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Sample records for activated carbon rac

  1. Implementation Of Palladized Iron-Impregnated Reactive Activated Carbon (RAC) System For PCBs Cleanup: Effects Of PCB Loading, Reaction pH, And Co-Existing NOM And Ionic Species

    EPA Science Inventory

    For the treatment of chlorinated organic compounds in the environment, such as polychlorinated biphenyls (PCBs), we have developed reactive activated carbon (RAC) impregnated with Fe/Pd bimetallic nanoparticles. The RAC system can couple adsorption of PCBs to activated carbon wi...

  2. Supervillin Binds the Rac/Rho-GEF Trio and Increases Trio-mediated Rac1 Activation

    PubMed Central

    Son, Kyonghee; Smith, Tara C.; Luna, Elizabeth J.

    2015-01-01

    We investigated cross-talk between the membrane-associated, myosin II-regulatory protein supervillin and the actin-regulatory small GTPases Rac1, RhoA, and Cdc42. Supervillin knockdown reduced Rac1-GTP loading, but not the GTP loading of RhoA or Cdc42, in HeLa cells with normal levels of the Rac1-activating protein Trio. No reduction in Rac1-GTP loading was observed when supervillin levels were reduced in Trio-depleted cells. Conversely, overexpression of supervillin isoform 1 (SV1) or, especially, isoform 4 (SV4) increased Rac1 activation. Inhibition of the Trio-mediated Rac1 guanine nucleotide exchange (GEF) activity with ITX3 partially blocked the SV4-mediated increase in Rac1-GTP. Both SV4 and SV1 co-localized with Trio at or near the plasma membrane in ruffles and cell surface projections. Two sequences within supervillin bound directly to Trio spectrin repeats 4–7: SV1-171, which contains N-terminal residues found in both SV1 and SV4 and the SV4-specific differentially spliced coding exons 3, 4, and 5 within SV4 (SV4-E345; SV4 amino acids 276 – 669). In addition, SV4-E345 interacted with the homologous sequence in rat kalirin (repeats 4–7, amino acids 531 – 1101). Overexpressed SV1-174 and SV4-E345 affected Rac1-GTP loading, but only in cells with endogenous levels of Trio. Trio residues 771 – 1057, which contain both supervillin-interaction sites, exerted a dominant-negative effect on cell spreading. Supervillin and Trio knockdowns, separately or together, inhibited cell spreading, suggesting that supervillin regulates the Rac1 guanine nucleotide exchange activity of Trio, and potentially also kalirin, during cell spreading and lamellipodia extension. PMID:25655724

  3. Rac1 activity regulates proliferation of aggressive metastatic melanoma

    SciTech Connect

    Bauer, Natalie N. Chen Yihwen; Samant, Rajeev S.; Shevde, Lalita A.; Fodstad, Oystein

    2007-11-01

    Molecular mechanisms underlying the different capacity of two in vivo selected human melanoma cell variants to form experimental metastases were studied. The doubling times of the FEMX-I and FEMX-V cell sublines in vitro were 15 and 25 h, respectively. The invasive capacity of FEMX-I cells was 8-fold higher than FEMX-V cells, and the time to form approximately 10 mm s.c. tumors in nude mice was 21 versus 35 days. FEMX-I displayed a spindle-like formation in vitro, whereas FEMX-V cells had a rounded shape. Hence, we examined known determinants of cell shape and proliferation, the small GTPases. The four studied showed equal expression in both cell types, but Rac1 activity was significantly decreased in FEMX-V cells. Rac1 stimulates NF{kappa}B, and we found that endogenous NF{kappa}B activity of FEMX-V cells was 2% of that of FEMX-I cells. Inhibition of Rac1 resulted in blocked NF{kappa}B activity. Specific inhibition of either Rac1 or NF{kappa}B significantly reduced proliferation and invasion of FEMX-I cells, the more pronounced effects observed with Rac1 inhibition. These data indicate that Rac1 activity in FEMX cells regulates cell proliferation and invasion, in part via its effect on NF{kappa}B, signifying Rac1 as a key molecule in melanoma progression and metastasis.

  4. Non-prenylatable, cytosolic Rac1 alters neurite outgrowth while retaining the ability to be activated.

    PubMed

    Reddy, Jairus M; Samuel, Filsy G; McConnell, Jordan A; Reddy, Cristina P; Beck, Brian W; Hynds, DiAnna L

    2015-03-01

    Rac1 is an important regulator of axon extension, cell migration and actin reorganization. Like all Rho guanine triphosphatases (GTPases), Rac1 is targeted to the membrane by the addition of a geranylgeranyl moiety, an action thought to result in Rac1 guanosine triphosphate (GTP) binding. However, the role that Rac1 localization plays in its activation (GTP loading) and subsequent activation of effectors is not completely clear. To address this, we developed a non-prenylatable emerald green fluorescent protein (EmGFP)-Rac1 fusion protein (EmGFP-Rac1(C189A)) and assessed how expressing this construct affected neurite outgrowth, Rac1 localization and activation in neuroblastoma cells. Expression of EmGFP-Rac1(C189A) increased localization to the cytosol and induced cell clustering while increasing neurite initiation. EmGFP-Rac1(C189A) expression also increased Rac1 activation in the cytosol, compared to cells expressing wild-type Rac1 (EmGFP-Rac1). These results suggest that activation of Rac1 may not require plasma membrane localization, potentially leading to differential activation of cytosolic signaling pathways that alter cell morphology. Understanding the consequences of differential localization and activation of Rho GTPases, including Rac1, could lead to new therapeutic targets for treating neurological disorders. PMID:25479592

  5. Activated Rac1 requires gp130 for Stat3 activation, cell proliferation and migration

    SciTech Connect

    Arulanandam, Rozanne; Geletu, Mulu; Feracci, Helene; Raptis, Leda

    2010-03-10

    Rac1 (Rac) is a member of the Rho family of small GTPases which controls cell migration by regulating the organization of actin filaments. Previous results suggested that mutationally activated forms of the Rho GTPases can activate the Signal Transducer and Activator of Transcription-3 (Stat3), but the exact mechanism is a matter of controversy. We recently demonstrated that Stat3 activity of cultured cells increases dramatically following E-cadherin engagement. To better understand this pathway, we now compared Stat3 activity levels in mouse HC11 cells before and after expression of the mutationally activated Rac1 (Rac{sup V12}), at different cell densities. The results revealed for the first time a dramatic increase in protein levels and activity of both the endogenous Rac and Rac{sup V12} with cell density, which was due to inhibition of proteasomal degradation. In addition, Rac{sup V12}-expressing cells had higher Stat3, tyrosine-705 phosphorylation and activity levels at all densities, indicating that Rac{sup V12} is able to activate Stat3. Further examination of the mechanism of Stat3 activation showed that Rac{sup V12} expression caused a surge in mRNA of Interleukin-6 (IL6) family cytokines, known potent Stat3 activators. Knockdown of gp130, the common subunit of this family reduced Stat3 activity, indicating that these cytokines may be responsible for the Stat3 activation by Rac{sup V12}. The upregulation of IL6 family cytokines was required for cell migration and proliferation induced by Rac{sup V12}, as shown by gp130 knockdown experiments, thus demonstrating that the gp130/Stat3 axis represents an essential effector of activated Rac for the regulation of key cellular functions.

  6. How to staff for RACs.

    PubMed

    Brocato, Lori; Hirschl, Nancy; Padfield, Stanley

    2010-01-01

    To meet the challenges presented by recovery audit contractors (RACs), hospitals should perform six tasks that require appropriate investments in staff: conduct a financial risk assessment of the impact of RAC reviews on the organization; establish a RAC team and assign a coordinator; receive and fill RAC requests; track RAC activity; manage RAC appeals; analyze RAC audit outcomes. PMID:20088469

  7. Inhibition of Rac1 Activity in the Hippocampus Impairs the Forgetting of Contextual Fear Memory.

    PubMed

    Jiang, Lizhu; Mao, Rongrong; Zhou, Qixin; Yang, Yuexiong; Cao, Jun; Ding, Yuqiang; Yang, Yuan; Zhang, Xia; Li, Lingjiang; Xu, Lin

    2016-03-01

    Fear is crucial for survival, whereas hypermnesia of fear can be detrimental. Inhibition of the Rac GTPase is recently reported to impair the forgetting of initially acquired memory in Drosophila. Here, we investigated whether inhibition of Rac1 activity in rat hippocampus could contribute to the hypermnesia of contextual fear. We found that spaced but not massed training of contextual fear conditioning caused inhibition of Rac1 activity in the hippocampus and heightened contextual fear. Furthermore, intrahippocampal injection of the Rac1 inhibitor NSC23766 heightened contextual fear in massed training, while Rac1 activator CN04-A weakened contextual fear in spaced training rats. Our study firstly demonstrates that contextual fear memory in rats is actively regulated by Rac1 activity in the hippocampus, which suggests that the forgetting impairment of traumatic events in posttraumatic stress disorder may be contributed to the pathological inhibition of Rac1 activity in the hippocampus. PMID:25613020

  8. Fluctuation of Rac1 activity is associated with the phenotypic and transcriptional heterogeneity of glioma cells.

    PubMed

    Yukinaga, Hiroko; Shionyu, Clara; Hirata, Eishu; Ui-Tei, Kumiko; Nagashima, Takeshi; Kondo, Shinji; Okada-Hatakeyama, Mariko; Naoki, Honda; Matsuda, Michiyuki

    2014-04-15

    Phenotypic heterogeneity of cancer cells is caused not only by genetic and epigenetic alterations but also by stochastic variation of intracellular signaling molecules. Using cells that stably express Förster resonance energy transfer (FRET) biosensors, we show here a correlation between a temporal fluctuation in the activity of Rac1 and the invasive properties of C6 glioma cells. By using long-term time-lapse imaging, we found that Rac1 activity in C6 glioma cells fluctuated over a timescale that was substantially longer than that of the replication cycle. Because the relative level of Rac1 activity in each cell was unaffected by a suspension-adhesion procedure, we were able to sort C6 glioma cells according to the levels of Rac1 activity, yielding Rac1(high) and Rac1(low) cells. The Rac1(high) cells invaded more efficiently than did Rac1(low) cells in a Matrigel invasion assay. We assessed the transcriptional profiles of Rac1(high) and Rac1(low) cells and performed gene ontology analysis. Among the 14 genes that were most associated with the term 'membrane' (membrane-related genes) in Rac1(high) cells, we identified four genes that were associated with glioma invasion and Rac1 activity by using siRNA knockdown experiments. Among the transcription factors upregulated in Rac1(high) cells, Egr2 was found to positively regulate expression of the four membrane-related invasion-associated genes. The identified signaling network might cause the fluctuations in Rac1 activity and the heterogeneity in the invasive capacity of glioma cells. PMID:24522191

  9. RAC1 activation drives pathologic interactions between the epidermis and immune cells.

    PubMed

    Winge, Mårten C G; Ohyama, Bungo; Dey, Clara N; Boxer, Lisa M; Li, Wei; Ehsani-Chimeh, Nazanin; Truong, Allison K; Wu, Diane; Armstrong, April W; Makino, Teruhiko; Davidson, Matthew; Starcevic, Daniela; Kislat, Andreas; Nguyen, Ngon T; Hashimoto, Takashi; Homey, Bernard; Khavari, Paul A; Bradley, Maria; Waterman, Elizabeth A; Marinkovich, M Peter

    2016-07-01

    Interactions between the epidermis and the immune system govern epidermal tissue homeostasis. These epidermis-immune interactions are altered in the inflammatory disease psoriasis; however, the pathways that underlie this aberrant immune response are not well understood. Here, we determined that Ras-related C3 botulinum toxin substrate 1 (RAC1) is a key mediator of epidermal dysfunction. RAC1 activation was consistently elevated in psoriatic epidermis and primary psoriatic human keratinocytes (PHKCs) exposed to psoriasis-related stimuli, but not in skin from patients with basal or squamous cell carcinoma. Expression of a constitutively active form of RAC1 (RACV12) in mice resulted in the development of lesions similar to those of human psoriasis that required the presence of an intact immune system. RAC1V12-expressing mice and human psoriatic skin showed similar RAC1-dependent signaling as well as transcriptional overlap of differentially expressed epidermal and immune pathways. Coculture of PHKCs with immunocytes resulted in the upregulation of RAC1-dependent proinflammatory cytokines, an effect that was reproduced by overexpressing RAC1 in normal human keratinocytes. In keratinocytes, modulating RAC1 activity altered differentiation, proliferation, and inflammatory pathways, including STAT3, NFκB, and zinc finger protein 750 (ZNF750). Finally, RAC1 inhibition in xenografts composed of human PHKCs and immunocytes abolished psoriasiform hyperplasia and inflammation in vivo. These studies implicate RAC1 as a potential therapeutic target for psoriasis and as a key orchestrator of pathologic epidermis-immune interactions. PMID:27294528

  10. Characterization of the Rac-GAP (Rac-GTPase-activating protein) activity of beta2-chimaerin, a 'non-protein kinase C' phorbol ester receptor.

    PubMed Central

    Caloca, Maria Jose; Wang, HongBin; Kazanietz, Marcelo G

    2003-01-01

    The regulation and function of beta2-chimaerin, a novel receptor for the phorbol ester tumour promoters and the second messenger DAG (diacylglycerol), is largely unknown. As with PKC (protein kinase C) isoenzymes, phorbol esters bind to beta2-chimaerin with high affinity and promote its subcellular distribution. beta2-Chimaerin has GAP (GTPase-activating protein) activity for the small GTP-binding protein Rac1, but for not Cdc42 or RhoA. We show that acidic phospholipids enhanced its catalytic activity markedly in vitro, but the phorbol ester PMA had no effect. beta2-Chimaerin and other chimaerin isoforms decreased cellular levels of Rac-GTP markedly in COS-1 cells and impaired GTP loading on to Rac upon EGF (epidermal growth factor) receptor stimulation. Deletional and mutagenesis analysis determined that the beta2-chimaerin GAP domain is essential for this effect. Interestingly, PMA has a dual effect on Rac-GTP levels in COS-1 cells. PMA increased Rac-GTP levels in the absence of a PKC inhibitor, whereas under conditions in which PKC activity is inhibited, PMA markedly decreased Rac-GTP levels and potentiated the effect of beta2-chimaerin. Chimaerin isoforms co-localize at the plasma membrane with active Rac, and these results were substantiated by co-immunoprecipitation assays. In summary, the novel phorbol ester receptor beta2-chimaerin regulates the activity of the Rac GTPase through its GAP domain, leading to Rac inactivation. These results strongly emphasize the high complexity of DAG signalling due to the activation of PKC-independent pathways, and cast doubts regarding the selectivity of phorbol esters and DAG analogues as selective PKC activators. PMID:12877655

  11. Melatonin suppresses hypoxia-induced migration of HUVECs via inhibition of ERK/Rac1 activation.

    PubMed

    Yang, Ling; Zheng, Jianchao; Xu, Rui; Zhang, Yujie; Gu, Luo; Dong, Jing; Zhu, Yichao; Zhou, Ruijue; Zheng, Lu; Zhang, Xiaoying; Du, Jun

    2014-01-01

    Melatonin, a naturally-occurring hormone, possesses antioxidant properties and ameliorates vascular endothelial dysfunction. In this study, we evaluate the impact of melatonin on the migratory capability of human umbilical vein endothelial cells (HUVECs) to hypoxia and further investigate whether ERK/Rac1 signaling is involved in this process. Here, we found that melatonin inhibited hypoxia-stimulated hypoxia-inducible factor-1α (HIF-1α) expression and cell migration in a dose-dependent manner. Mechanistically, melatonin inhibited Rac1 activation and suppressed the co-localized Rac1 and F-actin on the membrane of HUVECs under hypoxic condition. In addition, the blockade of Rac1 activation with ectopic expression of an inactive mutant form of Rac1-T17N suppressed HIF-1α expression and cell migration in response to hypoxia, as well, but constitutive activation of Rac1 mutant Rac1-V12 restored HIF-1α expression, preventing the inhibition of melatonin on cell migration. Furthermore, the anti-Rac1 effect of melatonin in HUVECs appeared to be associated with its inhibition of ERK phosphorylation, but not that of the PI3k/Akt signaling pathway. Taken together, our work indicates that melatonin exerts an anti-migratory effect on hypoxic HUVECs by blocking ERK/Rac1 activation and subsequent HIF-1α upregulation. PMID:25123138

  12. Simultaneous and independent tuning of RhoA and Rac1 activity with orthogonally inducible promoters

    PubMed Central

    MacKay, Joanna L.

    2014-01-01

    The GTPases RhoA and Rac1 are key regulators of cell spreading, adhesion, and migration, and they exert distinct effects on the actin cytoskeleton. While RhoA classically stimulates stress fiber assembly and contraction, Rac1 promotes branched actin polymerization and membrane protrusion. These competing influences are reinforced by antagonistic crosstalk between RhoA and Rac1, which has complicated efforts to identify the specific mechanisms by which each GTPase regulates cell behavior. We therefore wondered whether RhoA and Rac1 are intrinsically coupled or whether they can be manipulated independently. To address this question, we placed constitutively active (CA) RhoA under a doxycycline-inducible promoter and CA Rac1 under an orthogonal cumate-inducible promoter, and we stably introduced both constructs into glioblastoma cells. We found that doxycycline addition increased RhoA activity without altering Rac1 and similarly cumate addition increased Rac1 activity without altering RhoA. Furthermore, co-expression of both mutants enabled high activation of RhoA and Rac1 simultaneously. When cells were cultured on collagen hydrogels, RhoA activation prevented cell spreading and motility, whereas Rac1 activation stimulated migration and dynamic cell protrusions. Interestingly, high activation of both GTPases induced a third phenotype, in which cells migrated at intermediate speeds similar to control cells but also aggregated into large, contractile clusters. In addition, we demonstrate dynamic and reversible switching between high RhoA and high Rac1 phenotypes. Overall, this approach represents a unique way to access different combinations of RhoA and Rac1 activity levels in a single cell and may serve as a valuable tool for multiplexed dissection and control of mechanobiological signals. PMID:25044255

  13. Regulation of Rac1 translocation and activation by membrane domains and their boundaries

    PubMed Central

    Moissoglu, Konstadinos; Kiessling, Volker; Wan, Chen; Hoffman, Brenton D.; Norambuena, Andres; Tamm, Lukas K.; Schwartz, Martin Alexander

    2014-01-01

    ABSTRACT The activation of Rac1 and related Rho GTPases involves dissociation from Rho GDP-dissociation inhibitor proteins and translocation to membranes, where they bind effectors. Previous studies have suggested that the binding of Rac1 to membranes requires, and colocalizes with, cholesterol-rich liquid-ordered (lo) membrane domains (lipid rafts). Here, we have developed a fluorescence resonance energy transfer (FRET) assay that robustly detects Rac1 membrane targeting in living cells. Surprisingly, FRET with acceptor constructs that were targeted to either raft or non-raft areas indicated that Rac1 was present in both regions. Functional studies showed that Rac1 localization to non-raft regions decreased GTP loading as a result of inactivation by GTPase-activating proteins. In vitro, Rac1 translocation to supported lipid bilayers also required lo domains, yet Rac1 was concentrated in the liquid-disordered (ld) phase. Single-molecule analysis demonstrated that translocation occurred preferentially at lo–ld boundaries. These results, therefore, suggest that Rac1 translocates to the membrane at domain boundaries, then diffuses into raft and non-raft domains, which controls interactions. These findings resolve discrepancies in our understanding of Rac biology and identify novel mechanisms by which lipid rafts modulate Rho GTPase signaling. PMID:24695858

  14. Inhibition of Rac1 activity in the hippocampus impaired extinction of contextual fear.

    PubMed

    Jiang, Lizhu; Mao, Rongrong; Tong, Jianbin; Li, Jinnan; Chai, Anping; Zhou, Qixin; Yang, Yuexiong; Wang, Liping; Li, Lingjiang; Xu, Lin

    2016-10-01

    Promoting extinction of fear memory is the main treatment of fear disorders, especially post-traumatic stress disorder (PTSD). However, fear extinction is often incomplete in these patients. Our previous study had shown that Rac1 activity in hippocampus plays a crucial role in the learning of contextual fear memory in rats. Here, we further investigated whether Rac1 activity also modulated the extinction of contextual fear memory. We found that massed extinction obviously upregulated hippocampal Rac1 activity and induced long-term extinction of contextual fear in rats. Intrahippocampal injection of the Rac1 inhibitor NSC23766 prevents extinction of contextual fear in massed extinction training rats. In contrast, long-spaced extinction downregulated Rac1 activity and caused less extinction. And Rac1 activator CN04-A promotes extinction of contextual fear in long-spaced extinction rats. Our study demonstrates that inhibition of Rac1 activity in the hippocampus impaired extinction of contextual fear, suggesting that modulating Rac1 activity of the hippocampus may be promising therapy of fear disorders. PMID:27329554

  15. Hippocampal Activation of Rac1 Regulates the Forgetting of Object Recognition Memory.

    PubMed

    Liu, Yunlong; Du, Shuwen; Lv, Li; Lei, Bo; Shi, Wei; Tang, Yikai; Wang, Lianzhang; Zhong, Yi

    2016-09-12

    Forgetting is a universal feature for most types of memories. The best-defined and extensively characterized behaviors that depict forgetting are natural memory decay and interference-based forgetting [1, 2]. Molecular mechanisms underlying the active forgetting remain to be determined for memories in vertebrates. Recent progress has begun to unravel such mechanisms underlying the active forgetting [3-11] that is induced through the behavior-dependent activation of intracellular signaling pathways. In Drosophila, training-induced activation of the small G protein Rac1 mediates natural memory decay and interference-based forgetting of aversive conditioning memory [3]. In mice, the activation of photoactivable-Rac1 in recently potentiated spines in a motor learning task erases the motor memory [12]. These lines of evidence prompted us to investigate a role for Rac1 in time-based natural memory decay and interference-based forgetting in mice. The inhibition of Rac1 activity in hippocampal neurons through targeted expression of a dominant-negative Rac1 form extended object recognition memory from less than 72 hr to over 72 hr, whereas Rac1 activation accelerated memory decay within 24 hr. Interference-induced forgetting of this memory was correlated with Rac1 activation and was completely blocked by inhibition of Rac1 activity. Electrophysiological recordings of long-term potentiation provided independent evidence that further supported a role for Rac1 activation in forgetting. Thus, Rac1-dependent forgetting is evolutionarily conserved from invertebrates to vertebrates. PMID:27593377

  16. Corticosterone regulates fear memory via Rac1 activity in the hippocampus.

    PubMed

    Gan, Ping; Ding, Ze-Yang; Gan, Cheng; Mao, Rong-Rong; Zhou, Heng; Xu, Lin; Zhou, Qi-Xin

    2016-09-01

    Stressful events can generate enduring memories, which may induce certain psychiatric disorders such as post-traumatic stress disorder (PTSD). However, the underlying molecular mechanisms in these processes remain unclear. In this study, we examined whether the active form of the small G protein Rac1, Rac1-GTP, is involved in fear memory. Firstly, we detected the time course changes of Rac1-GTP after foot shocks (a strong stressor) and exogenous corticosterone (CORT) treatment. The data showed that stress and CORT induced the downregulation of Rac1-GTP in the hippocampus. Changes in the serum CORT level were negatively correlated with the level of Rac1-GTP. Additionally, a glucocorticoid receptor antagonist, RU38486, not only recovered the expression of Rac1-GTP but also impaired fear memory. Furthermore, systemic administration of NSC23766, an inhibitor of Rac1-GTP, improved fear memory at 1.5 and 24h. Therefore, Rac1 activity plays a critical role in stress-related cognition and may be a potential target in stress-related disorders. PMID:27249795

  17. Rac1 Protein Regulates Glycogen Phosphorylase Activation and Controls Interleukin (IL)-2-dependent T Cell Proliferation*

    PubMed Central

    Arrizabalaga, Onetsine; Lacerda, Hadriano M.; Zubiaga, Ana M.; Zugaza, José L.

    2012-01-01

    Small GTPases of the Rho family have been implicated in important cellular processes such as cell migration and adhesion, protein secretion, and/or gene transcription. In the lymphoid system, these GTPases participate in the signaling cascades that are activated after engagement of antigen receptors. However, little is known about the role that Rho GTPases play in IL-2-mediated responses. Here, we show that IL-2 induces Rac1 activation in Kit 225 T cells. We identified by mass spectrometry the muscle isoform of glycogen phosphorylase (PYGM) as a novel Rac1 effector molecule in IL-2-stimulated cells. The interaction between the active form of Rac1 (Rac1-GTP) and PYGM was established directly through a domain comprising amino acids 191–270 of PYGM that exhibits significant homology with the Rac binding domain of PAK1. The integrity of this region was crucial for PYGM activation. Importantly, IL-2-dependent cellular proliferation was inhibited upon blocking both the activation of Rac1 and the activity of PYGM. These results reveal a new role for Rac1 in cell signaling, showing that this GTPase triggers T cell proliferation upon IL-2 stimulation by associating with PYGM and modulating its enzymatic activity. PMID:22337875

  18. A novel pathway spatiotemporally activates Rac1 and redox signaling in response to fluid shear stress

    PubMed Central

    Liu, Yunhao; Collins, Caitlin; Kiosses, William B.; Murray, Ann M.; Joshi, Monika; Shepherd, Tyson R.; Fuentes, Ernesto J.

    2013-01-01

    Hemodynamic forces regulate embryonic organ development, hematopoiesis, vascular remodeling, and atherogenesis. The mechanosensory stimulus of blood flow initiates a complex network of intracellular pathways, including activation of Rac1 GTPase, establishment of endothelial cell (EC) polarity, and redox signaling. The activity of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase can be modulated by the GTP/GDP state of Rac1; however, the molecular mechanisms of Rac1 activation by flow are poorly understood. Here, we identify a novel polarity complex that directs localized Rac1 activation required for downstream reactive oxygen species (ROS) production. Vav2 is required for Rac1 GTP loading, whereas, surprisingly, Tiam1 functions as an adaptor in a VE-cadherin–p67phox–Par3 polarity complex that directs localized activation of Rac1. Furthermore, loss of Tiam1 led to the disruption of redox signaling both in vitro and in vivo. Our results describe a novel molecular cascade that regulates redox signaling by the coordinated regulation of Rac1 and by linking components of the polarity complex to the NADPH oxidase. PMID:23733346

  19. Inhibition of Rac1 activity by controlled release of NSC23766 from chitosan microspheres effectively ameliorates osteoarthritis development in vivo

    PubMed Central

    Zhu, Shouan; Lu, Ping; Liu, Huanhuan; Chen, Pengfei; Wu, Yan; Wang, Yanyan; Sun, Heng; Zhang, Xiaolei; Xia, Qingqing; Heng, Boon Chin; Zhou, Yiting; Ouyang, Hong Wei

    2015-01-01

    Background Osteoarthritis (OA) is a degenerative joint disease characterised by cartilage degradation and chondrocyte hypertrophy. A recent study showed that Rac1 promoted expression of MMP13 and chondrocyte hypertrophy within the growth plate. These findings warrant further investigations on the roles of Rac1 in OA development and therapy in animal models. Objective To investigate the role and mechanistic pathway of Rac1 involvement in pathological changes of OA chondrocytes in vitro and OA development in vivo, as well as to develop a strategy of modulating Rac1 activity for OA treatment. Material and methods OA and normal cartilage from human or mice were used for immunohistochemical study and Rac1 activity assay. Chondrocytes treated with IL1β and the untreated control were subjected to the Rac1 activity assay. Chondrocytes transfected with CA-Rac1, DN-Rac1 or GFP were cultured under conditions for inducing calcification. To evaluate the effect of Rac1 in OA development, an OA model was created by anterior cruciate ligament transection in mice. CA-Rac1, DN-Rac1 and GFP lentivirus, or NSC23766, were injected intra-articularly. Joints were subjected to histological analysis. Results It was found that there is aberrant Rac1 activation in human OA cartilage. Rac1 activity could also be elevated by IL1β. Additionally, activated Rac1 promoted expression of MMP13, ADAMTS-5 and COLX by chondrocytes, partially through the β-catenin pathway. Moreover, activation of Rac1 in knee joints by CA-Rac1 lentivirus accelerated OA progression, while inhibition of Rac1 activity by DN-Rac1 lentivirus or Rac1 inhibitor NSC23766 delayed OA development. Therefore, we developed a strategy of controlled release of NSC23766 from chitosan microspheres to OA joints, which effectively protected cartilage from destruction. Conclusions These findings demonstrated that Rac1 activity is implicated in OA development. Also, controlled release of Rac1 inhibitor is a promising strategy for OA

  20. Carbon-Ion Irradiation Suppresses Migration and Invasiveness of Human Pancreatic Carcinoma Cells MIAPaCa-2 via Rac1 and RhoA Degradation

    SciTech Connect

    Fujita, Mayumi; Imadome, Kaori; Shoji, Yoshimi; Isozaki, Tetsurou; Endo, Satoshi; Yamada, Shigeru; Imai, Takashi

    2015-09-01

    Purpose: To investigate the mechanisms underlying the inhibition of cancer cell migration and invasion by carbon (C)-ion irradiation. Methods and Materials: Human pancreatic cancer cells MIAPaCa-2, AsPC-1, and BxPC-3 were treated by x-ray (4 Gy) or C-ion (0.5, 1, 2, or 4 Gy) irradiation, and their migration and invasion were assessed 2 days later. The levels of guanosine triphosphate (GTP)-bound Rac1 and RhoA were determined by the active GTPase pull-down assay with or without a proteasome inhibitor, and the binding of E3 ubiquitin ligase to GTP-bound Rac1 was examined by immunoprecipitation. Results: Carbon-ion irradiation reduced the levels of GTP-bound Rac1 and RhoA, 2 major regulators of cell motility, in MIAPaCa-2 cells and GTP-bound Rac1 in AsPC-1 and BxPC-3 cells. Proteasome inhibition reversed the effect, indicating that C-ion irradiation induced Rac1 and RhoA degradation via the ubiquitin (Ub)-proteasome pathway. E3 Ub ligase X-linked inhibitor of apoptosis protein (XIAP), which directly targets Rac1, was selectively induced in C-ion–irradiated MIAPaCa-2 cells and coprecipitated with GTP-bound Rac1 in C-ion–irradiated cells, which was associated with Rac1 ubiquitination. Cell migration and invasion reduced by C-ion radiation were restored by short interfering RNA–mediated XIAP knockdown, indicating that XIAP is involved in C-ion–induced inhibition of cell motility. Conclusion: In contrast to x-ray irradiation, C-ion treatment inhibited the activity of Rac1 and RhoA in MIAPaCa-2 cells and Rac1 in AsPC-1 and BxPC-3 cells via Ub-mediated proteasomal degradation, thereby blocking the motility of these pancreatic cancer cells.

  1. Activation of Rac1 by RhoG regulates cell migration.

    PubMed

    Katoh, Hironori; Hiramoto, Kiyo; Negishi, Manabu

    2006-01-01

    Cell migration is essential for normal development and many pathological processes. Rho-family small GTPases play important roles in this event. In particular, Rac regulates lamellipodia formation at the leading edge during migration. The small GTPase RhoG activates Rac through its effector ELMO and the ELMO-binding protein Dock180, which functions as a Rac-specific guanine nucleotide exchange factor. Here we investigated the role of RhoG in cell migration. RNA interference-mediated knockdown of RhoG in HeLa cells reduced cell migration in Transwell and scratch-wound migration assays. In RhoG-knockdown cells, activation of Rac1 and formation of lamellipodia at the leading edge in response to wounding were attenuated. By contrast, expression of active RhoG promoted cell migration through ELMO and Dock180. However, the interaction of Dock180 with Crk was dispensable for the activation of Rac1 and promotion of cell migration by RhoG. Taken together, these results suggest that RhoG contributes to the regulation of Rac activity in migrating cells. PMID:16339170

  2. Proapoptotic and antiinvasive activity of Rac1 small molecule inhibitors on malignant glioma cells

    PubMed Central

    Cardama, Georgina A; Gonzalez, Nazareno; Ciarlantini, Matias; Gandolfi Donadío, Lucia; Comin, María Julieta; Alonso, Daniel F; Menna, Pablo Lorenzano; Gomez, Daniel E

    2014-01-01

    Malignant gliomas are characterized by an intrinsic ability to invade diffusely throughout the normal brain tissue. This feature contributes mainly to the failure of existing therapies. Deregulation of small GTPases signaling, in particular Rac1 activity, plays a key role in the invasive phenotype of gliomas. Here we report the effect of ZINC69391, a specific Rac1 inhibitor developed by our group, on human glioma cell lines LN229 and U-87 MG. ZINC69391 is able to interfere with the interaction of Rac1 with Dock180, a relevant Rac1 activator in glioma invasion, and to reduce Rac1-GTP levels. The kinase Pak1, a downstream effector of Dock180–Rac1 signaling, was also downregulated upon ZINC69391 treatment. ZINC69391 reduced cell proliferation, arrested cells in G1 phase, and triggered apoptosis in glioma cells. Importantly, ZINC69391 dramatically affected cell migration and invasion in vitro, interfering with actin cytoskeleton dynamics. We also evaluated the effect of analog 1A-116, a compound derived from ZINC69391 structure. 1A-116 showed an improved antiproliferative and antiinvasive activity on glioma cells. These findings encourage further preclinical testing in clinically relevant animal models. PMID:25378937

  3. Cytotoxic Necrotizing Factor-Y Boosts Yersinia Effector Translocation by Activating Rac Protein*

    PubMed Central

    Wolters, Manuel; Boyle, Erin C.; Lardong, Kerstin; Trülzsch, Konrad; Steffen, Anika; Rottner, Klemens; Ruckdeschel, Klaus; Aepfelbacher, Martin

    2013-01-01

    Pathogenic Yersinia spp. translocate the effectors YopT, YopE, and YopO/YpkA into target cells to inactivate Rho family GTP-binding proteins and block immune responses. Some Yersinia spp. also secrete the Rho protein activator cytotoxic necrotizing factor-Y (CNF-Y), but it has been unclear how the bacteria may benefit from Rho protein activation. We show here that CNF-Y increases Yop translocation in Yersinia enterocolitica-infected cells up to 5-fold. CNF-Y strongly activated RhoA and also delayed in time Rac1 and Cdc42, but when individually expressed, constitutively active mutants of Rac1, but not of RhoA, increased Yop translocation. Consistently, knock-out or knockdown of Rac1 but not of RhoA, -B, or -C inhibited Yersinia effector translocation in CNF-Y-treated and control cells. Activation or knockdown of Cdc42 also affected Yop translocation but much less efficiently than Rac. The increase in Yop translocation induced by CNF-Y was essentially independent of the presence of YopE, YopT, or YopO in the infecting Yersinia strain, indicating that none of the Yops reported to inhibit translocation could reverse the CNF-Y effect. In summary, the CNF-Y activity of Yersinia strongly enhances Yop translocation through activation of Rac. PMID:23803609

  4. DOCK2 is a Rac activator that regulates motility and polarity during neutrophil chemotaxis.

    PubMed

    Kunisaki, Yuya; Nishikimi, Akihiko; Tanaka, Yoshihiko; Takii, Ryosuke; Noda, Mayuko; Inayoshi, Ayumi; Watanabe, Ken-ichi; Sanematsu, Fumiyuki; Sasazuki, Takehiko; Sasaki, Takehiko; Fukui, Yoshinori

    2006-08-28

    Neutrophils are highly motile leukocytes, and they play important roles in the innate immune response to invading pathogens. Neutrophil chemotaxis requires Rac activation, yet the Rac activators functioning downstream of chemoattractant receptors remain to be determined. We show that DOCK2, which is a mammalian homologue of Caenorhabditis elegans CED-5 and Drosophila melanogaster Myoblast City, regulates motility and polarity during neutrophil chemotaxis. Although DOCK2-deficient neutrophils moved toward the chemoattractant source, they exhibited abnormal migratory behavior with a marked reduction in translocation speed. In DOCK2-deficient neutrophils, chemoattractant-induced activation of both Rac1 and Rac2 were severely impaired, resulting in the loss of polarized accumulation of F-actin and phosphatidylinositol 3,4,5-triphosphate (PIP3) at the leading edge. On the other hand, we found that DOCK2 associates with PIP3 and translocates to the leading edge of chemotaxing neutrophils in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. These results indicate that during neutrophil chemotaxis DOCK2 regulates leading edge formation through PIP3-dependent membrane translocation and Rac activation. PMID:16943182

  5. Tum/RacGAP functions as a switch activating the Pav/kinesin-6 motor.

    PubMed

    Tao, Li; Fasulo, Barbara; Warecki, Brandt; Sullivan, William

    2016-01-01

    Centralspindlin is essential for central spindle and cleavage furrow formation. Drosophila centralspindlin consists of a kinesin-6 motor (Pav/kinesin-6) and a GTPase-activating protein (Tum/RacGAP). Centralspindlin localization to the central spindle is mediated by Pav/kinesin-6. While Tum/RacGAP has well-documented scaffolding functions, whether it influences Pav/kinesin-6 function is less well-explored. Here we demonstrate that both Pav/kinesin-6 and the centralspindlin complex (co-expressed Pav/Tum) have strong microtubule bundling activity. Centralspindlin also has robust plus-end-directed motility. In contrast, Pav/kinesin-6 alone cannot move microtubules. However, the addition of Tum/RacGAP or a 65 amino acid Tum/RacGAP fragment to Pav/kinesin-6 restores microtubule motility. Further, ATPase assays reveal that microtubule-stimulated ATPase activity of centralspindlin is seven times higher than that of Pav/kinesin-6. These findings are supported by in vivo studies demonstrating that in Tum/RacGAP-depleted S2 Drosophila cells, Pav/kinesin-6 exhibits severely reduced localization to the central spindle and an abnormal concentration at the centrosomes. PMID:27091402

  6. Tum/RacGAP functions as a switch activating the Pav/kinesin-6 motor

    PubMed Central

    Tao, Li; Fasulo, Barbara; Warecki, Brandt; Sullivan, William

    2016-01-01

    Centralspindlin is essential for central spindle and cleavage furrow formation. Drosophila centralspindlin consists of a kinesin-6 motor (Pav/kinesin-6) and a GTPase-activating protein (Tum/RacGAP). Centralspindlin localization to the central spindle is mediated by Pav/kinesin-6. While Tum/RacGAP has well-documented scaffolding functions, whether it influences Pav/kinesin-6 function is less well-explored. Here we demonstrate that both Pav/kinesin-6 and the centralspindlin complex (co-expressed Pav/Tum) have strong microtubule bundling activity. Centralspindlin also has robust plus-end-directed motility. In contrast, Pav/kinesin-6 alone cannot move microtubules. However, the addition of Tum/RacGAP or a 65 amino acid Tum/RacGAP fragment to Pav/kinesin-6 restores microtubule motility. Further, ATPase assays reveal that microtubule-stimulated ATPase activity of centralspindlin is seven times higher than that of Pav/kinesin-6. These findings are supported by in vivo studies demonstrating that in Tum/RacGAP-depleted S2 Drosophila cells, Pav/kinesin-6 exhibits severely reduced localization to the central spindle and an abnormal concentration at the centrosomes. PMID:27091402

  7. TIPE1 induces apoptosis by negatively regulating Rac1 activation in hepatocellular carcinoma cells.

    PubMed

    Zhang, Z; Liang, X; Gao, L; Ma, H; Liu, X; Pan, Y; Yan, W; Shan, H; Wang, Z; Chen, Y H; Ma, C

    2015-05-14

    TIPE1 (tumor necrosis factor-α-induced protein 8-like 1 or TNFAIP8L1) is a newly identified member of the TIPE (TNFAIP8) family, which play roles in regulating cell death. However, the biologic functions of TIPE1 in physiologic and pathologic conditions are largely unknown. Here, we report the roles of TIPE1 in hepatocellular carcinoma (HCC). Evaluated by immunohistochemical staining, HCC tissues showed significantly downregulated TIPE1 expression compared with adjacent non-tumor tissues, which positively correlated with tumor pathologic grades and patient survival. Using a homograft tumor model in Balb/c mice, we discovered that TIPE1 significantly diminished the growth and tumor weight of murine liver cancer homografts. Consistently, TIPE1 inhibited both cell growth and colony formation ability of cultured HCC cell lines, which was further identified to be due to TIPE1-inducing apoptosis in a caspase-independent, necrostatin-1 (Nec-1)-insensitive manner. Furthermore, mechanistic investigations revealed that TIPE1 interacted with Rac1, and inhibited the activation of Rac1 and its downstream p65 and c-Jun N-terminal kinase pathway. Moreover, overexpression of constitutively active Rac1 partially rescued the apoptosis induced by TIPE1, and Rac1 knockdown significantly restored the deregulated cell growth induced by TIPE1 small interfering RNA. Our findings revealed that TIPE1 induced apoptosis in HCC cells by negatively regulating Rac1 pathway, and loss of TIPE1 might be a new prognostic indicator for HCC patients. PMID:25043299

  8. Phosphorylation of EBP50 negatively regulates β-PIX-dependent Rac1 activity in anoikis.

    PubMed

    Chen, J-Y; Lin, Y-Y; Jou, T-S

    2012-06-01

    We demonstrated a protein kinase C (PKC)-dependent phosphorylation of canine ezrin/radixin/moesin (ERM)-binding phosphoprotein 50 (EBP50) at serine 347/348 by site-directed mutagenesis and a phospho-specific antibody. Cell fractionation and confocal imaging revealed the relocation of EBP50 from the plasma membrane to cytosol that accompanied this phosphorylation event. Increased phosphorylation at these serine residues led to the dissociation of EBP50 from ezrin and β-PIX, which are two upstream regulators of Rac1 activation. Cells overexpressing an EBP50 mutant, mimicking serine 347/348 phosphorylation, became refractory to hepatocyte growth factor-induced cell spreading and scattering, which is normally mediated by Rac1 activation. Detachment of cells from the substratum also elicited an increase in EBP50 phosphorylation, apparently due to counteracting activities of PKC and protein phosphastase 2A, which resulted in decreased Rac1 activation and induction of anoikis. Cells overexpressing an EBP50 mutant defective in serine 347/348 phosphorylation did not undergo apoptosis in suspension culture. These studies reveal a signaling cascade in which different phosphorylation states and subcellular localization of EBP50 regulate Rac1 function. PMID:22301917

  9. Antiviral activity of a Rac GEF inhibitor characterized with a sensitive HIV/SIV fusion assay

    SciTech Connect

    Pontow, Suzanne; Harmon, Brooke; Campbell, Nancy; Ratner, Lee

    2007-11-10

    A virus-dependent fusion assay was utilized to examine the activity of a panel of HIV-1, -2, and SIV isolates of distinct coreceptor phenotypes. This assay allowed identification of entry inhibitors, and characterization of an antagonist of a Rac guanine nucleotide exchange factor, as an inhibitor of HIV-mediated fusion.

  10. Rac1-Rab11-FIP3 regulatory hub coordinates vesicle traffic with actin remodeling and T-cell activation.

    PubMed

    Bouchet, Jérôme; Del Río-Iñiguez, Iratxe; Lasserre, Rémi; Agüera-Gonzalez, Sonia; Cuche, Céline; Danckaert, Anne; McCaffrey, Mary W; Di Bartolo, Vincenzo; Alcover, Andrés

    2016-06-01

    The immunological synapse generation and function is the result of a T-cell polarization process that depends on the orchestrated action of the actin and microtubule cytoskeleton and of intracellular vesicle traffic. However, how these events are coordinated is ill defined. Since Rab and Rho families of GTPases control intracellular vesicle traffic and cytoskeleton reorganization, respectively, we investigated their possible interplay. We show here that a significant fraction of Rac1 is associated with Rab11-positive recycling endosomes. Moreover, the Rab11 effector FIP3 controls Rac1 intracellular localization and Rac1 targeting to the immunological synapse. FIP3 regulates, in a Rac1-dependent manner, key morphological events, like T-cell spreading and synapse symmetry. Finally, Rab11-/FIP3-mediated regulation is necessary for T-cell activation leading to cytokine production. Therefore, Rac1 endosomal traffic is key to regulate T-cell activation. PMID:27154205

  11. The Transcriptomic Signature of RacA Activation and Inactivation Provides New Insights into the Morphogenetic Network of Aspergillus niger

    PubMed Central

    Kwon, Min Jin; Nitsche, Benjamin M.; Arentshorst, Mark; Jørgensen, Thomas R.; Ram, Arthur F. J.; Meyer, Vera

    2013-01-01

    RacA is the main Rho GTPase in Aspergillus niger regulating polarity maintenance via controlling actin dynamics. Both deletion and dominant activation of RacA (RacG18V) provoke an actin localization defect and thereby loss of polarized tip extension, resulting in frequent dichotomous branching in the ΔracA strain and an apolar growing phenotype for RacG18V. In the current study the transcriptomics and physiological consequences of these morphological changes were investigated and compared with the data of the morphogenetic network model for the dichotomous branching mutant ramosa-1. This integrated approach revealed that polar tip growth is most likely orchestrated by the concerted activities of phospholipid signaling, sphingolipid signaling, TORC2 signaling, calcium signaling and CWI signaling pathways. The transcriptomic signatures and the reconstructed network model for all three morphology mutants (ΔracA, RacG18V, ramosa-1) imply that these pathways become integrated to bring about different physiological adaptations including changes in sterol, zinc and amino acid metabolism and changes in ion transport and protein trafficking. Finally, the fate of exocytotic (SncA) and endocytotic (AbpA, SlaB) markers in the dichotomous branching mutant ΔracA was followed, demonstrating that hyperbranching does not per se result in increased protein secretion. PMID:23894378

  12. Structural details of light activation of the LOV2-based photoswitch PA-Rac1.

    PubMed

    Winkler, Andreas; Barends, Thomas R M; Udvarhelyi, Anikó; Lenherr-Frey, Daniel; Lomb, Lukas; Menzel, Andreas; Schlichting, Ilme

    2015-02-20

    Optical control of cellular processes is an emerging approach for studying biological systems, affording control with high spatial and temporal resolution. Specifically designed artificial photoswitches add an interesting extension to naturally occurring light-regulated functionalities. However, despite a great deal of structural information, the generation of new tools cannot be based fully on rational design yet; in many cases design is limited by our understanding of molecular details of light activation and signal transduction. Our biochemical and biophysical studies on the established optogenetic tool PA-Rac1, the photoactivatable small GTPase Rac1, reveal how unexpected details of the sensor-effector interface, such as metal coordination, significantly affect functionally important structural elements of this photoswitch. Together with solution scattering experiments, our results favor differences in the population of pre-existing conformations as the underlying allosteric activation mechanism of PA-Rac1, rather than the assumed release of the Rac1 domain from the caging photoreceptor domain. These results have implications for the design of new optogenetic tools and highlight the importance of including molecular details of the sensor-effector interface, which is however difficult to assess during the initial design of novel artificial photoswitches. PMID:25368973

  13. Expression and activity of Rac1 is negatively affected in the dehydroepiandrosterone induced polycystic ovary of mouse

    PubMed Central

    2014-01-01

    Background Polycystic ovarian syndrome (PCOS) is characterized by the presence of multiple follicular cysts, giving rise to infertility due to anovulation. This syndrome affects about 10% of women, worldwide. The exact molecular mechanism leading to PCOS remains obscure. RhoGTPase has been associated with oogenesis, but its role in PCOS remains unexplored. Therefore, we attempted to elucidate the Vav-Rac1 signaling in PCOS mice model. Methods We generated a PCOS mice model by injecting dehydroepiandrosterone (DHEA) for a period of 20 days. The expression levels of Rac1, pRac1, Vav, pVav and Caveolin1 were analyzed by employing immuno-blotting and densitometry. The association between Vav and Rac1 proteins were studied by immuno-precipitation. Furthermore, we analyzed the activity of Rac1 and levels of inhibin B and 17β-estradiol in ovary using biochemical assays. Results The presence of multiple follicular cysts in ovary were confirmed by histology. The activity of Rac1 (GTP bound state) was significantly reduced in the PCOS ovary. Similarly, the expression levels of Rac1 and its phosphorylated form (pRac1) were decreased in PCOS in comparison to the sham ovary. The expression level and activity (phosphorylated form) of guanine nucleotide exchanger of Rac1, Vav, was moderately down-regulated. We observed comparatively increased expressions of Caveolin1, 17β-estradiol, and inhibin B in the polycystic ovary. Conclusion We conclude that hyperandrogenization (PCOS) by DHEA diminishes ovarian Rac1 and Vav expression and activity along with an increase in expression of Caveolin1. This is accompanied by an increase in the intra-ovarian level of '17 β-estradiol and inhibin B. PMID:24628852

  14. Rac-1 and Raf-1 kinases, components of distinct signaling pathways, activate myotonic dystrophy protein kinase

    NASA Technical Reports Server (NTRS)

    Shimizu, M.; Wang, W.; Walch, E. T.; Dunne, P. W.; Epstein, H. F.

    2000-01-01

    Myotonic dystrophy protein kinase (DMPK) is a serine-threonine protein kinase encoded by the myotonic dystrophy (DM) locus on human chromosome 19q13.3. It is a close relative of other kinases that interact with members of the Rho family of small GTPases. We show here that the actin cytoskeleton-linked GTPase Rac-1 binds to DMPK, and coexpression of Rac-1 and DMPK activates its transphosphorylation activity in a GTP-sensitive manner. DMPK can also bind Raf-1 kinase, the Ras-activated molecule of the MAP kinase pathway. Purified Raf-1 kinase phosphorylates and activates DMPK. The interaction of DMPK with these distinct signals suggests that it may play a role as a nexus for cross-talk between their respective pathways and may partially explain the remarkable pleiotropy of DM.

  15. Geometry sensing through POR1 regulates Rac1 activity controlling early osteoblast differentiation in response to nanofiber diameter.

