volume increase (RVI) upon hypertonic exposure. Under these conditions, the expression of SNAT2 gene is induced and newly synthesized SNAT2 proteins are preferentially targeted to the cell membrane, leading to a significant increase of system A transport Vmax. In cultured human fibroblasts incubated under hypertonic conditions, the specific silencing of SNAT2 expression, obtained with anti-SNAT2 siRNAs, prevents the increase in system A transport activity, hinders the expansion of intracellular amino acid pool, and significantly delays cell volume recovery. These results demonstrate the pivotal role played by SNAT2 induction in the short-term hypertonic RVI and suggest that neutral amino acids behave as compatible osmolytes in hypertonically stressed cells.

  8. Role of organic acids in promoting colloidal transport of mercury from mine tailings

    USGS Publications Warehouse

    Slowey, A.J.; Johnson, S.B.; Rytuba, J.J.; Brown, Gordon E.

    2005-01-01

    A number of factors affect the transport of dissolved and paniculate mercury (Hg) from inoperative Hg mines, including the presence of organic acids in the rooting zone of vegetated mine waste. We examined the role of the two most common organic acids in soils (oxalic and citric acid) on Hg transport from such waste by pumping a mixed organic acid solution (pH 5.7) at 1 mL/min through Hg mine tailings columns. For the two total organic acid concentrations investigated (20 ??M and 1 mM), particle-associated Hg was mobilized, with the onset of paniculate Hg transport occurring later for the lower organic acid concentration. Chemical analyses of column effluent indicate that 98 wt % of Hg mobilized from the column was paniculate. Hg speciation was determined using extended X-ray absorption fine structure spectroscopy and transmission electron microscopy, showing that HgS minerals are dominant in the mobilized particles. Hg adsorbed to colloids is another likely mode of transport due to the abundance of Fe-(oxyhydr)oxides, Fe-sulfides, alunite, and jarosite in the tailings to which Hg(II) adsorbs. Organic acids produced by plants are likely to enhance the transport of colloid-associated Hg from vegetated Hg mine tailings by dissolving cements to enable colloid release. ?? 2005 American Chemical Society.

  9. Role of organic acids in promoting colloidal transport of mercury from mine tailings.

    PubMed

    Slowey, Aaron J; Johnson, Stephen B; Rytuba, James J; Brown, Gordon E

    2005-10-15

    A number of factors affect the transport of dissolved and particulate mercury (Hg) from inoperative Hg mines, including the presence of organic acids in the rooting zone of vegetated mine waste. We examined the role of the two most common organic acids in soils (oxalic and citric acid) on Hg transport from such waste by pumping a mixed organic acid solution (pH 5.7) at 1 mL/min through Hg mine tailings columns. For the two total organic acid concentrations investigated (20 microM and 1 mM), particle-associated Hg was mobilized, with the onset of particulate Hg transport occurring later for the lower organic acid concentration. Chemical analyses of column effluent indicate that 98 wt % of Hg mobilized from the column was particulate. Hg speciation was determined using extended X-ray absorption fine structure spectroscopy and transmission electron microscopy, showing that HgS minerals are dominant in the mobilized particles. Hg adsorbed to colloids is another likely mode of transport due to the abundance of Fe-(oxyhydr)oxides, Fe-sulfides, alunite, and jarosite in the tailings to which Hg(II) adsorbs. Organic acids produced by plants are likely to enhance the transport of colloid-associated Hg from vegetated Hg mine tailings by dissolving cements to enable colloid release.

  10. Utilization of Lactic Acid by Fusarium oxysporum var. lini: Regulation of Transport and Metabolism

    PubMed Central

    Castro, Ieso M.; Loureiro-Dias, Maria C.

    1994-01-01

    Lactic acid was transported in Fusarium oxysporum var. lini ATCC 10960 by a saturable transport system that had a half-saturation constant of 56.6 ± 7.5 μM and a maximum velocity of 0.61 ± 0.10 mmol h-1 g-1 (dry weight) at 26°C and pH 5.0. This transport system was inducible and was not expressed in the presence of a repressing substrate. Evidence is presented that the anionic form lactate- was taken up by the cells. Propionic, acetic, pyruvic, and bromoacetic acids but not succinic acid competitively inhibited the transport of lactic acid. Bromoacetic acid, which was not metabolized, was taken up to a steady-state level when intracellular and extracellular concentrations were identical, indicating that the transport system was not accumulative. The enzymatic activity that was physiologically more relevant in the metabolism of lactic acid was lactate: ferricytochrome c oxidase. This enzyme did not exhibit stereospecifity and was induced by lactic acid. PMID:16349143

  11. Characterization of methylaminoisobutyric acid transport by system A in rat mammary gland.

    PubMed

    Tovar, A R; Avila, E; DeSantiago, S; Torres, N

    2000-07-01

    During lactation, the mammary gland has a large demand for amino acids for the synthesis of milk proteins and fatty acids. Arteriovenous differences in amino acids across the mammary gland show an elevated uptake of small neutral amino acids that are mainly transported via system A. The purpose of this study was to characterize the transport of methylaminoisobutyric acid (MeAIB), an amino acid analog used to model transport by system A in lactating rat mammary gland explants. MeAIB accumulation in mammary gland cells increased steadily, and after 3 hours of incubation, the intracellular concentration of the analog was 8-fold higher than the concentration in the medium. MeAIB transport into mammary gland explants showed a Km of 3.3 +/- 0.4 mmol/L and a maximal velocity (Vmax) of 555 +/- 23 pmol/microL intracellular fluid (ICF) x min, indicating a system with high capacity but low affinity for its substrate. MeAIB transport into mammary tissue depended highly on Na+, and the uptake was inhibited by addition of natural and analog small neutral amino acids. Cationic, anionic, and large neutral amino acids did not reduce MeAIB transport into mammary gland explants. Preincubation of mammary gland explants in an amino acid-free medium stimulated MeAIB transport, suggesting an adaptive regulation. The addition of an equimolar mixture of alanine, glycine, and serine to the preincubation medium inhibited stimulation of MeAIB transport. Furthermore, stimulation of MeAIB uptake by amino acid starvation was also prevented by the addition of actinomycin D, cycloheximide, tunicamycin, and colchicine. Dibutyryl cyclic adenosine monophosphate (cAMP) increased MeAIB uptake, whereas phorbol 12-myristate 13-acetate (PMA) did not stimulate MeAIB transport. During the first postweaning days, kinetic analyses showed a decrease of 27% in the Vmax. Injection of rat lactating mammary gland mRNA into Xenopus laevis oocytes induced expression of the MeAIB transport system; however, the

  12. In-stream sorption of fulvic acid in an acidic stream: A stream-scale transport experiment

    USGS Publications Warehouse

    McKnight, Diane M.; Hornberger, G.M.; Bencala, K.E.; Boyer, E.W.

    2002-01-01

    The variation of concentration and composition of dissolved organic carbon (DOC) in stream waters cannot be explained solely on the basis of soil processes in contributing subcatchments. To investigate in-stream processes that control DOC, we injected DOC-enriched water into a reach of the Snake River (Summit County, Colorado) that has abundant iron oxyhydroxides coating the streambed. The injected water was obtained from the Suwannee River (Georgia), which is highly enriched in fulvic acid. The fulvic acid from this water is the standard reference for aquatic fulvic acid for the International Humic Substances Society and has been well characterized. During the experimental injection, significant removal of sorbable fulvic acid occurred within the first 141 m of stream reach. We coinjected a conservative tracer (lithium chloride) and analyzed the results with the one-dimensional transport with inflow and storage (OTIS) stream solute transport model to quantify the physical transport mechanisms. The downstream transport of fulvic acid as indicated by absorbance was then simulated using OTIS with a first-order kinetic sorption rate constant applied to the sorbable fulvic acid. The "sorbable" fraction of injected fulvic acid was irreversibly sorbed by streambed sediments at rates (kinetic rate constants) of the order of 10-4-10-3 S-1. In the injected Suwannee River water, sorbable and nonsorbable fulvic acid had distinct chemical characteristics identified in 13C-NMR spectra. The 13C-NMR spectra indicate that during the experiment, the sorbable "signal" of greater aromaticity and carboxyl content decreased downstream; that is, these components were preferentially removed. This study illustrates that interactions between the water and the reactive surfaces will modify significantly the concentration and composition of DOC observed in streams with abundant chemically reactive surfaces on the streambed and in the hyporheic zone.

  13. Maternal bile acid transporter deficiency promotes neonatal demise

    PubMed Central

    Zhang, Yuanyuan; Li, Fei; Wang, Yao; Pitre, Aaron; Fang, Zhong-ze; Frank, Matthew W.; Calabrese, Christopher; Krausz, Kristopher W.; Neale, Geoffrey; Frase, Sharon; Vogel, Peter; Rock, Charles O.; Gonzalez, Frank J.; Schuetz, John D.

    2015-01-01

    Intrahepatic cholestasis of pregnancy (ICP) is associated with adverse neonatal survival and is estimated to impact between 0.4 and 5% of pregnancies worldwide. Here we show that maternal cholestasis (due to Abcb11 deficiency) produces neonatal death among all offspring within 24 h of birth due to atelectasis-producing pulmonary hypoxia, which recapitulates the neonatal respiratory distress of human ICP. Neonates of Abcb11-deficient mothers have elevated pulmonary bile acids and altered pulmonary surfactant structure. Maternal absence of Nr1i2 superimposed on Abcb11 deficiency strongly reduces maternal serum bile acid concentrations and increases neonatal survival. We identify pulmonary bile acids as a key factor in the disruption of the structure of pulmonary surfactant in neonates of ICP. These findings have important implications for neonatal respiratory failure, especially when maternal bile acids are elevated during pregnancy, and highlight potential pathways and targets amenable to therapeutic intervention to ameliorate this condition. PMID:26416771

  14. Maternal bile acid transporter deficiency promotes neonatal demise.

    PubMed

    Zhang, Yuanyuan; Li, Fei; Wang, Yao; Pitre, Aaron; Fang, Zhong-Ze; Frank, Matthew W; Calabrese, Christopher; Krausz, Kristopher W; Neale, Geoffrey; Frase, Sharon; Vogel, Peter; Rock, Charles O; Gonzalez, Frank J; Schuetz, John D

    2015-09-29

    Intrahepatic cholestasis of pregnancy (ICP) is associated with adverse neonatal survival and is estimated to impact between 0.4 and 5% of pregnancies worldwide. Here we show that maternal cholestasis (due to Abcb11 deficiency) produces neonatal death among all offspring within 24 h of birth due to atelectasis-producing pulmonary hypoxia, which recapitulates the neonatal respiratory distress of human ICP. Neonates of Abcb11-deficient mothers have elevated pulmonary bile acids and altered pulmonary surfactant structure. Maternal absence of Nr1i2 superimposed on Abcb11 deficiency strongly reduces maternal serum bile acid concentrations and increases neonatal survival. We identify pulmonary bile acids as a key factor in the disruption of the structure of pulmonary surfactant in neonates of ICP. These findings have important implications for neonatal respiratory failure, especially when maternal bile acids are elevated during pregnancy, and highlight potential pathways and targets amenable to therapeutic intervention to ameliorate this condition.

  15. The bZIP Protein VIP1 Is Involved in Touch Responses in Arabidopsis Roots1[OPEN

    PubMed Central

    Liu, Shenkui; Takano, Tetsuo

    2016-01-01

    VIP1 is a bZIP transcription factor in Arabidopsis (Arabidopsis thaliana). VIP1 transiently accumulates in the nucleus when cells are exposed to hypoosmotic conditions, but its physiological relevance is unclear. This is possibly because Arabidopsis has approximately 10 close homologs of VIP1 and they function redundantly. To examine their physiological roles, transgenic plants overexpressing a repression domain-fused form of VIP1 (VIP1-SRDXox plants), in which the gene activation mediated by VIP1 is expected to be repressed, were generated. Because hypoosmotic stress can mimic mechanical stimuli (e.g. touch), the touch-induced root-waving phenotypes and gene expression patterns in those transgenic plants were examined. VIP1-SRDXox plants exhibited more severe root waving and lower expression of putative VIP1 target genes. The expression of the VIP1-green fluorescent protein (GFP) fusion protein partially suppressed the VIP1-SRDX-induced increase in root waving when expressed in the VIP1-SRDXox plants. These results suggest that VIP1 can suppress the touch-induced root waving. The VIP1-SRDX-induced increase in root waving was also suppressed when the synthetic auxin 2,4-dichlorophenoxy acetic acid or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, which is known to activate auxin biosynthesis, was present in the growth medium. Root cap cells with the auxin marker DR5rev::GFP were more abundant in the VIP1-SRDXox background than in the wild-type background. Auxin is transported via the root cap, and the conditions of outermost root cap layers were abnormal in VIP1-SRDXox plants. These results raise the possibility that VIP1 influences structures of the root cap and thereby regulates the local auxin responses in roots. PMID:27208231

  16. The SLC36 family of proton-coupled amino acid transporters and their potential role in drug transport

    PubMed Central

    Thwaites, David T; Anderson, Catriona MH

    2011-01-01

    Members of the solute carrier (SLC) 36 family are involved in transmembrane movement of amino acids and derivatives. SLC36 consists of four members. SLC36A1 and SLC36A2 both function as H+-coupled amino acid symporters. SLC36A1 is expressed at the luminal surface of the small intestine but is also commonly found in lysosomes in many cell types (including neurones), suggesting that it is a multipurpose carrier with distinct roles in different cells including absorption in the small intestine and as an efflux pathway following intralysosomal protein breakdown. SLC36A1 has a relatively low affinity (Km 1–10 mM) for its substrates, which include zwitterionic amino and imino acids, heterocyclic amino acids and amino acid-based drugs and derivatives used experimentally and/or clinically to treat epilepsy, schizophrenia, bacterial infections, hyperglycaemia and cancer. SLC36A2 is expressed at the apical surface of the human renal proximal tubule where it functions in the reabsorption of glycine, proline and hydroxyproline. SLC36A2 also transports amino acid derivatives but has a narrower substrate selectivity and higher affinity (Km 0.1–0.7 mM) than SLC36A1. Mutations in SLC36A2 lead to hyperglycinuria and iminoglycinuria. SLC36A3 is expressed only in testes and is an orphan transporter with no known function. SLC36A4 is widely distributed at the mRNA level and is a high-affinity (Km 2–3 µM) transporter for proline and tryptophan. We have much to learn about this family of transporters, but from current knowledge, it seems likely that their function will influence the pharmacokinetic profiles of amino acid-based drugs by mediating transport in both the small intestine and kidney. LINKED ARTICLES This article is part of a themed section on Transporters. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2011.164.issue-7 PMID:21501141

  17. Transportation impact analysis for the shipment of low specific activity nitric acid. Revisison 1

    SciTech Connect

    Green, J.R.

    1995-05-16

    This is in support of the Plutonium-Uranium Extraction (PUREX) Facility Low Specific Activity (LSA) Nitric Acid Shipment Environmental Assessment. It analyzes potential toxicological and radiological risks associated with transportation of PUREX Facility LSA Nitric Acid from the Hanford Site to Portsmouth VA, Baltimore MD, and Port Elizabeth NJ.

  18. Transport of Corilagin, Gallic Acid, and Ellagic Acid from Fructus Phyllanthi Tannin Fraction in Caco-2 Cell Monolayers

    PubMed Central

    Zhao, Hai-juan; Liang, Wen-Yi; Chen, Wen-Jing; Han, Shu-Xian; Qi, Qi; Cui, Ya-Ping; Li, Shi; Yang, Guang-Hui; Shao, Yan-Yan; Zhu, Dan

    2016-01-01

    Objective. To investigate the absorption property of the representative hydrolyzable tannin, namely corilagin, and its hydrolysates gallic acid (GA) and ellagic acid (EA) from the Fructus Phyllanthi tannin fraction (PTF) in vitro. Methods. Caco-2 cells monolayer model was established. Influences of PTF on Caco-2 cells viability were detected with MTT assay. The transport across monolayers was examined for different time points, concentrations, and secretory directions. The inhibitors of P-glycoprotein (P-gp), multidrug resistance proteins (MRPs), organic anion transporting polypeptide (OATP) and sodium/glucose cotransporter 1 (SGLT1), and tight junction modulators were used to study the transport mechanism. LC-MS method was employed to quantify the absorption concentration. Results. The apparent permeability coefficient (Papp) values of the three compounds were below 1.0 × 10−6 cm/s. The absorption of corilagin and GA were much lower than their efflux, and the uptake of both compounds was increased in the presence of inhibitors of P-gp and MRPs. The absorption of EA was decreased in the company of OATP and SGLT1 inhibitors. Moreover, the transport of corilagin, GA, and EA was enhanced by tight junction modulators. Conclusion. These observations indicated that the three compounds in PTF were transported via passive diffusion combined with protein mediated transport. P-gp and MRPs might get involved in the transport of corilagin and GA. The absorption of EA could be attributed to OATP and SGLT1 protein. PMID:27738446

  19. Expression pattern of peptide and amino acid genes in digestive tract of transporter juvenile turbot ( Scophthalmus maximus L.)

    NASA Astrophysics Data System (ADS)

    Xu, Dandan; He, Gen; Mai, Kangsen; Zhou, Huihui; Xu, Wei; Song, Fei

    2016-04-01

    Turbot ( Scophthalmus maximus L.), a carnivorous fish species with high dietary protein requirement, was chosen to examine the expression pattern of peptide and amino acid transporter genes along its digestive tract which was divided into six segments including stomach, pyloric caeca, rectum, and three equal parts of the remainder of the intestine. The results showed that the expression of two peptide and eleven amino acid transporters genes exhibited distinct patterns. Peptide transporter 1 (PepT1) was rich in proximal intestine while peptide transporter 2 (PepT2) was abundant in distal intestine. A number of neutral and cationic amino acid transporters expressed richly in whole intestine including B0-type amino acid transporter 1 (B0AT1), L-type amino acid transporter 2 (LAT2), T-type amino acid transporter 1 (TAT1), proton-coupled amino acid transporter 1 (PAT1), y+L-type amino acid transporter 1 (y+LAT1), and cationic amino acid transporter 2 (CAT2) while ASC amino acid transporter 2 (ASCT2), sodium-coupled neutral amino acid transporter 2 (SNAT2), and y+L-type amino acid transporter 2 (y+LAT2) abundantly expressed in stomach. In addition, system b0,+ transporters (rBAT and b0,+AT) existed richly in distal intestine. These findings comprehensively characterized the distribution of solute carrier family proteins, which revealed the relative importance of peptide and amino acid absorption through luminal membrane. Our findings are helpful to understand the mechanism of the utilization of dietary protein in fish with a short digestive tract.

  20. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells

    PubMed Central

    Komaba, Shigeru; Coluccio, Lynne M.

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  1. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells.

    PubMed

    Komaba, Shigeru; Coluccio, Lynne M

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  2. Role for Ion Transport in Porcine Vocal Fold Epithelial Defense to Acid Challenge

    PubMed Central

    Erickson-Levendoski, Elizabeth; Sivasankar, M. Preeti

    2012-01-01

    Objective The vocal fold epithelium is routinely exposed to gastric contents, including acid and pepsin, during laryngopharyngeal reflux events. The epithelium may possess intrinsic defenses to reflux. The first objective of the current study was to examine whether vocal fold epithelial ion transport is one potential mechanism of defense to gastric contents. The second objective was to determine whether ion transport in response to gastric contents is associated with the secretion of bicarbonate. Study Design Prospective design in excised porcine larynges. Setting Laboratory. Subjects and Methods Porcine vocal folds (N = 56) were exposed on the luminal surface to acid, pepsin, or sham challenges. Ion transport at baseline and following challenge exposure was measured using electrophysiological techniques. To examine specific ion transport mechanisms, vocal folds were pretreated with either a sodium channel blocker or bicarbonate channel blocker. Results Within 60 seconds of acid but not pepsin exposure, there was a significant increase in ion transport. This rapid increase in ion transport was transient and related to bicarbonate secretion. Conclusion The current data suggest that porcine vocal folds immediately increase bicarbonate secretion following exposure to acid. Bicarbonate secretion may act to neutralize acid. These findings contribute to the identification of the mechanisms underlying vocal fold defense to reflux and offer implications for the development of treatments for reflux-induced vocal fold injury. PMID:22086905

  3. Substrate specificity and transport mechanism of amino-acid transceptor Slimfast from Aedes aegypti

    PubMed Central

    Boudko, Dmitri Y.; Tsujimoto, Hitoshi; Rodriguez, Stacy D.; Meleshkevitch, Ella A.; Price, David P.; Drake, Lisa L.; Hansen, Immo A.

    2015-01-01

    Anautogenous mosquitoes depend on vertebrate blood as nutrient source for their eggs. A highly efficient set of membrane transporters mediates the massive movement of nutrient amino acids between mosquito tissues after a blood meal. Here we report the characterization of the amino-acid transporter Slimfast (Slif) from the yellow-fever mosquito Aedes aegypti using codon-optimized heterologous expression. Slif is a well-known component of the target-of-rapamycin signalling pathway and fat body nutrient sensor, but its substrate specificity and transport mechanism were unknown. We found that Slif transports essential cationic and neutral amino acids with preference for arginine. It has an unusual dual-affinity mechanism with only the high affinity being Na+ dependent. Tissue-specific expression and blood meal-dependent regulation of Slif are consistent with conveyance of essential amino acids from gut to fat body. Slif represents a novel transport system and type of transceptor for sensing and transporting essential amino acids during mosquito reproduction. PMID:26449545

  4. OST alpha-OST beta: a key membrane transporter of bile acids and conjugated steroids.

    PubMed

    Ballatori, Nazzareno; Li, Na; Fang, Fang; Boyer, James L; Christian, Whitney V; Hammond, Christine L

    2009-01-01

    The organic solute and steroid transporter, Ost alpha-Ost beta, is an unusual heteromeric carrier that appears to play a central role in the transport of bile acids, conjugated steroids, and structurally-related molecules across the basolateral membrane of many epithelial cells. The transporter's substrate specificity, transport mechanism, tissue distribution, subcellular localization, transcriptional regulation, as well as the phenotype of the recently characterized Ost alpha-deficient mice all strongly support this model. In particular, the Ost alpha-deficient mice display a marked defect in intestinal bile acid and conjugated steroid absorption; a decrease in bile acid pool size and serum bile acid levels; altered intestinal, hepatic and renal disposition of known substrates of the transporter; and altered serum triglyceride, cholesterol, and glucose levels. Collectively, the data indicate that Ost alpha-Ost beta is essential for bile acid and sterol disposition, and suggest that the carrier may be involved in human conditions related to imbalances in bile acid or lipid homeostasis.

  5. Light-activated amino acid transport in Halobacterium halobium envelope vesicles

    NASA Technical Reports Server (NTRS)

    Macdonald, R. E.; Lanyi, J. K.

    1977-01-01

    Vesicles prepared from Halobacterium halobium cell envelopes accumulate amino acids in response to light-induced electrical and chemical gradients. Nineteen of 20 commonly occurring amino acids have been shown to be actively accumulated by these vesicles in response to illumination or in response to an artificially created Na+ gradient. On the basis of shared common carriers the transport systems can be divided into eight classes, each responsible for the transport of one or several amino acids: arginine, lysine, histidine; asparagine, glutamine; alanine, glycine, threonine, serine; leucine, valine, isoleucine, methionine; phenylalanine, tyrosine, tryptophan; aspartate; glutamate; proline. Available evidence suggests that these carriers are symmetrical in that amino acids can be transported equally well in both directions across the vesicle membranes. A tentative working model to account for these observations is presented.

  6. The glutamate and neutral amino acid transporter family: physiological and pharmacological implications.

    PubMed

    Kanai, Yoshikatsu; Hediger, Matthias A

    2003-10-31

    The solute carrier family 1 (SLC1) is composed of five high affinity glutamate transporters, which exhibit the properties of the previously described system XAG-, as well as two Na+-dependent neutral amino acid transporters with characteristics of the so-called "ASC" (alanine, serine and cysteine). The SLC1 family members are structurally similar, with almost identical hydropathy profiles and predicted membrane topologies. The transporters have eight transmembrane domains and a structure reminiscent of a pore loop between the seventh and eighth domains [Neuron 21 (1998) 623]. However, each of these transporters exhibits distinct functional properties. Glutamate transporters mediate transport of L-Glu, L-Asp and D-Asp, accompanied by the cotransport of 3 Na+ and one 1 H+, and the countertransport of 1 K+, whereas ASC transporters mediate Na+-dependent exchange of small neutral amino acids such as Ala, Ser, Cys and Thr. Given the high concentrating capacity provided by the unique ion coupling pattern of glutamate transporters, they play crucial roles in protecting neurons against glutamate excitotoxicity in the central nervous system (CNS). The regulation and manipulation of their function is a critical issue in the pathogenesis and treatment of CNS disorders involving glutamate excitotoxicity. Loss of function of the glial glutamate transporter GLT1 (SLC1A2) has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS), resulting in damage of adjacent motor neurons. The importance of glial glutamate transporters in protecting neurons from extracellular glutamate was further demonstrated in studies of the slc1A2 glutamate transporter knockout mouse. The findings suggest that therapeutic upregulation of GLT1 may be beneficial in a variety of pathological conditions. Selective inhibition of the neuronal glutamate transporter EAAC1 (SLC1A1) but not the glial glutamate transporters may be of therapeutic interest, allowing blockage of glutamate exit from

  7. Greater Transport Efficiencies of the Membrane Fatty Acid Transporters FAT/CD36 and FATP4 Compared with FABPpm and FATP1 and Differential Effects on Fatty Acid Esterification and Oxidation in Rat Skeletal Muscle*

    PubMed Central

    Nickerson, James G.; Alkhateeb, Hakam; Benton, Carley R.; Lally, James; Nickerson, Jennifer; Han, Xiao-Xia; Wilson, Meredith H.; Jain, Swati S.; Snook, Laelie A.; Glatz, Jan F. C.; Chabowski, Adrian; Luiken, Joost J. F. P.; Bonen, Arend

    2009-01-01

    In selected mammalian tissues, long chain fatty acid transporters (FABPpm, FAT/CD36, FATP1, and FATP4) are co-expressed. There is controversy as to whether they all function as membrane-bound transporters and whether they channel fatty acids to oxidation and/or esterification. Among skeletal muscles, the protein expression of FABPpm, FAT/CD36, and FATP4, but not FATP1, correlated highly with the capacities for oxidative metabolism (r ≥ 0.94), fatty acid oxidation (r ≥ 0.88), and triacylglycerol esterification (r ≥ 0.87). We overexpressed independently FABPpm, FAT/CD36, FATP1, and FATP4, within a normal physiologic range, in rat skeletal muscle, to determine the effects on fatty acid transport and metabolism. Independent overexpression of each fatty acid transporter occurred without altering either the expression or plasmalemmal content of other fatty acid transporters. All transporters increased fatty acid transport, but FAT/CD36 and FATP4 were 2.3- and 1.7-fold more effective than FABPpm and FATP1, respectively. Fatty acid transporters failed to alter the rates of fatty acid esterification into triacylglycerols. In contrast, all transporters increased the rates of long chain fatty acid oxidation, but the effects of FABPpm and FAT/CD36 were 3-fold greater than for FATP1 and FATP4. Thus, fatty acid transporters exhibit different capacities for fatty acid transport and metabolism. In vivo, FAT/CD36 and FATP4 are the most effective fatty acid transporters, whereas FABPpm and FAT/CD36 are key for stimulating fatty acid oxidation. PMID:19380575

  8. Role of ion transporters in the bile acid-induced esophageal injury.

    PubMed

    Laczkó, Dorottya; Rosztóczy, András; Birkás, Klaudia; Katona, Máté; Rakonczay, Zoltán; Tiszlavicz, László; Róka, Richárd; Wittmann, Tibor; Hegyi, Péter; Venglovecz, Viktória

    2016-07-01

    Barrett's esophagus (BE) is considered to be the most severe complication of gastro-esophageal reflux disease (GERD), in which the prolonged, repetitive episodes of combined acidic and biliary reflux result in the replacement of the squamous esophageal lining by columnar epithelium. Therefore, the acid-extruding mechanisms of esophageal epithelial cells (EECs) may play an important role in the defense. Our aim was to identify the presence of acid/base transporters on EECs and to investigate the effect of bile acids on their expressions and functions. Human EEC lines (CP-A and CP-D) were acutely exposed to bile acid cocktail (BAC) and the changes in intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i) were measured by microfluorometry. mRNA and protein expression of ion transporters was investigated by RT-PCR, Western blot, and immunohistochemistry. We have identified the presence of a Na(+)/H(+) exchanger (NHE), Na(+)/HCO3 (-) cotransporter (NBC), and a Cl(-)-dependent HCO3 (-) secretory mechanism in CP-A and CP-D cells. Acute administration of BAC stimulated HCO3 (-) secretion in both cell lines and the NHE activity in CP-D cells by an inositol triphosphate-dependent calcium release. Chronic administration of BAC to EECs increased the expression of ion transporters compared with nontreated cells. A similar expression pattern was observed in biopsy samples from BE compared with normal epithelium. We have shown that acute administration of bile acids differently alters ion transport mechanisms of EECs, whereas chronic exposure to bile acids increases the expression of acid/base transporters. We speculate that these adaptive processes of EECs represent an important mucosal defense against the bile acid-induced epithelial injury. PMID:27198194

  9. Bibliography for acid-rock drainage and selected acid-mine drainage issues related to acid-rock drainage from transportation activities

    USGS Publications Warehouse

    Bradley, Michael W.; Worland, Scott C.

    2015-01-01

    Acid-rock drainage occurs through the interaction of rainfall on pyrite-bearing formations. When pyrite (FeS2) is exposed to oxygen and water in mine workings or roadcuts, the mineral decomposes and sulfur may react to form sulfuric acid, which often results in environmental problems and potential damage to the transportation infrastructure. The accelerated oxidation of pyrite and other sulfidic minerals generates low pH water with potentially high concentrations of trace metals. Much attention has been given to contamination arising from acid mine drainage, but studies related to acid-rock drainage from road construction are relatively limited. The U.S. Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to evaluate the occurrence and processes controlling acid-rock drainage and contaminant transport from roadcuts in Tennessee. The basic components of acid-rock drainage resulting from transportation activities are described and a bibliography, organized by relevant categories (remediation, geochemical, microbial, biological impact, and secondary mineralization) is presented.

  10. Fatty Acid-binding Proteins Transport N-Acylethanolamines to Nuclear Receptors and Are Targets of Endocannabinoid Transport Inhibitors*

    PubMed Central

    Kaczocha, Martin; Vivieca, Stephanie; Sun, Jing; Glaser, Sherrye T.; Deutsch, Dale G.

    2012-01-01

    N-Acylethanolamines (NAEs) are bioactive lipids that engage diverse receptor systems. Recently, we identified fatty acid-binding proteins (FABPs) as intracellular NAE carriers. Here, we provide two new functions for FABPs in NAE signaling. We demonstrate that FABPs mediate the nuclear translocation of the NAE oleoylethanolamide, an agonist of nuclear peroxisome proliferator-activated receptor α (PPARα). Antagonism of FABP function through chemical inhibition, dominant-negative approaches, or shRNA-mediated knockdown reduced PPARα activation, confirming a requisite role for FABPs in this process. In addition, we show that NAE analogs, traditionally employed as inhibitors of the putative endocannabinoid transmembrane transporter, target FABPs. Support for the existence of the putative membrane transporter stems primarily from pharmacological inhibition of endocannabinoid uptake by such transport inhibitors, which are widely employed in endocannabinoid research despite lacking a known cellular target(s). Our approach adapted FABP-mediated PPARα signaling and employed in vitro binding, arachidonoyl-[1-14C]ethanolamide ([14C]AEA) uptake, and FABP knockdown to demonstrate that transport inhibitors exert their effects through inhibition of FABPs, thereby providing a molecular rationale for the underlying physiological effects of these compounds. Identification of FABPs as targets of transport inhibitors undermines the central pharmacological support for the existence of an endocannabinoid transmembrane transporter. PMID:22170058

  11. Putative ABC transporter responsible for acetic acid resistance in Acetobacter aceti.

    PubMed

    Nakano, Shigeru; Fukaya, Masahiro; Horinouchi, Sueharu

    2006-01-01

    Two-dimensional gel electrophoretic analysis of the membrane fraction of Acetobacter aceti revealed the presence of several proteins that were produced in response to acetic acid. A 60-kDa protein, named AatA, which was mostly induced by acetic acid, was prepared; aatA was cloned on the basis of its NH2-terminal amino acid sequence. AatA, consisting of 591 amino acids and containing ATP-binding cassette (ABC) sequences and ABC signature sequences, belonged to the ABC transporter superfamily. The aatA mutation with an insertion of the neomycin resistance gene within the aatA coding region showed reduced resistance to acetic acid, formic acid, propionic acid, and lactic acid, whereas the aatA mutation exerted no effects on resistance to various drugs, growth at low pH (adjusted with HCl), assimilation of acetic acid, or resistance to citric acid. Introduction of plasmid pABC101 containing aatA under the control of the Escherichia coli lac promoter into the aatA mutant restored the defect in acetic acid resistance. In addition, pABC101 conferred acetic acid resistance on E. coli. These findings showed that AatA was a putative ABC transporter conferring acetic acid resistance on the host cell. Southern blot analysis and subsequent nucleotide sequencing predicted the presence of aatA orthologues in a variety of acetic acid bacteria belonging to the genera Acetobacter and Gluconacetobacter. The fermentation with A. aceti containing aatA on a multicopy plasmid resulted in an increase in the final yield of acetic acid.

  12. New mechanisms that regulate Saccharomyces cerevisiae short peptide transporter achieve balanced intracellular amino acid concentrations.

    PubMed

    Melnykov, Artem V

    2016-01-01

    The budding yeast Saccharomyces cerevisiae is able to take up large quantities of amino acids in the form of di- and tripeptides via a short peptide transporter, Ptr2p. It is known that PTR2 can be induced by certain peptides and amino acids, and the mechanisms governing this upregulation are understood at the molecular level. We describe two new opposing mechanisms of regulation that emphasize potential toxicity of amino acids: the first is upregulation of PTR2 in a population of cells, caused by amino acid secretion that accompanies peptide uptake; the second is loss of Ptr2p activity, due to transporter internalization following peptide uptake. Our findings emphasize the importance of proper amino acid balance in the cell and extend understanding of peptide import regulation in yeast.

  13. Defective canalicular transport and toxicity of dietary ursodeoxycholic acid in the abcb11-/- mouse: transport and gene expression studies.

    PubMed

    Wang, Renxue; Liu, Lin; Sheps, Jonathan A; Forrest, Dana; Hofmann, Alan F; Hagey, Lee R; Ling, Victor

    2013-08-15

    The bile salt export pump (BSEP), encoded by the abcb11 gene, is the major canalicular transporter of bile acids from the hepatocyte. BSEP malfunction in humans causes bile acid retention and progressive liver injury, ultimately leading to end-stage liver failure. The natural, hydrophilic, bile acid ursodeoxycholic acid (UDCA) is efficacious in the treatment of cholestatic conditions, such as primary biliary cirrhosis and cholestasis of pregnancy. The beneficial effects of UDCA include promoting bile flow, reducing hepatic inflammation, preventing apoptosis, and maintaining mitochondrial integrity in hepatocytes. However, the role of BSEP in mediating UDCA efficacy is not known. Here, we used abcb11 knockout mice (abcb11-/-) to test the effects of acute and chronic UDCA administration on biliary secretion, bile acid composition, liver histology, and liver gene expression. Acutely infused UDCA, or its taurine conjugate (TUDC), was taken up by the liver but retained, with negligible biliary output, in abcb11-/- mice. Feeding UDCA to abcb11-/- mice led to weight loss, retention of bile acids, elevated liver enzymes, and histological damage to the liver. Semiquantitative RT-PCR showed that genes encoding Mdr1a and Mdr1b (canalicular) as well as Mrp4 (basolateral) transporters were upregulated in abcb11-/- mice. We concluded that infusion of UDCA and TUDC failed to induce bile flow in abcb11-/- mice. UDCA fed to abcb11-/- mice caused liver damage and the appearance of biliary tetra- and penta-hydroxy bile acids. Supplementation with UDCA in the absence of Bsep caused adverse effects in abcb11-/- mice. PMID:23764895

  14. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, Diane M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  15. Perfluoroalkyl Acid Concentrations in Blood Samples Subjected to Transportation and Processing Delay

    PubMed Central

    Bach, Cathrine Carlsen; Henriksen, Tine Brink; Bossi, Rossana; Bech, Bodil Hammer; Fuglsang, Jens; Olsen, Jørn; Nohr, Ellen Aagaard

    2015-01-01

    Background In studies of perfluoroalkyl acids, the validity and comparability of measured concentrations may be affected by differences in the handling of biospecimens. We aimed to investigate whether measured plasma levels of perfluoroalkyl acids differed between blood samples subjected to delay and transportation prior to processing and samples with immediate processing and freezing. Methods Pregnant women recruited at Aarhus University Hospital, Denmark, (n = 88) provided paired blood samples. For each pair of samples, one was immediately processed and plasma was frozen, and the other was delayed and transported as whole blood before processing and freezing of plasma (similar to the Danish National Birth Cohort). We measured 12 perfluoroalkyl acids and present results for compounds with more than 50% of samples above the lower limit of quantification. Results For samples taken in the winter, relative differences between the paired samples ranged between -77 and +38% for individual perfluoroalkyl acids. In most cases concentrations were lower in the delayed and transported samples, e.g. the relative difference was -29% (95% confidence interval -30; -27) for perfluorooctane sulfonate. For perfluorooctanoate there was no difference between the two setups [corresponding estimate 1% (0, 3)]. Differences were negligible in the summer for all compounds. Conclusions Transport of blood samples and processing delay, similar to conditions applied in some large, population-based studies, may affect measured perfluoroalkyl acid concentrations, mainly when outdoor temperatures are low. Attention to processing conditions is needed in studies of perfluoroalkyl acid exposure in humans. PMID:26356420

  16. Genetic evidence of a high-affinity cyanuric acid transport system in Pseudomonas sp. ADP.

    PubMed

    Platero, Ana I; Santero, Eduardo; Govantes, Fernando

    2014-03-01

    The Pseudomonas sp. ADP plasmid pADP-1 encodes the activities involved in the hydrolytic degradation of the s-triazine herbicide atrazine. Here, we explore the presence of a specific transport system for the central intermediate of the atrazine utilization pathway, cyanuric acid, in Pseudomonas sp. ADP. Growth in fed-batch cultures containing limiting cyanuric acid concentrations is consistent with high-affinity transport of this substrate. Acquisition of the ability to grow at low cyanuric acid concentrations upon conjugal transfer of pADP1 to the nondegrading host Pseudomonas putida KT2442 suggests that all activities required for this phenotype are encoded in this plasmid. Co-expression of the pADP1-borne atzDEF and atzTUVW genes, encoding the cyanuric acid utilization pathway and the subunits of an ABC-type solute transport system, in P. putida KT2442 was sufficient to promote growth at cyanuric acid concentrations as low as 50 μM in batch culture. Taken together, our results strongly suggest that the atzTUVW gene products are involved in high-affinity transport of cyanuric acid.

