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Sample records for acid transporter cd36

  1. Hyperinsulinemia Enhances Hepatic Expression of the Fatty Acid Transporter Cd36 and Provokes Hepatosteatosis and Hepatic Insulin Resistance*

    PubMed Central

    Steneberg, Pär; Sykaras, Alexandros G.; Backlund, Fredrik; Straseviciene, Jurate; Söderström, Ingegerd; Edlund, Helena

    2015-01-01

    Hepatosteatosis is associated with the development of both hepatic insulin resistance and Type 2 diabetes. Hepatic expression of Cd36, a fatty acid transporter, is enhanced in obese and diabetic murine models and human nonalcoholic fatty liver disease, and thus it correlates with hyperinsulinemia, steatosis, and insulin resistance. Here, we have explored the effect of hyperinsulinemia on hepatic Cd36 expression, development of hepatosteatosis, insulin resistance, and dysglycemia. A 3-week sucrose-enriched diet was sufficient to provoke hyperinsulinemia, hepatosteatosis, hepatic insulin resistance, and dysglycemia in CBA/J mice. The development of hepatic steatosis and insulin resistance in CBA/J mice on a sucrose-enriched diet was paralleled by increased hepatic expression of the transcription factor Pparγ and its target gene Cd36 whereas that of genes implicated in lipogenesis, fatty acid oxidation, and VLDL secretion was unaltered. Additionally, we demonstrate that insulin, in a Pparγ-dependent manner, is sufficient to directly increase Cd36 expression in perfused livers and isolated hepatocytes. Mouse strains that display low insulin levels, i.e. C57BL6/J, and/or lack hepatic Pparγ, i.e. C3H/HeN, do not develop hepatic steatosis, insulin resistance, or dysglycemia on a sucrose-enriched diet, suggesting that elevated insulin levels, via enhanced CD36 expression, provoke fatty liver development that in turn leads to hepatic insulin resistance and dysglycemia. Thus, our data provide evidence for a direct role for hyperinsulinemia in stimulating hepatic Cd36 expression and thus the development of hepatosteatosis, hepatic insulin resistance, and dysglycemia. PMID:26085100

  2. 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

  3. CD36, but not GPR120, is required for efficient fatty acid utilization during endurance exercise.

    PubMed

    Fujitani, Mina; Matsumura, Shigenobu; Masuda, Daisaku; Yamashita, Shizuya; Fushiki, Tohru; Inoue, Kazuo

    2014-01-01

    Fatty acids (FA) are an important energy source during exercise. In addition to its role as an energy supply for skeletal muscle, FA may activate signaling pathways that regulate gene expression. FA translocase/cluster of differentiation 36 (CD36) and G protein-coupled receptor GPR120 are long-chain FA receptors. In this study, we investigated the impact of CD36 or GPR120 deletion on energy metabolism during exercise. CD36 has been reported to facilitate cellular transport and oxidation of FA during endurance exercise. We show that CD36 deletion decreased exogenous FA oxidation during exercise, using a combination of (13)C-labeled FA oxidation measurement and indirect calorimetry. In contrast, GPR120 deletion had no observable effect on energy metabolism during exercise. Our results further substantiate that CD36-mediated FA transport plays an essential role in efficient FA oxidation during exercise. PMID:25070011

  4. Regulation of the subcellular trafficking of CD36, a major determinant of cardiac fatty acid utilization.

    PubMed

    Glatz, Jan F C; Nabben, Miranda; Heather, Lisa C; Bonen, Arend; Luiken, Joost J F P

    2016-10-01

    Myocardial uptake of long-chain fatty acids largely occurs by facilitated diffusion, involving primarily the membrane-associated protein CD36. Other putative fatty acid transporters, such as FABPpm, FATP1 and FATP4, also play a role, but their quantitative contribution is much smaller or their involvement is rather permissive. Besides its sarcolemmal localization, CD36 is also present in intracellular compartments (endosomes). CD36 cycles between both pools via vesicle-mediated trafficking, and the relative distribution between endosomes versus sarcolemma determines the rate of cardiac fatty acid uptake. A net translocation of CD36 to the sarcolemma is induced by various stimuli, in particular hormones like insulin and myocyte contractions, so as to allow a proper coordination of the rate of fatty acid uptake with rapid fluctuations in myocardial energy needs. Furthermore, changes in cardiac fatty acid utilization that occur in both acute and chronic cardiac disease appear to be accompanied by concomitant changes in the sarcolemmal presence of CD36. Studies in various animal and cell models suggest that interventions aimed at modulating the sarcolemmal presence or functioning of CD36 hold promise as therapy to rectify aberrant rates of fatty acid uptake in order to fight cardiac metabolic remodeling and restore proper contractile function. In this review we discuss our current knowledge about the role of CD36 in cardiac fatty acid uptake and metabolism in health and disease with focus on the regulation of the subcellular trafficking of CD36 and its selective modulation as therapeutic approach for cardiac disease. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:27090938

  5. Molecular cloning, characterization, and expression analysis of fatty acid translocase (FAT/CD36) in the pigeon (Columba livia domestica).

    PubMed

    Xie, P; Zhang, A T; Wang, C; Azzam, M M M; Zou, X T

    2012-07-01

    Fatty acid translocase (FAT/CD36) is a transmembrane glycoprotein that plays an important role in transporting long-chain fatty acids. In the current study, a full-length cDNA of FAT/CD36 was first cloned from the intestine of White King pigeon by rapid amplification of cDNA ends (RACE) method. The full-length cDNA of pigeon FAT/CD36 was 2,282 bp, including a 5'-untranslated region of 224 bp, a 3'-untranslated region of 642 bp, and an open reading frame of 1,416 bp encoding a protein of 471 amino acids with the predicted molecular weight of 52.7 kDa. Sequence comparison indicated that FAT/CD36 of pigeon had high identity with other avian FAT/CD36. Using quantitative real-time PCR, expression of FAT/CD36 was the greatest in the duodenum at 28 d posthatch, and in the jejunum, the expression of FAT/CD36 at 14 d posthatch was greater than at 8 d but the same as 28 d posthatch. However, in the ileum, expression of FAT/CD36 peaked at embryonic d 15 and 8 d posthatch. The effects of long-chain fatty acids on pigeon FAT/CD36 and peroxisome proliferator activated receptor γ (PPARγ) mRNA expression were also investigated in vitro. It showed that a low concentration (5 μM) of oleic acid, palmitic acid, and linoleic acid can significantly increase FAT/CD36 and PPARγ mRNA level in pigeon jejunum. However, for linolenic acid or arachidonic acid, the induction of both gene expressions needed a higher concentration (50 μM or 250 μM). Two hundred and 50 μM palmitic acid was shown to suppress FAT/CD36 gene expression. The results suggest that FAT/CD36 may be a representative of intestine development in pigeon, and it could be regulated by long-chain fatty acids via PPARγ pathway.

  6. Formation of one or more intrachain disulphide bonds is required for the intracellular processing and transport of CD36.

    PubMed Central

    Gruarin, P; Sitia, R; Alessio, M

    1997-01-01

    In monocytes/macrophages, CD36 is thought to have a role as a scavenger receptor, mediating the phagocytosis of apoptotic cells and the endocytic uptake of oxidized low-density lipoproteins and fatty acids. The proposed topology of CD36 predicts that, of ten cysteine residues, six lie in the extracellular domain, whereas four are equally distributed in the two short terminal tails flanking the N-terminal and C-terminal hydrophobic stretches. Here we investigate the formation of intrachain disulphide bonds, on the basis of the assumption that the cysteine residues present in the luminal domains are generally oxidized, whereas those in the cytosol are reduced. As revealed by gel mobility-shift assays, disulphide bonds are present in the extracellular domain of the CD36 molecule. The formation of these bonds is required for the transport of CD36 from endoplasmic reticulum to Golgi. Furthermore reactive thiol groups are present in the CD36 sequence, which upon lysis form an intrachain extra loop as an artifact. This disulphide bond is not formed in either (1) truncated CD36 lacking the two C-terminal cysteine residues or (2) Triton X-100-insoluble wild-type CD36 molecules, suggesting that, in this fraction, the C-terminal thiol groups are modified. PMID:9371725

  7. Ca2+ Binding/Permeation via Calcium Channel, CaV1.1, Regulates the Intracellular Distribution of the Fatty Acid Transport Protein, CD36, and Fatty Acid Metabolism.

    PubMed

    Georgiou, Dimitra K; Dagnino-Acosta, Adan; Lee, Chang Seok; Griffin, Deric M; Wang, Hui; Lagor, William R; Pautler, Robia G; Dirksen, Robert T; Hamilton, Susan L

    2015-09-25

    Ca(2+) permeation and/or binding to the skeletal muscle L-type Ca(2+) channel (CaV1.1) facilitates activation of Ca(2+)/calmodulin kinase type II (CaMKII) and Ca(2+) store refilling to reduce muscle fatigue and atrophy (Lee, C. S., Dagnino-Acosta, A., Yarotskyy, V., Hanna, A., Lyfenko, A., Knoblauch, M., Georgiou, D. K., Poché, R. A., Swank, M. W., Long, C., Ismailov, I. I., Lanner, J., Tran, T., Dong, K., Rodney, G. G., Dickinson, M. E., Beeton, C., Zhang, P., Dirksen, R. T., and Hamilton, S. L. (2015) Skelet. Muscle 5, 4). Mice with a mutation (E1014K) in the Cacna1s (α1 subunit of CaV1.1) gene that abolishes Ca(2+) binding within the CaV1.1 pore gain more body weight and fat on a chow diet than control mice, without changes in food intake or activity, suggesting that CaV1.1-mediated CaMKII activation impacts muscle energy expenditure. We delineate a pathway (Cav1.1→ CaMKII→ NOS) in normal skeletal muscle that regulates the intracellular distribution of the fatty acid transport protein, CD36, altering fatty acid metabolism. The consequences of blocking this pathway are decreased mitochondrial β-oxidation and decreased energy expenditure. This study delineates a previously uncharacterized CaV1.1-mediated pathway that regulates energy utilization in skeletal muscle.

  8. Ca2+ Binding/Permeation via Calcium Channel, CaV1.1, Regulates the Intracellular Distribution of the Fatty Acid Transport Protein, CD36, and Fatty Acid Metabolism*

    PubMed Central

    Georgiou, Dimitra K.; Dagnino-Acosta, Adan; Lee, Chang Seok; Griffin, Deric M.; Wang, Hui; Lagor, William R.; Pautler, Robia G.; Dirksen, Robert T.; Hamilton, Susan L.

    2015-01-01

    Ca2+ permeation and/or binding to the skeletal muscle L-type Ca2+ channel (CaV1.1) facilitates activation of Ca2+/calmodulin kinase type II (CaMKII) and Ca2+ store refilling to reduce muscle fatigue and atrophy (Lee, C. S., Dagnino-Acosta, A., Yarotskyy, V., Hanna, A., Lyfenko, A., Knoblauch, M., Georgiou, D. K., Poché, R. A., Swank, M. W., Long, C., Ismailov, I. I., Lanner, J., Tran, T., Dong, K., Rodney, G. G., Dickinson, M. E., Beeton, C., Zhang, P., Dirksen, R. T., and Hamilton, S. L. (2015) Skelet. Muscle 5, 4). Mice with a mutation (E1014K) in the Cacna1s (α1 subunit of CaV1.1) gene that abolishes Ca2+ binding within the CaV1.1 pore gain more body weight and fat on a chow diet than control mice, without changes in food intake or activity, suggesting that CaV1.1-mediated CaMKII activation impacts muscle energy expenditure. We delineate a pathway (Cav1.1→ CaMKII→ NOS) in normal skeletal muscle that regulates the intracellular distribution of the fatty acid transport protein, CD36, altering fatty acid metabolism. The consequences of blocking this pathway are decreased mitochondrial β-oxidation and decreased energy expenditure. This study delineates a previously uncharacterized CaV1.1-mediated pathway that regulates energy utilization in skeletal muscle. PMID:26245899

  9. CD36 binds oxidized low density lipoprotein (LDL) in a mechanism dependent upon fatty acid binding.

    PubMed

    Jay, Anthony G; Chen, Alexander N; Paz, Miguel A; Hung, Justin P; Hamilton, James A

    2015-02-20

    The association of unesterified fatty acid (FA) with the scavenger receptor CD36 has been actively researched, with focuses on FA and oxidized low density lipoprotein (oxLDL) uptake. CD36 has been shown to bind FA, but this interaction has been poorly characterized to date. To gain new insights into the physiological relevance of binding of FA to CD36, we characterized FA binding to the ectodomain of CD36 by the biophysical method surface plasmon resonance. Five structurally distinct FAs (saturated, monounsaturated (cis and trans), polyunsaturated, and oxidized) were pulsed across surface plasmon resonance channels, generating association and dissociation binding curves. Except for the oxidized FA HODE, all FAs bound to CD36, with rapid association and dissociation kinetics similar to HSA. Next, to elucidate the role that each FA might play in CD36-mediated oxLDL uptake, we used a fluorescent oxLDL (Dii-oxLDL) live cell assay with confocal microscopy imaging. CD36-mediated uptake in serum-free medium was very low but greatly increased when serum was present. The addition of exogenous FA in serum-free medium increased oxLDL binding and uptake to levels found with serum and affected CD36 plasma membrane distribution. Binding/uptake of oxLDL was dependent upon the FA dose, except for docosahexaenoic acid, which exhibited binding to CD36 but did not activate the uptake of oxLDL. HODE also did not affect oxLDL uptake. High affinity FA binding to CD36 and the effects of each FA on oxLDL uptake have important implications for protein conformation, binding of other ligands, functional properties of CD36, and high plasma FA levels in obesity and type 2 diabetes.

  10. CD36 is involved in oleic acid detection by the murine olfactory system.

    PubMed

    Oberland, Sonja; Ackels, Tobias; Gaab, Stefanie; Pelz, Thomas; Spehr, Jennifer; Spehr, Marc; Neuhaus, Eva M

    2015-01-01

    Olfactory signals influence food intake in a variety of species. To maximize the chances of finding a source of calories, an animal's preference for fatty foods and triglycerides already becomes apparent during olfactory food search behavior. However, the molecular identity of both receptors and ligands mediating olfactory-dependent fatty acid recognition are, so far, undescribed. We here describe that a subset of olfactory sensory neurons expresses the fatty acid receptor CD36 and demonstrate a receptor-like localization of CD36 in olfactory cilia by STED microscopy. CD36-positive olfactory neurons share olfaction-specific transduction elements and project to numerous glomeruli in the ventral olfactory bulb. In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca(2+) imaging experiments is drastically reduced in young CD36 knock-out mice. Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period. Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system. PMID:26441537

  11. CD36 is involved in oleic acid detection by the murine olfactory system

    PubMed Central

    Oberland, Sonja; Ackels, Tobias; Gaab, Stefanie; Pelz, Thomas; Spehr, Jennifer; Spehr, Marc; Neuhaus, Eva M.

    2015-01-01

    Olfactory signals influence food intake in a variety of species. To maximize the chances of finding a source of calories, an animal’s preference for fatty foods and triglycerides already becomes apparent during olfactory food search behavior. However, the molecular identity of both receptors and ligands mediating olfactory-dependent fatty acid recognition are, so far, undescribed. We here describe that a subset of olfactory sensory neurons expresses the fatty acid receptor CD36 and demonstrate a receptor-like localization of CD36 in olfactory cilia by STED microscopy. CD36-positive olfactory neurons share olfaction-specific transduction elements and project to numerous glomeruli in the ventral olfactory bulb. In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca2+ imaging experiments is drastically reduced in young CD36 knock-out mice. Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period. Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system. PMID:26441537

  12. Rosiglitazone increases fatty acid oxidation and fatty acid translocase (FAT/CD36) but not carnitine palmitoyltransferase I in rat muscle mitochondria

    PubMed Central

    Benton, Carley R; Holloway, Graham P; Campbell, S E; Yoshida, Yuko; Tandon, Narendra N; Glatz, Jan F C; Luiken, Joost J J F P; Spriet, Lawrence L; Bonen, Arend

    2008-01-01

    Peroxisome proliferator-activated receptors (PPARs) alter the expression of genes involved in regulating lipid metabolism. Rosiglitazone, a PPARγ agonist, induces tissue-specific effects on lipid metabolism; however, its mode of action in skeletal muscle remains unclear. Since fatty acid translocase (FAT/CD36) was recently identified as a possible regulator of skeletal muscle fatty acid transport and mitochondrial fatty acid oxidation, we examined in this tissue the effects of rosiglitazone infusion (7 days, 1 mg day−1) on FAT/CD36 mRNA and protein, its plasmalemmal content and fatty acid transport. In addition, in isolated subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria we examined rates of fatty acid oxidation, FAT/CD36 and carnitine palmitoyltransferase I (CPTI) protein, and CPTI and β-hydroxyacyl CoA dehydrogenase (β-HAD) activities. Rosiglitazone did not alter FAT/CD36 mRNA or protein expression, FAT/CD36 plasmalemmal content, or the rate of fatty acid transport into muscle (P > 0.05). In contrast, rosiglitazone increased the rates of fatty acid oxidation in both SS (+21%) and IMF mitochondria (+36%). This was accompanied by concomitant increases in FAT/CD36 in subsarcolemmal (SS) (+43%) and intermyofibrillar (IMF) mitochondria (+46%), while SS and IMF CPTI protein content, and CPTI submaximal and maximal activities (P > 0.05) were not altered. Similarly, citrate synthase (CS) and β-HAD activities were also not altered by rosiglitazone in SS and IMF mitochondria (P > 0.05). These studies provide another example whereby changes in mitochondrial fatty oxidation are associated with concomitant changes in mitochondrial FAT/CD36 independent of any changes in CPTI. Moreover, these studies identify for the first time a mechanism by which rosiglitazone stimulates fatty acid oxidation in skeletal muscle, namely the chronic, subcellular relocation of FAT/CD36 to mitochondria. PMID:18238811

  13. Role of FAT/CD36 in fatty acid sensing, energy, and glucose homeostasis regulation in DIO and DR rats

    PubMed Central

    Dunn-Meynell, Ambrose A.; Levin, Barry E.

    2014-01-01

    Hypothalamic fatty acid (FA) sensing neurons alter their activity utilizing the FA translocator/receptor, FAT/CD36. Depletion of ventromedial hypothalamus (VMH) CD36 with adeno-associated viral vector expressing CD36 shRNA (AAV CD36 shRNA) leads to redistribution of adipose stores and insulin resistance in outbred rats. This study assessed the requirement of VMH CD36-mediated FA sensing for the regulation of energy and glucose homeostasis in postnatal day 5 (P5) and P21 selectively bred diet-induced obese (DIO) and diet-resistant (DR) rats using VMH AAV CD36 shRNA injections. P5 CD36 depletion altered VMH neuronal FA sensing predominantly in DIO rats. After 10 wk on a 45% fat diet, DIO rats injected with VMH AAV CD36 shRNA at P21 ate more and gained more weight than DIO AAV controls, while DR AAV CD36 shRNA-injected rats gained less weight than DR AAV controls. VMH CD36 depletion increased inguinal fat pad weights and leptin levels in DIO and DR rats. Although DR AAV CD36 shRNA-injected rats became as obese as DIO AAV controls, only DIO control and CD36 depleted rats became insulin-resistant on a 45% fat diet. VMH CD36 depletion stunted linear growth in DIO and DR rats. DIO rats injected with AAV CD36 shRNA at P5 had increased fat mass, mostly due to a 45% increase in subcutaneous fat. They were also insulin-resistant with an associated 71% increase of liver triglycerides. These results demonstrate that VMH CD36-mediated FA sensing is a critical factor in the regulation of energy and glucose homeostasis and fat deposition in DIO and DR rats. PMID:25477422

  14. Adipokines enhance oleic acid-induced proliferation of vascular smooth muscle cells by inducing CD36 expression.

    PubMed

    Schlich, Raphaela; Lamers, Daniela; Eckel, Jürgen; Sell, Henrike

    2015-01-01

    Adipose tissue is not only releasing lipids but also various adipokines that are both dysregulated in the obese state and may contribute to obesity-associated vascular dysfunction and cardiovascular risk. We have previously shown that the combination of adipocyte-conditioned medium (CM) and oleic acid (OA) increases proliferation of human vascular smooth muscle cells (VSMC) in a synergistic way. We identified vascular endothelial growth factor (VEGF) as a component within CM that is responsible for most of the observed effects. In this study, we investigate novel mechanisms that underlie the combined effects of adipokine and oleic acid-induced proliferation of VSMC. Oleic acid leads to significant lipid accumulation in VSMC that is further enhanced by the combined treatment with CM. Accordingly CM stimulates CD36 expression in VSMC while OA is not affecting CD36. Silencing of CD36 was established and prevents lipid accumulation in all tested conditions. CD36 silencing also abrogates CM- and OA-induced proliferation and considerably reduces proliferation induced by the combination of CM and OA. At the same time, VEGF secretion and VEGF-receptor 1 (VEGF-R1) by VSMC was not affected by CD36 silencing. However, VEGF was not able to induce any proliferation in VSMC after CD36 silencing that also blunted VEGF-induced extracellular signal-regulated kinase (ERK) activation. Finally, combined silencing of CD36 together with a blocking antibody against VEGF prevented most of CMOA-induced proliferation. In conclusion, our results demonstrate that CD36 is mediating CM-induced proliferation of VSMC. Induction of CD36 by adipokines enhances the response of VSMC towards VEGF and OA.

  15. Omega-3 fatty acids attenuate constitutive and insulin-induced CD36 expression through a suppression of PPAR α/γ activity in microvascular endothelial cells.

    PubMed

    Madonna, Rosalinda; Salerni, Sara; Schiavone, Deborah; Glatz, Jan F; Geng, Yong-Jian; De Caterina, Raffaele

    2011-09-01

    Microvascular dysfunction occurs in insulin resistance and/or hyperinsulinaemia. Enhanced uptake of free fatty acids (FFA) and oxidised low-density lipoproteins (oxLDL) may lead to oxidative stress and microvascular dysfunction interacting with CD36, a PPARα/γ-regulated scavenger receptor and long-chain FFA transporter. We investigated CD36 expression and CD36-mediated oxLDL uptake before and after insulin treatment in human dermal microvascular endothelial cells (HMVECs), ± different types of fatty acids (FA), including palmitic, oleic, linoleic, arachidonic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. Insulin (10(-8) and 10(-7) M) time-dependently increased DiI-oxLDL uptake and CD36 surface expression (by 30 ± 13%, p<0.05 vs. untreated control after 24 hours incubation), as assessed by ELISA and flow cytometry, an effect that was potentiated by the PI3-kinase inhibitor wortmannin and reverted by the ERK1/2 inhibitor PD98059 and the PPARα/γ antagonist GW9662. A ≥ 24 hour exposure to 50 μM DHA or EPA, but not other FA, blunted both the constitutive (by 23 ± 3% and 29 ± 2%, respectively, p<0.05 for both) and insulin-induced CD36 expressions (by 45 ± 27 % and 12 ± 3 %, respectively, p<0.05 for both), along with insulin-induced uptake of DiI-oxLDL and the downregulation of phosphorylated endothelial nitric oxide synthase (P-eNOS). At gel shift assays, DHA reverted insulin-induced basal and oxLDL-stimulated transactivation of PPRE and DNA binding of PPARα/γ and NF-κB. In conclusion, omega-3 fatty acids blunt the increased CD36 expression and activity promoted by high concentrations of insulin. Such mechanisms may be the basis for the use of omega-3 fatty acids in diabetic microvasculopathy. PMID:21727988

  16. Molecular hydrogen attenuates fatty acid uptake and lipid accumulation through downregulating CD36 expression in HepG2 cells

    PubMed Central

    2013-01-01

    Background There is accumulating evidence that obesity is closely associated with an impaired free fatty acid metabolism as well as with insulin resistance and inflammation. Excessive fatty acid uptake mediated by fatty acid translocase CD36 plays an important role in hepatic steatosis. Molecular hydrogen has been shown to attenuate oxidative stress and improve lipid, glucose and energy metabolism in patients and animal models of hepatic steatosis and atherosclerosis, but the underlying molecular mechanisms remain largely unknown. Methods Human hepatoma HepG2 cells were exposed to palmitate-BSA complex after treatment with or without hydrogen for 24 h. The fatty acid uptake was measured by using spectrofluorometry and the lipid content was detected by Oil Red O staining. JNK phosphorylation and CD36 expression were analyzed by Western blot and real-time PCR analyses. Results Pretreatment with hydrogen reduced fatty acid uptake and lipid accumulation after palmitate overload in HepG2 cells, which was associated with inhibition of JNK activation. Hydrogen treatment did not alter CD36 mRNA expression but reduced CD36 protein expression. Conclusion Hydrogen inhibits fatty acid uptake and lipid accumulation through the downregulation of CD36 at the protein level in hepatic cultured cells, providing insights into the molecular mechanism underlying the hydrogen effects in vivo on lipid metabolism disorders. PMID:23448206

  17. CD36- and GPR120-mediated Ca2+ Signaling in Human Taste Bud Cells Mediates Differential Responses to Fatty Acids and is Altered in Obese Mice

    PubMed Central

    Ozdener, Mehmet Hakan; Subramaniam, Selvakumar; Sundaresan, Sinju; Sery, Omar; Hashimoto, Toshihiro; Asakawa, Yoshinori; Besnard, Philippe; Abumrad, Nada A.; Khan, Naim Akhtar

    2014-01-01

    Background & Aims It is important to increase our understanding of gustatory detection of dietary fat and its contribution to fat preference. We studied the roles of the fat taste receptors CD36 and GPR120 and their interactions via Ca2+ signaling in fungiform taste bud cells (TBC). Methods We measured Ca2+ signaling in human TBC, transfected with small interfering RNAs (siRNAs) against mRNAs encoding CD36 and GPR120 (or control siRNAs). We also studied Ca2+ signaling in TBC from CD36−/− mice and from wild-type lean and obese mice. Additional studies were conducted with mouse enteroendocrine cell line STC-1 that express GPR120 and stably transfected with human CD36. We measured release of serotonin and GLP-1 from human and mice TBC in response to CD36 and GPR120 activation. Results High concentrations of linoleic acid induced Ca2+ signaling via CD36 and GPR120 in human and mice TBC as well as in STC-1 cells, whereas low concentrations induced Ca2+ signaling via only CD36. Incubation of human and mice fungiform TBC with lineoleic acid downregulated CD36 and upregulated GPR120 in membrane lipid rafts. Obese mice had decreased spontaneous preference for fat. Fungiform TBC from obese mice had reduced Ca2+ and serotonin responses but increased release of GLP1, along with reduced levels of CD36 and increased levels of GPR120 in lipid rafts. Conclusions CD36 and GPR120 have non-overlapping roles in TBC signaling during oro-gustatory perception of dietary lipids; these are differentially regulated by obesity. PMID:24412488

  18. A mixture of apple pomace and rosemary extract improves fructose consumption-induced insulin resistance in rats: modulation of sarcolemmal CD36 and glucose transporter-4

    PubMed Central

    Ma, Peng; Yao, Ling; Lin, Xuemei; Gu, Tieguang; Rong, Xianglu; Batey, Robert; Yamahara, Johji; Wang, Jianwei; Li, Yuhao

    2016-01-01

    Apple pomace is a by-product of the processing of apple for juice, cider or wine preparation. Rosemary is a herb commonly used as spice and flavoring agent in food processing. Evidence suggests that both apple pomace and rosemary have rich bioactive molecules with numerous metabolic effects. To provide more information for using apple pomace and rosemary as functional foods for management of metabolism-associated disorders, the present study investigated the insulin-sensitizing effect of a mixture of apple pomace and rosemary extract (AR). The results showed that treatment with AR (500 mg/kg, daily, by gavage) for 5 weeks attenuated chronic liquid fructose consumption-induced increases in fasting plasma insulin concentration, the homeostasis model assessment of insulin resistance index and the adipose tissue insulin resistance index in rats. Mechanistically, AR suppressed fructose-induced acceleration of the clearance of plasma non-esterified fatty acids during oral glucose tolerance test, and decreased excessive triglyceride accumulation and the increased Oil Red O staining area in the gastrocnemius. Furthermore, AR restored fructose-induced overexpression of sarcolemmal CD36 that is known to contribute to etiology of insulin resistance by facilitating fatty acid uptake, and downregulation of sarcolemmal glucose transporter (GLUT)-4 that is the insulin-responsive glucose transporter. Thus, these results demonstrate that AR improves fructose-induced insulin resistance in rats via modulation of sarcolemmal CD36 and GLUT-4. PMID:27725859

  19. The effect of albumin on podocytes: The role of the fatty acid moiety and the potential role of CD36 scavenger receptor

    SciTech Connect

    Pawluczyk, I.Z.A.; Pervez, A.; Ghaderi Najafabadi, M.; Saleem, M.A.; Topham, P.S.

    2014-08-15

    Evidence is emerging that podocytes are able to endocytose proteins such as albumin using kinetics consistent with a receptor-mediated process. To date the role of the fatty acid moiety on albumin uptake kinetics has not been delineated and the receptor responsible for uptake is yet to be identified. Albumin uptake studies were carried out on cultured human podocytes exposed to FITC-labelled human serum albumin either carrying fatty acids (HSA{sub +FA}) or depleted of them (HSA{sub −FA}). Receptor-mediated endocytosis of FITC-HSA{sub +FA} over 60 min was 5 times greater than that of FITC-HSA{sub −FA}. 24 h exposure of podocytes to albumin up-regulated nephrin expression and induced the activation of caspase-3. These effects were more pronounced in response to HSA{sub −FA.} Individually, anti-CD36 antibodies had no effect upon endocytosis of FITC-HSA. However, a cocktail of 2 antibodies reduced uptake by nearly 50%. Albumin endocytosis was enhanced in the presence of the CD36 specific inhibitor sulfo-N-succinimidyl oleate (SSO) while knock-down of CD36 using CD36siRNA had no effect on uptake. These data suggest that receptor-mediated endocytosis of albumin by podocytes is regulated by the fatty acid moiety, although, some of the detrimental effects are induced independently of it. CD36 does not play a direct role in the uptake of albumin. - Highlights: • The fatty acid moiety is essential for receptor mediated endocytosis of albumin. • Fatty acid depleted albumin is more pathogenic to podocytes. • CD36 is not directly involved in albumin uptake by podocytes.

  20. Technical Report: Triple-Colour Staining Flow Cytometry for Co-Distribution of Thrombospondin Receptor (CD36), Ribonucleic Acid (RNA) and Fetal Haemoglobin (HbF) in Sickle Red Blood Cells.

    PubMed

    Mundee, Y; Bigelow, N C; Davis, B H; Porter, J B

    2001-01-01

    Red blood cells (RBCs) from sickle cell patients (SS) express thrombospondin receptor (CD36), contain ribonucleic acid (RNA, recognised as reticulocytes) and fetal haemoglobin (HbF, defined as F cells) in a higher proportion than RBCs from healthy individuals. The co-distribution of CD36, RNA and HbF on the same RBCs has not been demonstrated due to a lack of detection methods. A triple-colour staining flow cytometry for the co-distribution of CD36, RNA and HbF was developed. The method can simultaneously determine CD36-expressing RBCs (CD36 cells), RNA-bearing RBCs (reticulocytes), HbF-bearing RBCs (F cells), CD36-expressing reticulocytes (CD36 reticulocytes), CD36-expressing-F cells (CD36-F cells), HbF-bearing reticulocytes (F reticulocytes) and CD36-expressing-F reticulocjrtes (CD36-F reticulocytes). Mouse monoclonal antibody against CD36 (MoAb-CD36), antibodagainst mouse-immunoglobulin conjugated to biotin (Ab-Molg-Bi), streptavidin conjugated to rhodamine phycoerythrin (StA-RFE), MoAb against HbF conjugated to Tri-Colour® (MoAb-HbF-TC), Thiazole orange (TO), Glutaraldehyde and Triton X-100 were used. The procedure takes approximately 7 hours. The numbers of CD36 cells, reticulocytes and F cells obtaining from single and triple staining were well correlated and not significantly different. Intra- and inter-assay coefficient of variation percents (%CVs) of the triple-colour staining were less than 10 and 15% respectively. EDTA blood samples stored at 4°C for less than 3 days are suitable. The method trial was then employed on blood samples from SS and healthy individuals. The method is reproducible, objective and applicable for determination of co-distribution of other membrane and intracellular markers in RBCs.