    PubMed

    Higgins, A M; Banik, B L; Brown, J L

    2015-02-01

    Bone grafting procedures in the United States rely heavily upon autografts and allografts, which are donor-dependent, cause donor site pain, and can transmit disease. Synthetic bone grafts can reduce these risks; however, synthetics lack the bone differentiating (osteoinductive) abilities of auto- and allografts. Achieving innate osteoinductive properties of synthetics through surface modifications is currently under investigation. This study focuses on nanofibers, with emphasis on how fiber diameter and the potential curvature sensor POR1 affect the activation of the signaling molecules Rac1 and Arf1, and leading to expression of alkaline phosphatase (ALP), an osteoinductive marker. Diameters of 0.1, 0.3, and 1.0 μm were compared against a flat control. The highest level of Rac1 activation was achieved on the smallest fibers (0.1 μm), a trend that was lost in POR1 knockdowns. This supports the hypothesis that on small nanofibers, POR1 favorably binds to highly curved cell membranes, which allows Rac1 to subsequently dissociate and activate. When the curvature is insufficient to bind POR1, POR1 binds to inactive Rac1 and competitively inhibits its activation. Arf1 activation followed an opposite trend, with the largest nanofibers exhibiting the highest activity. This trend reinforces the known interaction between Rac1 and Arf1 through the GIT-PIX complex, an Arf1 GAP and Rac1 GEF, respectively. Large, (1.0 μm), nanofibers demonstrated the highest ALP activity, indicating that ALP expression is inversely dependent on Rac1 activation. Knockdown of POR1 resulted in increased ALP activity across the substrates but without regard to the curvature sensing trend seen previously. Thus, POR1 senses curvature and increases Rac1 activity, which negatively regulates bone differentiation. PMID:25539497

  16. Plexin-B2 negatively regulates macrophage motility, Rac, and Cdc42 activation.

    PubMed

    Roney, Kelly E; O'Connor, Brian P; Wen, Haitao; Holl, Eda K; Guthrie, Elizabeth H; Davis, Beckley K; Jones, Stephen W; Jha, Sushmita; Sharek, Lisa; Garcia-Mata, Rafael; Bear, James E; Ting, Jenny P-Y

    2011-01-01

    Plexins are cell surface receptors widely studied in the nervous system, where they mediate migration and morphogenesis though the Rho family of small GTPases. More recently, plexins have been implicated in immune processes including cell-cell interaction, immune activation, migration, and cytokine production. Plexin-B2 facilitates ligand induced cell guidance and migration in the nervous system, and induces cytoskeletal changes in overexpression assays through RhoGTPase. The function of Plexin-B2 in the immune system is unknown. This report shows that Plexin-B2 is highly expressed on cells of the innate immune system in the mouse, including macrophages, conventional dendritic cells, and plasmacytoid dendritic cells. However, Plexin-B2 does not appear to regulate the production of proinflammatory cytokines, phagocytosis of a variety of targets, or directional migration towards chemoattractants or extracellular matrix in mouse macrophages. Instead, Plxnb2(-/-) macrophages have greater cellular motility than wild type in the unstimulated state that is accompanied by more active, GTP-bound Rac and Cdc42. Additionally, Plxnb2(-/-) macrophages demonstrate faster in vitro wound closure activity. Studies have shown that a closely related family member, Plexin-B1, binds to active Rac and sequesters it from downstream signaling. The interaction of Plexin-B2 with Rac has only been previously confirmed in yeast and bacterial overexpression assays. The data presented here show that Plexin-B2 functions in mouse macrophages as a negative regulator of the GTPases Rac and Cdc42 and as a negative regulator of basal cell motility and wound healing. PMID:21966369

  17. Rab5 is required in metastatic cancer cells for Caveolin-1-enhanced Rac1 activation, migration and invasion.

    PubMed

    Díaz, Jorge; Mendoza, Pablo; Ortiz, Rina; Díaz, Natalia; Leyton, Lisette; Stupack, Dwayne; Quest, Andrew F G; Torres, Vicente A

    2014-06-01

    Rab5 is a small GTPase that regulates early endosome trafficking and other cellular processes, including cell adhesion and migration. Specifically, Rab5 promotes Rac1 activation and cancer cell migration, but little is known about the upstream regulators of Rab5. We have previously shown that the scaffolding protein Caveolin-1 (CAV1) promotes Rac1 activation and migration of cancer cells. Here, we hypothesized that CAV1 stimulates Rab5 activation, leading to increased Rac1 activity and cell migration. Expression of CAV1 in B16-F10 mouse melanoma and HT-29(US) human colon adenocarcinoma cells increased the GTP loading of Rab5, whereas shRNA-mediated targeting of endogenous CAV1 in MDA-MB-231 breast cancer cells decreased Rab5-GTP levels. Accordingly, shRNA-mediated downregulation of Rab5 decreased CAV1-mediated Rac1 activation, cell migration and invasion in B16-F10 and HT-29(US) cells. Expression of CAV1 was accompanied by increased recruitment of Tiam1, a Rac1 guanine nucleotide exchange factor (GEF), to Rab5-positive early endosomes. Using the inhibitor NSC23766, Tiam1 was shown to be required for Rac1 activation and cell migration induced by CAV1 and Rab5. Mechanistically, we provide evidence implicating p85α (also known as PIK3R1), a Rab5 GTPase-activating protein (GAP), in CAV1-dependent effects, by showing that CAV1 recruits p85α, precluding p85α-mediated Rab5 inactivation and increasing cell migration. In summary, these studies identify a novel CAV1-Rab5-Rac1 signaling axis, whereby CAV1 prevents Rab5 inactivation, leading to increased Rac1 activity and enhanced tumor cell migration and invasion. PMID:24659799

  18. Novel Activities of Select NSAID R-Enantiomers against Rac1 and Cdc42 GTPases.

    PubMed

    Oprea, Tudor I; Sklar, Larry A; Agola, Jacob O; Guo, Yuna; Silberberg, Melina; Roxby, Joshua; Vestling, Anna; Romero, Elsa; Surviladze, Zurab; Murray-Krezan, Cristina; Waller, Anna; Ursu, Oleg; Hudson, Laurie G; Wandinger-Ness, Angela

    2015-01-01

    Rho family GTPases (including Rac, Rho and Cdc42) collectively control cell proliferation, adhesion and migration and are of interest as functional therapeutic targets in numerous epithelial cancers. Based on high throughput screening of the Prestwick Chemical Library® and cheminformatics we identified the R-enantiomers of two approved drugs (naproxen and ketorolac) as inhibitors of Rac1 and Cdc42. The corresponding S-enantiomers are considered the active component in racemic drug formulations, acting as non-steroidal anti-inflammatory drugs (NSAIDs) with selective activity against cyclooxygenases. Here, we show that the S-enantiomers of naproxen and ketorolac are inactive against the GTPases. Additionally, more than twenty other NSAIDs lacked inhibitory action against the GTPases, establishing the selectivity of the two identified NSAIDs. R-naproxen was first identified as a lead compound and tested in parallel with its S-enantiomer and the non-chiral 6-methoxy-naphthalene acetic acid (active metabolite of nabumetone, another NSAID) as a structural series. Cheminformatics-based substructure analyses-using the rotationally constrained carboxylate in R-naproxen-led to identification of racemic [R/S] ketorolac as a suitable FDA-approved candidate. Cell based measurement of GTPase activity (in animal and human cell lines) demonstrated that the R-enantiomers specifically inhibit epidermal growth factor stimulated Rac1 and Cdc42 activation. The GTPase inhibitory effects of the R-enantiomers in cells largely mimic those of established Rac1 (NSC23766) and Cdc42 (CID2950007/ML141) specific inhibitors. Docking predicts that rotational constraints position the carboxylate moieties of the R-enantiomers to preferentially coordinate the magnesium ion, thereby destabilizing nucleotide binding to Rac1 and Cdc42. The S-enantiomers can be docked but are less favorably positioned in proximity to the magnesium. R-naproxen and R-ketorolac have potential for rapid translation and

  19. Novel Activities of Select NSAID R-Enantiomers against Rac1 and Cdc42 GTPases

    PubMed Central

    Oprea, Tudor I.; Sklar, Larry A.; Agola, Jacob O.; Guo, Yuna; Silberberg, Melina; Roxby, Joshua; Vestling, Anna; Romero, Elsa; Surviladze, Zurab; Murray-Krezan, Cristina; Waller, Anna; Ursu, Oleg; Hudson, Laurie G.; Wandinger-Ness, Angela

    2015-01-01

    Rho family GTPases (including Rac, Rho and Cdc42) collectively control cell proliferation, adhesion and migration and are of interest as functional therapeutic targets in numerous epithelial cancers. Based on high throughput screening of the Prestwick Chemical Library® and cheminformatics we identified the R-enantiomers of two approved drugs (naproxen and ketorolac) as inhibitors of Rac1 and Cdc42. The corresponding S-enantiomers are considered the active component in racemic drug formulations, acting as non-steroidal anti-inflammatory drugs (NSAIDs) with selective activity against cyclooxygenases. Here, we show that the S-enantiomers of naproxen and ketorolac are inactive against the GTPases. Additionally, more than twenty other NSAIDs lacked inhibitory action against the GTPases, establishing the selectivity of the two identified NSAIDs. R-naproxen was first identified as a lead compound and tested in parallel with its S-enantiomer and the non-chiral 6-methoxy-naphthalene acetic acid (active metabolite of nabumetone, another NSAID) as a structural series. Cheminformatics-based substructure analyses—using the rotationally constrained carboxylate in R-naproxen—led to identification of racemic [R/S] ketorolac as a suitable FDA-approved candidate. Cell based measurement of GTPase activity (in animal and human cell lines) demonstrated that the R-enantiomers specifically inhibit epidermal growth factor stimulated Rac1 and Cdc42 activation. The GTPase inhibitory effects of the R-enantiomers in cells largely mimic those of established Rac1 (NSC23766) and Cdc42 (CID2950007/ML141) specific inhibitors. Docking predicts that rotational constraints position the carboxylate moieties of the R-enantiomers to preferentially coordinate the magnesium ion, thereby destabilizing nucleotide binding to Rac1 and Cdc42. The S-enantiomers can be docked but are less favorably positioned in proximity to the magnesium. R-naproxen and R-ketorolac have potential for rapid translation and

  20. The role of Rac1 in the regulation of NF-kB activity, cell proliferation, and cell migration in non-small cell lung carcinoma

    PubMed Central

    Gastonguay, Adam; Berg, Tracy; Hauser, Andrew D.; Schuld, Nathan; Lorimer, Ellen; Williams, Carol L.

    2012-01-01

    The small GTPase Rac1 regulates many cellular processes, including cytoskeletal reorganization, cell migration, proliferation, and survival. Additionally, Rac1 plays a major role in activating NF-κB-mediated transcription. Both Rac1 and NF-κB regulate many properties of the malignant phenotype, including anchorage-independent proliferation and survival, metastasis, and angiogenesis. Despite these findings, the roles of Rac1and NF-κB in non-small cell lung carcinoma, a leading cause of cancer deaths, have not been thoroughly investigated. Here, we compared the effects of Rac1 siRNA to that of the Rac1 inhibitor NSC23766 on multiple features of the NSCLC malignant phenotype, including NF-κB activity. We show that the siRNA-mediated silencing of Rac1 in lung cancer cells results in decreased cell proliferation and migration. The decrease in proliferation was observed in both anchorage-dependent and anchorage-independent assays. Furthermore, cells with decreased Rac1 expression have a slowed progression through the G1 phase of the cell cycle. These effects induced by Rac1 siRNA correlated with a decrease in NF-κB transcriptional activity. Additionally, inhibition of NF-κB signaling with BAY 11–7082 inhibited proliferation; indicating that the loss of cell proliferation and migration induced by the silencing of Rac1 expression may be attributed in part to loss of NF-κB activity. Interestingly, treatment with the Rac1 inhibitor NSC23766 strongly inhibits cell proliferation, cell cycle progression, and NF-κB activity in lung cancer cells, to an even greater extent than the inhibition induced by Rac1 siRNA. These findings indicate that Rac1 plays an important role in lung cancer cell proliferation and migration, most likely through its ability to promote NF-κB activity, and highlight Rac1 pathways as therapeutic targets for the treatment of lung cancer. PMID:22549160

  1. IbeA and OmpA of Escherichia coli K1 exploit Rac1 activation for invasion of human brain microvascular endothelial cells.

    PubMed

    Maruvada, Ravi; Kim, Kwang Sik

    2012-06-01

    Meningitis-causing Escherichia coli K1 internalization of the blood-brain barrier is required for penetration into the brain, but the host-microbial interactions involved in E. coli entry of the blood-brain barrier remain incompletely understood. We show here that a meningitis-causing E. coli K1 strain RS218 activates Rac1 (GTP-Rac1) of human brain microvascular endothelial cells (HBMEC) in a time-dependent manner. Both activation and bacterial invasion were significantly inhibited in the presence of a Rac1 inhibitor. We further showed that the guanine nucleotide exchange factor Vav2, not β-Pix, was involved in E. coli K1-mediated Rac1 activation. Since activated STAT3 is known to bind GTP-Rac1, the relationship between STAT3 and Rac1 was examined in E. coli K1 invasion of HBMEC. Downregulation of STAT3 resulted in significantly decreased E. coli invasion compared to control HBMEC, as well as a corresponding decrease in GTP-Rac1, suggesting that Rac1 activation in response to E. coli is under the control of STAT3. More importantly, two E. coli determinants contributing to HBMEC invasion, IbeA and OmpA, were shown to affect both Rac1 activation and their association with STAT3. These findings demonstrate for the first time that specific E. coli determinants regulate a novel mechanism of STAT3 cross talk with Rac1 in E. coli K1 invasion of HBMEC. PMID:22451524

  2. [RAC3 nuclear receptor co-activator has a protective role in the apoptosis induced by different stimuli].

    PubMed

    Coló, Georgina P; Rubio, María F; Alvarado, Cecilia V; Costas, Mónica A

    2007-01-01

    RAC3 belongs to the family of p160 nuclear receptors coactivators and it is over-expressed in several tumors. We have previously shown that RAC3 is a NF-kappaB coactivator. In this paper, we investigated the role of RAC3 in cell-sensitivity to apoptosis, using H2O2 in the human embryonic kidney cell line (HEK293), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) in a human chronic myeloid leukemia cell line (K562) naturally resistant to TRAIL. We observed that the tumoral K562 cells have high levels of RAC3 if compared with the non-tumoral HEK293 cells. The normal or transfected coactivator over-expression inhibits apoptosis through a diminished caspase activity and AIF nuclear translocation, increased NF-kappaB, AKT and p38, and decreased ERK activities. In contrast, inhibition of RAC3 by siRNA induced sensitivity of K562 to TRAIL-induced apoptosis. Such results suggest that over-expression of RAC3 contributes to tumor development through molecular mechanisms that do not depend strictly on acetylation and/or steroid hormones, which control cell death. This could be a possible target for future tumor therapies. PMID:18051230

  3. ELMO1 Directly Interacts with Gβγ Subunit to Transduce GPCR Signaling to Rac1 Activation in Chemotaxis

    PubMed Central

    Wang, Youhong; Xu, Xuehua; Pan, Miao; Jin, Tian

    2016-01-01

    Diverse chemokines bind to G protein-coupled receptors (GPCRs) to activate the small GTPase Rac to regulate F-actin dynamics during chemotaxis. ELMO and Dock proteins form complexes that function as guanine nucleotide exchange factors (GEFs) for Rac activation. However, the linkage between GPCR activation and the ELMO/Dock-mediated Rac activation is not fully understood. In the present study, we show that chemoattractants induce dynamic membrane translocation of ELMO1 in mammalian cells. ELMO1 plays an important role in GPCR-mediated chemotaxis. We also reveal that ELMO1 and Dock1 form a stable complex. Importantly, activation of chemokine GPCR promotes the interaction between ELMO1 and Gβγ. The ELMO1-Gβγ interaction is through the N-terminus of ELMO1 protein and is important for the membrane translocation of ELMO1. ELMO1 is required for Rac1 activation upon chemoattractant stimulation. Our results suggest that chemokine GPCR-mediated interaction between Gβγ and ELMO1/Dock1 complex might serve as an evolutionarily conserved mechanism for Rac activation to regulate actin cytoskeleton for chemotaxis of human cells. PMID:27313788

  4. GIT1 promotes lung cancer cell metastasis through modulating Rac1/Cdc42 activity and is associated with poor prognosis.

    PubMed

    Chang, Jeng-Shou; Su, Chia-Yi; Yu, Wen-Hsuan; Lee, Wei-Jiunn; Liu, Yu-Peng; Lai, Tsung-Ching; Jan, Yi-Hua; Yang, Yi-Fang; Shen, Chia-Ning; Shew, Jin-Yuh; Lu, Jean; Yang, Chih-Jen; Huang, Ming-Shyan; Lu, Pei-Jung; Lin, Yuan-Feng; Kuo, Min-Liang; Hua, Kuo-Tai; Hsiao, Michael

    2015-11-01

    G-protein-coupled receptor kinase interacting protein 1 (GIT1) is participated in cell movement activation, which is a fundamental process during tissue development and cancer progression. GIT1/PIX forming a functional protein complex that contributes to Rac1/Cdc42 activation, resulting in increasing cell mobility. Although the importance of Rac1/Cdc42 activation is well documented in cancer aggressiveness, the clinical importance of GIT1 remains largely unknown. Here, we investigated the clinical significance of GIT1 expression in non-small-cell lung cancer (NSCLC) and also verified the importance of GIT1-Rac1/Cdc42 axis in stimulating NSCLC cell mobility. The result indicated higher GIT1 expression patients had significantly poorer prognoses in disease-free survival (DFS) and overall survival (OS) compared with lower GIT1 expression patients. Higher GIT1 expression was an independent prognostic factor by multivariate analysis and associated with migration/invasion of NSCLC cells in transwell assay. In vivo studies indicated that GIT1 promotes metastasis of NSCLC cells. Finally, GIT1 was found to stimulate migration/invasion by altering the activity of Rac1/Cdc42 in NSCLC cells. Together, the GIT1 expression is associated with poor prognosis in patients with NSCLC. GIT1 is critical for the invasiveness of NSCLC cells through stimulating the activity of Rac1/Cdc42. PMID:26462147

  5. GIT1 promotes lung cancer cell metastasis through modulating Rac1/Cdc42 activity and is associated with poor prognosis

    PubMed Central

    Chang, Jeng-Shou; Su, Chia-Yi; Yu, Wen-Hsuan; Lee, Wei-Jiunn; Liu, Yu-Peng; Lai, Tsung-Ching; Jan, Yi-Hua; Yang, Yi-Fang; Shen, Chia-Ning; Shew, Jin-Yuh; Lu, Jean; Yang, Chih-Jen; Huang, Ming-Shyan; Lu, Pei-Jung; Lin, Yuan-Feng; Kuo, Min-Liang; Hua, Kuo-Tai; Hsiao, Michael

    2015-01-01

    G-protein-coupled receptor kinase interacting protein 1 (GIT1) is participated in cell movement activation, which is a fundamental process during tissue development and cancer progression. GIT1/PIX forming a functional protein complex that contributes to Rac1/Cdc42 activation, resulting in increasing cell mobility. Although the importance of Rac1/Cdc42 activation is well documented in cancer aggressiveness, the clinical importance of GIT1 remains largely unknown. Here, we investigated the clinical significance of GIT1 expression in non-small-cell lung cancer (NSCLC) and also verified the importance of GIT1-Rac1/Cdc42 axis in stimulating NSCLC cell mobility. The result indicated higher GIT1 expression patients had significantly poorer prognoses in disease-free survival (DFS) and overall survival (OS) compared with lower GIT1 expression patients. Higher GIT1 expression was an independent prognostic factor by multivariate analysis and associated with migration/invasion of NSCLC cells in transwell assay. In vivo studies indicated that GIT1 promotes metastasis of NSCLC cells. Finally, GIT1 was found to stimulate migration/invasion by altering the activity of Rac1/Cdc42 in NSCLC cells. Together, the GIT1 expression is associated with poor prognosis in patients with NSCLC. GIT1 is critical for the invasiveness of NSCLC cells through stimulating the activity of Rac1/Cdc42. PMID:26462147

  6. Dynamic Assessment of Fibroblast Mechanical Activity during Rac-induced Cell Spreading in 3-D Culture

    PubMed Central

    Petroll, W. Matthew; Ma, Lisha; Kim, Areum; Ly, Linda; Vishwanath, Mridula

    2009-01-01

    The goal of this study was to determine the morphological and sub-cellular mechanical effects of Rac activation on fibroblasts within 3-D collagen matrices. Corneal fibroblasts were plated at low density inside 100 μm thick fibrillar collagen matrices and cultured for 1 to 2 days in serum-free media. Time-lapse imaging was then performed using Nomarski DIC. After an acclimation period, perfusion was switched to media containing PDGF. In some experiments, Y-27632 or blebbistatin were used to inhibit Rho-kinase (ROCK) or myosin II, respectively. PDGF activated Rac and induced cell spreading, which resulted in an increase in cell length, cell area, and the number of pseudopodial processes. Tractional forces were generated by extending pseudopodia, as indicated by centripetal displacement and realignment of collagen fibrils. Interestingly, the pattern of pseudopodial extension and local collagen fibril realignment was highly dependent upon the initial orientation of fibrils at the leading edge. Following ROCK or myosin II inhibition, significant ECM relaxation was observed, but small displacements of collagen fibrils continued to be detected at the tips of pseudopodia. Taken together, the data suggests that during Rac-induced cell spreading within 3-D matrices, there is a shift in the distribution of forces from the center to the periphery of corneal fibroblasts. ROCK mediates the generation of large myosin II-based tractional forces during cell spreading within 3-D collagen matrices, however residual forces can be generated at the tips of extending pseudopodia that are both ROCK and myosin II-independent. PMID:18452153

  7. Cellular inhibitor of apoptosis protein 2 controls human colonic epithelial restitution, migration, and Rac1 activation.

    PubMed

    Seidelin, Jakob Benedict; Larsen, Sylvester; Linnemann, Dorte; Vainer, Ben; Coskun, Mehmet; Troelsen, Jesper Thorvald; Nielsen, Ole Haagen

    2015-01-15

    Identification of pathways involved in wound healing is important for understanding the pathogenesis of various intestinal diseases. Cellular inhibitor of apoptosis protein 2 (cIAP2) regulates proliferation and migration in nonepithelial cells and is expressed in human colonocytes. The aim of the study was to investigate the role of cIAP2 for wound healing in the normal human colon. Wound tissue was generated by taking rectosigmoidal biopsies across an experimental ulcer in healthy subjects after 5, 24, and 48 h. In experimental ulcers, the expression of cIAP2 in regenerating intestinal epithelial cells (IECs) was increased at the wound edge after 24 h (P < 0.05), returned to normal after reepithelialization, and correlated with the inflammatory reaction in the experimental wounds (P < 0.001). cIAP2 was induced in vitro in regenerating Caco2 IECs after wound infliction (P < 0.01). Knockdown of cIAP2 caused a substantial impairment of the IEC regeneration through inhibition of migration (P < 0.005). cIAP2 overexpression lead to formation of migrating IECs and upregulation of expression of RhoA and Rac1 as well as GTP-activation of Rac1. Transforming growth factor-β1 enhanced the expression of cIAP2 but was not upregulated in wounds in vivo and in vitro. NF-κB and MAPK pathways did not affect cIAP2 expression. cIAP2 is in conclusion a regulator of human intestinal wound healing through enhanced migration along with activation of Rac1, and the findings suggest that cIAP2 could be a future therapeutic target to improve intestinal wound healing. PMID:25394657

  8. Abr and Bcr, Two Homologous Rac GTPase-Activating Proteins, Control Multiple Cellular Functions of Murine Macrophages▿ †

    PubMed Central

    Cho, Young Jin; Cunnick, Jess M.; Yi, Sun-Ju; Kaartinen, Vesa; Groffen, John; Heisterkamp, Nora

    2007-01-01

    Small GTPases of the Rho family are key regulators of phagocytic leukocyte function. Abr and Bcr are homologous, multidomain proteins. Their C-terminal domain has GTPase-activating protein (GAP) activity that, in vitro, is specific for Rac and Cdc42. To address the in vivo relevance of these entire proteins, of which little is known, the current study examined the effect of the genetic ablation of Abr and Bcr in murine macrophages. The concomitant loss of Abr and Bcr induced multiple alterations of macrophage cellular behavior known to be under the control of Rac. Macrophages lacking both Abr and Bcr exhibited an atypical, elongated morphology that was reproduced by the ectopic expression of GAP domain mutant Abr and Bcr in a macrophage cell line and of constitutively active Rac in primary macrophages. A robust increase in colony-stimulating factor 1 (CSF-1)-directed motility was observed in macrophages deficient for both proteins and, in response to CSF-1 stimulation, Abr and Bcr transiently translocated to the plasma membrane. Phagocytosis of opsonized particles was also increased in macrophages lacking both proteins and correlated with sustained Rac activation. Bcr and Abr GAP mutant proteins localized around phagosomes and induced distinct phagocytic cup formation. These results identify Abr and Bcr as the only GAPs to date that specifically negatively regulate Rac function in vivo in primary macrophages. PMID:17116687

  9. CCK activates RhoA and Rac1 differentially through Gα13 and Gαq in mouse pancreatic acini

    PubMed Central

    Bi, Yan; Ji, Baoan; Ernst, Stephen A.; Williams, John A.

    2010-01-01

    Cholecystokinin (CCK) has been shown to activate RhoA and Rac1, as well as reorganize the actin cytoskeleton and, thereby, modify acinar morphology and amylase secretion in mouse pancreatic acini. The aim of the present study was to determine which heterotrimeric G proteins activate RhoA and Rac1 upon CCK stimulation. Gα13, but not Gα12, was identified in mouse pancreatic acini by RT-PCR and Western blotting. Using specific assays for RhoA and Rac1 activation, we showed that only active Gα13 activated RhoA. By contrast, active Gα13 and Gαq, but not Gαs, slightly increased GTP-bound Rac1 levels. A greater increase in Rac1 activation was observed when active Gα13 and active Gαq were coexpressed. Gαi was not required for CCK-induced RhoA or Rac1 activation. The regulator of G protein signaling (RGS) domain of p115-Rho guanine nucleotide exchange factor (p115-RGS), a specific inhibitor of Gα12/13-mediated signaling, abolished CCK-stimulated RhoA activation. By contrast, both RGS-2, an inhibitor of Gαq, and p115-RGS abolished CCK-induced Rac1 activation, which was PLC pathway-independent. Active Gαq and Gα13, but not Gαs, induced morphological changes and actin redistribution similar to 1 nM CCK. CCK-induced actin cytoskeletal reorganization was inhibited by RGS-2, but not by p115-RGS, whereas CCK-induced amylase secretion was blocked by both inhibitors. Together, these findings indicate that, in mouse pancreatic acini, Gα13 links CCK stimulation to the activation of RhoA, whereas both Gα13 and Gαq link CCK stimulation to the activation of Rac1. CCK-induced actin cytoskeletal reorganization is mainly mediated by Gαq. By contrast, Gα13 and Gαq signaling are required for CCK-induced amylase secretion. PMID:19940064

  10. Smooth Muscle-Alpha Actin Inhibits Vascular Smooth Muscle Cell Proliferation and Migration by Inhibiting Rac1 Activity

    PubMed Central

    Chen, Lihua; DeWispelaere, Allison; Dastvan, Frank; Osborne, William R. A.; Blechner, Christine; Windhorst, Sabine; Daum, Guenter

    2016-01-01

    Smooth muscle alpha-actin (SMA) is a marker for the contractile, non-proliferative phenotype of adult smooth muscle cells (SMCs). Upon arterial injury, expression of SMA and other structural proteins decreases and SMCs acquire a pro-migratory and proliferative phenotype. To what extent SMA regulates migration and proliferation of SMCs is unclear and putative signaling pathways involved remain to be elucidated. Here, we used lentiviral-mediated gene transfer and siRNA technology to manipulate expression of SMA in carotid mouse SMCs and studied effects of SMA. Overexpression of SMA results in decreased proliferation and migration and blunts serum-induced activation of the small GTPase Rac, but not RhoA. All inhibitory effects of SMA are rescued by expression of a constitutively active Rac1 mutant (V12rac1). Moreover, reduction of SMA expression by siRNA technology results in an increased activation of Rac. Taken together, this study identifies Rac1 as a downstream target for SMA to inhibit SMC proliferation and migration. PMID:27176050

  11. Rapidly rendering cells phagocytic through a cell surface display technique and concurrent Rac activation.

    PubMed

    Onuma, Hiroki; Komatsu, Toru; Arita, Makoto; Hanaoka, Kenjiro; Ueno, Tasuku; Terai, Takuya; Nagano, Tetsuo; Inoue, Takanari

    2014-07-15

    Cell surfaces represent a platform through which extracellular signals that determine diverse cellular processes, including migration, division, adhesion, and phagocytosis, are transduced. Techniques to rapidly reconfigure the surface properties of living cells should thus offer the ability to harness these cellular functions. Although the molecular mechanism of phagocytosis is well characterized, the minimal molecular players that are sufficient to activate this elaborate process remain elusive. We developed and implemented a technique to present a molecule of interest at the cell surface in an inducible manner on a time scale of minutes. We simultaneously induced the cell surface display of the C2 domain of milk fat globule epidermal growth factor factor 8 (MFG-E8) and activated the intracellular small guanosine triphosphatase Rac, which stimulates actin polymerization at the cell periphery. The C2 domain binds to phosphatidylserine, a lipid exposed on the surface of apoptotic cells. By integrating the stimulation of these two processes, we converted HeLa cells into a phagocytic cell line that bound to and engulfed apoptotic human Jurkat cells. Inducing either the cell surface display of the C2 domain or activating Rac alone was not sufficient to stimulate phagocytosis, which suggests that attachment to the target cell and actin reorganization together constitute the minimal molecular events that are needed to induce phagocytosis. This cell surface display technique might be useful as part of a targeted, cell-based therapy in which unwanted cells with characteristic surface molecules could be rapidly consumed by engineered cells. PMID:25028719

  12. Rapidly rendering cells phagocytic through a cell-surface display technique and concurrent Rac activation

    PubMed Central

    Onuma, Hiroki; Arita, Makoto; Hanaoka, Kenjiro; Ueno, Tasuku; Terai, Takuya; Nagano, Tetsuo

    2014-01-01

    Cell surfaces represent a platform through which extracellular signals that determine diverse cellular processes, including migration, division, adhesion, and phagocytosis, are transduced. Techniques to rapidly reconfigure the surface properties of living cells should thus offer the ability to harness these cellular functions. Although the molecular mechanism of phagocytosis is well-characterized, the minimal molecular players that are sufficient to activate this elaborate process remain elusive. We developed and implemented a technique to present a molecule of interest at the cell surface in an inducible manner on a timescale of minutes. We simultaneously induced the cell-surface display of the C2 domain of milk fat globule-EGF factor 8 (MFG-E8) and activated the intracellular small guanosine triphosphatase Rac, which stimulates actin polymerization at the cell periphery. The C2 domain binds to phosphatidylserine, a lipid exposed on the surface of apoptotic cells. By integrating the stimulation of these two processes, we converted HeLa cells into a phagocytic cell line that bound to and engulfed apoptotic human Jurkat cells. Inducing either the cell-surface display of the C2 domain or activating Rac alone was not sufficient to stimulate phagocytosis, which suggests that attachment to the target cell and actin reorganization together constitute the minimal molecular events that are needed to induce phagocytosis. This cell-surface display technique might be useful as part of a targeted, cell-based therapy in which unwanted cells with characteristic surface molecules could be rapidly consumed by engineered cells. PMID:25028719

  13. Axl Phosphorylates Elmo Scaffold Proteins To Promote Rac Activation and Cell Invasion

    PubMed Central

    Abu-Thuraia, Afnan; Gauthier, Rosemarie; Chidiac, Rony; Fukui, Yoshinori; Screaton, Robert A.; Gratton, Jean-Philippe

    2014-01-01

    The receptor tyrosine kinase Axl contributes to cell migration and invasion. Expression of Axl correlates with metastatic progression in cancer patients, yet the specific signaling events promoting invasion downstream of Axl are poorly defined. Herein, we report Elmo scaffolds to be direct substrates and binding partners of Axl. Elmo proteins are established to interact with Dock family guanine nucleotide exchange factors to control Rac-mediated cytoskeletal dynamics. Proteomics and mutagenesis studies reveal that Axl phosphorylates Elmo1/2 on a conserved carboxyl-terminal tyrosine residue. Upon Gas6-dependent activation of Axl, endogenous Elmo2 becomes phosphorylated on Tyr-713 and enters into a physical complex with Axl in breast cancer cells. Interfering with Elmo2 expression prevented Gas6-induced Rac1 activation in breast cancer cells. Similarly to blocking of Axl, Elmo2 knockdown or pharmacological inhibition of Dock1 abolishes breast cancer cell invasion. Interestingly, Axl or Elmo2 knockdown diminishes breast cancer cell proliferation. Rescue of Elmo2 knockdown cells with the wild-type protein but not with Elmo2 harboring Tyr-713-Phe mutations restores cell invasion and cell proliferation. These results define a new mechanism by which Axl promotes cell proliferation and invasion and identifies inhibition of the Elmo-Dock pathway as a potential therapeutic target to stop Axl-induced metastases. PMID:25332238

  14. Axl phosphorylates Elmo scaffold proteins to promote Rac activation and cell invasion.

    PubMed

    Abu-Thuraia, Afnan; Gauthier, Rosemarie; Chidiac, Rony; Fukui, Yoshinori; Screaton, Robert A; Gratton, Jean-Philippe; Côté, Jean-François

    2015-01-01

    The receptor tyrosine kinase Axl contributes to cell migration and invasion. Expression of Axl correlates with metastatic progression in cancer patients, yet the specific signaling events promoting invasion downstream of Axl are poorly defined. Herein, we report Elmo scaffolds to be direct substrates and binding partners of Axl. Elmo proteins are established to interact with Dock family guanine nucleotide exchange factors to control Rac-mediated cytoskeletal dynamics. Proteomics and mutagenesis studies reveal that Axl phosphorylates Elmo1/2 on a conserved carboxyl-terminal tyrosine residue. Upon Gas6-dependent activation of Axl, endogenous Elmo2 becomes phosphorylated on Tyr-713 and enters into a physical complex with Axl in breast cancer cells. Interfering with Elmo2 expression prevented Gas6-induced Rac1 activation in breast cancer cells. Similarly to blocking of Axl, Elmo2 knockdown or pharmacological inhibition of Dock1 abolishes breast cancer cell invasion. Interestingly, Axl or Elmo2 knockdown diminishes breast cancer cell proliferation. Rescue of Elmo2 knockdown cells with the wild-type protein but not with Elmo2 harboring Tyr-713-Phe mutations restores cell invasion and cell proliferation. These results define a new mechanism by which Axl promotes cell proliferation and invasion and identifies inhibition of the Elmo-Dock pathway as a potential therapeutic target to stop Axl-induced metastases. PMID:25332238

  15. Actin depolymerization mediated loss of SNTA1 phosphorylation and Rac1 activity has implications on ROS production, cell migration and apoptosis.

    PubMed

    Bhat, Sehar Saleem; Parray, Arif Ali; Mushtaq, Umar; Fazili, Khalid Majid; Khanday, Firdous Ahmad

    2016-06-01

    Alpha-1-syntrophin (SNTA1) and Rac1 are part of a signaling pathway via the dystrophin glycoprotein complex (DGC). Both SNTA1 and Rac1 proteins are over-expressed in various carcinomas. It is through the DGC signaling pathway that SNTA1 has been shown to act as a link between the extra cellular matrix, the internal cell signaling apparatus and the actin cytoskeleton. SNTA1 is involved in the modulation of the actin cytoskeleton and actin reorganization. Rac1 also controls actin cytoskeletal organization in the cell. In this study, we present the interplay between f-actin, SNTA1 and Rac1. We analyzed the effect of actin depolymerization on SNTA1 tyrosine phosphorylation and Rac1 activity using actin depolymerizing drugs, cytochalasin D and latrunculin A. Our results indicate a marked decrease in the tyrosine phosphorylation of SNTA1 upon actin depolymerization. Results suggest that actin depolymerization mediated loss of SNTA1 phosphorylation leads to loss of interaction between SNTA1 and Rac1, with a concomitant loss of Rac1 activation. The loss of SNTA1tyrosine phosphorylation and Rac1 activity by actin depolymerization results in increased apoptosis, decreased cell migration and decreased reactive oxygen species (ROS) levels in breast carcinoma cells. Collectively, our results present a possible role of f-actin in the SNTA1-Rac1 signaling pathway and implications of actin depolymerization on cell migration, ROS production and apoptosis. PMID:27048259

  16. EspT triggers formation of lamellipodia and membrane ruffles through activation of Rac-1 and Cdc42

    PubMed Central

    Bulgin, Richard R; Arbeloa, Ana; Chung, Jade C S; Frankel, Gad

    2009-01-01

    Subversion of the eukaryotic cell cytoskeleton is a virulence strategy employed by many bacterial pathogens. Due to the pivotal role of Rho GTPases in actin dynamics they are common targets of bacterial effector proteins and toxins. IpgB1, IpgB2 (Shigella), SifA, SifB (Salmonella) and Map and EspM (attaching and effacing pathogens) constitute a family of type III secretion system effectors that subverts small GTPase signalling pathways. In this study we identified and characterized EspT from Citrobacter rodentium that triggers formation of lamellipodia on Swiss 3T3 and membrane ruffles on HeLa cells, which are reminiscent of the membrane ruffles induced by IpgB1. Ectopic expression of EspT and IpgB1, but not EspM, resulted in a mitochondrial localization. Using dominant negative constructs we found that EspT-induced actin remodelling is dependent on GTP-bound Rac-1 and Cdc42 but not ELMO or Dock180, which are hijacked by IpgB1 in order to form a Rac-1 specific guanine nucleotide exchange factor. Using pull-down assays with the Rac-1 and Cdc42 binding domains of Pak and WASP we demonstrate that EspT is capable of activating both Rac-1 and Cdc42. These results suggest that EspT modulates the host cell cytoskeleton through coactivation of Rac-1 and Cdc42 by a distinct mechanism. PMID:19016787

  17. DOCK2 regulates cell proliferation through Rac and ERK activation in B cell lymphoma

    SciTech Connect

    Wang, Lei; Nishihara, Hiroshi; Kimura, Taichi; Kato, Yasutaka; Tanino, Mishie; Nishio, Mitsufumi; Obara, Masato; Endo, Tomoyuki; Koike, Takao; Tanaka, Shinya

    2010-04-23

    DOCK2; a member of the CDM protein family, regulates cell motility and cytokine production through the activation of Rac in mammalian hematopoietic cells and plays a pivotal role in the modulation of the immune system. Here we demonstrated the alternative function of DOCK2 in hematopoietic tumor cells, especially in terms of its association with the tumor progression. Immunostaining for DOCK2 in 20 cases of human B cell lymphoma tissue specimens including diffuse large B cell lymphoma and follicular lymphoma revealed the prominent expression of DOCK2 in all of the lymphoma cells. DOCK2-knockdown (KD) of the B cell lymphoma cell lines, Ramos and Raji, using the lentiviral shRNA system presented decreased cell proliferation compared to the control cells. Furthermore, the tumor formation of DOCK2-KD Ramos cell in nude mice was significantly abrogated. Western blotting analysis and pull-down assay using GST-PAK-RBD kimeric protein suggested the presence of DOCK2-Rac-ERK pathway regulating the cell proliferation of these lymphoma cells. This is the first report to clarify the prominent role of DOCK2 in hematopoietic malignancy.

  18. PTEN inhibits PREX2-catalyzed activation of RAC1 to restrain tumor cell invasion

    PubMed Central

    Mense, Sarah M.; Barrows, Douglas; Hodakoski, Cindy; Steinbach, Nicole; Schoenfeld, David; Su, William; Hopkins, Benjamin D.; Su, Tao; Fine, Barry; Hibshoosh, Hanina; Parsons, Ramon

    2016-01-01

    The tumor suppressor PTEN restrains cell migration and invasion by a mechanism that is independent of inhibition of the PI3K pathway and decreased activation of the kinase AKT. PREX2, a widely distributed GEF that activates the GTPase RAC1, binds to and inhibits PTEN. We used mouse embryonic fibroblasts and breast cancer cell lines to show that PTEN suppresses cell migration and invasion by blocking PREX2 activity. In addition to metabolizing the phosphoinositide PIP3, PTEN inhibited PREX2-induced invasion by a mechanism that required the tail domain of PTEN, but not its lipid phosphatase activity. Fluorescent nucleotide exchange assays revealed that PTEN inhibited the GEF activity of PREX2 toward RAC1. PREX2 is a frequently mutated GEF in cancer, and examination of human tumor data showed that PREX2 mutation was associated with high PTEN expression. Therefore, we tested whether cancer-derived somatic PREX2 mutants, which accelerate tumor formation of immortalized melanocytes, were inhibited by PTEN. The three stably expressed, somatic PREX2 cancer mutants that we tested were resistant to PTEN-mediated inhibition of invasion but retained the ability to inhibit the lipid phosphatase activity of PTEN. In vitro analysis showed that PTEN did not block the GEF activity of two PREX2 cancer mutants and had a reduced binding affinity for the third. Thus, PTEN antagonized migration and invasion by restraining PREX2 GEF activity, and PREX2 mutants are likely selected in cancer to escape PTEN-mediated inhibition of invasion. PMID:25829446

  19. MgcRacGAP restricts active RhoA at the cytokinetic furrow and both RhoA and Rac1 at cell–cell junctions in epithelial cells

    PubMed Central

    Breznau, Elaina B.; Semack, Ansley C.; Higashi, Tomohito; Miller, Ann L.

    2015-01-01

    Localized activation of Rho GTPases is essential for multiple cellular functions, including cytokinesis and formation and maintenance of cell–cell junctions. Although MgcRacGAP (Mgc) is required for spatially confined RhoA-GTP at the equatorial cortex of dividing cells, both the target specificity of Mgc's GAP activity and the involvement of phosphorylation of Mgc at Ser-386 are controversial. In addition, Mgc's function at cell–cell junctions remains unclear. Here, using gastrula-stage Xenopus laevis embryos as a model system, we examine Mgc's role in regulating localized RhoA-GTP and Rac1-GTP in the intact vertebrate epithelium. We show that Mgc's GAP activity spatially restricts accumulation of both RhoA-GTP and Rac1-GTP in epithelial cells—RhoA at the cleavage furrow and RhoA and Rac1 at cell–cell junctions. Phosphorylation at Ser-386 does not switch the specificity of Mgc's GAP activity and is not required for successful cytokinesis. Furthermore, Mgc regulates adherens junction but not tight junction structure, and the ability to regulate adherens junctions is dependent on GAP activity and signaling via the RhoA pathway. Together these results indicate that Mgc's GAP activity down-regulates the active populations of RhoA and Rac1 at localized regions of epithelial cells and is necessary for successful cytokinesis and cell–cell junction structure. PMID:25947135

  20. Signal Transducer and Activator of Transcription-5 Mediates Neuronal Apoptosis Induced by Inhibition of Rac GTPase Activity*

    PubMed Central

    Stankiewicz, Trisha R.; Loucks, F. Alexandra; Schroeder, Emily K.; Nevalainen, Marja T.; Tyler, Kenneth L.; Aktories, Klaus; Bouchard, Ron J.; Linseman, Daniel A.

    2012-01-01

    In several neuronal cell types, the small GTPase Rac is essential for survival. We have shown previously that the Rho family GTPase inhibitor Clostridium difficile toxin B (ToxB) induces apoptosis in primary rat cerebellar granule neurons (CGNs) principally via inhibition of Rac GTPase function. In the present study, incubation with ToxB activated a proapoptotic Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, and a pan-JAK inhibitor protected CGNs from Rac inhibition. STAT1 expression was induced by ToxB; however, CGNs from STAT1 knock-out mice succumbed to ToxB-induced apoptosis as readily as wild-type CGNs. STAT3 displayed enhanced tyrosine phosphorylation following treatment with ToxB, and a reputed inhibitor of STAT3, cucurbitacin (JSI-124), reduced CGN apoptosis. Unexpectedly, JSI-124 failed to block STAT3 phosphorylation, and CGNs were not protected from ToxB by other known STAT3 inhibitors. In contrast, STAT5A tyrosine phosphorylation induced by ToxB was suppressed by JSI-124. In addition, roscovitine similarly inhibited STAT5A phosphorylation and protected CGNs from ToxB-induced apoptosis. Consistent with these results, adenoviral infection with a dominant negative STAT5 mutant, but not wild-type STAT5, significantly decreased ToxB-induced apoptosis of CGNs. Finally, chromatin immunoprecipitation with a STAT5 antibody revealed increased STAT5 binding to the promoter region of prosurvival Bcl-xL. STAT5 was recruited to the Bcl-xL promoter region in a ToxB-dependent manner, and this DNA binding preceded Bcl-xL down-regulation, suggesting transcriptional repression. These data indicate that a novel JAK/STAT5 proapoptotic pathway significantly contributes to neuronal apoptosis induced by the inhibition of Rac GTPase. PMID:22378792

  1. Signal transducer and activator of transcription-5 mediates neuronal apoptosis induced by inhibition of Rac GTPase activity.

    PubMed

    Stankiewicz, Trisha R; Loucks, F Alexandra; Schroeder, Emily K; Nevalainen, Marja T; Tyler, Kenneth L; Aktories, Klaus; Bouchard, Ron J; Linseman, Daniel A

    2012-05-11

    In several neuronal cell types, the small GTPase Rac is essential for survival. We have shown previously that the Rho family GTPase inhibitor Clostridium difficile toxin B (ToxB) induces apoptosis in primary rat cerebellar granule neurons (CGNs) principally via inhibition of Rac GTPase function. In the present study, incubation with ToxB activated a proapoptotic Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, and a pan-JAK inhibitor protected CGNs from Rac inhibition. STAT1 expression was induced by ToxB; however, CGNs from STAT1 knock-out mice succumbed to ToxB-induced apoptosis as readily as wild-type CGNs. STAT3 displayed enhanced tyrosine phosphorylation following treatment with ToxB, and a reputed inhibitor of STAT3, cucurbitacin (JSI-124), reduced CGN apoptosis. Unexpectedly, JSI-124 failed to block STAT3 phosphorylation, and CGNs were not protected from ToxB by other known STAT3 inhibitors. In contrast, STAT5A tyrosine phosphorylation induced by ToxB was suppressed by JSI-124. In addition, roscovitine similarly inhibited STAT5A phosphorylation and protected CGNs from ToxB-induced apoptosis. Consistent with these results, adenoviral infection with a dominant negative STAT5 mutant, but not wild-type STAT5, significantly decreased ToxB-induced apoptosis of CGNs. Finally, chromatin immunoprecipitation with a STAT5 antibody revealed increased STAT5 binding to the promoter region of prosurvival Bcl-xL. STAT5 was recruited to the Bcl-xL promoter region in a ToxB-dependent manner, and this DNA binding preceded Bcl-xL down-regulation, suggesting transcriptional repression. These data indicate that a novel JAK/STAT5 proapoptotic pathway significantly contributes to neuronal apoptosis induced by the inhibition of Rac GTPase. PMID:22378792

  2. Phosphorylation of Serine 402 Regulates RacGAP Protein Activity of FilGAP Protein.

    PubMed

    Morishita, Yuji; Tsutsumi, Koji; Ohta, Yasutaka

    2015-10-23

    FilGAP is a Rho GTPase-activating protein (GAP) that specifically regulates Rac. FilGAP is phosphorylated by ROCK, and this phosphorylation stimulates its RacGAP activity. However, it is unclear how phosphorylation regulates cellular functions and localization of FilGAP. We found that non-phosphorylatable FilGAP (ST/A) mutant is predominantly localized to the cytoskeleton along actin filaments and partially co-localized with vinculin around cell periphery, whereas phosphomimetic FilGAP (ST/D) mutant is diffusely cytoplasmic. Moreover, phosphorylated FilGAP detected by Phos-tag is also mainly localized in the cytoplasm. Of the six potential phosphorylation sites in FilGAP tested, only mutation of serine 402 to alanine (S402A) resulted in decreased cell spreading on fibronectin. FilGAP phosphorylated at Ser-402 is localized to the cytoplasm but not at the cytoskeleton. Although Ser-402 is highly phosphorylated in serum-starved quiescent cells, dephosphorylation of Ser-402 is accompanied with the cell spreading on fibronectin. Treatment of the cells expressing wild-type FilGAP with calyculin A, a Ser/Thr phosphatase inhibitor, suppressed cell spreading on fibronectin, whereas cells transfected with FilGAP S402A mutant were not affected by calyculin A. Expression of constitutively activate Arf6 Q67L mutant stimulated membrane blebbing activity of both non-phosphorylatable (ST/A) and phosphomimetic (ST/D) FilGAP mutants. Conversely, depletion of endogenous Arf6 suppressed membrane blebbing induced by FilGAP (ST/A) and (ST/D) mutants. Our study suggests that Arf6 and phosphorylation of FilGAP may regulate FilGAP, and phosphorylation of Ser-402 may play a role in the regulation of cell spreading on fibronectin. PMID:26359494

  3. Central Role of Protein Kinase Cε in Constitutive Activation of ERK1/2 and Rac1 in the Malignant Cells of Hairy Cell Leukemia

    PubMed Central

    Slupsky, Joseph R.; Kamiguti, Aura S.; Harris, Robert J.; Cawley, John C.; Zuzel, Mirko

    2007-01-01

    We have previously identified the presence of Ras/Raf-independent constitutive activation of extracellular signal-regulated kinase (ERK) in the hairy cells (HCs) of hairy cell leukemia. The aim of the present study was to characterize the signaling components involved in this activation and their relationship to the reported activation of Rac1. We found that both Rac1 and ERK activation in HCs are downstream of active Src and protein kinase C (PKC). Inhibition with toxin B showed that Rac1 plays no role in ERK activation in HCs. However, toxin B inhibited p60src and the Rac1-GEF Vav, demonstrating a positive feedback/activation of p60src by Rac1. Treatment with specific small interfering RNA for various PKC isoforms, or with PKC isoform-specific inhibitors, demonstrated a central role for PKCε in the constitutive activation of Rac1 and ERK in HCs. PKCε and active ERK were mutually associated and co-localized with mitochondria in HCs. Furthermore, active PKCε was nitrated on tyrosine, pointing to a reactive oxygen species-dependent mechanism of activation. By being involved in activation of ERK and Rac1, PKCε plays roles in both the survival of HCs and in the cytoskeletal dynamics responsible for the distinctive morphology and tissue homing of these cells. Our study therefore describes novel aspects of signaling important for the pathogenesis of hairy cell leukemia. PMID:17255340

  4. A MAPK-Driven Feedback Loop Suppresses Rac Activity to Promote RhoA-Driven Cancer Cell Invasion

    PubMed Central

    Hetmanski, Joseph H. R.; Zindy, Egor; Schwartz, Jean-Marc; Caswell, Patrick T.