  17. Proton-dependent glutamine uptake by aphid bacteriocyte amino acid transporter ApGLNT1.

    PubMed

    Price, Daniel R G; Wilson, Alex C C; Luetje, Charles W

    2015-10-01

    Aphids house large populations of the gammaproteobacterial symbiont Buchnera aphidicola in specialized bacteriocyte cells. The combined biosynthetic capability of the holobiont (Acyrthosiphon pisum and Buchnera) is sufficient for biosynthesis of all twenty protein coding amino acids, including amino acids that animals alone cannot synthesize; and that are present at low concentrations in A. pisum's plant phloem sap diet. Collaborative holobiont amino acid biosynthesis depends on glutamine import into bacteriocytes, which serves as a nitrogen-rich amino donor for biosynthesis of other amino acids. Recently, we characterized A. pisum glutamine transporter 1 (ApGLNT1), a member of the amino acid/auxin permease family, as the dominant bacteriocyte plasma membrane glutamine transporter. Here we show ApGLNT1 to be structurally and functionally related to mammalian proton-dependent amino acid transporters (PATs 1-4). Using functional expression in Xenopus laevis oocytes, combined with two-electrode voltage clamp electrophysiology we demonstrate that ApGLNT1 is electrogenic and that glutamine induces large inward currents. ApGLNT1 glutamine induced currents are dependent on external glutamine concentration, proton (H+) gradient across the membrane, and membrane potential. Based on these transport properties, ApGLNT1-mediated glutamine uptake into A. pisum bacteriocytes can be regulated by changes in either proton gradients across the plasma membrane or membrane potential. PMID:26028424

  18. Prohibitin/annexin 2 interaction regulates fatty acid transport in adipose tissue

    PubMed Central

    Salameh, Ahmad; Daquinag, Alexes C.; Staquicini, Daniela I.; An, Zhiqiang; Pasqualini, Renata; Kolonin, Mikhail G.

    2016-01-01

    We have previously identified prohibitin (PHB) and annexin A2 (ANX2) as proteins interacting on the surface of vascular endothelial cells in white adipose tissue (WAT) of humans and mice. Here, we demonstrate that ANX2 and PHB also interact in adipocytes. Mice lacking ANX2 have normal WAT vascularization, adipogenesis, and glucose metabolism but display WAT hypotrophy due to reduced fatty acid uptake by WAT endothelium and adipocytes. By using cell culture systems in which ANX2/PHB binding is disrupted either genetically or through treatment with a blocking peptide, we show that fatty acid transport efficiency relies on this protein complex. We also provide evidence that the interaction between ANX2 and PHB mediates fatty acid transport from the endothelium into adipocytes. Moreover, we demonstrate that ANX2 and PHB form a complex with the fatty acid transporter CD36. Finally, we show that the colocalization of PHB and CD36 on adipocyte surface is induced by extracellular fatty acids. Together, our results suggest that an unrecognized biochemical interaction between ANX2 and PHB regulates CD36-mediated fatty acid transport in WAT, thus revealing a new potential pathway for intervention in metabolic diseases. PMID:27468426

  19. Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

    PubMed

    Wei, Xiaorong; Shao, Mingan; Du, Lina; Horton, Robert

    2014-12-01

    Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

  20. Variation in indole-3-acetic acid transport and its relationship with growth in etiolated lupin hypocotyls.

    PubMed

    Nicolás, Juana Inés López; Acosta, Manuel; Sánchez-Bravo, José

    2007-07-01

    The relationship between the variation in polar auxin transport (PAT) and elongating growth in etiolated Lupinus albus hypocotyls was investigated. Parameters of auxin transport, such as the amount transported, intensity of the transport and sensitivity to 1-N-naphthylphthalamic acid (NPA) inhibition were measured in isolated sections from different sites (apical, middle and basal) along the hypocotyls in seedlings of different ages. Auxin transport was studied by applying radioactive indole-3-acetic acid (IAA) to upright and inverted sections. Basipetal transport was much higher than acropetal and very sensitive to NPA inhibition, which indicates that transport is polarized. Polarity was expressed as the NPA-induced inhibition and the basipetal/acropetal ratio. As a rule, both the amount of IAA transported and the polarity varied with the age of the seedlings, with values increasing from 3 to 5d and then decreasing. Both parameters were higher in apical (where most growth is localized) than in middle and basal regions, although this longitudinal gradient tended to disappear with aging as hypocotyl growth slowed and finally ceased. The application of NPA did not modify hypocotyl elongation in 5-d-old intact seedlings. Derooting of the seedlings drastically reduced elongation in the control, while NPA partially restored the growth, which suggests that NPA induces an increase in auxin in the elongation region. These results suggest that a basipetally decreasing gradient in PAT along the hypocotyl, which changes with age, may be responsible for auxin distribution pattern controlling growth.

  1. Carrier-mediated placental transport of cimetidine and valproic acid across differentiating JEG-3 cell layers.

    PubMed

    Ikeda, K; Ueda, C; Yamada, K; Nakamura, A; Hatsuda, Y; Kawanishi, S; Nishii, S; Ogawa, M

    2015-07-01

    Human choriocarcinoma has been used as a model to study trophoblast transcellular drug transport in the placenta. Previous models had limitations regarding low molecular weight drug transport through the intracellular gap junction. The purpose of this study was to evaluate placental carrier-mediated transport across a differentiating JEG-3 choriocarcinoma cell (DJEGs) layer model in which the intracellular gap junction was restricted. Cimetidine is the substrate of an efflux transporter, breast cancer resistance protein (BCRP). BCRP highly expressed in the placenta, and its function in the DJEGs model was investigated. In addition, the placental drug transport of another efflux transporter, multidrug resistance-associated proteins (MRPs), and an influx transporter, monocarboxylate transporter (MCT), were examined with various substrates. Cimetidine permeated from the fetal side to the maternal side at significantly high levels and saturated in a dose-dependent manner. The permeability coefficient of a MRP substrate, fluorescein, across the DJEGs model was significantly increased by inhibiting MRP function with probenecid. On the other hand, permeation in the influx direction to the fetal side with a substrate of MCT, valproic acid, had a gentle dose-dependent saturation. These findings suggest that the DJEGs model could be used to evaluate transcellular placental drug transport mediated by major placental transporters.

  2. Characteristics of Mammalian Rh Glycoproteins (SLC42 transporters) and Their Role in Acid-Base Transport

    PubMed Central

    Nakhoul, Nazih L.; Hamm, L. Lee

    2012-01-01

    The mammalian Rh glycoproteins belong to the solute transporter family SLC42 and include RhAG, present in red blood cells, and two non-erythroid members RhBG and RhCG that are expressed in various tissues, including kidney, liver, skin and the GI tract. The Rh proteins in the red blood cell form an “Rh complex” made up of one D-subunit, one CE-subunit and two RhAG subunits. The Rh complex has a well-known antigenic effect but also contributes to the stability of the red cell membrane. RhBG and RhCG are related to the NH4+ transporters of the yeast and bacteria but their exact function is yet to be determined. This review describes the expression and molecular properties of these membrane proteins and their potential role as NH3/NH4+ and CO2 transporters. The likelihood that these proteins transport gases such as CO2 or NH3 is novel and significant. The review also describes the physiological importance of these proteins and their relevance to human disease. PMID:23506896

  3. Transmembrane domain II of the human bile acid transporter SLC10A2 coordinates sodium translocation.

    PubMed

    Sabit, Hairat; Mallajosyula, Sairam S; MacKerell, Alexander D; Swaan, Peter W

    2013-11-01

    Human apical sodium-dependent bile acid transporter (hASBT, SLC10A2) is responsible for intestinal reabsorption of bile acids and plays a key role in cholesterol homeostasis. We used a targeted and systematic approach to delineate the role of highly conserved transmembrane helix 2 on the expression and function of hASBT. Cysteine mutation significantly depressed transport activity for >60% of mutants without affecting cell surface localization of the transporter. All mutants were inaccessible toward chemical modification by membrane-impermeant MTSET reagent, strongly suggesting that transmembrane 2 (TM2) plays an indirect role in bile acid substrate translocation. Both bile acid uptake and sodium dependence of TM2 mutants revealed a distinct α-helical periodicity. Kinetic studies with conservative and non-conservative mutants of sodium sensitive residues further underscored the importance of Gln(75), Phe(76), Met(79), Gly(83), Leu(86), Phe(90), and Asp(91) in hASBT function. Computational analysis indicated that Asp(91) may coordinate with sodium during the transport cycle. Combined, our data propose that a consortium of sodium-sensitive residues along with previously reported residues (Thr(134), Leu(138), and Thr(149)) from TM3 may form the sodium binding and translocation pathway. Notably, residues Gln(75), Met(79), Thr(82), and Leu(86) from TM2 are highly conserved in TM3 of a putative remote bacterial homologue (ASBTNM), suggesting a universal mechanism for the SLC10A transporter family.

  4. Tuning transport selectivity of ionic species by phosphoric acid gradient in positively charged nanochannel membranes.

    PubMed

    Yang, Meng; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Fan, Xin; Liu, Wei; Liu, Xizhen; Liu, Jianbo; Huang, Jin

    2015-02-01

    The transport of ionic species through a nanochannel plays important roles in fundamental research and practical applications of the nanofluidic device. Here, we demonstrated that ionic transport selectivity of a positively charged nanochannel membrane can be tuned under a phosphoric acid gradient. When phosphoric acid solution and analyte solution were connected by the positively charged nanochannel membrane, the faster-moving analyte through the positively charged nanochannel membrane was the positively charged dye (methylviologen, MV(2+)) instead of the negatively charged dye (1,5-naphthalene disulfonate, NDS(2-)). In other words, a reversed ion selectivity of the nanochannel membranes can be found. It can be explained as a result of the combination of diffusion, induced electroosmosis, and induced electrophoresis. In addition, the influencing factors of transport selectivity, including concentration of phosphoric acid, penetration time, and volume of feed solution, were also investigated. The results showed that the transport selectivity can further be tuned by adjusting these factors. As a method of tuning ionic transport selectivity by establishing phosphoric acid gradient, it will be conducive to improving the separation of ionic species. PMID:25557761

  5. Uptake of sialic acid by human erythrocyte. Characterization of a transport system.

    PubMed

    Bulai, Tatiana; Bratosin, Daniela; Artenie, Vlad; Montreuil, Jean

    2003-01-01

    Upon incubation of human red blood cells (RBC) with [4-9-14C] N-acetylneuraminic acid, the cells incorporated this sugar, as demonstrated by the identification of labelled N-acetylmannosamine in the cytosol, as a result of the action of the sialic acid pyruvate-lyase we discovered previously (Biochimie 84 (2002) 655). The mechanism is saturable and indicates the presence of a limited number of transporter molecules in the RBC membrane. This transport process may have relevance to the desialylation of membrane glycoconjugates which occurs during ageing of erythrocytes.

  6. Reactive iron transport in an acidic mountain stream in Summit County, Colorado: A hydrologic perspective

    USGS Publications Warehouse

    McKnight, Diane M.; Bencala, K.E.

    1989-01-01

    A pH perturbation experiment was conducted in an acidic, metal-enriched, mountain stream to identify relative rates of chemical and hydrologic processes as they influence iron transport. During the experiment the pH was lowered from 4.2 to 3.2 for three hours by injection of sulfuric acid. Amorphous iron oxides are abundant on the streambed, and dissolution and photoreduction reactions resulted in a rapid increase in the dissolved iron concentration. The increase occurred simultaneously with the decrease in pH. Ferrous iron was the major aqueous iron species. The changes in the iron concentration during the experiment indicate that variation exists in the solubility properties of the hydrous iron oxides on the streambed with dissolution of at least two compartments of hydrous iron oxides contributing to the iron pulse. Spatial variations of the hydrologic properties along the stream were quantified by simulating the transport of a coinjected tracer, lithium. A simulation of iron transport, as a conservative solute, indicated that hydrologie transport had a significant role in determining downstream changes in the iron pulse. The rapidity of the changes in iron concentration indicates that a model based on dynamic equilibrium may be adequate for simulating iron transport in acid streams. A major challenge for predictive solute transport models of geochemical processes may be due to substantial spatial and seasonal variations in chemical properties of the reactive hydrous oxides in such streams, and in the physical and hydrologic properties of the stream. ?? 1989.

  7. Efficient Transport of Nitric Acid in Urban Plumes Observed Over the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Neuman, J.; Parrish, D.; Trainer, M.; Brown, S.; Fehsenfeld, F.; Flocke, F.; Holloway, J.; Nowak, J.; Ryerson, T.; Stark, H.; Swanson, A.

    2005-12-01

    The processing of anthropogenic NOx emissions from urban and industrial sources was studied using data collected from an instrumented aircraft flying over the east coast of the United States and over the North Atlantic Ocean. Pollutants were sampled from the National Oceanic and Atmospheric Administration WP-3 aircraft during the International Consortium for Atmospheric Research on Transport and Transformation study in July and August, 2004. Fast response measurements of reactive nitrogen compounds and carbon monoxide (CO) were obtained in crosswind transects of urban plumes in the New York City and Boston source regions and up to 1600 km downwind. The magnitude and geographical extent of the effects of NOx and its oxidation products depend on the NOx oxidation rates and pathways and on the atmospheric lifetime and loss mechanisms of the resulting secondary products. In urban plumes that were sampled further than 200 km from New York City and Boston, nitric acid was always the most abundant reactive nitrogen species and usually accounted for over 80% of the sum of NOx and its oxidation products. During this study, frequently plumes were transported above the marine boundary layer at a few hundred meters altitude and were decoupled from the surface, which allowed efficient transport of nitric acid that is not commonly observed at the surface, in the continental boundary layer, or in the free troposphere. In plumes observed over the remote North Atlantic Ocean, nitric acid mixing ratios were high (up to 50 ppbv) and the ratio of CO to reactive nitrogen changed little with plume age, reflecting the small depositional loss of nitric acid. Many of the photochemically aged urban plumes were characterized by the presence of tens of ppbv of nitric acid for several days. As a consequence of the slow removal of nitric acid from these air masses, NOx can be reformed from nitric acid photolysis and OH oxidation. The efficient transport of nitric acid may also allow for

  8. Transport and metabolism of fumaric acid in Saccharomyces cerevisiae in aerobic glucose-limited chemostat culture.

    PubMed

    Shah, Mihir V; van Mastrigt, Oscar; Heijnen, Joseph J; van Gulik, Walter M

    2016-04-01

    Currently, research is being focused on the industrial-scale production of fumaric acid and other relevant organic acids from renewable feedstocks via fermentation, preferably at low pH for better product recovery. However, at low pH a large fraction of the extracellular acid is present in the undissociated form, which is lipophilic and can diffuse into the cell. There have been no studies done on the impact of high extracellular concentrations of fumaric acid under aerobic conditions in S. cerevisiae, which is a relevant issue to study for industrial-scale production. In this work we studied the uptake and metabolism of fumaric acid in S. cerevisiae in glucose-limited chemostat cultures at a cultivation pH of 3.0 (pH < pK). Steady states were achieved with different extracellular levels of fumaric acid, obtained by adding different amounts of fumaric acid to the feed medium. The experiments were carried out with the wild-type S. cerevisiae CEN.PK 113-7D and an engineered S. cerevisiae ADIS 244 expressing a heterologous dicarboxylic acid transporter (DCT-02) from Aspergillus niger, to examine whether it would be capable of exporting fumaric acid. We observed that fumaric acid entered the cells most likely via passive diffusion of the undissociated form. Approximately two-thirds of the fumaric acid in the feed was metabolized together with glucose. From metabolic flux analysis, an increased ATP dissipation was observed only at high intracellular concentrations of fumarate, possibly due to the export of fumarate via an ABC transporter. The implications of our results for the industrial-scale production of fumaric acid are discussed. PMID:26683700

  9. Modeling uranium transport in acidic contaminated groundwater with base addition

    SciTech Connect

    Zhang, Fan; Luo, Wensui; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip; Gu, Baohua

    2011-01-01

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  10. Modeling uranium transport in acidic contaminated groundwater with base addition.

    PubMed

    Zhang, Fan; Luo, Wensui; Parker, Jack C; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2011-06-15

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO(3)(-), SO(4)(2-), U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  11. Models for gibberellic acid transport and enzyme production and transport in the aleurone layer of barley.

    PubMed

    O'Brien, Ricky; Fowkes, Nev; Bassom, Andrew P

    2010-11-01

    Gibberellins are growth hormones produced in the embryo of grain released during germination. They promote growth through the production of enzymes in the aleurone layer surrounding the endosperm. These enzymes then diffuse into the endosperm and produce the sugars required by the growing acrospire. Here we model the transport of gibberellins into and along the aleurone layer, the consequent production of enzymes, and their transport into the endosperm. Simple approximate solutions of the governing equations are obtained which suggest that the enzymes are released immediately behind a gibberellin front which travels with almost constant speed along the aleurone layer. The model also suggests that this propagation speed is determined primarily by conditions near the scutellum-aleurone junction, which may enable the embryo to actively control the germination process.

  12. Transporters for cationic amino acids in animal cells: discovery, structure, and function.

    PubMed

    Devés, R; Boyd, C A

    1998-04-01

    The structure and function of the four cationic amino acid transporters identified in animal cells are discussed. The systems differ in specificity, cation dependence, and physiological role. One of them, system y+, is selective for cationic amino acids, whereas the others (B[0,+], b[0,+], and y+ L) also accept neutral amino acids. In recent years, cDNA clones related to these activities have been isolated. Thus two families of proteins have been identified: 1) CAT or cationic amino acid transporters and 2) BAT or broad-scope transport proteins. In the CAT family, three genes encode for four different isoforms [CAT-1, CAT-2A, CAT-2(B) and CAT-3]; these are approximately 70-kDa proteins with multiple transmembrane segments (12-14), and despite their structural similarity, they differ in tissue distribution, kinetics, and regulatory properties. System y+ is the expression of the activity of CAT transporters. The BAT family includes two isoforms (rBAT and 4F2hc); these are 59- to 78-kDa proteins with one to four membrane-spanning segments, and it has been proposed that these proteins act as transport regulators. The expression of rBAT and 4F2hc induces system b[0,+] and system y+ L activity in Xenopus laevis oocytes, respectively. The roles of these transporters in nutrition, endocrinology, nitric oxide biology, and immunology, as well as in the genetic diseases cystinuria and lysinuric protein intolerance, are reviewed. Experimental strategies, which can be used in the kinetic characterization of coexpressed transporters, are also discussed.

  13. Chronic intermittent psychological stress promotes macrophage reverse cholesterol transport by impairing bile acid absorption in mice

    PubMed Central

    Silvennoinen, Reija; Quesada, Helena; Kareinen, Ilona; Julve, Josep; Kaipiainen, Leena; Gylling, Helena; Blanco-Vaca, Francisco; Escola-Gil, Joan Carles; Kovanen, Petri T; Lee-Rueckert, Miriam

    2015-01-01

    Psychological stress is a risk factor for atherosclerosis, yet the pathophysiological mechanisms involved remain elusive. The transfer of cholesterol from macrophage foam cells to liver and feces (the macrophage-specific reverse cholesterol transport, m-RCT) is an important antiatherogenic pathway. Because exposure of mice to physical restraint, a model of psychological stress, increases serum levels of corticosterone, and as bile acid homeostasis is disrupted in glucocorticoid-treated animals, we investigated if chronic intermittent restraint stress would modify m-RCT by altering the enterohepatic circulation of bile acids. C57Bl/6J mice exposed to intermittent stress for 5 days exhibited increased transit through the large intestine and enhanced fecal bile acid excretion. Of the transcription factors and transporters that regulate bile acid homeostasis, the mRNA expression levels of the hepatic farnesoid X receptor (FXR), the bile salt export pump (BSEP), and the intestinal fibroblast growth factor 15 (FGF15) were reduced, whereas those of the ileal apical sodium-dependent bile acid transporter (ASBT), responsible for active bile acid absorption, remained unchanged. Neither did the hepatic expression of cholesterol 7α-hydroxylase (CYP7A1), the key enzyme regulating bile acid synthesis, change in the stressed mice. Evaluation of the functionality of the m-RCT pathway revealed increased fecal excretion of bile acids that had been synthesized from macrophage-derived cholesterol. Overall, our study reveals that chronic intermittent stress in mice accelerates m-RCT specifically by increasing fecal excretion of bile acids. This novel mechanism of m-RCT induction could have antiatherogenic potential under conditions of chronic stress. PMID:25969465

  14. Low brain ascorbic acid increases susceptibility to seizures in mouse models of decreased brain ascorbic acid transport and Alzheimer's disease.

    PubMed

    Warner, Timothy A; Kang, Jing-Qiong; Kennard, John A; Harrison, Fiona E

    2015-02-01

    Seizures are a known co-occurring symptom of Alzheimer's disease, and they can accelerate cognitive and neuropathological dysfunction. Sub-optimal vitamin C (ascorbic acid) deficiency, that is low levels that do not lead the sufferer to present with clinical signs of scurvy (e.g. lethargy, hemorrhage, hyperkeratosis), are easily obtainable with insufficient dietary intake, and may contribute to the oxidative stress environment of both Alzheimer's disease and epilepsy. The purpose of this study was to test whether mice that have diminished brain ascorbic acid in addition to carrying human Alzheimer's disease mutations in the amyloid precursor protein (APP) and presenilin 1 (PSEN1) genes, had altered electrical activity in the brain (electroencephalography; EEG), and were more susceptible to pharmacologically induced seizures. Brain ascorbic acid was decreased in APP/PSEN1 mice by crossing them with sodium vitamin C transporter 2 (SVCT2) heterozygous knockout mice. These mice have an approximately 30% decrease in brain ascorbic acid due to lower levels of SVCT2 that supplies the brain with ASC. SVCT2+/-APP/PSEN1 mice had decreased ascorbic acid and increased oxidative stress in brain, increased mortality, faster seizure onset latency following treatment with kainic acid (10 mg/kg i.p.), and more ictal events following pentylenetetrazol (50 mg/kg i.p.) treatment. Furthermore, we report the entirely novel phenomenon that ascorbic acid deficiency alone increased the severity of kainic acid- and pentylenetetrazol-induced seizures. These data suggest that avoiding ascorbic acid deficiency may be particularly important in populations at increased risk for epilepsy and seizures, such as Alzheimer's disease.

  15. Low brain ascorbic acid increases susceptibility to seizures in mouse models of decreased brain ascorbic acid transport and Alzheimer's disease.

    PubMed

    Warner, Timothy A; Kang, Jing-Qiong; Kennard, John A; Harrison, Fiona E

    2015-02-01

    Seizures are a known co-occurring symptom of Alzheimer's disease, and they can accelerate cognitive and neuropathological dysfunction. Sub-optimal vitamin C (ascorbic acid) deficiency, that is low levels that do not lead the sufferer to present with clinical signs of scurvy (e.g. lethargy, hemorrhage, hyperkeratosis), are easily obtainable with insufficient dietary intake, and may contribute to the oxidative stress environment of both Alzheimer's disease and epilepsy. The purpose of this study was to test whether mice that have diminished brain ascorbic acid in addition to carrying human Alzheimer's disease mutations in the amyloid precursor protein (APP) and presenilin 1 (PSEN1) genes, had altered electrical activity in the brain (electroencephalography; EEG), and were more susceptible to pharmacologically induced seizures. Brain ascorbic acid was decreased in APP/PSEN1 mice by crossing them with sodium vitamin C transporter 2 (SVCT2) heterozygous knockout mice. These mice have an approximately 30% decrease in brain ascorbic acid due to lower levels of SVCT2 that supplies the brain with ASC. SVCT2+/-APP/PSEN1 mice had decreased ascorbic acid and increased oxidative stress in brain, increased mortality, faster seizure onset latency following treatment with kainic acid (10 mg/kg i.p.), and more ictal events following pentylenetetrazol (50 mg/kg i.p.) treatment. Furthermore, we report the entirely novel phenomenon that ascorbic acid deficiency alone increased the severity of kainic acid- and pentylenetetrazol-induced seizures. These data suggest that avoiding ascorbic acid deficiency may be particularly important in populations at increased risk for epilepsy and seizures, such as Alzheimer's disease. PMID:25616451

  16. Energization of amino acid transport in energy-depleted Ehrlich cells and plasma membrane vesicles.

    PubMed

    Ohsawa, M; Kilberg, M S; Kimmel, G; Christensen, H N

    1980-06-20

    We redirect attention to contributions to the energization, of the active transport of amino acids in the Ehrlich cell, beyond the known energization, by down-gradient comigration of Na+, beyond possible direct energization by coupling to ATP breakdown, and beyond known energization by exchange with prior accumulations of amino acids. We re-emphasize the uphill operation of System L, and by prior depletion of cellular amino acids show that this system must receive energy beyond that made available by their coupled exodus. After this depletion the Na+-indepdendent accumulation of the norbornane amino acid, 2-aminobicycloheptane-2-carboxylic acid becomes strongly subject to stimulation by incubation with glucose. Energy transfer between Systems A and L through the mutual substrate action of ordinary amino acids was minimized although not entirely avoided by the use of amino acid analogs specific to each system. When 2,4-dinitrophenol was included in the depleting treatment, and pyruvate, phenazine methosulfate, or glucose used for restoration, recovery of uptake of the norbornane amino acid was independent of external Na+ or K+ levels. Restoration or the uptake of 2-(methylamino)isobutyric acid was, however, decreased by omission of external K+. Contrary to an earlier finding, restoration of uptake of each of these amino acids was associated with distinct and usually correlated rises in cellular ATP levels. ATP addition failed to stimulate exodus of the norbornane amino acid from plasma membrane vesicles, although either NADH or phenazine methosulfate did stimulate exodus. ATP production and use is thus associated with transport energization although evidence for a direct role failed to appear.

  17. Extra-renal elimination of uric acid via intestinal efflux transporter BCRP/ABCG2.

    PubMed

    Hosomi, Atsushi; Nakanishi, Takeo; Fujita, Takuya; Tamai, Ikumi

    2012-01-01

    Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.

  18. Transepithelial transport of aliphatic carboxylic acids studied in Madin Darby canine kidney (MDCK) cell monolayers.

    PubMed

    Cho, M J; Adson, A; Kezdy, F J

    1990-04-01

    Transport of 14C-labeled acetic, propionic (PA), butyric, valeric, heptanoic (HA), and octanoic (OA) acids across the Madin Darby canine kidney (MDCK) epithelial cell monolayer grown on a porous polycarbonate membrane was studied in Hanks' balanced salt solution (HBSS) at 37 degrees C in both apical-to-basolateral and basolateral-to-apical directions. At micromolar concentrations of solutes, metabolic decomposition was significant as evidenced by [14C]CO2 production during the OA transport. The apparent permeability (Pe) indicates that as lipophilicity increases, diffusion across the "unstirred" boundary layer becomes rate limiting. In support of this notion, transport of OA and HA was enhanced by agitation, showed an activation energy of 3.7 kcal/mol for OA, and resulted in identical Pe values for both transport directions. Analysis of Pe changes with varying alkyl chain length resulted in a delta G of -0.68 +/- 0.09 kcal/mol for -CH2-group transfer from an aqueous phase to the MDCK cells. When the intercellular tight junctions were opened by the divalent chelator EGTA in Ca2+/Mg2(+)-free HBSS, transport of the fluid-phase marker Lucifer yellow greatly increased because of paracellular leakage. PA transport also showed a significant increase, but OA transport was independent of EGTA. Although albumin also undergoes paracellular transport in the presence of EGTA and OA binds strongly to albumin, OA transport in EGTA solution was unchanged by albumin. These observations indicate that transmembrane transport is the major mechanism for lipophilic substances. The present study, together with earlier work on the transport of polar substances, shows that the MDCK cell monolayer is an excellent model of the transepithelial transport barrier.

  19. Transepithelial transport of aliphatic carboxylic acids studied in Madin Darby canine kidney (MDCK) cell monolayers

    SciTech Connect

    Cho, M.J.; Adson, A.; Kezdy, F.J. )

    1990-04-01

    Transport of 14C-labeled acetic, propionic (PA), butyric, valeric, heptanoic (HA), and octanoic (OA) acids across the Madin Darby canine kidney (MDCK) epithelial cell monolayer grown on a porous polycarbonate membrane was studied in Hanks' balanced salt solution (HBSS) at 37{degrees}C in both apical-to-basolateral and basolateral-to-apical directions. At micromolar concentrations of solutes, metabolic decomposition was significant as evidenced by (14C)CO2 production during the OA transport. The apparent permeability (Pe) indicates that as lipophilicity increases, diffusion across the unstirred boundary layer becomes rate limiting. In support of this notion, transport of OA and HA was enhanced by agitation, showed an activation energy of 3.7 kcal/mol for OA, and resulted in identical Pe values for both transport directions. Analysis of Pe changes with varying alkyl chain length resulted in a delta G of -0.68 +/- 0.09 kcal/mol for -CH2-group transfer from an aqueous phase to the MDCK cells. When the intercellular tight junctions were opened by the divalent chelator EGTA in Ca2+/Mg2(+)-free HBSS, transport of the fluid-phase marker Lucifer yellow greatly increased because of paracellular leakage. PA transport also showed a significant increase, but OA transport was independent of EGTA. Although albumin also undergoes paracellular transport in the presence of EGTA and OA binds strongly to albumin, OA transport in EGTA solution was unchanged by albumin. These observations indicate that transmembrane transport is the major mechanism for lipophilic substances. The present study, together with earlier work on the transport of polar substances, shows that the MDCK cell monolayer is an excellent model of the transepithelial transport barrier.

  20. Substrate-specific effects of pirinixic acid derivatives on ABCB1-mediated drug transport

    PubMed Central

    Michaelis, Martin; Rothweiler, Florian; Wurglics, Mario; Aniceto, Natália; Dittrich, Michaela; Zettl, Heiko; Wiese, Michael; Wass, Mark; Ghafourian, Taravat; Schubert-Zsilavecz, Manfred; Cinatl, Jindrich

    2016-01-01

    Pirinixic acid derivatives, a new class of drug candidates for a range of diseases, interfere with targets including PPARα, PPARγ, 5-lipoxygenase (5-LO), and microsomal prostaglandin and E2 synthase-1 (mPGES1). Since 5-LO, mPGES1, PPARα, and PPARγ represent potential anti-cancer drug targets, we here investigated the effects of 39 pirinixic acid derivatives on prostate cancer (PC-3) and neuroblastoma (UKF-NB-3) cell viability and, subsequently, the effects of selected compounds on drug-resistant neuroblastoma cells. Few compounds affected cancer cell viability in low micromolar concentrations but there was no correlation between the anti-cancer effects and the effects on 5-LO, mPGES1, PPARα, or PPARγ. Most strikingly, pirinixic acid derivatives interfered with drug transport by the ATP-binding cassette (ABC) transporter ABCB1 in a drug-specific fashion. LP117, the compound that exerted the strongest effect on ABCB1, interfered in the investigated concentrations of up to 2μM with the ABCB1-mediated transport of vincristine, vinorelbine, actinomycin D, paclitaxel, and calcein-AM but not of doxorubicin, rhodamine 123, or JC-1. In silico docking studies identified differences in the interaction profiles of the investigated ABCB1 substrates with the known ABCB1 binding sites that may explain the substrate-specific effects of LP117. Thus, pirinixic acid derivatives may offer potential as drug-specific modulators of ABCB1-mediated drug transport. PMID:26887049

  1. Disposition and transportation of surplus radioactive low specific activity nitric acid. Volume 1, Environmental Assessment

    SciTech Connect

    1995-05-01

    DOE is deactivating the PUREX plant at Hanford; this will involve the disposition of about 692,000 liters (183,000 gallons) of surplus nitric acid contaminated with low levels of U and other radionuclides. The nitric acid, designated as low specific activity, is stored in 4 storage tanks at PUREX. Five principal alternatives were evaluated: transfer for reuse (sale to BNF plc), no action, continued storage in Hanford upgraded or new facility, consolidation of DOE surplus acid, and processing the LSA nitric acid as waste. The transfer to BNF plc is the preferred alternative. From the analysis, it is concluded that the proposed disposition and transportation of the acid does not constitute a major federal action significantly affecting the quality of the human environment within the meaning of NEPA; therefore an environmental impact statement is not required.

  2. Cellular distribution of the neutral amino acid transporter subtype ASCT2 in mouse brain.

    PubMed

    Gliddon, Catherine M; Shao, Zongjun; LeMaistre, Jillian L; Anderson, Christopher M

    2009-01-01

    ASCT2 is an ASC (alanine-, serine-, cysteine-preferring) neutral amino acid exchanger that may regulate CNS function by transporting amino acid substrates including L-serine, L-cysteine, L-glutamine, L-glutamate and D-serine. Despite the potentially important role of ASCT2 in influencing metabolic and signaling functions of these amino acids in brain, there has been little description of its distribution in brain tissue. We employed a commercially available human ASCT2 antibody in immunohistochemistry studies in adult mouse brain and found a wide regional distribution for ASCT2 that was limited to dendrites labeled by anti-microtubule-associated protein-2 in cortex, hippocampus and striatum. No ASCT2 immunoreactivity was observed in areas labeled by antibodies against a neuronal cell body marker (NeuN), or either of the astrocyte markers, glial fibrillary acidic protein or S100beta. In cerebellum both Purkinje cell bodies and dendrites were positive for ASCT2 immunoreactivity. In support of a dendritic localization for ASCT2 in cortex, low affinity (K(T) > 1 mM), Na(+)-dependent D-serine and L-glutamine uptake characteristic of ASCT2-mediated transport was observed in P2 synaptosomal preparations. These results suggest that ASCT2 may be an important neuronal neutral amino acid transporter and highlight a discrepancy between findings of astrocyte ASCT2 function in tissue culture and brain in situ.

  3. Intracellular pH regulation by acid-base transporters in mammalian neurons

    PubMed Central

    Ruffin, Vernon A.; Salameh, Ahlam I.; Boron, Walter F.; Parker, Mark D.

    2014-01-01

    Intracellular pH (pHi) regulation in the brain is important in both physiological and physiopathological conditions because changes in pHi generally result in altered neuronal excitability. In this review, we will cover 4 major areas: (1) The effect of pHi on cellular processes in the brain, including channel activity and neuronal excitability. (2) pHi homeostasis and how it is determined by the balance between rates of acid loading (JL) and extrusion (JE). The balance between JE and JL determine steady-state pHi, as well as the ability of the cell to defend pHi in the face of extracellular acid-base disturbances (e.g., metabolic acidosis). (3) The properties and importance of members of the SLC4 and SLC9 families of acid-base transporters expressed in the brain that contribute to JL (namely the Cl-HCO3 exchanger AE3) and JE (the Na-H exchangers NHE1, NHE3, and NHE5 as well as the Na+- coupled HCO3− transporters NBCe1, NBCn1, NDCBE, and NBCn2). (4) The effect of acid-base disturbances on neuronal function and the roles of acid-base transporters in defending neuronal pHi under physiopathologic conditions. PMID:24592239

  4. Reconstitution of bile acid transport in the rat hepatoma McArdle RH-7777 cell line.

    PubMed

    Torchia, E C; Shapiro, R J; Agellon, L B

    1996-07-01

    The liver recovers bile acids from the portal circulation primarily via an active process that is dependent on sodium ions. Hepatocytes lose the ability to transport bile acids in culture, and, in liver-derived permanent cell lines, this ability is severely reduced or absent. To study the importance of bile acids in regulating liver-specific functions (e.g., cellular bile acid and cholesterol metabolism), we have re-established active bile acid transport in cultured cells. The complementary DNA (cDNA) encoding the rat sodium/taurocholate cotransporting polypeptide (ntcp) was placed under the control of a cytomegalovirus promoter and transfected into the rat hepatoma cell line, McArdle RH-7777. Transfected cells were screened for the ability to take up [3H]-taurocholate. Clones that displayed the ability to take up taurocholate were expanded (designated McNtcp) and further characterized. The apparent Michaelis constant (Km) for taurocholate uptake was similar among the different clones. The observed maximum velocity (Vmax), however, differed and was positively correlated with the abundance of recombinant ntcp messenger RNA (mRNA). The highest level of taurocholate uptake activity observed in McNtcp cells was comparable with that of freshly isolated hepatocytes. Efflux of accumulated taurocholate from McNtcp cells proceeded in a manner similar to primary hepatocytes, indicating that McArdle RH-7777 cells have retained the ability to secrete bile acids. Moreover, taurocholate uptake in McNtcp cells was inhibited by other bile acid species. Based on the observed kinetic parameters, the reconstituted McArdle RH-7777 cells mimic the ability of primary hepatocytes to transport bile acids.