  1. ROS-dependent Syk and Pyk2-mediated STAT1 activation is required for 15(S)-Hydroxyeicosatetraenoic acid-induced CD36 expression and foam cell formation

    PubMed Central

    Kotla, Sivareddy; Singh, Nikhlesh K.; Traylor, James G.; Orr, A. Wayne; Rao, Gadiparthi N.

    2014-01-01

    15(S)-Hydroxyeicosatetraenoic acid (15(S)-HETE), the major 15-lipoxygenase 1/2 (15-LO1/2) metabolite of arachidonic acid (AA), induces CD36 expression through xanthine oxidase and NADPH oxidase-dependent ROS production and Syk and Pyk2-dependent STAT1 activation. In line with these observations, 15(S)-HETE also induced foam cell formation involving ROS, Syk, Pyk2 and STAT1-mediated CD36 expression. In addition, peritoneal macrophages from Western diet-fed ApoE−/− mice exhibited elevated levels of xanthine oxidase and NADPH oxidase activities, ROS production, Syk, Pyk2, and STAT1 phosphorylation and CD36 expression compared to those from ApoE−/−:12/15-LO−/− mice and these events correlated with increased lipid deposits, macrophage content and lesion progression in the aortic roots. Human atherosclerotic arteries also showed increased 15-LO1 expression, STAT1 phosphorylation and CD36 levels as compared to normal arteries. Together, these findings suggest that 12/15-LO metabolites of AA, particularly 12/15(S)-HETE might play a crucial role in atherogenesis by enhancing foam cell formation. PMID:25152235

  2. CD36 is indispensable for thermogenesis under conditions of fasting and cold stress.

    PubMed

    Putri, Mirasari; Syamsunarno, Mas Rizky A A; Iso, Tatsuya; Yamaguchi, Aiko; Hanaoka, Hirofumi; Sunaga, Hiroaki; Koitabashi, Norimichi; Matsui, Hiroki; Yamazaki, Chiho; Kameo, Satomi; Tsushima, Yoshito; Yokoyama, Tomoyuki; Koyama, Hiroshi; Abumrad, Nada A; Kurabayashi, Masahiko

    2015-02-20

    Hypothermia can occur during fasting when thermoregulatory mechanisms, involving fatty acid (FA) utilization, are disturbed. CD36/FA translocase is a membrane protein which facilitates membrane transport of long-chain FA in the FA consuming heart, skeletal muscle (SkM) and adipose tissues. It also accelerates uptake of triglyceride-rich lipoprotein by brown adipose tissue (BAT) in a cold environment. In mice deficient for CD36 (CD36(-/-) mice), FA uptake is markedly reduced with a compensatory increase in glucose uptake in the heart and SkM, resulting in lower levels of blood glucose especially during fasting. However, the role of CD36 in thermogenic activity during fasting remains to be determined. In fasted CD36(-/-) mice, body temperature drastically decreased shortly after cold exposure. The hypothermia was accompanied by a marked reduction in blood glucose and in stores of triacylglycerols in BAT and of glycogen in glycolytic SkM. Biodistribution analysis using the FA analogue (125)I-BMIPP and the glucose analogue (18)F-FDG revealed that uptake of FA and glucose was severely impaired in BAT and glycolytic SkM in cold-exposed CD36(-/-) mice. Further, induction of the genes of thermogenesis in BAT was blunted in fasted CD36(-/-) mice after cold exposure. These findings strongly suggest that CD36(-/-) mice exhibit pronounced hypothermia after fasting due to depletion of energy storage in BAT and glycolytic SkM and to reduced supply of energy substrates to these tissues. Our study underscores the importance of CD36 for nutrient homeostasis to survive potentially life-threatening challenges, such as cold and starvation.

  3. CD36 is indispensable for thermogenesis under conditions of fasting and cold stress.

    PubMed

    Putri, Mirasari; Syamsunarno, Mas Rizky A A; Iso, Tatsuya; Yamaguchi, Aiko; Hanaoka, Hirofumi; Sunaga, Hiroaki; Koitabashi, Norimichi; Matsui, Hiroki; Yamazaki, Chiho; Kameo, Satomi; Tsushima, Yoshito; Yokoyama, Tomoyuki; Koyama, Hiroshi; Abumrad, Nada A; Kurabayashi, Masahiko

    2015-02-20

    Hypothermia can occur during fasting when thermoregulatory mechanisms, involving fatty acid (FA) utilization, are disturbed. CD36/FA translocase is a membrane protein which facilitates membrane transport of long-chain FA in the FA consuming heart, skeletal muscle (SkM) and adipose tissues. It also accelerates uptake of triglyceride-rich lipoprotein by brown adipose tissue (BAT) in a cold environment. In mice deficient for CD36 (CD36(-/-) mice), FA uptake is markedly reduced with a compensatory increase in glucose uptake in the heart and SkM, resulting in lower levels of blood glucose especially during fasting. However, the role of CD36 in thermogenic activity during fasting remains to be determined. In fasted CD36(-/-) mice, body temperature drastically decreased shortly after cold exposure. The hypothermia was accompanied by a marked reduction in blood glucose and in stores of triacylglycerols in BAT and of glycogen in glycolytic SkM. Biodistribution analysis using the FA analogue (125)I-BMIPP and the glucose analogue (18)F-FDG revealed that uptake of FA and glucose was severely impaired in BAT and glycolytic SkM in cold-exposed CD36(-/-) mice. Further, induction of the genes of thermogenesis in BAT was blunted in fasted CD36(-/-) mice after cold exposure. These findings strongly suggest that CD36(-/-) mice exhibit pronounced hypothermia after fasting due to depletion of energy storage in BAT and glycolytic SkM and to reduced supply of energy substrates to these tissues. Our study underscores the importance of CD36 for nutrient homeostasis to survive potentially life-threatening challenges, such as cold and starvation. PMID:25596128

  4. CD36 is indispensable for thermogenesis under conditions of fasting and cold stress

    SciTech Connect

    Putri, Mirasari; Syamsunarno, Mas Rizky A.A.; Iso, Tatsuya; Yamaguchi, Aiko; Hanaoka, Hirofumi; Sunaga, Hiroaki; Koitabashi, Norimichi; Matsui, Hiroki; Yamazaki, Chiho; Kameo, Satomi; Tsushima, Yoshito; and others

    2015-02-20

    Hypothermia can occur during fasting when thermoregulatory mechanisms, involving fatty acid (FA) utilization, are disturbed. CD36/FA translocase is a membrane protein which facilitates membrane transport of long-chain FA in the FA consuming heart, skeletal muscle (SkM) and adipose tissues. It also accelerates uptake of triglyceride-rich lipoprotein by brown adipose tissue (BAT) in a cold environment. In mice deficient for CD36 (CD36{sup −/−} mice), FA uptake is markedly reduced with a compensatory increase in glucose uptake in the heart and SkM, resulting in lower levels of blood glucose especially during fasting. However, the role of CD36 in thermogenic activity during fasting remains to be determined. In fasted CD36{sup −/−} mice, body temperature drastically decreased shortly after cold exposure. The hypothermia was accompanied by a marked reduction in blood glucose and in stores of triacylglycerols in BAT and of glycogen in glycolytic SkM. Biodistribution analysis using the FA analogue {sup 125}I-BMIPP and the glucose analogue {sup 18}F-FDG revealed that uptake of FA and glucose was severely impaired in BAT and glycolytic SkM in cold-exposed CD36{sup −/−} mice. Further, induction of the genes of thermogenesis in BAT was blunted in fasted CD36{sup −/−} mice after cold exposure. These findings strongly suggest that CD36{sup −/−} mice exhibit pronounced hypothermia after fasting due to depletion of energy storage in BAT and glycolytic SkM and to reduced supply of energy substrates to these tissues. Our study underscores the importance of CD36 for nutrient homeostasis to survive potentially life-threatening challenges, such as cold and starvation. - Highlights: • We examined the role of CD36 in thermogenesis during cold exposure. • CD36{sup −/−} mice exhibit rapid hypothermia after cold exposure during fasting. • Uptake of fatty acid and glucose is impaired in thermogenic tissues during fasting. • Storage of energy substrates is

  5. The role of CD36 in the regulation of myocardial lipid metabolism.

    PubMed

    Kim, Ty T; Dyck, Jason R B

    2016-10-01

    Since the heart has one of the highest energy requirements of all organs in the body, it requires a constant and plentiful supply of fuel to function properly. Mitochondrial oxidation of lipids provides a major source of ATP for the heart, and the cellular processes that regulate lipid uptake and utilization are important contributors to maintaining proper myocardial energetic status. Although numerous proteins are coordinately regulated in order to ensure proper fatty acid utilization in the cardiomyocyte, a key first step in this process is the entry of fatty acids into the cell. An important protein involved in the transport of fatty acids into the cardiomyocyte is the plasma membrane-associated protein known as fatty acid translocase (FAT; also known as CD36). While multiple proteins are involved in facilitating fatty acid uptake in the heart, CD36 accounts for approximately 50-70% of the total fatty acid taken up in cardiomyocytes. As such, myocardial metabolism of fatty acids may depend upon proper CD36 function. Consistent with this, changes in CD36 levels/function have been implicated in the alteration of myocardial metabolism in the pathophysiology of certain cardiovascular diseases. As such, a better understanding of the role and function of CD36 in the heart may provide important insights for the development of new treatments for specific cardiovascular diseases. Herein, we review the role of CD36 in myocardial lipid metabolism in the healthy heart and describe how CD36-mediated alterations in lipid metabolism may contribute to cardiovascular disease. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:26995462

  6. The Glucotoxicity Protecting Effect of Ezetimibe in Pancreatic Beta Cells via Inhibition of CD36

    PubMed Central

    2016-01-01

    Inhibition of CD36, a fatty acid transporter, has been reported to prevent glucotoxicity and ameliorate high glucose induced beta cell dysfunction. Ezetimibe is a selective cholesterol absorption inhibitor that blocks Niemann Pick C1-like 1 protein, but may exert its effect through suppression of CD36. We attempted to clarify the beneficial effect of ezetimibe on insulin secreting cells and to determine whether this effect is related to change of CD36 expression. mRNA expression of insulin and CD36, intracellular peroxide level and glucose stimulated insulin secretion (GSIS) under normal (5.6 mM) or high glucose (30 mM) condition in INS-1 cells and primary rat islet cells were compared. Changes of the aforementioned factors with treatment with ezetimibe (20 μM) under normal or high glucose condition were also assessed. mRNA expression of insulin was decreased with high glucose, which was reversed by ezetimibe in both INS-1 cells and primary rat islets. CD36 mRNA expression was increased with high glucose, but decreased by ezetimibe in INS-1 cells and primary rat islets. Three-day treatment with high glucose resulted in an increase in intracellular peroxide level; however, it was decreased by treatment with ezetimibe. Decrease in GSIS by three-day treatment with high glucose was reversed by ezetimibe. Palmitate uptake following exposure to high glucose conditions for three days was significantly elevated, which was reversed by ezetimibe in INS-1 cells. Ezetimibe may prevent glucotoxicity in pancreatic β-cells through a decrease in fatty acid influx via inhibition of CD36. PMID:27051238

  7. The terminal six amino-acids of the carboxy cytoplasmic tail of CD36 contain a functional domain implicated in the binding and capture of oxidized low-density lipoprotein.

    PubMed Central

    Malaud, Eric; Hourton, Delphine; Giroux, Louise Marie; Ninio, Ewa; Buckland, Robin; McGregor, John L

    2002-01-01

    CD36, a major adhesion molecule expressed by monocytes/macrophages, plays a key role in the binding and internalization of oxidized low-density lipoprotein (OxLDL). This adhesion molecule, a member of an important scavenger receptor family, contains a very short C-terminal cytoplasmic tail that is known to induce intracellular signalling events. However, the domains on the cytoplasmic tail involved in such signal transduction are unknown. In this study, we have investigated the functional components of the cytoplasmic tail by site-directed mutagenesis coupled with functional OxLDL and monoclonal antibody (mAb) binding studies. Seven truncated or punctual CD36 constructs, localized in the cytoplasmic tail, were produced by site-directed mutagenesis. Each construct was stably expressed in HEK293 cells. We used a quantitative and a qualitative method, labelling OxLDL with either iodine or rhodamine, to determine the functional importance of the cytoplasmic domains in OxLDL internalization. Results indicate that: (1) a deletion of the last amino-acid (construct K472STOP) significantly reduces, compared with wild-type, the binding, internalization and degradation of OxLDL; (2) truncation of the last six amino-acids (construct R467STOP) significantly reduces OxLDL binding; (3) the above two constructs (K472STOP and R467STOP) showed a reduced rate of OxLDL internalization compared with wild-type; (4) the binding and rate of internalization of an anti-CD36 monoclonal antibody (10/5) was not affected by the above mentioned mutants (K472STOP and R467STOP), compared with wild-type. This study shows, for the first time, a specific site on the CD36 cytoplasmic tail that is critical for the binding, endocytosis and targeting of OxLDL. PMID:12023894

  8. CD36 deficiency attenuates experimental mycobacterial infection

    PubMed Central

    2010-01-01

    Background Members of the CD36 scavenger receptor family have been implicated as sensors of microbial products that mediate phagocytosis and inflammation in response to a broad range of pathogens. We investigated the role of CD36 in host response to mycobacterial infection. Methods Experimental Mycobacterium bovis Bacillus Calmette-Guérin (BCG) infection in Cd36+/+ and Cd36-/- mice, and in vitro co-cultivation of M. tuberculosis, BCG and M. marinum with Cd36+/+ and Cd36-/-murine macrophages. Results Using an in vivo model of BCG infection in Cd36+/+ and Cd36-/- mice, we found that mycobacterial burden in liver and spleen is reduced (83% lower peak splenic colony forming units, p < 0.001), as well as the density of granulomas, and circulating tumor necrosis factor (TNF) levels in Cd36-/- animals. Intracellular growth of all three mycobacterial species was reduced in Cd36-/- relative to wild type Cd36+/+ macrophages in vitro. This difference was not attributable to alterations in mycobacterial uptake, macrophage viability, rate of macrophage apoptosis, production of reactive oxygen and/or nitrogen species, TNF or interleukin-10. Using an in vitro model designed to recapitulate cellular events implicated in mycobacterial infection and dissemination in vivo (i.e., phagocytosis of apoptotic macrophages containing mycobacteria), we demonstrated reduced recovery of viable mycobacteria within Cd36-/- macrophages. Conclusions Together, these data indicate that CD36 deficiency confers resistance to mycobacterial infection. This observation is best explained by reduced intracellular survival of mycobacteria in the Cd36-/- macrophage and a role for CD36 in the cellular events involved in granuloma formation that promote early bacterial expansion and dissemination. PMID:20950462

  9. CD36 Protein Influences Myocardial Ca2+ Homeostasis and Phospholipid Metabolism

    PubMed Central

    Pietka, Terri A.; Sulkin, Matthew S.; Kuda, Ondrej; Wang, Wei; Zhou, Dequan; Yamada, Kathryn A.; Yang, Kui; Su, Xiong; Gross, Richard W.; Nerbonne, Jeanne M.; Efimov, Igor R.; Abumrad, Nada A.

    2012-01-01

    Sarcolemmal CD36 facilitates myocardial fatty acid (FA) uptake, which is markedly reduced in CD36-deficient rodents and humans. CD36 also mediates signal transduction events involving a number of cellular pathways. In taste cells and macrophages, CD36 signaling was recently shown to regulate store-responsive Ca2+ flux and activation of Ca2+-dependent phospholipases A2 that cycle polyunsaturated FA into phospholipids. It is unknown whether CD36 deficiency influences myocardial Ca2+ handling and phospholipid metabolism, which could compromise the heart, typically during stresses. Myocardial function was examined in fed or fasted (18–22 h) CD36−/− and WT mice. Echocardiography and telemetry identified conduction anomalies that were associated with the incidence of sudden death in fasted CD36−/− mice. No anomalies or death occurred in WT mice during fasting. Optical imaging of perfused hearts from fasted CD36−/− mice documented prolongation of Ca2+ transients. Consistent with this, knockdown of CD36 in cardiomyocytes delayed clearance of cytosolic Ca2+. Hearts of CD36−/− mice (fed or fasted) had 3-fold higher SERCA2a and 40% lower phospholamban levels. Phospholamban phosphorylation by protein kinase A (PKA) was enhanced after fasting reflecting increased PKA activity and cAMP levels in CD36−/− hearts. Abnormal Ca2+ homeostasis in the CD36−/− myocardium associated with increased lysophospholipid content and a higher proportion of 22:6 FA in phospholipids suggests altered phospholipase A2 activity and changes in membrane dynamics. The data support the role of CD36 in coordinating Ca2+ homeostasis and lipid metabolism and the importance of this role during myocardial adaptation to fasting. Potential relevance of the findings to CD36-deficient humans would need to be determined. PMID:23019328

  10. Behavioral characterization of CD36 knockout mice with SHIRPA primary screen.

    PubMed

    Zhang, Shuxiao; Wang, Wei; Li, Juan; Cheng, Ke; Zhou, Jingjing; Zhu, Dan; Yang, Deyu; Liang, Zihong; Fang, Liang; Liao, Li; Xie, Peng

    2016-02-15

    CD36 is a member of the class B scavenger receptor family of cell surface proteins, which plays a major role in fatty acid, glucose and lipid metabolism. Besides, CD36 functions as a microglial surface receptor for amyloid beta peptide. Regarding this, we suggest CD36 might also contribute to neuropsychiatric disease. The aim of this study was to achieve a behavioral phenotype of CD36 knockout (CD36(-/-)) mice. We characterized the behavior of CD36(-/-) mice and C57BL/6J mice by subjecting them to a series of tests, which include SHIRPA primary behavioral screen test, 1% sucrose preference test, elevated plus-maze test, open-field test and forced swimming test. The results showed that CD36(-/-) mice traversed more squares, emitted more defecation, exhibited higher tail elevation and had more aggressive behaviors than C57BL/6J mice. The CD36(-/-) mice spent more time and traveled longer distance in periphery zone in the open-field test. Meanwhile, the numbers that CD36(-/-) mice entered in the open arms of elevated plus-maze were reduced. These findings suggest that CD36(-/-) mice present an anxious phenotype and might be involved in neuropsychiatric disorders.

  11. Multiphasic triacylglycerol dynamics in the intact heart during acute in vivo overexpression of CD36

    PubMed Central

    Carley, Andrew N.; Bi, Jian; Wang, Xuerong; Banke, Natasha H.; Dyck, Jason R. B.; O'Donnell, J. Michael; Lewandowski, E. Douglas

    2013-01-01

    Cardiac triacylglycerol (TAG) stores buffer the intracellular availability of long chain fatty acid (LCFA) that act as nuclear receptor ligands, substrate for lipotoxic derivatives, and high energy-yield fuel. The kinetic characteristics of TAG turnover and homeostatic mechanisms linking uptake and storage dynamics in hearts have until now remained elusive. This work examines TAG pool dynamics in the intact beating heart, under normal conditions and in response to acute gene expression-induced changes in CD36. Dynamic mode 13C NMR elucidated multiple kinetic processes in 13C-palmitate incorporation into TAG: an initial, saturable exponential component and a slower linear rate. Although previous work indicates the linear component to reflect TAG turnover, we hypothesized the saturable exponential to reflect transport of LCFA across the sarcolemma. Thus, we overexpressed the LCFA transporter CD36 through cardiac-specific adenoviral infection in vivo. Within 72 h, CD36 expression was increased 40% in intact hearts, accelerating the exponential phase relative to PBS-infused hearts. TAG turnover also increased with elevations in adipose triglyceride lipase (ATGL) and a modest increase in diacylglycerol acyltransferase 1 (DGAT1), without a significant expansion of the intracellular lipid pools. The results demonstrate a dynamic system of reciprocal gene regulation that couples saturable LCFA uptake across the sarcolemma to TAG synthesis/lipolysis rates. PMID:23099442

  12. Functional roles of membrane glycoprotein CD36.

    PubMed

    Daviet, L; McGregor, J L

    1996-01-01

    Cell-cell and cell-extracellular matrix interactions are mediated by a number of membrane glycoproteins. On the basis of structural homologies, several families of cell adhesion molecules (integrins, selectins, immunoglobulins, cadherins, leucine-rich glycoproteins) have been established. Since 1991, a new family of CD36-like proteins has been identified. CD36 is a cell surface glycoprotein that interacts with a large variety of ligands. CD36 has been implicated in thrombosis, vascular biology, lipid metabolism and atherogenesis. In this review, we aim to summarize our present knowledge on this important, multifunctional glycoprotein. PMID:21043590

  13. Hepatic fat accumulation and regulation of FAT/CD36: an effect of hepatic irradiation

    PubMed Central

    Martius, Gesa; Alwahsh, Salamah Mohammad; Rave-Fränk, Margret; Hess, Clemens Friedrich; Christiansen, Hans; Ramadori, Giuliano; Malik, Ihtzaz Ahmed

    2014-01-01

    Irradiation is known to induce inflammation and affect fat metabolic pathways. The current study investigates hepatic fat accumulation and fatty acid transportation in a rat model of single dose liver irradiation (25-Gy). Rat livers were selectively irradiated in-vivo (25-Gy), sham-irradiated rats served as controls. Hepatic lipids were studied by colorimetric assays in liver and serum. Intracellular lipids, protein and mRNA were studied by Nile red staining, immunohistology, Western Blot analysis and RT-PCR in liver, respectively. Changes in FAT/CD36 expression were studied in-vitro in a human monocyte cell line U937 after irradiation in presence or absence of infliximab (IFX). Nile Red staining of liver cryosections showed a quick (12-48 h) increase in fat droplets. Accordingly, hepatic triglycerides (TG) and free fatty acids (FFA) were elevated. An early increase (3-6 h) in the serum level of HDL-C, TG and cholesterol was measured after single dose irradiation followed by a decrease thereafter. Furthermore, expression of the fat transporter protein FAT/CD36 was increased, immunohistochemistry revealed basolateral and cytoplasmic expression in hepatocytes. Moreover, apolipoprotein-B100, -C3 and enzymes (acetyl-CoA carboxylase, lipoprotein-lipase, carnitine-palmitoyltransferase, malonyl-CoA-decarboxylase) involved in fat metabolism were induced at 12-24 h. Early activation of the NFkβ pathway (IκBα) by TNF-α was seen, followed by a significant elevation of serum markers for liver damage (AST and GLDH). TNF-α blockage by anti-TNF-α in cell culture (U937) prevented the increase of FAT/CD36 caused by irradiation. Selective liver irradiation is a model for rapid induction of steatosis hepatis and fat accumulation could be triggered by irradiation-induced inflammatory mediators (e.g. TNF-α). PMID:25197426

  14. Decreased expression of adipose CD36 and FATP1 are associated with increased plasma nonesterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The northern elephant seal undergoes a 2-3 month post-weaning fast during which it depends primarily on the oxidation of fatty acids to meet its energetic demands. The concentration of plasma free fatty acids (FFA) increases and is associated with the development of insulin resistance in late-fasted...

  15. 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

  16. Heart CD36 expression is increased in murine models of diabetes and in mice fed a high fat diet.

    PubMed Central

    Greenwalt, D E; Scheck, S H; Rhinehart-Jones, T

    1995-01-01

    High levels of CD36 expression are found in triglyceride storing and secreting cells such as differentiated adipocytes and mammary secretory epithelial cells and in some capillary endothelial cells. We have found high levels of CD36 in the capillary endothelium of murine adipose tissue and in cardiac and skeletal muscles. Muscle cells themselves were CD36 negative. No CD36 was found in brain endothelium. Cardiac and skeletal muscle tissues are highly oxidative and catabolize long-chain fatty acids as a source of energy while brain tissue does not use long-chain fatty acids for energy production. Since capillary endothelial cell CD36 expression appeared to correlate with parenchymal cell fatty acid utilization and since CD26 has been identified recently as a long-chain fatty acid-binding protein, we examined heart tissue CD36 expression in murine models of insulin-dependent (nonobese diabetic, NOD) and non-insulin-dependent diabetes mellitus (KKAY). Diabetic NOD and KKAY mice had serum triglyceride levels 2.6- and 4.2-fold higher, respectively, than normal mice and exhibited 7- and 3.5-fold higher levels of heart microsomal CD36, respectively, than control mice. Mice fed a 40% fat diet expressed heart tissue CD36 at a level 3.5-fold higher than those fed a 9% fat diet. These data suggest that endothelial cell CD36 expression is related to parenchymal cell lipid metabolism. Images PMID:7544802

  17. CD36 Inhibitors Reduce Postprandial Hypertriglyceridemia and Protect against Diabetic Dyslipidemia and Atherosclerosis

    PubMed Central

    Geloen, Alain; Helin, Lionel; Geeraert, Benjamine; Malaud, Eric; Holvoet, Paul; Marguerie, Gerard

    2012-01-01

    CD36 is recognized as a lipid and fatty acid receptor and plays an important role in the metabolic syndrome and associated cardiac events. The pleiotropic activity and the multiple molecular associations of this scavenger receptor with membrane associated molecules in different cells and tissues have however questioned its potential as a therapeutic target. The present study shows that it is possible to identify low molecular weight chemicals that can block the CD36 binding and uptake functions. These inhibitors were able to reduce arterial lipid deposition, fatty acid intestinal transit, plasma concentration of triglycerides and glucose, to improve insulin sensitivity, glucose tolerance and to reduce the plasma concentration of HbAc1 in different and independent rodent models. Correlation between the anti-CD36 activity of these inhibitors and the known pathophysiological activity of this scavenger receptor in the development of atherosclerosis and diabetes were observed at pharmacological doses. Thus, CD36 might represent an attractive therapeutic target. PMID:22662181

  18. Cluster Differentiating 36 (CD36) Deficiency Attenuates Obesity-Associated Oxidative Stress in the Heart

    PubMed Central

    Gharib, Mohamed; Tao, Huan; Fungwe, Thomas V.; Hajri, Tahar

    2016-01-01

    Rationale Obesity is often associated with a state of oxidative stress and increased lipid deposition in the heart. More importantly, obesity increases lipid influx into the heart and induces excessive production of reactive oxygen species (ROS) leading to cell toxicity and metabolic dysfunction. Cluster differentiating 36 (CD36) protein is highly expressed in the heart and regulates lipid utilization but its role in obesity-associated oxidative stress is still not clear. Objective The aim of this study was to determine the impact of CD36 deficiency on cardiac steatosis, oxidative stress and lipotoxicity associated with obesity. Methods and Results Studies were conducted in control (Lean), obese leptin-deficient (Lepob/ob) and leptin-CD36 double null (Lepob/obCD36-/-) mice. Compared to lean mice, cardiac steatosis, and fatty acid (FA) uptake and oxidation were increased in Lepob/ob mice, while glucose uptake and oxidation was reduced. Moreover, insulin resistance, oxidative stress markers and NADPH oxidase-dependent ROS production were markedly enhanced. This was associated with the induction of NADPH oxidase expression, and increased membrane-associated p47phox, p67phox and protein kinase C. Silencing CD36 in Lepob/ob mice prevented cardiac steatosis, increased insulin sensitivity and glucose utilization, but reduced FA uptake and oxidation. Moreover, CD36 deficiency reduced NADPH oxidase activity and decreased NADPH oxidase-dependent ROS production. In isolated cardiomyocytes, CD36 deficiency reduced palmitate-induced ROS production and normalized NADPH oxidase activity. Conclusions CD36 deficiency prevented obesity-associated cardiac steatosis and insulin resistance, and reduced NADPH oxidase-dependent ROS production. The study demonstrates that CD36 regulates NADPH oxidase activity and mediates FA-induced oxidative stress. PMID:27195707

  19. FAT/CD36 expression alone is insufficient to enhance cellular uptake of oleate

    SciTech Connect

    Eyre, Nicholas S.; Cleland, Leslie G.; Mayrhofer, Graham

    2008-06-06

    Fatty acid translocase (FAT/CD36) is one of several proteins implicated in receptor-mediated uptake of long-chain fatty acids (LCFAs). We have tested whether levels of FAT/CD36 correlate with cellular oleic acid import, using a Tet-Off inducible transfected CHO cell line. Consistent with our previous findings, FAT/CD36 was enriched in lipid raft-derived detergent-resistant membranes (DRMs) that also contained caveolin-1, the marker protein of caveolae. Furthermore in transfected cells, plasma membrane FAT/CD36 co-localized extensively with the lipid raft-enriched ganglioside GM1, and partially with a caveolin-1-EGFP fusion protein. Nevertheless, even at high levels of expression, FAT/CD36 did not affect uptake of oleic acid. We propose that the ability of FAT/CD36 to mediate enhanced uptake of LCFAs is dependent on co-expression of other proteins or factors that are lacking in CHO cells.

  20. Molecular basis of CD36 deficiency. Evidence that a 478C-->T substitution (proline90-->serine) in CD36 cDNA accounts for CD36 deficiency.

    PubMed Central

    Kashiwagi, H; Tomiyama, Y; Honda, S; Kosugi, S; Shiraga, M; Nagao, N; Sekiguchi, S; Kanayama, Y; Kurata, Y; Matsuzawa, Y

    1995-01-01

    CD36 deficiency is divided into two subgroups: neither platelets nor monocytes express CD36 (type I deficiency), and monocytes express CD36 in spite of the lack of platelet CD36 (type II deficiency). We have already demonstrated that a 478C-->T substitution (proline90-->serine) in platelet CD36 cDNA predominates in type II deficiency (Kashiwagi, H., S. Honda, Y. Tomiyama, H. Mizutani, H. Take, Y. Honda, S. Kosugi, Y. Kanayama, Y. Kurata, and Y. Matsuzawa. 1993. Thromb. Haemostasis. 69:481-484). In this study, we revealed that monocyte CD36 cDNA from two type II deficient subjects was heterozygous for C478 and T478 form, while platelet CD36 cDNA of these subjects consisted of only T478 form. In a type I deficient subject, both platelet and monocyte CD36 cDNA showed only T478 form. Expression assay using C478 or T478 form of CD36 cDNA transfected cells revealed that there was an 81-kD precursor form of CD36, and that the maturation of the 81-kD precursor form to the 88-kD mature form of CD36 was markedly impaired by the substitution. The mutated precursor form of CD36 was subsequently degraded in the cytoplasm. These results indicate that the 478C-->T substitution directly leads to CD36 deficiency via defects in posttranslational modification, and that this substitution is the major defects underlying CD36 deficiency. Images PMID:7533783

  1. The structural basis for CD36 binding by the malaria parasite

    PubMed Central

    Hsieh, Fu-Lien; Turner, Louise; Bolla, Jani Reddy; Robinson, Carol V.; Lavstsen, Thomas; Higgins, Matthew K.

    2016-01-01

    CD36 is a scavenger receptor involved in fatty acid metabolism, innate immunity and angiogenesis. It interacts with lipoprotein particles and facilitates uptake of long chain fatty acids. It is also the most common target of the PfEMP1 proteins of the malaria parasite, Plasmodium falciparum, tethering parasite-infected erythrocytes to endothelial receptors. This prevents their destruction by splenic clearance and allows increased parasitaemia. Here we describe the structure of CD36 in complex with long chain fatty acids and a CD36-binding PfEMP1 protein domain. A conserved hydrophobic pocket allows the hugely diverse PfEMP1 protein family to bind to a conserved phenylalanine residue at the membrane distal tip of CD36. This phenylalanine is also required for CD36 to interact with lipoprotein particles. By targeting a site on CD36 that is required for its physiological function, PfEMP1 proteins maintain the ability to tether to the endothelium and avoid splenic clearance. PMID:27667267

  2. Synthetic Amphipathic Helical Peptides Targeting CD36 Attenuate Lipopolysaccharide-Induced Inflammation and Acute Lung Injury.