    2016-01-01

    Cell migration in 3D microenvironments is fundamental to development, homeostasis and the pathobiology of diseases such as cancer. Rab-coupling protein (RCP) dependent co-trafficking of α5β1 and EGFR1 promotes cancer cell invasion into fibronectin (FN) containing extracellular matrix (ECM), by potentiating EGFR1 signalling at the front of invasive cells. This promotes a switch in RhoGTPase signalling to inhibit Rac1 and activate a RhoA-ROCK-Formin homology domain-containing 3 (FHOD3) pathway and generate filopodial actin-spike protrusions which drive invasion. To further understand the signalling network that drives RCP-driven invasive migration, we generated a Boolean logical model based on existing network pathways/models, where each node can be interrogated by computational simulation. The model predicted an unanticipated feedback loop, whereby Raf/MEK/ERK signalling maintains suppression of Rac1 by inhibiting the Rac-activating Sos1-Eps8-Abi1 complex, allowing RhoA activity to predominate in invasive protrusions. MEK inhibition was sufficient to promote lamellipodia formation and oppose filopodial actin-spike formation, and led to activation of Rac and inactivation of RhoA at the leading edge of cells moving in 3D matrix. Furthermore, MEK inhibition abrogated RCP/α5β1/EGFR1-driven invasive migration. However, upon knockdown of Eps8 (to suppress the Sos1-Abi1-Eps8 complex), MEK inhibition had no effect on RhoGTPase activity and did not oppose invasive migration, suggesting that MEK-ERK signalling suppresses the Rac-activating Sos1-Abi1-Eps8 complex to maintain RhoA activity and promote filopodial actin-spike formation and invasive migration. Our study highlights the predictive potential of mathematical modelling approaches, and demonstrates that a simple intervention (MEK-inhibition) could be of therapeutic benefit in preventing invasive migration and metastasis. PMID:27138333

  5. Rac1/p21-activated kinase pathway controls retinoblastoma protein phosphorylation and E2F transcription factor activation in B lymphocytes.

    PubMed

    Zaldua, Natalia; Llavero, Francisco; Artaso, Alain; Gálvez, Patricia; Lacerda, Hadriano M; Parada, Luis A; Zugaza, José L

    2016-02-01

    Small GTPases of the Ras superfamily are capable of activating E2F-dependent transcription leading to cell proliferation, but the molecular mechanisms are poorly understood. In this study, using immortalized chicken DT40 B cell lines to investigate the role of the Vav/Rac signalling cascade on B cell proliferation, it is shown that the proliferative response triggered by B cell receptor activation is dramatically reduced in the absence of Vav3 expression. Analysis of this proliferative defect shows that in the absence of Vav3 expression, retinoblastoma protein (RB) phosphorylation and the subsequent E2F activation do not take place. By combining pharmacological and genetic approaches, phosphatidylinositol-3-kinase and phospholipase Cγ2 (PLCγ2) were identified as the key regulatory signalling molecules upstream of the Vav3/Rac pathway leading to RB phosphorylation and E2F transcription factor activation. Additionally, vav3(-/-) and plcγ2(-/-) DT40 B cells were not able to activate the RB-E2F complex wild-type phenotype when these genetically modified cells were transfected with constitutively active forms of RhoA or Cdc42. However, when these knockout cells were transfected with different constitutively active versions of PLCγ, Vav or Rac1, not only activation of the RB-E2F complex wild-type phenotype was recovered but also the cellular proliferation. Furthermore, by evaluating the effect of two known effector mutants of Rac1 (Rac1(Q61L/F37A) and Rac1(Q61L/Y40C) ), the RB-E2F complex activation dependency on p21-activated kinase (PAK) and protein kinase Cε (PKCε) activities was established, being independent of both actin cytoskeleton reorganization and Ras activity. These results suggest that PAK1 and PKCε may be potential therapeutic targets to stop uncontrolled B cell proliferation mediated by the Vav/Rac pathway. PMID:26663827

  6. Foreign Body Giant Cell Formation Is Preceded by Lamellipodia Formation and Can Be Attenuated by Inhibition of Rac1 Activation

    PubMed Central

    Jay, Steven M.; Skokos, Eleni; Laiwalla, Farah; Krady, Marie-Marthe; Kyriakides, Themis R.

    2007-01-01

    Macrophages that are recruited to the site of implanted biomaterials undergo fusion to form surface-damaging foreign body giant cells. Exposure of peripheral blood monocytes to interleukin-4 can recapitulate the fusion process in vitro. In this study, we used interleukin-4 to induce multinucleation of murine bone marrow-derived macrophages and observed changes in cell shape, including elongation and lamellipodia formation, before fusion. Because cytoskeletal rearrangements are regulated by small GTPases, we examined the effects of inhibitors of Rho kinase (Y-32885) and Rac activation (NSC23766) on fusion. Y-32885 did not prevent cytoskeletal changes or fusion but limited the extent of multinucleation. NSC23766, on the other hand, inhibited lamellipodia formation and fusion in a dose-dependent manner. In addition, we found that in control cells, these changes were preceded by Rac1 activation. However, NSC23766 did not block the uptake of polystyrene microspheres. Likewise, short interfering RNA knockdown of Rac1 limited fusion without limiting phagocytosis. Thus, phagocytosis and fusion can be partially decoupled based on their susceptibility to NSC23766. Furthermore, poly(ethylene-co-vinyl acetate) scaffolds containing NSC23766 attenuated foreign body giant cell formation in vivo. These observations suggest that targeting Rac1 activation could protect biomaterials without compromising the ability of macrophages to perform beneficial phagocytic functions at implantation sites. PMID:17556592

  7. Association between Gαi2 and ELMO1/Dock180 connects chemokine signalling with Rac activation and metastasis.

    PubMed

    Li, Hongyan; Yang, Lei; Fu, Hui; Yan, Jianshe; Wang, Ying; Guo, Hua; Hao, Xishan; Xu, Xuehua; Jin, Tian; Zhang, Ning

    2013-01-01

    The chemokine CXCL12 and its G-protein-coupled receptor CXCR4 control the migration, invasiveness and metastasis of breast cancer cells. Binding of CXCL12 to CXCR4 triggers activation of heterotrimeric Gi proteins that regulate actin polymerization and migration. However, the pathways linking chemokine G-protein-coupled receptor/Gi signalling to actin polymerization and cancer cell migration are not known. Here we show that CXCL12 stimulation promotes interaction between Gαi2 and ELMO1. Gi signalling and ELMO1 are both required for CXCL12-mediated actin polymerization, migration and invasion of breast cancer cells. CXCL12 triggers a Gαi2-dependent membrane translocation of ELMO1, which associates with Dock180 to activate small G-proteins Rac1 and Rac2. In vivo, ELMO1 expression is associated with lymph node and distant metastasis, and knocking down ELMO1 impairs metastasis to the lung. Our findings indicate that a chemokine-controlled pathway, consisting of Gαi2, ELMO1/Dock180, Rac1 and Rac2, regulates the actin cytoskeleton during breast cancer metastasis. PMID:23591873

  8. Guanine Nucleotide Exchange Factor αPIX Leads to Activation of the Rac 1 GTPase/Glycogen Phosphorylase Pathway in Interleukin (IL)-2-stimulated T Cells

    PubMed Central

    Llavero, Francisco; Urzelai, Bakarne; Osinalde, Nerea; Gálvez, Patricia; Lacerda, Hadriano M.; Parada, Luis A.; Zugaza, José L.

    2015-01-01

    Recently, we have reported that the active form of Rac 1 GTPase binds to the glycogen phosphorylase muscle isoform (PYGM) and modulates its enzymatic activity leading to T cell proliferation. In the lymphoid system, Rac 1 and in general other small GTPases of the Rho family participate in the signaling cascades that are activated after engagement of the T cell antigen receptor. However, little is known about the IL-2-dependent Rac 1 activator molecules. For the first time, a signaling pathway leading to the activation of Rac 1/PYGM in response to IL-2-stimulated T cell proliferation is described. More specifically, αPIX, a known guanine nucleotide exchange factor for the small GTPases of the Rho family, preferentially Rac 1, mediates PYGM activation in Kit 225 T cells stimulated with IL-2. Using directed mutagenesis, phosphorylation of αPIX Rho-GEF serines 225 and 488 is required for activation of the Rac 1/PYGM pathway. IL-2-stimulated serine phosphorylation was corroborated in Kit 225 T cells cultures. A parallel pharmacological and genetic approach identified PKCθ as the serine/threonine kinase responsible for αPIX serine phosphorylation. The phosphorylated state of αPIX was required to activate first Rac 1 and subsequently PYGM. These results demonstrate that the IL-2 receptor activation, among other early events, leads to activation of PKCθ. To activate Rac 1 and consequently PYGM, PKCθ phosphorylates αPIX in T cells. The biological significance of this PKCθ/αPIX/Rac 1 GTPase/PYGM signaling pathway seems to be the control of different cellular responses such as migration and proliferation. PMID:25694429

  9. Mechanistic studies of anticancer aptamer AS1411 reveal a novel role for nucleolin in regulating Rac1 activation.

    PubMed

    Reyes-Reyes, E Merit; Šalipur, Francesca R; Shams, Mitra; Forsthoefel, Matthew K; Bates, Paula J

    2015-08-01

    AS1411 is a G-rich quadruplex-forming oligodeoxynucleotide that binds specifically to nucleolin, a protein found on the surface and in the cytoplasm of most malignant cells but absent from the surface/cytoplasm of most normal cells. AS1411 has shown promising clinical activity and is being widely used as a tumor-targeting agent, but its mechanism of action is not fully understood. Previously, we showed that AS1411 is taken up in cancer cells by macropinocytosis (fluid phase endocytosis) and subsequently stimulates further macropinocytosis by a nucleolin-dependent mechanism. In the current study, we have investigated the significance and molecular mechanisms of AS1411-induced macropinocytosis. Our results indicate that the antiproliferative activity of AS1411 in various cell lines correlated with its capacity to stimulate macropinocytosis. In DU145 prostate cancer cells, AS1411 induced activation of EGFR, Akt, p38, and Rac1. Activation of Akt and p38 were not critical for AS1411 activity because Akt activation was not observed in all AS1411-responsive cell lines and knockdown of p38 had no effect on AS1411's ability to inhibit proliferation. On the other hand, activation of EGFR and Rac1 appeared to play a role in AS1411 activity in all cancer cell lines examined (DU145, MDA-MB-468, A549, LNCaP) and their inhibition significantly reduced AS1411-mediated macropinocytosis and AS1411 antiproliferative activity. Interestingly, downregulation of nucleolin expression by siRNA also produced a substantial increase in activated Rac1, revealing a previously unknown role for nucleolin as a negative regulator of Rac1 activation. Our results are consistent with a model whereby AS1411 binding to nucleolin leads to sustained activation of Rac1 and causes methuosis, a novel type of nonapoptotic cell death characterized by hyperstimulation of macropinocytosis. We speculate that methuosis is a tumor/metastasis suppressor mechanism that opposes the malignant functions of Rac1 and that

  10. Cdc42 and Rac1 activity is reduced in human pheochromocytoma and correlates with FARP1 and ARHGEF1 expression.

    PubMed

    Croisé, Pauline; Houy, Sébastien; Gand, Mathieu; Lanoix, Joël; Calco, Valérie; Tóth, Petra; Brunaud, Laurent; Lomazzi, Sandra; Paramithiotis, Eustache; Chelsky, Daniel; Ory, Stéphane; Gasman, Stéphane

    2016-04-01

    Among small GTPases from the Rho family, Cdc42, RAC, and Rho are well known to mediate a large variety of cellular processes linked with cancer biology through their ability to cycle between an inactive (GDP-bound) and an active (GTP-bound) state. Guanine nucleotide exchange factors (GEFs) stimulate the exchange of GDP for GTP to generate the activated form, whereas the GTPase-activating proteins (GAPs) catalyze GTP hydrolysis, leading to the inactivated form. Modulation of Rho GTPase activity following altered expression of RHO-GEFs and/or RHO-GAPs has already been reported in various human tumors. However, nothing is known about the Rho GTPase activity or the expression of their regulators in human pheochromocytomas, a neuroendocrine tumor (NET) arising from chromaffin cells of the adrenal medulla. In this study, we demonstrate, through an ELISA-based activity assay, that Rac1 and Cdc42 activities decrease in human pheochromocytomas (PCCs) compared with the matched adjacent non-tumor tissue. Furthermore, through quantitative mass spectrometry (MS) approaches, we show that the expression of two RHO-GEF proteins, namely ARHGEF1 and FARP1, is significantly reduced in tumors compared with matched non-tumor tissue, whereas ARHGAP36 expression is increased. Moreover, siRNA-based knockdown of ARHGEF1 and FARP1 in PC12 cells leads to a significant inhibition of Rac1 and Cdc42 activities, respectively. Finally, a principal component analysis (PCA) of our dataset was able to discriminate PCC from non-tumor tissue and indicates a close correlation between Cdc42/Rac1 activity and FARP1/ARHGEF1 expression. Altogether, our findings reveal for the first time the importance of modulation of Rho GTPase activities and expression of their regulators in human PCCs. PMID:26911374

  11. Activated Rac1 regulates the degradation of IκBα and the nuclear translocation of STAT3–NFκB complexes in starved cancer cells

    PubMed Central

    Kim, Sung Joo; Yoon, Sarah

    2016-01-01

    In several human tumors, signal transducer and activator of transcription 3 (STAT3) and nuclear factor κB (NFκB) are activated and interact; how these STAT3–NFκB complexes are transported to the nucleus is not fully understood. In this study, we found that Rac1 was activated in starved cancer cells and that activated Rac1 coexisted with STAT3 and NFκB. Rac1 knockdown and overexpression of the dominant-negative mutant Rac1N19 inhibited the degradation of IκBα, an inhibitor of NFκB. MG132, an inhibitor of the ubiquitin proteasome pathway, increased the amount of non-phosphorylated IκBα, but not serine-phosphorylated IκBα, indicating that IκBα degradation by Rac1 in starved cancer cells is independent of IκBα serine phosphorylation by IKK. Rac1 knockdown also inhibited the nuclear translocation of STAT3–NFκB complexes, indicating that this translocation requires activated Rac1. We also demonstrated that the mutant STAT3 Y705F could form complexes with NFκB, and these unphosphorylated STAT3–NFκB complexes translocated into the nucleus and upregulated the activity of NFκB in starved cancer cells, suggesting that phosphorylation of STAT3 is not essential for its translocation. To our knowledge, this is the first study demonstrating the crucial role of Rac1 in the function of STAT3–NFκB complexes in starved cancer cells and implies that targeting Rac1 may have future therapeutic significance in cancer therapy. PMID:27151455

  12. Post-training activation of Rac1 in the basolateral amygdala is required for the formation of both short-term and long-term auditory fear memory

    PubMed Central

    Gao, Qinqin; Yao, Wenqing; Wang, Junjun; Yang, Tong; Liu, Cao; Tao, Yezheng; Chen, Yuejun; Liu, Xing; Ma, Lan

    2015-01-01

    Rac1, a member of the Rho family of small GTPases, is crucial for morphological changes of the mature neuronal synapse including spine formation and activity-dependent spine enlargement, while its role in the formation of associated memories, such as conditioned fear memory, is not clear. Here, we report that selective deletion of Rac1 in excitatory neurons, but not in parvalbumin inhibitory neurons, impaired short- and long-term memories (STM and LTM) of fear conditioning. Conditional knockout of Rac1 before associative fear training in the basolateral amygdala (BLA), a key area for fear memory acquisition and storage, impaired fear memory. The expression of dominant-negative mutant of Rac1, or infusion of Rac1 inhibitor NSC23766 into BLA blocked both STM and LTM of fear conditioning. Furthermore, selective inhibition of Rac1 activation in BLA immediately following fear conditioning impaired STM and LTM, demonstrating that fear conditioning-induced Rac1 activation in BLA plays a critical role in the formation of both STM and LTM of conditioned fear. PMID:26582975

  13. PTP1B inhibitor promotes endothelial cell motility by activating the DOCK180/Rac1 pathway

    PubMed Central

    Wang, Yuan; Yan, Feng; Ye, Qing; Wu, Xiao; Jiang, Fan

    2016-01-01

    Promoting endothelial cell (EC) migration is important not only for therapeutic angiogenesis, but also for accelerating re-endothelialization after vessel injury. Several recent studies have shown that inhibition of protein tyrosine phosphatase 1B (PTP1B) may promote EC migration and angiogenesis by enhancing the vascular endothelial growth factor receptor-2 (VEGFR2) signalling. In the present study, we demonstrated that PTP1B inhibitor could promote EC adhesion, spreading and migration, which were abolished by the inhibitor of Rac1 but not RhoA GTPase. PTP1B inhibitor significantly increased phosphorylation of p130Cas, and the interactions among p130Cas, Crk and DOCK180; whereas the phosphorylation levels of focal adhesion kinase, Src, paxillin, or Vav2 were unchanged. Gene silencing of DOCK180, but not Vav2, abrogated the effects of PTP1B inhibitor on EC motility. The effects of PTP1B inhibitor on EC motility and p130Cas/DOCK180 activation persisted in the presence of the VEGFR2 antagonist. In conclusion, we suggest that stimulation of the DOCK180 pathway represents an alternative mechanism of PTP1B inhibitor-stimulated EC motility, which does not require concomitant VEGFR2 activation as a prerequisite. Therefore, PTP1B inhibitor may be a useful therapeutic strategy for promoting EC migration in cardiovascular patients in which the VEGF/VEGFR functions are compromised. PMID:27052191

  14. Deficiency of Rac1 Blocks NADPH Oxidase Activation, Inhibits Endoplasmic Reticulum Stress, and Reduces Myocardial Remodeling in a Mouse Model of Type 1 Diabetes

    PubMed Central

    Li, Jianmin; Zhu, Huaqing; Shen, E; Wan, Li; Arnold, J. Malcolm O.; Peng, Tianqing

    2010-01-01

    OBJECTIVE Our recent study demonstrated that Rac1 and NADPH oxidase activation contributes to cardiomyocyte apoptosis in short-term diabetes. This study was undertaken to investigate if disruption of Rac1 and inhibition of NADPH oxidase would prevent myocardial remodeling in chronic diabetes. RESEARCH DESIGN AND METHODS Diabetes was induced by injection of streptozotocin in mice with cardiomyocyte-specific Rac1 knockout and their wild-type littermates. In a separate experiment, wild-type diabetic mice were treated with vehicle or apocynin in drinking water. Myocardial hypertrophy, fibrosis, endoplasmic reticulum (ER) stress, inflammatory response, and myocardial function were investigated after 2 months of diabetes. Isolated adult rat cardiomyocytes were cultured and stimulated with high glucose. RESULTS In diabetic hearts, NADPH oxidase activation, its subunits' expression, and reactive oxygen species production were inhibited by Rac1 knockout or apocynin treatment. Myocardial collagen deposition and cardiomyocyte cross-sectional areas were significantly increased in diabetic mice, which were accompanied by elevated expression of pro-fibrotic genes and hypertrophic genes. Deficiency of Rac1 or apocynin administration reduced myocardial fibrosis and hypertrophy, resulting in improved myocardial function. These effects were associated with a normalization of ER stress markers' expression and inflammatory response in diabetic hearts. In cultured cardiomyocytes, high glucose–induced ER stress was inhibited by blocking Rac1 or NADPH oxidase. CONCLUSIONS Rac1 via NADPH oxidase activation induces myocardial remodeling and dysfunction in diabetic mice. The role of Rac1 signaling may be associated with ER stress and inflammation. Thus, targeting inhibition of Rac1 and NADPH oxidase may be a therapeutic approach for diabetic cardiomyopathy. PMID:20522592

  15. Deletion of Wiskott-Aldrich syndrome protein triggers Rac2 activity and increased cross-presentation by dendritic cells.

    PubMed

    Baptista, Marisa A P; Keszei, Marton; Oliveira, Mariana; Sunahara, Karen K S; Andersson, John; Dahlberg, Carin I M; Worth, Austen J; Liedén, Agne; Kuo, I-Chun; Wallin, Robert P A; Snapper, Scott B; Eidsmo, Liv; Scheynius, Annika; Karlsson, Mikael C I; Bouma, Gerben; Burns, Siobhan O; Forsell, Mattias N E; Thrasher, Adrian J; Nylén, Susanne; Westerberg, Lisa S

    2016-01-01

    Wiskott-Aldrich syndrome (WAS) is caused by loss-of-function mutations in the WASp gene. Decreased cellular responses in WASp-deficient cells have been interpreted to mean that WASp directly regulates these responses in WASp-sufficient cells. Here, we identify an exception to this concept and show that WASp-deficient dendritic cells have increased activation of Rac2 that support cross-presentation to CD8(+) T cells. Using two different skin pathology models, WASp-deficient mice show an accumulation of dendritic cells in the skin and increased expansion of IFNγ-producing CD8(+) T cells in the draining lymph node and spleen. Specific deletion of WASp in dendritic cells leads to marked expansion of CD8(+) T cells at the expense of CD4(+) T cells. WASp-deficient dendritic cells induce increased cross-presentation to CD8(+) T cells by activating Rac2 that maintains a near neutral pH of phagosomes. Our data reveals an intricate balance between activation of WASp and Rac2 signalling pathways in dendritic cells. PMID:27425374

  16. Coordinated activation of the Rac-GAP β2-chimaerin by an atypical proline-rich domain and diacylglycerol.

    PubMed

    Gutierrez-Uzquiza, Alvaro; Colon-Gonzalez, Francheska; Leonard, Thomas A; Canagarajah, Bertram J; Wang, HongBin; Mayer, Bruce J; Hurley, James H; Kazanietz, Marcelo G

    2013-01-01

    Chimaerins, a family of GTPase activating proteins for the small G-protein Rac, have been implicated in development, neuritogenesis and cancer. These Rac-GTPase activating proteins are regulated by the lipid second messenger diacylglycerol generated by tyrosine kinases such as the epidermal growth factor receptor. Here we identify an atypical proline-rich motif in chimaerins that binds to the adaptor protein Nck1. Unlike most Nck1 partners, chimaerins bind to the third SH3 domain of Nck1. This association is mediated by electrostatic interactions of basic residues within the Pro-rich motif with acidic clusters in the SH3 domain. Epidermal growth factor promotes the binding of β2-chimaerin to Nck1 in the cell periphery in a diacylglycerol-dependent manner. Moreover, β2-chimaerin translocation to the plasma membrane and its peripheral association with Rac1 requires Nck1. Our studies underscore a coordinated mechanism for β2-chimaerin activation that involves lipid interactions via the C1 domain and protein-protein interactions via the N-terminal proline-rich region. PMID:23673634

  17. Deletion of Wiskott–Aldrich syndrome protein triggers Rac2 activity and increased cross-presentation by dendritic cells

    PubMed Central

    Baptista, Marisa A. P.; Keszei, Marton; Oliveira, Mariana; Sunahara, Karen K. S.; Andersson, John; Dahlberg, Carin I. M.; Worth, Austen J.; Liedén, Agne; Kuo, I-Chun; Wallin, Robert P. A.; Snapper, Scott B.; Eidsmo, Liv; Scheynius, Annika; Karlsson, Mikael C. I.; Bouma, Gerben; Burns, Siobhan O.; Forsell, Mattias N. E.; Thrasher, Adrian J.; Nylén, Susanne; Westerberg, Lisa S.

    2016-01-01

    Wiskott–Aldrich syndrome (WAS) is caused by loss-of-function mutations in the WASp gene. Decreased cellular responses in WASp-deficient cells have been interpreted to mean that WASp directly regulates these responses in WASp-sufficient cells. Here, we identify an exception to this concept and show that WASp-deficient dendritic cells have increased activation of Rac2 that support cross-presentation to CD8+ T cells. Using two different skin pathology models, WASp-deficient mice show an accumulation of dendritic cells in the skin and increased expansion of IFNγ-producing CD8+ T cells in the draining lymph node and spleen. Specific deletion of WASp in dendritic cells leads to marked expansion of CD8+ T cells at the expense of CD4+ T cells. WASp-deficient dendritic cells induce increased cross-presentation to CD8+ T cells by activating Rac2 that maintains a near neutral pH of phagosomes. Our data reveals an intricate balance between activation of WASp and Rac2 signalling pathways in dendritic cells. PMID:27425374

  18. Narrow-band UVB radiation promotes dendrite formation by activating Rac1 in B16 melanoma cells.

    PubMed

    Wang, Wu-Qing; Wu, Jin-Feng; Xiao, Xiao-Qing; Xiao, Qin; Wang, Jing; Zuo, Fu-Guo

    2013-09-01

    Melanocytes are found scattered throughout the basal layer of the epidermis. Following hormone or ultraviolet (UV) light stimulation, the melanin pigments contained in melanocytes are transferred through the dendrites to the surrounding keratinocytes to protect against UV light damage or carcinogenesis. This has been considered as a morphological indicator of melanocytes and melanoma cells. Small GTPases of the Rho family have been implicated in the regulation of actin reorganization underlying dendrite formation in melanocytes and melanoma cells. It has been proven that ultraviolet light plays a pivotal role in melanocyte dendrite formation; however, the molecular mechanism underlying this process has not been fully elucidated. The effect of small GTPases, such as Rac1 and RhoA, on the morphology of B16 melanoma cells treated with narrow-band UVB radiation was investigated. The morphological changes were observed under a phase contrast microscope and the F-actin microfilament of the cytoskeleton was observed under a laser scanning confocal microscope. The pull-down assay was performed to detect the activity of the small GTPases Rac1 and RhoA. The morphological changes were evident, with globular cell bodies and increased numbers of tree branch-like dendrites. The cytoskeletal F-actin appeared disassembled following narrow-band UVB irradiation of B16 melanoma cells. Treatment of B16 melanoma cells with narrow-band UVB radiation resulted in the activation of Rac1 in a time-dependent manner. In conclusion, the present study may provide a novel method through which narrow-band UVB radiation may be used to promote dendrite formation by activating the Rac1 signaling pathway, resulting in F-actin rearrangement in B16 melanoma cells. PMID:24649261

  19. Rac1 Activation Caused by Membrane Translocation of a Guanine Nucleotide Exchange Factor in Akt2-Mediated Insulin Signaling in Mouse Skeletal Muscle

    PubMed Central

    Takenaka, Nobuyuki; Nihata, Yuma; Satoh, Takaya

    2016-01-01

    Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4, which is translocated to the plasma membrane following insulin stimulation. Several lines of evidence suggested that the protein kinase Akt2 plays a key role in this insulin action. The small GTPase Rac1 has also been implicated as a regulator of insulin-stimulated GLUT4 translocation, acting downstream of Akt2. However, the mechanisms whereby Akt2 regulates Rac1 activity remain obscure. The guanine nucleotide exchange factor FLJ00068 has been identified as a direct regulator of Rac1 in Akt2-mediated signaling, but its characterization was performed mostly in cultured myoblasts. Here, we provide in vivo evidence that FLJ00068 indeed acts downstream of Akt2 as a Rac1 regulator by using mouse skeletal muscle. Small interfering RNA knockdown of FLJ00068 markedly diminished GLUT4 translocation to the sarcolemma following insulin administration or ectopic expression of a constitutively activated mutant of either phosphoinositide 3-kinase or Akt2. Additionally, insulin and these constitutively activated mutants caused the activation of Rac1 as shown by immunofluorescent microscopy using a polypeptide probe specific to activated Rac1 in isolated gastrocnemius muscle fibers and frozen sections of gastrocnemius muscle. This Rac1 activation was also abrogated by FLJ00068 knockdown. Furthermore, we observed translocation of FLJ00068 to the cell periphery following insulin stimulation in cultured myoblasts. Localization of FLJ00068 in the plasma membrane in insulin-stimulated, but not unstimulated, myoblasts and mouse gastrocnemius muscle was further affirmed by subcellular fractionation and subsequent immunoblotting. Collectively, these results strongly support a critical role of FLJ00068 in Akt2-mediated Rac1 activation in mouse skeletal muscle insulin signaling. PMID:27163697

  20. The novel RacE-binding protein GflB sharpens Ras activity at the leading edge of migrating cells

    PubMed Central

    Senoo, Hiroshi; Cai, Huaqing; Wang, Yu; Sesaki, Hiromi; Iijima, Miho

    2016-01-01

    Directional sensing, a process in which cells convert an external chemical gradient into internal signaling events, is essential in chemotaxis. We previously showed that a Rho GTPase, RacE, regulates gradient sensing in Dictyostelium cells. Here, using affinity purification and mass spectrometry, we identify a novel RacE-binding protein, GflB, which contains a Ras GEF domain and a Rho GAP domain. Using biochemical and gene knockout approaches, we show that GflB balances the activation of Ras and Rho GTPases, which enables cells to precisely orient signaling events toward higher concentrations of chemoattractants. Furthermore, we find that GflB is located at the leading edge of migrating cells, and this localization is regulated by the actin cytoskeleton and phosphatidylserine. Our findings provide a new molecular mechanism that connects directional sensing and morphological polarization. PMID:27009206

  1. The novel RacE-binding protein GflB sharpens Ras activity at the leading edge of migrating cells.

    PubMed

    Senoo, Hiroshi; Cai, Huaqing; Wang, Yu; Sesaki, Hiromi; Iijima, Miho

    2016-05-15

    Directional sensing, a process in which cells convert an external chemical gradient into internal signaling events, is essential in chemotaxis. We previously showed that a Rho GTPase, RacE, regulates gradient sensing in Dictyostelium cells. Here, using affinity purification and mass spectrometry, we identify a novel RacE-binding protein, GflB, which contains a Ras GEF domain and a Rho GAP domain. Using biochemical and gene knockout approaches, we show that GflB balances the activation of Ras and Rho GTPases, which enables cells to precisely orient signaling events toward higher concentrations of chemoattractants. Furthermore, we find that GflB is located at the leading edge of migrating cells, and this localization is regulated by the actin cytoskeleton and phosphatidylserine. Our findings provide a new molecular mechanism that connects directional sensing and morphological polarization. PMID:27009206

  2. Ultrasonic Stimulation of Mouse Skin Reverses the Healing Delays in Diabetes and Aging by Activation of Rac1.

    PubMed

    Roper, James A; Williamson, Rosalind C; Bally, Blandine; Cowell, Christopher A M; Brooks, Rebecca; Stephens, Phil; Harrison, Andrew J; Bass, Mark D

    2015-11-01

    Chronic skin-healing defects are one of the leading challenges to lifelong well-being, affecting 2-5% of populations. Chronic wound formation is linked to age and diabetes and frequently leads to major limb amputation. Here we identify a strategy to reverse fibroblast senescence and improve healing rates. In healthy skin, fibronectin activates Rac1 in fibroblasts, causing migration into the wound bed, and driving wound contraction. We discover that mechanical stimulation of the skin with ultrasound can overturn healing defects by activating a calcium/CamKinaseII/Tiam1/Rac1 pathway that substitutes for fibronectin-dependent signaling and promotes fibroblast migration. Treatment of diabetic and aged mice recruits fibroblasts to the wound bed and reduces healing times by 30%, restoring healing rates to those observed in young, healthy animals. Ultrasound treatment is equally effective in rescuing the healing defects of animals lacking fibronectin receptors, and can be blocked by pharmacological inhibition of the CamKinaseII pathway. Finally, we discover that the migration defects of fibroblasts from human venous leg ulcer patients can be reversed by ultrasound, demonstrating that the approach is applicable to human chronic samples. By demonstrating that this alternative Rac1 pathway can substitute for that normally operating in the skin, we identify future opportunities for management of chronic wounds. PMID:26079528

  3. Ultrasonic stimulation of mouse skin reverses the healing delays in diabetes and aging by activation of Rac1

    PubMed Central

    Roper, James A; Williamson, Rosalind C; Bally, Blandine; Cowell, Christopher AM; Brooks, Rebecca; Stephens, Phil; Harrison, Andrew J; Bass, Mark D

    2015-01-01

    Chronic skin healing defects are one of the leading challenges to lifelong wellbeing, affecting 2-5% of populations. Chronic wound formation is linked to age and diabetes and frequently leads to major limb amputation. Here we identify a strategy to reverse fibroblast senescence and improve healing rates. In healthy skin, fibronectin activates Rac1 in fibroblasts, causing migration into the wound bed and driving wound contraction. We discover that mechanical stimulation of skin with ultrasound can overturn healing defects by activating a calcium/CamKinaseII/Tiam1/Rac1 pathway that substitutes for fibronectin-dependent signaling and promotes fibroblast migration. Treatment of diabetic and aged mice recruits fibroblasts to the wound bed and reduces healing times by 30%, restoring healing rates to those observed in young, healthy animals. Ultrasound treatment is equally effective in rescuing the healing defects of animals lacking fibronectin receptors, and can be blocked by pharmacological inhibition of the CamKinaseII pathway. Finally, we discover that the migration defects of fibroblasts from human venous leg ulcer patients can be reversed by ultrasound, demonstrating that the approach is applicable to human chronic samples. By demonstrating that this alternative Rac1 pathway can substitute for that normally operating in skin, we identify future opportunities for management of chronic wounds. PMID:26079528

  4. Removal of 2-ClBP from soil-water system using activated carbon supported nanoscale zerovalent iron.

    PubMed

    Zhang, Wei; Yu, Tian; Han, Xiaolin; Ying, Weichi

    2016-09-01

    We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl (2-ClBP) from soil-water system using granular activated carbon (GAC) impregnated with nanoscale zerovalent iron (reactive activated carbon or RAC). The RAC samples were successfully synthesized by the liquid precipitation method. The mesoporous GAC based RAC with low iron content (1.32%) exhibited higher 2-ClBP removal efficiency (54.6%) in the water phase. The result of Langmuir-Hinshelwood kinetic model implied that the different molecular structures between 2-ClBP and trichloroethylene (TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities. Compared to removing 2-ClBP in the water phase, RAC removed the 2-ClBP more slowly in the soil phase due to the significant external mass transfer resistance. However, in the soil phase, a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-ClBP. This important result verified the effectiveness of RAC for removing 2-ClBP in the soil phase. Although reducing the total RAC removal rate of 2-ClBP, soil organic matter (SOM), especially the soft carbon, also served as an electron transfer medium to promote the dechlorination of 2-ClBP in the long term. PMID:27593281

  5. Effect Of Reaction Environments On The Reactivity Of PCB (2-Chlorobiphenyl) Over Activated Carbon Impregnated With Palladized Iron

    EPA Science Inventory

    Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-...

  6. Effects Of Aging And Oxidation Of Palladized Iron Embedded In Activated Carbon On The Dechlorination Of 2-Chlorobiphenyl

    EPA Science Inventory

    Reactive activated carbon (RAC) impregnated with palladized iron has been developed to effectively treat polychlorinated biphenyls (PCBs) in the environment by coupling adsorption and dechlorination of PCBs. In this study, we addressed the dechlorination reactivity and capacity ...

  7. Stability and cellular studies of [rac-1,2-bis(4-fluorophenyl)-ethylenediamine][cyclobutane-1,1- dicarboxylato]platinum(II), a novel, highly active carboplatin derivative.

    PubMed

    Gust, R; Schnurr, B; Krauser, R; Bernhardt, G; Koch, M; Schmid, B; Hummel, E; Schönenberger, H

    1998-01-01

    The synthesis of the diastereomeric [1,2-bis(4-fluorophenyl)ethylenediamine][cyclobutane-1, 1-dicarboxylato]platinum(II) complexes, rac- and meso-4F-Pt(CBDC), the evaluation of their structures, their tumor-inhibiting properties and their stability in physiological environment are described (reference complexes: the dichloro- and sulfatoplatinum(II) analogues, carboplatin and cisplatin). The most interesting diastereomer, rac-4F-Pt(CBDC), equals cisplatin and surpasses carboplatin in its effect on human breast cancer cell lines (MCF-7 and MDA-MB-231). Rac-4F-Pt(CBDC) is largely insensitive against attack of nucleophiles e.g. Cl-, a prerequisite for sufficient stability in vivo and for fewer side effects. In accordance with this, in vitro studies on the binding of rac-4F-Pt(CBDC) to albumin, the main plasma protein, show that the free, non-protein-bound fraction is relatively high, coming close to that of carboplatin. These properties are of importance for the transferability of the promising effects found in the cell culture experiments to in vivo conditions. The distinctly better anti-breast cancer activity of rac-4F-Pt(CBDC) than of carboplatin has been attributed to its ability to accumulate in the tumor cells. The human ovarian cancer cell line NIH-OVCAR-3 is also strongly inhibited by rac-4F-Pt(CBDC). PMID:9860287

  8. Adhesion-related kinase induction of migration requires phosphatidylinositol-3-kinase and ras stimulation of rac activity in immortalized gonadotropin-releasing hormone neuronal cells.

    PubMed

    Nielsen-Preiss, Sheila M; Allen, Melissa P; Xu, Mei; Linseman, Daniel A; Pawlowski, John E; Bouchard, R J; Varnum, Brian C; Heidenreich, Kim A; Wierman, Margaret E

    2007-06-01

    GnRH neurons migrate into the hypothalamus during development. Although migratory defects may result in disordered activation of the reproductive axis and lead to delayed or absent sexual maturation, specific factors regulating GnRH neuronal migration remain largely unknown. The receptor tyrosine kinase, adhesion-related kinase (Ark) (also known as Axl, UFO, and Tyro7), has been implicated in the migration of GnRH neuronal cells. Binding of its ligand, growth arrest-specific gene 6 (Gas6), promotes cytoskeletal remodeling and migration of NLT GnRH neuronal cells via Rac and p38 MAPK. Here, we examined the Axl effectors proximal to Rac in the signaling pathway. Gas6/Axl-induced lamellipodia formation and migration were blocked after phosphatidylinositol-3-kinase (PI3K) inhibition in GnRH neuronal cells. The p85 subunit of PI3K coimmunoprecipitated with Axl and was phosphorylated in a Gas6-sensitive manner. In addition, PI3K inhibition in GnRH neuronal cells diminished Gas6-induced Rac activation. Exogenous expression of a dominant-negative form of Ras also decreased GnRH neuronal lamellipodia formation, migration, and Rac activation. PI3K inhibition blocked Ras in addition to Rac activation and migration. In contrast, pharmacological blockade of the phospholipase C gamma effectors, protein kinase C or calcium/calmodulin protein kinase II, had no effect on Gas6/Axl signaling to promote Rac activation or stimulate cytoskeletal reorganization and migration. Together, these data show that the PI3K-Ras pathway is a major mediator of Axl actions upstream of Rac to induce GnRH neuronal cell migration. PMID:17332061

  9. The Guanine Nucleotide Exchange Factor (GEF) Asef2 Promotes Dendritic Spine Formation via Rac Activation and Spinophilin-dependent Targeting*

    PubMed Central

    Evans, J. Corey; Robinson, Cristina M.; Shi, Mingjian; Webb, Donna J.

    2015-01-01

    Dendritic spines are actin-rich protrusions that establish excitatory synaptic contacts with surrounding neurons. Reorganization of the actin cytoskeleton is critical for the development and plasticity of dendritic spines, which is the basis for learning and memory. Rho family GTPases are emerging as important modulators of spines and synapses, predominantly through their ability to regulate actin dynamics. Much less is known, however, about the function of guanine nucleotide exchange factors (GEFs), which activate these GTPases, in spine and synapse development. In this study we show that the Rho family GEF Asef2 is found at synaptic sites, where it promotes dendritic spine and synapse formation. Knockdown of endogenous Asef2 with shRNAs impairs spine and synapse formation, whereas exogenous expression of Asef2 causes an increase in spine and synapse density. This effect of Asef2 on spines and synapses is abrogated by expression of GEF activity-deficient Asef2 mutants or by knockdown of Rac, suggesting that Asef2-Rac signaling mediates spine development. Because Asef2 interacts with the F-actin-binding protein spinophilin, which localizes to spines, we investigated the role of spinophilin in Asef2-promoted spine formation. Spinophilin recruits Asef2 to spines, and knockdown of spinophilin hinders spine and synapse formation in Asef2-expressing neurons. Furthermore, inhibition of N-methyl-d-aspartate receptor (NMDA) activity blocks spinophilin-mediated localization of Asef2 to spines. These results collectively point to spinophilin-Asef2-Rac signaling as a novel mechanism for the development of dendritic spines and synapses. PMID:25750125

  10. Desorption, partitioning, and dechlorination characteristics of PCBs in sediments in interaction with reactive activated carbon.

    PubMed

    Choi, Hyeok; Lawal, Wasiu; Al-Abed, Souhail R

    2015-04-28

    Sediment (WHS) in Waukegan Harbor, Illinois, heavily contaminated and aged with polychlorinated biphenyls (PCBs), was treated with reactive activated carbon (RAC) impregnated with palladized iron nanoparticles. Lab test proceeded in a direct mixing configuration of RAC and WHS. A compartment configuration, where RAC was physically separated from WHS, was also designed to trace the sequential transport and fate of PCBs, including desorption, adsorption, dechlorination, and re-partitioning. PCBs, once desorbed from WHS, were immediately sequestrated to RAC and subject to dechlorination. Direct mixing of WHS with RAC was one-order of magnitude more effective for dechlorination than compartment configuration. Compared to their desorption-followed by-adsorption route, direct physical contact of RAC with PCBs bound to WHS exhibited negligible contribution to the availability of PCBs for dechlorination reaction. Addition of RAC even in compartment configuration facilitated PCBs desorption from WHS. However, slow desorption of PCBs limited overall performance, resulting in a five-order of magnitude lower dechlorination yield when compared with treatment of purely aqueous PCBs. The low dechlorination yield reflected real world complexities in treating 3.19% organic carbon-containing WHS aged with PCBs for 40 years. These observations were further supported when compared with results on clean Cesar Creek sediment spiked with 2-chlorinated biphenyls. PMID:25636140

  11. Cucurbitacin I Inhibits Rac1 Activation in Breast Cancer Cells by a Reactive Oxygen Species-Mediated Mechanism and Independently of Janus Tyrosine Kinase 2 and P-Rex1

    PubMed Central

    Lopez-Haber, Cynthia

    2013-01-01

    The small GTPase Rac1 has been widely implicated in mammary tumorigenesis and metastasis. Previous studies established that stimulation of ErbB receptors in breast cancer cells activates Rac1 and enhances motility via the Rac-guanine nucleotide exchange factor P-Rex1. As the Janus tyrosine kinase 2 (Jak2)/signal transducer and activator of transcription 3 (Stat3) pathway has been shown to be functionally associated with ErbB receptors, we asked if this pathway could mediate P-Rex1/Rac1 activation in response to ErbB ligands. Here we found that the anticancer agent cucurbitacin I, a Jak2 inhibitor, reduced the activation of Rac1 and motility in response to the ErbB3 ligand heregulin in breast cancer cells. However, Rac1 activation was not affected by Jak2 or Stat3 RNA interference, suggesting that the effect of cucurbitacin I occurs through a Jak2-independent mechanism. Cucurbitacin I also failed to affect the activation of P-Rex1 by heregulin. Subsequent analysis revealed that cucurbitacin I strongly activates RhoA and the Rho effector Rho kinase (ROCK) in breast cancer cells and induces the formation of stress fibers. Interestingly, disruption of the RhoA-ROCK pathway prevented the inhibitory effect of cucurbitacin I on Rac1 activation by heregulin. Lastly, we found that RhoA activation by cucurbitacin I is mediated by reactive oxygen species (ROS). The ROS scavenger N-acetyl l-cysteine and the mitochondrial antioxidant Mito-TEMPO rescued the inhibitory effect of cucurbitacin I on Rac1 activation. In conclusion, these results indicate that ErbB-driven Rac1 activation in breast cancer cells proceeds independently of the Jak2 pathway. Moreover, they established that the inhibitory effect of cucurbitacin I on Rac1 activity involves the alteration of the balance between Rho and Rac. PMID:23478800

  12. The RhoE/ROCK/ARHGAP25 signaling pathway controls cell invasion by inhibition of Rac activity.

    PubMed

    Thuault, Sylvie; Comunale, Franck; Hasna, Jessy; Fortier, Mathieu; Planchon, Damien; Elarouci, Nabila; De Reynies, Aurélien; Bodin, Stéphane; Blangy, Anne; Gauthier-Rouvière, Cécile

    2016-09-01

    Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of skeletal muscle origin in children and adolescents. Among RMS subtypes, alveolar rhabdomyosarcoma (ARMS), which is characterized by the presence of the PAX3-FOXO1A or PAX7-FOXO1A chimeric oncogenic transcription factor, is associated with poor prognosis and a strong risk of metastasis compared with the embryonal subtype (ERMS). To identify molecular pathways involved in ARMS aggressiveness, we first characterized the migratory behavior of cell lines derived from ARMS and ERMS biopsies using a three-dimensional spheroid cell invasion assay. ARMS cells were more invasive than ERMS cells and adopted an ellipsoidal morphology to efficiently invade the extracellular matrix. Moreover, the invasive potential of ARMS cells depended on ROCK activity, which is regulated by the GTPase RhoE. Specifically, RhoE expression was low in ARMS biopsies, and its overexpression in ARMS cells reduced their invasion potential. Conversely, ARHGAP25, a GTPase-activating protein for Rac, was up-regulated in ARMS biopsies. Moreover, we found that ARHGAP25 inhibits Rac activity downstream of ROCKII and is required for ARMS cell invasion. Our results indicate that the RhoE/ROCK/ARHGAP25 signaling pathway promotes ARMS invasive potential and identify these proteins as potential therapeutic targets for ARMS treatment. PMID:27413008

  13. Redox regulation of Rac1 by thiol oxidation.

    PubMed

    Hobbs, G Aaron; Mitchell, Lauren E; Arrington, Megan E; Gunawardena, Harsha P; DeCristo, Molly J; Loeser, Richard F; Chen, Xian; Cox, Adrienne D; Campbell, Sharon L

    2015-02-01

    The Rac1 GTPase is an essential and ubiquitous protein that signals through numerous pathways to control critical cellular processes, including cell growth, morphology, and motility. Rac1 deletion is embryonic lethal, and its dysregulation or mutation can promote cancer, arthritis, cardiovascular disease, and neurological disorders. Rac1 activity is highly regulated by modulatory proteins and posttranslational modifications. Whereas much attention has been devoted to guanine nucleotide exchange factors that act on Rac1 to promote GTP loading and Rac1 activation, cellular oxidants may also regulate Rac1 activation by promoting guanine nucleotide exchange. Herein, we show that Rac1 contains a redox-sensitive cysteine (Cys(18)) that can be selectively oxidized at physiological pH because of its lowered pKa. Consistent with these observations, we show that Rac1 is glutathiolated in primary chondrocytes. Oxidation of Cys(18) by glutathione greatly perturbs Rac1 guanine nucleotide binding and promotes nucleotide exchange. As aspartate substitutions have been previously used to mimic cysteine oxidation, we characterized the biochemical properties of Rac1(C18D). We also evaluated Rac1(C18S) as a redox-insensitive variant and found that it retains structural and biochemical properties similar to those of Rac1(WT) but is resistant to thiol oxidation. In addition, Rac1(C18D), but not Rac1(C18S), shows greatly enhanced nucleotide exchange, similar to that observed for Rac1 oxidation by glutathione. We employed Rac1(C18D) in cell-based studies to assess whether this fast-cycling variant, which mimics Rac1 oxidation by glutathione, affects Rac1 activity and function. Expression of Rac1(C18D) in Swiss 3T3 cells showed greatly enhanced GTP-bound Rac1 relative to Rac1(WT) and the redox-insensitive Rac1(C18S) variant. Moreover, expression of Rac1(C18D) in HEK-293T cells greatly promoted lamellipodia formation. Our results suggest that Rac1 oxidation at Cys(18) is a novel

  14. The P2Y2 Receptor Interacts with VE-Cadherin and VEGF Receptor-2 to Regulate Rac1 Activity in Endothelial Cells

    PubMed Central

    Liao, Zhongji; Cao, Chen; Wang, Jianjie; Huxley, Virginia H.; Baker, Olga; Weisman, Gary A.