  5. Dietary regulation of intestinal brush-border sugar and amino acid transport in carnivores.

    PubMed

    Buddington, R K; Chen, J W; Diamond, J M

    1991-10-01

    The ability of omnivores and herbivores to regulate reversibly their intestinal brush-border nutrient transporters is functionally related to the unpredictably variable composition of their natural diets. To determine whether carnivores are able similarly to regulate the activities of their intestinal nutrient transporters, we fed to three species of vertebrates that are carnivorous as adults (cats, mink, and leopard frogs) diets with either at least 50% digestible carbohydrate or with negligible carbohydrate levels. Rates of transport for the sugars glucose and fructose and the amino acids (AAs) aspartate, leucine, lysine, and proline were measured throughout the intestine (only proline and glucose in the frogs) by an in vitro everted-sleeve method. Although all three species consume much carbohydrate during early development, only the mink was able to regulate sugar transporter activity in response to changes in levels of dietary carbohydrate. In contrast, the sugar transporters of the cat were unresponsive to varying carbohydrate levels, and long-term feeding of a high-carbohydrate diet caused down-regulation of sugar transport in frogs. Of the three species, only the mink is a member of a family that includes omnivorous species, whereas all members of the families to which the cat and frog belong are carnivorous as adults. All three species were able to regulate rates of AA transport, though the patterns and magnitude of the responses differed between species as well as between AAs, suggesting independent regulation of some AA transporters.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Mutation and gene transfer of neutral amino acid transport System L genes in mammalian cells

    SciTech Connect

    El-Gewely, M.R.; Collarini, E.J.; Campbell, G.S.; Oxender, D.L.

    1987-05-01

    The authors are attempting to clone the genes coding for amino acid transport System L. Chinese hamster ovary (CHO) cell mutants that are temperature sensitive in their leucyl-tRNA synthetase show temperature-dependent regulation of System L. Temperature resistant mutants isolated from these cells have constitutively derepressed System L activity. Somatic cell fusion studies using these mutants have suggested that a trans-acting element controls regulation of System L. Mutants with reduced transport activity were isolated by a TH-suicide selection. The growth of these mutant cells is limited by the transport defect. CHO mutants were transformed with a human cosmid library, followed by selection at high temperatures and low leucine concentrations. Some transformants have increased levels of System L activity, suggesting that human genes coding for leucine transport have been incorporated into the CHO genome. Human sequences were rescued by a lambda in vitro packaging system. These sequences hybridize to vector and total human DNA. Experiments are being done to confirm that these sequences indeed code for transport System L. They are also attempting to label membrane components of amino acid transporters by group-specific modifying reagents.

  7. Glucocorticoid regulation of amino acid transport in anucleate rat hepatoma (HTC) cells

    PubMed Central

    1981-01-01

    The transport of alpha-aminoisobutyric acid (AIB) by rat hepatoma tissue culture (HTC) cells is rapidly and reversibly inhibited by dexamethasone and other glucocorticoids. To investigate the role of the nucleus in the regulation of transport and to determine whether steroid hormones or steroid-receptor complexes may have direct effects on cytoplasmic or membrane functions, we have examined the regulation of transport by dexamethasone in anucleate HTC cells. Cytoplasts prepared from suspension cultures of HTC cells fully retain active transport of AIB with the same kinetic properties as intact cells. However, the uptake of AIB is not inhibited by dexamethasone or other corticosteroids. Neither is the inhibited rate of transport, manifested by cytoplasts prepared from dexamethasone-treated cells, restored to normal upon removal of the hormone. Anucleate cells exhibit specific, saturable binding of [3H]dexamethasone; however, the binding is reduced compared with that of intact cells. The nucleus is thus required for the glucocorticoid regulation of amino acid transport in HTC cells. PMID:7217203

  8. Adaptive transport of folic acid across renal epithelia in folate-deficient rats.

    PubMed

    Wani, Nissar Ahmad; Kaur, Jyotdeep

    2012-11-01

    Folate (vitamin B(9)) is an essential vitamin for a wide spectrum of biochemical reactions; however, unlike bacteria and plants, mammals are devoid of folate biosynthesis and thus must obtain this cofactor from exogenous sources. The activities of folate transporters on the kidneys play an important role in conserving folate excretion and reabsorption across the apical membrane of the renal proximal tubules. The different transport system activities may become identifiable in response to external stimuli, such as folate availability and exposure to chemotherapeutic agents. We have explored the effect of folate deficiency on the activity and expression of folate transporters in rat kidneys. Wistar rats were fed a folate-containing diet (2 mg folic acid kg(-1) diet) or a folic acid-free diet over a 3-month period, and mechanisms of folate transport were studied in renal brush border membrane vesicles and basolateral membrane vesicles. The renal folate uptake process is saturable and pH dependent, and it involves the folate receptor and reduced folate carrier (RFC) systems and possibly the proton coupled folate transporter (PCFT) system. We found that folate deficiency increased the renal brush border membrane and basolateral folate uptake by increasing the number of transporter molecules. The observed up-regulation of mRNA expression was also associated with a significant increase in RFC and PCFT expression at the protein level.

  9. Modulating Effect of Ascorbic Acid on Transport-Induced Immunosuppression in Goats

    PubMed Central

    Minka, Ndazo Salka; Ayo, Joseph Olusegun

    2011-01-01

    The effect of 12 h road transportation on some basic blood cells and the modulating role of ascorbic acid were investigated in 40 adult Red Sokoto goats during the hot dry season. The animals were divided into two groups, GI (experimental; n = 20) and GII (control; n = 20). Group 1 was administered with ascorbic acid (AA) per os at a dosage rate of 100 mg/kg body weight, while GII was given 10 mL of sterile water per goat. Forty minutes after the administration and loading, the goats were transported for 12 h. The result obtained in GII goats showed that loading, transportation, high ambient temperature (AT), and relative humidity (RH) encountered during transportation induced lymphopenia, neutrophilia, and eosinopenia, which can cause immunosuppression. In GI goats, the administration of AA prior to loading and transportation ameliorated the adverse effects of loading and transportation stress on neutrophil/lymphocyte ratio and eosinopenia of the goats. PMID:23738106

  10. Role of sodium ion in transport of folic acid in the small intestine

    SciTech Connect

    Zimmerman, J.; Selhub, J.; Rosenberg, I.H.

    1986-08-01

    The effect of sodium on folate transport across the intestinal luminal membrane was analyzed using two techniques: the influx chamber and isoalted brush-border membrane vesicles. Preincubation of tissue in Na -free medium did not have a consistent effect on folic acid influx provided that Na was present in the test solution. Replacement of Na in the test solution by choline resulted in a significant reduction of folic acid influx. However, when intestinal sheets that had been equilibrated in Na -free solution were exposed to test solutions containing either Na , Li , K , Rb , Cs , Tris , or guanidinium as main cations, folic acid influx was not significantly decreased. Concentration-dependence studies showed that replacement of Na by Rb did not affect the saturable mechanism of folate transport. Rather, a decrease in nonsaturable folic acid uptake accounted for the slightly reduced influx observed in the presence of Rb . Experiments with brush-border membrane vesicles revealed that methotrexate uptake was significantly higher in the presence of external Na than in the presence of K , but was not different from uptake in the presence of K plus valinomycin. These data suggest that 1) the saturable component of folate transport is not Na dependent, and 2) nonsaturable transport of folic acid across the luminal membrane occurs in part through a conductive pathway that involves a negatively charged species of folate and a cation whose membrane permeability affects the rate of folate transport. The importance of Na in this process in vivo derives from the fact that Na is the most permeant cation available at the absorptive site in the small intestine.

  11. Inhibition of ileal bile acid transporter: An emerging therapeutic strategy for chronic idiopathic constipation

    PubMed Central

    Mosińska, Paula; Fichna, Jakub; Storr, Martin

    2015-01-01

    Chronic idiopathic constipation is a common disorder of the gastrointestinal tract that encompasses a wide profile of symptoms. Current treatment options for chronic idiopathic constipation are of limited value; therefore, a novel strategy is necessary with an increased effectiveness and safety. Recently, the inhibition of the ileal bile acid transporter has become a promising target for constipation-associated diseases. Enhanced delivery of bile acids into the colon achieves an accelerated colonic transit, increased stool frequency, and relief of constipation-related symptoms. This article provides insight into the mechanism of action of ileal bile acid transporter inhibitors and discusses their potential clinical use for pharmacotherapy of constipation in chronic idiopathic constipation. PMID:26139989

  12. Inhibition of ileal bile acid transporter: An emerging therapeutic strategy for chronic idiopathic constipation.

    PubMed

    Mosińska, Paula; Fichna, Jakub; Storr, Martin

    2015-06-28

    Chronic idiopathic constipation is a common disorder of the gastrointestinal tract that encompasses a wide profile of symptoms. Current treatment options for chronic idiopathic constipation are of limited value; therefore, a novel strategy is necessary with an increased effectiveness and safety. Recently, the inhibition of the ileal bile acid transporter has become a promising target for constipation-associated diseases. Enhanced delivery of bile acids into the colon achieves an accelerated colonic transit, increased stool frequency, and relief of constipation-related symptoms. This article provides insight into the mechanism of action of ileal bile acid transporter inhibitors and discusses their potential clinical use for pharmacotherapy of constipation in chronic idiopathic constipation. PMID:26139989

  13. ΔpH-Dependent Amino Acid Transport into Plasma Membrane Vesicles Isolated from Sugar Beet (Beta vulgaris L.) Leaves

    PubMed Central

    Li, Zhen-Chang; Bush, Daniel R.

    1991-01-01

    Proton-coupled aliphatic, neutral amino acid transport was investigated in plasma membrane vesicles isolated from sugar beet (Beta vulgaris L., cv Great Western) leaves. Two neutral amino acid symport systems were resolved based on inter-amino acid transport competition and on large variations in the specific activity of each porter in different species. Competitive inhibition was observed for transport competition between alanine, methionine, glutamine, and leucine (the alanine group) and between isoleucine, valine, and threonine (the isoleucine group). The apparent Km and Ki values were similar for transport competition among amino acids within the alanine group. In contrast, the kinetics of transport competition between these two groups of amino acids did not fit a simple competitive model. Furthermore, members of the isoleucine group were weak transport antagonists of the alanine group. These results are consistent with two independent neutral amino acid porters. In support of that conclusion, the ratio of the specific activity of alanine transport versus isoleucine transport varied from two- to 13-fold in plasma membrane vesicles isolated from different plant species. This ratio would be expected to remain relatively stable if these amino acids were moving through a single transport system and, indeed, the ratio of alanine to glutamine transport varied less than twofold. Analysis of the predicted structure of the aliphatic, neutral amino acids in solution shows that isoleucine, valine, and threonine contain a branched methyl or hydroxyl group at the β-carbon position that places a dense electron cloud close to the α-amino group. This does not occur for the unbranched amino acids or those that branch further away, e.g. leucine. We hypothesize that this structural feature of isoleucine, valine, and threonine results in unfavorable steric interactions with the alanine transport system that limits their flux through this porter. Hydrophobicity and hydrated

  14. Effect of maternal micronutrients (folic acid, vitamin B12) and omega 3 fatty acids on liver fatty acid desaturases and transport proteins in Wistar rats.

    PubMed

    Wadhwani, Nisha S; Manglekar, Rupali R; Dangat, Kamini D; Kulkarni, Asmita V; Joshi, Sadhana R

    2012-01-01

    A disturbed fatty acid metabolism increases the risk of adult non-communicable diseases. This study examines the effect of maternal micronutrients on the fatty acid composition, desaturase activity, mRNA levels of fatty acid desaturases and transport proteins in the liver. Pregnant female rats were divided into 6 groups at 2 levels of folic acid both in the presence and absence of vitamin B(12). The vitamin B(12) deficient groups were supplemented with omega 3 fatty acid. An imbalance of maternal micronutrients reduces liver docosahexaenoic acid, increases Δ5 desaturase activity but decreases mRNA levels, decreases Δ6 desaturase activity but not mRNA levels as compared to control. mRNA level of Δ5 desaturase reverts back to the levels of the control group as a result of omega 3 fatty acid supplementation. Our data for the first time indicates that maternal micronutrients differentially alter the activity and expression of fatty acid desaturases in the liver.

  15. Transport of indoleacetic acid in intact corn coleoptiles. [Zea mays L

    SciTech Connect

    Parker, K.E.; Briggs, W.R. )

    1990-10-01

    We have characterized the transport of ({sup 3}H)indoleacetic acid (IAA) in intact corn (Zea mays L.) coleoptiles. We have used a wide range of concentrations of added IAA (28 femtomoles to 100 picomoles taken up over 60 minutes). The shape of the transport curve varies with the concentration of added IAA, although the rate of movement of the observed front of tracer is invariant with concentration. At the lowest concentration of tracer used, the labeled IAA in the transport stream is not detectably metabolized or immobilized, curvature does not develop as a result of tracer application, and normal phototropic and gravitropic responsiveness are not affected. Therefore we believe we are observing the transport of true tracer quantities of labeled auxin at this lowest concentration.

  16. Bile acid transporters and regulatory nuclear receptors in the liver and beyond

    PubMed Central

    Halilbasic, Emina; Claudel, Thierry; Trauner, Michael

    2013-01-01

    Summary Bile acid (BA) transporters are critical for maintenance of the enterohepatic BA circulation where BAs exert their multiple physiological functions including stimulation of bile flow, intestinal absorption of lipophilic nutrients, solubilization and excretion of cholesterol, as well as antimicrobial and metabolic effects. Tight regulation of BA transporters via nuclear receptors is necessary to maintain proper BA homeostasis. Hereditary and acquired defects of BA transporters are involved in the pathogenesis of several hepatobiliary disorders including cholestasis, gallstones, fatty liver disease and liver cancer, but also play a role in intestinal and metabolic disorders beyond the liver. Thus, pharmacological modification of BA transporters and their regulatory nuclear receptors opens novel treatment strategies for a wide range of disorders. PMID:22885388

  17. Identification of functional amino acid residues involved in polyamine and agmatine transport by human organic cation transporter 2.

    PubMed

    Higashi, Kyohei; Imamura, Masataka; Fudo, Satoshi; Uemura, Takeshi; Saiki, Ryotaro; Hoshino, Tyuji; Toida, Toshihiko; Kashiwagi, Keiko; Igarashi, Kazuei

    2014-01-01

    Polyamine (putrescine, spermidine and spermine) and agmatine uptake by the human organic cation transporter 2 (hOCT2) was studied using HEK293 cells transfected with pCMV6-XL4/hOCT2. The Km values for putrescine and spermidine were 7.50 and 6.76 mM, and the Vmax values were 4.71 and 2.34 nmol/min/mg protein, respectively. Spermine uptake by hOCT2 was not observed at pH 7.4, although it inhibited both putrescine and spermidine uptake. Agmatine was also taken up by hOCT2, with Km value: 3.27 mM and a Vmax value of 3.14 nmol/min/mg protein. Amino acid residues involved in putrescine, agmatine and spermidine uptake by hOCT2 were Asp427, Glu448, Glu456, Asp475, and Glu516. In addition, Glu524 and Glu530 were involved in putrescine and spermidine uptake activity, and Glu528 and Glu540 were weakly involved in putrescine uptake activity. Furthermore, Asp551 was also involved in the recognition of spermidine. These results indicate that the recognition sites for putrescine, agmatine and spermidine on hOCT2 strongly overlap, consistent with the observation that the three amines are transported with similar affinity and velocity. A model of spermidine binding to hOCT2 was constructed based on the functional amino acid residues.

  18. Experimental Study and Reactive Transport Modeling of Boric Acid Leaching of Concrete

    NASA Astrophysics Data System (ADS)

    Pabalan, R. T.; Chiang, K.-T. K.

    2013-07-01

    Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure, compromise the integrity of the structure, or cause unmonitored releases of contaminated water to the environment. Experimental data indicate that pH is a critical parameter that determines the corrosion susceptibility of rebar in borated water and the degree of concrete degradation by boric acid leaching. In this study, reactive transport modeling of concrete leaching by borated water was performed to provide information on the solution pH in the concrete crack or matrix and the degree of concrete degradation at different locations of an SFP concrete structure exposed to borated water. Simulations up to 100 years were performed using different boric acid concentrations, crack apertures, and solution flow rates. Concrete cylinders were immersed in boric acid solutions for several months and the mineralogical changes and boric acid penetration in the concrete cylinder were evaluated as a function of time. The depths of concrete leaching by boric acid solution derived from the reactive transport simulations were compared with the measured boric acid penetration depth.

  19. Channel-mediated lactic acid transport: a novel function for aquaglyceroporins in bacteria.

    PubMed

    Bienert, Gerd P; Desguin, Benoît; Chaumont, François; Hols, Pascal

    2013-09-15

    MIPs (major intrinsic proteins), also known as aquaporins, are membrane proteins that channel water and/or uncharged solutes across membranes in all kingdoms of life. Considering the enormous number of different bacteria on earth, functional information on bacterial MIPs is scarce. In the present study, six MIPs [glpF1 (glycerol facilitator 1)-glpF6] were identified in the genome of the Gram-positive lactic acid bacterium Lactobacillus plantarum. Heterologous expression in Xenopus laevis oocytes revealed that GlpF2, GlpF3 and GlpF4 each facilitated the transmembrane diffusion of water, dihydroxyacetone and glycerol. As several lactic acid bacteria have GlpFs in their lactate racemization operon (GlpF1/F4 phylogenetic group), their ability to transport this organic acid was tested. Both GlpF1 and GlpF4 facilitated the diffusion of D/L-lactic acid. Deletion of glpF1 and/or glpF4 in Lb. plantarum showed that both genes were involved in the racemization of lactic acid and, in addition, the double glpF1 glpF4 mutant showed a growth delay under conditions of mild lactic acid stress. This provides further evidence that GlpFs contribute to lactic acid metabolism in this species. This lactic acid transport capacity was shown to be conserved in the GlpF1/F4 group of Lactobacillales. In conclusion, we have functionally analysed the largest set of bacterial MIPs and demonstrated that the lactic acid membrane permeability of bacteria can be regulated by aquaglyceroporins.

  20. Effects of chemical oxidants on perfluoroalkyl acid transport in one-dimensional porous media columns.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2015-02-01

    In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors. PMID:25621878

  1. Effects of chemical oxidants on perfluoroalkyl acid transport in one-dimensional porous media columns.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2015-02-01

    In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors.

  2. Rapid downward transport of the neurotoxin domoic acid in coastal waters

    NASA Astrophysics Data System (ADS)

    Sekula-Wood, Emily; Schnetzer, Astrid; Benitez-Nelson, Claudia R.; Anderson, Clarissa; Berelson, William M.; Brzezinski, Mark A.; Burns, Justina M.; Caron, David A.; Cetinic, Ivona; Ferry, John L.; Fitzpatrick, Elizabeth; Jones, Burton H.; Miller, Peter E.; Morton, Steve L.; Schaffner, Rebecca A.; Siegel, David A.; Thunell, Robert

    2009-04-01

    Toxic phytoplankton blooms threaten coastlines worldwide by diminishing beach quality and adversely affecting marine ecosystems and human health. The common diatom genus Pseudo-nitzschia consists of several species known to produce the neurotoxin domoic acid. Recent studies suggest that algal blooms dominated by Pseudo-nitzschia are increasing in frequency and duration owing to changes in coastal nutrient regimes. However, few studies have examined the persistence or long-term biogeochemical cycling of domoic acid in marine waters. Here, we measure the concentration of domoic acid in surface waters and sediment traps-up to 800m in depth-off the coast of Southern California. We show that peaks in Pseudo-nitzschia abundance and domoic acid concentrations in surface waters coincide with peaks in diatom and toxin abundance at depth, suggesting rapid downward transport of the toxin. In some cases, the sinking particles contain over five times the United States federal limit of domoic acid. Detection of domoic acid in bottom sediments indicates that the toxin may persist long after the Pseudo-nitzschia blooms. Our results indicate that vertical fluxes of domoic acid are a substantial source of the toxin to deep-ocean food webs, and could explain high levels of domoic acid previously observed in benthic organisms.

  3. Mammalian target of rapamycin signalling modulates amino acid uptake by regulating transporter cell surface abundance in primary human trophoblast cells.

    PubMed

    Rosario, Fredrick J; Kanai, Yoshikatsu; Powell, Theresa L; Jansson, Thomas

    2013-02-01

    Abnormal fetal growth increases the risk for perinatal complications and predisposes for the development of obesity, diabetes and cardiovascular disease later in life. Emerging evidence suggests that changes in placental amino acid transport directly contribute to altered fetal growth. However, the molecular mechanisms regulating placental amino acid transport are largely unknown. Here we combined small interfering (si) RNA-mediated silencing approaches with protein expression/localization and functional studies in cultured primary human trophoblast cells to test the hypothesis that mammalian target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) regulate amino acid transporters by post-translational mechanisms. Silencing raptor (inhibits mTORC1) or rictor (inhibits mTORC2) markedly decreased basal System A and System L amino acid transport activity but had no effect on growth factor-stimulated amino acid uptake. Simultaneous inhibition of mTORC1 and 2 completely inhibited both basal and growth factor-stimulated amino acid transport activity. In contrast, mTOR inhibition had no effect on serotonin transport. mTORC1 or mTORC2 silencing markedly decreased the plasma membrane expression of specific System A (SNAT2, SLC38A2) and System L (LAT1, SLC7A5) transporter isoforms without affecting global protein expression. In conclusion, mTORC1 and mTORC2 regulate human trophoblast amino acid transporters by modulating the cell surface abundance of specific transporter isoforms. This is the first report showing regulation of amino acid transport by mTORC2. Because placental mTOR activity and amino acid transport are decreased in human intrauterine growth restriction our data are consistent with the possibility that dysregulation of placental mTOR plays an important role in the development of abnormal fetal growth.

  4. Human intestine luminal ACE2 and amino acid transporter expression increased by ACE-inhibitors.

    PubMed

    Vuille-dit-Bille, Raphael N; Camargo, Simone M; Emmenegger, Luca; Sasse, Tom; Kummer, Eva; Jando, Julia; Hamie, Qeumars M; Meier, Chantal F; Hunziker, Schirin; Forras-Kaufmann, Zsofia; Kuyumcu, Sena; Fox, Mark; Schwizer, Werner; Fried, Michael; Lindenmeyer, Maja; Götze, Oliver; Verrey, François

    2015-04-01

    Sodium-dependent neutral amino acid transporter B(0)AT1 (SLC6A19) and imino acid (proline) transporter SIT1 (SLC6A20) are expressed at the luminal membrane of small intestine enterocytes and proximal tubule kidney cells where they exert key functions for amino acid (re)absorption as documented by their role in Hartnup disorder and iminoglycinuria, respectively. Expression of B(0)AT1 was shown in rodent intestine to depend on the presence of the carboxypeptidase angiotensin-converting enzyme 2 (ACE2). This enzyme belongs to the renin-angiotensin system and its expression is induced by treatment with ACE-inhibitors (ACEIs) or angiotensin II AT1 receptor blockers (ARBs) in many rodent tissues. We show here in the Xenopus laevis oocyte expression system that human ACE2 also functionally interacts with SIT1. To investigate in human intestine the potential effect of ACEIs or ARBs on ACE2, we analysed intestinal biopsies taken during routine gastroduodenoscopy and ileocolonoscopy from 46 patients of which 9 were under ACEI and 13 ARB treatment. Analysis of transcript expression by real-time PCR and of proteins by immunofluorescence showed a co-localization of SIT1 and B(0)AT1 with ACE2 in the brush-border membrane of human small intestine enterocytes and a distinct axial expression pattern of the tested gene products along the intestine. Patients treated with ACEIs displayed in comparison with untreated controls increased intestinal mRNA levels of ACE2, peptide transporter PEPT1 (SLC15A1) and AA transporters B(0)AT1 and PAT1 (SLC36A1). This study unravels in human intestine the localization and distribution of intestinal transporters involved in amino acid absorption and suggests that ACEIs impact on their expression.

  5. Structural basis for amino acid export by DMT superfamily transporter YddG.

    PubMed

    Tsuchiya, Hirotoshi; Doki, Shintaro; Takemoto, Mizuki; Ikuta, Tatsuya; Higuchi, Takashi; Fukui, Keita; Usuda, Yoshihiro; Tabuchi, Eri; Nagatoishi, Satoru; Tsumoto, Kouhei; Nishizawa, Tomohiro; Ito, Koichi; Dohmae, Naoshi; Ishitani, Ryuichiro; Nureki, Osamu

    2016-05-30

    The drug/metabolite transporter (DMT) superfamily is a large group of membrane transporters ubiquitously found in eukaryotes, bacteria and archaea, and includes exporters for a remarkably wide range of substrates, such as toxic compounds and metabolites. YddG is a bacterial DMT protein that expels aromatic amino acids and exogenous toxic compounds, thereby contributing to cellular homeostasis. Here we present structural and functional analyses of YddG. Using liposome-based analyses, we show that Escherichia coli and Starkeya novella YddG export various amino acids. The crystal structure of S. novella YddG at 2.4 Å resolution reveals a new membrane transporter topology, with ten transmembrane segments in an outward-facing state. The overall structure is basket-shaped, with a large substrate-binding cavity at the centre of the molecule, and is composed of inverted structural repeats related by two-fold pseudo-symmetry. On the basis of this intramolecular symmetry, we propose a structural model for the inward-facing state and a mechanism of the conformational change for substrate transport, which we confirmed by biochemical analyses. These findings provide a structural basis for the mechanism of transport of DMT superfamily proteins.

  6. Structural basis for amino acid export by DMT superfamily transporter YddG.

    PubMed

    Tsuchiya, Hirotoshi; Doki, Shintaro; Takemoto, Mizuki; Ikuta, Tatsuya; Higuchi, Takashi; Fukui, Keita; Usuda, Yoshihiro; Tabuchi, Eri; Nagatoishi, Satoru; Tsumoto, Kouhei; Nishizawa, Tomohiro; Ito, Koichi; Dohmae, Naoshi; Ishitani, Ryuichiro; Nureki, Osamu

    2016-06-16

    The drug/metabolite transporter (DMT) superfamily is a large group of membrane transporters ubiquitously found in eukaryotes, bacteria and archaea, and includes exporters for a remarkably wide range of substrates, such as toxic compounds and metabolites. YddG is a bacterial DMT protein that expels aromatic amino acids and exogenous toxic compounds, thereby contributing to cellular homeostasis. Here we present structural and functional analyses of YddG. Using liposome-based analyses, we show that Escherichia coli and Starkeya novella YddG export various amino acids. The crystal structure of S. novella YddG at 2.4 Å resolution reveals a new membrane transporter topology, with ten transmembrane segments in an outward-facing state. The overall structure is basket-shaped, with a large substrate-binding cavity at the centre of the molecule, and is composed of inverted structural repeats related by two-fold pseudo-symmetry. On the basis of this intramolecular symmetry, we propose a structural model for the inward-facing state and a mechanism of the conformational change for substrate transport, which we confirmed by biochemical analyses. These findings provide a structural basis for the mechanism of transport of DMT superfamily proteins. PMID:27281193

  7. Osmotic regulation of bile acid transport, apoptosis and proliferation in rat liver.

    PubMed

    Häussinger, Dieter; Reinehr, Roland

    2011-01-01

    Changes in mammalian cell volume as induced by either anisoosmolarity, hormones, nutrients or oxidative stress critically contribute to the regulation of metabolism, membrane transport, gene expression and the susceptibility to cellular stress. Osmosensing, i.e. the registration of cell volume changes, triggers signal transduction pathways towards effector pathways (osmosignaling) which link alterations of cell volume to changes in cell function. This review summarizes our own work on the understanding of how osmosensing and osmosignaling integrate into the overall context of bile acid transport, growth factor signaling and the execution of apoptotic programs. PMID:22178998

  8. Physiological responses of erythrocytes of goats to transportation and the mondulatory role of ascorbic acid.

    PubMed

    Minka, Ndazo Salka; Ayo, Joseph Olusegun

    2010-07-01

    Experiments were performed with the aim of investigating the effect of road transportation for 12 hr on erythrocytes of goats during the hot-dry season and the modulatory role of ascorbic acid. Forty 2.5-3-year-old Red Sokoto goats weighing 23-25 kg and belonging to both sexes served as the subjects of the study. Twenty of the goats served as the experimental group and were administered ascorbic acid (AA) per os at a dosage rate of 100 mg/kg body weight; the other 20 served as controls and were given 10 ml each of sterile water. Forty minutes after the administration and loading, the goats were transported for 12 hr. EDTA blood samples collected before loading, after loading, immediately after transportation and subsequently on the 3rd and 7th days of post-transportation were used to determine the red blood cell (RBC) count, packed cell volume (PCV), hemoglobin (Hb), erythrocyte osmotic fragility (EOF), hematimetric (intrinsic) indices and hemoglobin index levels. The obtained results showed that handling, loading and transportation of the control goats induced significant (P<0.05) increases in RBC, Hb, EOF and hypochromic erythrocytes and a decrease (P<0.05) in the volume and average Hb content in RBCs. AA administration ameliorated all these changes. The present results suggest that road transportation for 12 hr during the hot-dry season could induce serious stress, resulting in hemolysis of erythrocytes, which was ameliorated by AA administration. In addition, the results demonstrated that EOF could be used as a diagnostic tool in road transportation stress.

  9. Migration-induced variation of fatty acid transporters and cellular metabolic intensity in passerine birds.

    PubMed

    Zhang, Yufeng; King, Marisa O; Harmon, Erin; Eyster, Kathleen; Swanson, David L

    2015-10-01

    Because lipids are the main fuel supporting avian endurance activity, lipid transport and oxidation capacities may increase during migration. We measured enzyme activities, mRNA expression and protein levels in pectoralis and heart for several key steps of lipid transport and catabolism pathways to investigate whether these pathways were upregulated during migration. We used yellow-rumped (Setophaga coronata) and yellow (S. petechia) warblers and warbling vireos (Vireo gilvus) as study species because they all show migration-induced increases in organismal metabolic capacities. For yellow-rumped warblers, β-hydroxyacyl CoA-dehydrogenase (HOAD) activities and fatty acid transporter mRNA and/or protein levels were higher during spring than fall in pectoralis and heart, except that fatty acid translocase (FAT/CD36) protein levels showed the opposite pattern in heart. Lipid transporter protein levels, but not mRNA expression, in pectoralis and heart of warbling vireos were higher either during spring or fall than summer, but this was not true for HOAD activities. For yellow warblers, pectoralis, but not heart, protein levels of lipid transporters were upregulated during migration relative to summer, but this pattern was not evident for mRNA expression or HOAD activity. Finally, muscle and heart citrate synthase and carnitine palmitoyl transferase activities showed little seasonal variation for any species. These data suggest that pectoralis and heart lipid transport and catabolism capacities are often, but not universally, important correlates of elevated organismal metabolic capacity during migration. In contrast, migration-induced variation in cellular metabolic intensity and mitochondrial membrane transport are apparently not common correlates of the migratory phenotype in passerines.

  10. Migration-induced variation of fatty acid transporters and cellular metabolic intensity in passerine birds.

    PubMed

    Zhang, Yufeng; King, Marisa O; Harmon, Erin; Eyster, Kathleen; Swanson, David L

    2015-10-01

    Because lipids are the main fuel supporting avian endurance activity, lipid transport and oxidation capacities may increase during migration. We measured enzyme activities, mRNA expression and protein levels in pectoralis and heart for several key steps of lipid transport and catabolism pathways to investigate whether these pathways were upregulated during migration. We used yellow-rumped (Setophaga coronata) and yellow (S. petechia) warblers and warbling vireos (Vireo gilvus) as study species because they all show migration-induced increases in organismal metabolic capacities. For yellow-rumped warblers, β-hydroxyacyl CoA-dehydrogenase (HOAD) activities and fatty acid transporter mRNA and/or protein levels were higher during spring than fall in pectoralis and heart, except that fatty acid translocase (FAT/CD36) protein levels showed the opposite pattern in heart. Lipid transporter protein levels, but not mRNA expression, in pectoralis and heart of warbling vireos were higher either during spring or fall than summer, but this was not true for HOAD activities. For yellow warblers, pectoralis, but not heart, protein levels of lipid transporters were upregulated during migration relative to summer, but this pattern was not evident for mRNA expression or HOAD activity. Finally, muscle and heart citrate synthase and carnitine palmitoyl transferase activities showed little seasonal variation for any species. These data suggest that pectoralis and heart lipid transport and catabolism capacities are often, but not universally, important correlates of elevated organismal metabolic capacity during migration. In contrast, migration-induced variation in cellular metabolic intensity and mitochondrial membrane transport are apparently not common correlates of the migratory phenotype in passerines. PMID:26194862

  11. Inhibitory effect of unconjugated bile acids on the intestinal transport of 5-methyltetrahydrofolate in rat jejunum in vitro.

    PubMed Central

    Said, H M; Hollander, D; Strum, W B

    1984-01-01

    The effect of the unconjugated bile acids, cholic, deoxycholic, chenodeoxycholic, and ursodeoxycholic acids, and of the conjugated bile acid taurocholic acid on the mucosal-to-serosal transport and tissue uptake of the naturally occurring folate derivative, 5-methyltetrahydrofolate (5-CH3H4PteGlu) was examined in everted sacs of rat jejunum. Each of the unconjugated bile acids examined inhibited the transport and tissue uptake of 5-CH3H4PteGlu in a concentration dependent manner. At low concentrations (0.01-0.1 mM) of cholic and deoxycholic acids, no structural or functional damage to the intestinal mucosa occurred and the transport of 5-CH3H4PteGlu was inhibited competitively with Ki values of 0.114 mM and 0.055 mM for cholic and deoxycholic acids, respectively. The greater inhibition of 5-CH3H4PteGlu transport by unconjugated bile acids at 1 mM can be attributed to observed structural and functional damage to the intestinal mucosa. The addition of 2 mM lecithin to the mucosal medium failed to prevent the inhibitory effect of 0.1 mM deoxycholic acid on the transport of 0.5 microM 5-CH3H4PteGlu. Compared with the effect of unconjugated bile acids, the conjugated bile acid taurocholic acid (0.01-5 mM) showed no effect on the transport and tissue uptake of 5-CH3H4PteGlu. The results of this study show that intestinal transport and tissue uptake of 5-CH3H4PteGlu are inhibited by unconjugated bile acids in a dose-dependent fashion. The clinical and physiological implications of these observations are discussed. PMID:6510770

  12. Insulin-induced phospho-oligosaccharide stimulates amino acid transport in isolated rat hepatocytes.

    PubMed Central

    Varela, I; Avila, M; Mato, J M; Hue, L

    1990-01-01

    The ability of the insulin-induced phospho-oligosaccharide to stimulate amino acid transport was studied in isolated rat hepatocytes. At low alpha-aminoisobutyric acid concentrations (0.1 mM), both 100 nM-insulin and 10 microM-phospho-oligosaccharide doubled amino acid uptake after 2 h of incubation. This stimulation was prevented by 0.1 mM-cycloheximide or 5 micrograms of actinomycin D/ml, indicating that the phospho-oligosaccharide, like insulin, was acting via the synthesis of a high-affinity transport component. The effects of the phospho-oligosaccharide and of insulin were blocked by Ins2P (2.5 mM), but not by myo-inositol, inositol hexaphosphoric acid or several monosaccharides such as mannose, glucosamine and galactose. Both the temporal effect on amino acid entry and the extent of stimulation of this process by the phospho-oligosaccharide indicate that this molecule mimics, and may mediate, some of the long-term actions of insulin. However, the effects of phospho-oligosaccharide and insulin were not exactly the same, since the effect of insulin, but not of the phospho-oligosaccharide, was additive with that of glucagon. PMID:2185744

  13. Polar transport and accumulation of indole-3-acetic acid during root regeneration by Pinus lambertiana embryos.

    PubMed

    Greenwood, M S; Goldsmith, M H

    1970-12-01

    The relation of indoleacetic acid (IAA) transport to accumulation of auxin at the base of cuttings and to polar root formation was investigated with small cuttings from germinating embryos of Pinus lambertiana.The transport of endogenous auxin participates in regeneration of roots. This is shown by the facts that (1) more than 40% of the cuttings rooted without addition of exogenous indoleacetic acid; (2) the first regeneration always occurred at the basal tip of a slanting cut; and (3) 2,3,5-triiodobenzoic acid (TIBA), a specific inhibitor of auxin transport, totally inhibited rooting. Addition of IAA to the medium increased the number of roots formed per rooting hypocotyl.Sections of hypocotyls excised from dormant embryos and tested immediately after 2 h hydration were capable of polar transport of IAA. This polarity increased during the first 3 days of culture because of a marked increase in basipetal transport. Culturing the cuttings in 1 μM IAA for 3-5 days doubled both the basipetal transport of 1-(14)C-IAA by hypocotyl segments and the accumulation of radioactivity at the base of cuttings.The extent of the accumulation at the base of cuttings was similar at early (2 days, first mitoses) and late stages (5 days, organized meristem) of regeneration and was not affected by removal of the regenerating region immediately prior to uptake and transport of (14)C-IAA. The accumulation was inhibited by TIBA. In terms of increase in wet and dry weight and mitotic activity, the cotyledons rather than the regenerating root meristems were the most actively growing region of the cuttings. The upper part of the hypocotyl elongated more than the region of the slanting cut where regeneration was occurring.These results provide no support for the idea that the regenerating root controls the direction of polar transport by acting as a sink. The results are consistent with the view that polar auxin transport delivers auxin to the base of the cutting and raises the local

  14. Identification of a lithium interaction site in the gamma-aminobutyric acid (GABA) transporter GAT-1.

    PubMed

    Zhou, Yonggang; Zomot, Elia; Kanner, Baruch I

    2006-08-01

    The sodium- and chloride-dependent electrogenic gamma-aminobutyric acid (GABA) transporter GAT-1, which transports two sodium ions together with GABA, is essential for synaptic transmission by this neurotransmitter. Although lithium by itself does not support GABA transport, it has been proposed that lithium can replace sodium at one of the binding sites but not at the other. To identify putative lithium selectivity determinants, we have mutated the five GAT-1 residues corresponding to those whose side chains participate in the sodium binding sites Na1 and Na2 of the bacterial leucine-transporting homologue LeuT(Aa). In GAT-1 and in most other neurotransmitter transporter family members, four of these residues are conserved, but aspartate 395 replaces the Na2 residue threonine 354. At varying extracellular sodium, lithium stimulated sodium-dependent transport currents as well as [3H]GABA uptake in wild type GAT-1. The extent of this stimulation was dependent on the GABA concentration. In mutants in which aspartate 395 was replaced by threonine or serine, the stimulation of transport by lithium was abolished. Moreover, these mutants were unable to mediate the lithium leak currents. This phenotype was not observed in mutants at the four other positions, although their transport properties were severely impacted. Thus at saturating GABA, the site corresponding to Na2 behaves as a low affinity sodium binding site where lithium can replace sodium. We propose that GABA participates in the other sodium binding site, just like leucine does in the Na1 site, and that at limiting GABA, this site determines the apparent sodium affinity of GABA transport.