    PubMed

    Bocharov, Alexander V; Wu, Tinghuai; Baranova, Irina N; Birukova, Anna A; Sviridov, Denis; Vishnyakova, Tatyana G; Remaley, Alan T; Eggerman, Thomas L; Patterson, Amy P; Birukov, Konstantin G

    2016-07-15

    Synthetic amphipathic helical peptides (SAHPs) designed as apolipoprotein A-I mimetics are known to bind to class B scavenger receptors (SR-Bs), SR-BI, SR-BII, and CD36, receptors that mediate lipid transport and facilitate pathogen recognition. In this study, we evaluated SAHPs, selected for targeting human CD36, by their ability to attenuate LPS-induced inflammation, endothelial barrier dysfunction, and acute lung injury (ALI). L37pA, which targets CD36 and SR-BI equally, inhibited LPS-induced IL-8 secretion and barrier dysfunction in cultured endothelial cells while reducing lung neutrophil infiltration by 40% in a mouse model of LPS-induced ALI. A panel of 20 SAHPs was tested in HEK293 cell lines stably transfected with various SR-Bs to identify SAHPs with preferential selectivity toward CD36. Among several SAHPs targeting both SR-BI/BII and CD36 receptors, ELK-B acted predominantly through CD36. Compared with L37pA, 5A, and ELK SAHPs, ELK-B was most effective in reducing the pulmonary barrier dysfunction, neutrophil migration into the lung, and lung inflammation induced by LPS. We conclude that SAHPs with relative selectivity toward CD36 are more potent at inhibiting acute pulmonary inflammation and dysfunction. These data indicate that therapeutic strategies using SAHPs targeting CD36, but not necessarily mimicking all apolipoprotein A-I functions, may be considered a possible new treatment approach for inflammation-induced ALI and pulmonary edema. PMID:27316682

  3. CD36 deficiency impairs intestinal lipid secretion and clearance of chylomicrons from the blood

    PubMed Central

    Drover, Victor A.; Ajmal, Mohammad; Nassir, Fatiha; Davidson, Nicholas O.; Nauli, Andromeda M.; Sahoo, Daisy; Tso, Patrick; Abumrad, Nada A.

    2005-01-01

    CD36 mediates the transfer of fatty acids (FAs) across the plasma membranes of muscle and adipose cells, thus playing an important role in regulating peripheral FA metabolism in vivo. In the proximal intestine, CD36 is localized in abundant quantities on the apical surface of epithelial cells, a pattern similar to that of other proteins implicated in the uptake of dietary FAs. To define the role of CD36 in the intestine, we examined FA utilization and lipoprotein secretion by WT and CD36-null mice in response to acute and chronic fat feeding. CD36-null mice given a fat bolus by gavage or fed a high-fat diet accumulated neutral lipid in the proximal intestine, which indicated abnormal lipid processing. Using a model in which mice were equipped with lymph fistulae, we obtained evidence of defective lipoprotein secretion by directly measuring lipid output. The secretion defect appeared to reflect an impaired ability of CD36-null enterocytes to efficiently synthesize triacylglycerols from dietary FAs in the endoplasmic reticulum. In the plasma of intact mice, the reduced intestinal lipid secretion was masked by slow clearance of intestine-derived lipoproteins. The impaired clearance occurred despite normal lipoprotein lipase activity and likely reflected feedback inhibition of the lipase by FAs due to their defective removal from the plasma. We conclude that CD36 is important for both secretion and clearance of intestinal lipoproteins. CD36 deficiency results in hypertriglyceridemia both in the postprandial and fasting states and in humans may constitute a risk factor for diet-induced type 2 diabetes and cardiovascular disease. PMID:15841205

  4. CD36 is required for myoblast fusion during myogenic differentiation

    SciTech Connect

    Park, Seung-Yoon; Yun, Youngeun; Kim, In-San

    2012-11-02

    Highlights: Black-Right-Pointing-Pointer CD36 expression was induced during myogenic differentiation. Black-Right-Pointing-Pointer CD36 expression was localized in multinucleated myotubes. Black-Right-Pointing-Pointer The expression of myogenic markers is attenuated in CD36 knockdown C2C12 cells. Black-Right-Pointing-Pointer Knockdown of CD36 significantly inhibited myotube formation during differentiation. -- Abstract: Recently, CD36 has been found to be involved in the cytokine-induced fusion of macrophage. Myoblast fusion to form multinucleated myotubes is required for myogenesis and muscle regeneration. Because a search of gene expression database revealed the attenuation of CD36 expression in the muscles of muscular dystrophy patients, the possibility that CD36 could be required for myoblast fusion was investigated. CD36 expression was markedly up-regulated during myoblast differentiation and localized in multinucleated myotubes. Knockdown of endogenous CD36 significantly decreased the expression of myogenic markers as well as myotube formation. These results support the notion that CD36 plays an important role in cell fusion during myogenic differentiation. Our finding will aid the elucidation of the common mechanism governing cell-to-cell fusion in various fusion models.

  5. 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

  6. The CD36, CLA-1(CD36L1), and LIMPII (CD36L2) gene family: Cellular distribution, chromosomal location, and genetic evolution

    SciTech Connect

    Calvo, D.; Vega, M.A.; Dopazo, J.

    1995-01-01

    CD36, CLA-1, and LIMPII are single polypeptide membrane glycoproteins, and the genes encoding them constitute a recently described gene family. In the present paper, a cDNA encoding the human lysosomal membrane protein LIMPII was used to determine its expression pattern in cells of various lineages. Like CLA-1, and in contrast with the restricted expression of CD36, the expression of LIMPII is widespread. Mapping of the human LIMPII and CLA-1 genes (gene symbols CD36L2 and CD36L1, respectively) to specific chromosomes revealed that CLA-1, LIMPII, and CD36 do not form a gene cluster, but are found dispersed on chromosomes 12, 4, and 7, respectively. These data, together with the phylogenetic analysis carried out for the members of this family, indicate that the LIMPII, CIA-1, and CD36 genes diverged early in evolution from an ancestor gene, possibly before the divergence between the arthropods and the vertebrates. 48 refs., 5 figs.

  7. Oral Fat Sensing and CD36 Gene Polymorphism in Algerian Lean and Obese Teenagers.

    PubMed

    Daoudi, Hadjer; Plesník, Jiří; Sayed, Amira; Šerý, Omar; Rouabah, Abdelkader; Rouabah, Leila; Khan, Naim Akhtar

    2015-11-01

    Growing number of evidences have suggested that oral fat sensing, mediated by a glycoprotein CD36 (cluster of differentiation 36), plays a significant role in the development of obesity. Indeed, a decreased expression of CD36 in some obese subjects is associated with high dietary fat intake. In the present study, we examined whether an increase in body mass index (BMI) is associated with altered oleic acid lingual detection thresholds and blood lipid profile in young Algerian teenagers (n = 165). The obese teenagers (n = 83; 14.01 ± 0.19 years; BMI z-score 2.67 ± 0.29) exhibited higher lingual detection threshold for oleic acid than lean participants (n = 82, 13.92 ± 0.23 years; BMI z-score 0.03 ± 0.0001). We also studied the association between rs1761667 polymorphism of CD36 gene and obesity. The AA and AG genotypes were more frequent in obese teenagers, whereas GG genotype was more common in lean participants. The A-allele frequency was higher in obese teenagers than that in lean children. We report that rs1761667 polymorphism of CD36 gene and oro-gustatory thresholds for fat might play a significant role in the development of obesity in young teenagers. PMID:26556365

  8. Oral Fat Sensing and CD36 Gene Polymorphism in Algerian Lean and Obese Teenagers

    PubMed Central

    Daoudi, Hadjer; Plesník, Jiří; Sayed, Amira; Šerý, Omar; Rouabah, Abdelkader; Rouabah, Leila; Khan, Naim Akhtar

    2015-01-01

    Growing number of evidences have suggested that oral fat sensing, mediated by a glycoprotein CD36 (cluster of differentiation 36), plays a significant role in the development of obesity. Indeed, a decreased expression of CD36 in some obese subjects is associated with high dietary fat intake. In the present study, we examined whether an increase in body mass index (BMI) is associated with altered oleic acid lingual detection thresholds and blood lipid profile in young Algerian teenagers (n = 165). The obese teenagers (n = 83; 14.01 ± 0.19 years; BMI z-score 2.67 ± 0.29) exhibited higher lingual detection threshold for oleic acid than lean participants (n = 82, 13.92 ± 0.23 years; BMI z-score 0.03 ± 0.0001). We also studied the association between rs1761667 polymorphism of CD36 gene and obesity. The AA and AG genotypes were more frequent in obese teenagers, whereas GG genotype was more common in lean participants. The A-allele frequency was higher in obese teenagers than that in lean children. We report that rs1761667 polymorphism of CD36 gene and oro-gustatory thresholds for fat might play a significant role in the development of obesity in young teenagers. PMID:26556365

  9. Oral Fat Sensing and CD36 Gene Polymorphism in Algerian Lean and Obese Teenagers.

    PubMed

    Daoudi, Hadjer; Plesník, Jiří; Sayed, Amira; Šerý, Omar; Rouabah, Abdelkader; Rouabah, Leila; Khan, Naim Akhtar

    2015-11-04

    Growing number of evidences have suggested that oral fat sensing, mediated by a glycoprotein CD36 (cluster of differentiation 36), plays a significant role in the development of obesity. Indeed, a decreased expression of CD36 in some obese subjects is associated with high dietary fat intake. In the present study, we examined whether an increase in body mass index (BMI) is associated with altered oleic acid lingual detection thresholds and blood lipid profile in young Algerian teenagers (n = 165). The obese teenagers (n = 83; 14.01 ± 0.19 years; BMI z-score 2.67 ± 0.29) exhibited higher lingual detection threshold for oleic acid than lean participants (n = 82, 13.92 ± 0.23 years; BMI z-score 0.03 ± 0.0001). We also studied the association between rs1761667 polymorphism of CD36 gene and obesity. The AA and AG genotypes were more frequent in obese teenagers, whereas GG genotype was more common in lean participants. The A-allele frequency was higher in obese teenagers than that in lean children. We report that rs1761667 polymorphism of CD36 gene and oro-gustatory thresholds for fat might play a significant role in the development of obesity in young teenagers.

  10. Interaction of thrombospondin1 and CD36 contributes to obesity-associated podocytopathy.

    PubMed

    Cui, Wenpeng; Maimaitiyiming, Hasiyeti; Zhou, Qi; Norman, Heather; Zhou, Changcheng; Wang, Shuxia

    2015-07-01

    Obesity is associated with podocyte injury and the development of proteinuria. Elevated plasma free fatty acid is one of the characteristics of obesity and has been linked to podocyte dysfunction. However, the mechanisms remain unclear. In the current study, we examined the effect of saturated free fatty acid (FFA) on human podocyte apoptosis and function in vitro. The mechanism and its in vivo relevance were also determined. We found that FFA treatment induced human podocyte apoptosis and dysfunction, which was associated with increased expression of a matricellular protein-thrombospondin1 (TSP1). FFA stimulated TSP1 expression in podocytes at the transcriptional levels through activation of MAPK pathway. Addition of purified TSP1 to cell culture media induced podocyte apoptosis and dysfunction. Tis effect is though a TGF-β independent mechanism. Moreover, peptide treatment to block TSP1 binding to its receptor-CD36 attenuated FFA induced podocyte apoptosis, suggesting that TSP1/CD36 interaction mediates FFA-induced podocyte apoptosis. Importantly, using a diet-induced obese mouse model, in vivo data demonstrated that obesity-associated podocyte apoptosis and dysfunction were attenuated in TSP1 deficient mice as well as in CD36 deficient mice. Taken together, these studies provide novel evidence that the interaction of TSP1 with its receptor CD36 contributes to obesity--associated podocytopathy.

  11. CD36 genetic variation, fat intake and liver fibrosis in chronic hepatitis C virus infection

    PubMed Central

    Ramos-Lopez, Omar; Roman, Sonia; Martinez-Lopez, Erika; Fierro, Nora A; Gonzalez-Aldaco, Karina; Jose-Abrego, Alexis; Panduro, Arturo

    2016-01-01

    AIM To analyze the association of the CD36 polymorphism (rs1761667) with dietary intake and liver fibrosis (LF) in chronic hepatitis C (CHC) patients. METHODS In this study, 73 patients with CHC were recruited. The CD36 genotype (G > A) was determined by a TaqMan real-time PCR system. Dietary assessment was carried out using a three-day food record to register the daily intake of macronutrients. Serum lipids and liver enzymes were measured by a dry chemistry assay. LF evaluated by transient elastography (Fibroscan®) and APRI score was classified as mild LF (F1-F2) and advanced LF (F3-F4). RESULTS Overall, the CD36 genotypic frequencies were AA (30.1%), AG (54.8%), and GG (15.1%), whereas the allelic A and G frequencies were 57.5% and 42.5%, respectively. CHC patients who were carriers of the CD36 AA genotype had a higher intake of calories attributable to total fat and saturated fatty acids than those with the non-AA genotypes. Additionally, aspartate aminotransferase (AST) serum values were higher in AA genotype carriers compared to non-AA carriers (91.7 IU/L vs 69.8 IU/L, P = 0.02). Moreover, the AA genotype was associated with an increase of 30.23 IU/L of AST (β = 30.23, 95%CI: 9.0-51.46, P = 0.006). Likewise, the AA genotype was associated with advanced LF compared to the AG (OR = 3.60, 95%CI: 1.16-11.15, P = 0.02) or AG + GG genotypes (OR = 3.52, 95%CI: 1.18-10.45, P = 0.02). CONCLUSION This study suggests that the CD36 (rs1761667) AA genotype is associated with higher fat intake and more instances of advanced LF in CHC patients.

  12. CD36 genetic variation, fat intake and liver fibrosis in chronic hepatitis C virus infection

    PubMed Central

    Ramos-Lopez, Omar; Roman, Sonia; Martinez-Lopez, Erika; Fierro, Nora A; Gonzalez-Aldaco, Karina; Jose-Abrego, Alexis; Panduro, Arturo

    2016-01-01

    AIM To analyze the association of the CD36 polymorphism (rs1761667) with dietary intake and liver fibrosis (LF) in chronic hepatitis C (CHC) patients. METHODS In this study, 73 patients with CHC were recruited. The CD36 genotype (G > A) was determined by a TaqMan real-time PCR system. Dietary assessment was carried out using a three-day food record to register the daily intake of macronutrients. Serum lipids and liver enzymes were measured by a dry chemistry assay. LF evaluated by transient elastography (Fibroscan®) and APRI score was classified as mild LF (F1-F2) and advanced LF (F3-F4). RESULTS Overall, the CD36 genotypic frequencies were AA (30.1%), AG (54.8%), and GG (15.1%), whereas the allelic A and G frequencies were 57.5% and 42.5%, respectively. CHC patients who were carriers of the CD36 AA genotype had a higher intake of calories attributable to total fat and saturated fatty acids than those with the non-AA genotypes. Additionally, aspartate aminotransferase (AST) serum values were higher in AA genotype carriers compared to non-AA carriers (91.7 IU/L vs 69.8 IU/L, P = 0.02). Moreover, the AA genotype was associated with an increase of 30.23 IU/L of AST (β = 30.23, 95%CI: 9.0-51.46, P = 0.006). Likewise, the AA genotype was associated with advanced LF compared to the AG (OR = 3.60, 95%CI: 1.16-11.15, P = 0.02) or AG + GG genotypes (OR = 3.52, 95%CI: 1.18-10.45, P = 0.02). CONCLUSION This study suggests that the CD36 (rs1761667) AA genotype is associated with higher fat intake and more instances of advanced LF in CHC patients. PMID:27660673

  13. Insulin and AMPK regulate FA translocase/CD36 plasma membrane recruitment in cardiomyocytes via Rab GAP AS160 and Rab8a Rab GTPase.

    PubMed

    Samovski, Dmitri; Su, Xiong; Xu, Yingcheng; Abumrad, Nada A; Stahl, Philip D

    2012-04-01

    The FA translocase cluster of differentiation 36 (CD36) facilitates FA uptake by the myocardium, and its surface recruitment in cardiomyocytes is induced by insulin, AMP-dependent protein kinase (AMPK), or contraction. Dysfunction of CD36 trafficking contributes to disordered cardiac FA utilization and promotes progression to disease. The Akt substrate 160 (AS160) Rab GTPase-activating protein (GAP) is a key regulator of vesicular trafficking, and its activity is modulated via phosphorylation. Our study documents that AS160 mediates insulin or AMPK-stimulated surface translocation of CD36 in cardiomyocytes. Knock-down of AS160 redistributes CD36 to the surface and abrogates its translocation by insulin or the AMPK agonist 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR). Conversely, overexpression of a phosphorylation-deficient AS160 mutant (AS160 4P) suppresses the stimulated membrane recruitment of CD36. The AS160 substrate Rab8a GTPase is shown via overexpression and knock-down studies to be specifically involved in insulin/AICAR-induced CD36 membrane recruitment. Our findings directly demonstrate AS160 regulation of CD36 trafficking. In myocytes, the AS160 pathway also mediates the effect of insulin, AMPK, or contraction on surface recruitment of the glucose transporter GLUT4. Thus, AS160 constitutes a point of convergence for coordinating physiological regulation of CD36 and GLUT4 membrane recruitment.

  14. 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

  15. 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.

  16. Innate immunity receptor CD36 promotes cerebral amyloid angiopathy

    PubMed Central

    Park, Laibaik; Zhou, Joan; Zhou, Ping; Pistick, Rose; El Jamal, Sleiman; Younkin, Linda; Pierce, Joseph; Arreguin, Andrea; Anrather, Josef; Younkin, Steven G.; Carlson, George A.; McEwen, Bruce S.; Iadecola, Costantino

    2013-01-01

    Deposition of amyloid-β (Aβ) in cerebral arteries, known as cerebral amyloid angiopathy (CAA), occurs both in the setting of Alzheimer’s disease and independent of it, and can cause cerebrovascular insufficiency and cognitive deficits. The mechanisms leading to CAA have not been established, and no therapeutic targets have been identified. We investigated the role of CD36, an innate immunity receptor involved in Aβ trafficking, in the neurovascular dysfunction, cognitive deficits, and amyloid accumulation that occurs in mice expressing the Swedish mutation of the amyloid precursor protein (Tg2576). We found that Tg2576 mice lacking CD36 have a selective reduction in Aβ1-40 and CAA. This reduced vascular amyloid deposition was associated with preservation of the Aβ vascular clearance receptor LRP-1, and protection from the deleterious effects of Aβ on cerebral arterioles. These beneficial vascular effects were reflected by marked improvements in neurovascular regulation and cognitive performance. Our data suggest that CD36 promotes vascular amyloid deposition and the resulting cerebrovascular damage, leading to neurovascular dysfunction and cognitive deficits. These findings identify a previously unrecognized role of CD36 in the mechanisms of vascular amyloid deposition, and suggest that this scavenger receptor is a putative therapeutic target for CAA and related conditions. PMID:23382216

  17. Leishmania amazonensis Engages CD36 to Drive Parasitophorous Vacuole Maturation

    PubMed Central

    Okuda, Kendi; Tong, Mei; Dempsey, Brian; Moore, Kathryn J.; Gazzinelli, Ricardo T.; Silverman, Neal

    2016-01-01

    Leishmania amastigotes manipulate the activity of macrophages to favor their own success. However, very little is known about the role of innate recognition and signaling triggered by amastigotes in this host-parasite interaction. In this work we developed a new infection model in adult Drosophila to take advantage of its superior genetic resources to identify novel host factors limiting Leishmania amazonensis infection. The model is based on the capacity of macrophage-like cells, plasmatocytes, to phagocytose and control the proliferation of parasites injected into adult flies. Using this model, we screened a collection of RNAi-expressing flies for anti-Leishmania defense factors. Notably, we found three CD36-like scavenger receptors that were important for defending against Leishmania infection. Mechanistic studies in mouse macrophages showed that CD36 accumulates specifically at sites where the parasite contacts the parasitophorous vacuole membrane. Furthermore, CD36-deficient macrophages were defective in the formation of the large parasitophorous vacuole typical of L. amazonensis infection, a phenotype caused by inefficient fusion with late endosomes and/or lysosomes. These data identify an unprecedented role for CD36 in the biogenesis of the parasitophorous vacuole and further highlight the utility of Drosophila as a model system for dissecting innate immune responses to infection. PMID:27280707

  18. Responses of skeletal muscle lipid metabolism in rat gastrocnemius to hypothyroidism and iodothyronine administration: a putative role for FAT/CD36.

    PubMed

    Lombardi, Assunta; De Matteis, Rita; Moreno, Maria; Napolitano, Laura; Busiello, Rosa Anna; Senese, Rosalba; de Lange, Pieter; Lanni, Antonia; Goglia, Fernando

    2012-11-15

    Iodothyronines such as triiodothyronine (T(3)) and 3,5-diiodothyronine (T(2)) influence energy expenditure and lipid metabolism. Skeletal muscle contributes significantly to energy homeostasis, and the above iodothyronines are known to act on this tissue. However, little is known about the cellular/molecular events underlying the effects of T(3) and T(2) on skeletal muscle lipid handling. Since FAT/CD36 is involved in the utilization of free fatty acids by skeletal muscle, specifically in their import into that tissue and presumably their oxidation at the mitochondrial level, we hypothesized that related changes in lipid handling and in FAT/CD36 expression and subcellular redistribution would occur due to hypothyroidism and to T(3) or T(2) administration to hypothyroid rats. In gastrocnemius muscles isolated from hypothyroid rats, FAT/CD36 was upregulated (mRNA levels and total tissue, sarcolemmal, and mitochondrial protein levels). Administration of either T(3) or T(2) to hypothyroid rats resulted in 1) little or no change in FAT/CD36 mRNA level, 2) a decreased total FAT/CD36 protein level, and 3) further increases in FAT/CD36 protein level in sarcolemma and mitochondria. Thus, the main effect of each iodothyronine seemed to be exerted at the level of FAT/CD36 cellular distribution. The effect of further increases in FAT/CD36 protein level in sarcolemma and mitochondria was already evident at 1 h after iodothyronine administration. Each iodothyronine increased the mitochondrial fatty acid oxidation rate. However, the mechanisms underlying their rapid effects seem to differ; T(2) and T(3) each induce FAT/CD36 translocation to mitochondria, but only T(2) induces increases in carnitine palmitoyl transferase system activity and in the mitochondrial substrate oxidation rate.

  19. A CD36 ectodomain mediates insect pheromone detection via a putative tunnelling mechanism.

    PubMed

    Gomez-Diaz, Carolina; Bargeton, Benoîte; Abuin, Liliane; Bukar, Natalia; Reina, Jaime H; Bartoi, Tudor; Graf, Marion; Ong, Huy; Ulbrich, Maximilian H; Masson, Jean-Francois; Benton, Richard

    2016-01-01

    CD36 transmembrane proteins have diverse roles in lipid uptake, cell adhesion and pathogen sensing. Despite numerous in vitro studies, how they act in native cellular contexts is poorly understood. A Drosophila CD36 homologue, sensory neuron membrane protein 1 (SNMP1), was previously shown to facilitate detection of lipid-derived pheromones by their cognate receptors in olfactory cilia. Here we investigate how SNMP1 functions in vivo. Structure-activity dissection demonstrates that SNMP1's ectodomain is essential, but intracellular and transmembrane domains dispensable, for cilia localization and pheromone-evoked responses. SNMP1 can be substituted by mammalian CD36, whose ectodomain can interact with insect pheromones. Homology modelling, using the mammalian LIMP-2 structure as template, reveals a putative tunnel in the SNMP1 ectodomain that is sufficiently large to accommodate pheromone molecules. Amino-acid substitutions predicted to block this tunnel diminish pheromone sensitivity. We propose a model in which SNMP1 funnels hydrophobic pheromones from the extracellular fluid to integral membrane receptors. PMID:27302750

  20. A CD36 ectodomain mediates insect pheromone detection via a putative tunnelling mechanism

    PubMed Central

    Gomez-Diaz, Carolina; Bargeton, Benoîte; Abuin, Liliane; Bukar, Natalia; Reina, Jaime H.; Bartoi, Tudor; Graf, Marion; Ong, Huy; Ulbrich, Maximilian H.; Masson, Jean-Francois; Benton, Richard

    2016-01-01

    CD36 transmembrane proteins have diverse roles in lipid uptake, cell adhesion and pathogen sensing. Despite numerous in vitro studies, how they act in native cellular contexts is poorly understood. A Drosophila CD36 homologue, sensory neuron membrane protein 1 (SNMP1), was previously shown to facilitate detection of lipid-derived pheromones by their cognate receptors in olfactory cilia. Here we investigate how SNMP1 functions in vivo. Structure–activity dissection demonstrates that SNMP1's ectodomain is essential, but intracellular and transmembrane domains dispensable, for cilia localization and pheromone-evoked responses. SNMP1 can be substituted by mammalian CD36, whose ectodomain can interact with insect pheromones. Homology modelling, using the mammalian LIMP-2 structure as template, reveals a putative tunnel in the SNMP1 ectodomain that is sufficiently large to accommodate pheromone molecules. Amino-acid substitutions predicted to block this tunnel diminish pheromone sensitivity. We propose a model in which SNMP1 funnels hydrophobic pheromones from the extracellular fluid to integral membrane receptors. PMID:27302750

  1. CD36 Polymorphism Is Associated with Protection from Cerebral Malaria

    PubMed Central

    Omi, Kazuya; Ohashi, Jun; Patarapotikul, Jintana; Hananantachai, Hathairad; Naka, Izumi; Looareesuwan, Sornchai; Tokunaga, Katsushi

    2003-01-01

    The human protein CD36 is a major receptor for Plasmodium falciparum–infected erythrocytes and contributes to the pathology of P. falciparum malaria. We performed variation screening of the CD36 gene and examined the possible association between CD36 polymorphisms and the severity of malaria in 475 adult Thai patients with P. falciparum malaria. Accordingly, we identified nine CD36 polymorphisms with a high-frequency (>15%) minor allele. Of these, the frequencies of the −14T→C allele in the upstream promoter region and the −53G→T allele in the downstream promoter region were significantly decreased in patients with cerebral malaria compared to those with mild malaria (P=.016 for −14T→C and P=.050 for −53G→T). The analysis of linkage disequilibrium (LD) between the nine common polymorphisms revealed that there are two blocks with strong LD in the CD36 gene and that the −14T→C and −53G→T polymorphisms are within the upstream block of 35 kb from the upstream promoter to exon 8. Further association testing after the second variation screening in the upstream block indicated that the in3(TG)12 (i.e., 12 TG repeats in intron 3) allele is most strongly associated with the reduction in the risk of cerebral malaria (odds ratio 0.59; 95% confidence interval 0.40–0.87; P=.0069). We found, by reverse-transcriptase PCR amplification, that in3(TG)12 is involved in the nonproduction of the variant CD36 transcript that lacks exons 4 and 5. Since exon 5 of the gene is known to encode the ligand-binding domain for P. falciparum–infected erythrocytes, in3(TG)12 itself or a primary variant on the haplotype with in3(TG)12 may be responsible for protection from cerebral malaria in Thailand. Results of the present study suggest that LD mapping has potential for detecting a disease-associated variant on the basis of haplotype blocks. PMID:12506336

  2. CD36-deficient congenic strains show improved glucose tolerance and distinct shifts in metabolic and transcriptomic profiles.

    PubMed

    Šedová, L; Liška, F; Křenová, D; Kazdová, L; Tremblay, J; Krupková, M; Corbeil, G; Hamet, P; Křen, V; Šeda, O

    2012-07-01

    Deficiency of fatty acid translocase Cd36 has been shown to have a major role in the pathogenesis of metabolic syndrome in the spontaneously hypertensive rat (SHR). We have tested the hypothesis that the effects of Cd36 mutation on the features of metabolic syndrome are contextually dependent on genomic background. We have derived two new congenic strains by introgression of limited chromosome 4 regions of SHR origin, both including the defective Cd36 gene, into the genetic background of a highly inbred model of insulin resistance and dyslipidemia, polydactylous (PD) rat strain. We subjected standard diet-fed adult males of PD and the congenic PD.SHR4 strains to metabolic, morphometric and transcriptomic profiling. We observed significantly improved glucose tolerance and lower fasting insulin levels in PD.SHR4 congenics than in PD. One of the PD.SHR4 strains showed lower triglyceride concentrations across major lipoprotein fractions combined with higher levels of low-density lipoprotein cholesterol compared with the PD progenitor. The hepatic transcriptome assessment revealed a network of genes differentially expressed between PD and PD.SHR4 with significant enrichment by members of the circadian rhythmicity pathway (Arntl (Bmal1), Clock, Nfil3, Per2 and Per3). In summary, the introduction of the chromosome 4 region of SHR origin including defective Cd36 into the PD genetic background resulted in disconnected shifts of metabolic profile along with distinct changes in hepatic transcriptome. The synthesis of the current results with those obtained in other Cd36-deficient strains indicates that the eventual metabolic effect of a deleterious mutation such as that of SHR-derived Cd36 is not absolute, but rather a function of complex interactions between environmental and genomic background, upon which it operates.

  3. Rosiglitazone fails to improve hypertriglyceridemia and glucose tolerance in CD36-deficient BN.SHR4 congenic rat strain.

    PubMed

    Seda, Ondrej; Kazdova, Ludmila; Krenova, Drahomira; Kren, Vladimir

    2003-01-15

    The favorable metabolic effects of thiazolidinediones are supposedly related to the peroxisome proliferator-activated receptor-gamma (PPARgamma)-driven changes in lipid metabolism, particularly in free fatty acid (FFA) trafficking. The fatty acid translocase CD36 is one of the proposed PPARgamma targets to mediate this action. We assessed the effect of rosiglitazone (RSG, Avandia) administration in two inbred rat strains, BN/Cub and BN.SHR4 congenic strain, differing in 10 cM proximal segment of chromosome 4. Rats were fed high-sucrose diet with or without RSG for 1 wk. In BN.SHR4, which carries defective Cd36 allele of SHR origin, RSG failed to improve glucose tolerance (assessed by the oral glucose tolerance test), did not lower triglyceridemia, nor induced increases in epididymal and retroperitoneal adipose tissue weights and adipose tissue glucose utilization, effects observed in BN/Cub. On the other hand, the RSG-treated BN.SHR4 showed lower concentrations of FFA and substantial increase in glycogen synthesis and glucose oxidation in skeletal muscle. Altogether, these results support involvement of CD36 in RSG action, suggesting this pharmacogenetic interaction may be of particular importance in CD36-deficient humans.

  4. The A allele of cluster of differentiation 36 (CD36) SNP 1761667 associates with decreased lipid taste perception in obese Tunisian women.

    PubMed

    Mrizak, Ines; Šerý, Omar; Plesnik, Jiří; Arfa, Amel; Fekih, Mariem; Bouslema, Ali; Zaouali, Monia; Tabka, Zouhair; Khan, Naim Akhtar

    2015-04-28

    Recent studies have suggested that excessive intake of dietary fat is associated with obesity. Some obese subjects have been reported to exhibit high thresholds for the gustatory detection of lipids via lipid receptors, such as cluster of differentiation 36 (CD36). We studied lingual detection thresholds for emulsions containing oleic acid in obese Tunisian women (n 203) using a three-alternative forced choice (3-AFC) method. Genotyping of the TNF-α (rs1800629), IL-6 (rs1800795) and CD36 (rs1761667) genes was performed to associate with lipid taste perception thresholds. The CD36 genotype distribution was as follows: GG (n 42), AG (n 102) and AA (n 59). Women with the CD36 GG genotype exhibited oral detection thresholds for oleic acid that were more than three times lower than those with the CD36 AA genotype. The present study confirms a high threshold of gustatory fat detection in obese women with the CD36 AA genotype, but there is no significant association with the IL-6 and TNF-α gene polymorphisms.