    2015-01-01

    Vascular endothelial cadherin (VE-cadherin) mediates homophylic adhesion between endothelial cells and is an important regulator of angiogenesis, blood vessel permeability and leukocyte trafficking. Rac1, a member of the Rho family of GTPases, controls VE-cadherin adhesion by acting downstream of several growth factors, including angiopoietin-1 and vascular endothelial growth factor (VEGF). Here we show that UTP-induced activation of the Gq protein-coupled P2Y2 nucleotide receptor (P2Y2R) in human coronary artery endothelial cells (HCAECs) activated Rac1 and caused a transient complex to form between P2Y2R, VE-cadherin and VEGF receptor-2 (VEGFR-2). Knockdown of VE-cadherin expression with siRNA did not affect UTP-induced activation of extracellular signal-regulated kinases 1/2 (ERK1/2) but led to a loss of UTP-induced Rac1 activation and tyrosine phosphorylation of p120 catenin, a cytoplasmic protein known to interact with VE-cadherin. Activation of the P2Y2R by UTP also caused a prolonged interaction between p120 catenin and vav2 (a guanine nucleotide exchange factor for Rac) that correlated with the kinetics of UTP-induced tyrosine phosphorylation of p120 catenin and VE-cadherin. Inhibitors of VEGFR-2 (SU1498) or Src (PP2) significantly diminished UTP-induced Rac1 activation, tyrosine phosphorylation of p120 catenin and VE-cadherin, and association of the P2Y2R with VE-cadherin and p120 catenin with vav2. These findings suggest that the P2Y2R uses Src and VEGFR-2 to mediate association of the P2Y2R with VE-cadherin complexes in endothelial adherens junctions to activate Rac1. PMID:25657827

  15. Association of syntenin-1 with M-RIP polarizes Rac-1 activation during chemotaxis and immune interactions.

    PubMed

    Sala-Valdés, Mónica; Gordón-Alonso, Mónica; Tejera, Emilio; Ibáñez, Anna; Cabrero, J Román; Ursa, Angeles; Mittelbrunn, María; Lozano, Francisco; Sánchez-Madrid, Francisco; Yáñez-Mó, María

    2012-03-01

    In this study, we describe that the PDZ protein syntenin-1 is a crucial element for the generation of signaling asymmetry during the cellular response to polarized extracellular cues. We analyze the role of syntenin-1 in the control of asymmetry in two independent models of T cell polarization--the migratory response to chemoattractants and the establishment of cognate interactions between T cells and antigen-presenting cells (APCs). A combination of mutant, biochemical and siRNA approaches demonstrate that syntenin-1 is vital for the generation of polarized actin structures such as the leading edge and the contact zone with APCs. We found that the mechanism by which syntenin-1 controls actin polymerization relies on its mandatory role for activation of the small GTPase Rac. Syntenin-1 controls Rac through a specific association with the myosin phosphatase Rho interacting protein (M-RIP), which occurs in response to phosphorylation of syntenin-1 by Src at Tyr4. Our data indicate the key role of syntenin-1 in the generation of functional asymmetry in T cells and provide a novel mechanistic link between receptor activation and actin polymerization and accumulation in response to extracellular stimulation. PMID:22349701

  16. Inability to activate Rac1-dependent forgetting contributes to behavioral inflexibility in mutants of multiple autism-risk genes.

    PubMed

    Dong, Tao; He, Jing; Wang, Shiqing; Wang, Lianzhang; Cheng, Yuqi; Zhong, Yi

    2016-07-01

    The etiology of autism is so complicated because it involves the effects of variants of several hundred risk genes along with the contribution of environmental factors. Therefore, it has been challenging to identify the causal paths that lead to the core autistic symptoms such as social deficit, repetitive behaviors, and behavioral inflexibility. As an alternative approach, extensive efforts have been devoted to identifying the convergence of the targets and functions of the autism-risk genes to facilitate mapping out causal paths. In this study, we used a reversal-learning task to measure behavioral flexibility in Drosophila and determined the effects of loss-of-function mutations in multiple autism-risk gene homologs in flies. Mutations of five autism-risk genes with diversified molecular functions all led to a similar phenotype of behavioral inflexibility indicated by impaired reversal-learning. These reversal-learning defects resulted from the inability to forget or rather, specifically, to activate Rac1 (Ras-related C3 botulinum toxin substrate 1)-dependent forgetting. Thus, behavior-evoked activation of Rac1-dependent forgetting has a converging function for autism-risk genes. PMID:27335463

  17. Differential Rac1 signalling by guanine nucleotide exchange factors implicates FLII in regulating Rac1-driven cell migration

    PubMed Central

    Marei, Hadir; Carpy, Alejandro; Woroniuk, Anna; Vennin, Claire; White, Gavin; Timpson, Paul; Macek, Boris; Malliri, Angeliki

    2016-01-01

    The small GTPase Rac1 has been implicated in the formation and dissemination of tumours. Upon activation by guanine nucleotide exchange factors (GEFs), Rac1 associates with a variety of proteins in the cell thereby regulating various functions, including cell migration. However, activation of Rac1 can lead to opposing migratory phenotypes raising the possibility of exacerbating tumour progression when targeting Rac1 in a clinical setting. This calls for the identification of factors that influence Rac1-driven cell motility. Here we show that Tiam1 and P-Rex1, two Rac GEFs, promote Rac1 anti- and pro-migratory signalling cascades, respectively, through regulating the Rac1 interactome. In particular, we demonstrate that P-Rex1 stimulates migration through enhancing the interaction between Rac1 and the actin-remodelling protein flightless-1 homologue, to modulate cell contraction in a RhoA-ROCK-independent manner. PMID:26887924

  18. Generation of rac3 Null Mutant Mice: Role of Rac3 in Bcr/Abl-Caused Lymphoblastic Leukemia

    PubMed Central

    Cho, Young Jin; Zhang, Bin; Kaartinen, Vesa; Haataja, Leena; de Curtis, Ivan; Groffen, John; Heisterkamp, Nora

    2005-01-01

    Numerous studies indirectly implicate Rac GTPases in cancer. To investigate if Rac3 contributes to normal or malignant cell function, we generated rac3 null mutants through gene targeting. These mice were viable, fertile, and lacked an obvious external phenotype. This shows Rac3 function is dispensable for embryonic development. Bcr/Abl is a deregulated tyrosine kinase that causes chronic myelogenous leukemia and Ph-positive acute lymphoblastic leukemia in humans. Vav1, a hematopoiesis-specific exchange factor for Rac, was constitutively tyrosine phosphorylated in primary lymphomas from Bcr/Abl P190 transgenic mice, suggesting inappropriate Rac activation. rac3 is expressed in these malignant hematopoietic cells. Using lysates from BCR/ABL transgenic mice that express or lack rac3, we detected the presence of activated Rac3 but not Rac1 or Rac2 in the malignant precursor B-lineage lymphoblasts. In addition, in female P190 BCR/ABL transgenic mice, lack of rac3 was associated with a longer average survival. These data are the first to directly show a stimulatory role for Rac in leukemia in vivo. Moreover, our data suggest that interference with Rac3 activity, for example, by using geranyl-geranyltransferase inhibitors, may provide a positive clinical benefit for patients with Ph-positive acute lymphoblastic leukemia. PMID:15964830

  19. Tiam1 and Rac1 are required for platelet-activating factor-induced endothelial junctional disassembly and increase in vascular permeability.

    PubMed

    Knezevic, Ivana I; Predescu, Sanda A; Neamu, Radu F; Gorovoy, Matvey S; Knezevic, Nebojsa M; Easington, Cordus; Malik, Asrar B; Predescu, Dan N

    2009-02-20

    It is known that platelet-activating factor (PAF) induces severe endothelial barrier leakiness, but the signaling mechanisms remain unclear. Here, using a wide range of biochemical and morphological approaches applied in both mouse models and cultured endothelial cells, we addressed the mechanisms of PAF-induced disruption of interendothelial junctions (IEJs) and of increased endothelial permeability. The formation of interendothelial gaps filled with filopodia and lamellipodia is the cellular event responsible for the disruption of endothelial barrier. We observed that PAF ligation of its receptor induced the activation of the Rho GTPase Rac1. Following PAF exposure, both Rac1 and its guanine nucleotide exchange factor Tiam1 were found associated with a membrane fraction from which they co-immunoprecipitated with PAF receptor. In the same time frame with Tiam1-Rac1 translocation, the junctional proteins ZO-1 and VE-cadherin were relocated from the IEJs, and formation of numerous interendothelial gaps was recorded. Notably, the response was independent of myosin light chain phosphorylation and thus distinct from other mediators, such as histamine and thrombin. The changes in actin status are driven by the PAF-induced localized actin polymerization as a consequence of Rac1 translocation and activation. Tiam1 was required for the activation of Rac1, actin polymerization, relocation of junctional associated proteins, and disruption of IEJs. Thus, PAF-induced IEJ disruption and increased endothelial permeability requires the activation of a Tiam1-Rac1 signaling module, suggesting a novel therapeutic target against increased vascular permeability associated with inflammatory diseases. PMID:19095647

  20. Tiam1 and Rac1 Are Required for Platelet-activating Factor-induced Endothelial Junctional Disassembly and Increase in Vascular Permeability*

    PubMed Central

    Knezevic, Ivana I.; Predescu, Sanda A.; Neamu, Radu F.; Gorovoy, Matvey S.; Knezevic, Nebojsa M.; Easington, Cordus; Malik, Asrar B.; Predescu, Dan N.

    2009-01-01

    It is known that platelet-activating factor (PAF) induces severe endothelial barrier leakiness, but the signaling mechanisms remain unclear. Here, using a wide range of biochemical and morphological approaches applied in both mouse models and cultured endothelial cells, we addressed the mechanisms of PAF-induced disruption of interendothelial junctions (IEJs) and of increased endothelial permeability. The formation of interendothelial gaps filled with filopodia and lamellipodia is the cellular event responsible for the disruption of endothelial barrier. We observed that PAF ligation of its receptor induced the activation of the Rho GTPase Rac1. Following PAF exposure, both Rac1 and its guanine nucleotide exchange factor Tiam1 were found associated with a membrane fraction from which they co-immunoprecipitated with PAF receptor. In the same time frame with Tiam1-Rac1 translocation, the junctional proteins ZO-1 and VE-cadherin were relocated from the IEJs, and formation of numerous interendothelial gaps was recorded. Notably, the response was independent of myosin light chain phosphorylation and thus distinct from other mediators, such as histamine and thrombin. The changes in actin status are driven by the PAF-induced localized actin polymerization as a consequence of Rac1 translocation and activation. Tiam1 was required for the activation of Rac1, actin polymerization, relocation of junctional associated proteins, and disruption of IEJs. Thus, PAF-induced IEJ disruption and increased endothelial permeability requires the activation of a Tiam1-Rac1 signaling module, suggesting a novel therapeutic target against increased vascular permeability associated with inflammatory diseases. PMID:19095647

  1. PIKfyve, MTMR3 and their product PtdIns5P regulate cancer cell migration and invasion through activation of Rac1.

    PubMed

    Oppelt, Angela; Haugsten, Ellen M; Zech, Tobias; Danielsen, Håvard E; Sveen, Anita; Lobert, Viola H; Skotheim, Rolf I; Wesche, Jørgen

    2014-08-01

    Previously, we have shown that the phosphoinositide metabolizing enzymes PIKfyve (phosphoinositide 5-kinase, FYVE finger containing) and MTMR3 (myotubularin-related protein 3), together with their lipid product PtdIns5P, are important for migration of normal human fibroblasts. As these proteins are a kinase and a phosphatase respectively, and thereby considered druggable, we wanted to test their involvement in cancer cell migration and invasion. First, we showed that PIKfyve and MTMR3 are expressed in most cancer cells. Next, we demonstrated that depletion of PIKfyve or MTMR3 resulted in decreased velocity in three different cancer cell lines by using new software for cell tracking. Inhibition of the enzymatic activity of PIKfyve by the inhibitor YM201636 also led to a strong reduction in cell velocity. Mechanistically, we show that PIKfyve and MTMR3 regulate the activation of the Rho family GTPase Rac1. Further experiments also implicated PtdIns5P in the activation of Rac1. The results suggest a model for the activation of Rac1 in cell migration where PIKfyve and MTMR3 produce PtdIns5P on cellular membranes which may then serve to recruit effectors to activate Rac1. Finally, in an invasion assay, we demonstrate that both PIKfyve and MTMR3 are implicated in invasive behaviour of cancer cells. Thus PIKfyve and MTMR3 could represent novel therapeutic targets in metastatic cancer. PMID:24840251

  2. A novel interaction between the SH2 domain of signaling adaptor protein Nck-1 and the upstream regulator of the Rho family GTPase Rac1 engulfment and cell motility 1 (ELMO1) promotes Rac1 activation and cell motility.

    PubMed

    Zhang, Guo; Chen, Xia; Qiu, Fanghua; Zhu, Fengxin; Lei, Wenjing; Nie, Jing

    2014-08-15

    Nck family proteins function as adaptors to couple tyrosine phosphorylation signals to actin cytoskeleton reorganization. Several lines of evidence indicate that Nck family proteins involve in regulating the activity of Rho family GTPases. In the present study, we characterized a novel interaction between Nck-1 with engulfment and cell motility 1 (ELMO1). GST pull-down and co-immunoprecipitation assay demonstrated that the Nck-1-ELMO1 interaction is mediated by the SH2 domain of Nck-1 and the phosphotyrosine residues at position 18, 216, 395, and 511 of ELMO1. A R308K mutant of Nck-1 (in which the SH2 domain was inactive), or a 4YF mutant of ELMO1 lacking these four phosphotyrosine residues, diminished Nck-1-ELMO1 interaction. Conversely, tyrosine phosphatase inhibitor treatment and overexpression of Src family kinase Hck significantly enhanced Nck-1-ELMO1 interaction. Moreover, wild type Nck-1, but not R308K mutant, significantly augmented the interaction between ELMO1 and constitutively active RhoG (RhoG(V12A)), thus promoted Rac1 activation and cell motility. Taken together, the present study characterized a novel Nck-1-ELMO1 interaction and defined a new role for Nck-1 in regulating Rac1 activity. PMID:24928514

  3. Rap1 GTPase Inhibits Tumor Necrosis Factor-α-Induced Choroidal Endothelial Migration via NADPH Oxidase- and NF-κB-Dependent Activation of Rac1.

    PubMed

    Wang, Haibo; Fotheringham, Lori; Wittchen, Erika S; Hartnett, M Elizabeth

    2015-12-01

    Macrophage-derived tumor necrosis factor (TNF)-α has been found in choroidal neovascularization (CNV) surgically removed from patients with age-related macular degeneration. However, the role of TNF-α in CNV development remains unclear. In a murine laser-induced CNV model, compared with un-lasered controls, TNF-α mRNA was increased in retinal pigment epithelial and choroidal tissue, and TNF-α colocalized with lectin-stained migrating choroidal endothelial cells (CECs). Inhibition of TNF-α with a neutralizing antibody reduced CNV volume and reactive oxygen species (ROS) level around CNV. In CECs, pretreatment with the antioxidant apocynin or knockdown of p22phox, a subunit of NADPH oxidase, inhibited TNF-α-induced ROS generation. Apocynin reduced TNF-α-induced NF-κB and Rac1 activation, and inhibited TNF-α-induced CEC migration. TNF-α-induced Rac1 activation and CEC migration were inhibited by NF-κB inhibitor Bay11-7082. Overexpression of Rap1a prevented TNF-α-induced ROS generation and reduced NF-κB and Rac1 activation. Activation of Rap1 by 8-(4-chlorophenylthio)adenosine-2'-O-Me-cAMP prevented TNF-α-induced CEC migration and reduced laser-induced CNV volume, ROS generation, and activation of NF-κB and Rac1. These findings provide evidence that active Rap1a inhibits TNF-α-induced CEC migration by inhibiting NADPH oxidase-dependent NF-κB and Rac1 activation and suggests that Rap1a de-escalates CNV development by interfering with ROS-dependent signaling in several steps of the pathogenic process. PMID:26476350

  4. Activation of RhoA, but Not Rac1, Mediates Early Stages of S1P-Induced Endothelial Barrier Enhancement.

    PubMed

    Zhang, Xun E; Adderley, Shaquria P; Breslin, Jerome W

    2016-01-01

    Compromised endothelial barrier function is a hallmark of inflammation. Rho family GTPases are critical in regulating endothelial barrier function, yet their precise roles, particularly in sphingosine-1-phosphate (S1P)-induced endothelial barrier enhancement, remain elusive. Confluent cultures of human umbilical vein endothelial cells (HUVEC) or human dermal microvascular endothelial cells (HDMEC) were used to model the endothelial barrier. Barrier function was assessed by determining the transendothelial electrical resistance (TER) using an electrical cell-substrate impedance sensor (ECIS). The roles of Rac1 and RhoA were tested in S1P-induced barrier enhancement. The results show that pharmacologic inhibition of Rac1 with Z62954982 failed to block S1P-induced barrier enhancement. Likewise, expression of a dominant negative form of Rac1, or knockdown of native Rac1 with siRNA, failed to block S1P-induced elevations in TER. In contrast, blockade of RhoA with the combination of the inhibitors Rhosin and Y16 significantly reduced S1P-induced increases in TER. Assessment of RhoA activation in real time using a fluorescence resonance energy transfer (FRET) biosensor showed that S1P increased RhoA activation primarily at the edges of cells, near junctions. This was complemented by myosin light chain-2 phosphorylation at cell edges, and increased F-actin and vinculin near intercellular junctions, which could all be blocked with pharmacologic inhibition of RhoA. The results suggest that S1P causes activation of RhoA at the cell periphery, stimulating local activation of the actin cytoskeleton and focal adhesions, and resulting in endothelial barrier enhancement. S1P-induced Rac1 activation, however, does not appear to have a significant role in this process. PMID:27187066

  5. Activation of RhoA, but Not Rac1, Mediates Early Stages of S1P-Induced Endothelial Barrier Enhancement

    PubMed Central

    Zhang, Xun E.; Adderley, Shaquria P.

    2016-01-01

    Compromised endothelial barrier function is a hallmark of inflammation. Rho family GTPases are critical in regulating endothelial barrier function, yet their precise roles, particularly in sphingosine-1-phosphate (S1P)-induced endothelial barrier enhancement, remain elusive. Confluent cultures of human umbilical vein endothelial cells (HUVEC) or human dermal microvascular endothelial cells (HDMEC) were used to model the endothelial barrier. Barrier function was assessed by determining the transendothelial electrical resistance (TER) using an electrical cell-substrate impedance sensor (ECIS). The roles of Rac1 and RhoA were tested in S1P-induced barrier enhancement. The results show that pharmacologic inhibition of Rac1 with Z62954982 failed to block S1P-induced barrier enhancement. Likewise, expression of a dominant negative form of Rac1, or knockdown of native Rac1 with siRNA, failed to block S1P-induced elevations in TER. In contrast, blockade of RhoA with the combination of the inhibitors Rhosin and Y16 significantly reduced S1P-induced increases in TER. Assessment of RhoA activation in real time using a fluorescence resonance energy transfer (FRET) biosensor showed that S1P increased RhoA activation primarily at the edges of cells, near junctions. This was complemented by myosin light chain-2 phosphorylation at cell edges, and increased F-actin and vinculin near intercellular junctions, which could all be blocked with pharmacologic inhibition of RhoA. The results suggest that S1P causes activation of RhoA at the cell periphery, stimulating local activation of the actin cytoskeleton and focal adhesions, and resulting in endothelial barrier enhancement. S1P-induced Rac1 activation, however, does not appear to have a significant role in this process. PMID:27187066

  6. Neuronal Apoptosis Induced by Selective Inhibition of Rac GTPase versus Global Suppression of Rho Family GTPases Is Mediated by Alterations in Distinct Mitogen-activated Protein Kinase Signaling Cascades*

    PubMed Central

    Stankiewicz, Trisha R.; Ramaswami, Sai Anandi; Bouchard, Ron J.; Aktories, Klaus; Linseman, Daniel A.

    2015-01-01

    Rho family GTPases play integral roles in neuronal differentiation and survival. We have shown previously that Clostridium difficile toxin B (ToxB), an inhibitor of RhoA, Rac1, and Cdc42, induces apoptosis of cerebellar granule neurons (CGNs). In this study, we compared the effects of ToxB to a selective inhibitor of the Rac-specific guanine nucleotide exchange factors Tiam1 and Trio (NSC23766). In a manner similar to ToxB, selective inhibition of Rac induces CGN apoptosis associated with enhanced caspase-3 activation and reduced phosphorylation of the Rac effector p21-activated kinase. In contrast to ToxB, caspase inhibitors do not protect CGNs from targeted inhibition of Rac. Also dissimilar to ToxB, selective inhibition of Rac does not inhibit MEK1/2/ERK1/2 or activate JNK/c-Jun. Instead, targeted inhibition of Rac suppresses distinct MEK5/ERK5, p90Rsk, and Akt-dependent signaling cascades known to regulate the localization and expression of the Bcl-2 homology 3 domain-only protein Bad. Adenoviral expression of a constitutively active mutant of MEK5 is sufficient to attenuate neuronal cell death induced by selective inhibition of Rac with NSC23766 but not apoptosis induced by global inhibition of Rho GTPases with ToxB. Collectively, these data demonstrate that global suppression of Rho family GTPases with ToxB causes a loss of MEK1/2/ERK1/2 signaling and activation of JNK/c-Jun, resulting in diminished degradation and enhanced transcription of the Bcl-2 homology 3 domain-only protein Bim. In contrast, selective inhibition of Rac induces CGN apoptosis by repressing unique MEK5/ERK5, p90Rsk, and Akt-dependent prosurvival pathways, ultimately leading to enhanced expression, dephosphorylation, and mitochondrial localization of proapoptotic Bad. PMID:25666619

  7. Neuronal apoptosis induced by selective inhibition of Rac GTPase versus global suppression of Rho family GTPases is mediated by alterations in distinct mitogen-activated protein kinase signaling cascades.

    PubMed

    Stankiewicz, Trisha R; Ramaswami, Sai Anandi; Bouchard, Ron J; Aktories, Klaus; Linseman, Daniel A

    2015-04-10

    Rho family GTPases play integral roles in neuronal differentiation and survival. We have shown previously that Clostridium difficile toxin B (ToxB), an inhibitor of RhoA, Rac1, and Cdc42, induces apoptosis of cerebellar granule neurons (CGNs). In this study, we compared the effects of ToxB to a selective inhibitor of the Rac-specific guanine nucleotide exchange factors Tiam1 and Trio (NSC23766). In a manner similar to ToxB, selective inhibition of Rac induces CGN apoptosis associated with enhanced caspase-3 activation and reduced phosphorylation of the Rac effector p21-activated kinase. In contrast to ToxB, caspase inhibitors do not protect CGNs from targeted inhibition of Rac. Also dissimilar to ToxB, selective inhibition of Rac does not inhibit MEK1/2/ERK1/2 or activate JNK/c-Jun. Instead, targeted inhibition of Rac suppresses distinct MEK5/ERK5, p90Rsk, and Akt-dependent signaling cascades known to regulate the localization and expression of the Bcl-2 homology 3 domain-only protein Bad. Adenoviral expression of a constitutively active mutant of MEK5 is sufficient to attenuate neuronal cell death induced by selective inhibition of Rac with NSC23766 but not apoptosis induced by global inhibition of Rho GTPases with ToxB. Collectively, these data demonstrate that global suppression of Rho family GTPases with ToxB causes a loss of MEK1/2/ERK1/2 signaling and activation of JNK/c-Jun, resulting in diminished degradation and enhanced transcription of the Bcl-2 homology 3 domain-only protein Bim. In contrast, selective inhibition of Rac induces CGN apoptosis by repressing unique MEK5/ERK5, p90Rsk, and Akt-dependent prosurvival pathways, ultimately leading to enhanced expression, dephosphorylation, and mitochondrial localization of proapoptotic Bad. PMID:25666619

  8. Effect of reaction environments on the reactivity of PCB (2-chlorobiphenyl) over activated carbon impregnated with palladized iron.

    PubMed

    Choi, Hyeok; Al-Abed, Souhail R

    2010-07-15

    Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-ClBP) in the RAC system. The results were discussed in close connection to the implementation issue of the RAC system for the remediation of contaminated sites with PCBs. Adsorption event of 2-ClBP onto RAC limited the overall performance under condition with a 2-ClBP/RAC mass ratio of less than 1.0x10(-4) above which dechlorination of 2-ClBP adsorbed to RAC was the reaction rate-determining step. Acidic and basic conditions were harmful to 2-ClBP adsorption and iron stability while neutral pH showed the highest adsorption-promoted dechlorination of 2-ClBP and negligible metal leaching. Coexisting natural organic matter (NOM) slightly inhibited 2-ClBP adsorption onto RAC due to the partial partitioning of 2-ClBP into NOM in the liquid phase while the 2-ClBP absorbed into NOM, which also tended to adsorb onto RAC, was less available for the dechlorination reaction. Common anions slowed down 2-ClBP adsorption but adsorbed 2-ClBP was almost simultaneously dechlorinated. Some exceptions included strong inhibitory effect of carbonate species on 2-ClBP adsorption and severe detrimental effect of sulfite on 2-ClBP dechlorination. Results on treatment of 2-ClBP spiked to actual sediment supernatants implied site-specific reactivity of RAC. PMID:20388583

  9. Dlc1 interaction with non-muscle myosin heavy chain II-A (Myh9) and Rac1 activation

    PubMed Central

    Sabbir, Mohammad G.; Dillon, Rachelle; Mowat, Michael R. A.

    2016-01-01

    ABSTRACT The Deleted in liver cancer 1 (Dlc1) gene codes for a Rho GTPase-activating protein that also acts as a tumour suppressor gene. Several studies have consistently found that overexpression leads to excessive cell elongation, cytoskeleton changes and subsequent cell death. However, none of these studies have been able to satisfactorily explain the Dlc1-induced cell morphological phenotypes and the function of the different Dlc1 isoforms. Therefore, we have studied the interacting proteins associated with the three major Dlc1 transcriptional isoforms using a mass spectrometric approach in Dlc1 overexpressing cells. We have found and validated novel interacting partners in constitutive Dlc1-expressing cells. Our study has shown that Dlc1 interacts with non-muscle myosin heavy chain II-A (Myh9), plectin and spectrin proteins in different multiprotein complexes. Overexpression of Dlc1 led to increased phosphorylation of Myh9 protein and activation of Rac1 GTPase. These data support a role for Dlc1 in induced cell elongation morphology and provide some molecular targets for further analysis of this phenotype. PMID:26977077

  10. Dlc1 interaction with non-muscle myosin heavy chain II-A (Myh9) and Rac1 activation.

    PubMed

    Sabbir, Mohammad G; Dillon, Rachelle; Mowat, Michael R A

    2016-01-01

    The Deleted in liver cancer 1 (Dlc1) gene codes for a Rho GTPase-activating protein that also acts as a tumour suppressor gene. Several studies have consistently found that overexpression leads to excessive cell elongation, cytoskeleton changes and subsequent cell death. However, none of these studies have been able to satisfactorily explain the Dlc1-induced cell morphological phenotypes and the function of the different Dlc1 isoforms. Therefore, we have studied the interacting proteins associated with the three major Dlc1 transcriptional isoforms using a mass spectrometric approach in Dlc1 overexpressing cells. We have found and validated novel interacting partners in constitutive Dlc1-expressing cells. Our study has shown that Dlc1 interacts with non-muscle myosin heavy chain II-A (Myh9), plectin and spectrin proteins in different multiprotein complexes. Overexpression of Dlc1 led to increased phosphorylation of Myh9 protein and activation of Rac1 GTPase. These data support a role for Dlc1 in induced cell elongation morphology and provide some molecular targets for further analysis of this phenotype. PMID:26977077

  11. The Rac1-GEF Tiam1 couples the NMDA receptor to the activity-dependent development of dendritic arbors and spines.

    PubMed

    Tolias, Kimberley F; Bikoff, Jay B; Burette, Alain; Paradis, Suzanne; Harrar, Dana; Tavazoie, Sohail; Weinberg, Richard J; Greenberg, Michael E

    2005-02-17

    NMDA-type glutamate receptors play a critical role in the activity-dependent development and structural remodeling of dendritic arbors and spines. However, the molecular mechanisms that link NMDA receptor activation to changes in dendritic morphology remain unclear. We report that the Rac1-GEF Tiam1 is present in dendrites and spines and is required for their development. Tiam1 interacts with the NMDA receptor and is phosphorylated in a calcium-dependent manner in response to NMDA receptor stimulation. Blockade of Tiam1 function with RNAi and dominant interfering mutants of Tiam1 suggests that Tiam1 mediates effects of the NMDA receptor on dendritic development by inducing Rac1-dependent actin remodeling and protein synthesis. Taken together, these findings define a molecular mechanism by which NMDA receptor signaling controls the growth and morphology of dendritic arbors and spines. PMID:15721239

  12. Cinnamon and Its Metabolite Sodium Benzoate Attenuate the Activation of p21rac and Protect Memory and Learning in an Animal Model of Alzheimer's Disease.

    PubMed

    Modi, Khushbu K; Roy, Avik; Brahmachari, Saurabh; Rangasamy, Suresh B; Pahan, Kalipada

    2015-01-01

    This study underlines the importance of cinnamon, a commonly used natural spice and flavoring material, and its metabolite sodium benzoate (NaB) in attenuating oxidative stress and protecting memory and learning in an animal model of Alzheimer's disease (AD). NaB, but not sodium formate, was found to inhibit LPS-induced production of reactive oxygen species (ROS) in mouse microglial cells. Similarly, NaB also inhibited fibrillar amyloid beta (Aβ)- and 1-methyl-4-phenylpyridinium(+)-induced microglial production of ROS. Although NaB reduced the level of cholesterol in vivo in mice, reversal of the inhibitory effect of NaB on ROS production by mevalonate, and geranylgeranyl pyrophosphate, but not cholesterol, suggests that depletion of intermediates, but not end products, of the mevalonate pathway is involved in the antioxidant effect of NaB. Furthermore, we demonstrate that an inhibitor of p21rac geranylgeranyl protein transferase suppressed the production of ROS and that NaB suppressed the activation of p21rac in microglia. As expected, marked activation of p21rac was observed in the hippocampus of subjects with AD and 5XFAD transgenic (Tg) mouse model of AD. However, oral feeding of cinnamon (Cinnamonum verum) powder and NaB suppressed the activation of p21rac and attenuated oxidative stress in the hippocampus of Tg mice as evident by decreased dihydroethidium (DHE) and nitrotyrosine staining, reduced homocysteine level and increased level of reduced glutathione. This was accompanied by suppression of neuronal apoptosis, inhibition of glial activation, and reduction of Aβ burden in the hippocampus and protection of memory and learning in transgenic mice. Therefore, cinnamon powder may be a promising natural supplement in halting or delaying the progression of AD. PMID:26102198

  13. Cinnamon and Its Metabolite Sodium Benzoate Attenuate the Activation of p21rac and Protect Memory and Learning in an Animal Model of Alzheimer’s Disease

    PubMed Central

    Modi, Khushbu K.; Roy, Avik; Brahmachari, Saurabh; Rangasamy, Suresh B.; Pahan, Kalipada

    2015-01-01

    This study underlines the importance of cinnamon, a commonly used natural spice and flavoring material, and its metabolite sodium benzoate (NaB) in attenuating oxidative stress and protecting memory and learning in an animal model of Alzheimer’s disease (AD). NaB, but not sodium formate, was found to inhibit LPS-induced production of reactive oxygen species (ROS) in mouse microglial cells. Similarly, NaB also inhibited fibrillar amyloid beta (Aβ)- and 1-methyl-4-phenylpyridinium(+)-induced microglial production of ROS. Although NaB reduced the level of cholesterol in vivo in mice, reversal of the inhibitory effect of NaB on ROS production by mevalonate, and geranylgeranyl pyrophosphate, but not cholesterol, suggests that depletion of intermediates, but not end products, of the mevalonate pathway is involved in the antioxidant effect of NaB. Furthermore, we demonstrate that an inhibitor of p21rac geranylgeranyl protein transferase suppressed the production of ROS and that NaB suppressed the activation of p21rac in microglia. As expected, marked activation of p21rac was observed in the hippocampus of subjects with AD and 5XFAD transgenic (Tg) mouse model of AD. However, oral feeding of cinnamon (Cinnamonum verum) powder and NaB suppressed the activation of p21rac and attenuated oxidative stress in the hippocampus of Tg mice as evident by decreased dihydroethidium (DHE) and nitrotyrosine staining, reduced homocysteine level and increased level of reduced glutathione. This was accompanied by suppression of neuronal apoptosis, inhibition of glial activation, and reduction of Aβ burden in the hippocampus and protection of memory and learning in transgenic mice. Therefore, cinnamon powder may be a promising natural supplement in halting or delaying the progression of AD. PMID:26102198

  14. Jak3 Enables Chemokine-Dependent Actin Cytoskeleton Reorganization by Regulating Cofilin and Rac/Rhoa GTPases Activation

    PubMed Central

    Ambriz-Peña, Xochitl; García-Zepeda, Eduardo Alberto; Meza, Isaura; Soldevila, Gloria

    2014-01-01

    We have previously shown that Jak3 is involved in the signaling pathways of CCR7, CCR9 and CXCR4 in murine T lymphocytes and that Jak3−/− lymphocytes display an intrinsic defect in homing to peripheral lymph nodes. However, the molecular mechanism underlying the defective migration observed in Jak3−/− lymphocytes remains elusive. Here, it is demonstrated for the first time, that Jak3 is required for the actin cytoskeleton reorganization in T lymphocytes responding to chemokines. It was found that Jak3 regulates actin polymerization by controlling cofilin inactivation in response to CCL21 and CXCL12. Interestingly, cofilin inactivation was not precluded in PTX- treated cells despite their impaired actin polymerization. Additionally, Jak3 was required for small GTPases Rac1 and RhoA activation, which are indispensable for acquisition of the migratory cell phenotype and the generation of a functional leading edge and uropod, respectively. This defect correlates with data obtained by time-lapse video-microscopy showing an incompetent uropod formation and impaired motility in Jak3-pharmacologically inhibited T lymphocytes. Our data support a new model in which Jak3 and heterotrimeric G proteins can use independent, but complementary, signaling pathways to regulate actin cytoskeleton dynamics during cell migration in response to chemokines. PMID:24498424

  15. Heregulin/ErbB3 Signaling Enhances CXCR4-Driven Rac1 Activation and Breast Cancer Cell Motility via Hypoxia-Inducible Factor 1α.

    PubMed

    Lopez-Haber, Cynthia; Barrio-Real, Laura; Casado-Medrano, Victoria; Kazanietz, Marcelo G

    2016-08-01

    The growth factor heregulin (HRG), a ligand of ErbB3 and ErbB4 receptors, contributes to breast cancer development and the promotion of metastatic disease, and its expression in breast tumors has been associated with poor clinical outcome and resistance to therapy. In this study, we found that breast cancer cells exposed to sustained HRG treatment show markedly enhanced Rac1 activation and migratory activity in response to the CXCR4 ligand SDF-1/CXCL12, effects mediated by P-Rex1, a Rac-guanine nucleotide exchange factor (GEF) aberrantly expressed in breast cancer. Notably, HRG treatment upregulates surface expression levels of CXCR4, a G protein-coupled receptor (GPCR) implicated in breast cancer metastasis and an indicator of poor prognosis in breast cancer patients. A detailed mechanistic analysis revealed that CXCR4 upregulation and sensitization of the Rac response/motility by HRG are mediated by the transcription factor hypoxia-inducible factor 1α (HIF-1α) via ErbB3 and independently of ErbB4. HRG caused prominent induction in the nuclear expression of HIF-1α, which transcriptionally activates the CXCR4 gene via binding to a responsive element located in positions -1376 to -1372 in the CXCR4 promoter, as revealed by mutagenesis analysis and chromatin immunoprecipitation (ChIP). Our results uncovered a novel function for ErbB3 in enhancing breast cancer cell motility and sensitization of the P-Rex1/Rac1 pathway through HIF-1α-mediated transcriptional induction of CXCR4. PMID:27185877

  16. Coevolution of RAC Small GTPases and their Regulators GEF Proteins

    PubMed Central

    Jiménez-Sánchez, Alejandro

    2016-01-01

    RAC proteins are small GTPases involved in important cellular processes in eukaryotes, and their deregulation may contribute to cancer. Activation of RAC proteins is regulated by DOCK and DBL protein families of guanine nucleotide exchange factors (GEFs). Although DOCK and DBL proteins act as GEFs on RAC proteins, DOCK and DBL family members are evolutionarily unrelated. To understand how DBL and DOCK families perform the same function on RAC proteins despite their unrelated primary structure, phylogenetic analyses of the RAC, DBL, and DOCK families were implemented, and interaction patterns that may suggest a coevolutionary process were searched. Interestingly, while RAC and DOCK proteins are very well conserved in humans and among eukaryotes, DBL proteins are highly divergent. Moreover, correlation analyses of the phylogenetic distances of RAC and GEF proteins and covariation analyses between residues in the interacting domains showed significant coevolution rates for both RAC–DOCK and RAC–DBL interactions. PMID:27226705

  17. Growth arrest of lung carcinoma cells (A549) by polyacrylate-anchored peroxovanadate by activating Rac1-NADPH oxidase signalling axis.

    PubMed

    Chatterjee, Nirupama; Anwar, Tarique; Islam, Nashreen S; Ramasarma, T; Ramakrishna, Gayatri

    2016-09-01

    Hydrogen peroxide is often required in sublethal, millimolar concentrations to show its oxidant effects on cells in culture as it is easily destroyed by cellular catalase. Previously, we had shown that diperoxovanadate, a physiologically stable peroxovanadium compound, can substitute H2O2 effectively in peroxidation reactions. We report here that peroxovanadate when anchored to polyacrylic acid (PAPV) becomes a highly potent inhibitor of growth of lung carcinoma cells (A549). The early events associated with PAPV treatment included cytoskeletal modifications, increase in GTPase activity of Rac1, accumulation of the reactive oxygen species, and also increase in phosphorylation of H2AX (γH2AX), a marker of DNA damage. These effects persisted even at 24 h after removal of the compound and culminated in increased levels of p53 and p21 together with growth arrest. The PAPV-mediated growth arrest was significantly abrogated in cells pre-treated with the N-acetylcysteine, Rac1 knocked down by siRNA and DPI an inhibitor of NADPH oxidase. In conclusion, our results show that polyacrylate derivative of peroxovanadate efficiently arrests growth of A549 cancerous cells by activating the axis of Rac1-NADPH oxidase leading to oxidative stress and DNA damage. PMID:27435854

  18. Spatio-temporal co-ordination of RhoA, Rac1 and Cdc42 activation during prototypical edge protrusion and retraction dynamics

    PubMed Central

    Martin, Katrin; Reimann, Andreas; Fritz, Rafael D.; Ryu, Hyunryul; Jeon, Noo Li; Pertz, Olivier

    2016-01-01

    The three canonical Rho GTPases RhoA, Rac1 and Cdc42 co-ordinate cytoskeletal dynamics. Recent studies indicate that all three Rho GTPases are activated at the leading edge of motile fibroblasts, where their activity fluctuates at subminute time and micrometer length scales. Here, we use a microfluidic chip to acutely manipulate fibroblast edge dynamics by applying pulses of platelet-derived growth factor (PDGF) or the Rho kinase inhibitor Y-27632 (which lowers contractility). This induces acute and robust membrane protrusion and retraction events, that exhibit stereotyped cytoskeletal dynamics, allowing us to fairly compare specific morphodynamic states across experiments. Using a novel Cdc42, as well as previously described, second generation RhoA and Rac1 biosensors, we observe distinct spatio-temporal signaling programs that involve all three Rho GTPases, during protrusion/retraction edge dynamics. Our results suggest that Rac1, Cdc42 and RhoA regulate different cytoskeletal and adhesion processes to fine tune the highly plastic edge protrusion/retraction dynamics that power cell motility. PMID:26912264

  19. Effects of aging and oxidation of palladized iron embedded in activated carbon on the dechlorination of 2-chlorobiphenyl

    SciTech Connect

    Hyeok Choi; Souhail R. Al-Abed; Shirish Agarwal

    2009-06-15

    Reactive activated carbon (RAC) impregnated with palladized iron has been developed to effectively treat polychlorinated biphenyls (PCBs) in the environment by coupling adsorption and dechlorination of PCBs. In this study, we addressed the dechlorination reactivity and capacity of RAC toward aqueous 2-chlorobiphenyl (2-ClBP), and its aging and longevity under various oxidizing environments. RAC containing 14.4% Fe and 0.68% Pd used in this study could adsorb 122.6 mg 2-ClBP/g RAC, and dechlorinate 56.5 mg 2-ClBP/g RAC which corresponds to 12% (yield) of its estimated dechlorination capacity. Due to Fe0 oxidation to form oxide passivating layers, Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4} (oxide-water interface) and FeOOH/FeO (oxide-metal interface), RAC reactivity decreased progressively over aging under N{sub 2} < H{sub 2}O + N{sub 2} < H{sub 2}O + O{sub 2} conditions. Considering nanoscale Fe/Pd corrosion chemistry, the decline was quite slow at only 5.6%, 19.5%, and 32.5% over one year, respectively. Dissolved oxygen played a crucial role in enhancing 2-ClBP adsorption but inhibiting its dechlorination. The reactivity change could be explained with the properties of the aged RAC including surface area, Fe0 content, and Fe species. During the aging and oxidation, the RAC showed limited dissolution of Fe and Pd. Finally, implementation issues regarding application of RAC system to contaminated sites are discussed. 25 refs., 6 figs., 1 tab.

  20. Helicobacter pylori-elicited induction in gastric mucosal matrix metalloproteinase-9 (MMP-9) release involves ERK-dependent cPLA2 activation and its recruitment to the membrane-localized Rac1/p38 complex.

    PubMed

    Slomiany, B L; Slomiany, A

    2016-06-01

    Matrix metalloproteinases (MMPs) are a family of endopeptidases implicated in a wide rage of degenerative and inflammatory diseases, including Helicobacter pylori-associated gastritis, and gastric and duodenal ulcer. As gastric mucosal inflammatory responses to H. pylori are characterized by the rise in MMP-9 production, as well as the induction in mitogen-activated protein kinase (MAPK) and Rac1 activation, we investigated the role of Rac1/MAPK in the processes associated with the release of MMP-9. We show that H. pylori LPS-elicited induction in gastric mucosal MMP-9 release is associated with MAPK, ERK and p38 activation, and occurs with the involvement of Rac1 and cytosolic phospholipase A2 (cPLA2). Further, we demonstrate that the LPS-induced MMP-9 release requires ERK-mediated phosphorylation of cPLA2 on Ser(505) that is essential for its membrane localization with Rac1, and that this process necessitates p38 participation. Moreover, we reveal that the activation and membrane translocation of p38 to the Rac1-GTP complex plays a pivotal role in cPLA2-dependent enhancement in MMP-9 release. Hence, our findings provide a strong evidence for the role of ERK/cPLA2 and Rac1/p38/cPLA2 cascade in H. pylori LPS-induced up-regulation in gastric mucosal MMP-9 release. PMID:26886372

  1. Rac1 promotes chondrogenesis by regulating STAT3 signaling pathway.

    PubMed

    Kim, Hyoin; Sonn, Jong Kyung

    2016-09-01

    The small GTPase protein Rac1 is involved in a wide range of biological processes including cell differentiation. Previously, Rac1 was shown to promote chondrogenesis in micromass cultures of limb mesenchyme. However, the pathways mediating Rac1's role in chondrogenesis are not fully understood. This study aimed to explore the molecular mechanisms by which Rac1 regulates chondrogenic differentiation. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) was increased as chondrogenesis proceeded in micromass cultures of chick wing bud mesenchyme. Inhibition of Rac1 with NSC23766, janus kinase 2 (JAK2) with AG490, or STAT3 with stattic inhibited chondrogenesis and reduced phosphorylation of STAT3. Conversely, overexpression of constitutively active Rac1 (Rac L61) increased phosphorylation of STAT3. Rac L61 expression resulted in increased expression of interleukin 6 (IL-6), and treatment with IL-6 increased phosphorylation of STAT3. NSC23766, AG490, and stattic prohibited cell aggregation, whereas expression of Rac L61 increased cell aggregation, which was reduced by stattic treatment. Our studies indicate that Rac1 induces STAT3 activation through expression and action of IL-6. Overexpression of Rac L61 increased expression of bone morphogenic protein 4 (BMP4). BMP4 promoted chondrogenesis, which was inhibited by K02288, an activin receptor-like kinase-2 inhibitor, and increased phosphorylation of p38 MAP kinase. Overexpression of Rac L61 also increased phosphorylation of p38 MAPK, which was reduced by K02288. These results suggest that Rac1 activates STAT3 by expression of IL-6, which in turn increases expression and activity of BMP4, leading to the promotion of chondrogenesis. PMID:27306109

  2. RhoGDI2 is expressed in human trophoblasts and involved in their migration by inhibiting the activation of RAC1.

    PubMed

    Liu, Sishi; Cui, Hong; Li, Qiuling; Zhang, Lijuan; Na, Quan; Liu, Caixia

    2014-04-01

    The invasion of placental trophoblast cells into the maternal decidua is an essential aspect of placental embedment. The process of placentation bears several striking similarities to tumor cell metastasis. However, trophoblastic migration during implantation and placentation is stringently controlled both in space and time. RhoGDI2 belongs to a family of Rho guanosine diphosphate dissociation inhibitors (RhoGDIs), and RhoGDI2 is a metastasis suppressor gene and a marker of aggressive human cancer. We evaluated whether RhoGDI2 has a physiological role in embryo implantation, particularly trophoblast migration. The mRNA and protein expression levels of RhoGDI2 were higher in term placentas compared with first-trimester placentas as detected by real-time PCR and Western blot. Immunohistochemical studies indicated that RhoGDI2 localized to the cytotrophoblast layer and extravillous trophoblast in first-trimester placentas and was distributed in the syncytiotrophoblast layers of term placentas. Overexpression of RhoGDI2 in HTR-8/SVneo cells was associated with reduced RAC1-guanosine triphosphate (GTP) levels and inhibited cell migration. Conversely, small interfering RNA-mediated downregulation of RhoGDI2 resulted in significantly increased RAC1-GTP levels. Altered RhoGDI2 expression had no significant effects on cell proliferation. In conclusion, RhoGDI2 inhibits trophoblast cell migration, and this function may involve suppression of RAC1 activation. PMID:24554735

  3. Differential Tiam1/Rac1 activation in hippocampal and cortical neurons mediates differential spine shrinkage in response to oxygen/glucose deprivation

    PubMed Central

    Blanco-Suárez, Elena; Fiuza, Maria; Liu, Xun; Chakkarapani, Elavazhagan; Hanley, Jonathan G

    2014-01-01

    Distinct neuronal populations show differential sensitivity to global ischemia, with hippocampal CA1 neurons showing greater vulnerability compared to cortical neurons. The mechanisms that underlie differential vulnerability are unclear, and we hypothesize that intrinsic differences in neuronal cell biology are involved. Dendritic spine morphology changes in response to ischemic insults in vivo, but cell type-specific differences and the molecular mechanisms leading to such morphologic changes are unexplored. To directly compare changes in spine size in response to oxygen/glucose deprivation (OGD) in cortical and hippocampal neurons, we used separate and equivalent cultures of each cell type. We show that cortical neurons exhibit significantly greater spine shrinkage compared to hippocampal neurons. Rac1 is a Rho-family GTPase that regulates the actin cytoskeleton and is involved in spine dynamics. We show that Rac1 and the Rac guanine nucleotide exchange factor (GEF) Tiam1 are differentially activated by OGD in hippocampal and cortical neurons. Hippocampal neurons express more Tiam1 than cortical neurons, and reducing Tiam1 expression in hippocampal neurons by shRNA enhances OGD-induced spine shrinkage. Tiam1 knockdown also reduces hippocampal neuronal vulnerability to OGD. This work defines fundamental differences in signalling pathways that regulate spine morphology in distinct neuronal populations that may have a role in the differential vulnerability to ischemia. PMID:25248834

  4. CXCR4 regulates migration of lung alveolar epithelial cells through activation of Rac1 and matrix metalloproteinase-2

    PubMed Central

    Ghosh, Manik C.; Makena, Patrudu S.; Gorantla, Vijay; Sinclair, Scott E.

    2012-01-01

    Restoration of the epithelial barrier following acute lung injury is critical for recovery of lung homeostasis. After injury, alveolar type II epithelial (ATII) cells spread and migrate to cover the denuded surface and, eventually, proliferate and differentiate into type I cells. The chemokine CXCL12, also known as stromal cell-derived factor 1α, has well-recognized roles in organogenesis, hematopoiesis, and immune responses through its binding to the chemokine receptor CXCR4. While CXCL12/CXCR4 signaling is known to be important in immune cell migration, the role of this chemokine-receptor interaction has not been studied in alveolar epithelial repair mechanisms. In this study, we demonstrated that secretion of CXCL12 was increased in the bronchoalveolar lavage of rats ventilated with an injurious tidal volume (25 ml/kg). We also found that CXCL12 secretion was increased by primary rat ATII cells and a mouse alveolar epithelial (MLE12) cell line following scratch wounding and that both types of cells express CXCR4. CXCL12 significantly increased ATII cell migration in a scratch-wound assay. When we treated cells with a specific antagonist for CXCR4, AMD-3100, cell migration was significantly inhibited. Knockdown of CXCR4 by short hairpin RNA (shRNA) caused decreased cell migration compared with cells expressing a nonspecific shRNA. Treatment with AMD-3100 decreased matrix metalloproteinase-14 expression, increased tissue inhibitor of metalloproteinase-3 expression, decreased matrix metalloproteinase-2 activity, and prevented CXCL12-induced Rac1 activation. Similar results were obtained with shRNA knockdown of CXCR4. These findings may help identify a therapeutic target for augmenting epithelial repair following acute lung injury. PMID:22345572

  5. Serine-71 phosphorylation of Rac1 modulates downstream signaling.

    PubMed

    Schwarz, Janett; Proff, Julia; Hävemeier, Anika; Ladwein, Markus; Rottner, Klemens; Barlag, Britta; Pich, Andreas; Tatge, Helma; Just, Ingo; Gerhard, Ralf

    2012-01-01

    The Rho GTPases Rac1 and Cdc42 regulate a variety of cellular functions by signaling to different signal pathways. It is believed that the presence of a specific effector at the location of GTPase activation determines the route of downstream signaling. We previously reported about EGF-induced Ser-71 phosphorylation of Rac1/Cdc42. By using the phosphomimetic S71E-mutants of Rac1 and Cdc42 we investigated the impact of Ser-71 phosphorylation on binding to selected effector proteins. Binding of the constitutively active (Q61L) variants of Rac1 and Cdc42 to their specific interaction partners Sra-1 and N-WASP, respectively, as well as to their common effector protein PAK was abrogated when Ser-71 was exchanged to glutamate as phosphomimetic substitution. Interaction with their common effector proteins IQGAP1/2/3 or MRCK alpha was, however, hardly affected. This ambivalent behaviour was obvious in functional assays. In contrast to Rac1 Q61L, phosphomimetic Rac1 Q61L/S71E was not able to induce increased membrane ruffling. Instead, Rac1 Q61L/S71E allowed filopodia formation, which is in accordance with abrogation of the dominant Sra-1/Wave signalling pathway. In addition, in contrast to Rac1 transfected cells Rac1 S71E failed to activate PAK1/2. On the other hand, Rac1 Q61L/S71E was as effective in activation of NF-kappaB as Rac1 Q61L, illustrating positive signal transduction of phosphorylated Rac1. Together, these data suggest that phosphorylation of Rac1 and Cdc42 at serine-71 represents a reversible mechanism to shift specificity of GTPase/effector coupling, and to preferentially address selected downstream pathways. PMID:22970203

  6. Gnb isoforms control a signaling pathway comprising Rac1, Plcβ2, and Plcβ3 leading to LFA-1 activation and neutrophil arrest in vivo.