  15. Effect of the defoliant thidiazuron on ethylene evolution from mung bean hypocotyl segments.

    PubMed

    Suttle, J C

    1984-08-01

    The effect of the defoliant thidiazuron (N-phenyl-N'1,2,3-thiadiazol-5-ylurea) on ethylene evolution from etiolated mung bean hypocotyl segments was examined. Treatment of hypocotyl segments with concentrations of thidiazuron equal to or greater than 30 nanomolar stimulated ethylene evolution. Increased rates of ethylene evolution from thidiazuron-treated tissues could be detected within 90 minutes of treatment and persisted up to 30 hours after treatment. Radioactive methionine was readily taken up by thidiazuron-treated tissues and was converted to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC) and an acidic conjugate of ACC. Aminoethoxyvinylglycine, aminooxyacetic acid, cobalt chloride, and alpha-aminoisobutyric acid reduced ethylene evolution from treated tissues. An increase in the endogenous content of free ACC coincided with the increase in ethylene evolution following thidiazuron treatment. Uptake and conversion of exogenous ACC to ethylene were not affected by thidiazuron treatment. No increases in the extractable activities of ACC synthase were detected following thidiazuron treatment.

  16. Inducible expression and pharmacology of the human excitatory amino acid transporter 2 subtype of L-glutamate transporter.

    PubMed

    Dunlop, J; Lou, Z; Zhang, Y; McIlvain, H B

    1999-12-01

    1. In this study we have examined the use of the ecdysone-inducible mammalian expression system (Invitrogen) for the regulation of expression of the predominant L-glutamate transporter EAAT2 (Excitatory Amino Acid Transporter) in HEK 293 cells. 2. HEK 293 cells which were stably transformed with the regulatory vector pVgRXR (EcR 293 cells) were used for transfection of the human EAAT2 cDNA using the inducible vector pIND and a clone designated HEK/EAAT2 was selected for further characterization. 3. Na+-dependent L-glutamate uptake activity (3.2 pmol min-1 mg-1) was observed in EcR 293 cells and this was increased approximately 2 fold in the uninduced HEK/EAAT2 cells, indicating a low level of basal EAAT2 activity in the absence of exogenous inducing agent. Exposure of HEK/EAAT2 cells to the ecdysone analogue Ponasterone A (10 microM for 24 h) resulted in a > or = 10 fold increase in the Na+-dependent activity. 4. L-glutamate uptake into induced HEK/EAAT2 cells followed first-order Michaelis-Menten kinetics and Eadie-Hofstee transformation of the saturable uptake data produced estimates of kinetic parameters as follows; Km 52.7+/-7.5 microM, Vmax 3.8+/-0.9 nmol min-1 mg-1 protein. 5. The pharmacological profile of the EAAT2 subtype was characterized using a series of L-glutamate transport inhibitors and the rank order of inhibitory potency was similar to that described previously for the rat homologue GLT-1 and in synaptosomal preparations from rat cortex. 6. Addition of the EAAT2 modulator arachidonic acid resulted in an enhancement (155+/-5% control in the presence of 30 microM) of the L-glutamate transport capacity in the induced HEK/EAAT2 cells. 7. This study demonstrates that the expression of EAAT2 can be regulated in a mammalian cell line using the ecdysone-inducible mammalian expression system.

  17. Inhibition of Na+-Taurocholate Co-transporting Polypeptide-mediated Bile Acid Transport by Cholestatic Sulfated Progesterone Metabolites*

    PubMed Central

    Abu-Hayyeh, Shadi; Martinez-Becerra, Pablo; Sheikh Abdul Kadir, Siti H.; Selden, Clare; Romero, Marta R.; Rees, Myrddin; Marschall, Hanns-Ulrich; Marin, Jose J. G.; Williamson, Catherine

    2010-01-01

    Sulfated progesterone metabolite (P4-S) levels are raised in normal pregnancy and elevated further in intrahepatic cholestasis of pregnancy (ICP), a bile acid-liver disorder of pregnancy. ICP can be complicated by preterm labor and intrauterine death. The impact of P4-S on bile acid uptake was studied using two experimental models of hepatic uptake of bile acids, namely cultured primary human hepatocytes (PHH) and Na+-taurocholate co-transporting polypeptide (NTCP)-expressing Xenopus laevis oocytes. Two P4-S compounds, allopregnanolone-sulfate (PM4-S) and epiallopregnanolone-sulfate (PM5-S), reduced [3H]taurocholate (TC) uptake in a dose-dependent manner in PHH, with both Na+-dependent and -independent bile acid uptake systems significantly inhibited. PM5-S-mediated inhibition of TC uptake could be reversed by increasing the TC concentration against a fixed PM5-S dose indicating competitive inhibition. Experiments using NTCP-expressing Xenopus oocytes confirmed that PM4-S/PM5-S are capable of competitively inhibiting NTCP-mediated uptake of [3H]TC. Total serum PM4-S + PM5-S levels were measured in non-pregnant and third trimester pregnant women using liquid chromatography-electrospray tandem mass spectrometry and were increased in pregnant women, at levels capable of inhibiting TC uptake. In conclusion, pregnancy levels of P4-S can inhibit Na+-dependent and -independent influx of taurocholate in PHH and cause competitive inhibition of NTCP-mediated uptake of taurocholate in Xenopus oocytes. PMID:20177056

  18. Conformationally-restricted amino acid analogues bearing a distal sulfonic acid show selective inhibition of system x(c)(-) over the vesicular glutamate transporter.

    PubMed

    Etoga, Jean-Louis G; Ahmed, S Kaleem; Patel, Sarjubhai; Bridges, Richard J; Thompson, Charles M

    2010-04-15

    A panel of amino acid analogs and conformationally-restricted amino acids bearing a sulfonic acid were synthesized and tested for their ability to preferentially inhibit the obligate cysteine-glutamate transporter system x(c)(-) versus the vesicular glutamate transporter (VGLUT). Several promising candidate molecules were identified: R/S-4-[4'-carboxyphenyl]-phenylglycine, a biphenyl substituted analog of 4-carboxyphenylglycine and 2-thiopheneglycine-5-sulfonic acid both of which reduced glutamate uptake at system x(c)(-) by 70-75% while having modest to no effect on glutamate uptake at VGLUT.

  19. Theory of ion transport with fast acid-base equilibrations in bioelectrochemical systems

    NASA Astrophysics Data System (ADS)

    Dykstra, J. E.; Biesheuvel, P. M.; Bruning, H.; Ter Heijne, A.

    2014-07-01

    Bioelectrochemical systems recover valuable components and energy in the form of hydrogen or electricity from aqueous organic streams. We derive a one-dimensional steady-state model for ion transport in a bioelectrochemical system, with the ions subject to diffusional and electrical forces. Since most of the ionic species can undergo acid-base reactions, ion transport is combined in our model with infinitely fast ion acid-base equilibrations. The model describes the current-induced ammonia evaporation and recovery at the cathode side of a bioelectrochemical system that runs on an organic stream containing ammonium ions. We identify that the rate of ammonia evaporation depends not only on the current but also on the flow rate of gas in the cathode chamber, the diffusion of ammonia from the cathode back into the anode chamber, through the ion exchange membrane placed in between, and the membrane charge density.

  20. Evidence for transport intermediates in aromatic amino acid synthesis of non-green tissues

    SciTech Connect

    Leuschner, C.; Schultz, G. )

    1990-05-01

    Quinate (QA) is the predominant pre-aromatic compound formed at high rates in leaves of many plants at the early vegetation stage and transported through the phloem. The transfer of 3-dehydroquinate, 3-dehydroshikimate and (SkA) across the plastidial membranes has been evidenced. The question was whether the rate of QA uptake is comparable to that of the 3 SkA-pathway intermediates. To demonstrate this, /U-{sup 14}C/QA and /U-{sup 14}C/SkA were applied to Brassica rapa roots. Both compounds were uptaken at considerable rates and incorporated into aromatic amino acids (Phe + Tyr + Trp formation, in nmol/g fresh wt x h: applying 145 {mu}mol QA: 21.2; applying 156 {mu}mol Ska: 31.8). Thus, QA is a possible candidate for transport into non-green tissues for aromatic amino acid synthesis.

  1. Immunohistochemical localization of fatty acid transporters and MCT1 in the sebaceous glands of mouse skin.

    PubMed

    Zheng, Miao; Lee, Shinhye; Tsuzuki, Satoshi; Inoue, Kazuo; Masuda, Daisaku; Yamashita, Shizuya; Iwanaga, Toshihiko

    2016-01-01

    The sebaceous glands secrete sebum to protect the epidermis and hairs by the oily products. The glands express several transporters and binding proteins for the production of fatty acids and uptake of their sources. The present immunohistochemical study examined the expression and localization of CD36, MCT1, FATP4, and E-FABP in the sebaceous glands, including the meibomian and preputial glands of mice. CD36 and MCT1 in sebaceous glands were largely co-localized along the plasma membrane of secretory cells, while they were separately expressed in the glandular portion of meibomian and preputial glands. Immunoreactivities for FATP4 and E-FABP appeared diffusely in the cytoplasm of secretory cells. Genetic deletion of CD36 did not affect the immunolocalization of the three other molecules. The sebaceous glands were judged to be useful for analyzing the functions and relation of fatty acid transporters and binding proteins. PMID:27545003

  2. Theory of ion transport with fast acid-base equilibrations in bioelectrochemical systems.

    PubMed

    Dykstra, J E; Biesheuvel, P M; Bruning, H; Ter Heijne, A

    2014-07-01

    Bioelectrochemical systems recover valuable components and energy in the form of hydrogen or electricity from aqueous organic streams. We derive a one-dimensional steady-state model for ion transport in a bioelectrochemical system, with the ions subject to diffusional and electrical forces. Since most of the ionic species can undergo acid-base reactions, ion transport is combined in our model with infinitely fast ion acid-base equilibrations. The model describes the current-induced ammonia evaporation and recovery at the cathode side of a bioelectrochemical system that runs on an organic stream containing ammonium ions. We identify that the rate of ammonia evaporation depends not only on the current but also on the flow rate of gas in the cathode chamber, the diffusion of ammonia from the cathode back into the anode chamber, through the ion exchange membrane placed in between, and the membrane charge density. PMID:25122405

  3. Column experiments to investigate transport of colloidal humic acid through porous media during managed aquifer recharge

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Zhou, Jingjing; Zhang, Wenjing; Huan, Ying; Yu, Xipeng; Li, Fulin; Chen, Xuequn

    2016-09-01

    Colloids act as vectors for pollutants in groundwater, thereby creating a series of environmental problems. While managed aquifer recharge plays an important role in protecting groundwater resources and controlling land subsidence, it has a significant effect on the transport of colloids. In this study, particle size and zeta potential of colloidal humic acid (HA) have been measured to determine the effects of different hydrochemistry conditions. Column experiments were conducted to examine the effects on the transport of colloidal HA under varying conditions of pH (5, 7, 9), ionic strength (<0.0005, 0.02, 0.05 M), cation valence (Na+, Ca2+) and flow rate (0.1, 0.2, 0.4 ml/min) through collectors (glass beads) to model the properties and quality of artificial recharge water and changes in the hydrodynamic field. Breakthrough curves showed that the behavior of colloidal HA being transported varied depending on the conditions. Colloid transport was strongly influenced by hydrochemical and hydrodynamic conditions. With decreasing pH or increasing ionic strength, a decrease in the peak effluent concentration of colloidal HA and increase in deposition could be clearly seen. Comparison of different cation valence tests indicated that changes in transport and deposition were more pronounced with divalent Ca2+ than with monovalent Na+. Changes in hydrodynamic field (flow rate) also had an impact on transportation of colloidal HA. The results of this study highlight the need for further research in this area.

  4. Improved Experimental Techniques for Analyzing Nucleic Acid Transport Through Protein Nanopores in Planar Lipid Bilayers

    NASA Astrophysics Data System (ADS)

    Costa, Justin A.

    The translocation of nucleic acid polymers across cell membranes is a fundamental requirement for complex life and has greatly contributed to genomic molecular evolution. The diversity of pathways that have evolved to transport DNA and RNA across membranes include protein receptors, active and passive transporters, endocytic and pinocytic processes, and various types of nucleic acid conducting channels known as nanopores. We have developed a series of experimental techniques, collectively known as "Wicking", that greatly improves the biophysical analysis of nucleic acid transport through protein nanopores in planar lipid bilayers. We have verified the Wicking method using numerous types of classical ion channels including the well-studied chloride selective channel, CLIC1. We used the Wicking technique to reconstitute α-hemolysin and found that DNA translocation events of types A and B could be routinely observed using this method. Furthermore, measurable differences were observed in the duration of blockade events as DNA length and composition was varied, consistent with previous reports. Finally, we tested the ability of the Wicking technology to reconstitute the dsRNA transporter Sid-1. Exposure to dsRNAs of increasing length and complexity showed measurable differences in the current transitions suggesting that the charge carrier was dsRNA. However, the translocation events occurred so infrequently that a meaningful electrophysiological analysis was not possible. Alterations in the lipid composition of the bilayer had a minor effect on the frequency of translocation events but not to such a degree as to permit rigorous statistical analysis. We conclude that in many instances the Wicking method is a significant improvement to the lipid bilayer technique, but is not an optimal method for analyzing transport through Sid-1. Further refinements to the Wicking method might have future applications in high throughput DNA sequencing, DNA computation, and

  5. Amyloid protein precursor stimulates excitatory amino acid transport. Implications for roles in neuroprotection and pathogenesis.

    PubMed

    Masliah, E; Raber, J; Alford, M; Mallory, M; Mattson, M P; Yang, D; Wong, D; Mucke, L

    1998-05-15

    Excitatory neurotransmitters such as glutamate are required for the normal functioning of the central nervous system but can trigger excitotoxic neuronal injury if allowed to accumulate to abnormally high levels. Their extracellular levels are controlled primarily by transmitter uptake into astrocytes. Here, we demonstrate that the amyloid protein precursor may participate in the regulation of this important process. The amyloid protein precursor has been well conserved through evolution, and a number of studies indicate that it may function as an endogenous excitoprotectant. However, the mechanisms underlying this neuroprotective capacity remain largely unknown. At moderate levels of expression, human amyloid protein precursors increased glutamate/aspartate uptake in brains of transgenic mice, with the 751-amino acid isoform showing greater potency than the 695-amino acid isoform. Cerebral glutamate/aspartate transporter protein levels were higher in transgenic mice than in non-transgenic controls, whereas transporter mRNA levels were unchanged. Amyloid protein precursor-dependent stimulation of aspartate uptake by cultured primary astrocytes was associated with increases in protein kinase A and C activity and could be blocked by inhibitors of these kinases. The stimulation of astroglial excitatory amino acid transport by amyloid protein precursors could protect the brain against excitotoxicity and may play an important role in neurotransmission. PMID:9575214

  6. Stimulation of the amino acid transporter SLC6A19 by JAK2

    SciTech Connect

    Bhavsar, Shefalee K.; Hosseinzadeh, Zohreh; Merches, Katja; Gu, Shuchen; Broeer, Stefan; Lang, Florian

    2011-10-28

    Highlights: Black-Right-Pointing-Pointer The amino acid transporter SLC6A19 is upregulated by Janus kinase-2 JAK2. Black-Right-Pointing-Pointer The {sup V617F}JAK2 mutant, causing myeloproliferative disease, is more effective. Black-Right-Pointing-Pointer JAK2 inhibitor AG490 reverses stimulation of SLC6A19 by {sup V617F}JAK2. Black-Right-Pointing-Pointer JAK2 enhances SLC6A19 protein insertion into the cell membrane. Black-Right-Pointing-Pointer SLC6A19 may contribute to amino acid uptake into {sup V617F}JAK2 expressing tumor cells. -- Abstract: JAK2 (Janus kinase-2) is expressed in a wide variety of cells including tumor cells and contributes to the proliferation and survival of those cells. The gain of function mutation {sup V617F}JAK2 mutant is found in the majority of myeloproliferative diseases. Cell proliferation depends on the availability of amino acids. Concentrative cellular amino acid uptake is in part accomplished by Na{sup +} coupled amino acid transport through SLC6A19 (B(0)AT). The present study thus explored whether JAK2 activates SLC6A19. To this end, SLC6A19 was expressed in Xenopus oocytes with or without wild type JAK2, {sup V617F}JAK2 or inactive {sup K882E}JAK2 and electrogenic amino acid transport determined by dual electrode voltage clamp. In SLC6A19-expressing oocytes but not in oocytes injected with water or JAK2 alone, the addition of leucine (2 mM) to the bath generated a current (I{sub le}), which was significantly increased following coexpression of JAK2 or {sup V617F}JAK2, but not by coexpression of {sup K882E}JAK2. Coexpression of JAK2 enhanced the maximal transport rate without significantly modifying the affinity of the carrier. Exposure of the oocytes to the JAK2 inhibitor AG490 (40 {mu}M) resulted in a gradual decline of I{sub le}. According to chemiluminescence JAK2 enhanced the carrier protein abundance in the cell membrane. The decline of I{sub le} following inhibition of carrier insertion by brefeldin A (5 {mu}M) was similar

  7. Dietary docosahexaenoic acid supplementation reduces SERCA Ca2+ transport efficiency in rat skeletal muscle.

    PubMed

    Fajardo, Val Andrew; Bombardier, Eric; Irvine, Thomas; Metherel, Adam H; Stark, Ken D; Duhamel, Todd; Rush, James W E; Green, Howard J; Tupling, A Russell

    2015-04-01

    Docosahexaenoic acid (DHA) can reduce the efficiency and increase the energy consumption of Na(+)/K(+)-ATPase pump and mitochondrial electron transport chain by promoting Na(+) and H(+) membrane permeability, respectively. In skeletal muscle, the sarco(endo) plasmic reticulum Ca(2+)-ATPase (SERCA) pumps are major contributors to resting metabolic rate. Whether DHA can affect SERCA efficiency remains unknown. Here, we examined the hypothesis that dietary supplementation with DHA would reduce Ca(2+) transport efficiency of the SERCA pumps in skeletal muscle. Total lipids were extracted from enriched sarcoplasmic reticulum (SR) membranes that were isolated from red vastus lateralis skeletal muscles of rats that were either fed a standard chow diet supplemented with soybean oil or supplemented with DHA for 8 weeks. The fatty acid composition of total SR membrane lipids and the major phospholipid species were determined using electrospray ionization mass spectrometry (ESI-MS). After 8 weeks of DHA supplementation, total SR DHA content was significantly elevated (control, 4.1 ± 1.0% vs. DHA, 9.9 ± 1.7%; weight percent of total fatty acids) while total arachidonic acid was reduced (control, 13.5 ± 0.4% vs. DHA-fed, 9.4 ± 0.2). Similar changes in these fatty acids were observed in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, altogether indicating successful incorporation of DHA into the SR membranes post-diet. As hypothesized, DHA supplementation reduced SERCA Ca(2+) transport efficiency (control, 0.018 ± 0.0002 vs. DHA-fed, 0.014 ± 0.0009) possibly through enhanced SR Ca(2+) permeability (ionophore ratio: control, 2.8 ± 0.2 vs. DHA-fed, 2.2 ± 0.3). Collectively, our results suggest that DHA may promote skeletal muscle-based metabolism and thermogenesis through its influence on SERCA.

  8. Transport of. cap alpha. -aminoisobutyric acid by Streptococcus pyogenes and its derived L-form

    SciTech Connect

    Reizer, J.; Panos, C.

    1982-01-01

    We studied the uptake of ..cap alpha..-aminoisobutyric acid (AIB) in Streptococcus pyogenes and its physiologically isotonic L-form. S. pyogenes cells starved for glucose or treated with carbonyl cyanide-m-chlorophenyl hydrazone accumulated limited amounts of AIB. A high apparent K/sub m/ value characterized the glucose-independent transport of AIB. The rate and extent of AIB accumulation significantly increased in the presence of glucose. Two saturable transport components with distinct apparent K/sub m/values characterized glycolysis-coupled transport of AIB. A biphasic Lineweaver-Burk plot was also obtained for L-alanine transport by glycolyzing S. pyogenes cells. AIB seems to share a common transport system(s) with glycine, L- and D-anine, L-serine, and L-valine. This was shown by the competitive exchange efflux of accumulated AIB. About 30% of the AIB uptake was not inhibited by a saturating amount of L-valine, indicating the existence of more than one system for AIB transport, p-Chloromercuribenzoate markedly inhibited the accumulation of AIB by both glycolyzing and glucose-starved cells. In contrast, carbonyl cyanide-m-chlorophenyl hydrazone affected only metabolism-dependent uptake of AIB, which was also sensitive to dinitrophenol, N-ethylmaleimide, iodoacetate, fluoride (NaF), arsenate, and N,N'-dicyclohexylcarbodiimide. These results are interpreted according to the chemiosmotic theory of Mitchell, whereby a proton motive force constitutes the driving force for AIB accumulation. AIB was not accumulated by the L-form. However, a temporary accumulation of AIB by a counterflow mechanism and a saturable system with a low apparent affinity were demonstrated for AIB transport by this organism. We suggest that a deficiency in the coupling of energy to AIB transport is responsible for the apparent lack of active AIB accumulation by the L-form.

  9. Interaction of α-Lipoic Acid with the Human Na+/Multivitamin Transporter (hSMVT)*

    PubMed Central

    Zehnpfennig, Britta; Wiriyasermkul, Pattama; Carlson, David A.; Quick, Matthias

    2015-01-01

    The human Na+/multivitamin transporter (hSMVT) has been suggested to transport α-lipoic acid (LA), a potent antioxidant and anti-inflammatory agent used in therapeutic applications, e.g. in the treatment of diabetic neuropathy and Alzheimer disease. However, the molecular basis of the cellular delivery of LA and in particular the stereospecificity of the transport process are not well understood. Here, we expressed recombinant hSMVT in Pichia pastoris and used affinity chromatography to purify the detergent-solubilized protein followed by reconstitution of hSMVT in lipid bilayers. Using a combined approach encompassing radiolabeled LA transport and equilibrium binding studies in conjunction with the stabilized R-(+)- and S-(−)-enantiomers and the R,S-(+/−) racemic mixture of LA or lipoamide, we identified the biologically active form of LA, R-LA, to be the physiological substrate of hSMVT. Interaction of R-LA with hSMVT is strictly dependent on Na+. Under equilibrium conditions, hSMVT can simultaneously bind ∼2 molecules of R-LA in a biphasic binding isotherm with dissociation constants (Kd) of 0.9 and 7.4 μm. Transport of R-LA in the oocyte and reconstituted system is exclusively dependent on Na+ and exhibits an affinity of ∼3 μm. Measuring transport with known amounts of protein in proteoliposomes containing hSMVT in outside-out orientation yielded a catalytic turnover number (kcat) of about 1 s−1, a value that is well in agreement with other Na+-coupled transporters. Our data suggest that hSMVT-mediated transport is highly specific for R-LA at our tested concentration range, a finding with wide ramifications for the use of LA in therapeutic applications. PMID:25971966

  10. Size does matter: 18 amino acids at the N-terminal tip of an amino acid transporter in Leishmania determine substrate specificity

    PubMed Central

    Schlisselberg, Doreen; Mazarib, Eldar; Inbar, Ehud; Rentsch, Doris; Myler, Peter J.; Zilberstein, Dan

    2015-01-01

    Long N-terminal tails of amino acid transporters are known to act as sensors of the internal pool of amino acids and as positive regulators of substrate flux rate. In this study we establish that N-termini of amino acid transporters can also determine substrate specificity. We show that due to alternative trans splicing, the human pathogen Leishmania naturally expresses two variants of the proline/alanine transporter, one 18 amino acid shorter than the other. We demonstrate that the longer variant (LdAAP24) translocates both proline and alanine, whereas the shorter variant (∆18LdAAP24) translocates just proline. Remarkably, co-expressing the hydrophilic N-terminal peptide of the long variant with ∆18LdAAP24 was found to recover alanine transport. This restoration of alanine transport could be mediated by a truncated N-terminal tail, though truncations exceeding half of the tail length were no longer functional. Taken together, the data indicate that the first 18 amino acids of the negatively charged N-terminal LdAAP24 tail are required for alanine transport and may facilitate the electrostatic interactions of the entire negatively charged N-terminal tail with the positively charged internal loops in the transmembrane domain, as this mechanism has been shown to underlie regulation of substrate flux rate for other transporters. PMID:26549185

  11. cAMP increases mitochondrial cholesterol transport through the induction of arachidonic acid release inside this organelle in Leydig cells.

    PubMed

    Castillo, Ana Fernanda; Cornejo Maciel, Fabiana; Castilla, Rocío; Duarte, Alejandra; Maloberti, Paula; Paz, Cristina; Podestá, Ernesto J

    2006-11-01

    We have investigated the direct effect of arachidonic acid on cholesterol transport in intact cells or isolated mitochondria from steroidogenic cells and the effect of cyclic-AMP on the specific release of this fatty acid inside the mitochondria. We show for the first time that cyclic-AMP can regulate the release of arachidonic acid in a specialized compartment of MA-10 Leydig cells, e.g. the mitochondria, and that the fatty acid induces cholesterol transport through a mechanism different from the classical pathway. Arachidonic acid and arachidonoyl-CoA can stimulate cholesterol transport in isolated mitochondria from nonstimulated cells. The effect of arachidonoyl-CoA is inhibited by the reduction in the expression or in the activity of a mitochondrial thioesterase that uses arachidonoyl-CoA as a substrate to release arachidonic acid. cAMP-induced arachidonic acid accumulation into the mitochondria is also reduced when the mitochondrial thioesterase activity or expression is blocked. This new feature in the regulation of cholesterol transport by arachidonic acid and the release of arachidonic acid in specialized compartment of the cells could offer novel means for understanding the regulation of steroid synthesis but also would be important in other situations such as neuropathological disorders or oncology disorders, where cholesterol transport plays an important role.

  12. Intestinal transport of monosaccharides and amino acids during postnatal development of mink.

    PubMed

    Buddington, R K; Malo, C; Sangild, P T; Elnif, J

    2000-12-01

    Intestinal development is typically studied using omnivores. For comparative purposes, we examined an altricial carnivore, the mink (Mustela vison). In mink, intestinal dimensions increase up to 8 wk after birth and then remain constant (length) or decrease (mass) into maturity despite continuing gains in body mass. Rates of glucose and fructose transport decline after birth for intact tissues but increase for brush-border membrane vesicles (BBMV). Rates of absorption for five amino acids that are substrates for the acidic (aspartate), basic (lysine), neutral (leucine and methionine), and imino acid (proline) carriers increase between birth and 24 h for intact tissues before declining, but increase after 2 wk for BBMV. The proportion of BBMV amino acid uptake that is Na(+)-dependent increases during development but for aspartate is nearly 100% at all ages. Tracer uptake by BBMV can be inhibited by 100 mmol/l of unlabeled amino acid, except for lysine. BBMV uptake of the dipeptide glycyl-sarcosine does not differ between ages, is not Na(+) dependent, and is only partially inhibited by 100 mmol/l unlabeled dipeptide. Despite the ability to rapidly and efficiently digest high dietary loads of protein, rates of amino acid and peptide absorption are not markedly higher than those of other mammals.

  13. Peptide modules for overcoming barriers of nucleic acids transport to cells.

    PubMed

    Egorova, Anna A; Kiselev, Anton V

    2016-01-01

    Absence of safe and efficient methods of nucleic acids delivery is one of the major issues which limits the development of human gene therapy. Highly efficient viral vectors raise questions due to safety reasons. Among non-viral vectors peptide-based carriers can be considered as good candidates for the development of "artificial viruses"--multifunctional polyplexes that mimic viruses. Suggested strategy to obtain multifunctionality is to combine several peptide modules into one modular carrier. Different kinds of peptide modules are needed for successful overcoming barriers of nucleic acids transport into the cells. Design of such modules and establishment of structure-function relationships are issues of importance to researchers working in the field of nucleic acids delivery.

  14. Acid-extrusion from tissue: the interplay between membrane transporters and pH buffers.

    PubMed

    Hulikova, Alzbeta; Harris, Adrian L; Vaughan-Jones, Richard D; Swietach, Pawel

    2012-01-01

    The acid-base balance of cells is related to the concentration of free H⁺ ions. These are highly reactive, and their intracellular concentration must be regulated to avoid detrimental effects to the cell. H⁺ ion dynamics are influenced by binding to chelator substances ('buffering'), and by the production, diffusion and membrane-transport of free H⁺ ions or of the H⁺-bound chelators. Intracellular pH (pHi) regulation aims to balance this system of diffusion-reaction-transport processes at a favourable steady-state pHi. The ability of cells to regulate pHi may set a limit to tissue growth and can be subject to selection pressures. Cancer cells have been postulated to respond favourably to such selection pressures by evolving a better means of pHi regulation. A particularly important feature of tumour pHi regulation is acid-extrusion, which involves H⁺-extrusion and HCO₃⁻-uptake by membrane-bound transporter-proteins. Extracellular CO₂/HCO₃⁻ buffer facilitates these membrane-transport processes. As a mobile pH-buffer, CO₂/HCO₃⁻ protects the extracellular space from excessive acidification that could otherwise inhibit further acid-extrusion. CO₂/HCO₃⁻ also provides substrate for HCO₃⁻-transporters. However, the inherently slow reaction kinetics of CO₂/HCO₃⁻ can be rate-limiting for acid-extrusion. To circumvent this, cells can express extracellular-facing carbonic anhydrase enzymes to accelerate the attainment of equilibrium between CO₂, HCO₃⁻ and H⁺. The acid-extrusion apparatus has been proposed as a target for anti-cancer therapy. The major targets include H⁺ pumps, Na⁺/H⁺ exchangers and carbonic anhydrases. The effectiveness of such therapy will depend on the correct identification of rate-limiting steps in pHi regulation in a specific type of cancer. PMID:22360560

  15. PDR-type ABC transporter mediates cellular uptake of the phytohormone abscisic acid

    PubMed Central

    Kang, Joohyun; Hwang, Jae-Ung; Kim, Yu-Young; Assmann, Sarah M.; Martinoia, Enrico; Lee, Youngsook

    2010-01-01

    Abscisic acid (ABA) is a ubiquitous phytohormone involved in many developmental processes and stress responses of plants. ABA moves within the plant, and intracellular receptors for ABA have been recently identified; however, no ABA transporter has been described to date. Here, we report the identification of the ATP-binding cassette (ABC) transporter Arabidopsis thaliana Pleiotropic drug resistance transporter PDR12 (AtPDR12)/ABCG40 as a plasma membrane ABA uptake transporter. Uptake of ABA into yeast and BY2 cells expressing AtABCG40 was increased, whereas ABA uptake into protoplasts of atabcg40 plants was decreased compared with control cells. In response to exogenous ABA, the up-regulation of ABA responsive genes was strongly delayed in atabcg40 plants, indicating that ABCG40 is necessary for timely responses to ABA. Stomata of loss-of-function atabcg40 mutants closed more slowly in response to ABA, resulting in reduced drought tolerance. Our results integrate ABA-dependent signaling and transport processes and open another avenue for the engineering of drought-tolerant plants. PMID:20133880

  16. Physiologic hyperinsulinemia stimulates protein synthesis and enhances transport of selected amino acids in human skeletal muscle.

    PubMed Central

    Biolo, G; Declan Fleming, R Y; Wolfe, R R

    1995-01-01

    We have investigated the mechanisms of the anabolic effect of insulin on muscle protein metabolism in healthy volunteers, using stable isotopic tracers of amino acids. Calculations of muscle protein synthesis, breakdown, and amino acid transport were based on data obtained with the leg arteriovenous catheterization and muscle biopsy. Insulin was infused (0.15 mU/min per 100 ml leg) into the femoral artery to increase femoral venous insulin concentration (from 10 +/- 2 to 77 +/- 9 microU/ml) with minimal systemic perturbations. Tissue concentrations of free essential amino acids decreased (P < 0.05) after insulin. The fractional synthesis rate of muscle protein (precursor-product approach) increased (P < 0.01) after insulin from 0.0401 +/- 0.0072 to 0.0677 +/- 0.0101%/h. Consistent with this observation, rates of utilization for protein synthesis of intracellular phenylalanine and lysine (arteriovenous balance approach) also increased from 40 +/- 8 to 59 +/- 8 (P < 0.05) and from 219 +/- 21 to 298 +/- 37 (P < 0.08) nmol/min per 100 ml leg, respectively. Release from protein breakdown of phenylalanine, leucine, and lysine was not significantly modified by insulin. Local hyperinsulinemia increased (P < 0.05) the rates of inward transport of leucine, lysine, and alanine, from 164 +/- 22 to 200 +/- 25, from 126 +/- 11 to 221 +/- 30, and from 403 +/- 64 to 595 +/- 106 nmol/min per 100 ml leg, respectively. Transport of phenylalanine did not change significantly. We conclude that insulin promoted muscle anabolism, primarily by stimulating protein synthesis independently of any effect on transmembrane transport. Images PMID:7860765

  17. Transport of Indole-3-Butyric Acid and Indole-3-Acetic Acid in Arabidopsis Hypocotyls Using Stable Isotope Labeling1[C][W][OA

    PubMed Central

    Liu, Xing; Barkawi, Lana; Gardner, Gary; Cohen, Jerry D.

    2012-01-01

    The polar transport of the natural auxins indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA) has been described in Arabidopsis (Arabidopsis thaliana) hypocotyls using radioactive tracers. Because radioactive assays alone cannot distinguish IBA from its metabolites, the detected transport from applied [3H]IBA may have resulted from the transport of IBA metabolites, including IAA. To test this hypothesis, we used a mass spectrometry-based method to quantify the transport of IBA in Arabidopsis hypocotyls by following the movement of [13C1]IBA and the [13C1]IAA derived from [13C1]IBA. We also assayed [13C6]IAA transport in a parallel control experiment. We found that the amount of transported [13C1]IBA was dramatically lower than [13C6]IAA, and the IBA transport was not reduced by the auxin transport inhibitor N-1-naphthylphthalamic acid. Significant amounts of the applied [13C1]IBA were converted to [13C1]IAA during transport, but [13C1]IBA transport was independent of IBA-to-IAA conversion. We also found that most of the [13C1]IBA was converted to ester-linked [13C1]IBA at the apical end of hypocotyls, and ester-linked [13C1]IBA was also found in the basal end at a level higher than free [13C1]IBA. In contrast, most of the [13C6]IAA was converted to amide-linked [13C6]IAA at the apical end of hypocotyls, but very little conjugated [13C6]IAA was found in the basal end. Our results demonstrate that the polar transport of IBA is much lower than IAA in Arabidopsis hypocotyls, and the transport mechanism is distinct from IAA transport. These experiments also establish a method for quantifying the movement of small molecules in plants using stable isotope labeling. PMID:22323783

  18. Stable isotope tracer reveals that viviparous snakes transport amino acids to offspring during gestation.

    PubMed

    Van Dyke, James U; Beaupre, Steven J

    2012-03-01

    Viviparity and placentation have evolved from oviparity over 100 times in squamate reptiles (lizards and snakes). The independent origins of placentation have resulted in a variety of placental morphologies in different taxa, ranging from simple apposition of fetal and maternal tissues to endotheliochorial implantation that is homoplasious with mammalian placentation. Because the eggs of oviparous squamates transport gases and water from the environment and calcium from the eggshell, the placentae of viviparous squamates are thought to have initially evolved to accomplish these functions from within the maternal oviduct. Species with complex placentae have also been shown to rely substantially, or even primarily, on placental transport of organic nutrients for embryonic nutrition. However, it is unclear whether species with only simple placentae are also capable of transporting organic nutrients to offspring. Among viviparous squamates, all of the snakes that have been studied thus far have been shown to have simple placentae. However, most studies of snake placentation are limited to a single lineage, the North American Natricinae. We tested the abilities of four species of viviparous snakes - Agkistrodon contortrix (Viperidae), Boa constrictor (Boidae), Nerodia sipedon (Colubridae: Natricinae) and Thamnophis sirtalis (Colubridae: Natricinae) - to transport diet-derived amino acids to offspring during gestation. We fed [(15)N]leucine to pregnant snakes, and compared offspring (15)N content with that of unlabeled controls. Labeled females allocated significantly more (15)N to offspring than did controls, but (15)N allocation did not differ among species. Our results indicate that viviparous snakes are capable of transporting diet-derived amino acids to their offspring during gestation, possibly via placentation.