  5. A novel role for the dioxin receptor in fatty acid metabolism and hepatic steatosis

    PubMed Central

    Lee, Jung Hoon; Wada, Taira; Febbraio, Maria; He, Jinhan; Matsubara, Tsutomu; Lee, Min Jae; Gonzalez, Frank J.; Xie, Wen

    2010-01-01

    Background & Aims The aryl hydrocarbon receptor (AhR) is a PAS domain transcription factor previously known as the “dioxin receptor” or “xenobiotic receptor.” The goal of this study is to determine the endobiotic role of AhR in hepatic steatosis. Methods Wild type, constitutively activated AhR (CA-AhR) transgenic, AhR null (AhR-/-), and fatty acid translocase CD36/FAT null (CD36-/-) mice were used to investigate the role of AhR in steatosis and the involvement of CD36 in the steatotic effect of AhR. The promoters of the mouse and human CD36 genes were cloned and their regulation by AhR was analyzed. Results Activation of AhR induced spontaneous hepatic steatosis characterized by the accumulation of triglycerides. The steatotic effect of AhR is likely due to the combined upregulation of CD36 and fatty acid transport proteins (FATPs), suppression of fatty acid oxidation, inhibition of hepatic export of triglycerides, increase in peripheral fat mobilization, and increased hepatic oxidative stress. Promoter analysis established CD36 as a novel transcriptional target of AhR. Activation of AhR in liver cells induced CD36 gene expression and enhanced fatty acid uptake. The steatotic effect of an AhR agonist was inhibited in CD36-/- mice. Conclusions Our study reveals a novel link between AhR-induced steatosis and the expression of CD36. Industrial or military exposures to dioxin and related compounds have been linked to increased prevalence of fatty liver in humans. Results from this study may help to establish AhR and its target CD36 as novel therapeutic and preventive targets for fatty liver disease. PMID:20303349

  6. CD36-related protein in Schistosoma japonicum: candidate mediator of selective cholesteryl ester uptake from high-density lipoprotein for egg maturation.

    PubMed

    Okumura-Noji, Kuniko; Miura, Yutaka; Lu, Rui; Asai, Kiyofumi; Ohta, Nobuo; Brindley, Paul J; Yokoyama, Shinji

    2013-03-01

    Familial cholesteryl ester transfer protein (CETP) deficiency is more common in some East Asian populations than elsewhere, suggesting the possibility of a selective advantage of this genetic defect against regional infectious diseases. Historically, infection with the Asian blood fluke Schistosoma japonicum has been endemic in these regions, including Japan. We previously reported that eggs of S. japonicum require cholesteryl ester uptake from normal high-density lipoprotein (HDL) but not from CETP-deficient HDL for their maturation to miracidia, a critical step of the hepatic pathogenesis of schistosomiasis. Herein we show that cholesteryl ester uptake is selective from HDL, and identified CD36-related protein (CD36RP) as a candidate to mediate the reaction. CD36RP was cloned from the adult and the egg developmental stages of S. japonicum, with 1880 bp encoding 506 amino acid residues exhibiting the CD36 domains and two transmembrane regions. Using antibodies against recombinant peptides representing the potential extracellular domains of CD36RP, Western blotting detected a protein with a molecular mass of 82 kDa in the particulate fraction of the adult parasite cells, which was reduced to 62 kDa after N-glycanase treatment. The extracellular domain peptide bound human HDL, as established by immunoblots following nondenaturing gel electrophoresis. Antibodies against the extracellular domain suppressed HDL cholesteryl ester uptake and maturation of the eggs in vitro. CD36RP is a candidate receptor on eggs of S. japonicum that facilitates uptake of HDL cholesteryl ester necessary for egg embryonation and maturation.

  7. CD36 mediates proximal tubular binding and uptake of albumin and is upregulated in proteinuric nephropathies.

    PubMed

    Baines, Richard J; Chana, Ravinder S; Hall, Matthew; Febbraio, Maria; Kennedy, David; Brunskill, Nigel J

    2012-10-01

    Dysregulation of renal tubular protein handling in proteinuria contributes to the development of chronic kidney disease. We investigated the role of CD36 as a novel candidate mediator of albumin binding and endocytosis in the kidney proximal tubule using both in vitro and in vivo approaches, and in nephrotic patient renal biopsy samples. In CD36-transfected opossum kidney proximal tubular cells, both binding and uptake of albumin were substantially enhanced. A specific CD36 inhibitor abrogated this effect, but receptor-associated protein, which blocks megalin-mediated endocytosis of albumin, did not. Mouse proximal tubular cells expressed CD36 and this was absent in CD36 null animals, whereas expression of megalin was equal in these animals. Compared with wild-type mice, CD36 null mice demonstrated a significantly increased urinary protein-to-creatinine ratio and albumin-to-creatinine ratio. Proximal tubular cells expressed increased CD36 when exposed to elevated albumin concentrations in culture medium. Expression of CD36 was studied in renal biopsy tissue obtained from adult patients with heavy proteinuria due to minimal change disease, membranous nephropathy, or focal segmental glomerulosclerosis. Proximal tubular CD36 expression was markedly increased in proteinuric individuals. We conclude that CD36 is a novel mediator influencing binding and uptake of albumin in the proximal tubule that is upregulated in proteinuric renal diseases. CD36 may represent a potential therapeutic target in proteinuric nephropathy. PMID:22791331

  8. CD36 is a co-receptor for hepatitis C virus E1 protein attachment

    PubMed Central

    Cheng, Jun-Jun; Li, Jian-Rui; Huang, Meng-Hao; Ma, Lin-Lin; Wu, Zhou-Yi; Jiang, Chen-Chen; Li, Wen-Jing; Li, Yu-Huan; Han, Yan-Xing; Li, Hu; Chen, Jin-Hua; Wang, Yan-Xiang; Song, Dan-Qing; Peng, Zong-Gen; Jiang, Jian-Dong

    2016-01-01

    The cluster of differentiation 36 (CD36) is a membrane protein related to lipid metabolism. We show that HCV infection in vitro increased CD36 expression in either surface or soluble form. HCV attachment was facilitated through a direct interaction between CD36 and HCV E1 protein, causing enhanced entry and replication. The HCV co-receptor effect of CD36 was independent of that of SR-BI. CD36 monoclonal antibodies neutralized the effect of CD36 and reduced HCV replication. CD36 inhibitor sulfo-N-succinimidyl oleate (SSO), which directly bound CD36 but not SR-BI, significantly interrupted HCV entry, and therefore inhibited HCV replication. SSO’s antiviral effect was seen only in HCV but not in other viruses. SSO in combination with known anti-HCV drugs showed additional inhibition against HCV. SSO was considerably safe in mice. Conclusively, CD36 interacts with HCV E1 and might be a co-receptor specific for HCV entry; thus, CD36 could be a potential drug target against HCV. PMID:26898231

  9. Obesity-driven prepartal hepatic lipid accumulation in dairy cows is associated with increased CD36 and SREBP-1 expression.

    PubMed

    Prodanović, Radiša; Korićanac, Goran; Vujanac, Ivan; Djordjević, Ana; Pantelić, Marija; Romić, Snježana; Stanimirović, Zoran; Kirovski, Danijela

    2016-08-01

    We investigated the hypothesis that obesity in dairy cows enhanced expression of proteins involved in hepatic fatty acid uptake and metabolism. Sixteen Holstein-Friesian close-up cows were divided into 2 equal groups based on their body condition score (BCS) as optimal (3.25≤BCS≤3.5) and high (4.0≤BCS≤4.25). Intravenous glucose tolerance test (GTT) and liver biopsies were carried out at day 10 before calving. Blood samples were collected before (basal) and after glucose infusion, and glucose, insulin and non-esterified fatty acid (NEFA) levels were determined at each sample point. In addition, β-hydroxybutyrate and triglycerides levels were measured in the basal samples. The liver biopsies were analyzed for total lipid content and protein expression of insulin receptor beta (IRβ), fatty acid translocase (FAT/CD36) and sterol regulatory element-binding protein-1 (SREBP-1). Basal glucose and insulin were higher in high-BCS cows, which coincided with higher circulating triglycerides and hepatic lipid content. Clearance rate and AUC for NEFA during GTT were higher in optimal-BCS cows. The development of insulin resistance and fatty liver in obese cows was paralleled by increased hepatic expression of the IRβ, CD36 and SREBP-1. These results suggest that increased expression of hepatic CD36 and SREBP-1 is relevant in the obesity-driven lipid accumulation in the liver of dairy cows during late gestation. PMID:27473969

  10. Increased placental fatty acid transporter 6 and binding protein 3 expression and fetal liver lipid accumulation in a mouse model of obesity in pregnancy.

    PubMed

    Díaz, Paula; Harris, Jessica; Rosario, Fredrick J; Powell, Theresa L; Jansson, Thomas

    2015-12-15

    Obesity in pregnancy is associated with increased fetal growth and adiposity, which, in part, is determined by transplacental nutrient supply. Trophoblast uptake and intracellular trafficking of lipids are dependent on placental fatty acid transport proteins (FATP), translocase (FAT/CD36), and fatty acid binding proteins (FABP). We hypothesized that maternal obesity in mice leads to increased placental expression of FAT/CD36, FATPs, and FABPs, and lipid accumulation in the fetal liver. C57/BL6J female mice were fed either a control (C; n = 10) or an obesogenic (OB; n = 10) high-fat, high-sugar diet before mating and throughout pregnancy. At E18.5, placentas and fetal livers were collected. Trophoblast plasma membranes (TPM) were isolated from placental homogenates. Expression of FAT/CD36 and FATP (TPM) and FABP (homogenates) was determined by immunoblotting. Gene expression was assessed by RT-quantitative PCR. Sections of fetal livers were stained for Oil Red O, and lipid droplets were quantified. TPM protein expression of FAT/CD36, FATP 2, and FATP 4 was comparable between C and OB groups. Conversely, TPM FATP 6 expression was increased by 35% in OB compared with C placentas without changes in mRNA expression. FABPs 1, 3-5 and PPARγ were expressed in homogenates, and FABP 3 expression increased 27% in OB compared with C placentas; however, no changes were observed in mRNA expression. Lipid droplet accumulation was 10-fold higher in the livers of fetuses from OB compared with C group. We propose that increased lipid transport capacity in obese mice promotes transplacental fatty acid transport and contributes to excess lipid accumulation in the fetal liver.

  11. Mitigation of Insulin Resistance by Mangiferin in a Rat Model of Fructose-Induced Metabolic Syndrome Is Associated with Modulation of CD36 Redistribution in the Skeletal Muscle.

    PubMed

    Zhou, Liang; Pan, Yongquan; Chonan, Ritsu; Batey, Robert; Rong, Xianglu; Yamahara, Johji; Wang, Jianwei; Li, Yuhao

    2016-01-01

    Mangiferin is one of the prominent active components responsible for the antidiabetic property of many traditional herbs, but its underlying mechanisms of action remain unclear. CD36 in skeletal muscle is known to contribute to the etiology of insulin resistance by facilitating fatty acid uptake. This study investigated the effect of mangiferin on insulin resistance. The results showed that treatment of Wistar-Kyoto rats with mangiferin (15 mg/kg, once daily, by oral gavage) for 7 weeks inhibited chronic liquid fructose consumption-induced increases in plasma insulin concentrations at the baseline and during oral glucose tolerance test (OGTT), and the homeostasis model assessment of insulin resistance index. It also suppressed the increases in fasted plasma nonesterified fatty acid (NEFA) concentration and the adipose tissue insulin resistance index. Mechanistically, mangiferin neither affected intakes of fructose and chow, and the increase in epididymal and perirenal fat, nor attenuated fructose-induced hypertension. In contrast, mangiferin attenuated fructose-induced acceleration of plasma NEFA clearance during OGTT, and tended to decrease excessive triglyceride accumulation in gastrocnemius. Immunofluorescence staining and subsequent rating of CD36-expressing fibers in gastrocnemius revealed that mangiferin restored fructose-stimulated sarcolemmal CD36 overexpression and decreased intracellular CD36 distribution. In addition, the effects of mangiferin on the parameters associated with insulin resistance and abnormal fatty acid metabolism were absent in the spontaneously hypertensive rats carrying numerous nonfunctional mutations in the CD36 gene. Thus, these results suggest that mangiferin treatment mitigates insulin resistance in a rat model of fructose-induced metabolic syndrome by modulating sarcolemmal and intracellular CD36 redistribution in the skeletal muscle.

  12. Low CD36 and LOX-1 Levels and CD36 Gene Subexpression Are Associated with Metabolic Dysregulation in Older Individuals with Abdominal Obesity.

    PubMed

    Madrigal-Ruíz, Perla-Monserrat; Navarro-Hernández, Rosa-Elena; Ruíz-Quezada, Sandra-Luz; Corona-Meraz, Fernanda-Isadora; Vázquez-Del Mercado, Mónica; Gómez-Bañuelos, Eduardo; Castro-Albarran, Jorge; Sandoval-García, Flavio; Flores-Alvarado, Luis-Javier; Martín-Marquez, Beatriz-Teresita

    2016-01-01

    Background. Obesity study in the context of scavenger receptors has been linked to atherosclerosis. CD36 and LOX-1 are important, since they have been associated with atherogenic and metabolic disease but not fat redistribution. The aim of our study was to determinate the association between CD36 and LOX-1 in presence of age and abdominal obesity. Methods. This is a cross-sectional study that included 151 healthy individuals, clinically and anthropometrically classified into two groups by age (<30 and ≥30 years old) and abdominal obesity (according to World Health Organization guidelines). We excluded individuals with any chronic and metabolic illness, use of medication, or smoking. Fasting blood samples were taken to perform determination of CD36 mRNA expression by real-time PCR, lipid profile and metabolic and low grade inflammation markers by routine methods, and soluble scavenger receptors (CD36 and LOX-1) by ELISA. Results. Individuals ≥30 years old with abdominal obesity presented high atherogenic index, lower soluble scavenger receptor levels, and subexpression of CD36 mRNA (54% less). On the other hand, individuals <30 years old with abdominal adiposity presented higher levels in the same parameters, except LOX-1 soluble levels. Conclusion. In this study, individuals over 30 years of age presented low soluble scavenger receptors levels pattern and CD36 gene subexpression, which suggest the chronic metabolic dysregulation in abdominal obesity. PMID:27525284

  13. Low CD36 and LOX-1 Levels and CD36 Gene Subexpression Are Associated with Metabolic Dysregulation in Older Individuals with Abdominal Obesity.

    PubMed

    Madrigal-Ruíz, Perla-Monserrat; Navarro-Hernández, Rosa-Elena; Ruíz-Quezada, Sandra-Luz; Corona-Meraz, Fernanda-Isadora; Vázquez-Del Mercado, Mónica; Gómez-Bañuelos, Eduardo; Castro-Albarran, Jorge; Sandoval-García, Flavio; Flores-Alvarado, Luis-Javier; Martín-Marquez, Beatriz-Teresita

    2016-01-01

    Background. Obesity study in the context of scavenger receptors has been linked to atherosclerosis. CD36 and LOX-1 are important, since they have been associated with atherogenic and metabolic disease but not fat redistribution. The aim of our study was to determinate the association between CD36 and LOX-1 in presence of age and abdominal obesity. Methods. This is a cross-sectional study that included 151 healthy individuals, clinically and anthropometrically classified into two groups by age (<30 and ≥30 years old) and abdominal obesity (according to World Health Organization guidelines). We excluded individuals with any chronic and metabolic illness, use of medication, or smoking. Fasting blood samples were taken to perform determination of CD36 mRNA expression by real-time PCR, lipid profile and metabolic and low grade inflammation markers by routine methods, and soluble scavenger receptors (CD36 and LOX-1) by ELISA. Results. Individuals ≥30 years old with abdominal obesity presented high atherogenic index, lower soluble scavenger receptor levels, and subexpression of CD36 mRNA (54% less). On the other hand, individuals <30 years old with abdominal adiposity presented higher levels in the same parameters, except LOX-1 soluble levels. Conclusion. In this study, individuals over 30 years of age presented low soluble scavenger receptors levels pattern and CD36 gene subexpression, which suggest the chronic metabolic dysregulation in abdominal obesity.

  14. Low CD36 and LOX-1 Levels and CD36 Gene Subexpression Are Associated with Metabolic Dysregulation in Older Individuals with Abdominal Obesity

    PubMed Central

    Castro-Albarran, Jorge; Sandoval-García, Flavio; Flores-Alvarado, Luis-Javier

    2016-01-01

    Background. Obesity study in the context of scavenger receptors has been linked to atherosclerosis. CD36 and LOX-1 are important, since they have been associated with atherogenic and metabolic disease but not fat redistribution. The aim of our study was to determinate the association between CD36 and LOX-1 in presence of age and abdominal obesity. Methods. This is a cross-sectional study that included 151 healthy individuals, clinically and anthropometrically classified into two groups by age (<30 and ≥30 years old) and abdominal obesity (according to World Health Organization guidelines). We excluded individuals with any chronic and metabolic illness, use of medication, or smoking. Fasting blood samples were taken to perform determination of CD36 mRNA expression by real-time PCR, lipid profile and metabolic and low grade inflammation markers by routine methods, and soluble scavenger receptors (CD36 and LOX-1) by ELISA. Results. Individuals ≥30 years old with abdominal obesity presented high atherogenic index, lower soluble scavenger receptor levels, and subexpression of CD36 mRNA (54% less). On the other hand, individuals <30 years old with abdominal adiposity presented higher levels in the same parameters, except LOX-1 soluble levels. Conclusion. In this study, individuals over 30 years of age presented low soluble scavenger receptors levels pattern and CD36 gene subexpression, which suggest the chronic metabolic dysregulation in abdominal obesity. PMID:27525284

  15. Genome-Wide Transcriptome Analysis of CD36 Overexpression in HepG2.2.15 Cells to Explore Its Regulatory Role in Metabolism and the Hepatitis B Virus Life Cycle

    PubMed Central

    Huang, Jian; Zhao, Lei; Yang, Ping; Chen, Zhen; Tang, Ni; Z. Ruan, Xiong; Chen, Yaxi

    2016-01-01

    Hepatitis B virus (HBV) is a hepatocyte-specific DNA virus whose gene expression and replication are closely associated with hepatic metabolic processes. Thus, a potential anti-viral strategy is to target the host metabolic factors necessary for HBV gene expression and replication. Recent studies revealed that fatty acid translocase CD36 is involved in the replication, assembly, storage, and secretion of certain viruses, such as hepatitis C virus (HCV) and human immunodeficiency virus (HIV). However, the relationship between CD36 and the HBV life cycle remains unclear. Here, we showed, for the first time, that increased CD36 expression enhances HBV replication in HepG2.2.15 cells. To understand the underlying molecular basis, we performed genome-wide sequencing of the mRNA from HepG2.2.15-CD36 overexpression (CD36OE) cells and HepG2.2.15-vector cells using RNA Sequencing (RNA-seq) technology to analyze the differential transcriptomic profile. Our results identified 141 differentially expressed genes (DEGs) related to CD36 overexpression, including 79 upregulated genes and 62 downregulated genes. Gene ontology and KEGG pathway analysis revealed that some of the DEGs were involved in various metabolic processes and the HBV life cycle. The reliability of the RNA-Seq data was confirmed by qPCR analysis. Our findings provide clues to build a link between CD36, host metabolism and the HBV life cycle and identified areas that require further investigation. PMID:27749922

  16. Cholesteryl ester hydroperoxides increase macrophage CD36 gene expression via PPAR{alpha}

    SciTech Connect

    Jedidi, Iness; Couturier, Martine; Therond, Patrice; Gardes-Albert, Monique; Legrand, Alain; Barouki, Robert; Bonnefont-Rousselot, Dominique; Aggerbeck, Martine . E-mail: Martine.Aggerbeck@univ-paris5.fr

    2006-12-22

    The uptake of oxidized LDL by macrophages is a key event in the development of atherosclerosis. The scavenger receptor CD36 is one major receptor that internalizes oxidized LDL. In differentiated human macrophages, we compared the regulation of CD36 expression by copper-oxidized LDL or their products. Only oxidized derivatives of cholesteryl ester (CEOOH) increased the amount of CD36 mRNA (2.5-fold). Both oxidized LDL and CEOOH treatment increased two to fourfold the transcription of promoters containing peroxisome-proliferator-activated-receptor responsive elements (PPRE) in the presence of PPAR{alpha} or {gamma}. Electrophoretic-mobility-shift-assays with nuclear extracts prepared from macrophages treated by either oxidized LDL or CEOOH showed increased binding of PPAR{alpha} to the CD36 gene promoter PPRE. In conclusion, CEOOH present in oxidized LDL increase CD36 gene expression in a pathway involving PPAR{alpha}.

  17. Cancer stem cell-specific scavenger receptor CD36 drives glioblastoma progression

    PubMed Central

    Hale, James S.; Otvos, Balint; Sinyuk, Maksim; Alvarado, Alvaro G.; Hitomi, Masahiro; Stoltz, Kevin; Wu, Qiulian; Flavahan, William; Levison, Bruce; Johansen, Mette L.; Schmitt, David; Neltner, Janna M.; Huang, Ping; Ren, Bin; Sloan, Andrew E.; Silverstein, Roy L.; Gladson, Candece L.; DiDonato, Joseph A.; Brown, J. Mark; McIntyre, Thomas; Hazen, Stanley L.; Horbinski, Craig; Rich, Jeremy N.; Lathia, Justin D.

    2014-01-01

    Glioblastoma (GBM) contains a self-renewing, tumorigenic cancer stem cell (CSC) population which contributes to tumor propagation and therapeutic resistance. While the tumor microenvironment is essential to CSC self-renewal, the mechanisms by which CSCs sense and respond to microenvironmental conditions are poorly understood. Scavenger receptors are a broad class of membrane receptors that are well characterized on immune cells and instrumental in sensing apoptotic cellular debris and modified lipids. Here we provide evidence that CSCs selectively utilize the scavenger receptor CD36 to promote their maintenance using patient-derived CSCs and in vivo xenograft models. We detected CD36 expression in GBM cells in addition to previously described cell types including endothelial cells, macrophages and microglia. CD36 was enriched in CSCs and was able to functionally distinguish self-renewing cells. CD36 was co-expressed with integrin alpha 6 and CD133, previously described CSC markers, and CD36 reduction resulted in concomitant loss of integrin alpha 6 expression, self-renewal and tumor initiation capacity. We confirmed that oxidized phospholipids, ligands of CD36, were present in GBM and found that the proliferation of CSCs, but not non-CSCs, increased with exposure to oxidized low-density lipoprotein. CD36 was an informative biomarker of malignancy and negatively correlated to patient prognosis. These results provide a paradigm for CSCs to thrive by the selective enhanced expression of scavenger receptors, providing survival and metabolic advantages. PMID:24737733

  18. Genetic alterations in fatty acid transport and metabolism genes are associated with metastatic progression and poor prognosis of human cancers.

    PubMed

    Nath, Aritro; Chan, Christina

    2016-01-01

    Reprogramming of cellular metabolism is a hallmark feature of cancer cells. While a distinct set of processes drive metastasis when compared to tumorigenesis, it is yet unclear if genetic alterations in metabolic pathways are associated with metastatic progression of human cancers. Here, we analyzed the mutation, copy number variation and gene expression patterns of a literature-derived model of metabolic genes associated with glycolysis (Warburg effect), fatty acid metabolism (lipogenesis, oxidation, lipolysis, esterification) and fatty acid uptake in >9000 primary or metastatic tumor samples from the multi-cancer TCGA datasets. Our association analysis revealed a uniform pattern of Warburg effect mutations influencing prognosis across all tumor types, while copy number alterations in the electron transport chain gene SCO2, fatty acid uptake (CAV1, CD36) and lipogenesis (PPARA, PPARD, MLXIPL) genes were enriched in metastatic tumors. Using gene expression profiles, we established a gene-signature (CAV1, CD36, MLXIPL, CPT1C, CYP2E1) that strongly associated with epithelial-mesenchymal program across multiple cancers. Moreover, stratification of samples based on the copy number or expression profiles of the genes identified in our analysis revealed a significant effect on patient survival rates, thus confirming prominent roles of fatty acid uptake and metabolism in metastatic progression and poor prognosis of human cancers. PMID:26725848

  19. Association of CD36 expression and polymorphism with serum biochemical indices in Cherry Valley duck.

    PubMed

    Wang, D D; Li, W G; Zhang, Y Y

    2016-01-01

    Cluster of differentiation 36 (CD36) plays a crucial role in lipid sensing, innate immunity, atherogenesis, and glycolipid metabolism. This aims of this study were to delineate the CD36 mRNA expression profile in 16 duck tissues using relative quantitative real-time PCR and to screen single nucleotide polymorphisms (SNPs) in the duck CD36 gene by PCR-single strand conformation polymorphism and DNA direct sequencing. In addition, this study investigated CD36 gene expression, genetic variation, and their effect on serum biochemical indices in duck. The results showed that CD36 mRNA was expressed in all tissues, and was highly specific to the pituitary and large intestine, and to subcutaneous and abdominal fat. Furthermore, three genotypes of the SNP g.476593 T > C in exon 9 of the duck CD36 gene were identified: MM, MN, and NN. The dominant genotype and allele were MM and M, with frequencies of 0.453 and 0.643, respectively. The genotype distributions deviated from Hardy-Weinberg equilibrium (P < 0.05) and achieved moderate levels of polymorphism in ducks. Correlation results showed that CD36 mRNA was significantly negatively correlated with triglycerides (P < 0.05), and significantly positively correlated with total protein, globulin, low-density lipoprotein cholesterol, and total cholesterol (P < 0.01). All serum biochemical indices measured, with the exception of triglycerides, in birds with the NN genotype were significantly higher than those in birds with the MM genotype. These findings demonstrated that CD36 might be an important genetic marker for the selection of lipid metabolism and meat quality traits in ducks. PMID:27323079

  20. Genetics of Cd36 and the clustering of multiple cardiovascular risk factors in spontaneous hypertension.

    PubMed

    Pravenec, M; Zidek, V; Simakova, M; Kren, V; Krenova, D; Horky, K; Jachymova, M; Mikova, B; Kazdova, L; Aitman, T J; Churchill, P C; Webb, R C; Hingarh, N H; Yang, Y; Wang, J M; Lezin, E M; Kurtz, T W

    1999-06-01

    Disorders of carbohydrate and lipid metabolism have been reported to cluster in patients with essential hypertension and in spontaneously hypertensive rats (SHRs). A deletion in the Cd36 gene on chromosome 4 has recently been implicated in defective carbohydrate and lipid metabolism in isolated adipocytes from SHRs. However, the role of Cd36 and chromosome 4 in the control of blood pressure and systemic cardiovascular risk factors in SHRs is unknown. In the SHR. BN-Il6/Npy congenic strain, we have found that transfer of a segment of chromosome 4 (including Cd36) from the Brown Norway (BN) rat onto the SHR background induces reductions in blood pressure and ameliorates dietary-induced glucose intolerance, hyperinsulinemia, and hypertriglyceridemia. These results demonstrate that a single chromosome region can influence a broad spectrum of cardiovascular risk factors involved in the hypertension metabolic syndrome. However, analysis of Cd36 genotypes in the SHR and stroke-prone SHR strains indicates that the deletion variant of Cd36 was not critical to the initial selection for hypertension in the SHR model. Thus, the ability of chromosome 4 to influence multiple cardiovascular risk factors, including hypertension, may depend on linkage of Cd36 to other genes trapped within the differential segment of the SHR. BN-Il6/Npy strain.

  1. CD36 is expressed in a defined subpopulation of neurons in the olfactory epithelium

    PubMed Central

    Xavier, André Machado; Ludwig, Raissa Guimarães; Nagai, Maíra Harume; de Almeida, Tiago Jonas; Watanabe, Hebe Mizuno; Hirata, Marcio Yukio; Rosenstock, Tatiana Rosado; Papes, Fabio; Malnic, Bettina; Glezer, Isaias

    2016-01-01

    The sensory neurons in the olfactory epithelium (OSNs) are equipped with a large repertoire of olfactory receptors and the associated signal transduction machinery. In addition to the canonical OSNs, which express odorant receptors (ORs), the epithelium contains specialized subpopulations of sensory neurons that can detect specific information from environmental cues and relay it to relevant neuronal circuitries. Here we describe a subpopulation of mature OSNs in the main olfactory epithelium (MOE) which expresses CD36, a multifunctional receptor involved in a series of biological processes, including sensory perception of lipid ligands. The Cd36 expressing neurons coexpress markers of mature OSNs and are dispersed throughout the MOE. Unlike several ORs analyzed in our study, we found frequent coexpression of the OR Olfr287 in these neurons, suggesting that only a specific set of ORs may be coexpressed with CD36 in OSNs. We also show that CD36 is expressed in the cilia of OSNs, indicating a possible role in odorant detection. CD36-deficient mice display no signs of gross changes in the organization of the olfactory epithelium, but show impaired preference for a lipid mixture odor. Our results show that CD36-expressing neurons represent a distinct population of OSNs, which may have specific functions in olfaction. PMID:27145700

  2. Gene encoding the collagen type I and thrombospondin receptor CD36 is located on chromosome 7q11. 2

    SciTech Connect

    Fernandez-Ruiz, E.; Armesilla, A.L.; Sanchez-Madrid, F.; Vega, M.A. )

    1993-09-01

    The human CD36 is a member of a gene family of structurally related glycoproteins and functions as a receptor for collagen type I and thrombospondin. CD36 also binds to red blood cells infected with the human malaria parasite Plasmodium falciparum. In the present study, the CD36 gene was assigned to chromosome 7 by using the polymerase chain reaction with DNA from human-hamster somatic cell hybrids. Furthermore, the use of a CD36 genomic probe has allowed the localization of the CD36 locus to the 7q11.2 band by fluorescence in situ hybridization coupled with GTG-banding. 14 refs., 2 figs.

  3. 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.

  4. The human CD5L/AIM-CD36 axis: A novel autophagy inducer in macrophages that modulates inflammatory responses.

    PubMed

    Sanjurjo, Lucía; Amézaga, Núria; Aran, Gemma; Naranjo-Gómez, Mar; Arias, Lilibeth; Armengol, Carolina; Borràs, Francesc E; Sarrias, Maria-Rosa

    2015-01-01

    CD5L (CD5 molecule-like) is a secreted glycoprotein that participates in host response to bacterial infection. CD5L influences the monocyte inflammatory response to the bacterial surface molecules lipopolysaccharide (LPS) and lipoteichoic acid (LTA) by inhibiting TNF secretion. Here we studied the intracellular events that lead to macrophage TNF inhibition by human CD5L. To accomplish this goal, we performed functional analyses with human monocytic THP1 macrophages, as well as with peripheral blood monocytes. Inhibition of phosphatidylinositol 3-kinase (PtdIns3K) reversed the inhibitory effect of CD5L on TNF secretion. Among the various PtdIns3K isoforms, our results indicated that CD5L activates PtdIns3K (whose catalytic subunit is termed PIK3C3), a key modulator involved in autophagy. Further analysis revealed a concomitant enhancement of autophagy markers such as cellular LC3-II content, increased LC3 puncta, as well as LC3-LysoTracker Red colocalization. Moreover, electron microscopy showed an increased presence of cytosolic autophagosomes in THP1 macrophages overexpressing CD5L. Besides preventing TNF secretion, CD5L also inhibited IL1B and enhanced IL10 secretion. This macrophage anti-inflammatory pattern of CD5L was reverted upon silencing of autophagy protein ATG7 by siRNA transfection. Additional siRNA experiments in THP1 macrophages indicated that the induction of autophagy mechanisms by CD5L was achieved through cell-surface scavenger receptor CD36, a multiligand receptor expressed in a wide variety of cell types. Our data represent the first evidence that CD36 is involved in autophagy and point to a significant contribution of the CD5L-CD36 axis to the induction of macrophage autophagy.