    PubMed

    Block, Helena; Stadtmann, Anika; Riad, Daniel; Rossaint, Jan; Sohlbach, Charlotte; Germena, Giulia; Wu, Dianqing; Simon, Scott I; Ley, Klaus; Zarbock, Alexander

    2016-01-21

    Chemokines are required for leukocyte recruitment and appropriate host defense and act through G protein-coupled receptors (GPCRs), which induce downstream signaling leading to integrin activation. Although the α and β subunits of the GPCRs are the first intracellular molecules that transduce signals after ligand binding and are therefore indispensable for downstream signaling, relatively little is known about their contribution to lymphocyte function-associated antigen 1 (LFA-1) activation and leukocyte recruitment. We used knockout mice and short hairpin RNA to knock down guanine nucleotide binding protein (GNB) isoforms (GNB1, GNB2, GNB4, and GNB5) in HL60 cells and primary murine hematopoietic cells. Neutrophil function was assessed by using intravital microscopy, flow chamber assays, and chemotaxis and biochemistry studies. We unexpectedly discovered that all expressed GNB isoforms are required for LFA-1 activation. Their downregulation led to a significant impairment of LFA-1 activation, which was demonstrated in vitro and in vivo. Furthermore, we showed that GPCR activation leads to Ras-related C3 botulinum toxin substrate 1 (Rac1)-dependent activation of both phospholipase C β2 (Plcβ2) and Plcβ3. They act nonredundantly to produce inositol triphosphate-mediated intracellular Ca(2+) flux and LFA-1 activation that support chemokine-induced arrest in vivo. In a complex inflammatory disease model, Plcβ2-, Plcβ3-, or Rac1-deficient mice were protected from lipopolysaccharide-induced lung injury. Taken together, we demonstrated that all Gnb isoforms are required for chemokine-induced downstream signaling, and Rac1, Plcβ2, and Plcβ3 are critically involved in integrin activation and leukocyte arrest. PMID:26468229

  7. The RhoGAP activity of CYK-4/MgcRacGAP functions non-canonically by promoting RhoA activation during cytokinesis

    PubMed Central

    Zhang, Donglei; Glotzer, Michael

    2015-01-01

    Cytokinesis requires activation of the GTPase RhoA. ECT-2, the exchange factor responsible for RhoA activation, is regulated to ensure spatiotemporal control of contractile ring assembly. Centralspindlin, composed of the Rho family GTPase-activating protein (RhoGAP) MgcRacGAP/CYK-4 and the kinesin MKLP1/ZEN-4, is known to activate ECT-2, but the underlying mechanism is not understood. We report that ECT-2-mediated RhoA activation depends on the ability of CYK-4 to localize to the plasma membrane, bind RhoA, and promote GTP hydrolysis by RhoA. Defects resulting from loss of CYK-4 RhoGAP activity can be rescued by activating mutations in ECT-2 or depletion of RGA-3/4, which functions as a conventional RhoGAP for RhoA. Consistent with CYK-4 RhoGAP activity contributing to GEF activation, the catalytic domains of CYK-4 and ECT-2 directly interact. Thus, counterintuitively, CYK-4 RhoGAP activity promotes RhoA activation. We propose that the most active form of the cytokinetic RhoGEF involves complex formation between ECT-2, centralspindlin and RhoA. DOI: http://dx.doi.org/10.7554/eLife.08898.001 PMID:26252513

  8. Conditional deletion of FAK in mice endothelium disrupts lung vascular barrier function due to destabilization of RhoA and Rac1 activities

    PubMed Central

    Schmidt, Tracy Thennes; Tauseef, Mohammad; Yue, Lili; Bonini, Marcelo G.; Gothert, Joachim; Shen, Tang-Long; Guan, Jun-Lin; Predescu, Sanda; Sadikot, Ruxana

    2013-01-01

    Loss of lung-fluid homeostasis is the hallmark of acute lung injury (ALI). Association of catenins and actin cytoskeleton with vascular endothelial (VE)-cadherin is generally considered the main mechanism for stabilizing adherens junctions (AJs), thereby preventing disruption of lung vascular barrier function. The present study identifies endothelial focal adhesion kinase (FAK), a nonreceptor tyrosine kinase that canonically regulates focal adhesion turnover, as a novel AJ-stabilizing mechanism. In wild-type mice, induction of ALI by intraperitoneal administration of lipopolysaccharide or cecal ligation and puncture markedly decreased FAK expression in lungs. Using a mouse model in which FAK was conditionally deleted only in endothelial cells (ECs), we show that loss of EC-FAK mimicked key features of ALI (diffuse lung hemorrhage, increased transvascular albumin influx, edema, and neutrophil accumulation in the lung). EC-FAK deletion disrupted AJs due to impairment of the fine balance between the activities of RhoA and Rac1 GTPases. Deletion of EC-FAK facilitated RhoA's interaction with p115-RhoA guanine exchange factor, leading to activation of RhoA. Activated RhoA antagonized Rac1 activity, destabilizing AJs. Inhibition of Rho kinase, a downstream effector of RhoA, reinstated normal endothelial barrier function in FAK−/− ECs and lung vascular integrity in EC-FAK−/− mice. Our findings demonstrate that EC-FAK plays an essential role in maintaining AJs and thereby lung vascular barrier function by establishing the normal balance between RhoA and Rac1 activities. PMID:23771883

  9. Conditional deletion of FAK in mice endothelium disrupts lung vascular barrier function due to destabilization of RhoA and Rac1 activities.

    PubMed

    Schmidt, Tracy Thennes; Tauseef, Mohammad; Yue, Lili; Bonini, Marcelo G; Gothert, Joachim; Shen, Tang-Long; Guan, Jun-Lin; Predescu, Sanda; Sadikot, Ruxana; Mehta, Dolly

    2013-08-15

    Loss of lung-fluid homeostasis is the hallmark of acute lung injury (ALI). Association of catenins and actin cytoskeleton with vascular endothelial (VE)-cadherin is generally considered the main mechanism for stabilizing adherens junctions (AJs), thereby preventing disruption of lung vascular barrier function. The present study identifies endothelial focal adhesion kinase (FAK), a nonreceptor tyrosine kinase that canonically regulates focal adhesion turnover, as a novel AJ-stabilizing mechanism. In wild-type mice, induction of ALI by intraperitoneal administration of lipopolysaccharide or cecal ligation and puncture markedly decreased FAK expression in lungs. Using a mouse model in which FAK was conditionally deleted only in endothelial cells (ECs), we show that loss of EC-FAK mimicked key features of ALI (diffuse lung hemorrhage, increased transvascular albumin influx, edema, and neutrophil accumulation in the lung). EC-FAK deletion disrupted AJs due to impairment of the fine balance between the activities of RhoA and Rac1 GTPases. Deletion of EC-FAK facilitated RhoA's interaction with p115-RhoA guanine exchange factor, leading to activation of RhoA. Activated RhoA antagonized Rac1 activity, destabilizing AJs. Inhibition of Rho kinase, a downstream effector of RhoA, reinstated normal endothelial barrier function in FAK-/- ECs and lung vascular integrity in EC-FAK-/- mice. Our findings demonstrate that EC-FAK plays an essential role in maintaining AJs and thereby lung vascular barrier function by establishing the normal balance between RhoA and Rac1 activities. PMID:23771883

  10. Crossroads of PI3K and Rac pathways

    PubMed Central

    Campa, Carlo C; Ciraolo, Elisa; Ghigo, Alessandra; Germena, Giulia; Hirsch, Emilio

    2015-01-01

    Rac and PI3Ks are intracellular signal transducers able to regulate multiple signaling pathways fundamental for cell behavior. PI3Ks are lipid kinases that produce phosphorylated lipids which, in turn, transduce extracellular cues within the cell, while Rac is a small G protein that impacts on actin organization. Compelling evidence indicates that in multiple circumstances the 2 signaling pathways appear intermingled. For instance, phosphorylated lipids produced by PI3Ks recruit and activate GEF and GAP proteins, key modulators of Rac function. Conversely, PI3Ks interact with activated Rac, leading to Rac signaling amplification. This review summarizes the molecular mechanisms underlying the cross-talk between Rac and PI3K signaling in 2 different processes, cell migration and ROS production. PMID:25942647

  11. Neuronal filopodium formation induced by the membrane glycoprotein M6a (Gpm6a) is facilitated by coronin-1a, Rac1, and p21-activated kinase 1 (Pak1).

    PubMed

    Alvarez Juliá, Anabel; Frasch, Alberto C; Fuchsova, Beata

    2016-04-01

    Stress-responsive neuronal membrane glycoprotein M6a (Gpm6a) functions in neurite extension, filopodium and spine formation and synaptogenesis. The mechanisms of Gpm6a action in these processes are incompletely understood. Previously, we identified the actin regulator coronin-1a (Coro1a) as a putative Gpm6a interacting partner. Here, we used co-immunoprecipitation assays with the anti-Coro1a antibody to show that Coro1a associates with Gpm6a in rat hippocampal neurons. By immunofluorescence microscopy, we demonstrated that in hippocampal neurons Coro1a localizes in F-actin-enriched regions and some of Coro1a spots co-localize with Gpm6a labeling. Notably, the over-expression of a dominant-negative form of Coro1a as well as its down-regulation by siRNA interfered with Gpm6a-induced filopodium formation. Coro1a is known to regulate the plasma membrane translocation and activation of small GTPase Rac1. We show that Coro1a co-immunoprecipitates with Rac1 together with Gpm6a. Pharmacological inhibition of Rac1 resulted in a significant decrease in filopodium formation by Gpm6a. The same was observed upon the co-expression of Gpm6a with the inactive GDP-bound form of Rac1. In this case, the elevated membrane recruitment of GDP-bound Rac1 was detected as well. Moreover, the kinase activity of the p21-activated kinase 1 (Pak1), a main downstream effector of Rac1 that acts downstream of Coro1a, was required for Gpm6a-induced filopodium formation. Taken together, our results provide evidence that a signaling pathway including Coro1a, Rac1, and Pak1 facilitates Gpm6a-induced filopodium formation. Formation of filopodia by membrane glycoprotein M6a (Gpm6a) requires actin regulator coronin-1a (Coro1a), known to regulate plasma membrane localization and activation of Rac1 and its downstream effector Pak1. Coro1a associates with Gpm6a. Blockage of Coro1a, Rac1, or Pak1 interferes with Gpm6a-induced filopodium formation. Moreover, Gpm6a facilitates Rac1 membrane recruitment

  12. Activated carbon from biomass

    NASA Astrophysics Data System (ADS)

    Manocha, S.; Manocha, L. M.; Joshi, Parth; Patel, Bhavesh; Dangi, Gaurav; Verma, Narendra

    2013-06-01

    Activated carbon are unique and versatile adsorbents having extended surface area, micro porous structure, universal adsorption effect, high adsorption capacity and high degree of surface reactivity. Activated carbons are synthesized from variety of materials. Most commonly used on a commercial scale are cellulosic based precursors such as peat, coal, lignite wood and coconut shell. Variation occurs in precursors in terms of structure and carbon content. Coir having very low bulk density and porous structure is found to be one of the valuable raw materials for the production of highly porous activated carbon and other important factor is its high carbon content. Exploration of good low cost and non conventional adsorbent may contribute to the sustainability of the environment and offer promising benefits for the commercial purpose in future. Carbonization of biomass was carried out in a horizontal muffle furnace. Both carbonization and activation were performed in inert nitrogen atmosphere in one step to enhance the surface area and to develop interconnecting porosity. The types of biomass as well as the activation conditions determine the properties and the yield of activated carbon. Activated carbon produced from biomass is cost effective as it is easily available as a waste biomass. Activated carbon produced by combination of chemical and physical activation has higher surface area of 2442 m2/gm compared to that produced by physical activation (1365 m2/gm).

  13. Rac1 expression in epithelial ovarian cancer: effect on cell EMT and clinical outcome.

    PubMed

    Leng, Ruobing; Liao, Gang; Wang, Haixia; Kuang, Jun; Tang, Liangdan

    2015-02-01

    Ras-related C3 botulinum toxin substrate 1 (rac1) has been implicated in tumor epithelial-mesenchymal transition (EMT); however, limited information is available regarding the role of rac1 in epithelial ovarian cancer (EOC). This study aimed to evaluate the correlation of rac1 expression with EMT and EOC prognosis. Rac1 protein levels of 150 EOC specimens were evaluated by immunohistochemical staining. Survival analysis was performed to determine the correlation between rac1 expression and survival. Cellular and molecular changes were also examined after rac1 in ovarian cancer cells was silenced in vitro and in vivo. The mechanism of rac1 on EMT was investigated by Western blot analysis. Rac1 was highly expressed in EOC. Rac1 overexpression was closely associated with advanced stage based on International Federation of Gynecology and Obstetrics, poor grade, serum Ca-125, and residual tumor size. Survival analyses demonstrated that patients with high rac1 expression levels were more susceptible to early tumor recurrence with very poor prognosis. This study revealed that rac1 downregulation decreased cell EMT and proliferation capability in vitro and in vivo. Rac1 expression possibly altered cell EMT by interacting with p21-activated kinase 1 and p38 mitogen-activated protein kinase signaling pathways. The present study showed that rac1 overexpression is associated with cell EMT and poor EOC prognosis. Rac1 possibly plays an important role in predicting EOC metastasis. PMID:25585684

  14. New alternative splicing BCR/ABL-OOF shows an oncogenic role by lack of inhibition of BCR GTPase activity and an increased of persistence of Rac activation in chronic myeloid leukemia.

    PubMed

    Panuzzo, Cristina; Volpe, Gisella; Cibrario Rocchietti, Elisa; Casnici, Claudia; Crotta, Katia; Crivellaro, Sabrina; Carrà, Giovanna; Lorenzatti, Roberta; Peracino, Barbara; Torti, Davide; Morotti, Alessandro; Camacho-Leal, Maria Pilar; Defilippi, Paola; Marelli, Ornella; Saglio, Giuseppe

    2015-01-01

    In Chronic Myeloid Leukemia 80% of patients present alternative splice variants involving BCR exons 1, 13 or 14 and ABL exon 4, with a consequent impairment in the reading frame of the ABL gene. Therefore BCR/ABL fusion proteins (BCR/ABL-OOF) are characterized by an in-frame BCR portion followed by an amino acids sequence arising from the out of frame (OOF) reading of the ABL gene. The product of this new transcript contains the characteristic BCR domains while lacking the COOH-terminal Rho GTPase GAP domain. The present work aims to characterize the protein functionality in terms of cytoskeleton (re-)modelling, adhesion and activation of canonical oncogenic signalling pathways. Here, we show that BCR/ABL-OOF has a peculiar endosomal localization which affects EGF receptor activation and turnover. Moreover, we demonstrate that BCR/ABL-OOF expression leads to aberrant cellular adhesion due to the activation of Rac GTPase, increase in cellular proliferation, migration and survival. When overexpressed in a BCR/ABL positive cell line, BCR/ABL-OOF induces hyperactivation of Rac signaling axis offering a therapeutic window for Rac-targeted therapy. Our data support a critical role of BCR/ABL-OOF in leukemogenesis and identify a subset of patients that may benefit from Rac-targeted therapies. PMID:26682280

  15. A genetically-encoded photoactivatable Rac controls the motility of living cells

    PubMed Central

    Wu, Yi I.; Frey, Daniel; Lungu, Oana I.; Jaehrig, Angelika; Schlichting, Ilme; Kuhlman, Brian; Hahn, Klaus M.

    2009-01-01

    The precise spatio-temporal dynamics of protein activity are often critical in determining cell behaviour, yet for most proteins they remain poorly understood; it remains difficult to manipulate protein activity at precise times and places within living cells. Protein activity has been controlled by light, through protein derivatization with photocleavable moieties1 or using photoreactive small molecule ligands2. However, this requires use of toxic UV wavelengths, activation is irreversible, and/or cell loading is accomplished via disruption of the cell membrane (i.e. through microinjection). We have developed a new approach to produce genetically-encoded photo-activatable derivatives of Rac1, a key GTPase regulating actin cytoskeletal dynamics3,4. Rac1 mutants were fused to the photoreactive LOV (light oxygen voltage) domain from phototropin5,6, sterically blocking Rac1 interactions until irradiation unwound a helix linking LOV to Rac1. Photoactivatable Rac1 (PA-Rac1) could be reversibly and repeatedly activated using 458 or 473 nm light to generate precisely localized cell protrusions and ruffling. Localized Rac activation or inactivation was sufficient to produce cell motility and control the direction of cell movement. Myosin was involved in Rac control of directionality but not in Rac-induced protrusion, while PAK was required for Rac-induced protrusion. PA-Rac1 was used to elucidate Rac regulation of RhoA in cell motility. Rac and Rho coordinate cytoskeletal behaviours with seconds and submicron precision7,8. Their mutual regulation remains controversial9, with data indicating that Rac inhibits and/or activates Rho10,11. Rac was shown to inhibit RhoA in living cells, with inhibition modulated at protrusions and ruffles. A PA-Rac crystal structure and modelling revealed LOV-Rac interactions that will facilitate extension of this photoactivation approach to other proteins. PMID:19693014

  16. Central role of the exchange factor GEF-H1 in TNF-α–induced sequential activation of Rac, ADAM17/TACE, and RhoA in tubular epithelial cells

    PubMed Central

    Waheed, Faiza; Dan, Qinghong; Amoozadeh, Yasaman; Zhang, Yuqian; Tanimura, Susumu; Speight, Pam; Kapus, András; Szászi, Katalin

    2013-01-01

    Transactivation of the epidermal growth factor receptor (EGFR) by tumor necrosis factor-α (TNF-α) is a key step in mediating RhoA activation and cytoskeleton and junction remodeling in the tubular epithelium. In this study we explore the mechanisms underlying TNF-α–induced EGFR activation. We show that TNF-α stimulates the TNF-α convertase enzyme (TACE/a disintegrin and metalloproteinase-17), leading to activation of the EGFR/ERK pathway. TACE activation requires the mitogen-activated protein kinase p38, which is activated through the small GTPase Rac. TNF-α stimulates both Rac and RhoA through the guanine nucleotide exchange factor (GEF)-H1 but by different mechanisms. EGFR- and ERK-dependent phosphorylation at the T678 site of GEF-H1 is a prerequisite for RhoA activation only, whereas both Rac and RhoA activation require GEF-H1 phosphorylation on S885. Of interest, GEF-H1-mediated Rac activation is upstream from the TACE/EGFR/ERK pathway and regulates T678 phosphorylation. We also show that TNF-α enhances epithelial wound healing through TACE, ERK, and GEF-H1. Taken together, our findings can explain the mechanisms leading to hierarchical activation of Rac and RhoA by TNF-α through a single GEF. This mechanism could coordinate GEF functions and fine-tune Rac and RhoA activation in epithelial cells, thereby promoting complex functions such as sheet migration. PMID:23389627

  17. Inhibition of Rac1 reduces store overload-induced calcium release and protects against ventricular arrhythmia.

    PubMed

    Zhang, Lili; Lu, Xiangru; Gui, Le; Wu, Yan; Sims, Stephen M; Wang, Guoping; Feng, Qingping

    2016-08-01

    Rac1 is a small GTPase and plays key roles in multiple cellular processes including the production of reactive oxygen species (ROS). However, whether Rac1 activation during myocardial ischaemia and reperfusion (I/R) contributes to arrhythmogenesis is not fully understood. We aimed to study the effects of Rac1 inhibition on store overload-induced Ca(2+) release (SOICR) and ventricular arrhythmia during myocardial I/R. Adult Rac1(f/f) and cardiac-specific Rac1 knockdown (Rac1(ckd) ) mice were subjected to myocardial I/R and their electrocardiograms (ECGs) were monitored for ventricular arrhythmia. Myocardial Rac1 activity was increased and ventricular arrhythmia was induced during I/R in Rac1(f/f) mice. Remarkably, I/R-induced ventricular arrhythmia was significantly decreased in Rac1(ckd) compared to Rac1(f/f) mice. Furthermore, treatment with Rac1 inhibitor NSC23766 decreased I/R-induced ventricular arrhythmia. Ca(2+) imaging analysis showed that in response to a 6 mM external Ca(2+) concentration challenge, SOICR was induced with characteristic spontaneous intracellular Ca(2+) waves in Rac1(f/f) cardiomyocytes. Notably, SOICR was diminished by pharmacological and genetic inhibition of Rac1 in adult cardiomyocytes. Moreover, I/R-induced ROS production and ryanodine receptor 2 (RyR2) oxidation were significantly inhibited in the myocardium of Rac1(ckd) mice. We conclude that Rac1 activation induces ventricular arrhythmia during myocardial I/R. Inhibition of Rac1 suppresses SOICR and protects against ventricular arrhythmia. Blockade of Rac1 activation may represent a new paradigm for the treatment of cardiac arrhythmia in ischaemic heart disease. PMID:27222313

  18. CD81 controls immunity to Listeria infection through rac-dependent inhibition of proinflammatory mediator release and activation of cytotoxic T cells.

    PubMed

    Martínez del Hoyo, Gloria; Ramírez-Huesca, Marta; Levy, Shoshana; Boucheix, Claude; Rubinstein, Eric; Minguito de la Escalera, María; González-Cintado, Leticia; Ardavín, Carlos; Veiga, Esteban; Yáñez-Mó, María; Sánchez-Madrid, Francisco

    2015-06-15

    Despite recent evidence on the involvement of CD81 in pathogen binding and Ag presentation by dendritic cells (DCs), the molecular mechanism of how CD81 regulates immunity during infection remains to be elucidated. To investigate the role of CD81 in the regulation of defense mechanisms against microbial infections, we have used the Listeria monocytogenes infection model to explore the impact of CD81 deficiency in the innate and adaptive immune response against this pathogenic bacteria. We show that CD81(-/-) mice are less susceptible than wild-type mice to systemic Listeria infection, which correlates with increased numbers of inflammatory monocytes and DCs in CD81(-/-) spleens, the main subsets controlling early bacterial burden. Additionally, our data reveal that CD81 inhibits Rac/STAT-1 activation, leading to a negative regulation of the production of TNF-α and NO by inflammatory DCs and the activation of cytotoxic T cells by splenic CD8α(+) DCs. In conclusion, this study demonstrates that CD81-Rac interaction exerts an important regulatory role on the innate and adaptive immunity against bacterial infection and suggests a role for CD81 in the development of novel therapeutic targets during infectious diseases. PMID:25972472

  19. Loss of beta1-integrin enhances TGF-beta1-induced collagen expression in epithelial cells via increased alphavbeta3-integrin and Rac1 activity.

    PubMed

    Hayashida, Tomoko; Jones, Jonathan C R; Lee, Carrie K; Schnaper, H William

    2010-10-01

    Transforming growth factor β (TGF-β) promotes tissue fibrosis via the receptor-specific Smad pathway and non-canonical pathways. We recently reported that TGF-β1-stimulated collagen expression by cultured kidney cells requires integrin-dependent activation of focal adhesion kinase (FAK) and consequent ERK MAP kinase activity leading to Smad3 linker region phosphorylation. Here, we defined a role for αvβ3-integrin in this non-canonical pathway. A human kidney tubular cell line in which β1-integrin was knocked down (β1-k/d) demonstrated enhanced type I collagen mRNA expression and promoter activity. A second shRNA to either αv-integrin or β3-integrin, but not to another αv-binding partner, β6-integrin, abrogated the enhanced COL1A2 promoter activity in β1-k/d cells. Although αvβ3-integrin surface expression levels were not different, αvβ3-integrins colocalized with sites of focal adhesion significantly more in β1-k/d cells, and activated αvβ3-integrin was detected only in β1-k/d cells. Further, the collagen response was decreased by a function-blocking antibody or a peptide inhibitor of αvβ3-integrin. In cells lacking αvβ3-integrin, the responses were attenuated, whereas the response was enhanced in αvβ3-overexpressing cells. Rac1 and ERK, previously defined mediators for this non-canonical pathway, showed increased activities in β1-k/d cells. Finally, inhibition of αvβ3-integrin decreased Rac1 activity and COL1A2 promoter activity in β1-k/d cells. Together, our results indicate that decreasing β1 chain causes αvβ3-integrin to become functionally dominant and promotes renal cell fibrogenesis via Rac1-mediated ERK activity. PMID:20650890

  20. Activated carbon material

    DOEpatents

    Evans, A. Gary

    1978-01-01

    Activated carbon particles for use as iodine trapping material are impregnated with a mixture of selected iodine and potassium compounds to improve the iodine retention properties of the carbon. The I/K ratio is maintained at less than about 1 and the pH is maintained at above about 8.0. The iodine retention of activated carbon previously treated with or coimpregnated with triethylenediamine can also be improved by this technique. Suitable flame retardants can be added to raise the ignition temperature of the carbon to acceptable standards.

  1. CD81 is essential for the formation of membrane protrusions and regulates Rac1-activation in adhesion-dependent immune cell migration.

    PubMed

    Quast, Thomas; Eppler, Felix; Semmling, Verena; Schild, Cora; Homsi, Yahya; Levy, Shoshana; Lang, Thorsten; Kurts, Christian; Kolanus, Waldemar

    2011-08-18

    CD81 (TAPA-1) is a member of the widely expressed and evolutionary conserved tetraspanin family that forms complexes with a variety of other cell surface receptors and facilitates hepatitis C virus entry. Here, we show that CD81 is specifically required for the formation of lamellipodia in migrating dendritic cells (DCs). Mouse CD81(-/-) DCs, or murine and human CD81 RNA interference knockdown DCs lacked the ability to form actin protrusions, thereby impairing their motility dramatically. Moreover, we observed a selective loss of Rac1 activity in the absence of CD81, the latter of which is exclusively required for integrin-dependent migration on 2-dimensional substrates. Neither integrin affinity for substrate nor the size of basal integrin clusters was affected by CD81 deficiency in adherent DCs. However, the use of total internal reflection fluorescence microscopy revealed an accumulation of integrin clusters above the basal layer in CD81 knockdown cells. Furthermore, β1- or β2-integrins, actin, and Rac are strongly colocalized at the leading edge of DCs, but the very fronts of these cells protrude CD81-containing membranes that project outward from the actin-integrin area. Taken together, these data suggest a thus far unappreciated role for CD81 in the mobilization of preformed integrin clusters into the leading edge of migratory DCs on 2-dimensional surfaces. PMID:21677313

  2. Overexpression of Rac1 in leukemia patients and its role in leukemia cell migration and growth

    SciTech Connect

    Wang, Jiying; Rao, Qing; Wang, Min; Wei, Hui; Xing, Haiyan; Liu, Hang; Wang, Yanzhong; Tang, Kejing; Peng, Leiwen; Tian, Zheng; Wang, Jianxiang

    2009-09-04

    Rac1 belongs to the Rho family that act as critical mediators of signaling pathways controlling cell migration and proliferation and contributes to the interactions of hematopoietic stem cells with their microenvironment. Alteration of Rac1 might result in unbalanced interactions and ultimately lead to leukemogenesis. In this study, we analyze the expression of Rac1 protein in leukemia patients and determine its role in the abnormal behaviours of leukemic cells. Rac1 protein is overexpressed in primary acute myeloid leukemia cells as compared to normal bone marrow mononuclear cells. siRNA-mediated silencing of Rac1 in leukemia cell lines induced inhibition of cell migration, proliferation, and colony formation. Additionally, blocking Rac1 activity by an inhibitor of Rac1-GTPase, NSC23766, suppressed cell migration and growth. We conclude that overexpression of Rac1 contributes to the accelerated migration and high proliferation potential of leukemia cells, which could be implicated in leukemia development and progression.

  3. Proteomic analysis of Rac1 signaling regulation by guanine nucleotide exchange factors.

    PubMed

    Marei, Hadir; Carpy, Alejandro; Macek, Boris; Malliri, Angeliki

    2016-08-01

    The small GTPase Rac1 is implicated in various cellular processes that are essential for normal cell function. Deregulation of Rac1 signaling has also been linked to a number of diseases, including cancer. The diversity of Rac1 functioning in cells is mainly attributed to its ability to bind to a multitude of downstream effectors following activation by Guanine nucleotide Exchange Factors (GEFs). Despite the identification of a large number of Rac1 binding partners, factors influencing downstream specificity are poorly defined, thus hindering the detailed understanding of both Rac1's normal and pathological functions. In a recent study, we demonstrated a role for 2 Rac-specific GEFs, Tiam1 and P-Rex1, in mediating Rac1 anti- versus pro-migratory effects, respectively. Importantly, via conducting a quantitative proteomic screen, we identified distinct changes in the Rac1 interactome following activation by either GEF, indicating that these opposing effects are mediated through GEF modulation of the Rac1 interactome. Here, we present the full list of identified Rac1 interactors together with functional annotation of the differentially regulated Rac1 binding partners. In light of this data, we also provide additional insights into known and novel signaling cascades that might account for the GEF-mediated Rac1-driven cellular effects. PMID:27152953

  4. Proteomic analysis of Rac1 signaling regulation by guanine nucleotide exchange factors

    PubMed Central

    Marei, Hadir; Carpy, Alejandro; Macek, Boris; Malliri, Angeliki

    2016-01-01

    ABSTRACT The small GTPase Rac1 is implicated in various cellular processes that are essential for normal cell function. Deregulation of Rac1 signaling has also been linked to a number of diseases, including cancer. The diversity of Rac1 functioning in cells is mainly attributed to its ability to bind to a multitude of downstream effectors following activation by Guanine nucleotide Exchange Factors (GEFs). Despite the identification of a large number of Rac1 binding partners, factors influencing downstream specificity are poorly defined, thus hindering the detailed understanding of both Rac1's normal and pathological functions. In a recent study, we demonstrated a role for 2 Rac-specific GEFs, Tiam1 and P-Rex1, in mediating Rac1 anti- versus pro-migratory effects, respectively. Importantly, via conducting a quantitative proteomic screen, we identified distinct changes in the Rac1 interactome following activation by either GEF, indicating that these opposing effects are mediated through GEF modulation of the Rac1 interactome. Here, we present the full list of identified Rac1 interactors together with functional annotation of the differentially regulated Rac1 binding partners. In light of this data, we also provide additional insights into known and novel signaling cascades that might account for the GEF-mediated Rac1-driven cellular effects. PMID:27152953

  5. Simvastatin induces the apoptosis of normal vascular smooth muscle through the disruption of actin integrity via the impairment of RhoA/Rac-1 activity.

    PubMed

    Kang, Seojin; Kim, Keunyoung; Noh, Ji-Yoon; Jung, Yeryeon; Bae, Ok-Nam; Lim, Kyung-Min; Chung, Jin-Ho

    2016-08-30

    Statins, lipid-lowering agents for the prevention of atherosclerosis and fatal coronary heart diseases, have pleiotropic modalities on the function and physiology of vascular smooth muscle that include anti-contractile and pro-apoptotic effects. These effects were suggested to stem from the inhibition of small GTPase Rho A, but they are largely regarded as distinct and unrelated. Recently, we discovered that simvastatin causes both contractile dysfunction and apoptosis of vascular smooth muscle cells (VSMCs), reflecting that they may be closely related, yet their connecting link remains unexplained. Here, we elaborated the mechanism underlying simvastatin-induced apoptosis of normal VSMCs in connection with contractile dysfunction. Repeated oral administration of simvastatin to rats in vivo resulted in contractile dysfunction and apoptosis of vascular smooth muscle, of which pattern was well reproduced in rat VSMCs in vitro. Of note, contractile dysfunction and apoptosis occurred in concerted manners both in vivo and in vitro in the aspects of time course and dose of exposure. In rat VSMCs, simvastatin impaired the activation of small GTPases, RhoA along with Rac-1, which resulted in the disruption of actin integrity, a pivotal factor both for the generation of contractile force and survival of VSMCs. In line with the disruption of actin integrity, Bmf, a pro-apoptotic factor bound to intact actin, dissociated and translocated into mitochondria, which corresponded well with the dissipation of mitochondrial membrane potential, caspase-3 activation and ultimately apoptosis. These events were all rescued by an actin stabilisation agent, jasplakinolide as well as geranylgeraniol, indicating that damages of the actin integrity from disrupted activation of RhoA/Rac-1 lies at the center of simvastatin-induced contractile dysfunction and apoptosis in vascular smooth muscle. PMID:27306926

  6. Roles of Rac1 and Rac3 GTPases during the development of cortical and hippocampal GABAergic interneurons

    PubMed Central

    de Curtis, Ivan

    2014-01-01

    Rac GTPases are regulators of the cytoskeleton that play an important role in several aspects of neuronal and brain development. Two distinct Rac GTPases are expressed in the developing nervous system, the widely expressed Rac1 and the neural-specific Rac3 proteins. Recent experimental evidence supports a central role of these two Rac proteins in the development of inhibitory GABAergic interneurons, important modulatory elements of the brain circuitry. The combined inactivation of the genes for the two Rac proteins has profound effects on distinct aspects of interneuron development, and has highlighted a synergistic contribution of the two proteins to the postmitotic maturation of specific populations of cortical and hippocampal interneurons. Rac function is modulated by different types of regulators, and can influence the activity of specific effectors. Some of these proteins have been associated to the development and maturation of interneurons. Cortical interneuron dysfunction is implicated in several neurological and psychiatric diseases characterized by cognitive impairment. Therefore the description of the cellular processes regulated by the Rac GTPases, and the identification of the molecular networks underlying these processes during interneuron development is relevant to the understanding of the role of GABAergic interneurons in cognitive functions. PMID:25309333

  7. PtdIns(3,4,5)P3-dependent Rac Exchanger 1 (PREX1) Rac-Guanine Nucleotide Exchange Factor (GEF) Activity Promotes Breast Cancer Cell Proliferation and Tumor Growth via Activation of Extracellular Signal-regulated Kinase 1/2 (ERK1/2) Signaling.

    PubMed

    Liu, Heng-Jia; Ooms, Lisa M; Srijakotre, Nuthasuda; Man, Joey; Vieusseux, Jessica; Waters, JoAnne E; Feng, Yue; Bailey, Charles G; Rasko, John E J; Price, John T; Mitchell, Christina A

    2016-08-12

    PtdIns(3,4,5)P3-dependent Rac exchanger 1 (PREX1) is a Rac-guanine nucleotide exchange factor (GEF) overexpressed in a significant proportion of human breast cancers that integrates signals from upstream ErbB2/3 and CXCR4 membrane surface receptors. However, the PREX1 domains that facilitate its oncogenic activity and downstream signaling are not completely understood. We identify that ERK1/2 MAPK acts downstream of PREX1 and contributes to PREX1-mediated anchorage-independent cell growth. PREX1 overexpression increased but its shRNA knockdown decreased ERK1/2 phosphorylation in response to EGF/IGF-1 stimulation, resulting in induction of the cell cycle regulators cyclin D1 and p21(WAF1/CIP1) PREX1-mediated ERK1/2 phosphorylation, anchorage-independent cell growth, and cell migration were suppressed by inhibition of MEK1/2/ERK1/2 signaling. PREX1 overexpression reduced staurosporine-induced apoptosis whereas its shRNA knockdown promoted apoptosis in response to staurosporine or the anti-estrogen drug tamoxifen. Expression of wild-type but not GEF-inactive PREX1 increased anchorage-independent cell growth. In addition, mouse xenograft studies revealed that expression of wild-type but not GEF-dead PREX1 resulted in the formation of larger tumors that displayed increased phosphorylation of ERK1/2 but not AKT. The impaired anchorage-independent cell growth, apoptosis, and ERK1/2 signaling observed in stable PREX1 knockdown cells was restored by expression of wild-type but not GEF-dead-PREX1. Therefore, PREX1-Rac-GEF activity is critical for PREX1-dependent anchorage-independent cell growth and xenograft tumor growth and may represent a possible therapeutic target for breast cancers that exhibit PREX1 overexpression. PMID:27358402

  8. Optogenetics: optical control of a photoactivatable Rac in living cells.

    PubMed

    Yin, Taofei; Wu, Yi I

    2015-01-01

    Recent developments in optogenetics have extended optical control of signaling to intracellular proteins, including Rac, a small G protein in the Rho family. A blue light-sensing LOV (light, oxygen, or voltage) domain derived from Avena sativa (oat) phototropin was fused to the N-terminus of a constitutively active mutant of Rac, via an α-helix (Jα) that is conserved among plant phototropins. The fused LOV domain occluded binding of downstream effectors to Rac in the dark. Exposure to blue light caused a conformational change of the LOV domain and unwinding of the Jα helix, relieving steric inhibition. The LOV domain incorporates a flavin as the photon-absorbing cofactor and can be activated by light in a reversible and repeatable fashion. In cultured cells, global illumination with blue light rapidly activated Rac and led to cell spreading and membrane ruffling. Localized and pulsed illumination generated a gradient of Rac activity and induced directional migration. In this chapter, we will describe the techniques in detail and present some examples of applications of using photoactivatable Rac (PA-Rac) in living cells. PMID:25391805

  9. Rac1 Regulates Endometrial Secretory Function to Control Placental Development.

    PubMed

    Davila, Juanmahel; Laws, Mary J; Kannan, Athilakshmi; Li, Quanxi; Taylor, Robert N; Bagchi, Milan K; Bagchi, Indrani C

    2015-08-01

    During placenta development, a succession of complex molecular and cellular interactions between the maternal endometrium and the developing embryo ensures reproductive success. The precise mechanisms regulating this maternal-fetal crosstalk remain unknown. Our study revealed that the expression of Rac1, a member of the Rho family of GTPases, is markedly elevated in mouse decidua on days 7 and 8 of gestation. To investigate its function in the uterus, we created mice bearing a conditional deletion of the Rac1 gene in uterine stromal cells. Ablation of Rac1 did not affect the formation of the decidua but led to fetal loss in mid gestation accompanied by extensive hemorrhage. To gain insights into the molecular pathways affected by the loss of Rac1, we performed gene expression profiling which revealed that Rac1 signaling regulates the expression of Rab27b, another GTPase that plays a key role in targeting vesicular trafficking. Consequently, the Rac1-null decidual cells failed to secrete vascular endothelial growth factor A, which is a critical regulator of decidual angiogenesis, and insulin-like growth factor binding protein 4, which regulates the bioavailability of insulin-like growth factors that promote proliferation and differentiation of trophoblast cell lineages in the ectoplacental cone. The lack of secretion of these key factors by Rac1-null decidua gave rise to impaired angiogenesis and dysregulated proliferation of trophoblast cells, which in turn results in overexpansion of the trophoblast giant cell lineage and disorganized placenta development. Further experiments revealed that RAC1, the human ortholog of Rac1, regulates the secretory activity of human endometrial stromal cells during decidualization, supporting the concept that this signaling G protein plays a central and conserved role in controlling endometrial secretory function. This study provides unique insights into the molecular mechanisms regulating endometrial secretions that mediate stromal

  10. Rac1 Regulates Endometrial Secretory Function to Control Placental Development

    PubMed Central

    Davila, Juanmahel; Laws, Mary J.; Kannan, Athilakshmi; Li, Quanxi; Taylor, Robert N.; Bagchi, Milan K.; Bagchi, Indrani C.

    2015-01-01

    During placenta development, a succession of complex molecular and cellular interactions between the maternal endometrium and the developing embryo ensures reproductive success. The precise mechanisms regulating this maternal-fetal crosstalk remain unknown. Our study revealed that the expression of Rac1, a member of the Rho family of GTPases, is markedly elevated in mouse decidua on days 7 and 8 of gestation. To investigate its function in the uterus, we created mice bearing a conditional deletion of the Rac1 gene in uterine stromal cells. Ablation of Rac1 did not affect the formation of the decidua but led to fetal loss in mid gestation accompanied by extensive hemorrhage. To gain insights into the molecular pathways affected by the loss of Rac1, we performed gene expression profiling which revealed that Rac1 signaling regulates the expression of Rab27b, another GTPase that plays a key role in targeting vesicular trafficking. Consequently, the Rac1-null decidual cells failed to secrete vascular endothelial growth factor A, which is a critical regulator of decidual angiogenesis, and insulin-like growth factor binding protein 4, which regulates the bioavailability of insulin-like growth factors that promote proliferation and differentiation of trophoblast cell lineages in the ectoplacental cone. The lack of secretion of these key factors by Rac1-null decidua gave rise to impaired angiogenesis and dysregulated proliferation of trophoblast cells, which in turn results in overexpansion of the trophoblast giant cell lineage and disorganized placenta development. Further experiments revealed that RAC1, the human ortholog of Rac1, regulates the secretory activity of human endometrial stromal cells during decidualization, supporting the concept that this signaling G protein plays a central and conserved role in controlling endometrial secretory function. This study provides unique insights into the molecular mechanisms regulating endometrial secretions that mediate stromal

  11. New insights into the dimerization of small GTPase Rac/ROP guanine nucleotide exchange factors in rice

    PubMed Central

    Akamatsu, Akira; Uno, Kazumi; Kato, Midori; Wong, Hann Ling; Shimamoto, Ko; Kawano, Yoji

    2015-01-01

    Molecular links between receptor-kinases and Rac/ROP family small GTPases mediated by activator guanine nucleotide exchange factors (GEFs) govern diverse biological processes. However, it is unclear how the Rac/ROP GTPases orchestrate such a wide variety of activities. Here, we show that rice OsRacGEF1 forms homodimers, and heterodimers with OsRacGEF2, at the plasma membrane (PM) and the endoplasmic reticulum (ER). OsRacGEF2 does not bind directly to the receptor-like kinase (RLK) OsCERK1, but forms a complex with OsCERK1 through OsRacGEF1 at the ER. This complex is transported from ER to the PM and there associates with OsRac1, resulting in the formation of a stable immune complex. Such RLK-GEF heterodimer complexes may explain the diversity of Rac/ROP family GTPase signalings. PMID:26251883

  12. Arf nucleotide binding site opener [ARNO] promotes sequential activation of Arf6, Cdc42 and Rac1 and insulin secretion in INS 832/13 β-cells and rat islets

    PubMed Central

    Jayaram, Bhavaani; Syed, Ismail; Kyathanahalli, Chandrashekara N.; Rhodes, Christopher J.; Kowluru, Anjaneyulu

    2011-01-01

    Glucose-stimulated insulin secretion [GSIS] involves interplay between small G-proteins and their regulatory factors. Herein, we tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide exchange factor [GEF] for the small G-protein Arf6, mediates the functional activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of Cdc42 and Rac1, which have been implicated in GSIS. Molecular biological [i.e., expression of inactive mutants or siRNA] and pharmacological approaches were employed to assess the roles for ARNO/Arf6 signaling pathway in insulin secretion in normal rat islets and INS 832/13 cells. Degrees of activation of Arf6 and Cdc42/Rac1 were quantitated by GST-GGA3 and PAK-1 kinase pull-down assays, respectively. ARNO is expressed in INS 832/13 cells, rat islets and human islets. Expression of inactive mutants of Arf6 [Arf6-T27N] or ARNO [ARNO-E156K] or siRNA-ARNO markedly reduced GSIS in isolated β-cells. secinH3, a selective inhibitor of ARNO/Arf6 signaling axis, also inhibited GSIS in INS 832/13 cells and rat islets. Stimulatory concentrations of glucose promoted Arf6 activation, which was inhibited by secinH3 or siRNA-ARNO, suggesting that ARNO/Arf6 signaling cascade is necessary for GSIS. secinH3 or siRNA-ARNO also inhibited glucose-induced activation of Cdc42 and Rac1 suggesting that ARNO/Arf6 might be upstream to Cdc42 and Rac1 activation steps, which are necessary for GSIS. Lastly, co-immunoprecipitation and confocal microscopic studies suggested increased association between Arf6 and ARNO in glucose-stimulated β-cells. These findings provide the first evidence to implicate ARNO in the sequential activation of Arf6, Cdc42 and Rac1 culminating in GSIS. PMID:21276423

  13. Epithelial-specific knockout of the Rac1 gene leads to enamel defects

    PubMed Central

    Huang, Zhan; Kim, Jieun; Lacruz, Rodrigo; Bringas, Pablo; Kaartinen, Vesa M.; Snead, Malcolm L.

    2015-01-01

    Rac1 encodes a 21kDa GTP-binding protein belonging to the RAS superfamily. RAS members play important roles in controlling focal adhesion complex formation and cytoskeleton contraction; activities with consequences to cell growth, adhesion, migration, and differentiation. To examine the role(s) played by Rac1 protein in cell-to-matrix interaction and in enamel matrix biomineralization we used the Cre/loxP binary recombination system to characterize enamel matrix proteins expression and enamel formation in Rac1 knockout mice. Mating between mice bearing the floxed Rac1 allele with mice bearing a keratin14-Cre transgene generate animals in which Rac1 is absent from epithelial organs. The enamel of Rac1 conditional knockout mouse was characterized by computerized tomography (microCT), light microscopy, histochemistry, and back-scatter electron microscopy. Enamel matrix protein expression was analyzed by Western blotting. Major findings showed that the Tomes’ processes of Rac1−/− ameloblasts loose contact with the forming enamel matrix in un-erupted teeth. The abundance of amelogenin and ameloblastin was reduced in the Rac1−/− ameloblasts. After eruption, the enamel from the Rac1−/− mice displayed severe structural defects with the complete loss of enamel. These results support an essential role for Rac1 function in the dental epithelium involving cell-matrix interaction and matrix biomineralization. PMID:22243243

  14. Dewatering Peat With Activated Carbon

    NASA Technical Reports Server (NTRS)

    Rohatgi, N. K.

    1984-01-01

    Proposed process produces enough gas and carbon to sustain itself. In proposed process peat slurry is dewatered to approximately 40 percent moisture content by mixing slurry with activated carbon and filtering with solid/liquid separation techniques.

  15. Prolactin-Stimulated Activation of ERK1/2 Mitogen-Activated Protein Kinases is Controlled by PI3-Kinase/Rac/PAK Signaling Pathway in Breast Cancer Cells

    PubMed Central

    Aksamitiene, Edita; Achanta, Sirisha; Kolch, Walter; Kholodenko, Boris N.; Hoek, Jan B.; Kiyatkin, Anatoly

    2011-01-01

    There is strong evidence that deregulation of prolactin (PRL) signaling contributes to pathogenesis and chemoresistance of breast cancer. Therefore, understanding cross-talk between distinct signal transduction pathways triggered by activation of the prolactin receptor (PRL-R), is essential for elucidating the pathogenesis of metastatic breast cancer. In this study, we applied a sequential inhibitory analysis of various signaling intermediates to examine the hierarchy of protein interactions within the PRL signaling network and to evaluate the relative contributions of multiple signaling branches downstream of PRL-R to the activation of the extracellular signal-regulated kinases ERK1 and ERK2 in T47D and MCF-7 human breast cancer cells. Quantitative measurements of the phosphorylation/activation patterns of proteins showed that PRL simultaneously activated Src family kinases (SFKs) and the JAK/STAT, phosphoinositide-3 (PI3)-kinase/Akt and MAPK signaling pathways. The specific blockade or siRNA-mediated suppression of SFK/FAK, JAK2/STAT5, PI3-kinase/PDK1/Akt, Rac/PAK or Ras regulatory circuits revealed that (1) the PI3-kinase/Akt pathway is required for activation of the MAPK/ERK signaling cascade upon PRL stimulation; (2) PI3-kinase-mediated activation of the c-Raf-MEK1/2-ERK1/2 cascade occurs independent of signaling dowstream of STATs, Akt and PKC, but requires JAK2, SFKs and FAK activities; (3) activated PRL-R mainly utilizes the PI3-kinase-dependent Rac/PAK pathway rather than the canonical Shc/Grb2/SOS/Ras route to initiate and sustain ERK1/2 signaling. By interconnecting diverse signaling pathways PLR may enhance proliferation, survival, migration and invasiveness of breast cancer cells. PMID:21726627

  16. Prolactin-stimulated activation of ERK1/2 mitogen-activated protein kinases is controlled by PI3-kinase/Rac/PAK signaling pathway in breast cancer cells.