  19. Excitatory amino acid transporter 2 downregulation correlates with thalamic neuronal death following kainic acid-induced status epilepticus in rat.

    PubMed

    Sakurai, Masashi; Kurokawa, Haruna; Shimada, Akinori; Nakamura, Kazuhiro; Miyata, Hajime; Morita, Takehito

    2015-02-01

    Recurrent seizures without interictal resumption (status epilepticus) have been reported to induce neuronal death in the midline thalamic region that has functional roles in memory and decision-making; however, the pathogenesis underlying status epilepticus-induced thalamic neuronal death is yet to be determined. We performed histological and immunohistochemical studies as well as cerebral blood flow measurement using 4.7 tesla magnetic resonance imaging spectrometer on midline thalamic region in Sprague-Dawley rats (n = 75, male, 7 weeks after birth, body weight 250-300 g) treated with intraperitoneal injection of kainic acid (10 mg/kg) to induce status epilepticus (n = 55) or normal saline solution (n = 20). Histological study using paraffin-embedded specimens revealed neuronal death showing ischemic-like changes and Fluoro-Jade C positivity with calcium deposition in the midline thalamic region of epileptic rats. The distribution of neuronal death was associated with focal loss of immunoreactivity for excitatory amino acid transporter 2 (EAAT2), stronger immunoreaction for glutamate and increase in number of Iba-1-positive microglial cells showing swollen cytoplasm and long processes. Double immunofluorescence study demonstrated co-expression of interleukin-1 beta (IL-1β) and inducible nitric oxide synthase (iNOS) within microglial cells, and loss of EAAT2 immunoreactivity in reactive astrocytes. These microglial alterations and astrocytic EAAT2 downregulation were also observed in tissue without obvious neuronal death in kainic acid-treated rats. These results suggest the possible role of glutamate excitotoxicity in neuronal death in the midline thalamic region following kainic acid-induced status epilepticus due to astrocytic EAAT2 downregulation following microglial activation showing upregulation of IL-1β and iNOS.

  20. Peroxisomal beta-oxidation of branched chain fatty acids in rat liver. Evidence that carnitine palmitoyltransferase I prevents transport of branched chain fatty acids into mitochondria.

    PubMed

    Singh, H; Beckman, K; Poulos, A

    1994-04-01

    Fatty acid beta-oxidation was investigated in highly purified mitochondrial and peroxisomal preparations from rat liver. Under isotonic conditions, pristanic and homophytanic acid beta-oxidation in purified peroxisomes was severalfold greater compared to the oxidation in purified mitochondria. Branched chain fatty acid beta-oxidation in purified mitochondria was very low, and the oxidation was not stimulated by exogenous L-carnitine or L-malate. In contrast, stearic acid beta-oxidation by purified mitochondria depended upon exogenous L-carnitine, and the oxidation was stimulated by L-malate. Both mitochondrial and peroxisomal beta-oxidation of branched chain fatty acids was strongly inhibited by fatty acid-free bovine serum albumin, whereas stearic acid oxidation was either unaffected or slightly inhibited by bovine serum albumin. The results presented clearly indicate that branched chain fatty acids are mainly degraded in peroxisomes in rat liver. Branched chain fatty acids were efficiently converted to coenzyme A thioesters by purified mitochondria, peroxisomes, and microsomes. Although pristanic and phytanic acids were rapidly converted to pristanoyl-CoA and phytanoyl-CoA, respectively, they were not converted to carnitine esters by mitochondrial outer membranes. The results indicate that acyl-CoA synthetase and carnitine acyltransferase located at the mitochondrial outer membranes regulate entry of branched chain fatty acids into mitochondria. Mitochondrial carnitine acyltransferase I appears to be highly specific for straight chain fatty acids and restricts entry of branched chain fatty acids into mitochondria. Thus, branched chain fatty acids which cannot be transported across the mitochondrial membranes via the carnitine acyltransferase system are directed to peroxisomes for beta-oxidation. The results reported indicate that phytanic acid, the fatty acid which can be initially degraded by alpha-oxidation due to the presence of a beta-methyl group in the

  1. The contribution of SNAT1 to system A amino acid transporter activity in human placental trophoblast

    SciTech Connect

    Desforges, M.; Greenwood, S.L.; Glazier, J.D.; Westwood, M.; Sibley, C.P.

    2010-07-16

    Research highlights: {yields} mRNA levels for SNAT1 are higher than other system A subtype mRNAs in primary human cytotrophoblast. {yields} SNAT1 knockdown in cytotrophoblast cells significantly reduces system A activity. {yields} SNAT1 is a key contributor to system A-mediated amino acid transport in human placenta. -- Abstract: System A-mediated amino acid transport across the placenta is important for the supply of neutral amino acids needed for fetal growth. All three system A subtypes (SNAT1, 2, and 4) are expressed in human placental trophoblast suggesting there is an important biological role for each. Placental system A activity increases as pregnancy progresses, coinciding with increased fetal nutrient demands. We have previously shown SNAT4-mediated system A activity is higher in first trimester than at term, suggesting that SNAT1 and/or SNAT2 are responsible for the increased system A activity later in gestation. However, the relative contribution of each subtype to transporter activity in trophoblast at term has yet to be evaluated. The purpose of this study was to identify the predominant subtype of system A in cytotrophoblast cells isolated from term placenta, maintained in culture for 66 h, by: (1) measuring mRNA expression of the three subtypes and determining the Michaelis-Menten constants for uptake of the system A-specific substrate, {sup 14}C-MeAIB, (2) investigating the contribution of SNAT1 to total system A activity using siRNA. Results: mRNA expression was highest for the SNAT1 subtype of system A. Kinetic analysis of {sup 14}C-MeAIB uptake revealed two distinct transport systems; system 1: K{sub m} = 0.38 {+-} 0.12 mM, V{sub max} = 27.8 {+-} 9.0 pmol/mg protein/20 min, which resembles that reported for SNAT1 and SNAT2 in other cell types, and system 2: K{sub m} = 45.4 {+-} 25.0 mM, V{sub max} = 1190 {+-} 291 pmol/mg protein/20 min, which potentially represents SNAT4. Successful knockdown of SNAT1 mRNA using target-specific si

  2. Identification of transport pathways for citric acid cycle intermediates in the human colon carcinoma cell line, Caco-2.

    PubMed

    Weerachayaphorn, Jittima; Pajor, Ana M

    2008-04-01

    Citric acid cycle intermediates are absorbed from the gastrointestinal tract through carrier-mediated mechanisms, although the transport pathways have not been clearly identified. This study examines the transport of citric acid cycle intermediates in the Caco-2 human colon carcinoma cell line, often used as a model of small intestine. Inulin was used as an extracellular volume marker instead of mannitol since the apparent volume measured with mannitol changed with time. The results show that Caco-2 cells contain at least three distinct transporters, including the Na+-dependent di- and tricarboxylate transporters, NaDC1 and NaCT, and one or more sodium-independent pathways, possibly involving organic anion transporters. Succinate transport is mediated mostly by Na+-dependent pathways, predominantly by NaDC1, but with some contribution by NaCT. RT-PCR and functional characteristics verified the expression of these transporters in Caco-2 cells. In contrast, citrate transport in Caco-2 cells occurs by a combination of Na+-independent pathways, possibly mediated by an organic anion transporter, and Na+-dependent mechanisms. The non-metabolizable dicarboxylate, methylsuccinate, is also transported by a combination of Na+-dependent and -independent pathways. In conclusion, we find that multiple pathways are involved in the transport of di- and tricarboxylates by Caco-2 cells. Since many of these pathways are not found in human intestine, this model may be best suited for studying Na+-dependent transport of succinate by NaDC1.

  3. Amino acid contents and transport of fixed N in nodules of Leucaena leucocephala variety K-8

    SciTech Connect

    DuBois, J.D.

    1987-04-01

    Seedlings of Leucaena leucocephala var. K-8 were grown with a N-free fertilizer or fertilizer containing /sup 15/N-depleted (NH/sub 4/)/sub 2/SO/sub 4/ (0.01 atom /sup 15/N; 10 ppm). The nodules of 5 month old trees grown on N-free media were used for /sup 15/N-enriched treatment and as controls. Nodules from plants grown on /sup 15/N-depleted media were also used. Nodules were extracted with 0.5% aqueous toluene and aliquots were analyzed with a Beckman 120B Amino Acid Analyzer. Samples were separated into free ammonium, Asp-N, Glu-N, Asn and Gln amide- and amino-N, and remaining amino acids. Fractions were then analyzed for /sup 15/N content. Asn (27.3 umol/gfw) represented 56% of the total free amino acid pool in the nodules. Asn (amide-N and amino-N) also represented approximately 77% of the total N fixed during the one hour /sup 15/N-enriched N/sub 2/ and the /sup 15/N-depleted treatments. Based on these findings and the fact that the ureide fraction is barely detectable in the nodules (0.25 ..mu..mol/gfw), the authors considers L. leucocephala an amide transporter of fixed N. Additional information will be presented on the amino acid contents of tissues, as well as a time course of amino acid content from seed through nodulation.

  4. A branched chain amino acid metabolite drives vascular transport of fat and causes insulin resistance

    PubMed Central

    Jang, Cholsoon; Oh, Sungwhan F; Wada, Shogo; Rowe, Glenn C; Liu, Laura; Chan, Mun Chun; Rhee, James; Hoshino, Atsushi; Kim, Boa; Ibrahim, Ayon; Baca, Luisa G; Kim, Esl; Ghosh, Chandra C; Parikh, Samir M; Jiang, Aihua; Chu, Qingwei; Forman, Daniel E.; Lecker, Stewart H.; Krishnaiah, Saikumari; Rabinowitz, Joshua D; Weljie, Aalim M; Baur, Joseph A; Kasper, Dennis L; Arany, Zoltan

    2016-01-01

    Epidemiological and experimental data implicate branched chain amino acids (BCAAs) in the development of insulin resistance, but the mechanisms underlying this link remain unclear.1–3 Insulin resistance in skeletal muscle stems from excess accumulation of lipid species4, a process that requires blood-borne lipids to first traverse the blood vessel wall. Little is known, however, of how this trans-endothelial transport occurs or is regulated. Here, we leverage PGC-1α, a transcriptional coactivator that regulates broad programs of FA consumption, to identify 3-hydroxy-isobutyrate (3-HIB), a catabolic intermediate of the BCAA valine, as a novel paracrine regulator of trans-endothelial fatty acids (FA) transport. 3-HIB is secreted from muscle cells, activates endothelial FA transport, stimulates muscle FA uptake in vivo, and promotes muscle lipid accumulation and insulin resistance in animals. Conversely, inhibiting the synthesis of 3-HIB in muscle cells blocks the promotion of endothelial FA uptake. 3-HIB levels are elevated in muscle from db/db mice and from subjects with diabetes. These data thus unveil a novel mechanism that regulates trans-endothelial flux of FAs, revealing 3-HIB as a new bioactive signaling metabolite that links the regulation of FA flux to BCAA catabolism and provides a mechanistic explanation for how increased BCAA catabolic flux can cause diabetes. PMID:26950361

  5. Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate.

    PubMed

    Maruyama, Yukie; Itoh, Takafumi; Kaneko, Ai; Nishitani, Yu; Mikami, Bunzo; Hashimoto, Wataru; Murata, Kousaku

    2015-09-01

    The acidic polysaccharide alginate represents a promising marine biomass for the microbial production of biofuels, although the molecular and structural characteristics of alginate transporters remain to be clarified. In Sphingomonas sp. A1, the ATP-binding cassette transporter AlgM1M2SS is responsible for the import of alginate across the cytoplasmic membrane. Here, we present the substrate-transport characteristics and quaternary structure of AlgM1M2SS. The addition of poly- or oligoalginate enhanced the ATPase activity of reconstituted AlgM1M2SS coupled with one of the periplasmic solute-binding proteins, AlgQ1 or AlgQ2. External fluorescence-labeled oligoalginates were specifically imported into AlgM1M2SS-containing proteoliposomes in the presence of AlgQ2, ATP, and Mg(2+). The crystal structure of AlgQ2-bound AlgM1M2SS adopts an inward-facing conformation. The interaction between AlgQ2 and AlgM1M2SS induces the formation of an alginate-binding tunnel-like structure accessible to the solvent. The translocation route inside the transmembrane domains contains charged residues suitable for the import of acidic saccharides.

  6. Interactions Between Fatty Acid Transport Proteins, Genes That Encode for Them, and Exercise: A Systematic Review.

    PubMed

    Jayewardene, Avindra F; Mavros, Yorgi; Reeves, Anneliese; Hancock, Dale P; Gwinn, Tom; Rooney, Kieron B

    2016-08-01

    Long-chain fatty acid (LCFA) movement into skeletal muscle involves a highly mediated process in which lipid rafts are utilized in the cellular membrane, involving numerous putative plasma membrane-associated LCFA transport proteins. The process of LCFA uptake and oxidation is of particular metabolic significance both at rest and during light to moderate exercise. A comprehensive systematic search of electronic databases was conducted to investigate whether exercise alters protein and/or gene expression of putative LCFA transport proteins. There were 31 studies meeting all eligibility criteria, of these 13 utilized an acute exercise protocol and 18 examined chronic exercise adaptations. Seventeen involved a study design incorporating an exercise stimulus, while the remaining 14 incorporated a combined exercise and diet stimulus. Divergent data relating to acute exercise, as well as prolonged exercise training (≥3 weeks), on protein content (PC) response was identified for proteins CD36, FABPpm and CAV1. Messenger ribonucleic acid (mRNA) data did not always correspond to functional PC, supporting previous suggestions of a disconnect due to potentially limiting factors post gene expression. The large array of study designs, cohorts, and primary dependent variables within the studies included in the present review elucidate the complexity of the interaction between exercise and LCFA transport proteins. Summary of the results in the present review validate the need for further targeted investigation within this topic, and provide an important information base for such research. J. Cell. Physiol. 231: 1671-1687, 2016. © 2015 Wiley Periodicals, Inc.

  7. Influence of Perfluorooctanoic Acid on the Transport and Deposition Behaviors of Bacteria in Quartz Sand.

    PubMed

    Wu, Dan; Tong, Meiping; Kim, Hyunjung

    2016-03-01

    The significance of perfluorooctanoic acid (PFOA) on the transport and deposition behaviors of bacteria (Gram-negative Escherichia coli and Gram-positive Bacillus subtilis) in quartz sand is examined in both NaCl and CaCl2 solutions at pH 5.6 by comparing both breakthrough curves and retained profiles with PFOA in solutions versus those without PFOA. All test conditions are found to be highly unfavorable for cell deposition regardless of the presence of PFOA; however, 7%-46% cell deposition is observed depending on the conditions. The cell deposition may be attributed to micro- or nanoscale roughness and/or to chemical heterogeneity of the sand surface. The results show that, under all examined conditions, PFOA in suspensions increases cell transport and decreases cell deposition in porous media regardless of cell type, presence or absence of extracellular polymeric substances, ionic strength, and ion valence. We find that the additional repulsion between bacteria and quartz sand caused by both acid-base interaction and steric repulsion as well as the competition for deposition sites on quartz sand surfaces by PFOA are responsible for the enhanced transport and decreased deposition of bacteria with PFOA in solutions.

  8. Assessment of Amino Acid/Drug Transporters for Renal Transport of [18F]Fluciclovine (anti-[18F]FACBC) in Vitro

    PubMed Central

    Ono, Masahiro; Baden, Atsumi; Okudaira, Hiroyuki; Kobayashi, Masato; Kawai, Keiichi; Oka, Shuntaro; Yoshimura, Hirokatsu

    2016-01-01

    [18F]Fluciclovine (trans-1-amino-3-[18F]fluorocyclobutanecarboxylic acid; anti-[18F]FACBC), a positron emission tomography tracer used for the diagnosis of recurrent prostate cancer, is transported via amino acid transporters (AATs) with high affinity (Km: 97–230 μM). However, the mechanism underlying urinary excretion is unknown. In this study, we investigated the involvement of AATs and drug transporters in renal [18F]fluciclovine reuptake. [14C]Fluciclovine (trans-1-amino-3-fluoro[1-14C]cyclobutanecarboxylic acid) was used because of its long half-life. The involvement of AATs in [14C]fluciclovine transport was measured by apical-to-basal transport using an LLC-PK1 monolayer as model for renal proximal tubules. The contribution of drug transporters herein was assessed using vesicles/cells expressing the drug transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), multidrug resistance-associated protein 4 (MRP4), organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3) , organic cation transporter 2 (OCT2), organic anion transporting polypeptide 1B1 (OATP1B1), and organic anion transporting polypeptide 1B3 (OATP1B3). The apical-to-basal transport of [14C]fluciclovine was attenuated by l-threonine, the substrate for system alanine-serine-cysteine (ASC) AATs. [14C]Fluciclovine uptake by drug transporter-expressing vesicles/cells was not significantly different from that of control vesicles/cells. Fluciclovine inhibited P-gp, MRP4, OAT1, OCT2, and OATP1B1 (IC50 > 2.95 mM). Therefore, system ASC AATs may be partly involved in the renal reuptake of [18F]fluciclovine. Further, given that [18F]fluciclovine is recognized as an inhibitor with millimolar affinity for the tested drug transporters, slow urinary excretion of [18F]fluciclovine may be mediated by system ASC AATs, but not by drug transporters. PMID:27754421

  9. Threonine deprivation rapidly activates the system A amino acid transporter in primary cultures of rat neurons from the essential amino acid sensor in the anterior piriform cortex.

    PubMed

    Blais, Anne; Huneau, Jean-François; Magrum, Linda J; Koehnle, Thomas J; Sharp, James W; Tomé, Daniel; Gietzen, Dorothy W

    2003-07-01

    Omnivores show recognition of essential (indispensable) amino acid deficiency by changing their feeding behavior within 20 min, yet the cellular mechanisms of amino acid sensation in eukaryotes are poorly understood. The anterior piriform cortex (APC) of the brain in rats or its analog in birds likely houses the in vivo amino acid chemosensor. Because amino acid transporters adapt rapidly to essential amino acid deficiency in several cell models, we hypothesized that activation of electrogenic amino acid transport in APC neurons might contribute to the function of the amino acid sensor. We evaluated transport systems in primary cultures of neurons from the APC, hippocampus and cerebellum, or glia, incubated in complete or threonine-devoid (deficient) medium. After 10 min in deficient medium, uptake of threonine or a system A-selective substrate, methyl amino-isobutyric acid, was increased 60% in APC neurons only (P < 0.05). These results demonstrated upregulation of system A, an electrogenic amino acid-sodium symporter. This depletion-induced activation required sodium, intact intracellular trafficking, and phosphorylation of signal transduction-related kinases. Efflux studies showed that other transporter types were functional in the APC; they appeared to be altered dynamically in threonine-deficient cells in response to rapid increases in system A activity. The present data provided support for the chemical sensitivity of the APC and its role as the brain area housing the indispensable amino acid chemosensor. They also showed a region-specific, phosphorylation-dependent activation of the system A transporter in the brain in response to threonine deficiency.

  10. The role of transport processes in survival of lactic acid bacteria. Energy transduction and multidrug resistance.

    PubMed

    Konings, W N; Lolkema, J S; Bolhuis, H; van Veen, H W; Poolman, B; Driessen, A J

    1997-02-01

    Lactic acid bacteria play an essential role in many food fermentation processes. They are anaerobic organisms which obtain their metabolic energy by substrate phosphorylation. In addition three secondary energy transducing processes can contribute to the generation of a proton motive force: proton/substrate symport as in lactic acid excretion, electrogenic precursor/product exchange as in malolactic and citrolactic fermentation and histidine/histamine exchange, and electrogenic uniport as in malate and citrate uptake in Leuconostoc oenos. In several of these processes additional H+ consumption occurs during metabolism leading to the generation of a pH gradient, internally alkaline. Lactic acid bacteria have also developed multidrug resistance systems. In Lactococcus lactis three toxin excretion systems have been characterized: cationic toxins can be excreted by a toxin/proton antiport system and by an ABC-transporter. This cationic ABC-transporter has surprisingly high structural and functional analogy with the human MDR1-(P-glycoprotein). For anions an ATP-driven ABC-like excretion systems exist.

  11. MATE Transporter-Dependent Export of Hydroxycinnamic Acid Amides[OPEN

    PubMed Central

    Eschen-Lippold, Lennart; Gorzolka, Karin; Matern, Andreas; Marillonnet, Sylvestre; Böttcher, Christoph; Rosahl, Sabine

    2016-01-01

    The ability of Arabidopsis thaliana to successfully prevent colonization by Phytophthora infestans, the causal agent of late blight disease of potato (Solanum tuberosum), depends on multilayered defense responses. To address the role of surface-localized secondary metabolites for entry control, droplets of a P. infestans zoospore suspension, incubated on Arabidopsis leaves, were subjected to untargeted metabolite profiling. The hydroxycinnamic acid amide coumaroylagmatine was among the metabolites secreted into the inoculum. In vitro assays revealed an inhibitory activity of coumaroylagmatine on P. infestans spore germination. Mutant analyses suggested a requirement of the p-coumaroyl-CoA:agmatine N4-p-coumaroyl transferase ACT for the biosynthesis and of the MATE transporter DTX18 for the extracellular accumulation of coumaroylagmatine. The host plant potato is not able to efficiently secrete coumaroylagmatine. This inability is overcome in transgenic potato plants expressing the two Arabidopsis genes ACT and DTX18. These plants secrete agmatine and putrescine conjugates to high levels, indicating that DTX18 is a hydroxycinnamic acid amide transporter with a distinct specificity. The export of hydroxycinnamic acid amides correlates with a decreased ability of P. infestans spores to germinate, suggesting a contribution of secreted antimicrobial compounds to pathogen defense at the leaf surface. PMID:26744218

  12. Enhanced charge transport in highly conducting PEDOT-PSS films after acid treatment

    NASA Astrophysics Data System (ADS)

    Shiva, V. Akshaya; Bhatia, Ravi; Menon, Reghu

    The high electrical conductivity, good stability, high strength, flexibility and good transparency of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS), make it useful for many applications including polymeric anodes for organic photovoltaics, light-emitting diodes, flexible electrodes, supercapacitors, electrochromic devices, field-effect transistors and antistatic-coatings. However, the electrical conductivity of PEDOT-PSS has to be increased significantly for replacement of indium tin oxide (ITO) as the transparent electrode in optoelectronic devices. The as prepared (pristine) PEDOT-PSS film prepared from the PEDOT-PSS aqueous solution usually has conductivity below 1Scm-1, remarkably lower than ITO. Significant conductivity enhancement has been observed on transparent and conductive PEDOT-PSS films after a treatment with inorganic acids. Our study investigates the charge transport in pristine and H2SO4, HNO3, HCl treated PEDOT-PSS films. We have treated the films with various concentrations of acids to probe the effect of the acid treatment on the conduction mechanism. The study includes the measurement of dc and electric field dependent conductivity of films in the temperature range of 4.2K-300K. We have also performed magneto-resistance measurements in the range of 0-5T. An enhancement by a factor of~103 has been observed in the room temperature conductivity. The detailed magneto-transport studies explain the various mechanisms for the conductivity enhancement observed.

  13. Hypertonic stress regulates amino acid transport and cell cycle proteins in chick embryo hepatocytes.

    PubMed

    Bruscalupi, Giovannella; Massimi, Mara; Spagnuolo, Silvana; Fiore, Anna Maria; Leoni, Silvia

    2012-02-01

    Hyperosmotic stress affects cell growth, decreasing cell volume and increasing the uptake of organic osmolytes. However, the sensitivity of embryonic cells to osmotic treatment remains to be established. We have analysed some aspects of cell-cycle control and amino-acid transport in hypertonic conditions during prenatal life. The effects of hyperosmotic stress on amino-acid uptake mediated by system A, (3)H-thymidine incorporation, and regulation of cell-cycle proteins were analysed in chick embryo hepatocytes. Hypertonic stress increased system A activity and caused cell-cycle delay. Effects on amino-acid transport involved p38 kinase activation and new carrier synthesis. Cyclin D1, cdk4 (cyclin-dependent kinase 4) and PCNA (proliferating-cell nuclear antigen) levels decreased, whereas cyclin E, p21 and p53 levels were unchanged. Incorporation of (3)H-leucine indicated decreased synthesis of cyclin D1. In contrast, analysis of mRNA by qRT-PCR (quantitative real-time PCR) showed a net increase of cyclin D1 transcripts, suggesting post-transcriptional regulation. The data show that chick embryo hepatocytes respond to hyperosmotic conditions by arresting cell growth to prevent DNA damage and increasing osmolyte uptake to regulate cell volume, indicating that the adaptive response to environmental stress exists during prenatal life.

  14. Impact of Inhibiting Ileal Apical Versus Basolateral Bile acid Transport on Cholesterol Metabolism and Atherosclerosis in Mice

    PubMed Central

    Dawson, Paul A.

    2015-01-01

    Background Bile acid sequestrants have been used for many years to treat hypercholesterolemia by increasing hepatic conversion of cholesterol to bile acids, thereby inducing hepatic LDL receptor expression and clearance of apoB-containing particles. In order to further understand the underlying molecular mechanisms linking gut-liver signaling and cholesterol homeostasis, mouse models defective in ileal apical membrane bile acid transport (Asbt null) and ileal basolateral membrane bile acid transport (Ostα null) were studied under basal and hypercholesterolemic conditions. Key Messages Hepatic conversion of cholesterol to bile acids is the major pathway for cholesterol catabolism and a major mechanism for cholesterol elimination. Blocking ileal apical membrane bile acid transport (Asbt null mice) increases fecal bile acid excretion, hepatic Cyp7a1 expression and the relative proportion of taurocholate in the bile acid pool, but decreases ileal FGF15 expression, bile acid pool size, and hepatic cholesterol content. In contrast, blocking ileal basolateral membrane bile acid transport (Ostα null mice) increases ileal FGF15 expression, reduces hepatic Cyp7a1 expression, and increases the proportion of tauro-β-muricholic acid in the bile acid pool. In the hypercholesterolemic apoE null background, plasma cholesterol levels and measurements of atherosclerosis were reduced in Asbt/apoE null mice but not in Ostα/apoE null mice. Conclusions Blocking intestinal absorption of bile acids at the apical versus basolateral membrane differentially affects bile acid and cholesterol metabolism, including the development of hypercholesterolemia-associated atherosclerosis. The molecular mechanism likely involves altered regulation of ileal FGF15 expression. PMID:26045273

  15. Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

    USGS Publications Warehouse

    Scott, D.T.; Runkel, R.L.; McKnight, Diane M.; Voelker, B.M.; Kimball, B.A.; Carraway, E.R.

    2003-01-01

    An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O 2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 ??M midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(III), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

  16. Epoxyeicosatrienoic Acids Affect Electrolyte Transport in Renal Tubular Epithelial Cells: Dependence on Cyclooxygenase and Cell Polarity

    PubMed Central

    Nüsing, Rolf M.; Schweer, Horst; Fleming, Ingrid; Zeldin, Darryl C.; Wegmann, Markus

    2007-01-01

    We investigated the effects of epoxyeicosatrienoic acids (EETs) on ion transport in the polarized renal distal tubular cell line, MDCK C7. Of the four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) studied, only apical, but not basolateral, application of 5,6-EET increased short circuit current (Isc) with kinetics similar to those of arachidonic acid. The ion transport was blocked by preincubation with the cyclooxygenase inhibitor indomethacin or with the chloride channel blocker NPPB. Further, both a Cl−-free bath solution and the Ca2+ antagonist verapamil blocked 5,6-EET-induced ion transport. Although the presence of the PGE2 receptors EP2, EP3, and EP4 was demonstrated, apically added PGE2 was ineffective and basolaterally added PGE2 caused a different kinetics in ion transport compared to 5,6-EET. Moreover, PGE2 sythesis in MDCK C7 cells was unaffected by 5,6-EET treatment. GC/MS/MS analysis of cell supernatants revealed the presence of the biologically inactive 5,6-dihydroxy-PGE1 in 5,6-EET-treated cells, but not in control cells. Indomethacin suppressed the formation of 5,6-dihydroxy-PGE1. 5,6-epoxy-PGE1 the precursor of 5,6-dihydroxy-PGE1, caused a similar ion transport as 5,6-EET. Cytochrome P450 enzymes homolog to human CYP2C8, CYP2C9, and CYP2J2 protein were detected immunologically in the MDCK C7 cells. Our findings suggest that 5,6-EET affects Cl-transport in renal distal tubular cells independent of PGE2 but by a mechanism, dependent on its conversion to 5,6-epoxy-PGE1 by cyclooxygenase. We suggest a role for this P450 epoxygenase product in the regulation of electrolyte transport, especially as a saluretic compound acting from the luminal side of tubular cells in the mammalian kidney. PMID:17494091

  17. Transport of Indole-3-Acetic Acid during Gravitropism in Intact Maize Coleoptiles 1

    PubMed Central

    Parker, Karen E.; Briggs, Winslow R.

    1990-01-01

    We have investigated the transport of tritiated indole-3-acetic acid (IAA) in intact, red light-grown maize (Zea mays) coleoptiles during gravitropic induction and the subsequent development of curvature. This auxin is transported down the length of gravistimulated coleoptiles at a rate comparable to that in normal, upright plants. Transport is initially symmetrical across the coleoptile, but between 30 and 40 minutes after plants are turned horizontal a lateral redistribution of the IAA already present in the transport stream occurs. By 60 minutes after the beginning of the gravitropic stimulus, the ratio of tritiated tracer auxin in the lower half with respect to the upper half is approximately 2:1. The redistribution of growth that causes gravitropic curvature follows the IAA redistribution by 5 or 10 minutes at the minimum in most regions of the coleoptile. Immobilization of tracer auxin from the transport stream during gravitropism was not detectable in the most apical 10 millimeters. Previous reports have shown that in intact, red light-grown maize coleoptiles, endogenous auxin is limiting for growth, the tissue is linearly responsive to linearly increasing concentrations of small amounts of added auxin, and the lag time for the stimulation of straight growth by added IAA is approximately 8 or 9 minutes (TI Baskin, M Iino, PB Green, WR Briggs [1985] Plant Cell Environ 8: 595-603; TI Baskin, WR Briggs, M Iino [1986] Plant Physiol 81: 306-309). We conclude that redistribution of IAA in the transport stream occurs in maize coleoptiles during gravitropism, and is sufficient in degree and timing to be the immediate cause of gravitropic curvature. PMID:16667914

  18. Membrane transporters for the special amino acid glutamine: Structure/function relationships and relevance to human health.

    NASA Astrophysics Data System (ADS)

    Pochini, Lorena; Scalise, Mariafrancesca; Galluccio, Michele; Indiveri, Cesare

    2014-08-01

    Glutamine together with glucose is essential for body’s homeostasis. It is the most abundant amino acid and is involved in many biosynthetic, regulatory and energy production processes. Several membrane transporters which differ in transport modes, ensure glutamine homeostasis by coordinating its absorption, reabsorption and delivery to tissues. These transporters belong to different protein families, are redundant and ubiquitous. Their classification, originally based on functional properties, has recently been associated with the SLC nomenclature. Function of glutamine transporters is studied in cells over-expressing the transporters or, more recently in proteoliposomes harboring the proteins extracted from animal tissues or over-expressed in microorganisms. The role of the glutamine transporters is linked to their transport modes and coupling with Na+ and H+. Most transporters share specificity for other neutral or cationic amino acids. Na+-dependent co-transporters efficiently accumulate glutamine while antiporters regulate the pools of glutamine and other amino acids. The most acknowledged glutamine transporters belong to the SLC1, 6, 7 and 38 families. The members involved in the homeostasis are the co-transporters B0AT1 and the SNAT members 1, 2, 3, 5 and 7; the antiporters ASCT2, LAT1 and 2. The last two are associated to the ancillary CD98 protein. Some information on regulation of the glutamine transporters exist, which, however, need to be deepened. No information at all is available on structures, besides some homology models obtained using similar bacterial transporters as templates. Some models of rat and human glutamine transporters highlight very similar structures between the orthologues. Moreover the presence of glycosylation and/or phosphorylation sites located at the extracellular or intracellular faces has been predicted. ASCT2 and LAT1 are over-expressed in several cancers, thus representing potential targets for pharmacological intervention.

  19. Light-Activated Amino Acid Transport Systems in Halobacterium halobium Envelope Vesicles: Role of Chemical and Electrical Gradients

    NASA Technical Reports Server (NTRS)

    MacDonald, Russell E.; Greene, Richard V.; Lanyi, Janos K.

    1977-01-01

    The accumulation of 20 commonly occurring L-amino acids by cell envelope vesicles of Halobacterium halobium, in response to light-induced membrane potential and an artificially created sodium gradient, has been studied. Nineteen of these amino acids are actively accumulated under either or both of these conditions. Glutamate is unique in that its uptake is driven only by a chemical gradient for sodium. Amino acid concentrations at half-maximal uptake rates (Km) and maximal transport rates (V(sub max) have been determined for the uptake of all 19 amino acids. The transport systems have been partially characterized with respect to groups of amino acids transported by common carriers, cation effects, and relative response to the electrical and chemical components of the sodium gradient, the driving forces for uptake. The data presented clearly show that the carrier systems, which are responsible for uptake of individual amino acids, are as variable in their properties as those found in other organisms, i. e., some are highly specific for individual amino acids, some transport several amino acids competitively, some are activated by a chemical gradient of sodium only, and some function also in the complete absence of such a gradient. For all amino acids, Na(+) and K(+) are both required for maximal rate of uptake. The carriers for L-leucine and L-histidine are symmetrical in that these amino acids are transported in both directions across the vesicle membrane. It is suggested that coupling of substrate transport to metabolic energy via transient ionic gradients may be a general phenomenon in procaryotes.

  20. Facilitated transporters mediate net efflux of amino acids to the fetus across the basal membrane of the placental syncytiotrophoblast.

    PubMed

    Cleal, J K; Glazier, J D; Ntani, G; Crozier, S R; Day, P E; Harvey, N C; Robinson, S M; Cooper, C; Godfrey, K M; Hanson, M A; Lewis, R M

    2011-02-15

    Fetal growth depends on placental transfer of amino acids from maternal to fetal blood. The mechanisms of net amino acid efflux across the basal membrane (BM) of the placental syncytiotrophoblast to the fetus, although vital for amino acid transport, are poorly understood. We examined the hypothesis that facilitated diffusion by the amino acid transporters TAT1, LAT3 and LAT4 plays an important role in this process, with possible effects on fetal growth. Amino acid transfer was measured in isolated perfused human placental cotyledons (n = 5 per experiment) using techniques which distinguish between different transport processes. Placental TAT1, LAT3 and LAT4 proteins were measured, and mRNA expression levels (measured using real-time quantitative-PCR) were related to fetal and neonatal anthropometry and dual-energy X-ray absorptiometry measurements of neonatal lean mass in 102 Southampton Women's Survey (SWS) infants. Under conditions preventing transport by amino acid exchangers, all amino acids appearing in the fetal circulation were substrates of TAT1, LAT3 or LAT4. Western blots demonstrated the presence of TAT1, LAT3 and LAT4 in placental BM preparations. Placental TAT1 and LAT3 mRNA expression were positively associated with measures of fetal growth in SWS infants (P < 0.05). We provide evidence that the efflux transporters TAT1, LAT3 and LAT4 are present in the human placental BM, and may play an important role in the net efflux of amino acids to the fetus. Unlike other transporters they can increase fetal amino acid concentrations. Consistent with a role in placental amino acid transfer capacity and fetal growth TAT1 and LAT3 mRNA expression showed positive associations with infant size at birth.

  1. Biodegradation, sorption, and transport of 2,4-dichlorophenoxyacetic acid in saturated and unsaturated soils.

    PubMed Central

    Estrella, M R; Brusseau, M L; Maier, R S; Pepper, I L; Wierenga, P J; Miller, R M

    1993-01-01

    The fate of an organic contaminant in soil depends on many factors, including sorption, biodegradation, and transport. The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model compound to illustrate the impact of these interacting factors on the fate of an organic contaminant. Batch and column experiments performed with a sandy loam soil mixture under saturated and unsaturated conditions were used to determine the effects of sorption and biodegradation on the fate and transport of 2,4-D. Sorption of 2,4-D was found to have a slight but significant effect on transport of 2,4-D under saturated conditions (retardation factor, 1.8) and unsaturated conditions (retardation factor, 3.4). Biodegradation of 2,4-D was extensive under both batch and column conditions and was found to have a significant impact on 2,4-D transport in column experiments. In batch experiments, complete mineralization of 2,4-D (100 mg kg-1) occurred over a 4-day period following a 3-day lag phase under both saturated and unsaturated conditions. The biodegradation rate parameters calculated for batch experiments were found to be significantly different from those estimated for column experiments. PMID:8285717

  2. Structure-dependent effects of pyridine derivatives on mechanisms of intestinal fatty acid uptake: regulation of nicotinic acid receptor and fatty acid transporter expression.