  5. The human CD5L/AIM-CD36 axis: A novel autophagy inducer in macrophages that modulates inflammatory responses.

    PubMed

    Sanjurjo, Lucía; Amézaga, Núria; Aran, Gemma; Naranjo-Gómez, Mar; Arias, Lilibeth; Armengol, Carolina; Borràs, Francesc E; Sarrias, Maria-Rosa

    2015-01-01

    CD5L (CD5 molecule-like) is a secreted glycoprotein that participates in host response to bacterial infection. CD5L influences the monocyte inflammatory response to the bacterial surface molecules lipopolysaccharide (LPS) and lipoteichoic acid (LTA) by inhibiting TNF secretion. Here we studied the intracellular events that lead to macrophage TNF inhibition by human CD5L. To accomplish this goal, we performed functional analyses with human monocytic THP1 macrophages, as well as with peripheral blood monocytes. Inhibition of phosphatidylinositol 3-kinase (PtdIns3K) reversed the inhibitory effect of CD5L on TNF secretion. Among the various PtdIns3K isoforms, our results indicated that CD5L activates PtdIns3K (whose catalytic subunit is termed PIK3C3), a key modulator involved in autophagy. Further analysis revealed a concomitant enhancement of autophagy markers such as cellular LC3-II content, increased LC3 puncta, as well as LC3-LysoTracker Red colocalization. Moreover, electron microscopy showed an increased presence of cytosolic autophagosomes in THP1 macrophages overexpressing CD5L. Besides preventing TNF secretion, CD5L also inhibited IL1B and enhanced IL10 secretion. This macrophage anti-inflammatory pattern of CD5L was reverted upon silencing of autophagy protein ATG7 by siRNA transfection. Additional siRNA experiments in THP1 macrophages indicated that the induction of autophagy mechanisms by CD5L was achieved through cell-surface scavenger receptor CD36, a multiligand receptor expressed in a wide variety of cell types. Our data represent the first evidence that CD36 is involved in autophagy and point to a significant contribution of the CD5L-CD36 axis to the induction of macrophage autophagy. PMID:25713983

  6. Dietary Lipids Inform the Gut and Brain about Meal Arrival via CD36-Mediated Signal Transduction123

    PubMed Central

    Sundaresan, Sinju; Abumrad, Nada A

    2015-01-01

    Sensing mechanisms for nutrients, in particular dietary fat, operate in the mouth, brain, and gastrointestinal tract and play a key role in regulating feeding behavior and energy balance. Critical to these regulatory mechanisms are the specialized receptors present on taste buds on the tongue, on neurons in specialized centers in the brain, and on epithelial and enteroendocrine cells in the intestinal mucosa. These receptors recognize nutrients and respond by inducing intracellular signals that trigger release of bioactive compounds that influence other organs and help coordinate the response to the meal. Components of dietary fat that are recognized by these receptors are the long-chain fatty acids that act as ligands for 2 G protein-coupled receptors, GPR40 and GPR120, and the fatty acid (FA) translocase/CD36. Recent evidence that emphasizes the important role of CD36 in orosensory, intestinal, and neuronal sensing of FAs under physiologic conditions is highlighted in the review. How this role intersects with that of GPR120 and GPR40 in the regulation of food preference and energy balance is briefly discussed. PMID:26269236

  7. Viral Inhibition of Bacterial Phagocytosis by Human Macrophages: Redundant Role of CD36

    PubMed Central

    Cooper, Grace E.; Pounce, Zoe C.; Wallington, Joshua C.; Bastidas-Legarda, Leidy Y.; Nicholas, Ben; Chidomere, Chiamaka; Robinson, Emily C.; Martin, Kirstin; Tocheva, Anna S.; Christodoulides, Myron; Djukanovic, Ratko; Wilkinson, Tom M. A.

    2016-01-01

    Macrophages are essential to maintaining lung homoeostasis and recent work has demonstrated that influenza-infected lung macrophages downregulate their expression of the scavenger receptor CD36. This receptor has also been shown to be involved in phagocytosis of Streptococcus pneumoniae, a primary agent associated with pneumonia secondary to viral infection. The aim of this study was to investigate the role of CD36 in the effects of viral infection on macrophage phagocytic function. Human monocyte-derived macrophages (MDM) were exposed to H3N2 X31 influenza virus, M37 respiratory syncytial virus (RSV) or UV-irradiated virus. No infection of MDM was seen upon exposure to UV-irradiated virus but incubation with live X31 or M37 resulted in significant levels of viral detection by flow cytometry or RT-PCR respectively. Infection resulted in significantly diminished uptake of S. pneumoniae by MDM and significantly decreased expression of CD36 at both the cell surface and mRNA level. Concurrently, there was a significant increase in IFNβ gene expression in response to infection and we observed a significant decrease in bacterial phagocytosis (p = 0.031) and CD36 gene expression (p = 0.031) by MDM cultured for 24 h in 50IU/ml IFNβ. Knockdown of CD36 by siRNA resulted in decreased phagocytosis, but this was mimicked by transfection reagent alone. When MDM were incubated with CD36 blocking antibodies no effect on phagocytic ability was observed. These data indicate that autologous IFNβ production by virally-infected cells can inhibit bacterial phagocytosis, but that decreased CD36 expression by these cells does not play a major role in this functional deficiency. PMID:27701435

  8. Pathways commonly dysregulated in mouse and human obese adipose tissue: FAT/CD36 modulates differentiation and lipogenesis

    PubMed Central

    Berger, E; Héraud, S; Mojallal, A; Lequeux, C; Weiss-Gayet, M; Damour, O; Géloën, A

    2015-01-01

    Obesity is linked to adipose tissue hypertrophy (increased adipocyte cell size) and hyperplasia (increased cell number). Comparative analyses of gene datasets allowed us to identify 1426 genes which may represent common adipose phenotype in humans and mice. Among them we identified several adipocyte-specific genes dysregulated in obese adipose tissue, involved in either fatty acid storage (acyl CoA synthase ACSL1, hormone-sensitive lipase LIPE, aquaporin 7 AQP7, perilipin PLIN) or cell adhesion (fibronectin FN1, collagens COL1A1, COL1A3, metalloprotein MMP9, or both (scavenger receptor FAT/CD36). Using real-time analysis of cell surface occupancy on xCELLigence system we developed a new method to study lipid uptake and differentiation of mouse 3T3L1 fibroblasts and human adipose stem cells. Both processes are regulated by insulin and fatty acids such as oleic acid. We showed that fatty acid addition to culture media increased the differentiation rate and was required for full differentiation into unilocular adipocytes. Significant activation of lipogenesis, i.e. lipid accumulation, by either insulin or oleic acid was monitored in times ranging from 1 to 24 h, depending on differentiation state, whereas significant effects on adipogenesis, i.e., surperimposed lipid accumulation and gene transcriptional regulations were measured after 3 to 4 d. Combination of selected times for analysis of lipid contents, cell counts, size fractionations, and gene transcriptional regulations showed that FAT/CD36 specific inhibitor AP5258 significantly increased cell survival of oleic acid-treated mouse and human adipocytes, and partially restored the transcriptional response to oleic acid in the presence of insulin through JNK pathway. Taken together, these data open new perspectives to study the molecular mechanisms commonly dysregulated in mouse and human obesity at the level of lipogenesis linked to hypertrophy and adipogenesis linked to hyperplasia. PMID:26257990

  9. Deregulated Lipid Sensing by Intestinal CD36 in Diet-Induced Hyperinsulinemic Obese Mouse Model.

    PubMed

    Buttet, Marjorie; Poirier, Hélène; Traynard, Véronique; Gaire, Kévin; Tran, Thi Thu Trang; Sundaresan, Sinju; Besnard, Philippe; Abumrad, Nada A; Niot, Isabelle

    2016-01-01

    The metabolic syndrome (MetS) greatly increases risk of cardiovascular disease and diabetes and is generally associated with abnormally elevated postprandial triglyceride levels. We evaluated intestinal synthesis of triglyceride-rich lipoproteins (TRL) in a mouse model of the MetS obtained by feeding a palm oil-rich high fat diet (HFD). By contrast to control mice, MetS mice secreted two populations of TRL. If the smaller size population represented 44% of total particles in the beginning of intestinal lipid absorption in MetS mice, it accounted for only 17% after 4 h due to the secretion of larger size TRL. The MetS mice displayed accentuated postprandial hypertriglyceridemia up to 3 h due to a defective TRL clearance. These alterations reflected a delay in lipid induction of genes for key proteins of TRL formation (MTP, L-FABP) and blood clearance (ApoC2). These abnormalities associated with blunted lipid sensing by CD36, which is normally required to optimize jejunal formation of large TRL. In MetS mice CD36 was not downregulated by lipid in contrast to control mice. Treatment of controls with the proteosomal inhibitor MG132, which prevented CD36 downregulation, resulted in blunted lipid-induction of MTP, L-FABP and ApoC2 gene expression, as in MetS mice. Absence of CD36 sensing was due to the hyperinsulinemia in MetS mice. Acute insulin treatment of controls before lipid administration abolished CD36 downregulation, lipid-induction of TRL genes and reduced postprandial triglycerides (TG), while streptozotocin-treatment of MetS mice restored lipid-induced CD36 degradation and TG secretion. In vitro, insulin treatment abolished CD36-mediated up-regulation of MTP in Caco-2 cells. In conclusion, HFD treatment impairs TRL formation in early stage of lipid absorption via insulin-mediated inhibition of CD36 lipid sensing. This impairment results in production of smaller TRL that are cleared slowly from the circulation, which might contribute to the reported

  10. Deregulated Lipid Sensing by Intestinal CD36 in Diet-Induced Hyperinsulinemic Obese Mouse Model

    PubMed Central

    Buttet, Marjorie; Poirier, Hélène; Traynard, Véronique; Gaire, Kévin; Tran, Thi Thu Trang; Sundaresan, Sinju; Besnard, Philippe; Abumrad, Nada A.; Niot, Isabelle

    2016-01-01

    The metabolic syndrome (MetS) greatly increases risk of cardiovascular disease and diabetes and is generally associated with abnormally elevated postprandial triglyceride levels. We evaluated intestinal synthesis of triglyceride-rich lipoproteins (TRL) in a mouse model of the MetS obtained by feeding a palm oil-rich high fat diet (HFD). By contrast to control mice, MetS mice secreted two populations of TRL. If the smaller size population represented 44% of total particles in the beginning of intestinal lipid absorption in MetS mice, it accounted for only 17% after 4 h due to the secretion of larger size TRL. The MetS mice displayed accentuated postprandial hypertriglyceridemia up to 3 h due to a defective TRL clearance. These alterations reflected a delay in lipid induction of genes for key proteins of TRL formation (MTP, L-FABP) and blood clearance (ApoC2). These abnormalities associated with blunted lipid sensing by CD36, which is normally required to optimize jejunal formation of large TRL. In MetS mice CD36 was not downregulated by lipid in contrast to control mice. Treatment of controls with the proteosomal inhibitor MG132, which prevented CD36 downregulation, resulted in blunted lipid-induction of MTP, L-FABP and ApoC2 gene expression, as in MetS mice. Absence of CD36 sensing was due to the hyperinsulinemia in MetS mice. Acute insulin treatment of controls before lipid administration abolished CD36 downregulation, lipid-induction of TRL genes and reduced postprandial triglycerides (TG), while streptozotocin-treatment of MetS mice restored lipid-induced CD36 degradation and TG secretion. In vitro, insulin treatment abolished CD36-mediated up-regulation of MTP in Caco-2 cells. In conclusion, HFD treatment impairs TRL formation in early stage of lipid absorption via insulin-mediated inhibition of CD36 lipid sensing. This impairment results in production of smaller TRL that are cleared slowly from the circulation, which might contribute to the reported

  11. 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

  12. CD36 gene transfer confers capacity for phagocytosis of cells undergoing apoptosis

    PubMed Central

    1995-01-01

    Phagocyte recognition and ingestion of intact cells undergoing apoptosis are key events in this generally important program of cell death. Insufficient phagocyte capacity for apoptotic cells can result in failure to clear dying cells before membrane integrity is lost, resulting in leakage of noxious cell contents and severe tissue damage. However, no means has been available to increase phagocytic clearance of apoptotic cells. We now report that transfection of the macrophage adhesion molecule CD36 into human Bowes melanoma cells specifically conferred greatly increased capacity to ingest apoptotic neutrophils, lymphocytes, and fibroblasts, comparable to that exhibited by macrophages. Furthermore, when CD36 was transfected into another cell type with limited capacity to take up apoptotic bodies, the monkey COS- 7 cell, similar effects were observed. Therefore, CD36 gene transfer can confer "professional" capacity to ingest apoptotic cells upon "amateur" phagocytes. PMID:7536797

  13. HIV-1 Nef Impairs Key Functional Activities in Human Macrophages through CD36 Downregulation

    PubMed Central

    Olivetta, Eleonora; Tirelli, Valentina; Chiozzini, Chiara; Scazzocchio, Beatrice; Romano, Ignazio; Arenaccio, Claudia; Sanchez, Massimo

    2014-01-01

    Monocytes and macrophages utilize the class A and B scavenger receptors to recognize and perform phagocytosis of invading microbes before a pathogen-specific immune response is generated. HIV-1 Nef protein affects the innate immune system impairing oxidative burst response and phagocytic capacity of macrophages. Our data show that exogenous recombinant myristoylated Nef protein induces a marked CD36 downregulation in monocytes from Peripheral Blood Mononuclear Cells, in Monocyte-Derived Macrophages (MDMs) differentiated by cytokines and in MDMs contained in a mixed culture obtained expanding PBMCs under Human Erythroid Massive Amplification condition. Under the latter culture condition we identify three main populations after 6 days of expansion: lymphocytes (37.8±14.7%), erythroblasts (46.7±6.1%) and MDMs (15.7±7.5%). The Nef addition to the cell culture significantly downregulates CD36 expression in MDMs, but not in erythroid cells. Furthermore, CD36 inhibition is highly specific since it does not modify the expression levels of other MDM markers such as CD14, CD11c, CD86, CD68, CD206, Toll-like Receptor 2 and Toll-like Receptor 4. Similar results were obtained in MDMs infected with VSV-G pseudotyped HIV-1-expressing Nef. The reduced CD36 membrane expression is associated with decrease of correspondent CD36 mRNA transcript. Furthermore, Nef-induced CD36 downregulation is linked to both impaired scavenger activity with reduced capability to take up oxidized lipoproteins and to significant decreased phagocytosis of fluorescent beads and GFP-expressing Salmonella tiphymurium. In addition we observed that Nef induces TNF-α release in MDMs. Although these data suggest a possible involvement of TNF-α in mediating Nef activity, our results exclude a possible relationship between Nef-induced TNF-α release and Nef-mediated CD36 downregulation. The present work shows that HIV-1 Nef protein may have a role in the strategies elaborated by HIV-1 to alter pathogen

  14. CD36 Differently Regulates Macrophage Responses to Smooth and Rough Lipopolysaccharide

    PubMed Central

    Biedroń, Rafał; Peruń, Angelika; Józefowski, Szczepan

    2016-01-01

    Lipopolysaccharide (LPS) is the major pathogen-associated molecular pattern of Gram-negative bacterial infections, and includes smooth (S-LPS) and rough (R-LPS) chemotypes. Upon activation by LPS through CD14, TLR4/MD-2 heterodimers sequentially induce two waves of intracellular signaling for macrophage activation: the MyD88-dependent pathway from the plasma membrane and, following internalization, the TRIF-dependent pathway from endosomes. We sought to better define the role of scavenger receptors CD36 and CD204/SR-A as accessory LPS receptors that can contribute to pro-inflammatory and microbicidal activation of macrophages. We have found that CD36 differently regulates activation of mouse macrophages by S-LPS versus R-LPS. The ability of CD36 to substitute for CD14 in loading R-LPS, but not S-LPS onto TLR4/MD-2 allows CD14-independent macrophage responses to R-LPS. Conversely, S-LPS, but not R-LPS effectively stimulates CD14 binding to CD36, which favors S-LPS transfer from CD14 onto TLR4/MD-2 under conditions of low CD14 occupancy with S-LPS in serum-free medium. In contrast, in the presence of serum, CD36 reduces S-LPS binding to TLR4/MD-2 and the subsequent MyD88-dependent signaling, by mediating internalization of S-LPS/CD14 complexes. Additionally, CD36 positively regulates activation of TRIF-dependent signaling by both S-LPS and R-LPS, by promoting TLR4/MD-2 endocytosis. In contrast, we have found that SR-A does not function as a S-LPS receptor. Thus, by co-operating with CD14 in both R- and S-LPS loading onto TLR4/MD-2, CD36 can enhance the sensitivity of tissue-resident macrophages in detecting infections by Gram-negative bacteria. However, in later phases, following influx of serum to the infection site, the CD36-mediated negative regulation of MyD88-dependent branch of S-LPS-induced TLR4 signaling might constitute a mechanism to prevent an excessive inflammatory response, while preserving the adjuvant effect of S-LPS for adaptive immunity. PMID

  15. 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.

  16. CD36 T188G gene polymorphism and severe falciparum malaria in India.

    PubMed

    Das, A; Das, T K; Sahu, U; Das, B P; Kar, S K; Ranjit, M R

    2009-07-01

    Sequestration of parasitized erythrocytes (PE) in the microvasculature contributes directly to the virulence and severe pathology of Plasmodium falciparum malaria. The scavenger receptor CD36 appears to play an important role in PE adherence. Recently several mutations in the CD36 gene have been found to be associated with variability in susceptibility to P. falciparum infection in different ethnic populations. We investigated the possible association of T188G CD36 gene polymorphism with severe clinical manifestations of malaria in 95 adult patients with severe malaria admitted to SCB Medical College Hospital, Cuttack, Orissa, India ('severe' group) and 95 ethnically matched controls attending outpatient clinics at primary health centres ('mild' group). The frequency of the wild-type (T188T) allele of the CD36 gene was 0.91 in the 'severe' group and 0.78 in the 'mild' group of patients, while mutant (T188G) allele frequency was 0.09 in the severe group and 0.22 in the mild group. The Hardy-Weinberg equation indicates that the mutant allele is under selection pressure and disease association analysis shows that the presence of the heterozygote mutant allele renders protection against severe malaria (chi(2)=10.67, odds ratio=3.51, 95% CI 1.67-7.36). PMID:19136129

  17. CD36 Is Essential for Regulation of the Host Innate Response to Staphylococcus aureus α-Toxin-Mediated Dermonecrosis.

    PubMed

    Castleman, Moriah J; Febbraio, Maria; Hall, Pamela R

    2015-09-01

    Staphylococcus aureus is the primary cause of skin and skin structure infections (SSSIs) in the United States. α-Hemolysin (Hla), a pore-forming toxin secreted by S. aureus and a major contributor to tissue necrosis, prompts recruitment of neutrophils critical for host defense against S. aureus infections. However, the failure to clear apoptotic neutrophils can result in damage to host tissues, suggesting that mechanisms of neutrophil clearance are essential to limiting Hla-mediated dermonecrosis. We hypothesized that CD36, a scavenger receptor which facilitates recognition of apoptosing cells, would play a significant role in regulating Hla-mediated inflammation and tissue injury during S. aureus SSSI. In this study, we show that CD36 on macrophages negatively regulates dermonecrosis caused by Hla-producing S. aureus. This regulation is independent of bacterial burden, as CD36 also limits dermonecrosis caused by intoxication with sterile bacterial supernatant or purified Hla. Dermonecrotic lesions of supernatant intoxicated CD36(-/-) mice are significantly larger, with increased neutrophil accumulation and IL-1β expression, compared with CD36(+/+) (wild-type) mice. Neutrophil depletion of CD36(-/-) mice prevents this phenotype, demonstrating the contribution of neutrophils to tissue injury in this model. Furthermore, administration of CD36(+/+) but not CD36(-/-) macrophages near the site of intoxication reduces dermonecrosis, IL-1β production and neutrophil accumulation to levels seen in wild-type mice. This therapeutic effect is reversed by inhibiting actin polymerization in the CD36(+/+) macrophages, supporting a mechanism of action whereby CD36-dependent macrophage phagocytosis of apoptotic neutrophils regulates Hla-mediated dermonecrosis. Taken together, these data demonstrate that CD36 is essential for controlling the host innate response to S. aureus skin infection.

  18. CD36 is essential for regulation of the host innate response to Staphylococcus aureus alpha-toxin-mediated dermonecrosis

    PubMed Central

    Castleman, Moriah J.; Febbraio, Maria; Hall, Pamela R.

    2015-01-01

    Staphylococcus aureus is the primary cause of skin and skin structure infections (SSSI) in the USA. Alpha-hemolysin (Hla), a pore-forming toxin secreted by S. aureus and a major contributor to tissue necrosis, prompts recruitment of neutrophils critical for host defense against S. aureus infections. However, the failure to clear apoptotic neutrophils can result in damage to host tissues, suggesting that mechanisms of neutrophil clearance are essential to limiting Hla-mediated dermonecrosis. We hypothesized that CD36, a scavenger receptor which facilitates recognition of apoptosing cells, would play a significant role in regulating Hla-mediated inflammation and tissue injury during S. aureus SSSI. Here we show that CD36 on macrophages negatively regulates dermonecrosis caused by Hla-producing S. aureus. This regulation is independent of bacterial burden, as CD36 also limits dermonecrosis caused by intoxication with sterile bacterial supernatant or purified Hla. Dermonecrotic lesions of supernatant intoxicated CD36−/− mice are significantly larger, with increased neutrophil accumulation and IL-1β expression, compared to CD36+/+ (wild-type) mice. Neutrophil depletion of CD36−/− mice prevents this phenotype, demonstrating the contribution of neutrophils to tissue injury in this model. Furthermore, administration of CD36+/+, but not CD36−/−, macrophages near the site of intoxication reduces dermonecrosis, IL-1β production and neutrophil accumulation to levels seen in wild-type mice. This therapeutic effect is reversed by inhibiting actin polymerization in the CD36+/+ macrophages, supporting a mechanism of action whereby CD36-dependent macrophage phagocytosis of apoptotic neutrophils regulates Hla-mediated dermonecrosis. Together, these data demonstrate that CD36 is essential for controlling the host innate response to S. aureus skin infection. PMID:26223653

  19. The Effect of Pueraria Lobata/Rehmannia Glutinosa and Exercise on Fatty Acid Transporters Expression in Ovariectomized Rats Skeletal Muscles

    PubMed Central

    Kim, Hye Jin; Yoon, Hae Min; Kwon, Oran; Lee, Won Jun

    2016-01-01

    [Purpose] Pueraria lobata/rehmannia glutinosa (PR) and exercise have been receiving a lot of attention from postmenopausal women, as a result of the side effects of estrogen replacement therapy. However, the effects of PR and exercise on fatty acid transporters (FATPs), which play essential role in fatty acid transport, have not been studied. In this study, we evaluated the effects of PR and aerobic exercise on FATP1, FABPpm and FAT/CD36 expression in ovariectomized rat skeletal muscles. [Methods] Sixty rats were randomly divided into 6 groups: (1)HSV; high fat diet (HFD)+sedentary+vehicle, (2)HSP; HFD+sedentary+PR, (3)HSH; HFD+sedentary+17β-estradiol, (4)HEV; HFD+exercise+vehicle, (5) HEP; HFD+exercise+PR, (6)HEH; HFD+exercise+17β-estradiol. Exercise consisted of treadmill exercise (1-4th week: 15 m/min for 30 min, 5-8th week: 18 m/min for 40 min, 5 times/week). [Results] Exercise does not alter FATP1 and FAT/CD36 gene levels in soleus and plantaris muscles. In contrast, exercise had main effect on up-regulation of FABPpm mRNA expression in both muscles. However, FABPpm level was not increased by exercise combined with treatments, indicative of no additive effects of PR or hormone on FABPpm gene expression. On the other hand, immunohistochemistry result showed that translocation of FATPs proteins to plasma membrane were higher in PR, exercise groups, and exercise combined with PR groups in both muscles. [Conclusion] These result showed that aerobic exercise and PR may help increase fat-oxidation through the induction of FABPpm, a muscle specific transporter, in OVX rat skeletal muscles. In addition, FABPpm expression is possibly regulated post-transcriptionally in exercise, or pre-translationally in PR. PMID:27757385

  20. 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.

  1. 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.

  2. 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

  3. Prostaglandin E2 receptor subtype 2 regulation of scavenger receptor CD36 modulates microglial Aβ42 phagocytosis.

    PubMed

    Li, Xianwu; Melief, Erica; Postupna, Nadia; Montine, Kathleen S; Keene, C Dirk; Montine, Thomas J

    2015-01-01

    Recent studies underline the potential relevance of microglial innate immune activation in Alzheimer disease. Primary mouse microglia that lack prostaglandin E2 receptor subtype 2 (EP2) show decreased innate immune-mediated neurotoxicity and increased amyloid β (Aβ) peptide phagocytosis, features that were replicated in vivo. Here, we tested the hypothesis that scavenger receptor CD36 is an effector of EP2-regulated Aβ phagocytosis. CD36 expression was 143-fold greater in mouse primary microglia than in primary astrocytes. Three different means of suppressing EP2 signaling increased and an agonist of EP2 decreased CD36 expression in primary wild-type microglia. Activation of Toll-like receptor (TLR) 3, TLR4, and TLR7, but not TLR2 or TLR9, reduced primary microglial CD36 transcription and cell surface CD36 protein and reduced Aβ42 phagocytosis as well. At each step, the effects of innate immune activation on CD36 were reversed by at least 50% by an EP2 antagonist, and this partial rescue of microglia Aβ42 phagocytosis was largely mediated by CD36 activity. Finally, we showed in hippocampus of wild-type mice that innate immune activation suppressed CD36 expression by an EP2-dependent mechanism. Taken together with results of others that found brain clearance of Aβ peptides and behavioral improvements mediated by CD36 in mice, regulation of CD36-mediated Aβ phagocytosis by suppression of EP2 signaling may provide a new approach to suppressing some aspects of Alzheimer disease pathogenesis.

  4. OxLDL or TLR2-induced cytokine response is enhanced by oxLDL-independent novel domain on mouse CD36

    PubMed Central

    Xie, ChengHui; Ng, HangPong; Nagarajan, Shanmugam

    2011-01-01

    OxLDL binding to CD36 is shown to result in macrophage activation and foam cell formation that have been implicated in atherosclerosis. However, CD36 has also been shown to induce inflammatory response to other ligands besides oxLDL. During the course of blocking CD36 oxLDL binding function using anti CD36 antibodies, we have identified a novel domain of CD36 that triggers inflammatory response-independent of oxLDL binding. OxLDL bound to the mouse reporter cell line RAW-Blue induced TNF-α and RANTES mRNA and protein expression. Pretreatment of RAW-Blue cells with an anti-mCD36 mAb, JC63.1, an activating mCD36 mAb, surprisingly did not inhibit oxLDL-induced response. Further, binding of this antibody to CD36 alone induced a pro-inflammatory cytokine response in RAW-Blue cells as well as primary mouse macrophages. The induction of cytokine response was specific only to this antibody and was CD36-dependent, since CD36−/− macrophages failed to induce a similar response. The interaction of the antibody to CD36 led to activation of NF-κB and MAP kinase. Notably, a CD36 peptide blocked oxLDL-induced foam cell formation and macrophage activation. However, the activating mCD36 mAb induced macrophage activation was not inhibited by CD36 peptide. Further, activating mCD36 mAb enhanced oxLDL- or TLR2- or TLR4-mediated inflammatory responses. Collectively, our data provide evidence that activating mCD36 mAb binds to a domain different from the oxLDL-binding domain on mouse CD36, and suggest that interaction at this domain may contribute to oxLDL-independent macrophage inflammatory responses that lead to chronic inflammatory diseases. PMID:21281677

  5. 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.

  6. Lack of the scavenger receptor CD36 alters microglial phenotypes after neonatal stroke

    PubMed Central

    Li, Fan; Faustino, Joel; Woo, Moon-Sook; Derugin, Nikita; Vexler, Zinaida S

    2016-01-01

    The stage of brain development at the time of stroke has a major impact on the pathophysiological mechanisms of ischemic damage, including the neuroinflammatory response. Microglial cells have been shown to contribute to acute and sub-chronic injury in adult stroke models, whereas in neonatal rodents we showed that microglial cells serve as endogenous neuroprotectants early following transient middle cerebral artery occlusion (tMCAO), limiting neuroinflammation and injury. In the neonate, microglial depletion or lack of the scavenger receptor CD36 exacerbates injury. In this study we asked if lack of CD36 affects microglial phenotypes after neonatal stroke. Using RT-PCR we characterized the patterns of gene expression in microglia isolated from injured regions following acute tMCAO in postnatal day 10 mice and showed that expression of several pro-inflammatory genes, including Toll-like receptors (TLR), remains largely unaffected in activated microglia in injured regions. Using multiple biochemical assays we demonstrated that lack of CD36 alters several functions of microglia in acutely injured neonatal brain: it further enhances accumulation of the chemokine MCP-1, affects the number of CD11b+/CD45+ cells, along with protein expression of its co-receptor, TLR2, but does not affect accumulation of superoxide in microglia or the cytokines TNFα and IL-1β in injured regions. PMID:26223273

  7. miRNA-133a attenuates lipid accumulation via TR4-CD36 pathway in macrophages.

    PubMed

    Peng, Xiao-Ping; Huang, Lei; Liu, Zhi-Hong

    2016-08-01

    lipid metabolism is the major causes of atherosclerosis. There is increasing evidence that miR-133a plays an important role in atherosclerosis. However, the regulatory mechanism of miR-133a in macrophages is still unclear. Several lines of evidence indicate that loss of TR4 leads to reduce lipid accumulation in liver and adipose tissues, etc, and lesional macrophages-derived TR4 can greatly increase the foam cell formation through increasing the CD36-mediated the uptake of ox-LDL. Interestingly, computational analysis suggests that TR4 may be a target gene of miR-133a. Here, we examined whether miR-133a regulates TR4 expression in ox-LDL-induced mouse RAW 264.7 macrophages, thereby affecting lipid accumulation. Using ox-LDL-treatment RAW 264.7 macrophages transfected with miR-133a mimics or inhibitors, we have showed that miR-133a can directly regulate the expression of TR4 in RAW 264.7 cells, thereby attenuates CD36-medide lipid accumulation. Furthermore, our studies suggest an additional explanation for the regulatory mechanism of miR-133a regulation to its functional target, TR4 in RAW 264.7 macrophages. Thus, our findings suggest that miR-133a may regulate lipid accumulation in ox-LDL-stimulated RAW 264.7 macrophages via TR4-CD36 pathway.

  8. Structural and functional characterization of the mouse fatty acid translocase promoter: activation during adipose differentiation.

    PubMed Central

    Teboul, L; Febbraio, M; Gaillard, D; Amri, E Z; Silverstein, R; Grimaldi, P A

    2001-01-01

    Fatty acid translocase (FAT/CD36) is a cell-surface glycoprotein that functions as a receptor/transporter for long-chain fatty acids (LCFAs), and interacts with other protein and lipid ligands. FAT/CD36 is expressed by various cell types, including platelets, monocytes/macrophages and endothelial cells, and tissues with an active LCFA metabolism, such as adipose, small intestine and heart. FAT/CD36 expression is induced during adipose cell differentiation and is transcriptionally up-regulated by LCFAs and thiazolidinediones in pre-adipocytes via a peroxisome-proliferator-activated receptor (PPAR)-mediated process. We isolated and analysed the murine FAT/CD36 promoter employing C(2)C(12)N cells directed to differentiate to either adipose or muscle. Transient transfection studies revealed that the 309 bp upstream from the start of exon 1 confer adipose specific activity. Sequence analysis of this DNA fragment revealed the presence of two imperfect direct repeat-1 elements. Electrophoretic mobility-shift assay demonstrated that these elements were peroxisome-proliferator-responsive elements (PPREs). Mutagenesis and transfection experiments indicated that both PPREs co-operate to drive strong promoter activity in adipose cells. We conclude that murine FAT/CD36 expression in adipose tissue is dependent upon transcriptional activation via PPARs through binding to two PPREs located at -245 to -233 bp and -120 to -108 bp from the transcription start site. PMID:11716758

  9. Reduced uptake of oxidized low density lipoproteins in monocyte-derived macrophages from CD36-deficient subjects.

    PubMed Central

    Nozaki, S; Kashiwagi, H; Yamashita, S; Nakagawa, T; Kostner, B; Tomiyama, Y; Nakata, A; Ishigami, M; Miyagawa, J; Kameda-Takemura, K

    1995-01-01

    To clarify the physiological roles of CD36 as an oxidized low density lipoprotein (OxLDL) receptor, we analyzed the monocyte-derived macrophages from normal and two CD36-deficient subjects, since we identified the molecular abnormalities (Kashiwagi, H., Y. Tomiyama, Y. Kosugi, M. Shiraga, R. H. Lipsky, Y. Kanayama, Y. Kurata, and Y. Matsuzawa 1994. Blood. 83:3545-3552; and Kashiwagi, H., Y. Tomiyama, S. Honda, S. Kosugi, M. Shiraga, N. Nagao, S. Sekiguchi, Y. Kanayama, Y. Kurata, and Y. Matsuzawa. 1995. J. Clin. Invest. 95:1040-1046). Scatchard analysis of 125I-OxLDL binding showed a linear plot and the maximum binding was lower by approximately 40% in the macrophages from subjects with CD36 deficiency than those from normal controls. Competition studies showed that the uptake of 125I-OxLDL was suppressed by OKM5, an antibody against CD36, by 53% in normal control macrophages, but not in the CD36-deficient macrophages. After incubation with OxLDL for 24 h, cholesteryl ester mass accumulation was reduced by approximately 40% in the macrophages from CD36-deficient subjects than those from normal controls. These results suggest that CD36 is one of the physiological receptors for OxLDL. Since specific binding of OxLDL was only reduced by approximately 40% in spite of the complete deficiency of CD36, several other receptors also may have some role in OxLDL uptake. Further studies will be needed to assess the quantitative role of CD36 in foam cell formation in vivo. Images PMID:7560077

  10. Identification of CD13+CD36+ cells as a common progenitor for erythroid and myeloid lineages in human bone marrow

    PubMed Central

    Chen, Ling; Gao, Zhigang; Zhu, Jianqiong; Rodgers, Griffin P.