    PubMed

    Aksamitiene, Edita; Achanta, Sirisha; Kolch, Walter; Kholodenko, Boris N; Hoek, Jan B; Kiyatkin, Anatoly

    2011-11-01

    There is strong evidence that deregulation of prolactin (PRL) signaling contributes to pathogenesis and chemoresistance of breast cancer. Therefore, understanding cross-talk between distinct signal transduction pathways triggered by activation of the prolactin receptor (PRL-R), is essential for elucidating the pathogenesis of metastatic breast cancer. In this study, we applied a sequential inhibitory analysis of various signaling intermediates to examine the hierarchy of protein interactions within the PRL signaling network and to evaluate the relative contributions of multiple signaling branches downstream of PRL-R to the activation of the extracellular signal-regulated kinases ERK1 and ERK2 in T47D and MCF-7 human breast cancer cells. Quantitative measurements of the phosphorylation/activation patterns of proteins showed that PRL simultaneously activated Src family kinases (SFKs) and the JAK/STAT, phosphoinositide-3 (PI3)-kinase/Akt and MAPK signaling pathways. The specific blockade or siRNA-mediated suppression of SFK/FAK, JAK2/STAT5, PI3-kinase/PDK1/Akt, Rac/PAK or Ras regulatory circuits revealed that (1) the PI3-kinase/Akt pathway is required for activation of the MAPK/ERK signaling cascade upon PRL stimulation; (2) PI3-kinase-mediated activation of the c-Raf-MEK1/2-ERK1/2 cascade occurs independent of signaling dowstream of STATs, Akt and PKC, but requires JAK2, SFKs and FAK activities; (3) activated PRL-R mainly utilizes the PI3-kinase-dependent Rac/PAK pathway rather than the canonical Shc/Grb2/SOS/Ras route to initiate and sustain ERK1/2 signaling. By interconnecting diverse signaling pathways PLR may enhance proliferation, survival, migration and invasiveness of breast cancer cells. PMID:21726627

  17. IAPs as E3 ligases of Rac1: shaping the move.

    PubMed

    Oberoi-Khanuja, Tripat Kaur; Rajalingam, Krishnaraj

    2012-01-01

    Inhibitors of Apoptosis Proteins (IAPs) are well-studied E3 ubiquitin ligases predominantly known for regulation of apoptosis. We uncovered that IAPs can function as a direct E3 ubiquitin ligase of RhoGTPase Rac1. cIAP1 and XIAP directly conjugate polyubiquitin chains to Lysine 147 of activated Rac1 and target it for proteasomal degradation. Consistently, loss of these IAPs by various strategies led to stabilization of Rac1 and mesenchymal mode of migration in tumor cells. IAPs also regulate Rac1 degradation upon RhoGDI1 depletion and CNF1 toxin treatment. Our observations revealed an evolutionarily conserved role of IAPs in regulating Rac1 stability shedding light on to the mechanisms behind ubiquitination-dependent inactivation of Rac1 signaling. PMID:22790203

  18. A Cdc42- and Rac-interactive binding (CRIB) domain mediates functions of coronin.

    PubMed

    Swaminathan, Karthic; Müller-Taubenberger, Annette; Faix, Jan; Rivero, Francisco; Noegel, Angelika A

    2014-01-01

    The Cdc42- and Rac-interactive binding motif (CRIB) of coronin binds to Rho GTPases with a preference for GDP-loaded Rac. Mutation of the Cdc42- and Rac-interactive binding motif abrogates Rac binding. This results in increased 1evels of activated Rac in coronin-deficient Dictyostelium cells (corA(-)), which impacts myosin II assembly. corA(-) cells show increased accumulation of myosin II in the cortex of growth-phase cells. Myosin II assembly is regulated by myosin heavy chain kinase-mediated phosphorylation of its tail. Kinase activity depends on the activation state of the p21-activated kinase a. The myosin II defect of corA(-) mutant is alleviated by dominant-negative p21-activated kinase a. It is rescued by wild-type coronin, whereas coronin carrying a mutated Cdc42- and Rac-interactive binding motif failed to rescue the myosin defect in corA(-) mutant cells. Ectopically expressed myosin heavy chain kinases affinity purified from corA(-) cells show reduced kinase activity. We propose that coronin through its affinity for GDP-Rac regulates the availability of GTP-Rac for activation of downstream effectors. PMID:24347642

  19. Rac regulates vascular endothelial growth factor stimulated motility.

    PubMed

    Soga, N; Connolly, J O; Chellaiah, M; Kawamura, J; Hruska, K A

    2001-01-01

    During angiogenesis endothelial cells migrate towards a chemotactic stimulus. Understanding the mechanism of endothelial cell migration is critical to the therapeutic manipulation of angiogenesis and ultimately cancer prevention. Vascular endothelial growth factor (VEGF) is a potent chemotactic stimulus of endothelial cells during angiogenesis. The endothelial cell signal transduction pathway of VEGF represents a potential target for cancer therapy, but the mechanisms of post-receptor signal transduction including the roles of rho family GTPases in regulating the cytoskeletal effects of VEGF in endothelial cells are not understood. Here we analyze the mechanisms of cell migration in the mouse brain endothelial cell line (bEND3). Stable transfectants containing a tetracycline repressible expression vector were used to induce expression of Rac mutants. Endothelial cell haptotaxis was stimulated by constitutively active V12Rac on collagen and vitronectin coated supports, and chemotaxis was further stimulated by VEGF. Osteopontin coated supports were the most stimulatory to bEND3 haptotaxis, but VEGF was not effective in further increasing migration on osteopontin coated supports. Haptotaxis on support coated with collagen, vitronectin, and to a lesser degree osteopontin was inhibited by N17 Rac. N17 Rac expression blocked stimulation of endothelial cell chemotaxis by VEGF. As part of the chemotactic stimulation, VEGF caused a loss of actin organization at areas of cell-cell contact and increased stress fiber expression in endothelial cells which were directed towards pores in the transwell membrane. N17 Rac prevented the stimulation of cell-cell contact disruption and the stress fiber stimulation by VEGF. These data demonstrate two pathways of regulating endothelial cell motility, one in which Rac is activated by matrix/integrin stimulation and is a crucial modulator of endothelial cell haptotaxis. The other pathway, in the presence of osteopontin, is Rac independent

  20. Aluminium salalens vs. salans: "Initiator Design" for the isoselective polymerisation of rac-lactide.

    PubMed

    McKeown, Paul; Davidson, Matthew G; Kociok-Köhn, Gabriele; Jones, Matthew D

    2016-08-16

    We report the rationalised design of aluminium initiators and their application for ROP of rac-lactide (rac-LA). A very minor change to the ligand backbone (imine reduction) to give secondary amines was found to have a dramatic effect on activity and selectivity with isotactic PLA being realised. PMID:27487791

  1. Rac1 is a novel regulator of contraction-stimulated glucose uptake in skeletal muscle.

    PubMed

    Sylow, Lykke; Jensen, Thomas E; Kleinert, Maximilian; Mouatt, Joshua R; Maarbjerg, Stine J; Jeppesen, Jacob; Prats, Clara; Chiu, Tim T; Boguslavsky, Shlomit; Klip, Amira; Schjerling, Peter; Richter, Erik A

    2013-04-01

    In skeletal muscle, the actin cytoskeleton-regulating GTPase, Rac1, is necessary for insulin-dependent GLUT4 translocation. Muscle contraction increases glucose transport and represents an alternative signaling pathway to insulin. Whether Rac1 is activated by muscle contraction and regulates contraction-induced glucose uptake is unknown. Therefore, we studied the effects of in vivo exercise and ex vivo muscle contractions on Rac1 signaling and its regulatory role in glucose uptake in mice and humans. Muscle Rac1-GTP binding was increased after exercise in mice (~60-100%) and humans (~40%), and this activation was AMP-activated protein kinase independent. Rac1 inhibition reduced contraction-stimulated glucose uptake in mouse muscle by 55% in soleus and by 20-58% in extensor digitorum longus (EDL; P < 0.01). In agreement, the contraction-stimulated increment in glucose uptake was decreased by 27% (P = 0.1) and 40% (P < 0.05) in soleus and EDL muscles, respectively, of muscle-specific inducible Rac1 knockout mice. Furthermore, depolymerization of the actin cytoskeleton decreased contraction-stimulated glucose uptake by 100% and 62% (P < 0.01) in soleus and EDL muscles, respectively. These are the first data to show that Rac1 is activated during muscle contraction in murine and human skeletal muscle and suggest that Rac1 and possibly the actin cytoskeleton are novel regulators of contraction-stimulated glucose uptake. PMID:23274900

  2. Rac1 Is a Novel Regulator of Contraction-Stimulated Glucose Uptake in Skeletal Muscle

    PubMed Central

    Sylow, Lykke; Jensen, Thomas E.; Kleinert, Maximilian; Mouatt, Joshua R.; Maarbjerg, Stine J.; Jeppesen, Jacob; Prats, Clara; Chiu, Tim T.; Boguslavsky, Shlomit; Klip, Amira; Schjerling, Peter; Richter, Erik A.

    2013-01-01

    In skeletal muscle, the actin cytoskeleton-regulating GTPase, Rac1, is necessary for insulin-dependent GLUT4 translocation. Muscle contraction increases glucose transport and represents an alternative signaling pathway to insulin. Whether Rac1 is activated by muscle contraction and regulates contraction-induced glucose uptake is unknown. Therefore, we studied the effects of in vivo exercise and ex vivo muscle contractions on Rac1 signaling and its regulatory role in glucose uptake in mice and humans. Muscle Rac1-GTP binding was increased after exercise in mice (∼60–100%) and humans (∼40%), and this activation was AMP-activated protein kinase independent. Rac1 inhibition reduced contraction-stimulated glucose uptake in mouse muscle by 55% in soleus and by 20–58% in extensor digitorum longus (EDL; P < 0.01). In agreement, the contraction-stimulated increment in glucose uptake was decreased by 27% (P = 0.1) and 40% (P < 0.05) in soleus and EDL muscles, respectively, of muscle-specific inducible Rac1 knockout mice. Furthermore, depolymerization of the actin cytoskeleton decreased contraction-stimulated glucose uptake by 100% and 62% (P < 0.01) in soleus and EDL muscles, respectively. These are the first data to show that Rac1 is activated during muscle contraction in murine and human skeletal muscle and suggest that Rac1 and possibly the actin cytoskeleton are novel regulators of contraction-stimulated glucose uptake. PMID:23274900

  3. Separating proteins with activated carbon.

    PubMed

    Stone, Matthew T; Kozlov, Mikhail

    2014-07-15

    Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon. PMID:24898563

  4. Identification, characterization and immunological analysis of Ras related C3 botulinum toxin substrate 1 (Rac1) from grass carp Ctenopharyngodon idella.

    PubMed

    Hu, Mo-Yan; Shen, Yu-Bang; Xu, Xiao-Yan; Yu, Hong-Yan; Zhang, Meng; Dang, Yun-Fei; Li, Jia-Le

    2016-01-01

    Rac1, a Rho GTPase, serves critical immunological functions in mammals. Here, a Rac1 homolog (gcRac1) was identified in grass carp (Ctenopharyngodon idella). The full-length 2023-base pair gcRac1 cDNA contained a 579-bp open reading frame encoding a 192-residue protein, including a conserved RHO domain and nuclear localization signal. The gcRac1 protein shares high identity with other Rac1 counterparts and phylogenetically clustered with Danio rerio Rac1. The gcRac1 transcript showed wide tissue distribution and was inducible by Aeromonas hydrophila in vivo and in vitro; its expression also fluctuated with LPS or flagellin stimulation in vitro. With gcRac1 over-expression, gcPAK1, gcIL1-β, gcTNF-α and gcIFN were basically up-regulated by A. hydrophila and bacterial PAMPs induction, while gcRac1 knockdown decreased these transcripts after A. hydrophila challenge. Over-expression of gcRac1 reduced, while its suppression facilitated, bacterial invasion. Moreover, gcRac1 could activate NF-κB signaling. These findings implicate the vital role of gcRac1 in grass carp innate immunity. PMID:26315145

  5. Individual Rac GTPases Mediate Aspects of Prostate Cancer Cell and Bone Marrow Endothelial Cell Interactions

    PubMed Central

    Chatterjee, Moumita; Sequeira, Linda; Jenkins-Kabaila, Mashariki; Dubyk, Cara W.; Pathak, Surabhi; van Golen, Kenneth L.

    2011-01-01

    The Rho GTPases organize the actin cytoskeleton and are involved in cancer metastasis. Previously, we demonstrated that RhoC GTPase was required for PC-3 prostate cancer cell invasion. Targeted down-regulation of RhoC led to sustained activation of Rac1 GTPase and morphological, molecular and phenotypic changes reminiscent of epithelial to mesenchymal transition. We also reported that Rac1 is required for PC-3 cell diapedesis across a bone marrow endothelial cell layer. In the current study, we queried whether Rac3 and RhoG GTPases also have a role in prostate tumor cell diapedesis. Using specific siRNAs we demonstrate roles for each protein in PC-3 and C4-2 cell adhesion and diapedesis. We have shown that the chemokine CCL2 induces tumor cell diapedesis via Rac1 activation. Here we find that RhoG partially contributes to CCL2-induced tumor cell diapedesis. We also find that Rac1 GTPase mediates tight binding of prostate cancer cells to bone marrow endothelial cells and promotes retraction of endothelial cells required for tumor cell diapedesis. Finally, Rac1 leads to β1 integrin activation, suggesting a mechanism that Rac1 can mediate tight binding with endothelial cells. Together, our data suggest that Rac1 GTPase is key mediator of prostate cancer cell-bone marrow endothelial cell interactions. PMID:21776386

  6. Endothelial Rac1 is essential for hematogenous metastasis to the lung.

    PubMed

    Yao, Hongyi; Shi, Wei; Wu, Junsong; Xu, Chengyun; Wang, Jirong; Shao, Yanan; Wu, Ximei; Zhang, Zhongmiao

    2015-07-10

    A variety of vasoactive stimuli induce endothelial permeability through Rac1, a membrane of Rho small GTPases. Here, we determine whether tumor-secreted vasoactive stimulant through Rac1 inducing permeability contributes to hematogenous metastasis. Activation of Rac1 was assayed in human umbilical vein endothelial cells (HUVEC), transendothelial passages were measured by Transwell chambers, and hematogenously metastatic mouse model was generated by intravenous injection with Lewis lung carcinoma cells (LLC). LLC secreted abundant vascular endothelial growth factor (VEGF) in the culture media and sera of mice bearing LLC xenografts or metastatic LLC, and VEGF activated Rac1 through VEGF receptors/PI3Kβ signaling cascade, resulting in hyperoxidative stress and consequent hyperpermeability in HUVEC. Moreover, in co-culture of LLC and HUVEC, significant increases in endothelial permeability and transendothelial migration of LLC were robustly attenuated by either anti-VEGF neutralizing antibody or Rac1 knockdown in HUVEC. Finally, in metastatic mouse model, deletion of one copy of Rac1 in endothelium not only significantly attenuated LLC-induced vascular permeability, but robustly reduced the metastasis of LLC to lungs. This study supports that tumor-secreted vasoactive stimuli activate Rac1 to induce permeability and consequent transendothelial migration of tumor cells, and that loss of Rac1 function in endothelium is an effective therapeutic intervention for hematogenous metastasis. PMID:25991673

  7. Endothelial Rac1 is essential for hematogenous metastasis to the lung

    PubMed Central

    Wu, Junsong; Xu, Chengyun; Wang, Jirong; Shao, Yanan; Wu, Ximei; Zhang, Zhongmiao

    2015-01-01

    A variety of vasoactive stimuli induce endothelial permeability through Rac1, a membrane of Rho small GTPases. Here, we determine whether tumor-secreted vasoactive stimulant through Rac1 inducing permeability contributes to hematogenous metastasis. Activation of Rac1 was assayed in human umbilical vein endothelial cells (HUVEC), transendothelial passages were measured by Transwell chambers, and hematogenously metastatic mouse model was generated by intravenous injection with Lewis lung carcinoma cells (LLC). LLC secreted abundant vascular endothelial growth factor (VEGF) in the culture media and sera of mice bearing LLC xenografts or metastatic LLC, and VEGF activated Rac1 through VEGF receptors/PI3Kβ signaling cascade, resulting in hyperoxidative stress and consequent hyperpermeability in HUVEC. Moreover, in co-culture of LLC and HUVEC, significant increases in endothelial permeability and transendothelial migration of LLC were robustly attenuated by either anti-VEGF neutralizing antibody or Rac1 knockdown in HUVEC. Finally, in metastatic mouse model, deletion of one copy of Rac1 in endothelium not only significantly attenuated LLC-induced vascular permeability, but robustly reduced the metastasis of LLC to lungs. This study supports that tumor-secreted vasoactive stimuli activate Rac1 to induce permeability and consequent transendothelial migration of tumor cells, and that loss of Rac1 function in endothelium is an effective therapeutic intervention for hematogenous metastasis. PMID:25991673

  8. The Rac1 hypervariable region in targeting and signaling: a tail of many stories.

    PubMed

    Lam, B Daniel; Hordijk, Peter L

    2013-01-01

    Cellular signaling by small GTPases is critically dependent on proper spatio-temporal orchestration of activation and output. In addition to their core G (guanine nucleotide binding)-domain, small GTPases comprise a hypervariable region (HVR) and a lipid anchor that are generally accepted to control subcellullar localization. The HVR encodes in many small GTPases a polybasic region (PBR) that permits charge-mediated association to the inner leaflet of the plasma membrane or to intracellular organelles. Over the past 15-20 years, evidence has accumulated for specific protein-protein interactions, mediated by the HVR, that control both targeting and signaling specificity of small GTPases. Using the RhoGTPase Rac1 as a paradigm we here review a series of protein partners that require the Rac1 HVR for association and that control various aspects of localized Rac1 signaling. Some of these proteins represent Rac1 activators, whereas others mediate Rac1 inactivation and degradation and yet others potentiate Rac1 downstream signaling. Finally, evidence is discussed which shows that the HVR of Rac1 also contributes to effector interactions, co-operating with the N-terminal effector domain. The complexity of localized Rac1 signaling, reviewed here, is most likely exemplary for many other small GTPases as well, representing a challenge to identify and define similar mechanisms controlling the specific signaling induced by small GTPases. PMID:23354415

  9. SPARC Controls Melanoma Cell Plasticity through Rac1

    PubMed Central

    Salvatierra, Edgardo; Alvarez, Mariano J.; Leishman, Claudia C.; Rivas Baquero, Elvia; Lutzky, Viviana P.; Chuluyan, H. Eduardo; Podhajcer, Osvaldo L.

    2015-01-01

    Cell transition to a more aggressive mesenchymal-like phenotype is a hallmark of cancer progression that involves different steps and requires tightly regulated cell plasticity. SPARC (Secreted Protein Acidic and Rich in Cysteine) is a matricellular protein that promotes this transition in various malignant cell types, including melanoma cells. We found that suppression of SPARC expression in human melanoma cells compromised cell migration, adhesion, cytoskeleton structure, and cell size. These changes involved the Akt/mTOR pathway. Re-expression of SPARC or protein addition restored all the cell features. Suppression of SPARC expression was associated with increased Rac1-GTP levels and its membrane localization. Expression of the dominant negative mutant of Rac1 counteracted almost all the changes observed in SPARC-deficient cells. Overall, these data suggest that most of the SPARC-mediated effects occurred mainly through the blockade of Rac1 activity. PMID:26248315

  10. MYADM regulates Rac1 targeting to ordered membranes required for cell spreading and migration.

    PubMed

    Aranda, Juan F; Reglero-Real, Natalia; Kremer, Leonor; Marcos-Ramiro, Beatriz; Ruiz-Sáenz, Ana; Calvo, María; Enrich, Carlos; Correas, Isabel; Millán, Jaime; Alonso, Miguel A

    2011-04-15

    Membrane organization into condensed domains or rafts provides molecular platforms for selective recruitment of proteins. Cell migration is a general process that requires spatiotemporal targeting of Rac1 to membrane rafts. The protein machinery responsible for making rafts competent to recruit Rac1 remains elusive. Some members of the MAL family of proteins are involved in specialized processes dependent on this type of membrane. Because condensed membrane domains are a general feature of the plasma membrane of all mammalian cells, we hypothesized that MAL family members with ubiquitous expression and plasma membrane distribution could be involved in the organization of membranes for cell migration. We show that myeloid-associated differentiation marker (MYADM), a protein with unique features within the MAL family, colocalizes with Rac1 in membrane protrusions at the cell surface and distributes in condensed membranes. MYADM knockdown (KD) cells had altered membrane condensation and showed deficient incorporation of Rac1 to membrane raft fractions and, similar to Rac1 KD cells, exhibited reduced cell spreading and migration. Results of rescue-of-function experiments by expression of MYADM or active Rac1L61 in cells knocked down for Rac1 or MYADM, respectively, are consistent with the idea that MYADM and Rac1 act on parallel pathways that lead to similar functional outcomes. PMID:21325632

  11. Mitochondrial Dysfunction in Human Leukemic Stem/Progenitor Cells upon Loss of RAC2

    PubMed Central

    Capala, Marta E.; Maat, Henny; Bonardi, Francesco; van den Boom, Vincent; Kuipers, Jeroen; Vellenga, Edo; Giepmans, Ben N. G.; Schuringa, Jan Jacob

    2015-01-01

    Leukemic stem cells (LSCs) reside within bone marrow niches that maintain their relatively quiescent state and convey resistance to conventional treatment. Many of the microenvironmental signals converge on RAC GTPases. Although it has become clear that RAC proteins fulfill important roles in the hematopoietic compartment, little has been revealed about the downstream effectors and molecular mechanisms. We observed that in BCR-ABL-transduced human hematopoietic stem/progenitor cells (HSPCs) depletion of RAC2 but not RAC1 induced a marked and immediate decrease in proliferation, progenitor frequency, cobblestone formation and replating capacity, indicative for reduced self-renewal. Cell cycle analyses showed reduced cell cycle activity in RAC2-depleted BCR-ABL leukemic cobblestones coinciding with an increased apoptosis. Moreover, a decrease in mitochondrial membrane potential was observed upon RAC2 downregulation, paralleled by severe mitochondrial ultrastructural malformations as determined by automated electron microscopy. Proteome analysis revealed that RAC2 specifically interacted with a set of mitochondrial proteins including mitochondrial transport proteins SAM50 and Metaxin 1, and interactions were confirmed in independent co-immunoprecipitation studies. Downregulation of SAM50 also impaired the proliferation and replating capacity of BCR-ABL-expressing cells, again associated with a decreased mitochondrial membrane potential. Taken together, these data suggest an important role for RAC2 in maintaining mitochondrial integrity. PMID:26016997

  12. Cooperation of distinct Rac-dependent pathways to stabilise E-cadherin adhesion.

    PubMed

    Erasmus, Jennifer C; Welsh, Natalie J; Braga, Vania M M

    2015-09-01

    The precise mechanisms via which Rac1 is activated by cadherin junctions are not fully known. In keratinocytes Rac1 activation by cadherin junctions requires EGFR signalling, but how EGFR does so is unclear. To address which activator could mediate E-cadherin signalling to Rac1, we investigated EGFR and two Rac1 GEFs, SOS1 and DOCK180. EGFR RNAi prevented junction-induced Rac1 activation and led to fragmented localization of E-cadherin at cadherin contacts. In contrast, depletion of another EGFR family member, ErbB3, did not interfere with either process. DOCK180 RNAi, but not SOS1, prevented E-cadherin-induced Rac1 activation. However, in a strong divergence from EGFR RNAi phenotype, DOCK180 depletion did not perturb actin recruitment or cadherin localisation at junctions. Rather, reduced DOCK180 levels impaired the resistance to mechanical stress of pre-formed cell aggregates. Thus, within the same cell type, EGFR and DOCK180 regulate Rac1 activation by newly-formed contacts, but control separate cellular events that cooperate to stabilise junctions. PMID:25957131

  13. Cooperation of distinct Rac-dependent pathways to stabilise E-cadherin adhesion

    PubMed Central

    Erasmus, Jennifer C.; Welsh, Natalie J.; Braga, Vania M.M.

    2015-01-01

    The precise mechanisms via which Rac1 is activated by cadherin junctions are not fully known. In keratinocytes Rac1 activation by cadherin junctions requires EGFR signalling, but how EGFR does so is unclear. To address which activator could mediate E-cadherin signalling to Rac1, we investigated EGFR and two Rac1 GEFs, SOS1 and DOCK180. EGFR RNAi prevented junction-induced Rac1 activation and led to fragmented localization of E-cadherin at cadherin contacts. In contrast, depletion of another EGFR family member, ErbB3, did not interfere with either process. DOCK180 RNAi, but not SOS1, prevented E-cadherin-induced Rac1 activation. However, in a strong divergence from EGFR RNAi phenotype, DOCK180 depletion did not perturb actin recruitment or cadherin localisation at junctions. Rather, reduced DOCK180 levels impaired the resistance to mechanical stress of pre-formed cell aggregates. Thus, within the same cell type, EGFR and DOCK180 regulate Rac1 activation by newly-formed contacts, but control separate cellular events that cooperate to stabilise junctions. PMID:25957131

  14. Eiger-induced cell death relies on Rac1-dependent endocytosis.

    PubMed

    Ruan, W; Srinivasan, A; Lin, S; Kara, K-I; Barker, P A

    2016-01-01

    Signaling via tumor necrosis factor receptor (TNFR) superfamily members regulates cellular life and death decisions. A subset of mammalian TNFR proteins, most notably the p75 neurotrophin receptor (p75NTR), induces cell death through a pathway that requires activation of c-Jun N-terminal kinases (JNKs). However the receptor-proximal signaling events that mediate this remain unclear. Drosophila express a single tumor necrosis factor (TNF) ligand termed Eiger (Egr) that activates JNK-dependent cell death. We have exploited this model to identify phylogenetically conserved signaling events that allow Egr to induce JNK activation and cell death in vivo. Here we report that Rac1, a small GTPase, is specifically required in Egr-mediated cell death. rac1 loss of function blocks Egr-induced cell death, whereas Rac1 overexpression enhances Egr-induced killing. We identify Vav as a GEF for Rac1 in this pathway and demonstrate that dLRRK functions as a negative regulator of Rac1 that normally acts to constrain Egr-induced death. Thus dLRRK loss of function increases Egr-induced cell death in the fly. We further show that Rac1-dependent entry of Egr into early endosomes is a crucial prerequisite for JNK activation and for cell death and show that this entry requires the activity of Rab21 and Rab7. These findings reveal novel regulatory mechanisms that allow Rac1 to contribute to Egr-induced JNK activation and cell death. PMID:27054336

  15. Eiger-induced cell death relies on Rac1-dependent endocytosis

    PubMed Central

    Ruan, W; Srinivasan, A; Lin, S; Kara, k-I; Barker, P A

    2016-01-01

    Signaling via tumor necrosis factor receptor (TNFR) superfamily members regulates cellular life and death decisions. A subset of mammalian TNFR proteins, most notably the p75 neurotrophin receptor (p75NTR), induces cell death through a pathway that requires activation of c-Jun N-terminal kinases (JNKs). However the receptor-proximal signaling events that mediate this remain unclear. Drosophila express a single tumor necrosis factor (TNF) ligand termed Eiger (Egr) that activates JNK-dependent cell death. We have exploited this model to identify phylogenetically conserved signaling events that allow Egr to induce JNK activation and cell death in vivo. Here we report that Rac1, a small GTPase, is specifically required in Egr-mediated cell death. rac1 loss of function blocks Egr-induced cell death, whereas Rac1 overexpression enhances Egr-induced killing. We identify Vav as a GEF for Rac1 in this pathway and demonstrate that dLRRK functions as a negative regulator of Rac1 that normally acts to constrain Egr-induced death. Thus dLRRK loss of function increases Egr-induced cell death in the fly. We further show that Rac1-dependent entry of Egr into early endosomes is a crucial prerequisite for JNK activation and for cell death and show that this entry requires the activity of Rab21 and Rab7. These findings reveal novel regulatory mechanisms that allow Rac1 to contribute to Egr-induced JNK activation and cell death. PMID:27054336

  16. Phosphoinositide 3-kinase enables phagocytosis of large particles by terminating actin assembly through Rac/Cdc42 GTPase-activating proteins

    PubMed Central

    Schlam, Daniel; Bagshaw, Richard D.; Freeman, Spencer A.; Collins, Richard F.; Pawson, Tony; Fairn, Gregory D.; Grinstein, Sergio

    2015-01-01

    Phagocytosis is responsible for the elimination of particles of widely disparate sizes, from large fungi or effete cells to small bacteria. Though superficially similar, the molecular mechanisms involved differ: engulfment of large targets requires phosphoinositide 3-kinase (PI3K), while that of small ones does not. Here, we report that inactivation of Rac and Cdc42 at phagocytic cups is essential to complete internalization of large particles. Through a screen of 62 RhoGAP-family members, we demonstrate that ARHGAP12, ARHGAP25 and SH3BP1 are responsible for GTPase inactivation. Silencing these RhoGAPs impairs phagocytosis of large targets. The GAPs are recruited to large—but not small—phagocytic cups by products of PI3K, where they synergistically inactivate Rac and Cdc42. Remarkably, the prominent accumulation of phosphatidylinositol 3,4,5-trisphosphate characteristic of large-phagosome formation is less evident during phagocytosis of small targets, accounting for the contrasting RhoGAP distribution and the differential requirement for PI3K during phagocytosis of dissimilarly sized particles. PMID:26465210

  17. Activated carbon to the rescue

    SciTech Connect

    Sen, S.

    1996-03-01

    This article describes the response to pipeline spill of ethylene dichloride (EDC) on the property of an oil company. Activated carbon cleanup proceedure was used. During delivery, changeout, transport, storage, thermal reactivation, and return delivery to the site, the carbon never came into direct contact with operating personnel or the atmosphere. More than 10,000 tones of dredge soil and 50 million gallons of surface water were processed during the emergency response.

  18. Cloning and characterization of bovine low molecular weight GTPases (Rac1 and Rac2) and rho GDP-dissociation inhibitor 2 (D4-GDI).

    PubMed

    Davis, A R; Clements, M K; Bunger, P L; Siemsen, D W; Quinn, M T

    2000-05-23

    GTPases of the Rho family play important roles in human leukocyte signal transduction pathways; however, little is known about the function of these proteins in bovine cells. In the present studies, we isolated molecular clones of bovine Rac1, Rac2, and the Rac/Rho GTPase regulatory protein D4-GDP dissociation inhibitor (D4-GDI) from a bovine bone marrow cDNA library. These clones contained complete open reading frames, encoding 192, 192, and 200 amino acids, respectively. Comparison of the bovine amino acid sequences with those of other species demonstrated a high degree of identity of these proteins across all species, suggesting that these proteins likely play conserved functional roles in bovine leukocyte signal transduction pathways. Comparative Western blotting of these proteins in human and bovine neutrophil cytosol demonstrated that Rac2 was the predominant Rac species and that D4-GDI was the predominant GDI species in bovine neutrophil cytosol. Despite the high degree of homology between human and bovine Rac2, some of the anti-peptide antibody probes prepared against human Rac2 failed to recognize the bovine homologue. We also showed by subcellular fractionation techniques that Rac2 is localized primarily to the cytosolic compartment of resting bovine neutrophils, but is translocated to the plasma membrane after stimulation with PMA. These findings suggest that Rac2 does play a role in bovine neutrophil activation. In addition, these data will be helpful in developing more specific probes for investigating the role of these proteins in bovine leukocyte signal transduction pathways and for studying various inflammatory diseases in cattle. PMID:10802295

  19. Exome sequencing identifies recurrent somatic RAC1 mutations in melanoma

    SciTech Connect

    Krauthammer, Michael; Kong, Yong; Ha, Byung Hak; Evans, Perry; Bacchiocchi, Antonella; McCusker, James P.; Cheng, Elaine; Davis, Matthew J.; Goh, Gerald; Choi, Murim; Ariyan, Stephan; Narayan, Deepak; Dutton-Regester, Ken; Capatana, Ana; Holman, Edna C.; Bosenberg, Marcus; Sznol, Mario; Kluger, Harriet M.; Brash, Douglas E.; Stern, David F.; Materin, Miguel A.; Lo, Roger S.; Mane, Shrikant; Ma, Shuangge; Kidd, Kenneth K.; Hayward, Nicholas K.; Lifton, Richard P.; Schlessinger, Joseph; Boggon, Titus J.; Halaban, Ruth

    2012-10-11

    We characterized the mutational landscape of melanoma, the form of skin cancer with the highest mortality rate, by sequencing the exomes of 147 melanomas. Sun-exposed melanomas had markedly more ultraviolet (UV)-like C>T somatic mutations compared to sun-shielded acral, mucosal and uveal melanomas. Among the newly identified cancer genes was PPP6C, encoding a serine/threonine phosphatase, which harbored mutations that clustered in the active site in 12% of sun-exposed melanomas, exclusively in tumors with mutations in BRAF or NRAS. Notably, we identified a recurrent UV-signature, an activating mutation in RAC1 in 9.2% of sun-exposed melanomas. This activating mutation, the third most frequent in our cohort of sun-exposed melanoma after those of BRAF and NRAS, changes Pro29 to serine (RAC1{sup P29S}) in the highly conserved switch I domain. Crystal structures, and biochemical and functional studies of RAC1{sup P29S} showed that the alteration releases the conformational restraint conferred by the conserved proline, causes an increased binding of the protein to downstream effectors, and promotes melanocyte proliferation and migration. These findings raise the possibility that pharmacological inhibition of downstream effectors of RAC1 signaling could be of therapeutic benefit.

  20. Temporal Rac1 - HIF-1 crosstalk modulates hypoxic survival of aged neurons.

    PubMed

    Güntert, Tanja; Gassmann, Max; Ogunshola, Omolara O

    2016-07-01

    Neurodegenerative diseases are frequently associated with hypoxic conditions. During hypoxia the neuronal cytoskeleton is rapidly reorganized and such abnormalities are directly linked to adverse outcomes. Besides their roles as master regulators of the cytoskeleton, the Rho GTPases are also involved in cellular processes stimulated by hypoxic stress. We investigated the contribution of Rac1-mediated signaling to hypoxic responses of mature neurons using primary cortical cells cultured for 17 days in vitro. We show Rac1 is both upregulated and activated during hypoxia. Pharmacological inhibition of Rac1, but not RhoA, completely abrogated hypoxic HIF-1α stabilization and expression of the HIF-1 targets VEGF and GLUT1. Furthermore activity of JNK and GSK3β were also highly dependent on Rac1 activity and biphasic effects were observed after 6 and 24h of exposure. Notably, inhibition of either pathway suppressed HIF-1α accumulation. Although inhibition of Rac1 did not affect neuronal viability during acute exposure cell death was strongly induced after 24h revealing a time-dependent effect of Rac1 signaling on survival. Thus hypoxia-activated Rac1 is critical for neuronal HIF-1α stabilization and survival during oxygen deprivation via integration of complex signaling cascades. PMID:27018294

  1. Rac Regulates Giardia lamblia Encystation by Coordinating Cyst Wall Protein Trafficking and Secretion

    PubMed Central

    Krtková, Jana; Thomas, Elizabeth B.; Alas, Germain C. M.; Schraner, Elisabeth M.; Behjatnia, Habib R.; Hehl, Adrian B.

    2016-01-01

    ABSTRACT Encystation of the common intestinal parasite Giardia lamblia involves the production, trafficking, and secretion of cyst wall material (CWM). However, the molecular mechanism responsible for the regulation of these sequential processes remains elusive. Here, we examined the role of GlRac, Giardia’s sole Rho family GTPase, in the regulation of endomembrane organization and cyst wall protein (CWP) trafficking. Localization studies indicated that GlRac is associated with the endoplasmic reticulum (ER) and the Golgi apparatus-like encystation-specific vesicles (ESVs). Constitutive GlRac signaling increased levels of the ER marker PDI2, induced ER swelling, reduced overall CWP1 production, and promoted the early maturation of ESVs. Quantitative analysis of cells expressing constitutively active hemagglutinin (HA)-tagged GlRac (HA-RacCA) revealed fewer but larger ESVs than control cells. Consistent with the phenotype of premature maturation of ESVs in HA-RacCA-expressing cells, constitutive GlRac signaling resulted in increased CWP1 secretion and, conversely, morpholino depletion of GlRac blocked CWP1 secretion. Wild-type cells unexpectedly secreted large quantities of CWP1 into the medium, and free CWP1 was used cooperatively during cyst formation. These results, in part, could account for the previously reported observation that G. lamblia encysts more efficiently at high cell densities. These studies of GlRac show that it regulates encystation at several levels, and our findings support its coordinating role as a regulator of CWP trafficking and secretion. The central role of GlRac in regulating membrane trafficking and the cytoskeleton, both of which are essential to Giardia parasitism, further suggests its potential as a novel target for drug development to treat giardiasis. PMID:27555307

  2. Aegeline from Aegle marmelos stimulates glucose transport via Akt and Rac1 signaling, and contributes to a cytoskeletal rearrangement through PI3K/Rac1.

    PubMed

    Gautam, Sudeep; Ishrat, Nayab; Singh, Rohit; Narender, Tadigoppula; Srivastava, Arvind K

    2015-09-01

    Aegeline is an alkaloidal-amide, isolated from the leaves of Aegle marmelos and have shown antihyperglycemic as well as antidyslipidemic activities in the validated animal models of type 2 diabetes mellitus. Here we delineate, aegeline enhanced GLUT4 translocation mediated 2-deoxy-glucose uptake in both time and concentration-dependent manner. 2-deoxy-glucose uptake was completely stymied by the transport inhibitors (wortmannin and genistein) in C2C12 myotubes. Pharmacological inhibition of Akt (also known as protein kinase B) and Ras-related C3 botulinum toxin substrate 1 (Rac1) suggest that both Akt and Rac1 operate aegeline-stimulated glucose transport via distinct parallel pathways. Moreover, aegeline activates p21 protein-activated kinase 1 (PAK1) and cofilin (an actin polymerization regulator). Rac1 inhibitor (Rac1 inhib II) and PAK1 inhibitor (IPA-3) completely blocked aegeline-induced phosphorylation of cofilin and p21 protein-activated kinase 1 (PAK1). In summary, these findings suggest that aegeline stimulates the glucose transport through Akt and Rac1 dependent distinct parallel pathways and have cytoskeletal roles via stimulation of the PI3-kinase-Rac1-PAK1-cofilin pathway in the skeletal muscle cells. Therefore, multiple targets of aegeline in the improvement of insulin sensitivity of the skeletal muscle cells may be suggested. PMID:26102565

  3. Deletion of Rac1GTPase in the Myeloid Lineage Protects against Inflammation-Mediated Kidney Injury in Mice

    PubMed Central

    Nagase, Miki; Kurihara, Hidetake; Aiba, Atsu; Young, Morag J.; Sakai, Tatsuo

    2016-01-01

    Macrophage-mediated inflammation has been implicated in various kidney diseases. We previously reported that Rac1, a Rho family small GTP-binding protein, was overactivated in several chronic kidney disease models, and that Rac1 inhibitors ameliorated renal injury, in part via inhibition of inflammation, but the detailed mechanisms have not been clarified. In the present study, we examined whether Rac1 in macrophages effects cytokine production and the inflammatory mechanisms contributing to kidney derangement. Myeloid-selective Rac1 flox control (M-Rac1 FC) and knockout (M-Rac1 KO) mice were generated using the cre-loxP system. Renal function under basal conditions did not differ between M-Rac1 FC and KO mice. Accordingly, lipopolysaccharide (LPS)-evoked kidney injury model was created. LPS elevated blood urea nitrogen and serum creatinine, enhanced expressions of kidney injury biomarkers, Kim-1 and Ngal, and promoted tubular injury in M-Rac1 FC mice. By contrast, deletion of myeloid Rac1 almost completely prevented the LPS-mediated renal impairment. LPS triggered a marked induction of macrophage-derived inflammatory cytokines, IL-6 and TNFα, in M-Rac1 FC mice, which was accompanied by Rac1 activation, stimulation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and reactive oxygen species overproduction. These changes were inhibited in M-Rac1 KO mice. LPS evoked F4/80-positive macrophages accumulation in the kidney, which was not affected by myeloid Rac1 deficiency. We further tested the role of Rac1 signaling in cytokine production using macrophage cell line, RAW264.7. Exposure to LPS increased IL-6 and TNFα mRNA expression. The LPS-driven cytokine induction was dose-dependently blocked by the Rac1 inhibitor EHT1864, NADPH oxidase inhibitor diphenyleneiodonium, and NF-κB inhibitor BAY11-7082. In conclusion, genetic ablation of Rac1 in the myeloid lineage protected against LPS-induced renal inflammation and injury, by suppressing

  4. Deletion of Rac1GTPase in the Myeloid Lineage Protects against Inflammation-Mediated Kidney Injury in Mice.

    PubMed

    Nagase, Miki; Kurihara, Hidetake; Aiba, Atsu; Young, Morag J; Sakai, Tatsuo

    2016-01-01

    Macrophage-mediated inflammation has been implicated in various kidney diseases. We previously reported that Rac1, a Rho family small GTP-binding protein, was overactivated in several chronic kidney disease models, and that Rac1 inhibitors ameliorated renal injury, in part via inhibition of inflammation, but the detailed mechanisms have not been clarified. In the present study, we examined whether Rac1 in macrophages effects cytokine production and the inflammatory mechanisms contributing to kidney derangement. Myeloid-selective Rac1 flox control (M-Rac1 FC) and knockout (M-Rac1 KO) mice were generated using the cre-loxP system. Renal function under basal conditions did not differ between M-Rac1 FC and KO mice. Accordingly, lipopolysaccharide (LPS)-evoked kidney injury model was created. LPS elevated blood urea nitrogen and serum creatinine, enhanced expressions of kidney injury biomarkers, Kim-1 and Ngal, and promoted tubular injury in M-Rac1 FC mice. By contrast, deletion of myeloid Rac1 almost completely prevented the LPS-mediated renal impairment. LPS triggered a marked induction of macrophage-derived inflammatory cytokines, IL-6 and TNFα, in M-Rac1 FC mice, which was accompanied by Rac1 activation, stimulation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and reactive oxygen species overproduction. These changes were inhibited in M-Rac1 KO mice. LPS evoked F4/80-positive macrophages accumulation in the kidney, which was not affected by myeloid Rac1 deficiency. We further tested the role of Rac1 signaling in cytokine production using macrophage cell line, RAW264.7. Exposure to LPS increased IL-6 and TNFα mRNA expression. The LPS-driven cytokine induction was dose-dependently blocked by the Rac1 inhibitor EHT1864, NADPH oxidase inhibitor diphenyleneiodonium, and NF-κB inhibitor BAY11-7082. In conclusion, genetic ablation of Rac1 in the myeloid lineage protected against LPS-induced renal inflammation and injury, by suppressing

  5. The Fer tyrosine kinase regulates interactions of Rho GDP-Dissociation Inhibitor α with the small GTPase Rac

    PubMed Central

    2010-01-01

    Background RhoGDI proteins are important regulators of the small GTPase Rac, because they shuttle Rac from the cytoplasm to membranes and also protect Rac from activation, deactivation and degradation. How the binding and release of Rac from RhoGDI is regulated is not precisely understood. Results We report that the non-receptor tyrosine kinase Fer is able to phosphorylate RhoGDIα and form a direct protein complex with it. This interaction is mediated by the C-terminal end of RhoGDIα. Activation of Fer by reactive oxygen species caused increased phosphorylation of RhoGDIα and pervanadate treatment further augmented this. Tyrosine phosphorylation of RhoGDIα by Fer prevented subsequent binding of Rac to RhoGDIα, but once a RhoGDIα-Rac complex was formed, the Fer kinase was not able to cause Rac release through tyrosine phosphorylation of preformed RhoGDIα-Rac complexes. Conclusions These results identify tyrosine phosphorylation of RhoGDIα by Fer as a mechanism to regulate binding of RhoGDIα to Rac. PMID:21122136

  6. The Role of Rac1 in the Growth Cone Dynamics and Force Generation of DRG Neurons

    PubMed Central

    Sayyad, Wasim A.; Fabris, Paolo; Torre, Vincent

    2016-01-01

    We used optical tweezers, video imaging, immunocytochemistry and a variety of inhibitors to analyze the role of Rac1 in the motility and force generation of lamellipodia and filopodia from developing growth cones of isolated Dorsal Root Ganglia neurons. When the activity of Rac1 was inhibited by the drug EHop-016, the period of lamellipodia protrusion/retraction cycles increased and the lamellipodia retrograde flow rate decreased; moreover, the axial force exerted by lamellipodia was reduced dramatically. Inhibition of Arp2/3 by a moderate amount of the drug CK-548 caused a transient retraction of lamellipodia followed by a complete recovery of their usual motility. This recovery was abolished by the concomitant inhibition of Rac1. The filopodia length increased upon inhibition of both Rac1 and Arp2/3, but the speed of filopodia protrusion increased when Rac1 was inhibited and decreased instead when Arp2/3 was inhibited. These results suggest that Rac1 acts as a switch that activates upon inhibition of Arp2/3. Rac1 also controls the filopodia dynamics necessary to explore the environment. PMID:26766136

  7. The involvement of mutant Rac1 in the formation of invadopodia in cultured melanoma cells

    PubMed Central

    Revach, Or-Yam; Winograd-Katz, Sabina E; Samuels, Yardena; Geiger, Benjamin

    2016-01-01

    In this article, we discuss the complex involvement of a Rho-family GTPase, Rac1, in cell migration and in invadopodia-mediated matrix degradation. We discuss the involvement of invadopodia in invasive cell migration, and their capacity to promote cancer metastasis. Considering the regulation of invadopodia formation, we describe studies that demonstrate the role of Rac1 in the metastatic process, and the suggestion that this effect is attributable to the capacity of Rac1 to promote invadopodia formation. This notion is demonstrated here by showing that knockdown of Rac1 in melanoma cells expressing a wild-type form of this GTPase, reduces invadopodia-dependent matrix degradation. Interestingly, we also show that excessive activity of Rac1, displayed by the P29S, hyperactive, “fast cycling” mutant of Rac1, which is present in 5–10% of melanoma tumors, inhibits invadopodia function. Moreover, knockdown of this hyperactive mutant enhanced matrix degradation, indicating that excessive Rac1 activity by this mutant can negatively regulate invadopodia formation and function. PMID:26873115

  8. Regulating Rac in the Nervous System: Molecular Function and Disease Implication of Rac GEFs and GAPs

    PubMed Central

    Bai, Yanyang; Xiang, Xiaoliang; Liang, Chunmei

    2015-01-01

    Rho family GTPases, including RhoA, Rac1, and Cdc42 as the most studied members, are master regulators of actin cytoskeletal organization. Rho GTPases control various aspects of the nervous system and are associated with a number of neuropsychiatric and neurodegenerative diseases. The activity of Rho GTPases is controlled by two families of regulators, guanine nucleotide exchange factors (GEFs) as the activators and GTPase-activating proteins (GAPs) as the inhibitors. Through coordinated regulation by GEFs and GAPs, Rho GTPases act as converging signaling molecules that convey different upstream signals in the nervous system. So far, more than 70 members of either GEFs or GAPs of Rho GTPases have been identified in mammals, but only a small subset of them have well-known functions. Thus, characterization of important GEFs and GAPs in the nervous system is crucial for the understanding of spatiotemporal dynamics of Rho GTPase activity in different neuronal functions. In this review, we summarize the current understanding of GEFs and GAPs for Rac1, with emphasis on the molecular function and disease implication of these regulators in the nervous system. PMID:25879033

  9. Strengthening College Students' Success through the RAC

    ERIC Educational Resources Information Center

    Anderson, Trela; Kim, Ji Young

    2011-01-01

    This article describes how Fayetteville State University's Reading Across the Curriculum (RAC) model developed for use with underprepared students can effectively improve the literacy and academic language skills of those students. The primary goals and objectives of the RAC program are to train faculty members from various disciplines to create…

  10. An evolutionary analysis of RAC2 identifies haplotypes associated with human autoimmune diseases.

    PubMed

    Sironi, Manuela; Guerini, Franca Rosa; Agliardi, Cristina; Biasin, Mara; Cagliani, Rachele; Fumagalli, Matteo; Caputo, Domenico; Cassinotti, Andrea; Ardizzone, Sandro; Zanzottera, Milena; Bolognesi, Elisabetta; Riva, Stefania; Kanari, Yasuyoshi; Miyazawa, Masaaki; Clerici, Mario

    2011-12-01

    The human RAC2 gene encodes a small GTP-binding protein with a pivotal role in immune activation and in the induction of peripheral immune tolerance through restimulation-induced cell death (RICD). Different human pathogens target the protein product of RAC2, suggesting that the gene may be subject to natural selection, and that variants in RAC2 may affect immunological phenotypes in humans. We scanned the genomic region encompassing the entire transcription unit for the presence of putative noncoding regulatory elements conserved across mammals. This information was used to select two RAC2 gene regions and analyze their intraspecific genetic diversity. Results suggest that a region covering the 3' untranslated region has been a target of multiallelic balancing selection (or diversifying selection), and three major RAC2 haplogroups occur in human populations. Haplotypes belonging to one of these clades are associated with increased susceptibility to multiple sclerosis (P = 0.022) and earlier onset of disease symptoms (P = 0.025). This same haplogroup is significantly more common in patients with Crohn's disease compared with healthy controls (P = 0.048). These data reinforce recent evidences that susceptibility alleles/haplotypes are shared among multiple autoimmune disorders and support a causal "role for RAC2" variants in the pathogenesis of autoimmune diseases. Other genes with a role in RICD have previously been associated with autoimmunity in humans, suggesting that this pathway and RAC2 may represent novel therapeutic targets in autoimmune disorders. PMID:21680873

  11. RotundRacGAP functions with Ras during spermatogenesis and retinal differentiation in Drosophila melanogaster.

    PubMed

    Bergeret, E; Pignot-Paintrand, I; Guichard, A; Raymond, K; Fauvarque, M O; Cazemajor, M; Griffin-Shea, R

    2001-09-01

    Our analysis of rotund (rn) null mutations in Drosophila melanogaster revealed that deletion of the rn locus affects both spermatid and retinal differentiation. In the male reproductive system, the absence of RnRacGAP induced small testes, empty seminal vesicles, short testicular cysts, reduced amounts of interspermatid membrane, the absence of individualization complexes, and incomplete mitochondrial condensation. Flagellar growth continued within the short rn null cysts to produce large bulbous terminations of intertwined mature flagella. Organization of the retina was also severely perturbed as evidenced by grossly misshapen ommatidia containing reduced numbers of photoreceptor and pigment cells. These morphological phenotypes were rescued by genomic rnRacGAP transgenes, demonstrating that RnRacGAP function is critical to spermatid and retinal differentiation. The testicular phenotypes were suppressed by heterozygous hypomorphic mutations in the Dras1 and drk genes, indicating cross talk between RacGAP-regulated signaling and that of the Ras pathway. The observed genetic interactions are consistent with a model in which Rac signaling is activated by Ras and negatively regulated by RnRacGAP during spermatid differentiation. RnRacGAP and Ras cross talk also operated during retinal differentiation; however, while the heterozygous hypomorphic drk mutation continued to act as a suppressor of the rn null mutation, the heterozygous hypomorphic Dras1 mutation induced novel retinal phenotypes. PMID:11509670

  12. Photoconductivity of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    Kuriyama, K.; Dresselhaus, M. S.

    1990-08-01

    The photoconductivity is measured on a high-surface-area disordered carbon material, namely activated carbon fibers, to investigate their electronic properties. Measurements of decay time, recombination kinetics and temperature dependence of the photoconductivity generally reflect the electronic properties of a material. The material studied in this paper is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000--2000m{sup 2}/g. Our preliminary thermopower measurements suggest that this carbon material is a p-type semiconductor with an amorphous-like microstructure. The intrinsic electrical conductivity, on the order of 20S/cm at room temperature, increases with increasing temperature in the range 30--290K. In contrast with the intrinsic conductivity, the photoconductivity in vacuum decreases with increasing temperature. The recombination kinetics changes from a monomolecular process at room temperature to a biomolecular process at low temperatures. The observed decay time of the photoconductivity is {approx equal}0.3sec. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The intrinsic carrier density and the activation energy for conduction are estimated to be {approx equal}10{sup 21}/cm{sup 3} and {approx equal}20meV, respectively. The majority of the induced photocarriers and of the intrinsic carriers are trapped, resulting in the long decay time of the photoconductivity and the positive temperature dependence of the conductivity.