    PubMed

    Riedel, Annett; Lang, Roman; Rohm, Barbara; Rubach, Malte; Hofmann, Thomas; Somoza, Veronika

    2014-07-01

    Pyridines are widely distributed in foods. Nicotinic acid (NA), a carboxylated pyridine derivative, inhibits lipolysis in adipocytes by activation of the orphan NA receptor (HM74A) and is applied to treat hyperlipidemia. However, knowledge on the impact of pyridine derivatives on intestinal lipid metabolism is scarce. This study was performed to identify the structural determinants of pyridines for their effects on fatty acid uptake in enterocyte-like Caco-2 cells and to elucidate the mechanisms of action. The impact of 17 pyridine derivatives on fatty acid uptake was tested. Multiple regression analysis revealed the presence of a methyl group to be the structural determinant at 0.1 mM, whereas at 1 mM, the presence of a carboxylic group and the N-methylation presented further structural characteristics to affect the fatty acid uptake. NA, showing a stimulating effect on FA uptake, and N-methyl-4-phenylpyridinium (MPP), inhibiting FA uptake, were selected for mechanistic studies. Gene expression of the fatty acid transporters CD36, FATP2 and FATP4, and the lipid metabolism regulating transcription factors peroxisome proliferator-activated receptor (PPAR) α and PPARγ was up-regulated upon NA treatment. Caco-2 cells were demonstrated to express the low-affinity NA receptor HM74 of which the gene expression was up-regulated upon NA treatment. We hypothesize that the NA-induced fatty acid uptake might result from NA receptor activation and related intracellular signaling cascades. In contrast, MPP increased transepithelial electrical resistance. We therefore conclude that NA and MPP, both sharing the pyridine motif core, exhibit their contrary effects on intestinal FA uptake by activation of different mechanisms.

  3. Structure-dependent effects of pyridine derivatives on mechanisms of intestinal fatty acid uptake: regulation of nicotinic acid receptor and fatty acid transporter expression.

    PubMed

    Riedel, Annett; Lang, Roman; Rohm, Barbara; Rubach, Malte; Hofmann, Thomas; Somoza, Veronika

    2014-07-01

    Pyridines are widely distributed in foods. Nicotinic acid (NA), a carboxylated pyridine derivative, inhibits lipolysis in adipocytes by activation of the orphan NA receptor (HM74A) and is applied to treat hyperlipidemia. However, knowledge on the impact of pyridine derivatives on intestinal lipid metabolism is scarce. This study was performed to identify the structural determinants of pyridines for their effects on fatty acid uptake in enterocyte-like Caco-2 cells and to elucidate the mechanisms of action. The impact of 17 pyridine derivatives on fatty acid uptake was tested. Multiple regression analysis revealed the presence of a methyl group to be the structural determinant at 0.1 mM, whereas at 1 mM, the presence of a carboxylic group and the N-methylation presented further structural characteristics to affect the fatty acid uptake. NA, showing a stimulating effect on FA uptake, and N-methyl-4-phenylpyridinium (MPP), inhibiting FA uptake, were selected for mechanistic studies. Gene expression of the fatty acid transporters CD36, FATP2 and FATP4, and the lipid metabolism regulating transcription factors peroxisome proliferator-activated receptor (PPAR) α and PPARγ was up-regulated upon NA treatment. Caco-2 cells were demonstrated to express the low-affinity NA receptor HM74 of which the gene expression was up-regulated upon NA treatment. We hypothesize that the NA-induced fatty acid uptake might result from NA receptor activation and related intracellular signaling cascades. In contrast, MPP increased transepithelial electrical resistance. We therefore conclude that NA and MPP, both sharing the pyridine motif core, exhibit their contrary effects on intestinal FA uptake by activation of different mechanisms. PMID:24767308

  4. Design and Evaluation of a Novel Trifluorinated Imaging Agent for Assessment of Bile Acid Transport Using Fluorine Magnetic Resonance Imaging

    PubMed Central

    Vivian, Diana; Cheng, Kunrong; Khurana, Sandeep; Xu, Su; Dawson, Paul A.; Raufman, Jean-Pierre; Polli, James E.

    2014-01-01

    Previously, we developed a trifluorinated bile acid, CA-lys-TFA, with the objective of noninvasively assessing bile acid transport in vivo using 19F magnetic resonance imaging (MRI). CA-lys-TFA was successfully imaged in the mouse gallbladder, but was susceptible to deconjugation in vitro by choloylglycine hydrolase (CGH), a bacterial bile acid deconjugating enzyme found in the terminal ileum and colon. The objective of the present study was to develop a novel trifluorinated bile acid resistant to deconjugation by CGH. CA-sar-TFMA was designed, synthesized, and tested for in vitro transport properties, stability, imaging properties, and its ability to differentially accumulate in the gallbladders of normal mice, compared with mice with known impaired bile acid transport (deficient in the apical sodium-dependent bile acid transporter, ASBT). CA-sar-TFMA was a potent inhibitor and substrate of ASBT and the Na+/taurocholate cotransporting polypeptide. Stability was favorable in all conditions tested, including the presence of CGH. CA-sar-TFMA was successfully imaged and accumulated at 16.1-fold higher concentrations in gallbladders from wild-type mice compared with those from Asbt-deficient mice. Our results support the potential of using MRI with CA-sar-TFMA as a noninvasive method to assess bile acid transport in vivo. PMID:25196788

  5. Transforming growth factor-beta 1 stimulates vascular smooth muscle cell L-proline transport by inducing system A amino acid transporter 2 (SAT2) gene expression.

    PubMed Central

    Ensenat, D; Hassan, S; Reyna, S V; Schafer, A I; Durante, W

    2001-01-01

    Transforming growth factor-beta1 (TGF-beta 1) is a multifunctional cytokine that contributes to arterial remodelling by stimulating vascular smooth muscle cell (SMC) growth and collagen synthesis at sites of vascular injury. Since l-proline is essential for the synthesis of collagen, we examined whether TGF-beta 1 regulates the transcellular transport of l-proline by vascular SMCs. l-Proline uptake by vascular SMCs was primarily sodium-dependent, pH-sensitive, blocked by neutral amino acids and alpha-(methylamino)isobutyric acid, and exhibited trans-inhibition. Treatment of SMCs with TGF-beta 1 stimulated l-proline transport in a concentration- and time-dependent manner. The TGF-beta 1-mediated l-proline uptake was inhibited by cycloheximide or actinomycin D. Kinetic studies indicated that TGF-beta 1-induced l-proline transport was mediated by an increase in transport capacity independent of any changes in the affinity for l-proline. TGF-beta 1 stimulated the expression of system A amino acid transporter 2 (SAT2) mRNA in a time-dependent fashion that paralleled the increase in l-proline transport. Reverse transcriptase PCR failed to detect the presence of SAT1 or amino acid transporter 3 (ATA3) in either untreated or TGF-beta 1-treated SMCs. These results demonstrate that l-proline transport by vascular SMCs is mediated predominantly by the SAT and that TGF-beta 1 stimulates SMC l-proline uptake by inducing the expression of the SAT2 gene. The ability of TGF-beta 1 to induce SAT2 expression may function to provide SMCs with the necessary levels of l-proline required for collagen synthesis and cell growth. PMID:11716780

  6. Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders.

    PubMed

    Nava, Caroline; Rupp, Johanna; Boissel, Jean-Paul; Mignot, Cyril; Rastetter, Agnès; Amiet, Claire; Jacquette, Aurélia; Dupuits, Céline; Bouteiller, Delphine; Keren, Boris; Ruberg, Merle; Faudet, Anne; Doummar, Diane; Philippe, Anne; Périsse, Didier; Laurent, Claudine; Lebrun, Nicolas; Guillemot, Vincent; Chelly, Jamel; Cohen, David; Héron, Delphine; Brice, Alexis; Closs, Ellen I; Depienne, Christel

    2015-12-01

    Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors. PMID:26215737

  7. Evaluating remedial alternatives for an acid mine drainage stream: Application of a reactive transport model

    USGS Publications Warehouse

    Runkel, R.L.; Kimball, B.A.

    2002-01-01

    A reactive transport model based on one-dimensional transport and equilibrium chemistry is applied to synoptic data from an acid mine drainage stream. Model inputs include streamflow estimates based on tracer dilution, inflow chemistry based on synoptic sampling, and equilibrium constants describing acid/base, complexation, precipitation/dissolution, and sorption reactions. The dominant features of observed spatial profiles in pH and metal concentration are reproduced along the 3.5-km study reach by simulating the precipitation of Fe(III) and Al solid phases and the sorption of Cu, As, and Pb onto freshly precipitated iron-(III) oxides. Given this quantitative description of existing conditions, additional simulations are conducted to estimate the streamwater quality that could result from two hypothetical remediation plans. Both remediation plans involve the addition of CaCO3 to raise the pH of a small, acidic inflow from ???2.4 to ???7.0. This pH increase results in a reduced metal load that is routed downstream by the reactive transport model, thereby providing an estimate of post-remediation water quality. The first remediation plan assumes a closed system wherein inflow Fe(II) is not oxidized by the treatment system; under the second remediation plan, an open system is assumed, and Fe(II) is oxidized within the treatment system. Both plans increase instream pH and substantially reduce total and dissolved concentrations of Al, As, Cu, and Fe(II+III) at the terminus of the study reach. Dissolved Pb concentrations are reduced by ???18% under the first remediation plan due to sorption onto iron-(III) oxides within the treatment system and stream channel. In contrast, iron(III) oxides are limiting under the second remediation plan, and removal of dissolved Pb occurs primarily within the treatment system. This limitation results in an increase in dissolved Pb concentrations over existing conditions as additional downstream sources of Pb are not attenuated by

  8. Phytanic acid oxidation: normal activation and transport yet defective alpha-hydroxylation of phytanic acid in peroxisomes from Refsum disease and rhizomelic chondrodysplasia punctata.

    PubMed

    Pahan, K; Khan, M; Singh, I

    1996-05-01

    In humans the oxidation of phytanic acid is a peroxisomal function. To understand the possible mechanisms for the pathognomic accumulation of phytanic acid in plasma and body fluids of Refsum disease (RD) and rhizomelic chondrodysplasia punctata (RCDP), we investigated activities of various steps (activation, transport, and oxidation) in the metabolism of phytanic acid in peroxisomes isolated from cultured skin fibroblasts from control, RD, and RCDP subjects. Activation of phytanic acid was normal in peroxisomes from both RD and RCDP. Transport of phytanic acid or phytanoyl-CoA in the absence or presence of fatty acid activating cofactors (ATP, MgCl2, and CoASH) into peroxisomes isolated from RD and RCDP skin fibroblasts was also similar to that of peroxisomes from control fibroblasts. Defective oxidation of [(2,3)-3H]- or [1-14C]phytanic acid, or [1-14C]phytanoyl-CoA (substrate for the first step of alpha-oxidation) but normal oxidation of [1-14C] alpha-hydroxyphytanic acid (substrate for the second step of the alpha-oxidation pathway) in peroxisomes from RD clearly demonstrates that excessive accumulation of phytanic acid in plasma and body fluids of RD is due to the deficiency of phytanic acid alpha-hydroxylase in peroxisomes. However, in RCDP peroxisomes, in addition to deficient oxidation of [1-14C]phytanic acid or phytanoyl-CoA or [(2,3)-3H]phytanic acid, the oxidation of [1-14C] alpha-hydroxyphytanic acid was also deficient, indicating that in RCDP the activities both of alpha-hydroxylation of phytanic acid and decarboxylation of alpha-hydroxyphytanic acid are deficient. These observations indicate that peroxisomal membrane functions (phytanic acid activation and transport) in phytanic acid metabolism are normal in both RD and RCDP. The defect in RD is in the alpha-hydroxylation of phytanic acid; whereas in RCDP both alpha-hydroxylation of phytanic acid as well as decarboxylation of alpha-hydroxyphytanic acid are deficient.

  9. Location of Transported Auxin in Etiolated Maize Shoots Using 5-Azidoindole-3-Acetic Acid 1

    PubMed Central

    Jones, Alan M.

    1990-01-01

    A study was undertaken using the photoaffinity labeling agent, tritiated 5-azidoindole-3-acetic acid ([3H],5-N3IAA), to identify cells in the etiolated maize (Zea mays L.) shoot which transport auxin. Transport of [3H],5-N3IAA was shown to be polar, inhibited by 2,3,5-triiodobenzoic acid (TIBA) and essentially freely mobile. There was no detectable radiodecomposition of [3H],5-N3IAA within tissue kept in darkness for 4 hours. Shoot tissue which had taken up [3H],5-N3IAA was irradiated with ultraviolet light to covalently fix the photoaffinity labeling agent within cells that contained it at the time of photolysis. Subsequent microautoradiography showed that all cells contained radioactivity; however, the amount of radioactivity varied among different cell types. Epidermal cells contained the most radioactivity per area, approximately twofold more than other cells. Parenchyma cells in the mature stelar region contained the next largest amount and cortical cells, sieve tube cells, tracheary cells, and all cells in the leaf base contained the least amount of the radioactive label. Two observations suggest that the auxin within the epidermal cells is transported in a polar manner: (a) the amount of auxin in the epidermal cells is greatly reduced in the presence of TIBA, and (b) auxin accumulates on the apical side of a wound in the epidermis and is absent on the basal side. While these results indicate that auxin in the epidermis is polarly transported, this tissue cannot be the only pathway since the epidermis is only a small fraction of the shoot volume. The greater than twofold difference between the concentration of auxin in the epidermal and subtending cells demonstrates that physiological differences in the concentration of auxin can occur between adjacent cells. Images Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 PMID:16667572

  10. Charge transport through dicarboxylic-acid-terminated alkanes bound to graphene-gold nanogap electrodes

    NASA Astrophysics Data System (ADS)

    Liu, Longlong; Zhang, Qian; Tao, Shuhui; Zhao, Cezhou; Almutib, Eman; Al-Galiby, Qusiy; Bailey, Steven W. D.; Grace, Iain; Lambert, Colin J.; Du, Jun; Yang, Li

    2016-07-01

    Graphene-based electrodes are attractive for single-molecule electronics due to their high stability and conductivity and reduced screening compared with metals. In this paper, we use the STM-based matrix isolation I(s) method to measure the performance of graphene in single-molecule junctions with one graphene electrode and one gold electrode. By measuring the length dependence of the electrical conductance of dicarboxylic-acid-terminated alkanes, we find that the transport is consistent with phase-coherent tunneling, but with an attenuation factor of βN = 0.69 per methyl unit, which is lower than the value measured for Au-molecule-Au junctions. Comparison with density-functional-theory calculations of electron transport through graphene-molecule-Au junctions and Au-molecule-Au junctions reveals that this difference is due to the difference in Fermi energies of the two types of junction, relative to the frontier orbitals of the molecules. For most molecules, their electrical conductance in graphene-molecule-Au junctions is higher than that in Au-molecule-Au junctions, which suggests that graphene offers superior electrode performance, when utilizing carboxylic acid anchor groups.Graphene-based electrodes are attractive for single-molecule electronics due to their high stability and conductivity and reduced screening compared with metals. In this paper, we use the STM-based matrix isolation I(s) method to measure the performance of graphene in single-molecule junctions with one graphene electrode and one gold electrode. By measuring the length dependence of the electrical conductance of dicarboxylic-acid-terminated alkanes, we find that the transport is consistent with phase-coherent tunneling, but with an attenuation factor of βN = 0.69 per methyl unit, which is lower than the value measured for Au-molecule-Au junctions. Comparison with density-functional-theory calculations of electron transport through graphene-molecule-Au junctions and Au

  11. Essential amino acid transporter Lat4 (Slc43a2) is required for mouse development

    PubMed Central

    Guetg, Adriano; Mariotta, Luca; Bock, Lukas; Herzog, Brigitte; Fingerhut, Ralph; Camargo, Simone M R; Verrey, François

    2015-01-01

    Amino acid (AA) uniporter Lat4 (Slc43a2) mediates facilitated diffusion of branched-chain AAs, methionine and phenylalanine, although its physiological role and subcellular localization are not known. We report that Slc43a2 knockout mice were born at expected Mendelian frequency but displayed an ∼10% intrauterine growth retardation and low amniotic fluid AAs, suggesting defective transplacental transport. Postnatal growth was strongly reduced, with premature death occurring within 9 days such that further investigations were made within 3 days of birth. Lat4 immunofluorescence showed a strong basolateral signal in the small intestine, kidney proximal tubule and thick ascending limb epithelial cells of wild-type but not Slc43a2 null littermates and no signal in liver and skeletal muscle. Experiments using Xenopus laevis oocytes demonstrated that Lat4 functioned as a symmetrical low affinity uniporter with a K0.5 of ∼5 mm for both in- and efflux. Plasma AA concentration was decreased in Slc43a2 null pups, in particular that of non-essential AAs alanine, serine, histidine and proline. Together with an increased level of plasma long chain acylcarnitines and a strong alteration of liver gene expression, this indicates malnutrition. Attempts to rescue pups by decreasing the litter size or by nutrients injected i.p. did not succeed. Radioactively labelled leucine but not lysine given per os accumulated in the small intestine of Slc43a2null pups, suggesting the defective transcellular transport of Lat4 substrates. In summary, Lat4 is a symmetrical uniporter for neutral essential AAs localizing at the basolateral side of (re)absorbing epithelia and is necessary for early nutrition and development. Key points Lat4 (Slc43a2) transports branched-chain amino acids, phenylalanine and methionine, and is expressed in kidney tubule and small intestine epithelial cells. Using a new knockout model as a negative control, it is shown that Lat4 is expressed at the basolateral

  12. Metal transport in a stream polluted by acid mine drainage--The Afon Goch, Anglesey, UK.

    PubMed

    Boult, S; Collins, D N; White, K N; Curtis, C D

    1994-01-01

    Sampling of the Afon Goch over a 14-month period revealed maximum dissolved Fe, Al, Mn, Cu and Zn concentrations of 259, 167, 49, 60 and 42 mg dm(-3), respectively, and pH as low as 2.3, making it one of the most metal- and acid-contaminated streams in the UK. The river produces particulates by precipitation of ferrihydrite, due to the entry of near-neutral tributary waters, under all discharge conditions. Consequently, metal transport in this stream is dominated by processes different from those in less contaminated streams. The stream acts as a sink for contaminants, except under high discharge, when accumulated metals are flushed from the system. The implications of these observations for the monitoring and management of streams polluted by acid mine drainage are discussed. PMID:15091699

  13. Norlittorine and norhyoscyamine identified as products of littorine and hyoscyamine metabolism by (13)C-labeling in Datura innoxia hairy roots.

    PubMed

    Al Balkhi, Mohamad Houssam; Schiltz, Séverine; Lesur, David; Lanoue, Arnaud; Wadouachi, Anne; Boitel-Conti, Michèle

    2012-02-01

    The presence of two compounds, norlittorine and norhyoscyamine, has been reported in leaves and roots of Datura innoxia; however their metabolic origin in the tropane alkaloid pathway has remained unknown. Precise knowledge of this pathway is a necessary pre-requisite to optimize the production of hyoscyamine and scopolamine in D. innoxia hairy root cultures. The exact structure of norlittorine and norhyoscyamine was confirmed by LC-MS/MS and NMR analyses. Isotopic labeling experiments, using [1-(13)C]-phenylalanine, [1'-(13)C]-littorine and [1'-(13)C]-hyoscyamine, combined with elicitor treatments, using methyl jasmonate, coronalon and 1-aminocyclopropane-1-carboxylic acid, were used to investigate the metabolic origin of the N-demethylated tropane alkaloids. The results suggest that norlittorine and norhyoscyamine are induced under stress conditions by conversion of littorine and hyoscyamine. We propose the N-demethylation of tropane alkaloids as a mechanism to detoxify cells in overproducing conditions.

  14. The role of gravity in apical dominance: effects of clinostating on shoot inversion-induced ethylene production, shoot elongation and lateral bud growth

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1987-01-01

    Shoot inversion-induced release of apical dominance in Pharbitis nil is inhibited by rotating the plant at 0.42 revolutions per minute in a vertical plane perpendicular to the axis of rotation of a horizontal clinostat. Clinostating prevented lateral bud outgrowth, apparently by negating the restriction of the shoot elongation via reduction of ethylene production in the inverted shoot. Radial stem expansion was also decreased. Data from experiments with intact tissue and isolated segments indicated that shoot-inversion stimulates ethylene production by increasing the activity of 1-aminocyclopropane-1-carboxylic acid synthase. The results support the hypothesis that shoot inversion-induced release of apical dominance in Pharbitis nil is due to gravity stress and is mediated by ethylene-induced retardation of the elongation of the inverted shoot.

  15. Plant growth-promoting traits of yeasts isolated from the phyllosphere and rhizosphere of Drosera spatulata Lab.

    PubMed

    Fu, Shih-Feng; Sun, Pei-Feng; Lu, Hsueh-Yu; Wei, Jyuan-Yu; Xiao, Hong-Su; Fang, Wei-Ta; Cheng, Bai-You; Chou, Jui-Yu

    2016-03-01

    Microorganisms can promote plant growth through direct and indirect mechanisms. Compared with the use of bacteria and mycorrhizal fungi, the use of yeasts as plant growth-promoting (PGP) agents has not been extensively investigated. In this study, yeast isolates from the phyllosphere and rhizosphere of the medicinally important plant Drosera spatulata Lab. were assessed for their PGP traits. All isolates were tested for indole-3-acetic acid-, ammonia-, and polyamine-producing abilities, calcium phosphate and zinc oxide solubilizing ability, and catalase activity. Furthermore, the activities of siderophore, 1-aminocyclopropane-1-carboxylate deaminase, and fungal cell wall-degrading enzymes were assessed. The antagonistic action of yeasts against pathogenic Glomerella cingulata was evaluated. The cocultivation of Nicotiana benthamiana with yeast isolates enhanced plant growth, indicating a potential yeast-plant interaction. Our study results highlight the potential use of yeasts as plant biofertilizers under controlled and field conditions.

  16. Plant growth-promoting and rhizosphere-competent Acinetobacter rhizosphaerae strain BIHB 723 from the cold deserts of the Himalayas.

    PubMed

    Gulati, Arvind; Vyas, Pratibha; Rahi, Praveen; Kasana, Ramesh Chand

    2009-04-01

    A phosphate-solubilizing bacterial strain BIHB 723 isolated from the rhizosphere of Hippophae rhamnoides was identified as Acinetobacter rhizosphaerae on the basis of phenotypic characteristics, carbon source utilization pattern, fatty acid methyl esters analysis, and 16S rRNA gene sequence. The strain exhibited the plant growth-promoting attributes of inorganic and organic phosphate solubilization, auxin production, 1-aminocyclopropane-1-carboxylate deaminase activity, ammonia generation, and siderophore production. A significant increase in the growth of pea, chickpea, maize, and barley was recorded for inoculations under controlled conditions. Field testing with the pea also showed a significant increment in plant growth and yield. The rifampicin mutant of the bacterial strain effectively colonized the pea rhizosphere without adversely affecting the resident microbial populations. PMID:19137371

  17. Optimatization of transient transformation methods to study gene expression in Musa acuminata (AAA group) cultivar Ambon Lumut

    NASA Astrophysics Data System (ADS)

    Prayuni, Kinasih; Dwivany, Fenny M.

    2015-09-01

    Banana is classified as a climateric fruit, whose ripening is regulated by ethylene. Ethylene is synthesized from ACC (1-aminocyclopropane-1-carboxylic acid) by ACC oxidase enzyme which is encoded by ACO gene. Controling an important gene expression in ethylene biosynthesis pathway has became a target to delay the ripening process. Therefore in the previous study we have designed a MaACO-RNAi construct to control MaACO gene expression. In this research, we study the effectiveness of different transient transformation methods to deliver the construct. Direct injection, with or no vaccum infiltration methods were used to deliver MaACO-RNAi construct. All of the methods succesfully deliver the construct into banana fruits based on RT-PCR result.

  18. Plant growth-promoting traits of yeasts isolated from the phyllosphere and rhizosphere of Drosera spatulata Lab.

    PubMed

    Fu, Shih-Feng; Sun, Pei-Feng; Lu, Hsueh-Yu; Wei, Jyuan-Yu; Xiao, Hong-Su; Fang, Wei-Ta; Cheng, Bai-You; Chou, Jui-Yu

    2016-03-01

    Microorganisms can promote plant growth through direct and indirect mechanisms. Compared with the use of bacteria and mycorrhizal fungi, the use of yeasts as plant growth-promoting (PGP) agents has not been extensively investigated. In this study, yeast isolates from the phyllosphere and rhizosphere of the medicinally important plant Drosera spatulata Lab. were assessed for their PGP traits. All isolates were tested for indole-3-acetic acid-, ammonia-, and polyamine-producing abilities, calcium phosphate and zinc oxide solubilizing ability, and catalase activity. Furthermore, the activities of siderophore, 1-aminocyclopropane-1-carboxylate deaminase, and fungal cell wall-degrading enzymes were assessed. The antagonistic action of yeasts against pathogenic Glomerella cingulata was evaluated. The cocultivation of Nicotiana benthamiana with yeast isolates enhanced plant growth, indicating a potential yeast-plant interaction. Our study results highlight the potential use of yeasts as plant biofertilizers under controlled and field conditions. PMID:26895872

  19. Characterization and Regulation of the Amino Acid Transporter SNAT2 in the Small Intestine of Piglets.

    PubMed

    Li, Guangran; Li, Jianjun; Tan, Bie; Wang, Jing; Kong, Xiangfeng; Guan, Guiping; Li, Fengna; Yin, Yulong

    2015-01-01

    The sodium-dependent neutral amino acid transporter 2 (SNAT2), which has dual transport/receptor functions, is well documented in eukaryotes and some mammalian systems, but has not yet been verified in piglets. The objective of this study was to investigate the characteristics and regulation of SNAT2 in the small intestine of piglets. The 1,521-bp porcine full cDNA sequence of SNAT2 (KC769999) from the small intestine of piglets was cloned. The open reading frame of cDNA encodes 506 deduced amino acid residues with a calculated molecular mass of 56.08 kDa and an isoelectric point (pI) of 7.16. Sequence alignment and phylogenetic analysis revealed that SNAT2 is highly evolutionarily conserved in mammals. SNAT2 mRNA can be detected in the duodenum, jejunum and ileum by real-time quantitative PCR. During the suckling period from days 1 to 21, the duodenum had the highest abundance of SNAT2 mRNA among the three segments of the small intestine. There was a significant decrease in the expression of SNAT2 mRNA in the duodenal and jejunal mucosa and in the expression of SNAT2 protein in the jejunal and ileal mucosa on day 1 after weaning (P < 0.05). Studies with enterocytes in vitro showed that amino acid starvation and supplementation with glutamate, arginine or leucine enhanced, while supplementation with glutamine reduced, SNAT2 mRNA expression (P < 0.05). These results regarding the characteristics and regulation of SNAT2 should help to provide some information to further clarify its roles in the absorption of amino acids and signal transduction in the porcine small intestine.

  20. Reactive transport controls on sandy acid sulfate soils and impacts on shallow groundwater quality

    NASA Astrophysics Data System (ADS)

    Salmon, S. Ursula; Rate, Andrew W.; Rengel, Zed; Appleyard, Steven; Prommer, Henning; Hinz, Christoph

    2014-06-01

    Disturbance or drainage of potential acid sulfate soils (PASS) can result in the release of acidity and degradation of infrastructure, water resources, and the environment. Soil processes affecting shallow groundwater quality have been investigated using a numerical code that integrates (bio)geochemical processes with water, solute, and gas transport. The patterns of severe and persistent acidification (pH < 4) in the sandy, carbonate-depleted podzols of a coastal plain could be reproduced without calibration, based on oxidation of microcrystalline pyrite after groundwater level decrease and/or residual groundwater acidity, due to slow vertical solute transport rates. The rate of acidification was limited by gas phase diffusion of oxygen and hence was sensitive to soil water retention properties and in some cases also to oxygen consumption by organic matter mineralization. Despite diffusion limitation, the rate of oxidation in sandy soils was rapid once pyrite-bearing horizons were exposed, even to a depth of 7.5 m. Groundwater level movement was thus identified as an important control on acidification, as well as the initial pyrite content. Increase in the rate of Fe(II) oxidation lead to slightly lower pH and greater accumulation of Fe(III) phases, but had little effect on the overall amount of pyrite oxidized. Aluminosilicate (kaolinite) dissolution had a small pH-buffering effect but lead to the release of Al and associated acidity. Simulated dewatering scenarios highlighted the potential of the model for risk assessment of (bio)geochemical impacts on soil and groundwater over a range of temporal and spatial scales.

  1. Unusual effects of monocarboxylic acids on the structure and on the transport and mechanical properties of chitosan films.

    PubMed

    Chen, Fei; Gällstedt, Mikael; Olsson, Richard T; Gedde, Ulf W; Hedenqvist, Mikael S

    2015-11-01

    The purpose of this study was to study the transport of monocarboxylic acids in chitosan films, since this is important for understanding and predicting the drying kinetics of chitosan from aqueous solutions. Despite the wealth of data on chitosan films prepared from aqueous monocarboxylic acid solutions, this transport has not been reported. Chitosan films were exposed to formic, acetic, propionic and butyric acid vapours, it was found that the rate of uptake decreased with increasing molecular size. The equilibration time was unexpectedly long, especially for propionic and butyric acid, nine months. A clear two-stage uptake curve was observed for propionic acid. Evidently, the rate of uptake was determined by acid-induced changes in the material. X-ray diffraction and infrared spectroscopy indicated that the structure of the chitosan acetate and buffered chitosan films changed during exposure to acid and during the subsequent drying. The dried films previously exposed to the acid showed less crystalline features than the original material and a novel repeating structure possibly involving acid molecules. The molar mass of the chitosan decreased on exposure to acid but tensile tests revealed that the films were always ductile. The films exposed to acid vapour (propionic and butyric acid) for the longest period of time were insoluble in the size-exclusion chromatography eluent, and they were also the most ductile/extensible of all samples studied.

  2. Sebacina vermifera promotes the growth and fitness of Nicotiana attenuata by inhibiting ethylene signaling.

    PubMed

    Barazani, Oz; von Dahl, Caroline C; Baldwin, Ian T

    2007-06-01

    Sebacina vermifera, a growth-promoting endophytic fungus, significantly increases Nicotiana attenuata's growth but impairs both its herbivore resistance and its accumulation of the costly, jasmonic acid (JA)-regulated defense protein, trypsin proteinase inhibitor (TPI). To determine if the fungi's growth-promoting effects can be attributed to lower TPI-related defense costs, we inoculated transformed N. attenuata plants silenced in their ability to synthesize JA, JA-isoleucine, and TPI by antisense (lipoxygenase 3 [as-lox3] and Thr deaminase [as-td]) and inverted repeat (ir-tpi) expression, and found that inoculation promoted plant growth as in untransformed wild-type plants. Moreover, herbivore-elicited increases in JA and JA-isoleucine concentrations did not differ between inoculated and uninoculated wild-type plants. However, inoculation significantly reduced the morphological effect of 1-aminocyclopropane-1-carboxylic acid on wild-type seedlings in a triple response assay, suggesting that ethylene signaling was impaired. Furthermore, S. vermifera failed to promote the growth of N. attenuata plants transformed to silence ethylene production (1-aminocyclopropane-1-carboxylic acid oxidase [ir-aco]). Inoculating wild-type plants with S. vermifera decreased the ethylene burst elicited by applying Manduca sexta oral secretions to mechanical wounds. Accordingly, oral secretion-elicited transcript levels of the ethylene synthesis genes NaACS3, NaACO1, and NaACO3 in inoculated plants were significantly lower compared to these levels in uninoculated wild-type plants. Inoculation accelerated germination in wild-type seeds; however, uninoculated wild-type seeds germinated as rapidly as inoculated seeds in the presence of the ethylene scrubber KMnO(4). In contrast, neither inoculation nor KMnO(4) exposure influenced the germination of ir-aco seeds. We conclude that S. vermifera increases plant growth by impairing ethylene production independently of JA signaling and TPI

  3. Suppression of Ripening-Associated Gene Expression in Tomato Fruits Subjected to a High CO2 Concentration.

    PubMed Central

    Rothan, C.; Duret, S.; Chevalier, C.; Raymond, P.

    1997-01-01

    High concentrations of CO2 block or delay the ripening of fruits. In this study we investigated the effects of high CO2 on ripening and on the expression of stress- and ripening-inducible genes in cherry tomato (Lycopersicon esculentum Mill.) fruit. Mature-green tomato fruits were submitted to a high CO2 concentration (20%) for 3 d and then transferred to air. These conditions effectively inhibited ripening-associated color changes and ethylene production, and reduced the protein content. No clear-cut effect was observed on the expression of two proteolysis-related genes, encoding polyubiquitin and ubiquitin-conjugating enzyme E2, respectively. Exposure of fruit to high CO2 also resulted in the strong induction of two genes encoding stress-related proteins: a ripening-regulated heat-shock protein and glutamate decarboxylase. Induction of these two genes indicated that high CO2 had a stress effect, most likely through cytosolic acidification. In addition, high CO2 blocked the accumulation of mRNAs for genes involved in the main ripening-related changes: ethylene synthesis (1-aminocyclopropane-1-carboxylic acid synthase and 1-aminocyclopropane-1-carboxylic acid oxidase), color (phytoene synthase), firmness (polygalacturonase), and sugar accumulation (acid invertase). The expression of ripening-specific genes was affected by CO2 regardless of whether their induction was ethylene- or development-dependent. It is proposed that the inhibition of tomato fruit ripening by high CO2 is due, in part, to the suppression of the expression of ripening-associated genes, which is probably related to the stress effect exerted by high CO2. PMID:12223703

  4. Steric hindrance of 2,6-disubstituted benzoic acid derivatives on the uptake via monocarboxylic acid transporters from the apical membranes of Caco-2 cells.

    PubMed

    Tsukagoshi, Kensuke; Kimura, Osamu; Endo, Tetsuya

    2014-05-01

    Benzoic acid is a typical substrate for monocarboxylic acid transporters (MCTs), and easily taken up from the apical membranes of Caco-2 cells by MCTs. However, some benzoic acid derivatives were sparingly taken up by Caco-2 cells. To elucidate the mechanism of lower uptake of the derivatives, we investigated the effect of substitution of benzene ring on the uptake by MCTs using Caco-2 cells. Among the benzoic acid derivatives tested, the uptake of 2,6-disubstituted benzoic acids was markedly lower than that of other benzoic acids. Co-incubation of the 2,6-disubstituted derivatives with benzoic acid did not decrease the uptake of benzoic acid, while co-incubation with other derivatives significantly decreased the uptake of benzoic acid. Kinetic analyses elucidated that the uptake of 2,6-dichlorobenzoic acid and 2,3,6-trichlorobenzoic acid did not involve the carrier-mediated process. The 2,6-disubstitution of benzoic acid may prevent the access of carboxylic acid group to MCTs expressed on the apical membranes of Caco-2 cells. PMID:24861932

  5. Suppression of asymmetric acid efflux and gravitropism in maize roots treated with auxin transport inhibitors of sodium orthovanadate

    NASA Technical Reports Server (NTRS)

    Mulkey, T. J.; Evans, M. L.

    1982-01-01

    In gravitropically stimulated roots of maize (Zea mays L., hybrid WF9 x 38MS), there is more acid efflux on the rapidly growing upper side than on the slowly growing lower side. In light of the Cholodny/Went hypothesis of gravitropism which states that gravitropic curvature results from lateral redistribution of auxin, the effects of auxin transport inhibitors on the development of acid efflux asymmetry and curvature in gravistimulated roots were examined. All the transport inhibitors tested prevented both gravitropism and the development of asymmetric acid efflux in gravistimulated roots. The results indicate that auxin redistribution may cause the asymmetry of acid efflux, a finding consistent with the Cholodny/Went hypothesis of gravitropism. As further evidence that auxin-induced acid efflux asymmetry may mediate gravitropic curvature, sodium orthovanadate, an inhibitor of auxin-induced H+ efflux was found to prevent both gravitropism and the development of asymmetric acid efflux in gravistimulated roots.

  6. Functional reconstitution of the. gamma. -aminobutyric acid transporter from synaptic vesicles using artificial ion gradients

    SciTech Connect

    Hell, J.W.; Edelmann, L.; Hartinger, J.; Jahn, R. )

    1991-12-24

    The {gamma}-aminobutyric acid transporter of rat brain synaptic vesicles was reconstituted in proteoliposomes, and its activity was studied in response to artificially created membrane potentials or proton gradients. Changes of the membrane potential were monitored using the dyes oxonol VI and 3,3{prime}-diisopropylthiodicarbocyanine iodide, and changes of the H{sup +} gradient were followed using acridine orange. An inside positive membrane potential was generated by the creation of an inwardly directed K{sup +} gradient and the subsequent addition of valinomycin. Under these conditions, valinomycin evoked uptake of ({sup 3}H)GABA which was saturable. Similarly, ({sup 3}H)glutamate uptake was stimulated by valinomycin, indicating that both transporters can be driven by the membrane potential. Proton gradients were generated by the incubation of K{sup +}-loaded proteoliposomes in a buffer free of K{sup +} or Na{sup +} ions and the subsequent addition of nigericin. Proton gradients were also generated via the endogenous H{sup +} ATPase by incubation of K{sup +}-loaded proteoliposomes in equimolar K{sup +} buffer in the presence of valinomycin. These proton gradients evoked nonspecific, nonsaturable uptake of GABA and {beta}-alanine but not of glycine in proteoliposomes as well as protein-free liposomes. Therefore, transporter activity was monitored using glycine as an alternative substrate. Proton gradients generated by both methods elicited saturable glycine uptake in proteoliposomes. Together, these data confirm that the vesicular GABA transporter can be energized by both the membrane potential and the pH gradient and show that transport can be achieved by artificial gradients independently of the endogenous proton ATPase.