    2008-01-01

    Objective To identify bi-potential precursor cells of erythroid and myeloid development in human bone marrow. Materials and Methods Cells co-expressing CD13 and CD36 (CD13+CD36+) were investigated by analyzing cell surface marker expression during erythroid development (induced with a combination of cytokines plus erythropoietin [EPO]), or myeloid development (induced with the same cocktail of cytokines plus granulocyte-colony stimulating factor [G-CSF]) of bone marrow derived CD133 cells in liquid cultures. CD13+CD36+ subsets were also isolated on the 14th day of cultures and further evaluated for their hematopoietic clonogenic capacity in methylcellulose. Results Colony-forming analysis of sorted CD13+CD36+ cells of committed erythroid and myeloid lineages demonstrated that these cells were able to generate erythroid, granulocyte, and mixed erythroid –granulocyte colonies. In contrast, CD13+CD36− or CD13−CD36+ cells exclusively committed to granulocyte/monocyte or erythroid colonies, respectively, but failed to form mixed erythroid –granulocyte colonies; no colonies were detected in CD13−CD36− cells with lineage-supporting cytokines. In addition, our data confirmed that EPO induced both erythroid and myeloid commitment, while G-CSF only supported the differentiation of the myeloid lineage. Conclusions The present data identify some CD13+CD36+ cells as bi-potential precursors of erythroid and myeloid commitment in normal hematopoiesis. They provide a physiological explanation for the cell identification of myeloid and erythroid lineages observed in hematopoietic diseases. This unique fraction of CD13+CD36+ cells may be useful for further studies on regulating erythroid and myeloid differentiation during normal and malignant hematopoiesis. PMID:17588473

  11. 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.

  12. 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

  13. Evolutionarily conserved recognition and innate immunity to fungal pathogens by the scavenger receptors SCARF1 and CD36

    PubMed Central

    Mylonakis, Eleftherios; Tampakakis, Emmanouil; Colvin, Richard A.; Seung, Edward; Puckett, Lindsay; Tai, Melissa F.; Stewart, Cameron R.; Pukkila-Worley, Read; Hickman, Suzanne E.; Moore, Kathryn J.; Calderwood, Stephen B.; Hacohen, Nir; Luster, Andrew D.; El Khoury, Joseph

    2009-01-01

    Receptors involved in innate immunity to fungal pathogens have not been fully elucidated. We show that the Caenorhabditis elegans receptors CED-1 and C03F11.3, and their mammalian orthologues, the scavenger receptors SCARF1 and CD36, mediate host defense against two prototypic fungal pathogens, Cryptococcus neoformans and Candida albicans. CED-1 and C03F11.1 mediated antimicrobial peptide production and were necessary for nematode survival after C. neoformans infection. SCARF1 and CD36 mediated cytokine production and were required for macrophage binding to C. neoformans, and control of the infection in mice. Binding of these pathogens to SCARF1 and CD36 was β-glucan dependent. Thus, CED-1/SCARF1 and C03F11.3/CD36 are β-glucan binding receptors and define an evolutionarily conserved pathway for the innate sensing of fungal pathogens. PMID:19237602

  14. 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.

  15. Nrf2, a PPARγ Alternative Pathway to Promote CD36 Expression on Inflammatory Macrophages: Implication for Malaria

    PubMed Central

    Olagnier, David; Lavergne, Rose-Anne; Meunier, Etienne; Lefèvre, Lise; Dardenne, Christophe; Aubouy, Agnès; Benoit-Vical, Françoise; Ryffel, Bernhard; Coste, Agnès; Berry, Antoine; Pipy, Bernard

    2011-01-01

    CD36 is the major receptor mediating nonopsonic phagocytosis of Plasmodium falciparum-parasitized erythrocytes by macrophages. Its expression on macrophages is mainly controlled by the nuclear receptor PPARγ. Here, we demonstrate that inflammatory processes negatively regulate CD36 expression on human and murine macrophages, and hence decrease Plasmodium clearance directly favoring the worsening of malaria infection. This CD36 downregulation in inflammatory conditions is associated with a failure in the expression and activation of PPARγ. Interestingly, using siRNA mediating knock down of Nrf2 in macrophages or Nrf2- and PPARγ-deficient macrophages, we establish that in inflammatory conditions, the Nrf2 transcription factor controls CD36 expression independently of PPARγ. In these conditions, Nrf2 activators, but not PPARγ ligands, enhance CD36 expression and CD36-mediated Plasmodium phagocytosis. These results were confirmed in human macrophages and in vivo where only Nrf2 activators improve the outcome of severe malaria. Collectively, this report highlights that the Nrf2 transcription factor could be an alternative target to PPARγ in the control of severe malaria through parasite clearance. PMID:21949655

  16. [Oxidized low density lipoprotein induces macrophage endoplasmic reticulum stress via CD36.].

    PubMed

    Yao, Shu-Tong; Sang, Hui; Yang, Na-Na; Kang, Li; Tian, Hua; Zhang, Ying; Song, Guo-Hua; Qin, Shu-Cun

    2010-10-25

    The purpose of the present study is to explore the effect of oxidized low density lipoprotein (ox-LDL) on the induction of endoplasmic reticulum stress (ERS) and the underlying mechanisms in ox-LDL-induced macrophage foam-forming process. RAW264.7 macrophages were cultured in DMEM medium containing 10% fetal bovine serum, and then treated with ox-LDL (25, 50 and 100 mg/L), anti-CD36 monoclonal antibody+ox-LDL and tunicamycin (TM), respectively. After incubation for 24 h, the cells were collected. The cellular lipid accumulation was showed by oil red O staining and the content of cellular total cholesterol was quantified by enzymatic colorimetry. The expression of glucose-regulated protein 94 (GRP94), a molecular marker of ERS, was determined by immunocytochemistry assay. The levels of GRP94 protein, phosphorylated inositol-requiring enzyme 1 (p-IRE1) and X box binding protein 1 (XBP1) in RAW264.7 cells were detected by Western blotting. The results indicated that after incubation with ox-LDL (25, 50 and 100 mg/L) for 24 h, a large amount of lipid droplets were found in the cytoplasm, and the contents of cellular total cholesterol were increased by 2.1, 2.8 and 3.1 folds compared with the control, respectively. Anti-CD36 antibody decreased markedly the cellular lipid accumulation induced by ox-LDL at 100 mg/L. Both ox-LDL and TM, a specific ERS inducer, could up-regulate the protein expression of GRP94 in a dose-dependent manner. Furthermore, p-IRE1 and XBP1, two key components of the unfolded protein response, were also significantly induced by the treatment with ox-LDL. The up-regulations of the three proteins induced by ox-LDL were inhibited significantly when the macrophages were pre-incubated with anti-CD36 antibody. These results suggest that ox-LDL may induce ERS in a dose-dependent way and subsequently activate the unfolded protein response signaling pathway in RAW264.7 macrophages, which is potentially mediated by scavenger receptor CD36. PMID:20945046

  17. 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

  18. Rspo2 suppresses CD36-mediated apoptosis in oxidized low density lipoprotein-induced macrophages.

    PubMed

    Yan, Hui; Wang, Shuai; Li, Zhenwei; Sun, Zewei; Zan, Jie; Zhao, Wenting; Pan, Yanyun; Wang, Zhen; Wu, Mingjie; Zhu, Jianhua

    2016-10-01

    Oxidized low density lipoprotein (oxLDL)-induced apoptosis of macrophages contributes to the formation of atherosclerotic plaques. R‑spondin 2 (Rspo2), a member of the cysteine‑rich secreted proteins, has been shown to be involved in the oncogenesis of several types of cancer. It has also been found to be abundantly expressed among the four R‑spondin members in macrophages. The present study was performed to determine whether Rspo2 is involved in the ox‑LDL‑induced apoptosis of macrophages. It was identified that Rspo2 inhibited oxLDL‑induced apoptosis in the presence of endoplasmic reticulum (ER) stress activator using flow cytometry. In addition, Rspo2 was observed to suppress oxLDL‑induced ER stress and reactive oxygen species production as demonstrated by western blotting. Furthermore, analysis of the role of Rspo2 in macrophage lipid uptake identified that Rspo2 negatively regulated the Dil‑oxLDL uptake by inhibiting the expression of cluster of differentiation (CD)36, through the transcription factor, peroxisome proliferator‑activated receptor (PPAR)‑γ. The manipulation of Rspo2 had a direct effect on PPAR‑γ nuclear translocation. In addition, chromatin immunoprecipitation analysis revealed that Rspo2 manipulation led to regulation of the direct binding between PPAR‑γ and CD36. In conclusion, Rspo2 was found to have a negative regulatory effect during oxLDL‑induced macrophage apoptosis by regulating lipid uptake. PMID:27571704

  19. Rspo2 suppresses CD36-mediated apoptosis in oxidized low density lipoprotein-induced macrophages

    PubMed Central

    Yan, Hui; Wang, Shuai; Li, Zhenwei; Sun, Zewei; Zan, Jie; Zhao, Wenting; Pan, Yanyun; Wang, Zhen; Wu, Mingjie; Zhu, Jianhua

    2016-01-01

    Oxidized low density lipoprotein (oxLDL)-induced apoptosis of macrophages contributes to the formation of atherosclerotic plaques. R-spondin 2 (Rspo2), a member of the cysteine-rich secreted proteins, has been shown to be involved in the oncogenesis of several types of cancer. It has also been found to be abundantly expressed among the four R-spondin members in macrophages. The present study was performed to determine whether Rspo2 is involved in the ox-LDL-induced apoptosis of macrophages. It was identified that Rspo2 inhibited oxLDL-induced apoptosis in the presence of endoplasmic reticulum (ER) stress activator using flow cytometry. In addition, Rspo2 was observed to suppress oxLDL-induced ER stress and reactive oxygen species production as demonstrated by western blotting. Furthermore, analysis of the role of Rspo2 in macrophage lipid uptake identified that Rspo2 negatively regulated the Dil-oxLDL uptake by inhibiting the expression of cluster of differentiation (CD)36, through the transcription factor, peroxisome proliferator-activated receptor (PPAR)-γ. The manipulation of Rspo2 had a direct effect on PPAR-γ nuclear translocation. In addition, chromatin immunoprecipitation analysis revealed that Rspo2 manipulation led to regulation of the direct binding between PPAR-γ and CD36. In conclusion, Rspo2 was found to have a negative regulatory effect during oxLDL-induced macrophage apoptosis by regulating lipid uptake. PMID:27571704

  20. 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

  1. Inhibition of Glutathione Production Induces Macrophage CD36 Expression and Enhances Cellular-oxidized Low Density Lipoprotein (oxLDL) Uptake.

    PubMed

    Yang, Xiaoxiao; Yao, Hui; Chen, Yuanli; Sun, Lei; Li, Yan; Ma, Xingzhe; Duan, Shengzhong; Li, Xiaoju; Xiang, Rong; Han, Jihong; Duan, Yajun

    2015-09-01

    The glutathione (GSH)-dependent antioxidant system has been demonstrated to inhibit atherosclerosis. Macrophage CD36 uptakes oxidized low density lipoprotein (oxLDL) thereby facilitating foam cell formation and development of atherosclerosis. It remains unknown if GSH can influence macrophage CD36 expression and cellular oxLDL uptake directly. Herein we report that treatment of macrophages with l-buthionine-S,R-sulfoximine (BSO) decreased cellular GSH production and ratios of GSH to glutathione disulfide (GSH/GSSG) while increasing production of reactive oxygen species. Associated with decreased GSH levels, macrophage CD36 expression was increased, which resulted in enhanced cellular oxLDL uptake. In contrast, N-acetyl cysteine and antioxidant enzyme (catalase or superoxide dismutase) blocked BSO-induced CD36 expression as well as oxLDL uptake. In vivo, administration of mice with BSO increased CD36 expression in peritoneal macrophages and kidneys. BSO had no effect on CD36 mRNA expression and promoter activity but still induced CD36 protein expression in macrophages lacking peroxisome proliferator-activated receptor γ expression, suggesting it induced CD36 expression at the translational level. Indeed, we determined that BSO enhanced CD36 translational efficiency. Taken together, our study demonstrates that cellular GSH levels and GSH/GSSG status can regulate macrophage CD36 expression and cellular oxLDL uptake and demonstrate an important anti-atherogenic function of the GSH-dependent antioxidant system by providing a novel molecular mechanism.

  2. Inhibition of Glutathione Production Induces Macrophage CD36 Expression and Enhances Cellular-oxidized Low Density Lipoprotein (oxLDL) Uptake*

    PubMed Central

    Yang, Xiaoxiao; Yao, Hui; Chen, Yuanli; Sun, Lei; Li, Yan; Ma, Xingzhe; Duan, Shengzhong; Li, Xiaoju; Xiang, Rong; Han, Jihong; Duan, Yajun

    2015-01-01

    The glutathione (GSH)-dependent antioxidant system has been demonstrated to inhibit atherosclerosis. Macrophage CD36 uptakes oxidized low density lipoprotein (oxLDL) thereby facilitating foam cell formation and development of atherosclerosis. It remains unknown if GSH can influence macrophage CD36 expression and cellular oxLDL uptake directly. Herein we report that treatment of macrophages with l-buthionine-S,R-sulfoximine (BSO) decreased cellular GSH production and ratios of GSH to glutathione disulfide (GSH/GSSG) while increasing production of reactive oxygen species. Associated with decreased GSH levels, macrophage CD36 expression was increased, which resulted in enhanced cellular oxLDL uptake. In contrast, N-acetyl cysteine and antioxidant enzyme (catalase or superoxide dismutase) blocked BSO-induced CD36 expression as well as oxLDL uptake. In vivo, administration of mice with BSO increased CD36 expression in peritoneal macrophages and kidneys. BSO had no effect on CD36 mRNA expression and promoter activity but still induced CD36 protein expression in macrophages lacking peroxisome proliferator-activated receptor γ expression, suggesting it induced CD36 expression at the translational level. Indeed, we determined that BSO enhanced CD36 translational efficiency. Taken together, our study demonstrates that cellular GSH levels and GSH/GSSG status can regulate macrophage CD36 expression and cellular oxLDL uptake and demonstrate an important anti-atherogenic function of the GSH-dependent antioxidant system by providing a novel molecular mechanism. PMID:26187465

  3. Circulating CD36 and fractalkine levels are associated with vulnerable plaque progression in patients with unstable angina pectoris.

    PubMed

    Li, Rui Jian; Yang, Ming; Li, Ji Fu; Xue, Li; Chen, Yu Guo; Chen, Wen Qiang

    2014-11-01

    The chemokine, fractalkine, independently enhances the vulnerability of coronary atherosclerotic plaques. The present study investigated the combined effects of CD36 and fractalkine on coronary plaque progression in patients with unstable angina pectoris. In the present study, 120 unstable angina pectoris patients undergoing coronary angiography and intravascular ultrasound were divided into two groups: an intermediate lesion group (lumen diameter stenosis 50-70%, 80 patients) and a severe lesion group (at least one lesion with lumen diameter stenosis > 70%, 40 patients). The control group consisted of 40 healthy age- and sex-matched subjects. Concentrations of CD36 and fractalkine were measured by enzyme-linked immunosorbent assay. Major adverse cardiovascular events were monitored over a 2-year follow up. Intravascular ultrasound showed that patients with severe lesions had more calcified and mixed plaques, and a larger plaque area and plaque burden than patients with intermediate lesions (P < 0.05-0.01). More patients with severe lesions underwent stent deployment (P < 0.05) than those with intermediate lesions. CD36 and fractalkine concentrations were significantly higher in the severe lesion patients (P < 0.05), and both had significant positive correlations (P < 0.05) with the plaque burden of atherosclerotic lesions. Using the matched nested case-control study, we found that CD36 and fractalkine levels were higher in patients with recurrent major adverse cardiovascular events than controls (P < 0.05). In conclusion, CD36 and fractalkine both promote, and might synergistically enhance, the progression of coronary atherosclerotic plaques.

  4. 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

  5. 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

  6. 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

  7. 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

  8. CD36-Dependent 7-Ketocholesterol Accumulation in Macrophages Mediates Progression of Atherosclerosis in Response to Chronic Air Pollution Exposure

    PubMed Central

    Maiseyeu, Andrei; Gopalakrishnan, Bhavani; Villamena, Frederick A.; Chen, Lung-Chi; Harkema, Jack R; Sun, Qinghua; Rajagopalan, Sanjay

    2014-01-01

    Rationale Air pollution exposure has been shown to potentiate plaque progression in humans and animals. Our previous studies have suggested a role for oxidized lipids in mediating adverse vascular effect of air pollution. However, the types of oxidized lipids formed in response to air pollutants and how this occurs and their relevance to atherosclerosis is not fully understood. Objective To investigate the mechanisms by which particulate matter< 2.5μm (PM2.5) induces progression of atherosclerosis. Methods and Results Atherosclerosis-prone ApoE−/− or LDLR−/− mice were exposed to filtered air or concentrated ambient PM2.5 using a versatile aerosol concentrator enrichment system for 6 months. PM2.5 increased 7-ketocholesterol (7-KCh), an oxidatively modified form of cholesterol, in plasma IDL/LDL fraction and in aortic plaque concomitant with progression of atherosclerosis and increased CD36 expression in plaque-macrophages from PM2.5-exposed mice. Macrophages isolated from PM2.5-exposed mice displayed increased uptake of oxidized lipids without alterations in their efflux capacity. Consistent with these finding, CD36-positive macrophages displayed a heightened capacity for oxidized lipid uptake. Deficiency of CD36 on hematopoietic cells diminished the effect of air pollution on 7-KCh accumulation, foam cell formation, and atherosclerosis. Conclusions Our results suggest a potential role for CD36-mediated abnormal accumulations of oxidized lipids such as 7-KCh in air pollution induced atherosclerosis progression. PMID:25186795

  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. Ionizing Radiation Induces Macrophage Foam Cell Formation and Aggregation Through JNK-Dependent Activation of CD36 Scavenger Receptors

    SciTech Connect

    Katayama, Ikuo; Hotokezaka, Yuka; Matsuyama, Toshifumi; Sumi, Tadateru; Nakamura, Takashi

    2008-03-01

    Purpose: Irradiated arteries of cancer patients can be associated with atherosclerosis-like lesions containing cholesterol-laden macrophages (foam cells). Endothelial cell damage by irradiation does not completely explain the foam cell formation. We investigated the possible underlying mechanisms for ionizing radiation (IR)-induced foam cell formation. Methods and Materials: Human peripheral blood monocytes were activated by macrophage colony-stimulating factor and then treated with varying doses of IR in vitro in the absence of endothelial cells. Scavenger receptor expression and foam cell formation of IR-treated macrophages were investigated in the presence or absence of oxidized low-density lipoprotein. We also assessed the importance of mitogen-activated protein kinase activity in the macrophage colony-stimulating factor-activated human monocytes (macrophages) for the foam cell formation. Results: We found that IR treatment of macrophage colony-stimulating factor-activated human peripheral blood monocytes resulted in the enhanced expression of CD36 scavenger receptors and that cholesterol accumulated in the irradiated macrophages with resultant foam cell formation in the presence of oxidized low-density lipoprotein. Furthermore, when cultured on collagen gels, human macrophages formed large foam cell aggregates in response to IR. Antibodies against CD36 inhibited the IR-induced foam cell formation and aggregation, indicating that the IR-induced foam cell formation and the subsequent aggregation are dependent on functional CD36. In addition, we found that IR of human macrophages resulted in c-Jun N-terminal kinase activation and that c-Jun N-terminal kinase inhibition suppressed IR-induced CD36 expression and the subsequent foam cell formation and aggregation. Conclusion: Taken together, these results suggest that IR-induced foam cell formation is mediated by c-Jun N-terminal kinase-dependent CD36 activation.

  11. 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.

  12. 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.

  13. Effect of tachycardia on lipid metabolism and expression of fatty acid transporters in heart ventricles of the rat.

    PubMed

    Wojcik, B; Harasim, E; Zabielski, P; Chabowski, A; Gorski, J

    2015-10-01

    Tachycardia increases oxidation of the plasma-borne long chain fatty acids in the heart. The aim of the present study was to examine effect of tachycardia on: 1) the total level of free fatty acids, diacylglycerols, triacylglycerols and phospholipids in both heart ventricles; 2) (14)C-palmitate incorporation in the lipid fractions; 3) expression of fatty acid and glucose transporters in the ventricles. Tachycardia was induced in anesthetized rats by electrical atrial pacing at the rate of 600/min. Samples of the left (LV) and right (RV) ventricle were taken after 30 and 60 min pacing. The level free fatty acids, diacylglycerols, triacylglycerols and phospholipids was determined by means of gas-liquid chromatography and (14)C-palmitate incorporation by liquid scintillation counting, respectively. Expression of fatty acid- and glucose-transporters was determined using Western blot technique. In LV, 30min pacing increased the content of diacylglycerols whereas the content of other lipids remained stable. After 60 min of pacing the levels of the examined lipid fractions did not differ from the respective control values. In RV, the content of diacylglycerols and triacylglycerols was reduced both after 30 and 60 min pacing. Tachycardia also affected incorporation of (14)C-palmitate in lipid fractions of goth ventricles. 30 min pacing up-regulated plasmalemmal expression of FAT/CD36 (fatty acid translocase) in both ventricles and reduced its microsomal expression in LV. After 60 min pacing they did not differ from the respective control values. Plasmalemmal expression of FATP-1 (fatty acid transport protein 1) increased and its microsomal expression decreased in RV after 30 min pacing. After 60 min pacing the plasmalemmal FATP-1 expression remained elevated whereas the microsomal expression did not differ from the control value. Pacing did not affect or expression of FABPpm (plasma membrane associated fatty acid binding protein) in either plasma membranes and microsomal

  14. Effect of tachycardia on lipid metabolism and expression of fatty acid transporters in heart ventricles of the rat.

    PubMed

    Wojcik, B; Harasim, E; Zabielski, P; Chabowski, A; Gorski, J

    2015-10-01

    Tachycardia increases oxidation of the plasma-borne long chain fatty acids in the heart. The aim of the present study was to examine effect of tachycardia on: 1) the total level of free fatty acids, diacylglycerols, triacylglycerols and phospholipids in both heart ventricles; 2) (14)C-palmitate incorporation in the lipid fractions; 3) expression of fatty acid and glucose transporters in the ventricles. Tachycardia was induced in anesthetized rats by electrical atrial pacing at the rate of 600/min. Samples of the left (LV) and right (RV) ventricle were taken after 30 and 60 min pacing. The level free fatty acids, diacylglycerols, triacylglycerols and phospholipids was determined by means of gas-liquid chromatography and (14)C-palmitate incorporation by liquid scintillation counting, respectively. Expression of fatty acid- and glucose-transporters was determined using Western blot technique. In LV, 30min pacing increased the content of diacylglycerols whereas the content of other lipids remained stable. After 60 min of pacing the levels of the examined lipid fractions did not differ from the respective control values. In RV, the content of diacylglycerols and triacylglycerols was reduced both after 30 and 60 min pacing. Tachycardia also affected incorporation of (14)C-palmitate in lipid fractions of goth ventricles. 30 min pacing up-regulated plasmalemmal expression of FAT/CD36 (fatty acid translocase) in both ventricles and reduced its microsomal expression in LV. After 60 min pacing they did not differ from the respective control values. Plasmalemmal expression of FATP-1 (fatty acid transport protein 1) increased and its microsomal expression decreased in RV after 30 min pacing. After 60 min pacing the plasmalemmal FATP-1 expression remained elevated whereas the microsomal expression did not differ from the control value. Pacing did not affect or expression of FABPpm (plasma membrane associated fatty acid binding protein) in either plasma membranes and microsomal

  15. Association between rs1761667 polymorphism of CD36 gene and risk of coronary atherosclerosis in Egyptian population

    PubMed Central

    Arafa, Usama Ahmed; Sabet, Eman A.; Salama, Eman; El Sharawy, Ahmed; Elbadry, Mahmoud I.

    2016-01-01

    Background Recent studies have demonstrated that CD36 is involved in the progression of atherosclerosis. Associations between rs1761667 polymorphisms of the CD36 gene and susceptibility to coronary artery disease (CAD) are not obvious. Methods We studied the relationship between single nucleotide polymorphisms (SNPs), rs1761667 of CD36 gene and the risk of coronary atherosclerosis in a case-control study composed of 71 CAD patients and 76 healthy controls by assessment of allele frequencies and genotype distributions using real-time polymerase chain reaction (PCR) and the allele discrimination technique. Additionally, we detected CD36 expression by flow cytometry. Results The distribution of rs1761667 genotypes between the two groups was significantly different (P<0.001), with the frequency of the AG genotype being significantly higher in the CAD group than in the control group (P<0.001). The expression level of CD36 in the CAD group was significantly higher than that in the control group (P<0.001), with significant differences in the CAD patients with an AG genotype compared with those with an AA and GG genotype (P<0.001). The plasma levels (mg/dL) of low-density lipoprotein (LDL) in the CAD group were much higher than that in the control group (P<0.001). On the other hand, the plasma LDL levels in CAD patients with the AG genotype were remarkably higher than those with the GG and AA genotypes (P=0.046) and AG genotype was significantly more prevalent among type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) patients (P<0.05). After adjusted logistic regression analysis, the AG genotype of rs1761667 was associated with an increased risk of CAD (OR=17.97, 95% CI, 3.19–87.85, P=0.001). Conclusions The AG genotype of the rs1761667 polymorphism in the CD36 gene may be involved in CAD pathogenesis as well as increased body mass index (BMI), T2DM and MetS in the Sohag population of Egypt. PMID:27054101

  16. A novel lipopeptide from skin commensal activates TLR2/CD36-p38 MAPK signaling to increase antibacterial defense against bacterial infection.

    PubMed

    Li, Dongqing; Lei, Hu; Li, Zhiheng; Li, Hongquan; Wang, Yue; Lai, Yuping

    2013-01-01

    Staphylococcus epidermidis (S.epidermidis) plays important protective roles by directly producing or by stimulating hosts to produce antimicrobial peptides (AMPs) against pathogenic infections. Although several AMPs from S.epidermidis have been identified, molecules that stimulate hosts to produce AMPs remain largly unknown. Here we demonstrate that a new lipopeptide (named LP01) purified from S.epidermidis culture media has a unique structure with heneicosanoic acid (21 carbons) binding to lysine(11) of a peptide chain. In vitro LP01 increased the expression of β-defensin 2(hBD2) and hBD3 in neonatal human epidermal keratinocytes(NHEK), leading to increased capacity of cell lysates to inhibit the growth of S.aureus. In vivo LP01 induced the expression of mouse β-defensin 4(mBD4) to decrease the survival of local S.aureus in skin and systemic S.aureus survival in liver. The induction of beta-defensins by LP01 was dependent on TLR2 as Tlr2-deficient mice had decreased mBD4. Furthermore, knockdown of CD36 decreased the expression of hBD2 and hBD3, and p38 MAPK inhibitor significantly inhibited the expression of hBDs induced by LP01.Taken together, these findings demonstrate that lipopeptide LP01 from normal commensal S.epidermidis increases antimicrobial peptide hBD2 and hBD3 expression via the activation of TLR2/CD36-p38 MAPK, thus enhancing antimicrobial defense against pathogenic infections.

  17. Myocardial macronutrient transporter adaptations in the adult pregestational female intrauterine and postnatal growth-restricted offspring

    PubMed Central

    Abbasi, Afshan; Thamotharan, Manikkavasagar; Shin, Bo-Chul; Jordan, Maria C.; Roos, Kenneth P.; Stahl, Andreas

    2012-01-01

    Associations between exponential childhood growth superimposed on low birth weight and adult onset cardiovascular disease with glucose intolerance/type 2 diabetes mellitus exist in epidemiological investigations. To determine the metabolic adaptations that guard against myocardial failure on subsequent exposure to hypoxia, we compared with controls (CON), the effect of intrauterine (IUGR), postnatal (PNGR), and intrauterine and postnatal (IPGR) calorie and growth restriction (n = 6/group) on myocardial macronutrient transporter (fatty acid and glucose) -mediated uptake in pregestational young female adult rat offspring. A higher myocardial FAT/CD36 protein expression in IUGR, PNGR, and IPGR, with higher FATP1 in IUGR, FATP6 in PNGR, FABP-c in PNGR and IPGR, and no change in GLUT4 of all groups was observed. These adaptive macronutrient transporter protein changes were associated with no change in myocardial [3H]bromopalmitate accumulation but a diminution in 2-deoxy-[14C]glucose uptake. Examination of the sarcolemmal subfraction revealed higher basal concentrations of FAT/CD36 in PNGR and FATP1 and GLUT4 in IUGR, PNGR, and IPGR vs. CON. Exogenous insulin uniformly further enhanced sarcolemmal association of these macronutrient transporter proteins above that of basal, with the exception of insulin resistance of FATP1 and GLUT4 in IUGR and FAT/CD36 in PNGR. The basal sarcolemmal macronutrient transporter adaptations proved protective against subsequent chronic hypoxic exposure (7 days) only in IUGR and PNGR, with notable deterioration in IPGR and CON of the echocardiographic ejection fraction. We conclude that the IUGR and PNGR pregestational adult female offspring displayed a resistance to insulin-induced translocation of FATP1, GLUT4, or FAT/CD36 to the myocardial sarcolemma due to preexistent higher basal concentrations. This basal adaptation of myocardial macronutrient transporters ensured adequate fatty acid uptake, thereby proving protective against chronic

  18. Low Levels of CD36 in Peripheral Blood Monocytes in Subclinical Atherosclerosis in Rheumatoid Arthritis: A Cross-Sectional Study in a Mexican Population

    PubMed Central

    Gómez-Bañuelos, Eduardo; Martín-Márquez, Beatriz Teresita; Martínez-García, Erika Aurora; Figueroa-Sanchez, Mauricio; Nuñez-Atahualpa, Lourdes; Rocha-Muñoz, Alberto Daniel; Sánchez-Hernández, Pedro Ernesto; Navarro-Hernandez, Rosa Elena; Madrigal-Ruiz, Perla Monserrat; Saldaña-Millan, Adan Alberto; Duran-Barragan, Sergio; Gonzalez-Lopez, Laura; Gamez-Nava, Jorge Ivan; Vázquez-Del Mercado, Mónica

    2014-01-01

    Patients with rheumatoid arthritis (RA) have a higher risk for atherosclerosis. There is no clinical information about scavenger receptor CD36 and the development of subclinical atherosclerosis in patients with RA. The aim of this study was to evaluate the association between membrane expression of CD36 in peripheral blood mononuclear cells (PBMC) and carotid intima-media thickness (cIMT) in patients with RA. Methods. We included 67 patients with RA from the Rheumatology Department of Hospital Civil “Dr. Juan I. Menchaca,” Guadalajara, Jalisco, Mexico. We evaluated the cIMT, considering subclinical atherosclerosis when >0.6 mm. Since our main objective was to associate the membrane expression of CD36 with subclinical atherosclerosis, other molecules related with cardiovascular risk such as ox-LDL, IL-6, and TNFα were tested. Results. We found low CD36 membrane expression in PBMC from RA patients with subclinical atherosclerosis (P < 0.001). CD36 mean fluorescence intensity had negative correlations with cIMT (r = −0.578, P < 0.001), ox-LDL (r = −0.427, P = 0.05), TNFα (r = −0.729, P < 0.001), and IL-6 (r = −0.822, P < 0.001). Conclusion. RA patients with subclinical atherosclerosis showed low membrane expression of CD36 in PBMC and increased serum proinflammatory cytokines. Further studies are needed to clarify the regulation of CD36 in RA. PMID:25006585

  19. Activation of monocytes and platelets by monoclonal antibodies or malaria-infected erythrocytes binding to the CD36 surface receptor in vitro.