  13. Catalytic Role Of Palladium And Relative Reactivity Of Substituted Chlorines During Adsorption And Treatment Of PCBs On Reactive Activated Carbon

    EPA Science Inventory

    The adsorption-mediated dechlorination of polychlorinated biphenyls (PCBs) is a unique feature of reactive activated cabon (RAC). Here, we address the RAC system, containing a tunable amount of Fe as a primary electron donor coupled with Pd as an electrochemical catalyst to pote...

  14. Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling.

    PubMed

    Walliser, Claudia; Tron, Kyrylo; Clauss, Karen; Gutman, Orit; Kobitski, Andrei Yu; Retlich, Michael; Schade, Anja; Röcker, Carlheinz; Henis, Yoav I; Nienhaus, G Ulrich; Gierschik, Peter

    2015-07-10

    The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca(2+). The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction. Here, we use a Rac-resistant mutant of PLCγ2 to functionally reconstitute cultured PLCγ2-deficient DT40 B cells and to examine the effects of the Rac-PLCγ2 interaction on BCR-mediated changes of intracellular Ca(2+) and regulation of Ca(2+)-regulated and nuclear-factor-of-activated-T-cell-regulated gene transcription at the level of single, intact B cells. The results show that the functional Rac-PLCγ2 interaction causes marked increases in the following: (i) sensitivity of B cells to BCR ligation; (ii) BCR-mediated Ca(2+) release from intracellular stores; (iii) Ca(2+) entry from the extracellular compartment; and (iv) nuclear translocation of the Ca(2+)-regulated nuclear factor of activated T cells. Hence, Rac-mediated stimulation of PLCγ2 activity serves to amplify B cell receptor-induced Ca(2+) signaling. PMID:25903139

  15. Rac1 augments Wnt signaling by stimulating β-catenin-lymphoid enhancer factor-1 complex assembly independent of β-catenin nuclear import.

    PubMed

    Jamieson, Cara; Lui, Christina; Brocardo, Mariana G; Martino-Echarri, Estefania; Henderson, Beric R

    2015-11-01

    β-Catenin transduces the Wnt signaling pathway and its nuclear accumulation leads to gene transactivation and cancer. Rac1 GTPase is known to stimulate β-catenin-dependent transcription of Wnt target genes and we confirmed this activity. Here we tested the recent hypothesis that Rac1 augments Wnt signaling by enhancing β-catenin nuclear import; however, we found that silencing/inhibition or up-regulation of Rac1 had no influence on nuclear accumulation of β-catenin. To better define the role of Rac1, we employed proximity ligation assays (PLA) and discovered that a significant pool of Rac1-β-catenin protein complexes redistribute from the plasma membrane to the nucleus upon Wnt or Rac1 activation. More importantly, active Rac1 was shown to stimulate the formation of nuclear β-catenin-lymphoid enhancer factor 1 (LEF-1) complexes. This regulation required Rac1-dependent phosphorylation of β-catenin at specific serines, which when mutated (S191A and S605A) reduced β-catenin binding to LEF-1 by up to 50%, as revealed by PLA and immunoprecipitation experiments. We propose that Rac1-mediated phosphorylation of β-catenin stimulates Wnt-dependent gene transactivation by enhancing β-catenin-LEF-1 complex assembly, providing new insight into the mechanism of cross-talk between Rac1 and canonical Wnt/β-catenin signaling. PMID:26403202

  16. Rac1 augments Wnt signaling by stimulating β-catenin–lymphoid enhancer factor-1 complex assembly independent of β-catenin nuclear import

    PubMed Central

    Jamieson, Cara; Lui, Christina; Brocardo, Mariana G.; Martino-Echarri, Estefania; Henderson, Beric R.

    2015-01-01

    ABSTRACT β-Catenin transduces the Wnt signaling pathway and its nuclear accumulation leads to gene transactivation and cancer. Rac1 GTPase is known to stimulate β-catenin-dependent transcription of Wnt target genes and we confirmed this activity. Here we tested the recent hypothesis that Rac1 augments Wnt signaling by enhancing β-catenin nuclear import; however, we found that silencing/inhibition or up-regulation of Rac1 had no influence on nuclear accumulation of β-catenin. To better define the role of Rac1, we employed proximity ligation assays (PLA) and discovered that a significant pool of Rac1–β-catenin protein complexes redistribute from the plasma membrane to the nucleus upon Wnt or Rac1 activation. More importantly, active Rac1 was shown to stimulate the formation of nuclear β-catenin–lymphoid enhancer factor 1 (LEF-1) complexes. This regulation required Rac1-dependent phosphorylation of β-catenin at specific serines, which when mutated (S191A and S605A) reduced β-catenin binding to LEF-1 by up to 50%, as revealed by PLA and immunoprecipitation experiments. We propose that Rac1-mediated phosphorylation of β-catenin stimulates Wnt-dependent gene transactivation by enhancing β-catenin–LEF-1 complex assembly, providing new insight into the mechanism of cross-talk between Rac1 and canonical Wnt/β-catenin signaling. PMID:26403202

  17. The Rac-GAP alpha2-chimaerin regulates hippocampal dendrite and spine morphogenesis.

    PubMed

    Valdez, Chris M; Murphy, Geoffrey G; Beg, Asim A

    2016-09-01

    Dendritic spines are fine neuronal processes where spatially restricted input can induce activity-dependent changes in one spine, while leaving neighboring spines unmodified. Morphological spine plasticity is critical for synaptic transmission and is thought to underlie processes like learning and memory. Significantly, defects in dendritic spine stability and morphology are common pathogenic features found in several neurodevelopmental and neuropsychiatric disorders. The remodeling of spines relies on proteins that modulate the underlying cytoskeleton, which is primarily composed of filamentous (F)-actin. The Rho-GTPase Rac1 is a major regulator of F-actin and is essential for the development and plasticity of dendrites and spines. However, the key molecules and mechanisms that regulate Rac1-dependent pathways at spines and synapses are not well understood. We have identified the Rac1-GTPase activating protein, α2-chimaerin, as a critical negative regulator of Rac1 in hippocampal neurons. The loss of α2-chimaerin significantly increases the levels of active Rac1 and induces the formation of aberrant polymorphic dendritic spines. Further, disruption of α2-chimaerin signaling simplifies dendritic arbor complexity and increases the presence of dendritic spines that appear poly-innervated. Our data suggests that α2-chimaerin serves as a "brake" to constrain Rac1-dependent signaling to ensure that the mature morphology of spines is maintained in response to network activity. PMID:27297944

  18. GABARAP proteins as scaffolds in localized TIAM1-RAC1 signaling

    PubMed Central

    Genau, Heide Marika; Behrends, Christian

    2016-01-01

    Spatially restricted signaling is a hallmark of RAC1 signaling. Recent work has uncovered a novel role of gamma-aminobutyric acid receptor-associated proteins (GABARAPs), a subfamily of human ATG8 ubiquitin-like modifiers, in providing a scaffold for recruitment of an ubiquitin E3 ligase complex to its substrate, T-lymphoma invasion and metastasis-inducing protein 1 (TIAM1), to enable ubiquitylation and thereby local control of RAC1 activity. PMID:27308540

  19. Remedial Strategies in Structural Proteomics: Expression, Purification, And Crystallization of the Vav1/Rac1 Complex

    SciTech Connect

    Brooun, A.; Foster, S.A.; Chrencik, H.E.; Chien, E.Y.T.; Kolatkar, A.R.; Streiff, M.; Ramage, P.; Widmer, H.; Weckbecker, G.; Kuhn, P.

    2007-07-03

    The signal transduction pathway involving the Vav1 guanine nucleotide exchange factor (GEF) and the Rac1 GTPase plays several key roles in the immune response mediated by the T cell receptor. Vav1 is also a unique member of the GEF family in that it contains a cysteine-rich domain (CRD) that is critical for Rac1 binding and maximal guanine nucleotide exchange activity, and thus may provide a unique protein-protein interface compared to other GEF/GTPase pairs. Here, we have applied a number of remedial structural proteomics strategies, such as construct and expression optimization, surface mutagenesis, limited proteolysis, and protein formulation to successfully express, purify, and crystallize the Vav1-DH-PH-CRD/Rac1 complex in an active conformation. We have also systematically characterized various Vav1 domains in a GEF assay and Rac1 in vitro binding experiments. In the context of Vav1-DH-PH-CRD, the zinc finger motif of the CRD is required for the expression of stable Vav1, as well as for activity in both a GEF assay and in vitro formation of a Vav1/Rac1 complex suitable for biophysical and structural characterization. Our data also indicate that the isolated CRD maintains a low level of specific binding to Rac1, appears to be folded based on 1D NMR analysis and coordinates two zinc ions based on ICP-MS analysis. The protein reagents generated here are essential tools for the determination of a three dimensional Vav1/Rac1 complex crystal structure and possibly for the identification of inhibitors of the Vav1/Rac1 protein-protein interaction with potential to inhibit lymphocyte activation.

  20. Ras, Rac1, and phosphatidylinositol-3-kinase (PI3K) signaling in nitric oxide induced endothelial cell migration.

    PubMed

    Eller-Borges, Roberta; Batista, Wagner L; da Costa, Paulo E; Tokikawa, Rita; Curcio, Marli F; Strumillo, Scheilla T; Sartori, Adriano; Moraes, Miriam S; de Oliveira, Graciele A; Taha, Murched O; Fonseca, Fábio V; Stern, Arnold; Monteiro, Hugo P

    2015-05-01

    The small GTP-binding proteins Ras and Rac1 are molecular switches exchanging GDP for GTP and converting external signals in response to a variety of stimuli. Ras and Rac1 play an important role in cell proliferation, cell differentiation, and cell migration. Rac1 is directly involved in the reorganization and changes in the cytoskeleton during cell motility. Nitric oxide (NO) stimulates the Ras - ERK1/2 MAP kinases signaling pathway and is involved in the interaction between Ras and the phosphatidyl-inositol-3 Kinase (PI3K) signaling pathway and cell migration. This study utilizes bradykinin (BK), which promotes endogenous production of NO, in an investigation of the role of NO in the activation of Rac1 in rabbit aortic endothelial cells (RAEC). NO-derived from BK stimulation of RAEC and incubation of the cells with the s-nitrosothiol S-nitrosoglutathione (GSNO) activated Rac1. NO-derived from BK stimulation promoted RAEC migration over a period of 12 h. The use of RAEC permanently transfected with the dominant negative mutant of Ras (Ras(N17)) or with the non-nitrosatable mutant of Ras (Ras(C118S)); and the use of specific inhibitors of: Ras, PI3K, and Rac1 resulted in inhibition of NO-mediated Rac1 activation. BK-stimulated s-nitrosylation of Ras in RAEC mediates Rac1 activation and cell migration. Inhibition of NO-mediated Rac1 activation resulted in inhibition of endothelial cell migration. In conclusion, the NO indirect activation of Rac1 involves the direct participation of Ras and PI3K in the migration of endothelial cells stimulated with BK. PMID:25819133

  1. Rac1 is required for Prkar1a-mediated Nf2 suppression in Schwann cell tumors

    PubMed Central

    Manchanda, Parmeet K.; Jones, Georgette N.; Lee, Audrey A.; Pringle, Daphne R.; Zhang, Mei; Yu, Lianbo; La Perle, Krista M. D.; Kirschner, Lawrence S.

    2012-01-01

    Schwannomas are peripheral nerve sheath tumors that often occur in the setting of an inherited tumor predisposition syndrome, including Neurofibromatosis Types 1 (NF1) and 2 (NF2), Familial Schwannomatosis (FS) and Carney Complex (CNC). Loss of the NF2 tumor suppressor (encoding NF2, or Merlin) is associated with upregulation of the Rac1 small GTPase, which is thought to play a key role in mediating tumor formation. In prior studies, we generated a mouse model of schwannomas by performing tissue-specific knockout of the CNC gene Prkar1a, which encodes the type 1A regulatory subunit of Protein Kinase A. These tumors exhibited down-regulation of Nf2 protein and an increase in activated Rac1. To assess the requirement for Rac1 in schwannoma formation, we generated a double knockout of Prkar1a and Rac1 in Schwann cells and monitored tumor formation. Loss of Rac1 reduced tumor formation by reducing proliferation and enhancing apoptosis. Surprisingly, the reduction of tumor formation was accompanied by re-expression of the Nf2 protein. Furthermore, activated Rac1 was able to downregulate Nf2 in vitro in a Pak-dependent manner. These in vivo data indicate that activation of Rac1 is responsible for suppression of Nf2 protein production; deficiency of Nf2 in Schwann cells leads to loss of cellular growth control and tumor formation.. Further, PKA activation through mutation in Prkar1a is sufficient to initiate Rac1 signaling, with subsequent reduction of Nf2 and schwannomagenesis. Although in vitro evidence has shown that loss of Nf2 activates Rac1, our data indicates that signaling between Nf2 and Rac1 occurs in a bidirectional fashion, and these interactions are modulated by PKA. PMID:23045281

  2. Rac1 is required for Prkar1a-mediated Nf2 suppression in Schwann cell tumors.

    PubMed

    Manchanda, P K; Jones, G N; Lee, A A; Pringle, D R; Zhang, M; Yu, L; La Perle, K M D; Kirschner, L S

    2013-07-25

    Schwannomas are peripheral nerve sheath tumors that often occur in the setting of an inherited tumor predisposition syndrome, including neurofibromatosis types 1 (NF1) and 2 (NF2), familial schwannomatosis and Carney complex. Loss of the NF2 tumor suppressor (encoding NF2, or Merlin) is associated with upregulation of the Rac1 small GTPase, which is thought to have a key role in mediating tumor formation. In prior studies, we generated a mouse model of schwannomas by performing tissue-specific knockout (KO) of the Carney complex gene Prkar1a, which encodes the type 1A regulatory subunit of protein kinase A. These tumors exhibited down-regulation of Nf2 protein and an increase in activated Rac1. To assess the requirement for Rac1 in schwannoma formation, we generated a double KO (DKO) of Prkar1a and Rac1 in Schwann cells and monitored tumor formation. Loss of Rac1 reduced tumor formation by reducing proliferation and enhancing apoptosis. Surprisingly, the reduction of tumor formation was accompanied by re-expression of the Nf2 protein. Furthermore, activated Rac1 was able to downregulate Nf2 in vitro in a Pak-dependent manner. These in vivo data indicate that activation of Rac1 is responsible for suppression of Nf2 protein production; deficiency of Nf2 in Schwann cells leads to loss of cellular growth control and tumor formation. Further, PKA activation through mutation in Prkar1a is sufficient to initiate Rac1 signaling, with subsequent reduction of Nf2 and schwannomagenesis. Although in vitro evidence has shown that loss of Nf2 activates Rac1, our data indicate that signaling between Nf2 and Rac1 occurs in a bidirectional fashion, and these interactions are modulated by PKA. PMID:23045281

  3. Regulation of Rac1 and Reactive Oxygen Species Production in Response to Infection of Gastrointestinal Epithelia

    PubMed Central

    Ablack, Amber; Hall, Emily H.; Butcher, Lindsay D.; Bhattacharyya, Asima; Eckmann, Lars; Harris, Paul R.; Das, Soumita; Ernst, Peter B.; Crowe, Sheila E.

    2016-01-01

    Generation of reactive oxygen species (ROS) during infection is an immediate host defense leading to microbial killing. APE1 is a multifunctional protein induced by ROS and after induction, protects against ROS-mediated DNA damage. Rac1 and NAPDH oxidase (Nox1) are important contributors of ROS generation following infection and associated with gastrointestinal epithelial injury. The purpose of this study was to determine if APE1 regulates the function of Rac1 and Nox1 during oxidative stress. Gastric or colonic epithelial cells (wild-type or with suppressed APE1) were infected with Helicobacter pylori or Salmonella enterica and assessed for Rac1 and NADPH oxidase-dependent superoxide production. Rac1 and APE1 interactions were measured by co-immunoprecipitation, confocal microscopy and proximity ligation assay (PLA) in cell lines or in biopsy specimens. Significantly greater levels of ROS were produced by APE1-deficient human gastric and colonic cell lines and primary gastric epithelial cells compared to control cells after infection with either gastric or enteric pathogens. H. pylori activated Rac1 and Nox1 in all cell types, but activation was higher in APE1 suppressed cells. APE1 overexpression decreased H. pylori-induced ROS generation, Rac1 activation, and Nox1 expression. We determined that the effects of APE1 were mediated through its N-terminal lysine residues interacting with Rac1, leading to inhibition of Nox1 expression and ROS generation. APE1 is a negative regulator of oxidative stress in the gastrointestinal epithelium during bacterial infection by modulating Rac1 and Nox1. Our results implicate APE1 in novel molecular interactions that regulate early stress responses elicited by microbial infections. PMID:26761793

  4. Activated, coal-based carbon foam

    DOEpatents

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2004-12-21

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  5. Activated, coal-based carbon foam

    SciTech Connect

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2009-06-09

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  6. Design of activated carbon/activated carbon asymmetric capacitors

    NASA Astrophysics Data System (ADS)

    Piñeiro-Prado, Isabel; Salinas-Torres, David; Ruiz Rosas, Ramiro; Morallon, Emilia; Cazorla-Amoros, Diego

    2016-03-01

    Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

  7. Rac2 Controls Tumor Growth, Metastasis and M1-M2 Macrophage Differentiation In Vivo

    PubMed Central

    Joshi, Shweta; Singh, Alok R.; Zulcic, Muamera; Bao, Lei; Messer, Karen; Ideker, Trey; Dutkowski, Janusz; Durden, Donald L.

    2014-01-01

    Although it is well-established that the macrophage M1 to M2 transition plays a role in tumor progression, the molecular basis for this process remains incompletely understood. Herein, we demonstrate that the small GTPase, Rac2 controls macrophage M1 to M2 differentiation and the metastatic phenotype in vivo. Using a genetic approach, combined with syngeneic and orthotopic tumor models we demonstrate that Rac2-/- mice display a marked defect in tumor growth, angiogenesis and metastasis. Microarray, RT-PCR and metabolomic analysis on bone marrow derived macrophages isolated from the Rac2-/- mice identify an important role for Rac2 in M2 macrophage differentiation. Furthermore, we define a novel molecular mechanism by which signals transmitted from the extracellular matrix via the α4β1 integrin and MCSF receptor lead to the activation of Rac2 and potentially regulate macrophage M2 differentiation. Collectively, our findings demonstrate a macrophage autonomous process by which the Rac2 GTPase is activated downstream of the α4β1 integrin and the MCSF receptor to control tumor growth, metastasis and macrophage differentiation into the M2 phenotype. Finally, using gene expression and metabolomic data from our Rac2-/- model, and information related to M1-M2 macrophage differentiation curated from the literature we executed a systems biologic analysis of hierarchical protein-protein interaction networks in an effort to develop an iterative interactome map which will predict additional mechanisms by which Rac2 may coordinately control macrophage M1 to M2 differentiation and metastasis. PMID:24770346

  8. Mercury binding on activated carbon

    SciTech Connect

    Bihter Padak; Michael Brunetti; Amanda Lewis; Jennifer Wilcox

    2006-11-15

    Density functional theory has been employed for the modeling of activated carbon (AC) using a fused-benzene ring cluster approach. Oxygen functional groups have been investigated for their promotion of effective elemental mercury binding on AC surface sites. Lactone and carbonyl functional groups yield the highest mercury binding energies. Further, the addition of halogen atoms has been considered to the modeled surface, and has been found to increase the AC's mercury adsorption capacity. The mercury binding energies increase with the addition of the following halogen atoms, F {gt} Cl {gt} Br {gt} I, with the fluorine addition being the most promising halogen for increasing mercury adsorption.

  9. Rac1 functions as a reversible tension modulator to stabilize VE-cadherin trans-interaction.

    PubMed

    Daneshjou, Nazila; Sieracki, Nathan; van Nieuw Amerongen, Geerten P; Schwartz, Martin A; Komarova, Yulia A; Malik, Asrar B; Conway, Daniel E

    2015-01-01

    The role of the RhoGTPase Rac1 in stabilizing mature endothelial adherens junctions (AJs) is not well understood. In this paper, using a photoactivatable probe to control Rac1 activity at AJs, we addressed the relationship between Rac1 and the dynamics of vascular endothelial cadherin (VE-cadherin). We demonstrated that Rac1 activation reduced the rate of VE-cadherin dissociation, leading to increased density of VE-cadherin at AJs. This response was coupled to a reduction in actomyosin-dependent tension across VE-cadherin adhesion sites. We observed that inhibiting myosin II directly or through photo-release of the caged Rho kinase inhibitor also reduced the rate of VE-cadherin dissociation. Thus, Rac1 functions by stabilizing VE-cadherin trans-dimers in mature AJs by counteracting the actomyosin tension. The results suggest a new model of VE-cadherin adhesive interaction mediated by Rac1-induced reduction of mechanical tension at AJs, resulting in the stabilization of VE-cadherin adhesions. PMID:25559184

  10. Regulation of Pathogenic Spore Germination by CgRac1 in the Fungal Plant Pathogen Colletotrichum gloeosporioides ▿ ‡

    PubMed Central

    Nesher, Iris; Minz, Anna; Kokkelink, Leonie; Tudzynski, Paul; Sharon, Amir

    2011-01-01

    Colletotrichum gloeosporioides is a facultative plant pathogen: it can live as a saprophyte on dead organic matter or as a pathogen on a host plant. Different patterns of conidial germination have been recognized under saprophytic and pathogenic conditions, which also determine later development. Here we describe the role of CgRac1 in regulating pathogenic germination. The hallmark of pathogenic germination is unilateral formation of a single germ tube following the first cell division. However, transgenic strains expressing a constitutively active CgRac1 (CA-CgRac1) displayed simultaneous formation of two germ tubes, with nuclei continuing to divide in both cells after the first cell division. CA-CgRac1 also caused various other abnormalities, including difficulties in establishing and maintaining cell polarity, reduced conidial and hyphal adhesion, and formation of immature appressoria. Consequently, CA-CgRac1 isolates were completely nonpathogenic. Localization studies with cyan fluorescent protein (CFP)-CgRac1 fusion protein showed that the CgRac1 protein is abundant in conidia and in hyphal tips. Although the CFP signal was equally distributed in both cells of a germinating conidium, reactive oxygen species accumulated only in the cell that produced a germ tube, indicating that CgRac1 was active only in the germinating cell. Collectively, our results show that CgRac1 is a major regulator of asymmetric development and that it is involved in the regulation of both morphogenesis and nuclear division. Modification of CgRac1 activity disrupts the morphogenetic program and prevents fungal infection. PMID:21460190

  11. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyan, M.; Lafferty, C.; Kimber, G.

    1996-10-01

    This work describes development of a series of novel activated carbon materials and their testing for possible water treatment applications by studying the adsorption of sodium pentachlorphenolate, PCP (a common herbicide/wood preservative). Although the application of activated carbons is an established technology for the treatment of public water supplies, there is a growing need for materials with higher selectivity and adsorptive capacities as well as high abrasion resistance. The materials that will be discussed include extruded wood-derived carbons with novel pore size distributions and high hardness, as well as activated carbon fiber composites. Comparisons will be made with commercial granular water treatment carbons.

  12. R-Ketorolac Targets Cdc42 and Rac1 and Alters Ovarian Cancer Cell Behaviors Critical for Invasion and Metastasis.

    PubMed

    Guo, Yuna; Kenney, S Ray; Muller, Carolyn Y; Adams, Sarah; Rutledge, Teresa; Romero, Elsa; Murray-Krezan, Cristina; Prekeris, Rytis; Sklar, Larry A; Hudson, Laurie G; Wandinger-Ness, Angela

    2015-10-01

    Cdc42 (cell division control protein 42) and Rac1 (Ras-related C3 botulinum toxin substrate 1) are attractive therapeutic targets in ovarian cancer based on established importance in tumor cell migration, adhesion, and invasion. Despite a predicted benefit, targeting GTPases has not yet been translated to clinical practice. We previously established that Cdc42 and constitutively active Rac1b are overexpressed in primary ovarian tumor tissues. Through high-throughput screening and computational shape homology approaches, we identified R-ketorolac as a Cdc42 and Rac1 inhibitor, distinct from the anti-inflammatory, cyclooxygenase inhibitory activity of S-ketorolac. In the present study, we establish R-ketorolac as an allosteric inhibitor of Cdc42 and Rac1. Cell-based assays validate R-ketorolac activity against Cdc42 and Rac1. Studies on immortalized human ovarian adenocarcinoma cells (SKOV3ip) and primary patient-derived ovarian cancer cells show that R-ketorolac is a robust inhibitor of growth factor or serum-dependent Cdc42 and Rac1 activation with a potency and cellular efficacy similar to small-molecule inhibitors of Cdc42 (CID2950007/ML141) and Rac1 (NSC23766). Furthermore, GTPase inhibition by R-ketorolac reduces downstream p21-activated kinases (PAK1/PAK2) effector activation by >80%. Multiple assays of cell behavior using SKOV3ip and primary patient-derived ovarian cancer cells show that R-ketorolac significantly inhibits cell adhesion, migration, and invasion. In summary, we provide evidence for R-ketorolac as a direct inhibitor of Cdc42 and Rac1 that is capable of modulating downstream GTPase-dependent, physiologic responses, which are critical to tumor metastasis. Our findings demonstrate the selective inhibition of Cdc42 and Rac1 GTPases by an FDA-approved drug, racemic ketorolac, that can be used in humans. PMID:26206334

  13. Preclinical Development of Novel Rac1-GEF Signaling Inhibitors using a Rational Design Approach in Highly Aggressive Breast Cancer Cell Lines

    PubMed Central

    Cardama, Georgina A; Comin, Maria J; Hornos, Leandro; Gonzalez, Nazareno; Defelipe, Lucas; Turjanski, Adrian G; Alonso, Daniel F; Gomez, Daniel E; Menna, Pablo Lorenzano

    2014-01-01

    Rho GTPases play a key role in the regulation of multiple essential cellular processes, including actin dynamics, gene transcription and cell cycle progression. Aberrant activation of Rac1, a member of Rho family of small GTPases, is associated with tumorigenesis, cancer progression, invasion and metastasis. Particularly, Rac1 is overexpressed and hyperactivated in highly aggressive breast cancer. Thus, Rac1 appears to be a promising and relevant target for the development of novel anticancer drugs. We identified the novel Rac1 inhibitor ZINC69391 through a docking-based virtual library screening targeting Rac1 activation by GEFs. This compound was able to block Rac1 interaction with its GEF Tiam1, prevented EGF-induced Rac1 activation and inhibited cell proliferation, cell migration and cell cycle progression in highly aggressive breast cancer cell lines. Moreover, ZINC69391 showed an in vivo antimetastatic effect in a syngeneic animal model. We further developed the novel analog 1A-116 by rational design and showed to be specific and more potent than the parental compound in vitro and interfered Rac1-P-Rex1 interaction. We also showed an enhanced in vivo potency of 1A-116 analog. These results show that we have developed novel Rac1 inhibitors that may be used as a novel anticancer therapy. PMID:24066799

  14. SORPTION OF ELEMENTAL MERCURY BY ACTIVATED CARBONS

    EPA Science Inventory

    The mechanisms and rate of elemental mercury (HgO) capture by activated carbons have been studied using a bench-scale apparatus. Three types of activated carbons, two of which are thermally activated (PC-100 and FGD) and one with elemental sulfur (S) impregnated in it (HGR), were...

  15. Regulation of Adherens Junctions in Trabecular Meshwork Cells by Rac GTPase and their influence on Intraocular Pressure

    PubMed Central

    Pattabiraman, Padmanabhan P; Epstein, David L; Rao, Ponugoti Vasantha

    2013-01-01

    Intercellular adherens junctions and cell-extracellular matrix interactions are presumed to influence aqueous humor (AH) drainage via the conventional route, however, their direct role in modulation of intraocular pressure (IOP) is not well understood. Here, we investigated the role of Rac GTPase signaling in basal and growth factor-induced formation of adherens junctions in human trabecular meshwork (HTM) cells as compared to human umbilical vascular endothelial cells, and evaluated the effects of inhibition of Rac GTPase activity on IOP in rabbits. Expression of a constitutively active Rac1 GTPase or treatment with platelet derived growth factor (PDGF), a known activator of Rac GTPase, induced formation of β-catenin-based adherens junctions, actin cytoskeletal reorganization and membrane ruffle in HTM cells. In contrast, treatment of HTM cells with inhibitors of Rac GTPase caused cell-cell separation, a decrease in adherens junctions, and reorganization of actin stress fibers to the cell cortical regions and focal adhesion to the cell leading edges. Both, constitutively active Rac1 and PDGF stimulated generation of Reactive Oxygen Species (ROS) in HTM cells, and ROS were found to increase adherens junction formation and transendothelial electrical resistance (TEER) in HTM cells. Topical application of Rac GTPase inhibitors (EHT1864 and NSC23766), however, only marginally influenced IOP in rabbit eyes. Taken together, these data reveal that while Rac GTPase signaling plays a significant role in regulation of adherens junctions, ROS production and TEER in cells of the AH outflow pathway, Rac inhibitors showed only a marginal influence on IOP in live rabbits. PMID:24932460

  16. Regulation of Adherens Junctions in Trabecular Meshwork Cells by Rac GTPase and their influence on Intraocular Pressure.

    PubMed

    Pattabiraman, Padmanabhan P; Epstein, David L; Rao, Ponugoti Vasantha

    2013-06-01

    Intercellular adherens junctions and cell-extracellular matrix interactions are presumed to influence aqueous humor (AH) drainage via the conventional route, however, their direct role in modulation of intraocular pressure (IOP) is not well understood. Here, we investigated the role of Rac GTPase signaling in basal and growth factor-induced formation of adherens junctions in human trabecular meshwork (HTM) cells as compared to human umbilical vascular endothelial cells, and evaluated the effects of inhibition of Rac GTPase activity on IOP in rabbits. Expression of a constitutively active Rac1 GTPase or treatment with platelet derived growth factor (PDGF), a known activator of Rac GTPase, induced formation of β-catenin-based adherens junctions, actin cytoskeletal reorganization and membrane ruffle in HTM cells. In contrast, treatment of HTM cells with inhibitors of Rac GTPase caused cell-cell separation, a decrease in adherens junctions, and reorganization of actin stress fibers to the cell cortical regions and focal adhesion to the cell leading edges. Both, constitutively active Rac1 and PDGF stimulated generation of Reactive Oxygen Species (ROS) in HTM cells, and ROS were found to increase adherens junction formation and transendothelial electrical resistance (TEER) in HTM cells. Topical application of Rac GTPase inhibitors (EHT1864 and NSC23766), however, only marginally influenced IOP in rabbit eyes. Taken together, these data reveal that while Rac GTPase signaling plays a significant role in regulation of adherens junctions, ROS production and TEER in cells of the AH outflow pathway, Rac inhibitors showed only a marginal influence on IOP in live rabbits. PMID:24932460

  17. Studies and characterisations of various activated carbons used for carbon/carbon supercapacitors

    NASA Astrophysics Data System (ADS)

    Gamby, J.; Taberna, P. L.; Simon, P.; Fauvarque, J. F.; Chesneau, M.

    Various activated carbons from the PICA Company have been tested in supercapacitor cells in order to compare their performances. The differences measured in terms of specific capacitance and cell resistance are presented. Porosity measurements made on activated carbon powders and electrode allowed a better understanding of the electrochemical behaviour of these activated carbons. In this way, the PICACTIF SC carbon was found to be an interesting active material for supercapacitors, with a specific capacitance as high as 125 F/g.

  18. RAC/ROP GTPases and auxin signaling.

    PubMed

    Wu, Hen-ming; Hazak, Ora; Cheung, Alice Y; Yalovsky, Shaul

    2011-04-01

    Auxin functions as a key morphogen in regulating plant growth and development. Studies on auxin-regulated gene expression and on the mechanism of polar auxin transport and its asymmetric distribution within tissues have provided the basis for realizing the molecular mechanisms underlying auxin function. In eukaryotes, members of the Ras and Rho subfamilies of the Ras superfamily of small GTPases function as molecular switches in many signaling cascades that regulate growth and development. Plants do not have Ras proteins, but they contain Rho-like small G proteins called RACs or ROPs that, like fungal and metazoan Rhos, are regulators of cell polarity and may also undertake some Ras functions. Here, we discuss the advances made over the last decade that implicate RAC/ROPs as mediators for auxin-regulated gene expression, rapid cell surface-located auxin signaling, and directional auxin transport. We also describe experimental data indicating that auxin-RAC/ROP crosstalk may form regulatory feedback loops and theoretical modeling that attempts to connect local auxin gradients with RAC/ROP regulation of cell polarity. We hope that by discussing these experimental and modeling studies, this perspective will stimulate efforts to further refine our understanding of auxin signaling via the RAC/ROP molecular switch. PMID:21478442

  19. Distinct predictive performance of Rac1 and Cdc42 in cell migration

    PubMed Central

    Yamao, Masataka; Naoki, Honda; Kunida, Katsuyuki; Aoki, Kazuhiro; Matsuda, Michiyuki; Ishii, Shin

    2015-01-01

    We propose a new computation-based approach for elucidating how signaling molecules are decoded in cell migration. In this approach, we performed FRET time-lapse imaging of Rac1 and Cdc42, members of Rho GTPases which are responsible for cell motility, and quantitatively identified the response functions that describe the conversion from the molecular activities to the morphological changes. Based on the identified response functions, we clarified the profiles of how the morphology spatiotemporally changes in response to local and transient activation of Rac1 and Cdc42, and found that Rac1 and Cdc42 activation triggers laterally propagating membrane protrusion. The response functions were also endowed with property of differentiator, which is beneficial for maintaining sensitivity under adaptation to the mean level of input. Using the response function, we could predict the morphological change from molecular activity, and its predictive performance provides a new quantitative measure of how much the Rho GTPases participate in the cell migration. Interestingly, we discovered distinct predictive performance of Rac1 and Cdc42 depending on the migration modes, indicating that Rac1 and Cdc42 contribute to persistent and random migration, respectively. Thus, our proposed predictive approach enabled us to uncover the hidden information processing rules of Rho GTPases in the cell migration. PMID:26634649

  20. 75 FR 54297 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-07

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  1. 75 FR 27703 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  2. 76 FR 2883 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of Meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  3. 76 FR 14897 - Humboldt County Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt County Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt County Resource Advisory Committee (RAC) will meet in...

  4. 75 FR 36061 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  5. 75 FR 43140 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-23

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  6. 76 FR 9540 - Humboldt County Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt County Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt County Resource Advisory Committee (RAC) will meet in...

  7. 75 FR 69620 - Humboldt Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Forest Service Humboldt Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Humboldt Resource Advisory Committee (RAC) will meet in Eureka, California....

  8. Reconstitution of ST2 (IL-1R4) specific for IL-33 activity; no suppression by IL-1Ra though a common chain IL-1R3 (IL-1RAcP) shared with IL-1.

    PubMed

    Jo, Seunghyun; Kim, Eunsom; Kwak, Areum; Lee, Jungmin; Hong, Jaewoo; Lee, Jongho; Youn, Sulah; Bae, Suyoung; Kim, Busun; Ryoo, Soyoon; Kang, Tae-Bong; Her, Erk; Choi, Dong-Ki; Kim, Yong-Sung; Lee, Youngmin; Jhun, Hyunjhung; Kim, Soohyun

    2016-07-01

    Interleukin-33 (IL-33) receptors are composed of ST2 (also known as IL-1R4), a ligand binding chain, and IL-1 receptor accessory protein (IL-1RAcP, also known as IL-1R3), a signal transducing chain. IL-1R3 is a common receptor for IL-1α, and IL-1β, IL-33, and three IL-36 isoforms. A549 human lung epithelial cells are highly sensitive to IL-1α and IL-1β but not respond to IL-33. The lack of responsiveness to IL-33 is due to ST2 expression. ST2 was stably transfected into A549 cells to reconstitute its activity. RT-PCR and FACS analysis confirmed ST2 expression on the cell surface of A549/ST2 cells. Upon IL-33 stimulation, A549/ST2 cells induced IL-8 and IL-6 production in a dose dependent manner while A549/mock cells remained unresponsive. There was no difference in IL-1α and IL-1β activity in A549/ST2 cells compared to A549/mock cells despite the fact that IL-33 shares IL-1R3 with IL-1α/β. IL-33 activated inflammatory signaling molecules in a time- and dose-dependent manner. Anti-ST2 antibody and soluble recombinant ST2-Fc abolished IL-33-induced IL-6 and IL-8 production in A549/ST2 cells but the IL-1 receptor antagonist failed to block IL-33-induced cytokines. This result demonstrates for the first time the reconstitution of ST2 in A549 human lung epithelial cell line and verified its function in IL-33-mediated cytokine production and signal transduction. PMID:27031441

  9. CD81 regulates cell migration through its association with Rac GTPase.

    PubMed

    Tejera, Emilio; Rocha-Perugini, Vera; López-Martín, Soraya; Pérez-Hernández, Daniel; Bachir, Alexia I; Horwitz, Alan Rick; Vázquez, Jesús; Sánchez-Madrid, Francisco; Yáñez-Mo, María

    2013-02-01

    CD81 is a member of the tetraspanin family that has been described to have a key role in cell migration of tumor and immune cells. To unravel the mechanisms of CD81-regulated cell migration, we performed proteomic analyses that revealed an interaction of the tetraspanin C-terminal domain with the small GTPase Rac. Direct interaction was confirmed biochemically. Moreover, microscopy cross-correlation analysis demonstrated the in situ integration of both molecules into the same molecular complex. Pull-down experiments revealed that CD81-Rac interaction was direct and independent of Rac activation status. Knockdown of CD81 resulted in enhanced protrusion rate, altered focal adhesion formation, and decreased cell migration, correlating with increased active Rac. Reexpression of wild-type CD81, but not its truncated form lacking the C-terminal cytoplasmic domain, rescued these effects. The phenotype of CD81 knockdown cells was mimicked by treatment with a soluble peptide with the C-terminal sequence of the tetraspanin. Our data show that the interaction of Rac with the C-terminal cytoplasmic domain of CD81 is a novel regulatory mechanism of the GTPase activity turnover. Furthermore, they provide a novel mechanism for tetraspanin-dependent regulation of cell motility and open new avenues for tetraspanin-targeted reagents by the use of cell-permeable peptides. PMID:23264468

  10. CD81 regulates cell migration through its association with Rac GTPase

    PubMed Central

    Tejera, Emilio; Rocha-Perugini, Vera; López-Martín, Soraya; Pérez-Hernández, Daniel; Bachir, Alexia I.; Horwitz, Alan Rick; Vázquez, Jesús; Sánchez-Madrid, Francisco; Yáñez-Mo, María

    2013-01-01

    CD81 is a member of the tetraspanin family that has been described to have a key role in cell migration of tumor and immune cells. To unravel the mechanisms of CD81-regulated cell migration, we performed proteomic analyses that revealed an interaction of the tetraspanin C-terminal domain with the small GTPase Rac. Direct interaction was confirmed biochemically. Moreover, microscopy cross-correlation analysis demonstrated the in situ integration of both molecules into the same molecular complex. Pull-down experiments revealed that CD81-Rac interaction was direct and independent of Rac activation status. Knockdown of CD81 resulted in enhanced protrusion rate, altered focal adhesion formation, and decreased cell migration, correlating with increased active Rac. Reexpression of wild-type CD81, but not its truncated form lacking the C-terminal cytoplasmic domain, rescued these effects. The phenotype of CD81 knockdown cells was mimicked by treatment with a soluble peptide with the C-terminal sequence of the tetraspanin. Our data show that the interaction of Rac with the C-terminal cytoplasmic domain of CD81 is a novel regulatory mechanism of the GTPase activity turnover. Furthermore, they provide a novel mechanism for tetraspanin-dependent regulation of cell motility and open new avenues for tetraspanin-targeted reagents by the use of cell-permeable peptides. PMID:23264468

  11. The Rac1 Inhibitor NSC23766 Suppresses CREB Signaling by Targeting NMDA Receptor Function

    PubMed Central

    Hou, Hailong; Chávez, Andrés E.; Wang, Chih-Chieh; Yang, Hongtian; Gu, Hua; Siddoway, Benjamin A.; Hall, Benjamin J.; Castillo, Pablo E.

    2014-01-01

    NMDA receptor signaling plays a complex role in CREB activation and CREB-mediated gene transcription, depending on the subcellular location of NMDA receptors, as well as how strongly they are activated. However, it is not known whether Rac1, the prototype of Rac GTPase, plays a role in neuronal CREB activation induced by NMDA receptor signaling. Here, we report that NSC23766, a widely used specific Rac1 inhibitor, inhibits basal CREB phosphorylation at S133 (pCREB) and antagonizes changes in pCREB levels induced by NMDA bath application in rat cortical neurons. Unexpectedly, we found that NSC23766 affects the levels of neuronal pCREB in a Rac1-independent manner. Instead, our results indicate that NSC23766 can directly regulate NMDA receptors as indicated by their strong effects on both exogenous and synaptically evoked NMDA receptor-mediated currents in mouse and rat neurons, respectively. Our findings strongly suggest that Rac1 does not affect pCREB signaling in cortical neurons and reveal that NSC23766 could be a novel NMDA receptor antagonist. PMID:25319697

  12. Preparation of activated carbon by chemical activation under vacuum.

    PubMed

    Juan, Yang; Ke-Qiang, Qiu

    2009-05-01

    Activated carbons especially used for gaseous adsorption were prepared from Chinesefir sawdust by zinc chloride activation under vacuum condition. The micropore structure, adsorption properties, and surface morphology of activated carbons obtained under atmosphere and vacuum were investigated. The prepared activated carbons were characterized by SEM, FTIR, and nitrogen adsorption. It was found that the structure of the starting material is kept after activation. The activated carbon prepared under vacuum exhibited higher values of the BET surface area (up to 1079 m2 g(-1)) and total pore volume (up to 0.5665 cm3 g(-1)) than those of the activated carbon obtained under atmosphere. This was attributed to the effect of vacuum condition that reduces oxygen in the system and limits the secondary reaction of the organic vapor. The prepared activated carbon has well-developed microstructure and high microporosity. According to the data obtained, Chinese fir sawdust is a suitable precursor for activated carbon preparation. The obtained activated carbon could be used as a low-cost adsorbent with favorable surface properties. Compared with the traditional chemical activation, vacuum condition demands less energy consumption, simultaneity, and biomass-oil is collected in the procedure more conveniently. FTIR analysis showed that heat treatment would result in the aromatization of the carbon structure. PMID:19534162

  13. RAC1 inhibition as a therapeutic target for gefitinib-resistant non-small-cell lung cancer

    PubMed Central

    Kaneto, Naoki; Yokoyama, Satoru; Hayakawa, Yoshihiro; Kato, Shinichiro; Sakurai, Hiroaki; Saiki, Ikuo

    2014-01-01

    Although epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (EGFR-TKI), including gefitinib, provide a significant clinical benefit in non-small-cell lung cancer (NSCLC) patients, the acquisition of drug resistance has been known to limit the efficacy of EGFR-TKI therapy. In this study, we demonstrated the involvement of EGF-EGFR signaling in NSCLC cell migration and the requirement of RAC1 in EGFR-mediated progression of NSCLC. We showed the significant role of RAC1 pathway in the cell migration or lamellipodia formation by using gene silencing of RAC1 or induction of constitutive active RAC1 in EGFR-mutant NSCLC cells. Importantly, the RAC1 inhibition suppressed EGFR-mutant NSCLC cell migration and growth in vitro, and growth in vivo even in the gefitinib-resistant cells. In addition, these suppressions by RAC1 inhibition were mediated through MEK or PI3K independent mechanisms. Collectively, these results open up a new opportunity to control the cancer progression by targeting the RAC1 pathway to overcome the resistance to EGFR-TKI in NSCLC patients. PMID:24750242

  14. Structural and functional regulation of tight junctions by RhoA and Rac1 small GTPases.

    PubMed

    Jou, T S; Schneeberger, E E; Nelson, W J

    1998-07-13

    Tight junctions (TJ) govern ion and solute diffusion through the paracellular space (gate function), and restrict mixing of membrane proteins and lipids between membrane domains (fence function) of polarized epithelial cells. We examined roles of the RhoA and Rac1 GTPases in regulating TJ structure and function in MDCK cells using the tetracycline repressible transactivator to regulate RhoAV14, RhoAN19, Rac1V12, and Rac1N17 expression. Both constitutively active and dominant negative RhoA or Rac1 perturbed TJ gate function (transepithelial electrical resistance, tracer diffusion) in a dose-dependent and reversible manner. Freeze-fracture EM and immunofluoresence microscopy revealed abnormal TJ strand morphology and protein (occludin, ZO-1) localization in RhoAV14 and Rac1V12 cells. However, TJ strand morphology and protein localization appeared normal in RhoAN19 and Rac1N17 cells. All mutant GTPases disrupted the fence function of the TJ (interdomain diffusion of a fluorescent lipid), but targeting and organization of a membrane protein in the apical membrane were unaffected. Expression levels and protein complexes of occludin and ZO-1 appeared normal in all mutant cells, although ZO-1 was more readily solubilized from RhoAV14-expressing cells with Triton X-100. These results show that RhoA and Rac1 regulate gate and fence functions of the TJ, and play a role in the spatial organization of TJ proteins at the apex of the lateral membrane. PMID:9660866

  15. 76 FR 20942 - Elko County Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-14

    ... Forest Service Elko County Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Elko County Resource Advisory Committee (RAC) will hold its first meeting... committee members; (4) Selection of RAC Committee Chairman; (5) Overview of project selection process;...

  16. Rac1 at the crossroad of actin dynamics and neuroinflammation in Amyotrophic Lateral Sclerosis

    PubMed Central

    D’Ambrosi, Nadia; Rossi, Simona; Gerbino, Valeria; Cozzolino, Mauro

    2014-01-01

    Rac1 is a major player of the Rho family of small GTPases that controls multiple cell signaling pathways, such as the organization of cytoskeleton (including adhesion and motility), cell proliferation, apoptosis and activation of immune cells. In the nervous system, in particular, Rac1 GTPase plays a key regulatory function of both actin and microtubule cytoskeletal dynamics and thus it is central to axonal growth and stability, as well as dendrite and spine structural plasticity. Rac1 is also a crucial regulator of NADPH-dependent membrane oxidase (NOX), a prominent source of reactive oxygen species (ROS), thus having a central role in the inflammatory response and neurotoxicity mediated by microglia cells in the nervous system. As such, alterations in Rac1 activity might well be involved in the processes that give rise to Amyotrophic Lateral Sclerosis (ALS), a complex syndrome where cytoskeletal disturbances in motor neurons and redox alterations in the inflammatory compartment play pivotal and synergic roles in the final disease outcomes. Here we will discuss the genetic and mechanistic evidence indicating the relevance of Rac1 dysregulation in the pathogenesis of ALS. PMID:25249940

  17. Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon

    SciTech Connect

    Abdullah, N.; Muhammad, I. S.; Hamid, S. B. Abd.; Rinaldi, A.; Su, D. S.; Schlogl, R.

    2009-06-01

    Carbon-carbon composite of activated carbon and carbon nanofibers have been synthesized by growing Carbon nanofiber (CNF) on Palm shell-based Activated carbon (AC) with Ni catalyst. The composites are in an agglomerated shape due to the entanglement of the defective CNF between the AC particles forming a macroscopic body. The macroscopic size will allow the composite to be used as a stabile catalyst support and liquid adsorbent. The preparation of CNT/AC nanocarbon was initiated by pre-treating the activated carbon with nitric acid, followed by impregnation of 1 wt% loading of nickel (II) nitrate solutions in acetone. The catalyst precursor was calcined and reduced at 300 deg. C for an hour in each step. The catalytic growth of nanocarbon in C{sub 2}H{sub 4}/H{sub 2} was carried out at temperature of 550 deg. C for 2 hrs with different rotating angle in the fluidization system. SEM and N{sub 2} isotherms show the level of agglomeration which is a function of growth density and fluidization of the system. The effect of fluidization by rotating the reactor during growth with different speed give a significant impact on the agglomeration of the final CNF/AC composite and thus the amount of CNFs produced. The macrostructure body produced in this work of CNF/AC composite will have advantages in the adsorbent and catalyst support application, due to the mechanical and chemical properties of the material.