  7. Potential role of sea spray generation in the atmospheric transport of perfluorocarboxylic acids.

    PubMed

    Webster, Eva; Ellis, David A

    2010-08-01

    The observed environmental concentrations of perfluorooctanoic acid (PFOA) and its conjugate base (PFO) in remote regions such as the Arctic have been primarily ascribed to the atmospheric transport and degradation of fluorotelomer alcohols (FTOHs) and to direct PFO transport in ocean currents. These mechanisms are each capable of only partially explaining observations. Transport within marine aerosols has been proposed and may explain transport over short distances but will contribute little over longer distances. However, PFO(A) has been shown to have a very short half-life in aqueous aerosols and thus sea spray was proposed as a mechanism for the generation of PFOA in the gas phase from PFO in a water body. Using the observed PFO concentrations in oceans of the Northern Hemisphere and estimated spray generation rates, this mechanism is shown to have the potential for contributing large amounts of PFOA to the atmosphere and may therefore contribute significantly to the concentrations observed in remote locations. Specifically, the rate of PFOA release into the gas phase from oceans in the Northern Hemisphere is calculated to be potentially comparable to global stack emissions to the atmosphere. The subsequent potential for atmospheric degradation of PFOA and its global warming potential are considered. Observed isomeric ratios and predicted atmospheric concentrations due to FTOH degradation are used to elucidate the likely relative importance of transport pathways. It is concluded that gas phase PFOA released from oceans may help to explain observed concentrations in remote regions. The model calculations performed in the present study strongly suggest that oceanic aerosol and gas phase field monitoring is of vital importance to obtain a complete understanding of the global dissemination of PFCAs.

  8. Reduced placental amino acid transport in response to maternal nutrient restriction in the baboon.

    PubMed

    Pantham, Priyadarshini; Rosario, Fredrick J; Nijland, Mark; Cheung, Alex; Nathanielsz, Peter W; Powell, Theresa L; Galan, Henry L; Li, Cun; Jansson, Thomas

    2015-10-01

    Intrauterine growth restriction increases the risk of perinatal complications and predisposes the infant to diabetes and cardiovascular disease in later life. Mechanisms by which maternal nutrient restriction (MNR) reduces fetal growth are poorly understood. We hypothesized that MNR decreases placental amino acid (AA) transporter activity, leading to reduced transplacental transfer of AAs. Pregnant baboons were fed either a control (ad libitum, n = 7), or MNR diet (70% of control diet, n = 7) from gestational day (GD) 30. At GD 165 (0.9 gestation), placentas (n = 7 in each group) were collected, and microvillous plasma membrane vesicles (MVM) isolated. MVM system A and system L AA transport was determined in vitro using radiolabeled substrates and rapid filtration techniques. In vivo transplacental AA transport was assessed by infusing nine (13)C- or (2)H-labeled essential AA as a bolus into the maternal circulation (n = 5 control, n = 4 MNR) at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each essential AA was calculated. Fetal and placental weights were significantly reduced in the MNR group compared with controls (P < 0.01). The activity of system A and system L was markedly reduced by 73 and 84%, respectively, in MVM isolated from baboon placentas at GD 165 following MNR (P < 0.01). In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly reduced for leucine, isoleucine, methionine, phenylalanine, threonine, and tryptophan in MNR baboons (P < 0.05). This is the first study to investigate placental AA transport in a nonhuman primate model of MNR. We demonstrate that the downregulation of system A and system L activity in syncytiotrophoblast MVM in MNR leads to decreased transplacental AA transport and, consequently, reduced circulating fetal AA concentrations, a potential mechanism linking maternal undernutrition to reduced fetal growth.

  9. The mRNA expression of amino acid transporters, aminopeptidase, and the di- and tri-peptide transporter PepT1 in the intestine and liver of post-hatch broiler chicks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Amino acid transporter (AAT) proteins are responsible for the movement of amino acids (AA) in and out of cells. Aminopeptidase (APN) cleaves AAs from the N terminus of polypeptides making them available for transport, while PepT1 is a di- and tri- peptide transporter. In the intestine, these prote...

  10. Homology modeling of human γ-butyric acid transporters and the binding of pro-drugs 5-aminolevulinic acid and methyl aminolevulinic acid used in photodynamic therapy.

    PubMed

    Baglo, Yan; Gabrielsen, Mari; Sylte, Ingebrigt; Gederaas, Odrun A

    2013-01-01

    Photodynamic therapy (PDT) is a safe and effective method currently used in the treatment of skin cancer. In ALA-based PDT, 5-aminolevulinic acid (ALA), or ALA esters, are used as pro-drugs to induce the formation of the potent photosensitizer protoporphyrin IX (PpIX). Activation of PpIX by light causes the formation of reactive oxygen species (ROS) and toxic responses. Studies have indicated that ALA and its methyl ester (MAL) are taken up into the cells via γ-butyric acid (GABA) transporters (GATs). Uptake via GATs into peripheral sensory nerve endings may also account for one of the few adverse side effects of ALA-based PDT, namely pain. In the present study, homology models of the four human GAT subtypes were constructed using three x-ray crystal structures of the homologous leucine transporter (LeuT) as templates. Binding of the native substrate GABA and the possible substrates ALA and MAL was investigated by molecular docking of the ligands into the central putative substrate binding sites in the outward-occluded GAT models. Electrostatic potentials (ESPs) of the putative substrate translocation pathway of each subtype were calculated using the outward-open and inward-open homology models. Our results suggested that ALA is a substrate of all four GATs and that MAL is a substrate of GAT-2, GAT-3 and BGT-1. The ESP calculations indicated that differences likely exist in the entry pathway of the transporters (i.e. in outward-open conformations). Such differences may be exploited for development of inhibitors that selectively target specific GAT subtypes and the homology models may hence provide tools for design of therapeutic inhibitors that can be used to reduce ALA-induced pain. PMID:23762315

  11. Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3'-Diiodothyronine across the Plasma Membrane.

    PubMed

    Kinne, Anita; Wittner, Melanie; Wirth, Eva K; Hinz, Katrin M; Schülein, Ralf; Köhrle, Josef; Krause, Gerd

    2015-09-01

    Thyroid hormones are transported across cell membranes by transmembrane transporter proteins, for example by members of the monocarboxylate transporter (MCT) and the L-type amino acid transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid hormones and their metabolites and its role in their transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3'-diiodo-L-thyronine (3,3'-T2) and to some extent also enhanced T3 transport. To gain insight into properties of thyroid hormones and their metabolites transported by Lat2, we inhibited 3,3'-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid strongly competed with 3,3'-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid hormone-specific transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid hormone transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid hormone transporters prefers 3,3'-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid hormone by importing and/or exporting 3,3'-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation. PMID:26601072

  12. Proton transport in triflic acid pentahydrate studied via ab initio path integral molecular dynamics.

    PubMed

    Hayes, Robin L; Paddison, Stephen J; Tuckerman, Mark E

    2011-06-16

    Trifluoromethanesulfonic acid hydrates provide a well-defined system to study proton dissociation and transport in perfluorosulfonic acid membranes, typically used as the electrolyte in hydrogen fuel cells, in the limit of minimal water. The triflic acid pentahydrate crystal (CF(3)SO(3)H·5H(2)O) is sufficiently aqueous that it contains an extended three-dimensional water network. Despite it being extended, however, long-range proton transport along the network is structurally unfavorable and would require considerable rearrangement. Nevertheless, the triflic acid pentahydrate crystal system can provide a clear picture of the preferred locations of local protonic defects in the water network, which provides insights about related structures in the disordered, low-hydration environment of perfluorosulfonic acid membranes. Ab initio molecular dynamics simulations reveal that the proton defect is most likely to transfer to the closest water that has the expected presolvation and only contains water in its first solvation shell. Unlike the tetrahydrate of triflic acid (CF(3)SO(3)H·4H(2)O), there is no evidence of the proton preferentially transferring to a water molecule bridging two of the sulfonate groups. However, this could be an artifact of the crystal structure since the only such water molecule is separated from the proton by long O-O distances. Hydrogen bonding criteria, using the two-dimensional potential of mean force, are extracted. Radial distribution functions, free energy profiles, radii of gyration, and the root-mean-square displacement computed from ab initio path integral molecular dynamics simulations reveal that quantum effects do significantly extend the size of the protonic defect and increase the frequency of proton transfer events by nearly 15%. The calculated IR spectra confirm that the dominant protonic defect mostly exists as an Eigen cation but contains some Zundel ion characteristics. Chain lengths and ring sizes determined from the

  13. Nutritional and Hormonal Regulation of Citrate and Carnitine/Acylcarnitine Transporters: Two Mitochondrial Carriers Involved in Fatty Acid Metabolism

    PubMed Central

    Giudetti, Anna M.; Stanca, Eleonora; Siculella, Luisa; Gnoni, Gabriele V.; Damiano, Fabrizio

    2016-01-01

    The transport of solutes across the inner mitochondrial membrane is catalyzed by a family of nuclear-encoded membrane-embedded proteins called mitochondrial carriers (MCs). The citrate carrier (CiC) and the carnitine/acylcarnitine transporter (CACT) are two members of the MCs family involved in fatty acid metabolism. By conveying acetyl-coenzyme A, in the form of citrate, from the mitochondria to the cytosol, CiC contributes to fatty acid and cholesterol synthesis; CACT allows fatty acid oxidation, transporting cytosolic fatty acids, in the form of acylcarnitines, into the mitochondrial matrix. Fatty acid synthesis and oxidation are inversely regulated so that when fatty acid synthesis is activated, the catabolism of fatty acids is turned-off. Malonyl-CoA, produced by acetyl-coenzyme A carboxylase, a key enzyme of cytosolic fatty acid synthesis, represents a regulator of both metabolic pathways. CiC and CACT activity and expression are regulated by different nutritional and hormonal conditions. Defects in the corresponding genes have been directly linked to various human diseases. This review will assess the current understanding of CiC and CACT regulation; underlining their roles in physio-pathological conditions. Emphasis will be placed on the molecular basis of the regulation of CiC and CACT associated with fatty acid metabolism. PMID:27231907

  14. Structural basis for substrate specificity of an amino acid ABC transporter.

    PubMed

    Yu, Jie; Ge, Jingpeng; Heuveling, Johanna; Schneider, Erwin; Yang, Maojun

    2015-04-21

    ATP-binding cassette (ABC) transporters are ubiquitous integral membrane proteins that translocate a variety of substrates, ranging from ions to macromolecules, either out of or into the cytosol (hence defined as importers or exporters, respectively). It has been demonstrated that ABC exporters and importers function through a common mechanism involving conformational switches between inward-facing and outward-facing states; however, the mechanism underlying their functions, particularly substrate recognition, remains elusive. Here we report the structures of an amino acid ABC importer Art(QN)2 from Thermoanaerobacter tengcongensis composed of homodimers each of the transmembrane domain ArtQ and the nucleotide-binding domain ArtN, either in its apo form or in complex with substrates (Arg, His) and/or ATPs. The structures reveal that the straddling of the TMDs around the twofold axis forms a substrate translocation pathway across the membrane. Interestingly, each TMD has a negatively charged pocket that together create a negatively charged internal tunnel allowing amino acids carrying positively charged groups to pass through. Our structural and functional studies provide a better understanding of how ABC transporters select and translocate their substrates.

  15. Peptide and amino acid transporters are differentially regulated during seed development and germination in faba bean.

    PubMed

    Miranda, Manoela; Borisjuk, Ljudmilla; Tewes, Annegret; Dietrich, Daniela; Rentsch, Doris; Weber, Hans; Wobus, Ulrich

    2003-08-01

    Two peptide transporter (PTR) homologs have been isolated from developing seeds of faba bean (Vicia faba). VfPTR1 was shown to be a functional peptide transporter through complementation of a yeast mutant. Expression patterns of VfPTR1 and VfPTR2 as well as of the amino acid permease VfAAP1 (Miranda et al., 2001) were compared throughout seed development and germination. In developing seeds, the highest levels of VfPTR1 transcripts were reached during midcotyledon development, whereas VfAAP1 transcripts were most abundant during early cotyledon development, before the appearance of storage protein gene transcripts, and were detectable until late cotyledon development. During early germination, VfPTR1 mRNA appeared first in cotyledons and later, during seedling growth, also in axes and roots. Expression of VfPTR2 and VfAAP1 was delayed compared with VfPTR1, and was restricted to the nascent organs of the seedlings. Localization of VfPTR1 transcripts showed that this PTR is temporally and spatially regulated during cotyledon development. In germinating seeds, VfPTR1 mRNA was localized in root hairs and root epidermal cells, suggesting a role in nutrient uptake from the soil. In seedling roots, VfPTR1 was repressed by a dipeptide and by an amino acid, whereas nitrate was without influence.

  16. Relative Rates of Amino Acid Import via the ABC Transporter GlnPQ Determine the Growth Performance of Lactococcus lactis

    PubMed Central

    Fulyani, Faizah; Schuurman-Wolters, Gea K.; Slotboom, Dirk-Jan

    2015-01-01

    ABSTRACT The GlnPQ transporter from Lactococcus lactis has the remarkable feature of having two substrate-binding domains (SBDs) fused to the N terminus of the transmembrane domain (TMD), and thus four SBDs are present in the homodimeric complex. Although X-ray structures and ligand binding data are available for both SBDs, little is known of how different amino acids compete with each other for transport via GlnPQ. Here we show GlnPQ has a broader substrate specificity than previously thought, with the ability to take up asparagine, glutamine, and glutamic acid, albeit via different routes and with different affinities. Asparagine and glutamine compete with each other at the level of binding to SBD1 and SBD2 (with differences in dissociation constant), but at the same time SBD1 and SBD2 compete with each other at the level of interaction with the translocator domain (with differences in affinity constant and rate of transport). Although glutamine transport via SBD1 is outcompeted by physiological concentrations of asparagine, SBD2 ensures high rates of import of the essential amino acid glutamine. Taken together, this study demonstrates that even in the presence of competing asparagine concentrations, GlnPQ has a high capacity to transport glutamine, which matches the high needs of the cell for glutamine and glutamate. IMPORTANCE GlnPQ is an ATP-binding cassette (ABC) transporter for glutamine, glutamic acid, and asparagine. The system is essential in various Gram-positive bacteria, including L. lactis and several pathogens. Here we show how the amino acids compete with each other for binding to the multiple SBDs of GlnPQ and how these SBDs compete with each other for substrate delivery to the transporter. Overall, our results show that GlnPQ has evolved to transport diverse substrates via different paths and to optimally acquire the abundant and essential amino acid glutamine. PMID:26553850

  17. Surfactant control of gas transport and reactions at the surface of sulfuric acid.

    PubMed

    Park, Seong-Chan; Burden, Daniel K; Nathanson, Gilbert M

    2009-02-17

    Aerosol particles in the atmosphere are tiny chemical reactors that catalyze numerous reactions, including the conversion of benign gases into ozone-destroying ones. In the lower stratosphere, these particles are often supercooled mixtures of water and sulfuric acid. The different species present at the surface of these droplets (H(2)O, H(3)O(+), HSO(4)(-), H(2)SO(4), and SO(4)(2-)) stand at the "gas-liquid frontier"; as the first to be struck by impinging molecules, these species provide the initial environment for solvation and reaction. Furthermore, aerosol particles may contain a wide range of organic molecules, some of which migrate to the surface and coat the droplet. How do ambient gases dissolve in the droplet if it is coated with an organic layer? At one extreme, monolayer films of insoluble, long-chain alcohols can dramatically reduce gas transport, packing so tightly at the surface of water that they impede water evaporation by factors of 10,000 or more. Shorter chain surfactants are expected to pack less tightly, but we wondered whether these incomplete monolayers also block gas transport and whether this system could serve as a model for understanding the surfaces of atmospheric aerosol particles. To address these questions, our research focuses on small, soluble surfactants such as butanol and hexanol dissolved in supercooled sulfuric acid. These amphiphilic molecules spontaneously segregate to the surface and coat the acid but only to a degree. Gas-liquid scattering experiments reveal that these porous films behave in surprisingly diverse ways: they can impose a barrier (to N(2)O(5) hydrolysis), be "invisible" (to water evaporation), or even enhance gas uptake (of HCl). The transition from obstacle to catalyst can be traced to specific interactions between the surfactant and each gas. For example, the hydrolysis of N(2)O(5) may be impeded because of its large size and because alcohol molecules that straddle the interface limit contact between N(2)O(5

  18. Surfactant control of gas transport and reactions at the surface of sulfuric acid.

    PubMed

    Park, Seong-Chan; Burden, Daniel K; Nathanson, Gilbert M

    2009-02-17

    Aerosol particles in the atmosphere are tiny chemical reactors that catalyze numerous reactions, including the conversion of benign gases into ozone-destroying ones. In the lower stratosphere, these particles are often supercooled mixtures of water and sulfuric acid. The different species present at the surface of these droplets (H(2)O, H(3)O(+), HSO(4)(-), H(2)SO(4), and SO(4)(2-)) stand at the "gas-liquid frontier"; as the first to be struck by impinging molecules, these species provide the initial environment for solvation and reaction. Furthermore, aerosol particles may contain a wide range of organic molecules, some of which migrate to the surface and coat the droplet. How do ambient gases dissolve in the droplet if it is coated with an organic layer? At one extreme, monolayer films of insoluble, long-chain alcohols can dramatically reduce gas transport, packing so tightly at the surface of water that they impede water evaporation by factors of 10,000 or more. Shorter chain surfactants are expected to pack less tightly, but we wondered whether these incomplete monolayers also block gas transport and whether this system could serve as a model for understanding the surfaces of atmospheric aerosol particles. To address these questions, our research focuses on small, soluble surfactants such as butanol and hexanol dissolved in supercooled sulfuric acid. These amphiphilic molecules spontaneously segregate to the surface and coat the acid but only to a degree. Gas-liquid scattering experiments reveal that these porous films behave in surprisingly diverse ways: they can impose a barrier (to N(2)O(5) hydrolysis), be "invisible" (to water evaporation), or even enhance gas uptake (of HCl). The transition from obstacle to catalyst can be traced to specific interactions between the surfactant and each gas. For example, the hydrolysis of N(2)O(5) may be impeded because of its large size and because alcohol molecules that straddle the interface limit contact between N(2)O(5

  19. Investigating Mass Transport Limitations on Xylan Hydrolysis During Dilute Acid Pretreatment of Poplar

    SciTech Connect

    Mittal, Ashutosh; Pilath, Heid M.; Parent, Yves; Chatterjee, Siddharth G.; Donohoe, Bryon S.; Yarbrough, John M.; Himmel, Michael E.; Nimlos, Mark R.; Johnson, David K.

    2014-04-28

    Mass transport limitations could be an impediment to achieving high sugar yields during biomass pretreatment and thus be a critical factor in the economics of biofuels production. The objective of this work was to study the mass transfer restrictions imposed by the structure of biomass on the hydrolysis of xylan during dilute acid pretreatment of biomass. Mass transfer effects were studied by pretreating poplar wood at particle sizes ranging from 10 micrometers to 10 mm. This work showed a significant reduction in the rate of xylan hydrolysis in poplar when compared to the intrinsic rate of hydrolysis for isolated xylan that is possible in the absence of mass transfer. In poplar samples we observed no significant difference in the rates of xylan hydrolysis over more than two orders of magnitude in particle size. It appears that no additional mass transport restrictions are introduced by increasing particle size from 10 micrometers to 10 mm. This work suggests that the rates of xylan hydrolysis in biomass particles are limited primarily by the diffusion of hydrolysis products out of plant cell walls. A mathematical description is presented to describe the kinetics of xylan hydrolysis that includes transport of the hydrolysis products through biomass into the bulk solution. The modeling results show that the effective diffusion coefficient of the hydrolysis products in the cell wall is several orders of magnitude smaller than typical values in other applications signifying the role of plant cell walls in offering resistance to diffusion of the hydrolysis products.

  20. Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

    USGS Publications Warehouse

    Coupe, R.H.; Kalkhoff, S.J.; Capel, P.D.; Gregoire, C.

    2012-01-01

    Background: Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. Results: Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. Conclusions: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil. ?? 2011 Society of Chemical Industry.

  1. Expression, solubilisation, and purification of a functional CMP-sialic acid transporter in Pichia pastoris.

    PubMed

    Maggioni, Andrea; Hadley, Barbara; von Itzstein, Mark; Tiralongo, Joe

    2014-09-01

    Membrane proteins, including solute transporters play crucial roles in cellular function and have been implicated in a variety of important diseases, and as such are considered important targets for drug development. Currently the drug discovery process is heavily reliant on the structural and functional information discerned from high-resolution crystal structures. However, membrane protein structure determination is notoriously difficult, due in part to challenges faced in their expression, solubilisation and purification. The CMP-sialic acid transporter (CST) is considered to be an attractive target for drug discovery. CST inhibition reduces cancer cell sialylation and decreases the metastatic potential of cancer cells and to date, no crystal structure of the CST, or any other nucleotide sugar transporter exists. Here we describe the optimised conditions for expression in Pichia pastoris, solubilisation using n-nonyl β-d-maltopyranoside (NM) and single step purification of a functional CST. Importantly we show that despite being able to solubilise and purify the CST using a number of different detergents, only NM was able to maintain CST functionality.

  2. Experimental lead poisoning and intestinal transport of glucose, amino acids, and sodium.

    PubMed

    Wapnir, R A; Exeni, R A; McVicar, M; Lipshitz, F

    1977-03-01

    Juvenile rats fed a diet containing 1% lead acetate for 7 weeks, in addition to an impaired growth rate and renal function derangements, suffered malabsorption of glucose and certain amino acids, as assessed by an in vivo perfusion technique. The reduction in glucose absorption ranged between 10% and 31% when the carbohydrate was pumped in concentrations of 2-80 mM. This alteration was compatible with a noncompetitive type of transport inhibition. The intestinal absorption of glycine, lysine, and phenylalanine were, respectively, decreased 22, 18, and 15% when these amino acids were present at 1 mM levels. Sodium transport was severely reduced (57.6 +/- 17.9 (SEM) vs. 124.2 +/- 17.4 muEq/min-cm) and intestinal mucosa (Na+-K+)-ATPase was concomitantly lower in the lead-intoxicated rats (186.4 +/- 19.0 vs 268.4 +/- 29.8 nmol P/min-mg protein). However, this enzyme was not altered in liver and kidney. Furthermore, intestinal mucosa fructose-1,6-diphosphatase, succinic dehydrogenase, pyruvate kinase, and tryptophan hydroxylase were not different in experimental and control animals. These studies substantiate the presence of functional and biochemical abnormalities in the intestinal mucosa of young rats when fed substantial amounts of a soluble lead salt. It is, therefore, reasonable to accept the possibility that physiologic damage occurs in tissues directly subjected to high and persistent levels of a toxic agents, as it occurs in other organs, underscoring the parallelism between transport mechanisms at the renal and intestinal levels.

  3. Omega 3 fatty acids promote macrophage reverse cholesterol transport in hamster fed high fat diet.

    PubMed

    Kasbi Chadli, Fatima; Nazih, Hassane; Krempf, Michel; Nguyen, Patrick; Ouguerram, Khadija

    2013-01-01

    The aim of this study was to investigate macrophage reverse cholesterol transport (RCT) in hamster, a CETP-expressing species, fed omega 3 fatty acids (ω3PUFA) supplemented high fat diet (HFD). Three groups of hamsters (n = 6/group) were studied for 20 weeks: 1) control diet: Control, 2) HFD group: HF and 3) HFD group supplemented with ω3PUFA (EPA and DHA): HFω3. In vivo macrophage-to-feces RCT was assessed after an intraperitoneal injection of (3)H-cholesterol-labelled hamster primary macrophages. Compared to Control, HF presented significant (p<0.05) increase in body weight, plasma TG (p<0.01) and cholesterol (p<0.001) with an increase in VLDL TG and in VLDL and LDL cholesterol (p<0.001). Compared to HF, HFω3 presented significant decrease in body weight. HFω3 showed less plasma TG (p<0.001) and cholesterol (p<0.001) related to a decrease in VLDL TG and HDL cholesterol respectively and higher LCAT activity (p<0.05) compared to HF. HFω3 showed a higher fecal bile acid excretion (p<0.05) compared to Control and HF groups and higher fecal cholesterol excretion (p<0.05) compared to HF. This increase was related to higher gene expression of ABCG5, ABCA1 and SR-B1 in HFω3 compared to Control and HF groups (<0.05) and in ABCG1 and CYP7A1 compared to HF group (p<0.05). A higher plasma efflux capacity was also measured in HFω3 using (3)H- cholesterol labeled Fu5AH cells. In conclusion, EPA and DHA supplementation improved macrophage to feces reverse cholesterol transport in hamster fed HFD. This change was related to the higher cholesterol and fecal bile acids excretion and to the activation of major genes involved in RCT. PMID:23613796

  4. Homologue gene of bile acid transporters ntcp, asbt, and ost-alpha in rainbow trout Oncorhynchus mykiss: tissue expression, effect of fasting, and response to bile acid administration.

    PubMed

    Murashita, Koji; Yoshiura, Yasutoshi; Chisada, Shin-Ichi; Furuita, Hirofumi; Sugita, Tsuyoshi; Matsunari, Hiroyuki; Iwashita, Yasuro; Yamamoto, Takeshi

    2014-04-01

    Bile acid transporters belonging to the SLC10A protein family, Na+ taurocholate cotransporting polypeptide (NTCP or SLC10A1), apical sodium-dependent bile salt transporter (ASBT or SLC10A2), and organic solute transporter alpha (Ost-alpha) have been known to play critical roles in the enterohepatic circulation of bile acids in mammals. In this study, ntcp, asbt, and ost-alpha-1/-2 cDNA were cloned, their tissue distributions were characterized, and the effects of fasting and bile acid administration on their expression were examined in rainbow trout Oncorhynchus mykiss. The structural characteristics of Ntcp, Asbt, and Ost-alpha were well conserved in trout, and three-dimensional structure analysis showed that Ntcp and Asbt were similar to each other. Tissue distribution analysis revealed that trout asbt was primarily expressed in the hindgut, while ntcp expression occurred in the brain, and ost-alpha-1/-2 was mainly expressed in the liver or ovary. Although asbt and ost-alpha-1 mRNA levels in the gut increased in response to fasting for 4 days, ost-alpha-1 expression in the liver decreased. Similarly, bile acid administration increased asbt and ost-alpha-1 expression levels in the gut, while those of ntcp and ost-alpha-2 in the liver decreased. These results suggested that the genes asbt, ntcp, and ost-alpha are involved in bile acid transport in rainbow trout.

  5. Screening of Streptococcus pneumoniae ABC transporter mutants demonstrates that LivJHMGF, a branched-chain amino acid ABC transporter, is necessary for disease pathogenesis.

    PubMed

    Basavanna, Shilpa; Khandavilli, Suneeta; Yuste, Jose; Cohen, Jonathan M; Hosie, Arthur H F; Webb, Alexander J; Thomas, Gavin H; Brown, Jeremy S

    2009-08-01

    Bacterial ABC transporters are an important class of transmembrane transporters that have a wide variety of substrates and are important for the virulence of several bacterial pathogens, including Streptococcus pneumoniae. However, many S. pneumoniae ABC transporters have yet to be investigated for their role in virulence. Using insertional duplication mutagenesis mutants, we investigated the effects on virulence and in vitro growth of disruption of 9 S. pneumoniae ABC transporters. Several were partially attenuated in virulence compared to the wild-type parental strain in mouse models of infection. For one ABC transporter, required for full virulence and termed LivJHMGF due to its similarity to branched-chain amino acid (BCAA) transporters, a deletion mutant (DeltalivHMGF) was constructed to investigate its phenotype in more detail. When tested by competitive infection, the DeltalivHMGF strain had reduced virulence in models of both pneumonia and septicemia but was fully virulent when tested using noncompetitive experiments. The DeltalivHMGF strain had no detectable growth defect in defined or complete laboratory media. Recombinant LivJ, the substrate binding component of the LivJHMGF, was shown by both radioactive binding experiments and tryptophan fluorescence spectroscopy to specifically bind to leucine, isoleucine, and valine, confirming that the LivJHMGF substrates are BCAAs. These data demonstrate a previously unsuspected role for BCAA transport during infection for S. pneumoniae and provide more evidence that functioning ABC transporters are required for the full virulence of bacterial pathogens. PMID:19470745

  6. Up-regulation of gamma-aminobutyric acid transporter I mediates ethanol sensitivity in mice.

    PubMed

    Hu, J-H; Ma, Y-H; Yang, N; Mei, Z-T; Zhang, M-H; Fei, J; Guo, L-H

    2004-01-01

    Ethanol is among the most widely abused drugs in the world. Chronic ethanol consumption leads to ethanol tolerance and addiction, and impairs learning and memory. Na+/Cl- dependent GABA transporters play an important role in controlling the concentration of GABA in the synaptic cleft, and thus they control the intensity and duration of synaptic transmission of GABA. It has been suggested that GABAergic system is involved in ethanol consumption, tolerance and addiction, because chronic ethanol consumption alters the expression of GABAA receptors and drugs on GABA receptors affect ethanol actions. The results of the present study reveal that that activity of GABA transporters in mouse brain after 15-min acute ethanol injection or after chronic ethanol consumption is increased. Moreover, mice pre-injected with a competitive or a noncompetitive antagonist of gamma-aminobutyric acid transporter subtype 1 (GAT1) showed high sensitivity to the sedative/hypnotic effects of ethanol. In contrast, transgenic mice overexpressing GAT1 displayed low sensitivity to ethanol, as shown by the righting reflex test. Mice overexpressing GAT1 survived a lethal dose of ethanol (9 g/kg, i.p.) longer, maintained locomotor activity longer after a sub-lethal dose (1.75 g/kg, i.p.) and exhibited a higher median lethal dose than wild-type littermates. These results suggest that GAT1 plays an important role in sensitivity to ethanol, and might be a therapeutic target for alcoholism prevention and treatment. Acute and chronic ethanol administration resulted in the increase of GABA transporter function. Use of GAT1 selective inhibitors and GAT1 overexpressing mice thus demonstrate that GAT1 should be an important protein mediating sensitivity to ethanol in mice.

  7. Plasmalemmal and Vesicular γ-Aminobutyric Acid Transporter Expression in the Developing Mouse Retina

    PubMed Central

    GUO, CHENYING; STELLA, SALVATORE L.; HIRANO, ARLENE A.; BRECHA, NICHOLAS C.

    2009-01-01

    Plasmalemmal and vesicular γ-aminobutyric acid (GABA) transporters influence neurotransmission by regulating high-affinity GABA uptake and GABA release into the synaptic cleft and extracellular space. Postnatal expression of the plasmalemmal GABA transporter-1 (GAT-1), GAT-3, and the vesicular GABA/glycine transporter (VGAT) were evaluated in the developing mouse retina by using immunohistochemistry with affinity-purified antibodies. Weak transporter immunoreactivity was observed in the inner retina at postnatal day 0 (P0). GAT-1 immunostaining at P0 and at older ages was in amacrine and displaced amacrine cells in the inner nuclear layer (INL) and ganglion cell layer (GCL), respectively, and in their processes in the inner plexiform layer (IPL). At P10, weak GAT-1 immunostaining was in Müller cell processes. GAT-3 immunostaining at P0 and older ages was in amacrine cells and their processes, as well as in Müller cells and their processes that extended radially across the retina. At P10, Müller cell somata were observed in the middle of the INL. VGAT immunostaining was present at P0 and older ages in amacrine cells in the INL as well as processes in the IPL. At P5, weak VGAT immunostaining was also observed in horizontal cell somata and processes. By P15, the GAT and VGAT immunostaining patterns appear similar to the adult immunostaining patterns; they reached adult levels by about P20. These findings demonstrate that GABA uptake and release are initially established in the inner retina during the first postnatal week and that these systems subsequently mature in the outer retina during the second postnatal week. PMID:18975268

  8. Transport in Porous Media of Poly(Acrylic Acid) Coated Ferrihydrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Jaffe, P. R.; Xiang, A.; Koel, B. E.

    2012-12-01

    Augmentation of soils with iron to enhance biological processes such as uranium reduction via iron reducing bacteria, e.g., Geobacter sp., might be achieved via the injection of iron nanoparticles into the subsurface. The challenge is to make these nanoparticles transportable in the subsurface while not affecting the iron bioavailability. Poorly crystallized 2-line ferrihydrite iron oxide nanoparticles were synthesized and coated with different amounts of poly(acrylic acid) polymers (Na-PAA6K or Na-PAA140K). Analyses were then performed on these particles, including sorption/desorption of the polymer onto the iron nanoparticles, particle size, zeta potential, transport in sand and soil columns, and bioavailabity of the Fe(III) in the absence and presence of the coating to iron reducing organisms. Results showed that at pH values of environmental relevance, the zeta potential of the particles varied from about 3 mV (pH=8.2) for the non-coated particles to about -30 mV for the particles coated with the polymers to their highest sorption capacity. The coated particle diameter was shown to be in the range of 200 nm. Column transport experiments showed that for the highest polymer coating the nanoparticle breakthrough was virtually identical to that of bromide, while significant filtration was observed for particles with an intermediate coating, and complete particle removal via filtration was observed for the non-coated particles. These results held for sand as well as for soil, which had been previously characterized, from a field site at Rifle, CO. Bioavailability experiments showed no difference in the iron reduction rate between the untreated and treated nanoparticles. These results show that it is possible to manufacture iron nanoparticles to enhance biological iron reduction, and that the transport properties of these treated particles is tunable so that a desired retention in the porous medium can be achieved.

  9. Accumulation of ascorbate by endocrine-regulated and glucose-sensitive transport of dehydroascorbic acid in luteinized rat ovarian cells.

    PubMed

    Kodaman, P H; Aten, R F; Behrman, H R

    1998-02-01

    The corpus luteum is notable for very high levels of ascorbic acid. In luteal cells, ascorbic acid depletion occurs as a result of consumption during radical scavenging, inhibition of ascorbic acid uptake, and stimulation of its secretion. Oxidation of ascorbic acid generates dehydroascorbic acid (DHAA). Although levels of DHAA in blood are much lower than those of ascorbic acid, DHAA serves as the major transportable form of ascorbate for certain cell types. The aim of the present studies was to investigate whether DHAA transport is a potential mechanism for conserving ascorbic acid in the corpus luteum. DHAA uptake by rat luteal cells precultured for 24 h was linear for up to 30 min. Kinetics studies showed that uptake of DHAA was a concentration-dependent and saturable process with an estimated Michaelis constant (Km) of 830 microM and a maximum velocity (Vmax) of 700 pmol/min per 10(6) cells, a rate 50 times that of ascorbate transport. More than 90% of DHAA was reduced to ascorbic acid within 2 h of cellular uptake. DHAA uptake was energy- and microfilament-dependent, as transport was inhibited by 2,4-dinitrophenol (1 mM) and cytochalasin B (10 microM). Menadione (50 microM), an intracellular generator of reactive oxygen species, also markedly reduced DHAA uptake. In contrast to ascorbic acid transport, DHAA uptake was potently inhibited by glucose and phloretin, an inhibitor of glucose transporters, with IC50s of approximately 5 mM and 10 microM, respectively. DHAA uptake appears to occur via an insulin-insensitive transporter, as insulin (10 nM) had no effect on uptake. However, 24-h preincubation with insulin-like growth factor (IGF)-I dose-dependently (10-100 ng/ml) stimulated DHAA uptake; similar concentrations of IGF-II had no effect. The secretion of radioactivity by cells preloaded with radiolabeled DHAA was significantly increased by prostaglandin F2alpha (1 microM). The ability of luteal cells to transport DHAA in a regulated manner may serve to

  10. The Fate and Transport of Glyphosate and its Degradation Product, Aminomethylphosphonic Acid (AMPA), in Water

    NASA Astrophysics Data System (ADS)

    Scribner, E.; Meyer, M. T.

    2006-05-01

    Since 2001, the U.S. Geological Survey (USGS) has investigated the fate and transport of glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), in surface water, and more recently in tile-drain flow, soil, and wet deposition. According to U.S. Environmental Protection Agency sources, glyphosate is among the world's most widely used herbicides. In 2004, glyphosate usage estimates indicated that between 103 and 113 million pounds were applied annually to crops in the United States. The use of glyphosate over a wide geographic area suggests that this herbicide might be a potential concern for air, water, and soil quality as well as measured in high concentrations in streams; therefore, it is important to monitor its fate and transport in ground-water/surface-water systems. National, regional, and field-scale studies conducted by the USGS National Water-Quality Assessment and Toxic Substance Hydrology Programs have studied the fate and transport of glyphosate in overland flow, tile- drain flow, surface water, soil, and wet-deposition samples. The samples were analyzed for glyphosate and AMPA by using derivatization and online solid-phase extraction with liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS methods developed by the USGS Organic Geochemistry Research Laboratory in Lawrence, Kansas. During spring, summer, and fall 2002 runoff periods in 50 Midwestern streams, glyphosate was detected at or above the 0.10 micrograms per liter detection limit in 35, 41, and 31 percent of samples, respectively. AMPA was detected in 53, 82, and 75 percent of samples, respectively. Results of 128 samples from a field study showed that glyphosate was transported as a narrow high- concentration pulse during the first period of runoff after application and that the concentration of glyphosate in runoff was greater than the concentration of AMPA. In tile-drain flow, glyphosate and AMPA were transported in a broad low-concentration pulse during these same

  11. Coffee polyphenol caffeic acid but not chlorogenic acid increases 5'AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscle.