    PubMed Central

    Ockenhouse, C F; Magowan, C; Chulay, J D

    1989-01-01

    The CD36 leukocyte differentiation antigen, recognized by MAbs OKM5 and OKM8 and found on human monocytes and endothelial cells, has been implicated as a sequestration receptor for erythrocytes infected with the human malaria parasite Plasmodium falciparum (IRBC). CD36 is also expressed on platelets and appears to be identical to platelet glycoprotein IV. We investigated receptor activation of monocytes and platelets by anti-CD36 MAbs and by IRBC. Incubation of human monocytes with anti-CD36 MAbs or IRBC resulted in stimulation of the respiratory burst as measured by reduction of nitroblue tetrazolium and generation of chemiluminescence. Incubation of human platelets with anti-CD36 MAbs resulted in platelet activation as measured by aggregation or ATP secretion. Activation of monocytes and platelets required appropriate intracellular transmembrane signaling and was inhibited by calcium antagonists or by specific inhibitors of protein kinase C or guanine nucleotide binding proteins. Soluble CD36 inhibited binding of IRBC to both monocytes and platelets, suggesting that these interactions are mediated by the CD36 receptor. Using a cytochemical electron microscopic technique, the presence of reactive oxygen intermediates was identified at the interface between human monocytes and IRBC. These data provide support for the hypothesis that reactive oxygen intermediates produced by monocytes when IRBC ligands interact with cell surface receptors may play a role in the pathophysiology of falciparum malaria. Images PMID:2474569

  20. Nuclear Factor-κB Activation and Postischemic Inflammation Are Suppressed in CD36-Null Mice after Middle Cerebral Artery Occlusion

    PubMed Central

    Kunz, Alexander; Abe, Takato; Hochrainer, Karin; Shimamura, Munehisa; Anrather, Josef; Racchumi, Gianfranco; Zhou, Ping; Iadecola, Costantino

    2008-01-01

    CD36, a class-B scavenger receptor involved in multiple functions, including inflammatory signaling, may also contribute to ischemic brain injury through yet unidentified mechanisms. We investigated whether CD36 participates in the molecular events underlying the inflammatory reaction that accompanies cerebral ischemia and may contribute to the tissue damage. We found that activation of nuclear factor-κB, a transcription factor that coordinates postischemic gene expression, is attenuated in CD36-null mice subjected to middle cerebral artery occlusion. The infiltration of neutrophils and the glial reaction induced by cerebral ischemia were suppressed. Treatment with an inhibitor of inducible nitric oxide synthase, an enzyme that contributes to the tissue damage, reduced ischemic brain injury in wild-type mice, but not in CD36 nulls. In contrast to cerebral ischemia, the molecular and cellular inflammatory changes induced by intracerebroventricular injection of interleukin-1β were not attenuated in CD36-null mice. The findings unveil a novel role of CD36 in early molecular events leading to nuclear factor-κB activation and postischemic inflammation. Inhibition of CD36 signaling may be a valuable therapeutic approach to counteract the deleterious effects of postischemic inflammation. PMID:18272685

  1. 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

  2. Obesity alters the gustatory perception of lipids in the mouse: plausible involvement of lingual CD36[S

    PubMed Central

    Chevrot, Michael; Bernard, Arnaud; Ancel, Déborah; Buttet, Marjorie; Martin, Céline; Abdoul-Azize, Souleymane; Merlin, Jean-François; Poirier, Hélène; Niot, Isabelle; Khan, Naim Akhtar; Passilly-Degrace, Patricia; Besnard, Philippe

    2013-01-01

    A relationship between orosensory detection of dietary lipids, regulation of fat intake, and body mass index was recently suggested. However, involved mechanisms are poorly understood. Moreover, whether obesity can directly modulate preference for fatty foods remains unknown. To address this question, exploration of the oral lipid sensing system was undertaken in diet-induced obese (DIO) mice. By using a combination of biochemical, physiological, and behavioral approaches, we found that i) the attraction for lipids is decreased in obese mice, ii) this behavioral change has an orosensory origin, iii) it is reversed in calorie-restricted DIO mice, revealing an inverse correlation between fat preference and adipose tissue size, iv) obesity suppresses the lipid-mediated downregulation of the lipid-sensor CD36 in circumvallate papillae, usually found during the refeeding of lean mice, and v) the CD36-dependent signaling cascade controlling the intracellular calcium levels ([Ca2+]i) in taste bud cells is decreased in obese mice. Therefore, obesity alters the lipid-sensing system responsible for the oral perception of dietary lipids. This phenomenon seems to take place through a CD36-mediated mechanism, leading to changes in eating behavior. PMID:23840049

  3. 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.

  4. 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.

  5. CD36/SR-B2-TLR2 Dependent Pathways Enhance Porphyromonas gingivalis Mediated Atherosclerosis in the Ldlr KO Mouse Model.

    PubMed

    Brown, Paul M; Kennedy, David J; Morton, Richard E; Febbraio, Maria

    2015-01-01

    There is strong epidemiological association between periodontal disease and cardiovascular disease but underlying mechanisms remain ill-defined. Because the human periodontal disease pathogen, Porphyromonas gingivalis (Pg), interacts with innate immune receptors Toll-like Receptor (TLR) 2 and CD36/scavenger receptor-B2 (SR-B2), we studied how CD36/SR-B2 and TLR pathways promote Pg-mediated atherosclerosis. Western diet fed low density lipoprotein receptor knockout (Ldlr°) mice infected orally with Pg had a significant increase in lesion burden compared with uninfected controls.This increase was entirely CD36/SR-B2-dependent, as there was no significant change in lesion burden between infected and uninfected Cd36o/Ldlro mice [corrected]. Western diet feeding promoted enhanced CD36/SR-B2-dependent IL1β generation and foam cell formation as a result of Pg lipopolysaccharide (PgLPS) exposure. CD36/SR-B2 and TLR2 were necessary for inflammasome activation and optimal IL1ß generation, but also resulted in LPS induced lethality (pyroptosis). Modified forms of LDL inhibited Pg-mediated IL1ß generation in a CD36/SR-B2-dependent manner and prevented pyroptosis, but promoted foam cell formation. Our data show that Pg infection in the oral cavity can lead to significant TLR2-CD36/SR-B2 dependent IL1ß release. In the vessel wall, macrophages encountering systemic release of IL1ß, PgLPS and modified LDL have increased lipid uptake, foam cell formation, and release of IL1ß, but because pyroptosis is inhibited, this enables macrophage survival and promotes increased plaque development. These studies may explain increased lesion burden as a result of periodontal disease, and suggest strategies for development of therapeutics.

  6. Selection of an antibody library identifies a pathway to induce immunity by targeting CD36 on steady-state CD8 alpha+ dendritic cells.

    PubMed

    Tagliani, Elisa; Guermonprez, Pierre; Sepúlveda, Jorge; López-Bravo, María; Ardavín, Carlos; Amigorena, Sebastian; Benvenuti, Federica; Burrone, Oscar R

    2008-03-01

    Improvement of the strategy to target tumor Ags to dendritic cells (DCs) for immunotherapy requires the identification of the most appropriate ligand/receptor pairing. We screened a library of Ab fragments on mouse DCs to isolate new potential Abs capable of inducing protective immune responses. The screening identified a high-affinity Ab against CD36, a multi-ligand scavenger receptor primarily expressed by the CD8alpha+ subset of conventional DCs. The Ab variable regions were genetically linked to the model Ag OVA and tested in Ag presentation assays in vitro and in vivo. Anti-CD36-OVA was capable of delivering exogenous Ags to the MHC class I and MHC class II processing pathways. In vivo, immunization with anti-CD36-OVA induced robust activation of naive CD4+ and CD8+ Ag-specific T lymphocytes and the differentiation of primed CD8+ T cells into long-term effector CTLs. Vaccination with anti-CD36-OVA elicited humoral and cell-mediated protection from the growth of an Ag-specific tumor. Notably, the relative efficacy of targeting CD11c/CD8alpha+ via CD36 or DEC205 was qualitatively different. Anti-DEC205-OVA was more efficient than anti-CD36-OVA in inducing early events of naive CD8+ T cell activation. In contrast, long-term persistence of effector CTLs was stronger following immunization with anti-CD36-OVA and did not require the addition of exogenous maturation stimuli. The results identify CD36 as a novel potential target for immunotherapy and indicate that the outcome of the immune responses vary by targeting different receptors on CD8alpha+ DCs.

  7. Cellular fatty acid uptake: a pathway under construction.

    PubMed

    Su, Xiong; Abumrad, Nada A

    2009-03-01

    Membrane uptake of long-chain fatty acids (FAs) is the first step in cellular FA utilization and a point of metabolic regulation. CD36 facilitates a major fraction of FA uptake by key tissues. This review highlights the contribution of CD36 to pathophysiology in rodents and humans. Novel concepts regarding regulation of CD36-facilitated uptake are discussed (i.e. the role of membrane rafts and caveolae, CD36 recycling between intracellular depots and the membrane, and chemical modifications of the protein that impact its turnover and recruitment). Importantly, CD36 membrane levels and turnover are abnormal in diabetes, resulting in dysfunctional FA utilization. In addition, variants in the CD36 gene were shown recently to influence susceptibility for the metabolic syndrome, which greatly increases the risk of diabetes and heart disease. PMID:19185504

  8. CD36 is not involved in scavenger receptor-mediated endocytic uptake of glycolaldehyde- and methylglyoxal-modified proteins by liver endothelial cells.

    PubMed

    Nakajou, Keisuke; Horiuchi, Seikoh; Sakai, Masakazu; Hirata, Kenshiro; Tanaka, Makiko; Takeya, Motohiro; Kai, Toshiya; Otagiri, Masaki

    2005-05-01

    Circulating proteins modified by advanced glycation end-products (AGE) are mainly taken up by liver endothelial cells (LECs) via scavenger receptor-mediated endocytosis. Endocytic uptake of chemically modified proteins by macrophages and macrophage-derived cells is mediated by class A scavenger receptor (SR-A) and CD36. In a previous study using SR-A knockout mice, we demonstrated that SR-A is not involved in endocytic uptake of AGE proteins by LECs [Matsumoto et al. (2000) Biochem. J. 352, 233-240]. The present study was conducted to determine the contribution of CD36 to this process. Glycolaldehyde-modified BSA (GA-BSA) and methylglyoxal-modified BSA (MG-BSA) were used as AGE proteins. 125I-GA-BSA and 125I-MG-BSA underwent endocytic degradation by these cells at 37 degrees C, and this process was inhibited by several ligands for the scavenger receptors. However, this endocytic uptake of 125I-GA-BSA by LECs was not inhibited by a neutralizing anti-CD36 antibody. Similarly, hepatic uptake of (111)In-GA-BSA after its intravenous injection was not significantly attenuated by co-administration of the anti-CD36 antibody. These results clarify that CD36 does not play a significant role in elimination of GA-BSA and MG-BSA from the circulation, suggesting that the receptor involved in endocytic uptake of circulating AGE proteins by LEC is not SR-A or CD36.

  9. CD36 plays an important role in the clearance of oxLDL and associated age-dependent sub-retinal deposits.

    PubMed

    Picard, Emilie; Houssier, Marianne; Bujold, Kim; Sapieha, Przemyslaw; Lubell, William; Dorfman, Allison; Racine, Julie; Hardy, Pierre; Febbraio, Maria; Lachapelle, Pierre; Ong, Huy; Sennlaub, Florian; Chemtob, Sylvain

    2010-12-01

    Age-related macular degeneration (AMD) represents the major cause of vision loss in industrialized nations. Laminar deposits in Bruch's membrane (BM) are among the first prominent histopathologic features, along with drusen formation, and have been found to contain oxidized lipids. Increases in concentrations of oxidized LDL (oxLDL) in plasma are observed with age and high fat high (HFHC) cholesterol diet. CD36 is the principal receptor implicated in uptake of oxLDL, and is expressed in the retinal pigment epithelium (RPE). We determined if CD36 participates in oxLDL uptake in RPE and correspondingly in clearance of sub-retinal deposits. Uptake of oxLDL by RPEin vitro and in vivo was CD36-dependent. CD36 deficiency in mice resulted in age-associated accumulation of oxLDL and sub-retinal BM thickening, despite fed a regular diet. Conversely, treatment of HFHC-fed ApoE null mice with a CD36 agonist, EP80317 (300 μg/kg/day), markedly diminished thickening of BM, and partially preserved (in part) photoreceptor function. In conclusion, our data uncover a new role for CD36 in the clearance of oxidized lipids from BM and in the prevention of age-dependent sub-retinal laminar deposits.

  10. Oxidized High-Density Lipoprotein Impairs Endothelial Progenitor Cells' Function by Activation of CD36-MAPK-TSP-1 Pathways

    PubMed Central

    Wu, Jianxiang; He, Zhiqing; Gao, Xiang; Wu, Feng; Ding, Ru; Ren, Yusheng; Jiang, Qijun; Fan, Min

    2015-01-01

    Abstract Aims: High-density lipoprotein (HDL) levels inversely correlate with cardiovascular events due to the protective effects on vascular wall and stem cells, which are susceptible to oxidative modifications and then lead to potential pro-atherosclerotic effects. We proposed that oxidized HDL (ox-HDL) might lead to endothelial progenitor cells (EPCs) dysfunction and investigated underlying mechanisms. Results: ox-HDL was shown to increase apoptosis and intracellular reactive oxygen species levels, but to reduce migration, angiogenesis, and cholesterol efflux of EPCs in a dose-dependent manner. p38 mitogen-activated protein kinase (MAPK) and NF-κB were activated after ox-HDL stimulation, which also upregulated thrombospondin-1 (TSP-1) expression without affecting vascular endothelial growth factor. Effects caused by ox-HDL could be significantly attenuated by pretreatment with short hairpin RNA-mediated CD36 knockdown or probucol. Data of in vivo experiments and the inverse correlation of ox-HDL and circulating EPC numbers among patients with coronary artery diseases (CAD) or CAD and type 2 diabetes also supported it. Meanwhile, HDL separated from such patients could significantly increase cultured EPC's caspase 3 activity, further supporting our proposal. Innovation: This is the most complete study to date of how ox-HDL would impair EPCs function, which was involved with activation of CD36-p38 MAPK-TSP-1 pathways and proved by not only the inverse relationship between ox-HDL and circulating EPCs in clinic but also pro-apoptotic effects of HDL separated from patients' serum. Conclusion: Activation of CD36-p38 MAPK-TSP-1 pathways contributes to the pathological effects of ox-HDL on EPCs' dysfunction, which might be one of the potential etiological factors responsible for the disturbed neovascularization in chronic ischemic disease. Antioxid. Redox Signal. 22, 308–324. PMID:25313537

  11. 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...

  12. Increased hepatic CD36 expression contributes to dyslipidemia associated with diet-induced obesity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The etiology of type 2 diabetes often involves diet-induced obesity (DIO), which is associated with elevated plasma fatty acids and lipoprotein associated triglycerides. Since aberrant hepatic fatty acid uptake may contribute to this, we investigated whether increased expression of a fatty acid tran...

  13. Expression of the energy substrate transporters in uterine fibroids.

    PubMed

    Knapp, Paweł; Chabowski, Adrian; Posmyk, Renata; Górski, Jan

    2016-03-01

    Proliferating cells exhibit accelerated rates of substrate utilization, favoring glucose over fatty acids (FA's) oxidation. Protein-mediated transport is thought to play a predominant role in facilitating either glucose or FA routing into the cells. In the present study, we examined the expression of glucose transporters (GLUT-1, GLUT-4) and fatty acids transporters (FAT/CD36, FATP-1, FATP-4) at transcript and protein levels as well as cytosolic fatty acid binding proteins (H-FABP, ACBP) in human fibroids (n=74, size up to 3cm diameter) and compared with pair-matched healthy myometrium. Additionally lipid content (diacylglycerols, triacylglycerols and ceramide) was estimated by gas liquid chromatography (GLC). Uterine fibroids displayed decreased expression of both FAT/CD36 and FATP-1 proteins along with lower diacylglycerol (DAG) and triacylglycerol (TAG) content as compared to healthy pair-matched myometrium. The expression of glucose transport proteins (GLUT-4 and GLUT-1) remained relatively constant, although the higher expression of GLUT-1 in uterine fibroids did not reach the minimum significance threshold (p=0.056). However, no change in either cytochrome c oxidase (COX IV) or hydroxyacyl-CoA dehydrogenase (HADHSC) was observed and these data confirm a possible metabolic shift favoring glucose utilization over fatty acid oxidation in human uterine fibroids. PMID:26932421

  14. Plasmodium falciparum erythrocyte membrane protein 1 is a parasitized erythrocyte receptor for adherence to CD36, thrombospondin, and intercellular adhesion molecule 1.

    PubMed Central

    Baruch, D I; Gormely, J A; Ma, C; Howard, R J; Pasloske, B L

    1996-01-01

    Adherence of mature Plasmodium falciparum parasitized erythrocytes (PRBCs) to microvascular endothelium contributes directly to acute malaria pathology. We affinity purified molecules from detergent extracts of surface-radioiodinated PRBCs using several endothelial cell receptors known to support PRBC adherence, including CD36, thrombospondin (TSP), and intercellular adhesion molecule 1 (ICAM-1). All three host receptors affinity purified P. falciparum erythrocyte membrane protein 1 (PfEMP1), a very large malarial protein expressed on the surface of adherent PRBCs. Binding of PfEMP1 to particular host cell receptors correlated with the binding phenotype of the PRBCs from which PfEMP1 was extracted. Preadsorption of PRBC extracts with anti-PfEMP1 antibodies, CD36, or TSP markedly reduced PfEMP1 binding to CD36 or TSP. Mild trypsinization of intact PRBCs of P. falciparum strains shown to express antigenically different PfEMP1 released different (125)I-labeled tryptic fragments of PfEMP1 that bound specifically to CD36 and TSP. In clone C5 and strain MC, these activities resided on different tryptic fragments, but a single tryptic fragment from clone ItG-ICAM bound to both CD36 and TSP. Hence, the CD36- and TSP-binding domains are distinct entities located on a single PfEMP1 molecule. PfEMP1, the malarial variant antigen on infected erythrocytes, is therefore a receptor for CD36, TSP, and ICAM-1. A therapeutic approach to block or reverse adherence of PRBCs to host cell receptors can now be pursued with the identification of PfEMP1 as a malarial receptor for PRBC adherence to host proteins. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8622965

  15. CD36 Upregulation Mediated by Intranasal LV-NRF2 Treatment Mitigates Hypoxia-Induced Progression of Alzheimer's-Like Pathogenesis

    PubMed Central

    Wang, Chun-Yan; Xie, Jing-Wei; Cai, Jian-Hui; Wang, Tao; Xu, Ye; Wang, Xu

    2014-01-01

    Abstract Aims: There is extensive evidence that oxidative stress induces cellular dysfunction in the brain and plays a critical role in Alzheimer's disease (AD) pathogenesis. Hypoxia increases factors involved in oxidative stress injury and contributes to the onset and progression of AD. Nuclear factor erythroid 2-related factor 2 (NRF2), a major component regulating antioxidant response, is attenuated in the AD brain. Importantly, NRF2 directly regulates the alternative first exons of CD36, an important participant in oxidative and inflammatory processes. To explore the effects of hypoxia-induced deterioration of AD-like pathogenesis and investigate the correlation between hypoxia-induced NRF2 signal alterations and CD36 expression, we examined the NRF2 signaling, CD36, and oxidative stress events in hypoxia-treated APPswe/PSEN1dE9 (APP/PS1) mice brain. Results: We observed that hypoxia treatment increased oxidative stress, exacerbated inflammation, and aggravated learning defects in aged APP/PS1 mice. Microglia from hypoxia-treated mice brain exhibited marked reduction in CD36 expression and inhibition of β-amyloid (Aβ) degradation. Accordingly, hypoxia treatment caused a decrease in transactivation of NRF2 target genes in the aging mouse brain. Intranasal administration with a lentiviral vector encoding human NRF2 increased CD36 expression, ameliorated the weak antioxidant response triggered by hypoxia, diminished Aβ deposition, and improved spatial memory defects. Innovation: In this study, we demonstrated for the first time that NRF2 intranasal treatment-induced increases of CD36 could enhance Aβ clearance in AD transgenic mouse. Conclusion: These results suggest that targeting NRF2-mediated CD36 expression might provide a beneficial intervention for cognitive impairment and oxidative stress in AD progression. Antioxid. Redox Signal. 21, 2208–2230. PMID:24702189

  16. 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.

  17. Effects of cAMP modulators on long-chain fatty-acid uptake and utilization by electrically stimulated rat cardiac myocytes.

    PubMed Central

    Luiken, J J F P; Willems, J; Coort, S L M; Coumans, W A; Bonen, A; Van Der Vusse, G J; Glatz, J F C

    2002-01-01

    Recently, we established that cellular contractions increase long-chain fatty-acid (FA) uptake by cardiac myocytes. This increase is dependent on the transport function of an 88 kDa membrane FA transporter, FA translocase (FAT/CD36), and, in analogy to skeletal muscle, is likely to involve its translocation from an intracellular pool to the sarcolemma. In the present study, we investigated whether cAMP-dependent signalling is involved in this translocation process. Isoproterenol, dibutyryl-cAMP and the phosphodiesterase (PDE) inhibitor, amrinone, which markedly raised the intracellular cAMP level, did not affect cellular FA uptake, but influenced the fate of intracellular FAs by directing these to mitochondrial oxidation in electrostimulated cardiac myocytes. The PDE inhibitors 3-isobutyl-1-methylxanthine, milrinone and dipyridamole each significantly stimulated FA uptake as well as intracellular cAMP levels, but these effects were quantitatively unrelated. The stimulatory effects of these PDE inhibitors were antagonized by sulpho- N -succinimidylpalmitate, indicating the involvement of FAT/CD36, albeit that the different PDE inhibitors use different molecular mechanisms to stimulate FAT/CD36-mediated FA uptake. Notably, 3-isobutyl-1-methylxanthine and milrinone increased the intrinsic activity of FAT/CD36, possibly through its covalent modification, and dipyridamole induces translocation of FAT/CD36 to the sarcolemma. Elevation of intracellular cGMP, but not of cAMP, by the PDE inhibitor zaprinast did not have any effect on FA uptake and metabolism by cardiac myocytes. The stimulatory effects of PDE inhibitors on cardiac FA uptake should be considered when applying these agents in clinical medicine. PMID:12093365

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. The Drosophila CD36 Homologue croquemort Is Required to Maintain Immune and Gut Homeostasis during Development and Aging

    PubMed Central

    Guillou, Aurélien; Wang, Hui

    2016-01-01

    Phagocytosis is an ancient mechanism central to both tissue homeostasis and immune defense. Both the identity of the receptors that mediate bacterial phagocytosis and the nature of the interactions between phagocytosis and other defense mechanisms remain elusive. Here, we report that Croquemort (Crq), a Drosophila member of the CD36 family of scavenger receptors, is required for microbial phagocytosis and efficient bacterial clearance. Flies mutant for crq are susceptible to environmental microbes during development and succumb to a variety of microbial infections as adults. Crq acts parallel to the Toll and Imd pathways to eliminate bacteria via phagocytosis. crq mutant flies exhibit enhanced and prolonged immune and cytokine induction accompanied by premature gut dysplasia and decreased lifespan. The chronic state of immune activation in crq mutant flies is further regulated by negative regulators of the Imd pathway. Altogether, our data demonstrate that Crq plays a key role in maintaining immune and organismal homeostasis. PMID:27780230

  4. 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.

  5. Oxidized Lipoprotein Uptake Through the CD36 Receptor Activates the NLRP3 Inflammasome in Human Retinal Pigment Epithelial Cells

    PubMed Central

    Gnanaguru, Gopalan; Choi, Ariel R.; Amarnani, Dhanesh; D'Amore, Patricia A.

    2016-01-01

    Purpose Accumulation of oxidized phospholipids/lipoproteins with age is suggested to contribute to the pathogenesis of AMD. We investigated the effect of oxidized LDL (ox-LDL) on human RPE cells. Methods Primary human fetal RPE (hf-RPE) and ARPE-19 cells were treated with different doses of LDL or ox-LDL. Assessment of cell death was measured by lactate dehydrogenase release into the conditioned media. Barrier function of RPE was assayed by measuring transepithelial resistance. Lysosomal accumulation of ox-LDL was determined by immunostaining. Expression of CD36 was determined by RT-PCR; protein blot and function was examined by receptor blocking. NLRP3 inflammasome activation was assessed by RT-PCR, protein blot, caspase-1 fluorescent probe assay, and inhibitor assays. Results Treatment with ox-LDL, but not LDL, for 48 hours caused significant increase in hf-RPE and ARPE-19 (P < 0.001) cell death. Oxidized LDL treatment of hf-RPE cells resulted in a significant decrease in transepithelial resistance (P < 0.001 at 24 hours and P < 0.01 at 48 hours) relative to LDL-treated and control cells. Internalized ox-LDL was targeted to RPE lysosomes. Uptake of ox-LDL but not LDL significantly increased CD36 protein and mRNA levels by more than 2-fold. Reverse transcription PCR, protein blot, and caspase-1 fluorescent probe assay revealed that ox-LDL treatment induced NLRP3 inflammasome when compared with LDL treatment and control. Inhibition of NLRP3 activation using 10 μM isoliquiritigenin significantly (P < 0.001) inhibited ox-LDL induced cytotoxicity. Conclusions These data are consistent with the concept that ox-LDL play a role in the pathogenesis of AMD by NLRP3 inflammasome activation. Suppression of NLRP3 inflammasome activation could attenuate RPE degeneration and AMD progression. PMID:27607416

  6. Oily Fish Consumption Modifies the Association between CD36 rs6969989 Polymorphism and Lipid Profiles in Korean Women

    PubMed Central

    Shin, Yoonjin; Kim, Yangha

    2016-01-01

    The aim of this study was to investigate the association of CD36, a class B scavenger receptor, rs6969989 polymorphism with the serum lipid profiles in Korean women, together with their modulation by oily fish consumption. Subjects were participants from the Korean Genome Epidemiology Study (KoGES), which was initiated in 2001 as a large-scale. A total of 4,210 women aged 39 to 70 were included in this study. Data were collected using self-administered questionnaires, anthropometric measurements, and blood chemical analysis. Dietary intake was analyzed using a semi-quantitative food frequency questionnaire. The minor allele frequency for rs6969989 was found in 12% of this population. Homozygotes minor G allele at the rs6868989 exhibited significantly higher high density lipoprotein cholesterol (HDL-C) concentrations (P-trend=0.043) and lower fasting glucose (P-trend=0.013) than major allele A carriers. The risk of low HDL-C was significantly lower in homozygotes for the G allele than the A allele carriers (P-trend=0.032). Gene-diet interaction effects between rs6969989 and oily fish intake were significantly associated with the risk of dyslipidemia (P-interaction= 0.004). Subjects with homozygotes minor G allele and high oily fish intake generally had a lower risk of dyslipidemia than did those with major allele homozygotes and low oily fish intake. These findings supported that oily fish consumption may modulate the contributions of CD36 rs6969989 on genetic predisposition to the risk of dyslipidemia. PMID:27752496

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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

  17. Synergically increased expression of CD36, CLA-1 and CD68, but not of SR-A and LOX-1, with the progression to foam cells from macrophages.

    PubMed

    Tsukamoto, Kayo; Kinoshita, Makoto; Kojima, Kyoko; Mikuni, Yoko; Kudo, Mikiko; Mori, Masaki; Fujita, Mineko; Horie, Eiko; Shimazu, Nobuko; Teramoto, Tamio

    2002-01-01

    Several species of scavenger receptors have so far been identified. However, it remains unclear which receptors are more crucial for the foam cell formation and progression. In the present study, we compared five major scavenger receptors (SR-A, CD36, CLA-1, CD68, and LOX-1) in their levels of expression at the different stages of foam cells derived from THP-1 cells. The expression of all scavenger receptors examined was up-regulated by the stimulation with TPA for 48 hours, despite the expressions of SR-A, CD36 and LOX-1 being very low before the treatment with TPA. Four to 7 days after the removal of TPA, the levels of CD36, CLA-1 and CD68 were increased significantly. In contrast, the expression of SR-A was suppressed significantly, and no change was observed in that of LOX-1. Furthermore, when the transformed macrophages were incubated with oxidized LDL, in which the uptake of [3H] cholesteryl oleoyl ether-labeled OxLDL was linear up to 7 days after the addition of OxLDL, the expression of CD36, CLA-1 and CD68 were greatly enhanced. This enhancement was more prominent than that without oxidized LDL, and the enhancement was sustained throughout the experimental period. On the other hand, SR-A was not up-regulated, and LOX-1 was down-regulated. We thus propose that CD36, CLA-1 and CD68, but not SR-A and LOX-1, may play crucial roles in the progression of macrophages to foam cells, which is a key step for the initiation of atherosclerosis.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Pharmacogenetic interaction between dexamethasone and Cd36-deficient segment of spontaneously hypertensive rat chromosome 4 affects triacylglycerol and cholesterol distribution into lipoprotein fractions.

    PubMed

    Krupková, Michaela; Sedová, Lucie; Liska, Frantisek; Krenová, Drahomíra; Kren, Vladimír; Seda, Ondrej

    2010-04-16

    Dexamethasone (DEX) is known to induce diabetes and dyslipidemia. We have compared fasting triacylglycerol and cholesterol concentrations across 20 lipoprotein fractions and glucose tolerance in control (standard diet) and DEX-treated 7-month-old males of two rat strains, Brown Norway (BN) and congenic BN.SHR-(Il6-Cd36)/Cub (BN.SHR4). These two inbred strains differ in a defined segment of chromosome 4, originally transferred from the spontaneously hypertensive rat (SHR) including the mutant Cd36 gene, a known target of DEX. Compared to BN, the standard-diet-fed BN.SHR4 showed higher cholesterol and triacylglycerol concentrations across many lipoprotein fractions, particularly in small VLDL and LDL particles. Total cholesterol was decreased by DEX by more than 21% in BN.SHR4 contrasting with the tendency to increase in BN (strain*DEX interaction p = 0.0017). Similar pattern was observed for triacylglycerol concentrations in LDL. The LDL particle size was significantly reduced by DEX in both strains. Also, while control BN and BN.SHR4 displayed comparable glycaemic profiles during oral glucose tolerance test, we observed a markedly blunted DEX induction of glucose intolerance in BN.SHR4 compared to BN. In summary, we report a pharmacogenetic interaction between limited genomic segment with mutated Cd36 gene and dexamethasone-induced glucose intolerance and triacylglycerol and cholesterol redistribution into lipoprotein fractions.

  9. Phagocytosis of Cholesteryl Ester Is Amplified in Diabetic Mouse Macrophages and Is Largely Mediated by CD36 and SR-A

    PubMed Central

    Guest, Christopher B.; Hartman, Matthew E.; O'Connor, Jason C.; Chakour, Kenneth S.; Sovari, Ali A.; Freund, Gregory G.

    2007-01-01

    Type 2 diabetes (T2D) is associated with accelerated atherosclerosis, which accounts for approximately 75% of all diabetes-related deaths. Here we investigate the link between diabetes and macrophage cholesteryl ester accumulation. When diabetic (db/db) mice are given cholesteryl ester intraperitoneally (IP), peritoneal macrophages (PerMΦs) recovered from these animals showed a 58% increase in intracellular cholesteryl ester accumulation over PerMΦs from heterozygote control (db/+) mice. Notably, PerMΦ fluid-phase endocytosis and large particle phagocytosis was equivalent in db/+and db/db mice. However, IP administration of CD36 and SR-A blocking antibodies led to 37% and 25% reductions in cholesteryl ester accumulation in PerMΦ. Finally, in order to determine if these scavenger receptors (SRs) were part of the mechanism responsible for the increased accumulation of cholesteryl esters observed in the diabetic mouse macrophages, receptor expression was quantified by flow cytometry. Importantly, db/db PerMΦs showed a 43% increase in CD36 expression and an 80% increase in SR-A expression. Taken together, these data indicate that direct cholesteryl ester accumulation in mouse macrophages is mediated by CD36 and SR-A, and the magnitude of accumulation is increased in db/db macrophages due to increased scavenger receptor expression. PMID:17551591

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba) Seed in the Heart of Dyslipemic Insulin-Resistant Rats.

    PubMed

    Creus, Agustina; Ferreira, María R; Oliva, María E; Lombardo, Yolanda B

    2016-01-28

    This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR) rats fed a sucrose-rich diet (SRD) and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA) improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO), was replaced by chia seeds from month 3 to 6 (SRD+chia). A reference group consumed a control diet (CD) all the time. Triglyceride, long-chain acyl CoA (LC ACoA) and diacylglycerol (DAG) contents, pyruvate dehydrogenase complex (PDHc) and muscle-type carnitine palmitoyltransferase 1 (M-CPT1) activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36), peroxisome proliferator activated receptor α (PPARα) and uncoupling protein 2 (UCP2) were analyzed. Results show that: (a) the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b) Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs) availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats.

  16. Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba) Seed in the Heart of Dyslipemic Insulin-Resistant Rats

    PubMed Central

    Creus, Agustina; Ferreira, María R.; Oliva, María E.; Lombardo, Yolanda B.

    2016-01-01

    This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR) rats fed a sucrose-rich diet (SRD) and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA) improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO), was replaced by chia seeds from month 3 to 6 (SRD+chia). A reference group consumed a control diet (CD) all the time. Triglyceride, long-chain acyl CoA (LC ACoA) and diacylglycerol (DAG) contents, pyruvate dehydrogenase complex (PDHc) and muscle-type carnitine palmitoyltransferase 1 (M-CPT1) activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36), peroxisome proliferator activated receptor α (PPARα) and uncoupling protein 2 (UCP2) were analyzed. Results show that: (a) the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b) Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs) availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats. PMID:26828527

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. Matrix-mediated canal formation in primmorphs from the sponge Suberites domuncula involves the expression of a CD36 receptor-ligand system.

    PubMed

    Müller, Werner E G; Thakur, Narsinh L; Ushijima, Hiroshi; Thakur, Archana N; Krasko, Anatoli; Le Pennec, Gaël; Indap, Madhavi M; Perovic-Ottstadt, Sanja; Schröder, Heinz C; Lang, Gerhard; Bringmann, Gerhard

    2004-05-15

    Sponges (Porifera), represent the phylogenetically oldest metazoan phylum still extant today. Recently, molecular biological studies provided compelling evidence that these animals share basic receptor/ligand systems, especially those involved in bodyplan formation and in immune recognition, with the higher metazoan phyla. An in vitro cell/organ-like culture system, the primmorphs, has been established that consists of proliferating and differentiating cells, but no canals of the aquiferous system. We show that after the transfer of primmorphs from the demosponge Suberites domuncula to a homologous matrix (galectin), canal-like structures are formed in these 3D-cell aggregates. In parallel with the formation of these structures a gene is expressed whose deduced protein falls into the CD36/LIMPII receptor family. The receptor was cloned and found to be strongly expressed after adhesion to the galectin matrix. This process was suppressed if primmorphs were co-incubated with a homologous polypeptide containing the CSVTCG domain, as found in thrombospondin-1 (and related) molecules of vertebrates. In situ hybridization studies revealed that the S. domuncula CD36/LIMPII receptor is localized in the pinacocytes that surround the canals of the sponge. Furthermore, a secondary metabolite from a sponge-associated bacterium was isolated and characterized, the 2-methylthio-1,4-naphthoquinone (MTN). MTN causes inhibition of cell proliferation of vertebrate tumor cells at concentrations of >80 ng/ml. However, doses of only 2 ng are required to potently inhibit angiogenesis in the chick chorio-allantoic membrane assay. At concentrations of 10 ng/ml this compound was also found to suppress the expression of the S. domuncula CD36/LIMPII; this result is a first indication that this secondary metabolite has a conserved functional activity: the suppression of the formation of the circulation system, from sponges to vertebrates.

  9. Associations between CD36 gene polymorphisms and metabolic response to a short-term endurance-training program in a young-adult population.

    PubMed

    Jayewardene, Avindra F; Mavros, Yorgi; Gwinn, Tom; Hancock, Dale P; Rooney, Kieron B

    2016-02-01

    Recent studies have shown that CD36 gene variants are associated with an increased prevalence of chronic disease. Although a genetic component to trainability has been proven, no data are available specifically on the influence of CD36 on training response. Two single nucleotide polymorphisms (SNPs) (rs1527479 and rs1984112) were assessed for associations with whole-body substrate oxidation, response to a 75-g dextrose oral glucose tolerance test, fasting plasma lipids, and cardiovascular disease risk factors in a young healthy cohort, both using cross-sectional analysis and following a 4-week endurance-exercise training program. Genotyping was performed using real-time polymerase chain reaction. Cross-sectional data were collected in 34 individuals (age, 22.7 ± 3.5 years), with 17 completing the training program. At baseline, TT SNP carriers at rs1527479 and wild-type GG carriers at rs1984112 were associated with significantly greater whole-body rate of fat oxidation (Fatox) during submaximal exercise (P < 0.05), whilst AA carriers at the same position were associated with elevated triglyceride (TG) levels. A significant genotype × time interaction in Fatox at SNP rs1984112 was identified at rest. Significant genotype × time interactions were present at rs1527479, with TT carriers exhibiting a favourable response to training when compared with C-allele carriers for fasting TG, diastolic blood pressure (DBP), and mean arterial pressure (MAP). In conclusion, cross-sectional assessment identified associations with Fatox and TG. Training response at both SNPs identified "at-risk" genotypes responding favourably to the training stimulus in Fatox, TG, DBP, and MAP. Although these data show potential pleiotropic influence of CD36 SNPs, assessment in a larger cohort is warranted.

  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. Rosiglitazone but not losartan prevents Nrf-2 dependent CD36 gene expression up-regulation in an in vivo atherosclerosis model

    PubMed Central

    Hernandez-Trujillo, Y; Rodriguez-Esparragon, F; Macias-Reyes, A; Caballero-Hidalgo, A; Rodriguez-Perez, Jose C

    2008-01-01

    Background Thiazolidinediones exert anti-inflammatory and anti-oxidative roles and attenuate atherosclerosis by mechanisms partially independent of their metabolizing actions. High doses of angiotensin type 1 receptor (AT1R) blocker losartan (LST) seem to promote fat cell formation by preserving PPARγ activity. Methods C57BL/6J diet-induced atherosclerotic susceptible mice randomly received a normal or a high-fat high-cholesterol (HFHC) diet and were treated with rosiglitazone (RG), LST or a vehicle for 12 weeks. Results HFHC was associated with increased PPARγ gene expression without an over regulation of PPARγ responsive genes, whereas RG and LST treatments were found to maintain PPARγ activity without resulting in increased PPARγ gene expression. A better anti-inflammatory and antioxidant profile in mice treated with RG regarding LST was observed in spite of a similar PPARγ preserved activity. Chromatin immunoprecipitation (ChIP) assays revealed that animals under HFHC diet treated with RG showed a significant nuclear factor erythroid 2-like 2 (Nrf2)-dependent down-regulation of the expression of the CD36 gene. Conclusion The PPARγ agonist RG exerts antioxidant properties that significantly reduced Nrf-2-dependent CD-36 up-regulation in mice under HFHC diet. Because LST treatment was also associated with a preserved PPARγ activity, our data suggests that these RG antioxidant effects are partially independent of its PPARγ metabolizing properties. PMID:18302760

  12. CD36 and Proteoglycan-Mediated Pathways for (n-3) Fatty Acid–Enriched Triglyceride-Rich Particle Blood Clearance in Mouse Models In Vivo and in Peritoneal Macrophages In Vitro1,2

    PubMed Central

    Densupsoontorn, Narumon; Carpentier, Yvon A.; Racine, Radjini; Murray, Faith M.; Seo, Toru; Ramakrishnan, Rajasekhar; Deckelbaum, Richard J.

    2008-01-01

    Because the mechanisms of (n-3) fatty acid–enriched triglyceride-rich particle [(n-3)-TGRP] uptake are not well characterized, we questioned whether (n-3)-TGRP are removed via “nonclassical” pathways, e.g., pathways other than an LDL receptor and/or involving apolipoprotein E (apoE). Chylomicron-sized model (n-3)-TGRP labeled with [3H]cholesteryl ether were injected into wild-type (WT) and CD36 knockout (CD36−/−) mice at low, nonsaturating and high, saturating doses. Blood clearance of (n-3)-TGRP was determined by calculating fractional catabolic rates. At saturating doses, blood clearance of (n-3)-TGRP was slower in CD36−/− mice relative to WT mice, suggesting that in part CD36 contributes to (n-3)-TGRP uptake. To further examine the potential nonclassical clearance pathways, peritoneal-elicited macrophages from WT and CD36−/− mice were incubated with (n-3)-TGRP in the presence of apoE, lactoferrin, and/or sodium chlorate. Cellular (n-3)-TGRP uptake was measured to test the roles of apoE-mediated pathways and/or proteoglycans. ApoE-mediated pathways compensated in part for defective (n-3)-TGRP uptake in CD36−/− cells. Lactoferrin decreased (n-3)-TGRP uptake in the presence of apoE. Inhibition of cell proteoglycan synthesis by chlorate reduced (n-3)-TGRP uptake in both groups of macrophages, and chlorate effects were independent of apoE. We conclude that although CD36 is involved, it is not the primary contributor to the blood clearance of (n-3)-TGRP. The removal of (n-3)-TGRP likely relies more on nonclassical pathways, such as proteoglycan-mediated pathways. PMID:18203888

  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. 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)

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. Large Multiethnic Candidate Gene Study for C-Reactive Protein Levels: Identification of a Novel Association at CD36 in African Americans

    PubMed Central

    Ellis, Jaclyn; Lange, Ethan M.; Li, Jin; Dupuis, Josee; Baumert, Jens; Walston, Jeremy D.; Keating, Brendan J.; Durda, Peter; Fox, Ervin R.; Palmer, Cameron D.; Meng, Yan A.; Young, Taylor; Farlow, Deborah N.; Schnabel, Renate B.; Marzi, Carola S.; Larkin, Emma; Martin, Lisa W.; Bis, Joshua C.; Auer, Paul; Ramachandran, Vasan S.; Gabriel, Stacey B.; Willis, Monte S.; Pankow, James S.; Papanicolaou, George J.; Rotter, Jerome I.; Ballantyne, Christie M.; Gross, Myron D.; Lettre, Guillaume; Wilson, James G.; Peters, Ulrike; Koenig, Wolfgang; Tracy, Russell P.; Redline, Susan; Reiner, Alex P.; Benjamin, Emelia J.; Lange, Leslie A.

    2014-01-01

    C-reactive protein (CRP) is a heritable biomarker of systemic inflammation and a predictor of cardiovascular disease (CVD). Large-scale genetic association studies for CRP have largely focused on individuals of European descent. We sought to uncover novel genetic variants for CRP in a multi-ethnic sample using the ITMAT Broad-CARe (IBC) array, a custom 50,000 SNP gene-centric array having dense coverage of over 2,000 candidate CVD genes. We performed analyses on 7570 African Americans (AA) from the Candidate gene Association Resource (CARe) study and race-combined meta-analyses that included 29,939 additional individuals of European descent from CARe, the Women’s Health Initiative (WHI) and KORA studies. We observed array-wide significance (p<2.2×10−6) for four loci in AA, three of which have been reported previously in individuals of European descent (IL6R, p=2.0×10−6; CRP, p=4.2×10−71; APOE, p=1.6×10−6). The fourth significant locus, CD36 (p=1.6×10−6), was observed at a functional variant (rs3211938) that is extremely rare in individuals of European descent. We replicated the CD36 finding (p=1.8×10−5) in an independent sample of 8041 AA women from WHI; a meta-analysis combining the CARe and WHI AA results at rs3211938 reached genome-wide significance (p=1.5×10−10). In the race-combined meta-analyses, 13 loci reached significance, including ten (CRP, TOMM40/APOE/APOC1, HNF1A, LEPR, GCKR, IL6R, IL1RN, NLRP3, HNF4A and BAZ1B/BCL7B) previously associated with CRP, and one (ARNTL) previously reported to be nominally associated with CRP. Two novel loci were also detected (RPS6KB1, p=2.0×10−6; CD36, p=1.4×10−6). These results highlight both shared and unique genetic risk factors for CRP in AA compared to populations of European descent. PMID:24643644

  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. Degree of oxidation of low density lipoprotein affects expression of CD36 and PPARgamma, but not cytokine production, by human monocyte-macrophages.

    PubMed

    Kavanagh, Ian C; Symes, Carole E; Renaudin, Pauline; Nova, Esther; Mesa, Maria Dolores; Boukouvalas, George; Leake, David S; Yaqoob, Parveen

    2003-06-01

    Oxidized low-density lipoprotein (oxLDL) exhibits many atherogenic effects, including the promotion of monocyte recruitment to the arterial endothelium and the induction of scavenger receptor expression. However, while atherosclerosis involves chronic inflammation within the arterial intima, it is unclear whether oxLDL alone provides a direct inflammatory stimulus for monocyte-macrophages. Furthermore, oxLDL is not a single, well-defined entity, but has structural and physical properties which vary according to the degree of oxidation. We tested the hypothesis that the biological effects of oxLDL will vary according to its degree of oxidation and that some species of oxLDL will have atherogenic properties, while other species may be responsible for its inflammatory activity. The atherogenic and inflammatory properties of LDL oxidized to predetermined degrees (mild, moderate and extensive oxidation) were investigated in a single system using human monocyte-derived macrophages. Expression of CD36 mRNA was up-regulated by mildly- and moderately-oxLDL, but not highly-oxLDL. The expression of the transcription factor, proliferator-activated receptor-gamma (PPARgamma), which has been proposed to positively regulate the expression of CD36, was increased to the greatest degree by highly-oxLDL. However, the DNA binding activity of PPARgamma was increased only by mildly- and moderately-oxLDL. None of the oxLDL species appeared to be pro-inflammatory towards monocytes, either directly or indirectly through mediators derived from lymphocytes, regardless of the degree of oxidation.

  9. Cinnamaldehyde and allopurinol reduce fructose-induced cardiac inflammation and fibrosis by attenuating CD36-mediated TLR4/6-IRAK4/1 signaling to suppress NLRP3 inflammasome activation

    PubMed Central

    Kang, Lin-Lin; Zhang, Dong-Mei; Ma, Chun-Hua; Zhang, Jian-Hua; Jia, Ke-Ke; Liu, Jia-Hui; Wang, Rong; Kong, Ling-Dong

    2016-01-01

    Fructose consumption induces metabolic syndrome to increase cardiovascular disease risk. Cinnamaldehyde and allopurinol possess anti-oxidative and anti-inflammatory activity to relieve heart injury in metabolic syndrome. But the mechanisms of fructose-induced cardiac injury, and cardioprotective effects of cinnamaldehyde and allopurinol are not completely understood. In this study, fructose-fed rats displayed metabolic syndrome with elevated serum ox-LDL, cardiac oxidative stress, inflammation and fibrosis. Scavenger receptor CD36, Toll-like receptor 4 (TLR4), TLR6, IL-1R-associated kinase 4/1 (IRAK4/1), nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome, interleukin-1β, transforming growth factor-β (TGF-β), drosophila mothers against DPP homolog (Smad) 2/3 phosphorylation and Smad4 were increased in animal and H9c2 cell models. These pathological processes were further evaluated in ox-LDL or fructose-exposed H9c2 cells pretreated with ROS scavenger and CD36 specific inhibitor, or IRAK1/4 inhibitor, and transfected with CD36, NLRP3, or IRAK4/1 siRNA, demonstrating that NLPR3 inflammasome activation through CD36-mediated TLR4/6-IRAK4/1 signaling may promote cardiac inflammation and fibrosis. Cinnamaldehyde and allopurinol reduced cardiac oxidative stress to suppress NLPR3 inflammasome activation and TGF-β/Smads signaling by inhibiting CD36-mediated TLR4/6-IRAK4/1 signaling under fructose induction. These results suggest that the blockage of CD36-mediated TLR4/6-IRAK4/1 signaling to suppress NLRP3 inflammasome activation by cinnamaldehyde and allopurinol may protect against fructose-induced cardiac inflammation and fibrosis. PMID:27270216

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. Single nucleotide polymorphisms in CETP, SLC46A1, SLC19A1, CD36, BCMO1, APOA5, and ABCA1 are significant predictors of plasma HDL in healthy adults

    PubMed Central

    2013-01-01

    Background In a marker-trait association study we estimated the statistical significance of 65 single nucleotide polymorphisms (SNP) in 23 candidate genes on HDL levels of two independent Caucasian populations. Each population consisted of men and women and their HDL levels were adjusted for gender and body weight. We used a linear regression model. Selected genes corresponded to folate metabolism, vitamins B-12, A, and E, and cholesterol pathways or lipid metabolism. Methods Extracted DNA from both the Sacramento and Beltsville populations was analyzed using an allele discrimination assay with a MALDI-TOF mass spectrometry platform. The adjusted phenotype, y, was HDL levels adjusted for gender and body weight only statistical analyses were performed using the genotype association and regression modules from the SNP Variation Suite v7. Results Statistically significant SNP (where P values were adjusted for false discovery rate) included: CETP (rs7499892 and rs5882); SLC46A1 (rs37514694; rs739439); SLC19A1 (rs3788199); CD36 (rs3211956); BCMO1 (rs6564851), APOA5 (rs662799), and ABCA1 (rs4149267). Many prior association trends of the SNP with HDL were replicated in our cross-validation study. Significantly, the association of SNP in folate transporters (SLC46A1 rs37514694 and rs739439; SLC19A1 rs3788199) with HDL was identified in our study. Conclusions Given recent literature on the role of niacin in the biogenesis of HDL, focus on status and metabolism of B-vitamins and metabolites of eccentric cleavage of β-carotene with lipid metabolism is exciting for future study. PMID:23656756

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. Genetic variation in CD36, HBA, NOS3 and VCAM1 is associated with chronic haemolysis level in sickle cell anaemia: a longitudinal study.

    PubMed

    Coelho, Andreia; Dias, Alexandra; Morais, Anabela; Nunes, Baltazar; Ferreira, Emanuel; Picanço, Isabel; Faustino, Paula; Lavinha, João

    2014-03-01

    Chronic haemolysis stands out as one of the hallmarks of sickle cell anaemia, a clinically heterogeneous autosomal recessive monogenic anaemia. However, the genetic architecture of this sub-phenotype is still poorly understood. Here, we report the results of an association study between haemolysis biomarkers (serum LDH, total bilirubin and reticulocyte count) and the inheritance of 41 genetic variants of ten candidate genes in a series of 99 paediatric SS patients (median current age of 9.9 yr) followed up in two general hospitals in Greater Lisboa area (median follow-up per patient of 5.0 yr). Although in a large number of tests a seemingly significant (i.e. P < 0.05) association was observed, the following ones were confirmed upon correction for multiple comparisons: (i) an increased serum LDH level was associated with haplotype 7 within VCAM1 gene; (ii) a lower total bilirubin was associated with the 3.7-kb deletion at HBA gene, rs2070744_T allele at NOS3 gene, and haplotype 9 within VCAM1 promoter; and (iii) a diminished reticulocyte count was associated with the 3.7-kb deletion at HBA, whereas an increased count was associated with rs1984112_G allele at CD36 gene. On the whole, our findings suggest a complex genetic architecture for the sickle cell anaemia haemolysis process involving multiple pathways, namely control of vascular cell adhesion, NO synthesis and erythrocyte volume and haemoglobinisation.

  13. Plasmodium chabaudi-Infected Erythrocytes Adhere to CD36 and Bind to Microvascular Endothelial Cells in an Organ-Specific Way

    PubMed Central

    Mota, Maria M.; Jarra, William; Hirst, Elizabeth; Patnaik, Pradeep K.; Holder, Anthony A.

    2000-01-01

    Adherence of erythrocytes infected with Plasmodium falciparum to microvascular endothelial cells (sequestration) is considered to play an important role in parasite virulence and pathogenesis. However, the real importance of sequestration for infection and disease has never been fully assessed. The absence of an appropriate in vivo model for sequestration has been a major barrier. We have examined the rodent malaria parasite Plasmodium chabaudi chabaudi AS in mice as a potential model. Erythrocytes infected with this parasite adhere in vitro to purified CD36, a critical endothelium receptor for binding P. falciparum-infected erythrocytes. P. c. chabaudi-infected erythrocytes adhere in vitro to endothelial cells in a gamma interferon-dependent manner, suggesting the involvement of additional adhesion molecules in the binding process, as is also the case with P. falciparum-infected cells. Furthermore, plasma or sera from infected and hyperimmune mice, respectively, have the ability to block binding of infected erythrocytes to endothelial cells. In vivo, erythrocytes containing mature P. c. chabaudi parasites are sequestered from the peripheral circulation. Sequestration is organ specific, occurring primarily in the liver, although intimate contact between infected erythrocytes and endothelial cells is also observed in the spleen and brain. The results are discussed in the context of the use of this model to study (i) the relationship between endothelial cell activation and the level of sequestration and (ii) the primary function of sequestration in malaria infection. PMID:10858230

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Free Fatty Acid Storage in Human Visceral and Subcutaneous Adipose Tissue

    PubMed Central

    Ali, Asem H.; Koutsari, Christina; Mundi, Manpreet; Stegall, Mark D.; Heimbach, Julie K.; Taler, Sandra J.; Nygren, Jonas; Thorell, Anders; Bogachus, Lindsey D.; Turcotte, Lorraine P.; Bernlohr, David; Jensen, Michael D.

    2011-01-01

    OBJECTIVE Because direct adipose tissue free fatty acid (FFA) storage may contribute to body fat distribution, we measured FFA (palmitate) storage rates and fatty acid (FA) storage enzymes/proteins in omental and abdominal subcutaneous fat. RESEARCH DESIGN AND METHODS Elective surgery patients received a bolus of [1-14C]palmitate followed by omental and abdominal subcutaneous fat biopsies to measure direct FFA storage. Long chain acyl-CoA synthetase (ACS) and diacylglycerol acyltransferase activities, CD36, fatty acid-binding protein, and fatty acid transport protein 1 were measured. RESULTS Palmitate tracer storage (dpm/g adipose lipid) and calculated palmitate storage rates were greater in omental than abdominal subcutaneous fat in women (1.2 ± 0.8 vs. 0.7 ± 0.4 μmol ⋅ kg adipose lipid−1 ⋅ min−1, P = 0.005) and men (0.7 ± 0.2 vs. 0.2 ± 0.1, P < 0.001), and both were greater in women than men (P < 0.0001). Abdominal subcutaneous adipose tissue palmitate storage rates correlated with ACS activity (women: r = 0.66, P = 0.001; men: r = 0.70, P = 0.007); in men, CD36 was also independently related to palmitate storage rates. The content/activity of FA storage enzymes/proteins in omental fat was dramatically lower in those with more visceral fat. In women, only omental palmitate storage rates were correlated (r = 0.54, P = 0.03) with ACS activity. CONCLUSIONS Some adipocyte FA storage factors correlate with direct FFA storage, but sex differences in this process in visceral fat do not account for sex differences in visceral fatness. The reduced storage proteins in those with greater visceral fat suggest that the storage factors we measured are not a predominant cause of visceral adipose tissue accumulation. PMID:21810594

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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)

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. A functional, genome-wide evaluation of liposensitive yeast identifies the "ARE2 required for viability" (ARV1) gene product as a major component of eukaryotic fatty acid resistance.

    PubMed

    Ruggles, Kelly V; Garbarino, Jeanne; Liu, Ying; Moon, James; Schneider, Kerry; Henneberry, Annette; Billheimer, Jeff; Millar, John S; Marchadier, Dawn; Valasek, Mark A; Joblin-Mills, Aidan; Gulati, Sonia; Munkacsi, Andrew B; Repa, Joyce J; Rader, Dan; Sturley, Stephen L

    2014-02-14

    The toxic subcellular accumulation of lipids predisposes several human metabolic syndromes, including obesity, type 2 diabetes, and some forms of neurodegeneration. To identify pathways that prevent lipid-induced cell death, we performed a genome-wide fatty acid sensitivity screen in Saccharomyces cerevisiae. We identified 167 yeast mutants as sensitive to 0.5 mm palmitoleate, 45% of which define pathways that were conserved in humans. 63 lesions also impacted the status of the lipid droplet; however, this was not correlated to the degree of fatty acid sensitivity. The most liposensitive yeast strain arose due to deletion of the "ARE2 required for viability" (ARV1) gene, encoding an evolutionarily conserved, potential lipid transporter that localizes to the endoplasmic reticulum membrane. Down-regulation of mammalian ARV1 in MIN6 pancreatic β-cells or HEK293 cells resulted in decreased neutral lipid synthesis, increased fatty acid sensitivity, and lipoapoptosis. Conversely, elevated expression of human ARV1 in HEK293 cells or mouse liver significantly increased triglyceride mass and lipid droplet number. The ARV1-induced hepatic triglyceride accumulation was accompanied by up-regulation of DGAT1, a triglyceride synthesis gene, and the fatty acid transporter, CD36. Furthermore, ARV1 was identified as a transcriptional of the protein peroxisome proliferator-activated receptor α (PPARα), a key regulator of lipid homeostasis whose transcriptional targets include DGAT1 and CD36. These results implicate ARV1 as a protective factor in lipotoxic diseases due to modulation of fatty acid metabolism. In conclusion, a lipotoxicity-based genetic screen in a model microorganism has identified 75 human genes that may play key roles in neutral lipid metabolism and disease.

  1. A Functional, Genome-wide Evaluation of Liposensitive Yeast Identifies the “ARE2 Required for Viability” (ARV1) Gene Product as a Major Component of Eukaryotic Fatty Acid Resistance*

    PubMed Central

    Ruggles, Kelly V.; Garbarino, Jeanne; Liu, Ying; Moon, James; Schneider, Kerry; Henneberry, Annette; Billheimer, Jeff; Millar, John S.; Marchadier, Dawn; Valasek, Mark A.; Joblin-Mills, Aidan; Gulati, Sonia; Munkacsi, Andrew B.; Repa, Joyce J.; Rader, Dan; Sturley, Stephen L.

    2014-01-01

    The toxic subcellular accumulation of lipids predisposes several human metabolic syndromes, including obesity, type 2 diabetes, and some forms of neurodegeneration. To identify pathways that prevent lipid-induced cell death, we performed a genome-wide fatty acid sensitivity screen in Saccharomyces cerevisiae. We identified 167 yeast mutants as sensitive to 0.5 mm palmitoleate, 45% of which define pathways that were conserved in humans. 63 lesions also impacted the status of the lipid droplet; however, this was not correlated to the degree of fatty acid sensitivity. The most liposensitive yeast strain arose due to deletion of the “ARE2 required for viability” (ARV1) gene, encoding an evolutionarily conserved, potential lipid transporter that localizes to the endoplasmic reticulum membrane. Down-regulation of mammalian ARV1 in MIN6 pancreatic β-cells or HEK293 cells resulted in decreased neutral lipid synthesis, increased fatty acid sensitivity, and lipoapoptosis. Conversely, elevated expression of human ARV1 in HEK293 cells or mouse liver significantly increased triglyceride mass and lipid droplet number. The ARV1-induced hepatic triglyceride accumulation was accompanied by up-regulation of DGAT1, a triglyceride synthesis gene, and the fatty acid transporter, CD36. Furthermore, ARV1 was identified as a transcriptional of the protein peroxisome proliferator-activated receptor α (PPARα), a key regulator of lipid homeostasis whose transcriptional targets include DGAT1 and CD36. These results implicate ARV1 as a protective factor in lipotoxic diseases due to modulation of fatty acid metabolism. In conclusion, a lipotoxicity-based genetic screen in a model microorganism has identified 75 human genes that may play key roles in neutral lipid metabolism and disease. PMID:24273168

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Acrolein-induced oxidative stress in NAD(P)H Oxidase Subunit gp91phox knock-out mice and its modulation of NFκB and CD36.

    PubMed

    Yousefipour, Zivar; Zhang, Chelsea; Monfareed, Mahdieh; Walker, James; Newaz, Mohammad

    2013-11-01

    An essential component of NAD(P)H, gp91phox, maintains the functionality of the enzyme in producing oxygen radicals. NAD(P)H oxidase plays an important role in oxidative stress but its precise contribution in acrolein-induced toxicity was not explored. We examined the involvement of NAD(P)H oxidase and other oxidant system in acrolein toxicity using gp91phox knockout mice. Male gp91phox knockout (KO) mice (20-25 gm) or wild type (WT) controls were treated with acrolein (0.5 μg/kg; 1 week). Animals were sacrificed and the liver was used to determine biochemical parameters. Knockout mice generated low (1.43 ±.02 pg/μg protein) free radicals as evident in 8-Isoprostane compared with the WT mice (2.19 ± 0.1). Acrolein increased 8-Isoprostane in WT (P<.05) and KO (p<.05) mice. Xanthine Oxidase (XO) activity was higher (p<.05) in KO (0.56 ± 0.06 μ unit/μg protein) than WT mice. Acrolein increased XO in KO mice, but significantly increased it only in WT. Cycloxygenase (COX) activity was not different between WT and KO mice, although acroelin increased COX in WT. Knockout mice exhibited a significantly low (2.1 ± 0.2 μmol/mg protein) total antioxidant status (TAS) compared with the WT (3.5 ± 0.3). Acrolein reduced TAS in both WT and KO mice equally. Baseline NFκB was significantly higher in KO mice, although acrolein increased NFκB in WT but not in KO. CD36 was higher (p<.05) in KO mice than the WT and acrolein increased (p<.05) CD36 further in KO but not in WT mice. These data suggest that NAD(P)H oxidase contributes significantly in acrolein-induced oxidative stress. We also suggests that in the absence of NAD(P)H oxidase XO plays a definitive role together with reduced antioxidant ability to compound the toxic effects of acrolein. We propose that in absence of NAD(P)H oxidase a different signaling process may involve that utilizes CD36 besides NFκB.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  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. Adenosine monophosphate-activated protein kinase activation, substrate transporter translocation, and metabolism in the contracting hyperthyroid rat heart.

    PubMed

    Heather, Lisa C; Cole, Mark A; Atherton, Helen J; Coumans, Will A; Evans, Rhys D; Tyler, Damian J; Glatz, Jan F C; Luiken, Joost J F P; Clarke, Kieran

    2010-01-01

    Thyroid hormones can modify cardiac metabolism via multiple molecular mechanisms, yet their integrated effect on overall substrate metabolism is poorly understood. Here we determined the effect of hyperthyroidism on substrate metabolism in the isolated, perfused, contracting rat heart. Male Wistar rats were injected for 7 d with T(3) (0.2 mg/kg x d ip). Plasma free fatty acids increased by 97%, heart weights increased by 33%, and cardiac rate pressure product, an indicator of contractile function, increased by 33% in hyperthyroid rats. Insulin-stimulated glycolytic rates and lactate efflux rates were increased by 33% in hyperthyroid rat hearts, mediated by an increased insulin-stimulated translocation of the glucose transporter GLUT4 to the sarcolemma. This was accompanied by a 70% increase in phosphorylated AMP-activated protein kinase (AMPK) and a 100% increase in phosphorylated acetyl CoA carboxylase, confirming downstream signaling from AMPK. Fatty acid oxidation rates increased in direct proportion to the increased heart weight and rate pressure product in the hyperthyroid heart, mediated by synchronized changes in mitochondrial enzymes and respiration. Protein levels of the fatty acid transporter, fatty acid translocase (FAT/CD36), were reduced by 24% but were accompanied by a 19% increase in the sarcolemmal content of fatty acid transport protein 1 (FATP1). Thus, the relationship between fatty acid metabolism, cardiac mass, and contractile function was maintained in the hyperthyroid heart, associated with a sarcolemmal reorganization of fatty acid transporters. The combined effects of T(3)-induced AMPK activation and insulin stimulation were associated with increased sarcolemmal GLUT4 localization and glycolytic flux in the hyperthyroid heart. PMID:19940039

  10. 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...

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.