    PubMed

    Tsuda, Satoshi; Egawa, Tatsuro; Ma, Xiao; Oshima, Rieko; Kurogi, Eriko; Hayashi, Tatsuya

    2012-11-01

    Chlorogenic acid is an ester of caffeic and quinic acids, and is one of the most widely consumed polyphenols because it is abundant in foods, especially coffee. We explored whether chlorogenic acid and its metabolite, caffeic acid, act directly on skeletal muscle to stimulate 5'-adenosine monophosphate-activated protein kinase (AMPK). Incubation of rat epitrochlearis muscles with Krebs buffer containing caffeic acid (≥0.1 mM, ≥30 min) but not chlorogenic acid increased the phosphorylation of AMPKα Thr(172), an essential step for kinase activation, and acetyl CoA carboxylase Ser(79), a downstream target of AMPK, in a dose- and time-dependent manner. Analysis of isoform-specific AMPK activity revealed that AMPKα2 activity increased significantly, whereas AMPKα1 activity did not change. This enzyme activation was associated with a reduction in phosphocreatine content and an increased rate of 3-O-methyl-d-glucose transport activity in the absence of insulin. These results suggest that caffeic acid but not chlorogenic acid acutely stimulates skeletal muscle AMPK activity and insulin-independent glucose transport with a reduction of the intracellular energy status. PMID:22227267

  12. Parallel transport of an organic acid by solid-phase and macropore diffusion in a weakly basic ion exchanger

    SciTech Connect

    Yoshida, Hiroyuki; Takatsuji; Wataru

    2000-04-01

    The parallel transport of an organic acid by solid-phase and macropore diffusion within a porous ion exchanger was studied by measuring equilibrium isotherms and uptake curves for adsorption of acetic acid and lactic acid on a weakly basic ion exchanger, DIAION WA30. Experimental adsorption isotherms were correlated by the Langmuir equation. The Langmuir equilibrium constant of acetic acid was close to that of lactic acid, and the saturation capacity of acetic acid was about 84% that of lactic acid. Intraparticle effective diffusivity D{sub eff} was determined using the homogeneous Fickian diffusion model. The value of D{sub eff} for acetic acid was about 1.5 times lactic acid. Because D{sub eff} increased with linearly increasing bulk phase concentration C{sub 0}, D{sub eff} was separated to the solid-phase diffusivity D{sub s} and the macropore diffusivity D{sub P} by applying the parallel diffusion model. The model agreed well with the experimental curves. The values of D{sub S} and D{sub P} for acetic acid were about 2 and 1.5 times those of lactic acid, respectively. The acetic acid and the lactic acid may be separated by the difference of the diffusion rates.

  13. The arabidopsis ISR1 locus controlling rhizobacteria-mediated induced systemic resistance is involved in ethylene signaling.

    PubMed

    Ton, J; Davison, S; Van Wees, S C; Van Loon, L; Pieterse, C M

    2001-02-01

    In Arabidopsis, the rhizobacterial strain Pseudomonas fluorescens WCS417r triggers an induced systemic resistance (ISR) response that is effective against different types of pathogens. The ISR signaling pathway functions independent of salicylic acid, but requires responsiveness to jasmonate (JA) and ethylene. Using the genetic variability of ISR inducibility between Arabidopsis accessions, we recently identified a locus (ISR1) on chromosome III that is involved in ISR signaling. Accessions RLD and Wassilewskija (Ws) are recessive at the ISR1 locus and are, therefore, unable to develop ISR. Here we investigated whether the ISR1 locus is involved in JA or ethylene signaling. Compared with the ISR-inducible accession Columbia (Col), accessions RLD and Ws were not affected in JA-induced inhibition of root growth and expression of the JA-responsive gene Atvsp, suggesting that the ISR1 locus is not involved in JA signaling. However, RLD and Ws showed an affected expression of the triple response and a reduced expression of the ethylene responsive genes Hel and Pdf1.2 after exogenous application of the ethylene precursor 1-aminocyclopropane-1-carboxylate. Moreover, in contrast to Col, RLD and Ws did not develop resistance against P. syringae pv. tomato DC3000 after treatment of the leaves with 1-aminocyclopropane-1-carboxylate. Analysis of the F(2) and F(3) progeny of a cross between Col (ISR1/ISR1) and RLD (isr1/isr1) revealed that reduced sensitivity to ethylene cosegregates with the recessive alleles of the ISR1 locus. These results suggest that the ISR1 locus encodes a component of the ethylene response, which is required for the expression of rhizobacteria-mediated ISR.

  14. PtAAP11, a high affinity amino acid transporter specifically expressed in differentiating xylem cells of poplar.

    PubMed

    Couturier, Jérémy; de Faÿ, Elisabeth; Fitz, Michael; Wipf, Daniel; Blaudez, Damien; Chalot, Michel

    2010-06-01

    Amino acids are the currency of nitrogen exchange between source and sink tissues in plants and constitute a major source of the components used for cellular growth and differentiation. The characterization of a new amino acid transporter belonging to the amino acid permease (AAP) family, AAP11, expressed in the perennial species Populus trichocarpa is reported here. PtAAP11 expression analysis was performed by semi-quantitative RT-PCR and GUS activity after poplar transformation. PtAAP11 function was studied in detail by heterologous expression in yeast. The poplar genome contains 14 putative AAPs which is quite similar to other species analysed except Arabidopsis. PtAAP11 was mostly expressed in differentiating xylem cells in different organs. Functional characterization demonstrated that PtAAP11 was a high affinity amino acid transporter, more particularly for proline. Compared with other plant amino acid transporters, PtAAP11 represents a novel high-affinity system for proline. Thus, the functional characterization and expression studies suggest that PtAAP11 may play a major role in xylogenesis by providing proline required for xylem cell wall proteins. The present study provides important information highlighting the role of a specific amino acid transporter in xylogenesis in poplar.

  15. K(+)- and HCO3(-)-dependent acid-base transport in squid giant axons. I. Base efflux

    PubMed Central

    1995-01-01

    We used microelectrodes to monitor the recovery (i.e., decrease) of intracellular pH (pHi) after using internal dialysis to load squid giant axons with alkali to pHi values of 7.7, 8.0, or 8.3. The dialysis fluid (DF) contained 400 mM K+ but was free of Na+ and Cl-. The artificial seawater (ASW) lacked Na+, K+, and Cl-, thereby eliminating effects of known acid-base transporters on pHi. Under these conditions, halting dialysis unmasked a slow pHi decrease caused at least in part by acid-base transport we refer to as "base efflux." Replacing K+ in the DF with either NMDG+ or TEA+ significantly reduced base efflux and made membrane voltage (Vm) more positive. Base efflux in K(+)-dialyzed axons was stimulated by decreasing the pH of the ASW (pHo) from 8 to 7, implicating transport of acid or base. Although postdialysis acidifications also occurred in axons in which we replaced the K+ in the DF with Li+, Na+, Rb+, or Cs+, only with Rb+ was base efflux stimulated by low pHo. Thus, the base effluxes supported by K+ and Rb+ appear to be unrelated mechanistically to those observed with Li+, Na+, or Cs+. The combination of 437 mM K+ and 12 mM HCO3- in the ASW, which eliminates the gradient favoring a hypothetical K+/HCO3- efflux, blocked pHi recovery in K(+)-dialyzed axons. However, the pHi recovery was not blocked by the combination of 437 mM Na+, veratridine, and CO2/HCO3- in the ASW, a treatment that inverts electrochemical gradients for H+ and HCO3- and would favor passive H+ and HCO3- fluxes that would have alkalinized the axon. Similarly, the recovery was not blocked by K+ alone or HCO3- alone in the ASW, nor was it inhibited by the K-H pump blocker Sch28080 nor by the Na-H exchange inhibitors amiloride and hexamethyleneamiloride. Our data suggest that a major component of base efflux in alkali-loaded axons cannot be explained by metabolism, a H+ or HCO3- conductance, or by a K-H exchanger. However, this component could be mediated by a novel K/HCO3- cotransporter

  16. Fatty Acid Transport Protein-2 inhibitor Grassofermata/CB5 protects cells against lipid accumulation and toxicity

    PubMed Central

    Saini, Nipun; Black, Paul N.; Montefusco, David; DiRusso, Concetta C.

    2015-01-01

    The inhibition of the fatty acid uptake into non-adipose tissues provides an attractive target for prevention of lipotoxicity leading to obesity-associated non-alcoholic fatty liver disease and type 2 diabetes. Fatty acid transport proteins (FATPs) are bifunctional proteins involved in the uptake and activation of fatty acids by esterification with coenzyme A. Here we characterize Grassofermata/CB5, previously identified as a fatty acid uptake inhibitor directed against HsFATP2. The compound was effective in inhibiting the uptake of fatty acids in the low micro-molar range (IC50 8–11μM) and prevented palmitate-mediated lipid accumulation and cell death in cell lines that are models for intestines, liver, muscle and pancreas. In adipocytes, uptake inhibition was less effective (IC50 58μM). Inhibition was specific for long chain fatty acids and was ineffective toward medium chain fatty acids, which are transported by diffusion. Kinetic analysis of Grassofermata-dependent FA transport inhibition verified a non-competitive mechanism. By comparison with Grassofermata, several atypical antipsychotic drugs previously implicated as inhibitors of FA uptake were ineffectual. In mice Grassofermata decreased absorption of 13C-oleate demonstrating its potential as a therapeutic agent. PMID:26284975

  17. Determination of thermodynamic and transport parameters of naphthenic acids and organic process chemicals in oil sand tailings pond water.

    PubMed

    Wang, Xiaomeng; Robinson, Lisa; Wen, Qing; Kasperski, Kim L

    2013-07-01

    Oil sand tailings pond water contains naphthenic acids and process chemicals (e.g., alkyl sulphates, quaternary ammonium compounds, and alkylphenol ethoxylates). These chemicals are toxic and can seep through the foundation of the tailings pond to the subsurface, potentially affecting the quality of groundwater. As a result, it is important to measure the thermodynamic and transport parameters of these chemicals in order to study the transport behavior of contaminants through the foundation as well as underground. In this study, batch adsorption studies and column experiments were performed. It was found that the transport parameters of these chemicals are related to their molecular structures and other properties. The computer program (CXTFIT) was used to further evaluate the transport process in the column experiments. The results from this study show that the transport of naphthenic acids in a glass column is an equilibrium process while the transport of process chemicals seems to be a non-equilibrium process. At the end of this paper we present a real-world case study in which the transport of the contaminants through the foundation of an external tailings pond is calculated using the lab-measured data. The results show that long-term groundwater monitoring of contaminant transport at the oil sand mining site may be necessary to avoid chemicals from reaching any nearby receptors. PMID:23736740

  18. Determination of thermodynamic and transport parameters of naphthenic acids and organic process chemicals in oil sand tailings pond water.

    PubMed

    Wang, Xiaomeng; Robinson, Lisa; Wen, Qing; Kasperski, Kim L

    2013-07-01

    Oil sand tailings pond water contains naphthenic acids and process chemicals (e.g., alkyl sulphates, quaternary ammonium compounds, and alkylphenol ethoxylates). These chemicals are toxic and can seep through the foundation of the tailings pond to the subsurface, potentially affecting the quality of groundwater. As a result, it is important to measure the thermodynamic and transport parameters of these chemicals in order to study the transport behavior of contaminants through the foundation as well as underground. In this study, batch adsorption studies and column experiments were performed. It was found that the transport parameters of these chemicals are related to their molecular structures and other properties. The computer program (CXTFIT) was used to further evaluate the transport process in the column experiments. The results from this study show that the transport of naphthenic acids in a glass column is an equilibrium process while the transport of process chemicals seems to be a non-equilibrium process. At the end of this paper we present a real-world case study in which the transport of the contaminants through the foundation of an external tailings pond is calculated using the lab-measured data. The results show that long-term groundwater monitoring of contaminant transport at the oil sand mining site may be necessary to avoid chemicals from reaching any nearby receptors.

  19. Drosophila Fatty Acid Transport Protein Regulates Rhodopsin-1 Metabolism and Is Required for Photoreceptor Neuron Survival

    PubMed Central

    Dourlen, Pierre; Bertin, Benjamin; Chatelain, Gilles; Robin, Marion; Napoletano, Francesco; Roux, Michel J.; Mollereau, Bertrand

    2012-01-01

    Tight regulation of the visual response is essential for photoreceptor function and survival. Visual response dysregulation often leads to photoreceptor cell degeneration, but the causes of such cell death are not well understood. In this study, we investigated a fatty acid transport protein (fatp) null mutation that caused adult-onset and progressive photoreceptor cell death. Consistent with fatp having a role in the retina, we showed that fatp is expressed in adult photoreceptors and accessory cells and that its re-expression in photoreceptors rescued photoreceptor viability in fatp mutants. The visual response in young fatp-mutant flies was abnormal with elevated electroretinogram amplitudes associated with high levels of Rhodopsin-1 (Rh1). Reducing Rh1 levels in rh1 mutants or depriving flies of vitamin A rescued photoreceptor cell death in fatp mutant flies. Our results indicate that fatp promotes photoreceptor survival by regulating Rh1 abundance. PMID:22844251

  20. Vesicular γ-Aminobutyric Acid Transporter Expression in Amacrine and Horizontal Cells

    PubMed Central

    Cueva, Juan G.; Haverkamp, Silke; Reimer, Richard J.; Edwards, Robert; Wässle, Heinz; Brecha, Nicholas C.

    2010-01-01

    The vesicular γ-aminobutyric acid (GABA) transporter (VGAT), which transports the inhibitory amino acid transmitters GABA and glycine, is localized to synaptic vesicles in axon terminals. The localization of VGAT immunoreactivity to mouse and rat retina was evaluated with light and electron microscopy by using well-characterized VGAT antibodies. Specific VGAT immunoreactivity was localized to numerous varicose processes in all laminae of the inner plexiform layer (IPL) and to the outer plexiform layer (OPL). Amacrine cell somata characterized by weak VGAT immunoreactivity in the cytoplasm were located in the ganglion cell layer and proximal inner nuclear layer (INL) adjacent to the IPL. In rat retina, VGAT-immunoreactive cell bodies also contained GABA, glycine, or parvalbumin (PV) immunoreactivity, suggesting vesicular uptake of GABA or glycine by these cells. A few varicose VGAT-immunoreactive processes entered the OPL from the IPL. VGAT immunoreactivity in the OPL was predominantly localized to horizontal cell processes. VGAT and calcium binding protein-28K immunoreactivities (CaBP; a marker for horizontal cells) were colocalized in processes and terminals distributed to the OPL. Furthermore, VGAT immunoreactivity overlapped or was immediately adjacent to postsynaptic density-95 (PSD-95) immunoreactivity, which is prominent in photoreceptor terminals. Preem-bedding immunoelectron microscopy of mouse and rat retinae showed that VGAT immunoreactivity was localized to horizontal cell processes and their terminals. Immunoreactivity was distributed throughout the cytoplasm of the horizontal cell processes. Taken together, these findings demonstrate VGAT immunoreactivity in both amacrine and horizontal cell processes, suggesting these cells contain vesicles that accumulate GABA and glycine, possibly for vesicular release. PMID:11920703

  1. TNF-α stimulates System A amino acid transport in primary human trophoblast cells mediated by p38 MAPK signaling.

    PubMed

    Aye, Irving L M H; Jansson, Thomas; Powell, Theresa L

    2015-10-01

    Maternal obesity and gestational diabetes mellitus (GDM) increase the risk of delivering infants that are large for gestational age with greater adiposity, who are prone to the development of metabolic disease in childhood and beyond. These maternal conditions are also associated with increased levels of the proinflammatory cytokine TNF-α in maternal tissues and the placenta. Recent evidence suggests that changes in placental amino acid transport contribute to altered fetal growth. TNF-α was previously shown to stimulate System A amino acid transport in primary human trophoblasts (PHTs), however the molecular mechanisms remain unknown. In this study, we tested the hypothesis that TNF-α regulates amino acid uptake in cultured PHTs by a mitogen-activated protein kinase (MAPK)-dependent mechanism. Treatment of PHTs with TNF-α significantly increased System A amino acid transport, as well as Erk and p38 MAPK signaling. Pharmacological antagonism of p38, but not Erk MAPK activity, inhibited TNF-α stimulated System A activity. Silencing of p38 MAPK using siRNA transfections prevented TNF-α stimulated System A transport in PHTs. TNF-α significantly increased the protein expression of System A transporters SNAT1 and SNAT2, but did not affect their mRNA expression. The effects of TNF-α on SNAT1 and SNAT2 protein expression were reversed by p38 MAPK siRNA silencing. In conclusion, TNF-α regulates System A activity through increased SNAT1 and SNAT2 transporter protein expression in PHTs. These findings suggest that p38 MAPK may represent a critical mechanistic link between elevated proinflammatory cytokines and increased placental amino acid transport in obese and GDM pregnancies associated with fetal overgrowth.

  2. TNF-α stimulates System A amino acid transport in primary human trophoblast cells mediated by p38 MAPK signaling.

    PubMed

    Aye, Irving L M H; Jansson, Thomas; Powell, Theresa L

    2015-10-01

    Maternal obesity and gestational diabetes mellitus (GDM) increase the risk of delivering infants that are large for gestational age with greater adiposity, who are prone to the development of metabolic disease in childhood and beyond. These maternal conditions are also associated with increased levels of the proinflammatory cytokine TNF-α in maternal tissues and the placenta. Recent evidence suggests that changes in placental amino acid transport contribute to altered fetal growth. TNF-α was previously shown to stimulate System A amino acid transport in primary human trophoblasts (PHTs), however the molecular mechanisms remain unknown. In this study, we tested the hypothesis that TNF-α regulates amino acid uptake in cultured PHTs by a mitogen-activated protein kinase (MAPK)-dependent mechanism. Treatment of PHTs with TNF-α significantly increased System A amino acid transport, as well as Erk and p38 MAPK signaling. Pharmacological antagonism of p38, but not Erk MAPK activity, inhibited TNF-α stimulated System A activity. Silencing of p38 MAPK using siRNA transfections prevented TNF-α stimulated System A transport in PHTs. TNF-α significantly increased the protein expression of System A transporters SNAT1 and SNAT2, but did not affect their mRNA expression. The effects of TNF-α on SNAT1 and SNAT2 protein expression were reversed by p38 MAPK siRNA silencing. In conclusion, TNF-α regulates System A activity through increased SNAT1 and SNAT2 transporter protein expression in PHTs. These findings suggest that p38 MAPK may represent a critical mechanistic link between elevated proinflammatory cytokines and increased placental amino acid transport in obese and GDM pregnancies associated with fetal overgrowth. PMID:26508738

  3. Highly conserved asparagine 82 controls the interaction of Na+ with the sodium-coupled neutral amino acid transporter SNAT2.

    PubMed

    Zhang, Zhou; Gameiro, Armanda; Grewer, Christof

    2008-05-01

    The neutral amino acid transporter 2 (SNAT2), which belongs to the SLC38 family of solute transporters, couples the transport of amino acid to the cotransport of one Na(+) ion into the cell. Several polar amino acids are highly conserved within the SLC38 family. Here, we mutated three of these conserved amino acids, Asn(82) in the predicted transmembrane domain 1 (TMD1), Tyr(337) in TMD7, and Arg(374) in TMD8; and we studied the functional consequences of these modifications. The mutation of N82A virtually eliminated the alanine-induced transport current, as well as amino acid uptake by SNAT2. In contrast, the mutations Y337A and R374Q did not abolish amino acid transport. The K(m) of SNAT2 for its interaction with Na(+), K(Na(+)), was dramatically reduced by the N82A mutation, whereas the more conservative mutation N82S resulted in a K(Na(+)) that was in between SNAT2(N82A) and SNAT2(WT). These results were interpreted as a reduction of Na(+) affinity caused by the Asn(82) mutations, suggesting that these mutations interfere with the interaction of SNAT2 with the sodium ion. As a consequence of this dramatic reduction in Na(+) affinity, the apparent K(m) of SNAT2(N82A) for alanine was increased 27-fold compared with that of SNAT2(WT). Our results demonstrate a direct or indirect involvement of Asn(82) in Na(+) coordination by SNAT2. Therefore, we predict that TMD1 is crucial for the function of SLC38 transporters and that of related families.

  4. Effect of acid stress on sodium transport by isolated skins and on osmotic permeability of intact frogs

    SciTech Connect

    Fromm, P.O.

    1981-08-01

    The experiments reported here were designed to determine the effects of increased external hydrogen ion concentrations on the ion transport capability of isolated frog skins measured as short-circuit current and to determine the nature of the interaction of hydrogen ions to sodium transport. Results from a study of the effects of acid exposure on the osmotic permeability of intact frogs are also reported.

  5. Sex-dependent activity of the spinal excitatory amino acid transporter: Role of estrous cycle.

    PubMed

    Sajjad, Jahangir; Felice, Valeria D; Golubeva, Anna V; Cryan, John F; O'Mahony, Siobhain M

    2016-10-01

    Females are more likely to experience visceral pain than males, yet mechanisms underlying this sex bias are not fully elucidated. Moreover, pain sensitivity can change throughout the menstrual cycle. Alterations in the glutamatergic system have been implicated in several pain-disorders; however, whether these are sex-dependent is unclear. Thus, we aimed to investigate sex differences in the spinal cord glutamate uptake and how it varies across the estrous cycle. The activity of the glutamate transporters, excitatory amino acid transporters (EAATs) was assessed using an ex vivo aspartate radioactive uptake assay in the lumbosacral spinal cord in Sprague-Dawley male and female rats. The gene expression of EAATs, glutamate receptor subunits NR1 and NR2B and the estrogen receptors ERα & ERβ in the spinal cord were also analyzed. EAAT activity was lower in females, particularly during the estrus phase, and this was the only cycle stage that was responsive to the pharmacological effects of the EAATs activator riluzole. Interestingly, EAAT1 mRNA expression was lower in high-estrogen and high-ERα states compared to diestrus in females. We conclude that the Spinal EAAT activity in females is different to that in males, and varies across the estrous cycle. Furthermore, the expression levels of estrogen receptors also showed a cycle-dependent pattern that may affect EAATs function and expression. PMID:27471194

  6. Biphasic effects of ethanol and sodium oleate on synaptic transport of aspartic acid

    SciTech Connect

    Foley, T.; Rhoads, D.E.

    1987-05-01

    The authors have examined the effects of ethanol and sodium oleate on the transport of aspartic acid (ASP) by nerve-ending preparations from rat cerebral cortex. Physiologically relevant ethanol concentrations of up to 100mM stimulated ASP uptake while concentrations greater than 200mM caused inhibition. A similar biphasic effect was observed with oleate stimulating ASP uptake at 0.1 to 1..mu..M and inhibiting ASP uptake at concentrations greater than 1..mu..M. Maximum stimulation was observed at 0.1..mu..M oleate and at 50mM ethanol. In contrast, when synaptosomes were prepared from rats that had been exposed for 2-3 weeks to 10% ethanol in their drinking water, higher concentrations of ethanol and oleate were required to obtain comparable stimulation of ASP uptake. These biphasic effects on ASP transport can be interpreted in terms of physicochemical alterations in the synaptic membranes, with from alcohol-exposed rats showing tolerance to these fluidizing effects.

  7. Recent Advance in the Relationship between Excitatory Amino Acid Transporters and Parkinson's Disease

    PubMed Central

    Zhang, Yunlong; Tan, Feng; Xu, Pingyi; Qu, Shaogang

    2016-01-01

    Parkinson's disease (PD) is the most common movement disorder disease in the elderly and is characterized by degeneration of dopamine neurons and formation of Lewy bodies. Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). If glutamate is not removed promptly in the synaptic cleft, it will excessively stimulate the glutamate receptors and induce excitotoxic effects on the CNS. With lack of extracellular enzyme to decompose glutamate, glutamate uptake in the synaptic cleft is mainly achieved by the excitatory amino acid transporters (EAATs, also known as high-affinity glutamate transporters). Current studies have confirmed that decreased expression and function of EAATs appear in PD animal models. Moreover, single unilateral administration of EAATs inhibitor in the substantia nigra mimics several PD features and this is a solid evidence supporting that decreased EAATs contribute to the process of PD. Drugs or treatments promoting the expression and function of EAATs are shown to attenuate dopamine neurons death in the substantia nigra and striatum, ameliorate the behavior disorder, and improve cognitive abilities in PD animal models. EAATs are potential effective drug targets in treatment of PD and thus study of relationship between EAATs and PD has predominant medical significance currently. PMID:26981287

  8. Expression Profile of Cationic Amino Acid Transporters in Rats with Endotoxin-Induced Uveitis

    PubMed Central

    Chang, Shu-Wen; Lee, Yi-An; Kao, Tzu-Yun

    2016-01-01

    Purpose. The transcellular arginine transportation via cationic amino acid transporter (CAT) is the rate-limiting step in nitric oxide (NO) synthesis, which is crucial in intraocular inflammation. In this study, CAT isoforms and inducible nitric oxide synthase (iNOS) expression was investigated in endotoxin-induced uveitis (EIU). Methods. EIU was induced in Lewis rats by lipopolysaccharide (LPS) injection. In the treatment group, the rats were injected intraperitoneally with the proteasome inhibitor bortezomib before EIU induction. After 24 hours, leukocyte quantification, NO measurement of the aqueous humor, and histopathological examination were evaluated. The expression of CAT isoforms and iNOS was determined by reverse transcription-polymerase chain reaction, western blotting, and immunofluorescence staining. Nuclear factor-kappa B (NF-κB) binding activity was evaluated by electrophoretic mobility shift assay. The mouse macrophage cell line RAW 264.7 was used to validate the in vivo findings. Results. LPS significantly stimulated iNOS, CAT-2A, and CAT-2B mRNA and protein expression but did not affect CAT-1 in EIU rats and RAW 264.7 cells. Bortezomib attenuated inflammation and inhibited iNOS, CAT-2A, and CAT-2B expression through NF-κB inhibition. Conclusions. CAT-2 and iNOS, but not CAT-1, are specifically involved in EIU. NF-κB is essential in the induction of CAT-2 and iNOS in EIU. PMID:27413255

  9. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…

  10. Transport and fate of acid rains out of North America. Final report, April 14, 1982-April 13, 1983

    SciTech Connect

    Knap, A.H.

    1983-06-01

    A program to determine the transport of acid rain has been undertaken at Bermuda. The results indicate that precipitation at Bermuda is acidified to a pH of 4.8 over a one-year period with a seasonal component of greater acidity (pH 4.4) corresponding to back trajectories of the North American air mass. A detailed study of the composition of Bermuda rainwater compared to a North American coastal site has been carried out as well as a shipboard collection program between eastern North America and Bermuda. The results indicate that the strong acid acidity is due to long-range transport of the North American air mass.

  11. The expression of excitatory amino acid transporter 2 (EAAT2) in forensic autopsy cases.

    PubMed

    Ikematsu, K; Tsuda, R; Orihara, Y; Nakasono, I

    2001-04-15

    Glutamate is the major excitatory neurotransmitter and the greater part of this amino acid is removed from the synaptic cleft by excitatory amino acid transporter 2 (EAAT2) located on perisynaptic astrocytes. Recently, it was reported that the EAAT2 protein content changed in rats following forebrain ischemia and administration of methamphetamine. We planned to demonstrate the immunohistochemical distribution of EAAT2 in the human brain and discuss the significance of its pathophysiological roles. Thirty-two cases were used from forensic autopsies. The tissues were sampled from the cerebral cortex, striatum and hippocampus. The distribution of EAAT2 was difficult to identify in cases of electrical fatalities. However, continuous and extensive staining of EAAT2 was observed in cases of death from hypothermia. In almost all asphyxia death, we were able to observe a weak stain of EAAT2. In case of solvent abuse, EAAT2 staining was continuous and extensive as in the cases of hypothermia, and patchy negative zones were mixed. This study clearly showed the differences in EAAT2 localization according to the cause of death. These findings suggested that the differences in EAAT2 staining depended on the cause and course (pathophysiological conditions) of death.

  12. Intestinal-fatty acid binding protein and lipid transport in human intestinal epithelial cells

    SciTech Connect

    Montoudis, Alain; Delvin, Edgard; Menard, Daniel

    2006-01-06

    Intestinal-fatty acid binding protein (I-FABP) is a 14-15 kDa cytoplasmic molecule highly expressed in the enterocyte. Although different functions have been proposed for various FABP family members, the specific function of I-FABP in human intestine remains unclear. Here, we studied the role of I-FABP in molecularly modified normal human intestinal epithelial cells (HIEC-6). cDNA transfection resulted in 90-fold I-FABP overexpression compared to cells treated with empty pQCXIP vector. The high-resolution immunogold technique revealed labeling mainly in the cytosol and confirmed the marked phenotype abundance of I-FABP in cDNA transfected cells. I-FABP overexpression was not associated with alterations in cell proliferation and viability. Studies using these transfected cells cultured with [{sup 14}C]oleic acid did not reveal higher efficiency in de novo synthesis or secretion of triglycerides, phospholipids, and cholesteryl esters compared to cells treated with empty pQCXIP vector only. Similarly, the incubation with [{sup 35}S]methionine did not disclose a superiority in the biogenesis of apolipoproteins (apo) A-I, A-IV, B-48, and B-100. Finally, cells transfected with I-FABP did not exhibit an increased production of chylomicrons, VLDL, LDL, and HDL. Our observations establish that I-FABP overexpression in normal HIEC-6 is not related to cell proliferation, lipid esterification, apo synthesis, and lipoprotein assembly, and, therefore, exclude its role in intestinal fat transport.

  13. Transport of plasma free fatty acids and triglycerides in man: a theoretical analysis

    PubMed Central

    Shames, David M.; Frank, Arthur; Steinberg, Daniel; Berman, Mones

    1970-01-01

    Three different multicompartmental models of free fatty acid (FFA) and very low density lipoprotein triglyceride fatty acid (VLDL-TGFA) transport in man are formulated from plasma FFA and VLDL-TGFA tracee and tracer data collected over a 24 hr interval after the injection of palmitate-14C. All modeling and data fitting were performed on a digital computer using the SAAM program. Structural differences in the three models relate to the position of the slowly turning over compartment required to generate the late portion of the plasma VLDL-TGFA tracer data. The positions of this slow compartment are along the hepatic pathway from FFA to VLDL-TGFA (model A) or in the distribution system of VLDL-TGFA (model B) or in the distribution system of FFA (model C). Although all three models are equally consistent with our experimental data and are supported by observations of others, each reveals inconsistency with some data obtained from the literature. Consequently, a combination model of FFA-TGFA transport, incorporating properties of models A, B, and C would be more consistent with all available data. Experiments that would help to determine the quantitative significance of each of the slow compartments in the combination model are suggested. Several other models suggesting recycling of plasma VLDL-TGFA through the plasma FFA pool, kinetic heterogencity of the plasma VLDL-TGFA pool, and contamination of plasma VLDL-TGFA radioactivity with low density lipoprotein (LDL) TGFA radioactivity were tested. The first model does not explain the late portion of the plasma VLDL-TGFA tracer data. The second and third models, while consistent with our tracee and tracer data, have steady-state implications with respect to the extent of kinetic heterogeneity and size of the LDL-TGFA contaminant that make them unlikely. Assumptions underlying other investigator's models of FFA and TGFA transport in man are reviewed within the logical framework of our models. Quantitative differences among

  14. Deletion of the amino acid transporter Slc6a14 suppresses tumour growth in spontaneous mouse models of breast cancer.

    PubMed

    Babu, Ellappan; Bhutia, Yangzom D; Ramachandran, Sabarish; Gnanaprakasam, Jaya P; Prasad, Puttur D; Thangaraju, Muthusamy; Ganapathy, Vadivel

    2015-07-01

    SLC6A14 mediates Na(+)/Cl(-)-coupled concentrative uptake of a broad-spectrum of amino acids. It is expressed at low levels in many tissues but up-regulated in certain cancers. Pharmacological blockade of SLC6A14 causes amino acid starvation in estrogen receptor positive (ER+) breast cancer cells and suppresses their proliferation in vitro and in vivo. In the present study, we interrogated the role of this transporter in breast cancer by deleting Slc6a14 in mice and monitoring the consequences of this deletion in models of spontaneous breast cancer (Polyoma middle T oncogene-transgenic mouse and mouse mammary tumour virus promoter-Neu-transgenic mouse). Slc6a14-knockout mice are viable, fertile and phenotypically normal. The plasma amino acids were similar in wild-type and knockout mice and there were no major compensatory changes in the expression of other amino acid transporter mRNAs. There was also no change in mammary gland development in the knockout mouse. However, when crossed with PyMT-Tg mice or MMTV/Neu (mouse mammary tumour virus promoter-Neu)-Tg mice, the development and progression of breast cancer were markedly decreased on Slc6a14(-/-) background. Analysis of transcriptomes in tumour tissues from wild-type mice and Slc6a14-null mice indicated no compensatory changes in the expression of any other amino acid transporter mRNA. However, the tumours from the null mice showed evidence of amino acid starvation, decreased mTOR signalling and decreased cell proliferation. These studies demonstrate that SLC6A14 is critical for the maintenance of amino acid nutrition and optimal mammalian target of rapamycin (mTOR) signalling in ER+ breast cancer and that the transporter is a potential target for development of a novel class of anti-cancer drugs targeting amino acid nutrition in tumour cells.

  15. Dynamic recruitment of amino acid transporters to the insect/symbiont interface.

    PubMed

    Duncan, Rebecca P; Husnik, Filip; Van Leuven, James T; Gilbert, Donald G; Dávalos, Liliana M; McCutcheon, John P; Wilson, Alex C C

    2014-03-01

    Symbiosis is well known to influence bacterial symbiont genome evolution and has recently been shown to shape eukaryotic host genomes. Intriguing patterns of host genome evolution, including remarkable numbers of gene duplications, have been observed in the pea aphid, a sap-feeding insect that relies on a bacterial endosymbiont for amino acid provisioning. Previously, we proposed that gene duplication has been important for the evolution of symbiosis based on aphid-specific gene duplication in amino acid transporters (AATs), with some paralogs highly expressed in the cells housing symbionts (bacteriocytes). Here, we use a comparative approach to test the role of gene duplication in enabling recruitment of AATs to bacteriocytes. Using genomic and transcriptomic data, we annotate AATs from sap-feeding and non sap-feeding insects and find that, like aphids, AAT gene families have undergone independent large-scale gene duplications in three of four additional sap-feeding insects. RNA-seq differential expression data indicate that, like aphids, the sap-feeding citrus mealybug possesses several lineage-specific bacteriocyte-enriched paralogs. Further, differential expression data combined with quantitative PCR support independent evolution of bacteriocyte enrichment in sap-feeding insect AATs. Although these data indicate that gene duplication is not necessary to initiate host/symbiont amino acid exchange, they support a role for gene duplication in enabling AATs to mediate novel host/symbiont interactions broadly in the sap-feeding suborder Sternorrhyncha. In combination with recent studies on other symbiotic systems, gene duplication is emerging as a general pattern in host genome evolution.

  16. Proton transport in triflic acid hydrates studied via path integral car-parrinello molecular dynamics.

    PubMed

    Hayes, Robin L; Paddison, Stephen J; Tuckerman, Mark E

    2009-12-31

    The mono-, di-, and tetrahydrates of trifluoromethanesulfonic acid, which contain characteristic H(3)O(+), H(5)O(2)(+), and H(9)O(4)(+) structures, provide model systems for understanding proton transport in materials with high perfluorosulfonic acid density such as perfluorosulfonic acid membranes commonly employed in hydrogen fuel cells. Ab initio molecular dynamics simulations indicate that protons in these solids are predisposed to transfer to the water most strongly bound to sulfonate groups via a Grotthuss-type mechanism, but quickly return to the most solvated defect structure either due to the lack of a nearby species to stabilize the new defect or a preference for the proton to be maximally hydrated. Path integral molecular dynamics of the mono- and dihydrate reveal significant quantum effects that facilitate proton transfer to the "presolvated" water or SO(3)(-) in the first solvation shell and increase the Zundel character of all the defects. These trends are quantified in free energy profiles for each bonding environment. Hydrogen bonding criteria for HOH-OH(2) and HOH-O(3)S are extracted from the two-dimensional potential of mean force. The quantum radial distribution function, radius of gyration, and root-mean-square displacement position correlation function show that the protonic charge is distributed over two or more water molecules. Metastable structural defects with one excess proton shared between two sulfonate groups and another Zundel or Eigen type cation defect are found for the mono- and dihydrate but not for the tetrahydrate crystal. Results for the tetrahydrate native crystal exhibit minor differences at 210 and 250 K. IR spectra are calculated for all native and stable defect structures. Graph theory techniques are used to characterize the chain lengths and ring sizes in the hydrogen bond network. Low conductivities when limited water is present may be attributable to trapping of protons between SO(3)(-) groups and the increased

  17. The amino acid transporter SLC6A15 is a regulator of hippocampal neurochemistry and behavior.

    PubMed

    Santarelli, Sara; Namendorf, Christian; Anderzhanova, Elmira; Gerlach, Tamara; Bedenk, Benedikt; Kaltwasser, Sebastian; Wagner, Klaus; Labermaier, Christiana; Reichel, Judith; Drgonova, Jana; Czisch, Michael; Uhr, Manfred; Schmidt, Mathias V

    2015-09-01

    Although mental disorders as major depression are highly prevalent worldwide their underlying causes remain elusive. Despite the high heritability of depression and a clear genetic contribution to the disease, the identification of genetic risk factors for depression has been very difficult. The first published candidate to reach genome-wide significance in depression was SLC6A15, a neuronal amino acid transporter. With a reported 1,42 fold increased risk of suffering from depres