  18. TGFbeta1-induced aortic endothelial morphogenesis requires signaling by small GTPases Rac1 and RhoA.

    PubMed

    Varon, Christine; Basoni, Caroline; Reuzeau, Edith; Moreau, Violaine; Kramer, I Jsbrand; Génot, Elisabeth

    2006-11-01

    TGFbeta is a potent regulator of cell differentiation in many cell types. On aortic endothelial cells, TGFbeta1 displays angiogenic properties in inducing capillary-like tube formation in collagen I gels, in vitro. We investigated cytoskeletal changes that precede tube formation and related these alterations to the effects of TGFbeta1 on the activation state of members of the RhoGTPase family. TGFbeta1 promotes cell elongation and stress fiber formation in aortic endothelial cells. Using cell lines with inducible expression of Rac1 mutants, we show that these events are mimicked by expression of dominant-negative Rac1 whereas the constitutively active mutant prevents the TGFbeta1-mediated change of phenotype. Although TGFbeta1 induces an initial rise in the Rac1-GTP content, this phase is followed by a prolonged loss of the active form. In contrast, RhoA activity increases progressively and reaches a plateau when Rac1-GTP is no longer detectable. Prolonged inhibition of Rac1 appears necessary and sufficient for the increase in RhoA-GTP. In situ examination of Rho activity in TGFbeta1-treated cells provides evidence that active RhoA relocalizes to the tips of elongated cells. Inhibiting the Rho effector ROCK abrogates tube formation. Thus, Rac1 and RhoA are regulated by TGFbeta1 in the process of endothelial tube formation in collagen I gels. PMID:16978608

  19. Making Activated Carbon by Wet Pressurized Pyrolysis

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Pisharody, Suresh; Wignarajah, K.; Moran, Mark

    2006-01-01

    A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams. Activated carbon is highly porous and has a large surface area. The surface area depends strongly on the raw material and the production process. Coconut shells and bituminous coal are the primary raw materials that, until now, were converted into activated carbon of commercially acceptable quality by use of traditional production processes that involve activation by use of steam or carbon dioxide. In the wet pressurized pyrolysis process, the plant material is subjected to high pressure and temperature in an aqueous medium in the absence of oxygen for a specified amount of time to break carbon-oxygen bonds in the organic material and modify the structure of the material to obtain large surface area. Plant materials that have been used in demonstrations of the process include inedible parts of wheat, rice, potato, soybean, and tomato plants. The raw plant material is ground and mixed with a specified proportion of water. The mixture is placed in a stirred autoclave, wherein it is pyrolized at a temperature between 450 and 590 F (approximately between 230 and 310 C) and a pressure between 1 and 1.4 kpsi (approximately between 7 and 10 MPa) for a time between 5 minutes and 1 hour. The solid fraction remaining after wet carbonization is dried, then activated at a temperature of 500 F (260 C) in nitrogen gas. The activated carbon thus produced is comparable to commercial activated carbon. It can be used to adsorb oxides of sulfur, oxides of nitrogen, and trace amounts of hydrocarbons, any or all of which can be present in flue gas. Alternatively, the dried solid fraction can be used, even without the activation treatment, to absorb

  20. Rac1 Modulates Stimulus-evoked Ca2+ Release in Neuronal Growth Cones via Parallel Effects on Microtubule/Endoplasmic Reticulum Dynamics and Reactive Oxygen Species Production

    PubMed Central

    Zhang, Xiao-Feng

    2009-01-01

    The small G protein Rac regulates cytoskeletal protein dynamics in neuronal growth cones and has been implicated in axon growth, guidance, and branching. Intracellular Ca2+ is another well known regulator of growth cone function; however, effects of Rac activity on intracellular Ca2+ metabolism have not been well characterized. Here, we investigate how Rac1 activity affects release of Ca2+ from intracellular endoplasmic reticulum (ER) stores stimulated by application of serotonin (5-hydroxytriptamine). We also address how Rac1 effects on microtubule assembly dynamics affect distribution of Ca2+ release sites. Multimode fluorescent microscopy was used to correlate microtubule and ER behavior, and ratiometric imaging was used to assess intracellular Ca2+ dynamics. We report that Rac1 activity both promotes Ca2+ release and affects its spatial distribution in neuronal growth cones. The underlying mechanism involves synergistic Rac1 effects on microtubule assembly and reactive oxygen species (ROS) production. Rac1 activity modulates Ca2+ by 1) enhancing microtubule assembly which in turn promotes spread of the ER-based Ca2+ release machinery into the growth cone periphery, and 2) by increasing ROS production which facilitated inositol 1,4,5-trisphosphate-dependent Ca2+ release. These results cast Rac1 as a key modulator of intracellular Ca2+ function in the neuronal growth cone. PMID:19570918

  1. Cleavage of Hyaluronan and CD44 Adhesion Molecule Regulate Astrocyte Morphology via Rac1 Signalling

    PubMed Central

    Konopka, Anna; Zeug, Andre; Skupien, Anna; Kaza, Beata; Mueller, Franziska; Chwedorowicz, Agnieszka; Ponimaskin, Evgeni; Wilczynski, Grzegorz M.; Dzwonek, Joanna

    2016-01-01

    Communication of cells with their extracellular environment is crucial to fulfill their function in physiological and pathophysiological conditions. The literature data provide evidence that such a communication is also important in case of astrocytes. Mechanisms that contribute to the interaction between astrocytes and extracellular matrix (ECM) proteins are still poorly understood. Hyaluronan is the main component of ECM in the brain, where its major receptor protein CD44 is expressed by a subset of astrocytes. Considering the fact that functions of astrocytes are tightly coupled with changes in their morphology (e.g.: glutamate clearance in the synaptic cleft, migration, astrogliosis), we investigated the influence of hyaluronan cleavage by hyaluronidase, knockdown of CD44 by specific shRNA and CD44 overexpression on astrocyte morphology. Our results show that hyaluronidase treatment, as well as knockdown of CD44, in astrocytes result in a “stellate”-like morphology, whereas overexpression of CD44 causes an increase in cell body size and changes the shape of astrocytes into flattened cells. Moreover, as a dynamic reorganization of the actin cytoskeleton is supposed to be responsible for morphological changes of cells, and this reorganization is controlled by small GTPases of the Rho family, we hypothesized that GTPase Rac1 acts as a downstream effector for hyaluronan and CD44 in astrocytes. We used FRET-based biosensor and a dominant negative mutant of Rac1 to investigate the involvement of Rac1 activity in hyaluronidase- and CD44-dependent morphological changes of astrocytes. Both, hyaluronidase treatment and knockdown of CD44, enhances Rac1 activity while overexpression of CD44 reduces the activity state in astrocytes. Furthermore, morphological changes were blocked by specific inhibition of Rac1 activity. These findings indicate for the first time that regulation of Rac1 activity is responsible for hyaluronidase and CD44-driven morphological changes of

  2. Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling*♦

    PubMed Central

    Walliser, Claudia; Tron, Kyrylo; Clauss, Karen; Gutman, Orit; Kobitski, Andrei Yu.; Retlich, Michael; Schade, Anja; Röcker, Carlheinz; Henis, Yoav I.; Nienhaus, G. Ulrich; Gierschik, Peter

    2015-01-01

    The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca2+. The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction. Here, we use a Rac-resistant mutant of PLCγ2 to functionally reconstitute cultured PLCγ2-deficient DT40 B cells and to examine the effects of the Rac-PLCγ2 interaction on BCR-mediated changes of intracellular Ca2+ and regulation of Ca2+-regulated and nuclear-factor-of-activated-T-cell-regulated gene transcription at the level of single, intact B cells. The results show that the functional Rac-PLCγ2 interaction causes marked increases in the following: (i) sensitivity of B cells to BCR ligation; (ii) BCR-mediated Ca2+ release from intracellular stores; (iii) Ca2+ entry from the extracellular compartment; and (iv) nuclear translocation of the Ca2+-regulated nuclear factor of activated T cells. Hence, Rac-mediated stimulation of PLCγ2 activity serves to amplify B cell receptor-induced Ca2+ signaling. PMID:25903139

  3. Dock10, a Cdc42 and Rac1 GEF, induces loss of elongation, filopodia, and ruffles in cervical cancer epithelial HeLa cells

    PubMed Central

    Ruiz-Lafuente, Natalia; Alcaraz-García, María-José; García-Serna, Azahara-María; Sebastián-Ruiz, Silvia; Moya-Quiles, María-Rosa; García-Alonso, Ana-María; Parrado, Antonio

    2015-01-01

    Dock10 is one of the three members of the Dock-D family of Dock proteins, a class of guanine nucleotide exchange factors (GEFs) for Rho GTPases. Its homologs Dock9 and Dock11 are Cdc42 GEFs. Dock10 is required for maintenance of rounded morphology and amoeboid-type movement. Full-length isoforms of Dock10 have been recently cloned. Here, we address GTPase specificity and GEF activity of Dock10. In order of decreasing intensity, Dock10 interacted with nucleotide-free Rac1, Cdc42, and Rac3, and more weakly with Rac2, RhoF, and RhoG. Inducible expression of Dock10 in HeLa epithelial cells promoted GEF activity on Cdc42 and Rac1, and a morphologic change in two-dimensional culture consisting in loss of cell elongation, increase of filopodia, and ruffles. Area in contact with the substrate of cells that spread with non-elongated morphology was larger in cells expressing Dock10. Inducible expression of constitutively active mutants of Cdc42 and Rac1 in HeLa cells also induced loss of elongation. However, Cdc42 induced filopodia and contraction, and Rac1 induced membrane ruffles and flattening. When co-expressed with Dock10, Cdc42 potentiated filopodia, and Rac1 potentiated ruffles. These results suggest that Dock10 functions as a dual GEF for Cdc42 and Rac1, affecting cell morphology, spreading and actin cytoskeleton protrusions of adherent HeLa cells. PMID:25862245

  4. The NKD1/Rac1 feedback loop regulates the invasion and migration ability of hepatocarcinoma cells.

    PubMed

    Li, Jie; Zhang, Sheng; Hu, Qing; Zhang, Kang; Jin, Jianbin; Zheng, Xuqing; Yin, Zhenyu; Wang, Xiaomin

    2016-01-01

    Hepatocellular carcinoma (HCC) is complicated by aggressive migration and invasion, which contribute to the increased mortality of HCC patients. The NKD1 protein is abnormally expressed in many neoplasms and plays an important role in tumor progression. However, the regulation and underlying molecular mechanisms of NKD1 in HCC cell invasion and migration remain poorly understood. In the present study, ectopic expression of NKD1 in HCC cells attenuated migration and invasion in vitro and in vivo by down-regulating Rac1 expression level and activity, which affected the HCC cell cytoskeleton and E-cadherin expression. Mechanistic studies showed that NKD1 interacted with Rac1 in the cytoplasm and promoted its degradation by the ubiquitin-proteasome pathway. Over-expression of Rac1 enhanced the transcription of the NKD1 gene and protein expression conversely owing to its negative regulation of EZH2. Analysis of clinical samples showed that abnormal expression of NKD1 and Rac1 was associated with the poor prognosis of HCC patients. In summary, our data indicate a new role for NKD1 as a regulator of HCC cell invasion and migration via a feedback loop involving Rac1. PMID:27231134

  5. The NKD1/Rac1 feedback loop regulates the invasion and migration ability of hepatocarcinoma cells

    PubMed Central

    Li, Jie; Zhang, Sheng; Hu, Qing; Zhang, Kang; Jin, Jianbin; Zheng, Xuqing; Yin, Zhenyu; Wang, Xiaomin

    2016-01-01

    Hepatocellular carcinoma (HCC) is complicated by aggressive migration and invasion, which contribute to the increased mortality of HCC patients. The NKD1 protein is abnormally expressed in many neoplasms and plays an important role in tumor progression. However, the regulation and underlying molecular mechanisms of NKD1 in HCC cell invasion and migration remain poorly understood. In the present study, ectopic expression of NKD1 in HCC cells attenuated migration and invasion in vitro and in vivo by down-regulating Rac1 expression level and activity, which affected the HCC cell cytoskeleton and E-cadherin expression. Mechanistic studies showed that NKD1 interacted with Rac1 in the cytoplasm and promoted its degradation by the ubiquitin-proteasome pathway. Over-expression of Rac1 enhanced the transcription of the NKD1 gene and protein expression conversely owing to its negative regulation of EZH2. Analysis of clinical samples showed that abnormal expression of NKD1 and Rac1 was associated with the poor prognosis of HCC patients. In summary, our data indicate a new role for NKD1 as a regulator of HCC cell invasion and migration via a feedback loop involving Rac1. PMID:27231134

  6. RhoB controls endothelial barrier recovery by inhibiting Rac1 trafficking to the cell border.

    PubMed

    Marcos-Ramiro, Beatriz; García-Weber, Diego; Barroso, Susana; Feito, Jorge; Ortega, María C; Cernuda-Morollón, Eva; Reglero-Real, Natalia; Fernández-Martín, Laura; Durán, Maria C; Alonso, Miguel A; Correas, Isabel; Cox, Susan; Ridley, Anne J; Millán, Jaime

    2016-05-01

    Endothelial barrier dysfunction underlies chronic inflammatory diseases. In searching for new proteins essential to the human endothelial inflammatory response, we have found that the endosomal GTPase RhoB is up-regulated in response to inflammatory cytokines and expressed in the endothelium of some chronically inflamed tissues. We show that although RhoB and the related RhoA and RhoC play additive and redundant roles in various aspects of endothelial barrier function, RhoB specifically inhibits barrier restoration after acute cell contraction by preventing plasma membrane extension. During barrier restoration, RhoB trafficking is induced between vesicles containing RhoB nanoclusters and plasma membrane protrusions. The Rho GTPase Rac1 controls membrane spreading and stabilizes endothelial barriers. We show that RhoB colocalizes with Rac1 in endosomes and inhibits Rac1 activity and trafficking to the cell border during barrier recovery. Inhibition of endosomal trafficking impairs barrier reformation, whereas induction of Rac1 translocation to the plasma membrane accelerates it. Therefore, RhoB-specific regulation of Rac1 trafficking controls endothelial barrier integrity during inflammation. PMID:27138256

  7. The Rac-GAP Bcr is a novel regulator of the Par complex that controls cell polarity

    PubMed Central

    Narayanan, Anjana S.; Reyes, Steve B.; Um, Kyongmi; McCarty, Joseph H.; Tolias, Kimberley F.

    2013-01-01

    Cell polarization is essential for many biological processes, including directed cell migration, and loss of polarity contributes to pathological conditions such as cancer. The Par complex (Par3, Par6, and PKCζ) controls cell polarity in part by recruiting the Rac-specific guanine nucleotide exchange factor T-lymphoma invasion and metastasis 1 (Tiam1) to specialized cellular sites, where Tiam1 promotes local Rac1 activation and cytoskeletal remodeling. However, the mechanisms that restrict Par-Tiam1 complex activity to the leading edge to maintain cell polarity during migration remain unclear. We identify the Rac-specific GTPase-activating protein (GAP) breakpoint cluster region protein (Bcr) as a novel regulator of the Par-Tiam1 complex. We show that Bcr interacts with members of the Par complex and inhibits both Rac1 and PKCζ signaling. Loss of Bcr results in faster, more random migration and striking polarity defects in astrocytes. These polarity defects are rescued by reducing PKCζ activity or by expressing full-length Bcr, but not an N-terminal deletion mutant or the homologous Rac-GAP, Abr, both of which fail to associate with the Par complex. These results demonstrate that Bcr is an integral member of the Par-Tiam1 complex that controls polarized cell migration by locally restricting both Rac1 and PKCζ function. PMID:24152735

  8. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  9. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  10. ACTIVATED CARBON FROM LIGNITE FOR WATER TREATMENT

    SciTech Connect

    Edwin S. Olson; Daniel J. Stepan

    2000-07-01

    High concentrations of humate in surface water result in the formation of excess amounts of chlorinated byproducts during disinfection treatment. These precursors can be removed in water treatment prior to disinfection using powdered activated carbon. In the interest of developing a more cost-effective method for removal of humates in surface water, a comparison of the activities of carbons prepared from North Dakota lignites with those of commercial carbons was conducted. Previous studies indicated that a commercial carbon prepared from Texas lignite (Darco HDB) was superior to those prepared from bituminous coals for water treatment. That the high alkali content of North Dakota lignites would result in favorable adsorptive properties for the very large humate molecules was hypothesized, owing to the formation of larger pores during activation. Since no standard humate test has been previously developed, initial adsorption testing was performed using smaller dye molecules with various types of ionic character. With the cationic dye, methylene blue, a carbon prepared from a high-sodium lignite (HSKRC) adsorbed more dye than the Darco HDB. The carbon from the low-sodium lignite was much inferior. With another cationic dye, malachite green, the Darco HDB was slightly better. With anionic dyes, methyl red and azocarmine-B, the results for the HSKRC and Darco HDB were comparable. A humate test was developed using Aldrich humic acid. The HSKRC and the Darco HDB gave equally high adsorption capacities for the humate (138 mg/g), consistent with the similarities observed in earlier tests. A carbon prepared from a high-sodium lignite from a different mine showed an outstanding improvement (201 mg/g). The carbons prepared from the low-sodium lignites from both mines showed poor adsorption capacities for humate. Adsorption isotherms were performed for the set of activated carbons in the humate system. These exhibited a complex behavior interpreted as resulting from two types

  11. The small Rho GTPase Rac1 controls normal human dermal fibroblasts proliferation with phosphorylation of the oncoprotein c-myc

    SciTech Connect

    Nikolova, Ekaterina; Mitev, Vanio; Zhelev, Nikolai; Deroanne, Christophe F. . E-mail: yves.poumay@fundp.ac.be

    2007-08-03

    Proliferation of dermal fibroblasts is crucial for the maintenance of skin. The small Rho GTPase, Rac1, has been identified as a key transducer of proliferative signals in various cell types, but in normal human dermal fibroblasts its significance to cell growth control has not been studied. In this study, we applied the method of RNA interference to suppress endogenous Rac1 expression and examined the consequences on human skin fibroblasts. Rac1 knock-down resulted in inhibition of DNA synthesis. This effect was not mediated by inhibition of the central transducer of proliferative stimuli, ERK1/2 or by activation of the pro-apoptotic p38. Rather, as a consequence of the suppressed Rac1 expression we observed a significant decrease in phosphorylation of c-myc, revealing for the first time that in human fibroblasts Rac1 exerts control on proliferation through c-myc phosphorylation. Thus Rac1 activates proliferation of normal fibroblasts through stimulation of c-myc phosphorylation without affecting ERK1/2 activity.

  12. Physiological Function of Rac Prophage During Biofilm Formation and Regulation of Rac Excision in Escherichia coli K-12.

    PubMed

    Liu, Xiaoxiao; Li, Yangmei; Guo, Yunxue; Zeng, Zhenshun; Li, Baiyuan; Wood, Thomas K; Cai, Xingsheng; Wang, Xiaoxue

    2015-01-01

    Rac or rac-like prophage harbors many genes with important physiological functions, while it remains excision-proficient in several bacterial strains including Escherichia coli, Salmonella spp. and Shigella spp. Here, we found that rac excision is induced during biofilm formation, and the isogenic stain without rac is more motile and forms more biofilms in nutrient-rich medium at early stages in E. coli K-12. Additionally, the presence of rac genes increases cell lysis during biofilm development. In most E. coli strains, rac is integrated into the ttcA gene which encodes a tRNA-thioltransferase. Rac excision in E. coli K-12 leads to a functional change of TtcA, which results in reduced fitness in the presence of carbenicillin. Additionally, we demonstrate that YdaQ (renamed as XisR) is the excisionase of rac in E. coli K-12, and that rac excision is induced by the stationary sigma factor RpoS through inducing xisR expression. Taken together, our results reveal that upon rac integration, not only are new genes introduced into the host, but also there is a functional change in a host enzyme. Hence, rac excision is tightly regulated by host factors to control its stability in the host genome under different stress conditions. PMID:26530864

  13. Physiological Function of Rac Prophage During Biofilm Formation and Regulation of Rac Excision in Escherichia coli K-12

    PubMed Central

    Liu, Xiaoxiao; Li, Yangmei; Guo, Yunxue; Zeng, Zhenshun; Li, Baiyuan; Wood, Thomas K.; Cai, Xingsheng; Wang, Xiaoxue

    2015-01-01

    Rac or rac-like prophage harbors many genes with important physiological functions, while it remains excision-proficient in several bacterial strains including Escherichia coli, Salmonella spp. and Shigella spp. Here, we found that rac excision is induced during biofilm formation, and the isogenic stain without rac is more motile and forms more biofilms in nutrient-rich medium at early stages in E. coli K-12. Additionally, the presence of rac genes increases cell lysis during biofilm development. In most E. coli strains, rac is integrated into the ttcA gene which encodes a tRNA-thioltransferase. Rac excision in E. coli K-12 leads to a functional change of TtcA, which results in reduced fitness in the presence of carbenicillin. Additionally, we demonstrate that YdaQ (renamed as XisR) is the excisionase of rac in E. coli K-12, and that rac excision is induced by the stationary sigma factor RpoS through inducing xisR expression. Taken together, our results reveal that upon rac integration, not only are new genes introduced into the host, but also there is a functional change in a host enzyme. Hence, rac excision is tightly regulated by host factors to control its stability in the host genome under different stress conditions. PMID:26530864

  14. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyen, M.; Lafferty, C.; Kimber, G.

    1996-12-31

    This paper describes the results of research in which novel activated carbons have been examined for their efficacy in water treatment and, specifically, for the adsorption of a common herbicide and wood preservative, sodium pentachlorophenolate. To place this work in context, the introduction will discuss first some of the considerations of using activated carbons for water treatment, and then certain aspects of the authors research that has led to this particular topic.

  15. Activated Carbons From Grape Seeds By Chemical Activation With Potassium Carbonate And Potassium Hydroxide

    NASA Astrophysics Data System (ADS)

    Okman, Irem; Karagöz, Selhan; Tay, Turgay; Erdem, Murat

    2014-02-01

    Activated carbons were produced from grape seed using either potassium carbonate (K2CO3) or potassium hydroxide (KOH). The carbonization experiments were accomplished at 600 and 800 °C. The effects of the experimental conditions (i.e., type of activation reagents, reagent concentrations, and carbonization temperatures) on the yields and the properties of these activated carbons were analyzed under identical conditions. An increase in the temperature at the same concentrations for both K2CO3 and KOH led to a decrease in the yields of the activated carbons. The lowest activated carbon yields were obtained at 800 °C at the highest reagent concentration (100 wt%) for both K2CO3 and KOH. The activated carbon with the highest surface area of 1238 m2g-1 was obtained at 800 °C in K2CO3 concentration of 50 wt% while KOH produced the activated carbon with the highest surface area of 1222 m2g-1 in a concentration of 25wt% at 800 °C. The obtained activated carbons were mainly microporous.

  16. Arhgef16, a novel Elmo1 binding partner, promotes clearance of apoptotic cells via RhoG-dependent Rac1 activation.

    PubMed

    Lee, Juyeon; Park, Boyeon; Kim, Gayoung; Kim, Kwangwoo; Pak, Jeongjun; Kim, Kwanhyeong; Ye, Michael B; Park, Sung-Gyoo; Park, Daeho

    2014-11-01

    Elmo is an evolutionarily conserved mammalian ortholog of Caenorhabditis elegans CED-12 with proposed roles during the removal of apoptotic cells, cell migration, neurite outgrowth, and myoblast fusion (Katoh and Negishi (2003) [1], Park and Tosello (2007) [2], Grimsley et al. (2004) [3], Hamoud et al. (2014) [4]). Elmo mediates these cellular processes by interacting with various proteins located in the plasma membrane, cytoplasm and nucleus, and by modulating their activities although it has no intrinsic catalytic activity (Park and Tosello (2007) [2], Hamoud et al. (2014) [4], Li et al. (2013) [5], Margaron, Fradet and Cote (2013) [6], and Mauldin et al. (2013)[7]). Because there are a limited number of proteins known to interact with Elmo, we performed a yeast two-hybrid screen using Elmo1 as bait to identify Elmo1-interacting proteins and to evaluate their mode of regulation. Arhgef16 was one of the proteins identified through the screen and subsequent analyses revealed that Arhgef16 interacted with Elmo1 in mammalian cells as well. Expression of Arhgef16 in phagocytes promoted engulfment of apoptotic cells, and engulfment mediated by Arhgef16 increased synergistically in the presence of Elmo1 but was abrogated in the absence of Elmo1. In addition, Arhgef16-mediated removal of apoptotic cells was dependent on RhoG, but independent of Dock1. Taken together, this study suggests that the newly identified Elmo1-interacting protein, Arhgef16, functions synergistically with Elmo1 to promote clearance of apoptotic cells in a RhoG-dependent and Dock1-independent manner. PMID:25063526

  17. Organic solvent regeneration of granular activated carbon

    NASA Astrophysics Data System (ADS)

    Cross, W. H.; Suidan, M. T.; Roller, M. A.; Kim, B. R.; Gould, J. P.

    1982-09-01

    The use of activated carbon for the treatment of industrial waste-streams was shown to be an effective treatment. The high costs associated with the replacement or thermal regeneration of the carbon have prohibited the economic feasibility of this process. The in situ solvent regeneration of activated carbon by means of organic solvent extraction was suggested as an economically alternative to thermal regeneration. The important aspects of the solvent regeneration process include: the physical and chemical characteristics of the adsorbent, the pore size distribution and energy of adsorption associated with the activated carbon; the degree of solubility of the adsorbate in the organic solvent; the miscibility of the organic solvent in water; and the temperature at which the generation is performed.

  18. Microwave-assisted regeneration of activated carbon.

    PubMed

    Foo, K Y; Hameed, B H

    2012-09-01

    Microwave heating was used in the regeneration of methylene blue-loaded activated carbons produced from fibers (PFAC), empty fruit bunches (EFBAC) and shell (PSAC) of oil palm. The dye-loaded carbons were treated in a modified conventional microwave oven operated at 2450 MHz and irradiation time of 2, 3 and 5 min. The virgin properties of the origin and regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue (MB). Microwave irradiation preserved the pore structure, original active sites and adsorption capacity of the regenerated activated carbons. The carbon yield and the monolayer adsorption capacities for MB were maintained at 68.35-82.84% and 154.65-195.22 mg/g, even after five adsorption-regeneration cycles. The findings revealed the potential of microwave heating for regeneration of spent activated carbons. PMID:22728787

  19. Antimicrobial Activity of Carbon-Based Nanoparticles

    PubMed Central

    Maleki Dizaj, Solmaz; Mennati, Afsaneh; Jafari, Samira; Khezri, Khadejeh; Adibkia, Khosro

    2015-01-01

    Due to the vast and inappropriate use of the antibiotics, microorganisms have begun to develop resistance to the commonly used antimicrobial agents. So therefore, development of the new and effective antimicrobial agents seems to be necessary. According to some recent reports, carbon-based nanomaterials such as fullerenes, carbon nanotubes (CNTs) (especially single-walled carbon nanotubes (SWCNTs)) and graphene oxide (GO) nanoparticles show potent antimicrobial properties. In present review, we have briefly summarized the antimicrobial activity of carbon-based nanoparticles together with their mechanism of action. Reviewed literature show that the size of carbon nanoparticles plays an important role in the inactivation of the microorganisms. As major mechanism, direct contact of microorganisms with carbon nanostructures seriously affects their cellular membrane integrity, metabolic processes and morphology. The antimicrobial activity of carbon-based nanostructures may interestingly be investigated in the near future owing to their high surface/volume ratio, large inner volume and other unique chemical and physical properties. In addition, application of functionalized carbon nanomaterials as carriers for the ordinary antibiotics possibly will decrease the associated resistance, enhance their bioavailability and provide their targeted delivery. PMID:25789215

  20. Activated coconut shell charcoal carbon using chemical-physical activation

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Umiatin, Nasbey, Hadi; Bintoro, Ridho Akbar; Wulandari, Futri; Erlina

    2016-02-01

    The use of activated carbon from natural material such as coconut shell charcoal as metal absorbance of the wastewater is a new trend. The activation of coconut shell charcoal carbon by using chemical-physical activation has been investigated. Coconut shell was pyrolized in kiln at temperature about 75 - 150 °C for about 6 hours in producing charcoal. The charcoal as the sample was shieved into milimeter sized granule particle and chemically activated by immersing in various concentration of HCl, H3PO4, KOH and NaOH solutions. The samples then was physically activated using horizontal furnace at 400°C for 1 hours in argon gas environment with flow rate of 200 kg/m3. The surface morphology and carbon content of activated carbon were characterized by using SEM/EDS. The result shows that the pores of activated carbon are openned wider as the chemical activator concentration is increased due to an excessive chemical attack. However, the pores tend to be closed as further increasing in chemical activator concentration due to carbon collapsing.

  1. Cyclooxygenase-2 knockdown using retinoic acid chalcone (RAC), a promising therapeutic strategy for colon cancer

    PubMed Central

    Jiang, Chao; Wang, Qiong; Xu, Zhe; Li, Wei-Su; Chen, Che; Yao, Xue-Quan; Liu, Fu-Kun

    2015-01-01

    Retinoic acid is an effective agent in the treatment of epithelial and hematological malignancies. The present study demonstrates that retinoic acid chalcone (RAC), an analogue of retinoic acid inhibits cell proliferation and induces apoptosis in HCT-15 and CT26.WT colon cancer cell lines. In HCT-15 cells the percentage of apoptotic cells increased from 32.4 ± 3, 45.0 ± 3 to 72.6 ± 5% respectively at 10, 15 and 20 μg/mL compared to 3.7% in control. Similarly in CT26.WT cells the percentage increased from 28.6 ± 3, 41.2 ± 3 to 65.4 ± 5% on treatment with 10, 15 and 20 μg/mL concentrations of RAC after 72 h compared to 2.9 ± 1% in control. Western blotting, fluorescence-activated cell sorting analysis and reverse transcription-PCR assays were used to investigate these effects. RAC inhibited the overexpression of COX-2, PGE2 and PGE2 receptor (EP1 and EP4) in the colon cancer cell lines. RAC mediated inhibition of cell growth and induction of apoptosis through COX-2 inhibition was also confirmed by treating the HCT-15 and CT26.WT colon cancer cells with COX-2 inhibitor, indomethacin and transfection of cells with COX-2 small interfering RNA. In nude mice with tumor xenografts, treatment with RAC-supplemented diet caused inhibition of COX-2, PGE2, and PGE2 receptors (EP1, EP3, and EP4) in tumors. Thus RAC can be a potential candidate for the treatment of colon cancer through the inhibition of COX-2 expression and subsequent inhibition of PGE2 and PGE2 receptors. PMID:26269760

  2. Dock4 is regulated by RhoG and promotes Rac-dependent cell migration.

    PubMed

    Hiramoto, Kiyo; Negishi, Manabu; Katoh, Hironori

    2006-12-10

    Cell migration is essential for normal development and many pathological processes including tumor metastasis. Rho family GTPases play important roles in this event. In particular, Rac is required for lamellipodia formation at the leading edge during migration. Dock4 is a member of the Dock180 family proteins, and Dock4 mutations are present in a subset of human cancer cell lines. However, the function and the regulatory mechanism of Dock4 remain unclear. Here we show that Dock4 is regulated by the small GTPase RhoG and its effector ELMO and promotes cell migration by activating Rac1. Dock4 formed a complex with ELMO, and expression of active RhoG induced translocation of the Dock4-ELMO complex from the cytoplasm to the plasma membrane and enhanced the Dock4- and ELMO-dependent Rac1 activation and cell migration. On the other hand, RNA interference-mediated knockdown of Dock4 in NIH3T3 cells reduced cell migration. Taken together, these results suggest that Dock4 plays an important role in the regulation of cell migration through activation of Rac1, and that RhoG is a key upstream regulator for Dock4. PMID:17027967

  3. RAC: Repository of Antibiotic resistance Cassettes

    PubMed Central

    Tsafnat, Guy; Copty, Joseph; Partridge, Sally R.

    2011-01-01

    Antibiotic resistance in bacteria is often due to acquisition of resistance genes associated with different mobile genetic elements. In Gram-negative bacteria, many resistance genes are found as part of small mobile genetic elements called gene cassettes, generally found integrated into larger elements called integrons. Integrons carrying antibiotic resistance gene cassettes are often associated with mobile elements and here are designated ‘mobile resistance integrons’ (MRIs). More than one cassette can be inserted in the same integron to create arrays that contribute to the spread of multi-resistance. In many sequences in databases such as GenBank, only the genes within cassettes, rather than whole cassettes, are annotated and the same gene/cassette may be given different names in different entries, hampering analysis. We have developed the Repository of Antibiotic resistance Cassettes (RAC) website to provide an archive of gene cassettes that includes alternative gene names from multiple nomenclature systems and allows the community to contribute new cassettes. RAC also offers an additional function that allows users to submit sequences containing cassettes or arrays for annotation using the automatic annotation system Attacca. Attacca recognizes features (gene cassettes, integron regions) and identifies cassette arrays as patterns of features and can also distinguish minor cassette variants that may encode different resistance phenotypes (aacA4 cassettes and bla cassettes-encoding β-lactamases). Gaps in annotations are manually reviewed and those found to correspond to novel cassettes are assigned unique names. While there are other websites dedicated to integrons or antibiotic resistance genes, none includes a complete list of antibiotic resistance gene cassettes in MRI or offers consistent annotation and appropriate naming of all of these cassettes in submitted sequences. RAC thus provides a unique resource for researchers, which should reduce confusion

  4. The Rac Inhibitor EHop-016 Inhibits Mammary Tumor Growth and Metastasis in a Nude Mouse Model

    PubMed Central

    Castillo-Pichardo, Linette; Humphries-Bickley, Tessa; De La Parra, Columba; Forestier-Roman, Ingrid; Martinez-Ferrer, Magaly; Hernandez, Eliud; Vlaar, Cornelis; Ferrer-Acosta, Yancy; Washington, Anthony V.; Cubano, Luis A.; Rodriguez-Orengo, Jose; Dharmawardhane, Suranganie

    2014-01-01

    Metastatic disease still lacks effective treatments, and remains the primary cause of cancer mortality. Therefore, there is a critical need to develop better strategies to inhibit metastatic cancer. The Rho family GTPase Rac is an ideal target for anti-metastatic cancer therapy, because Rac is a key molecular switch that is activated by a myriad of cell surface receptors to promote cancer cell migration/invasion and survival. Previously, we reported the design and development of EHop-016, a small molecule compound, which inhibits Rac activity of metastatic cancer cells with an IC50 of 1 μM. EHop-016 also inhibits the activity of the Rac downstream effector p21-activated kinase (PAK), lamellipodia extension, and cell migration in metastatic cancer cells. Herein, we tested the efficacy of EHop-016 in a nude mouse model of experimental metastasis, where EHop-016 administration at 25 mg/kg body weight (BW) significantly reduced mammary fat pad tumor growth, metastasis, and angiogenesis. As quantified by UPLC MS/MS, EHop-016 was detectable in the plasma of nude mice at 17 to 23 ng/ml levels at 12 h following intraperitoneal (i.p.) administration of 10 to 25 mg/kg BW EHop-016. The EHop-016 mediated inhibition of angiogenesis In Vivo was confirmed by immunohistochemistry of excised tumors and by In Vitro tube formation assays of endothelial cells. Moreover, EHop-016 affected cell viability by down-regulating Akt and Jun kinase activities and c-Myc and Cyclin D expression, as well as increasing caspase 3/7 activities in metastatic cancer cells. In conclusion, EHop-016 has potential as an anticancer compound to block cancer progression via multiple Rac-directed mechanisms. PMID:25389450

  5. Rac1/Pak1/p38/MMP-2 axis regulates angiogenesis in ovarian cancer

    PubMed Central

    Gonzalez-Villasana, Vianey; Fuentes-Mattei, Enrique; Ivan, Cristina; Dalton, Heather J.; Rodriguez-Aguayo, Cristian; Fernandez-de Thomas, Ricardo J.; Aslan, Burcu; Monroig, Paloma del C.; Velazquez-Torres, Guermarie; Previs, Rebecca A.; Pradeep, Sunila; Kahraman, Nermin; Wang, Huamin; Kanlikilicer, Pinar; Ozpolat, Bulent; Calin, George; Sood, Anil K.; Lopez-Berestein, Gabriel

    2015-01-01

    Purpose Zoledronic acid (ZA) is being increasingly recognized for its anti-tumor properties, but the underlying functions are not well understood. In this study, we hypothesized that ZA inhibits ovarian cancer (OC) angiogenesis preventing Rac1 activation. Experimental Design The biological effects of ZA were examined using a series of in vitro (cell invasion, cytokine production, Rac1 activation, reverse-phase protein array and in vivo (orthotopic mouse models) experiments. Results There was significant inhibition of OC (HeyA8-MDR and OVCAR-5) cell invasion as well as reduced production of pro-angiogenic cytokines in response to ZA treatment. Furthermore, ZA inactivated Rac1 and decreased the levels of Pak1/p-38/matrix metalloproteinase-2 in OC cells. In vivo, ZA reduced tumor growth, angiogenesis and cell proliferation and inactivated Rac1 in both HeyA8-MDR and OVCAR-5 models. These in vivo antitumor effects were enhanced in both models when ZA was combined with nab-paclitaxel. Conclusion ZA has robust anti-tumor and anti-angiogenic activity and merits further clinical development as OC treatment. PMID:25595279

  6. Inhibition of the GTPase Rac1 mediates the antimigratory effects of metformin in prostate cancer cells.

    PubMed

    Dirat, Béatrice; Ader, Isabelle; Golzio, Muriel; Massa, Fabienne; Mettouchi, Amel; Laurent, Kathiane; Larbret, Frédéric; Malavaud, Bernard; Cormont, Mireille; Lemichez, Emmanuel; Cuvillier, Olivier; Tanti, Jean François; Bost, Frédéric

    2015-02-01

    Cell migration is a critical step in the progression of prostate cancer to the metastatic state, the lethal form of the disease. The antidiabetic drug metformin has been shown to display antitumoral properties in prostate cancer cell and animal models; however, its role in the formation of metastases remains poorly documented. Here, we show that metformin reduces the formation of metastases to fewer solid organs in an orthotopic metastatic prostate cancer cell model established in nude mice. As predicted, metformin hampers cell motility in PC3 and DU145 prostate cancer cells and triggers a radical reorganization of the cell cytoskeleton. The small GTPase Rac1 is a master regulator of cytoskeleton organization and cell migration. We report that metformin leads to a major inhibition of Rac1 GTPase activity by interfering with some of its multiple upstream signaling pathways, namely P-Rex1 (a Guanine nucleotide exchange factor and activator of Rac1), cAMP, and CXCL12/CXCR4, resulting in decreased migration of prostate cancer cells. Importantly, overexpression of a constitutively active form of Rac1, or P-Rex, as well as the inhibition of the adenylate cyclase, was able to reverse the antimigratory effects of metformin. These results establish a novel mechanism of action for metformin and highlight its potential antimetastatic properties in prostate cancer. PMID:25527635

  7. An evolutionarily conserved autoinhibitory molecular switch in ELMO proteins regulates Rac signaling.

    PubMed

    Patel, Manishha; Margaron, Yoran; Fradet, Nadine; Yang, Qi; Wilkes, Brian; Bouvier, Michel; Hofmann, Kay; Côté, Jean-François

    2010-11-23

    Dedicator of cytokinesis (DOCK) proteins are guanine nucleotide exchange factors (GEFs) controlling the activity of Rac1/Cdc42 during migration, phagocytosis, and myoblast fusion [1-4]. Engulfment and cell motility (ELMO) proteins bind a subset of DOCK members and are emerging as critical regulators of Rac signaling [5-10]. Although formation of a DOCK180/ELMO complex is not essential for Rac1 activation, ELMO mutants deficient in binding to DOCK180 are unable to promote cytoskeleton remodeling [11]. How ELMO regulates signaling through DOCK GEFs is poorly understood. Here, we identify an autoinhibitory switch in ELMO presenting homology to a regulatory unit described for Dia formins. One part of the switch, composed of a Ras-binding domain (RBD) and Armadillo repeats, is positioned N-terminally while the other is housed in the C terminus. We demonstrate interaction between these fragments, suggesting autoinhibition of ELMO. Using a bioluminescence resonance energy transfer biosensor, we establish that ELMO undergoes conformational changes upon disruption of autoinhibition. We found that engagement of ELMO to RhoG, or with DOCK180, promotes the relief of autoinhibition in ELMO. Functionally, we found that ELMO mutants with impaired autoregulatory activity promote cell elongation. These results demonstrate an unsuspected level of regulation for Rac1 signaling via autoinhibition of ELMO. PMID:21035343

  8. Microcystin-LR Adsorption by Activated Carbon.

    PubMed

    Pendleton, Phillip; Schumann, Russell; Wong, Shiaw Hui

    2001-08-01

    We use a selection of wood-based and coconut-based activated carbons to investigate the factors controlling the removal of the hepatotoxin microcystin-LR (m-LR) from aqueous solutions. The wood carbons contain both micropores and mesopores. The coconut carbons contain micropores only. Confirming previously published observations, we also find that the wood-based carbons adsorb more microcystin than the coconut-based carbons. From a combination of a judicious modification of a wood-based carbon's surface chemistry and of the solution chemistry, we demonstrate that both surface and solution chemistry play minor roles in the adsorption process, with the adsorbent surface chemistry exhibiting less influence than the solution chemistry. Conformational changes at low solution pH probably contribute to the observed increase in adsorption by both classes of adsorbent. At the solution pH of 2.5, the coconut-based carbons exhibit a 400% increased affinity for m-LR compared with 100% increases for the wood-based carbons. In an analysis of the thermodynamics of adsorption, using multiple temperature adsorption chromatography methods, we indicate that m-LR adsorption is an entropy-driven process for each of the carbons, except the most hydrophilic and mesoporous carbon, B1. In this case, exothermic enthalpy contributions to adsorption also exist. From our overall observations, since m-LR contains molecular dimensions in the secondary micropore width range, we demonstrate that it is important to consider both the secondary micropore and the mesopore volumes for the adsorption of m-LR from aqueous solutions. Copyright 2001 Academic Press. PMID:11446779

  9. A novel activated carbon for supercapacitors

    SciTech Connect

    Shen, Haijie; Liu, Enhui; Xiang, Xiaoxia; Huang, Zhengzheng; Tian, Yingying; Wu, Yuhu; Wu, Zhilian; Xie, Hui

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer A novel activated carbon was prepared from phenol-melamine-formaldehyde resin. Black-Right-Pointing-Pointer The carbon has large surface area with microporous, and high heteroatom content. Black-Right-Pointing-Pointer Heteroatom-containing functional groups can improve the pseudo-capacitance. Black-Right-Pointing-Pointer Physical and chemical properties lead to the good electrochemical properties. -- Abstract: A novel activated carbon has been prepared by simple carbonization and activation of phenol-melamine-formaldehyde resin which is synthesized by the condensation polymerization method. The morphology, thermal stability, surface area, elemental composition and surface chemical composition of samples have been investigated by scanning electron microscope, thermogravimetry and differential thermal analysis, Brunauer-Emmett-Teller measurement, elemental analysis and X-ray photoelectron spectroscopy, respectively. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L{sup -1} potassium hydroxide. The activated carbon shows good capacitive behavior and the specific capacitance is up to 210 F g{sup -1}, which indicates that it may be a promising candidate for supercapacitors.

  10. Activated carbon monoliths for methane storage

    NASA Astrophysics Data System (ADS)

    Chada, Nagaraju; Romanos, Jimmy; Hilton, Ramsey; Suppes, Galen; Burress, Jacob; Pfeifer, Peter

    2012-02-01

    The use of adsorbent storage media for natural gas (methane) vehicles allows for the use of non-cylindrical tanks due to the decreased pressure at which the natural gas is stored. The use of carbon powder as a storage material allows for a high mass of methane stored for mass of sample, but at the cost of the tank volume. Densified carbon monoliths, however, allow for the mass of methane for volume of tank to be optimized. In this work, different activated carbon monoliths have been produced using a polymeric binder, with various synthesis parameters. The methane storage was studied using a home-built, dosing-type instrument. A monolith with optimal parameters has been fabricated. The gravimetric excess adsorption for the optimized monolith was found to be 161 g methane for kg carbon.

  11. Rac1 and Cdc42 GTPases regulate shear stress-driven β-catenin signaling in osteoblasts

    PubMed Central

    Wan, Qiaoqiao; Cho, Eunhye; Yokota, Hiroki; Na, Sungsoo

    2013-01-01

    Beta-catenin-dependent TCF/LEF (T-cell factor/lymphocyte enhancing factor) is known to be mechanosensitive and an important regulator for promoting bone formation. However, the functional connection between TCF/LEF activity and Rho family GTPases is not well understood in osteoblasts. Herein we investigated the molecular mechanisms underlying oscillatory shear stress-induced TCF/LEF activity in MC3T3-E1 osteoblast cells using live cell imaging. We employed fluorescence resonance energy transfer (FRET)-based and green fluorescent protein (GFP)-based biosensors, which allowed us to monitor signal transduction in living cells in real time. Oscillatory (1 Hz) shear stress (10 dynes/cm2) increased TCF/LEF activity and stimulated translocation of β-catenin to the nucleus with the distinct activity patterns of Rac1 and Cdc42. The shear stress-induced TCF/LEF activity was blocked by the inhibition of Rac1 and Cdc42 with their dominant negative mutants or selective drugs, but not by a dominant negative mutant of RhoA. In contrast, constitutively active Rac1 and Cdc42 mutants caused a significant enhancement of TCF/LEF activity. Moreover, activation of Rac1 and Cdc42 increased the basal level of TCF/LEF activity, while their inhibition decreased the basal level. Interestingly, disruption of cytoskeletal structures or inhibition of myosin activity did not significantly affect shear stress-induced TCF/LEF activity. Although Rac1 is reported to be involved in β-catenin in cancer cells, the involvement of Cdc42 in β-catenin signaling in osteoblasts has not been identified. Our findings in this study demonstrate that both Rac1 and Cdc42 GTPases are critical regulators in shear stress-driven β-catenin signaling in osteoblasts. PMID:23524265

  12. Programmed Application of Transforming Growth Factor β3 and Rac1 Inhibitor NSC23766 Committed Hyaline Cartilage Differentiation of Adipose-Derived Stem Cells for Osteochondral Defect Repair

    PubMed Central

    Zhu, Shouan; Chen, Pengfei; Wu, Yan; Xiong, Si; Sun, Heng; Xia, Qingqing; Shi, Libing

    2014-01-01

    Hyaline cartilage differentiation is always the challenge with application of stem cells for joint repair. Transforming growth factors (TGFs) and bone morphogenetic proteins can initiate cartilage differentiation but often lead to hypertrophy and calcification, related to abnormal Rac1 activity. In this study, we developed a strategy of programmed application of TGFβ3 and Rac1 inhibitor NSC23766 to commit the hyaline cartilage differentiation of adipose-derived stem cells (ADSCs) for joint cartilage repair. ADSCs were isolated and cultured in a micromass and pellet culture model to evaluate chondrogenic and hypertrophic differentiation. The function of Rac1 was investigated with constitutively active Rac1 mutant and dominant negative Rac1 mutant. The efficacy of ADSCs with programmed application of TGFβ3 and Rac1 inhibitor for cartilage repair was studied in a rat model of osteochondral defects. The results showed that TGFβ3 promoted ADSCs chondro-lineage differentiation and that NSC23766 prevented ADSC-derived chondrocytes from hypertrophy in vitro. The combination of ADSCs, TGFβ3, and NSC23766 promoted quality osteochondral defect repair in rats with much less chondrocytes hypertrophy and significantly higher International Cartilage Repair Society macroscopic and microscopic scores. The findings have illustrated that programmed application of TGFβ3 and Rac1 inhibitor NSC23766 can commit ADSCs to chondro-lineage differentiation and improve the efficacy of ADSCs for cartilage defect repair. These findings suggest a promising stem cell-based strategy for articular cartilage repair. PMID:25154784

  13. The Candida albicans ELMO homologue functions together with Rac1 and Dck1, upstream of the MAP Kinase Cek1, in invasive filamentous growth.

    PubMed

    Hope, Hannah; Schmauch, Christian; Arkowitz, Robert A; Bassilana, Martine

    2010-06-01

    Regulation of Rho G-proteins is critical for cytoskeletal organization and cell morphology in all eukaryotes. In the human opportunistic pathogen Candida albicans, Rac1 and its activator Dck1, a member of the CED5, Dock180, myoblast city family of guanine nucleotide exchange factors, are required for the budding to filamentous transition during invasive growth. We show that Lmo1, a protein with similarity to human ELMO1, is necessary for invasive filamentous growth, similar to Rac1 and Dck1. Furthermore, Rac1, Dck1 and Lmo1 are required for cell wall integrity, as the deletion mutants are sensitive to cell wall perturbing agents, but not to oxidative or osmotic stresses. The region of Lmo1 encompassing the ELMO and PH-like domains is sufficient for its function. Both Rac1 and Dck1 can bind Lmo1. Overexpression of a number of protein kinases in the rac1, dck1 and lmo1 deletion mutants indicates that Rac1, Dck1 and Lmo1 function upstream of the mitogen-activated protein kinases Cek1 and Mkc1, linking invasive filamentous growth to cell wall integrity. We conclude that the requirement of ELMO/CED12 family members for Rac1 function is conserved from fungi to humans. PMID:20444104

  14. Preparation of activated carbons with mesopores by use of organometallics

    SciTech Connect

    Yamada, Yoshio; Yoshizawa, Noriko; Furuta, Takeshi

    1996-12-31

    Activated carbons are commercially produced by steam or CO{sub 2} activation of coal, coconut shell and so on. In general the carbons obtained give pores with a broad range of distribution. The objective of this study was to prepare activated carbons from coal by use of various organometallic compounds. The carbons were evaluated for pore size by nitrogen adsorption experiments.

  15. Rac1 and Cdc42 GTPases regulate shear stress-driven β-catenin signaling in osteoblasts

    SciTech Connect

    Wan, Qiaoqiao; Cho, Eunhye; Yokota, Hiroki; Na, Sungsoo

    2013-04-19

    Highlights: •Shear stress increased TCF/LEF activity and stimulated β-catenin nuclear localization. •Rac1, Cdc42, and RhoA displayed distinct dynamic activity patterns under flow. •Rac1 and Cdc42, but not RhoA, regulate shear stress-driven TCF/LEF activation. •Cytoskeleton did not significantly affect shear stress-induced TCF/LEF activation. -- Abstract: Beta-catenin-dependent TCF/LEF (T-cell factor/lymphocyte enhancing factor) is known to be mechanosensitive and an important regulator for promoting bone formation. However, the functional connection between TCF/LEF activity and Rho family GTPases is not well understood in osteoblasts. Herein we investigated the molecular mechanisms underlying oscillatory shear stress-induced TCF/LEF activity in MC3T3-E1 osteoblast cells using live cell imaging. We employed fluorescence resonance energy transfer (FRET)-based and green fluorescent protein (GFP)-based biosensors, which allowed us to monitor signal transduction in living cells in real time. Oscillatory (1 Hz) shear stress (10 dynes/cm{sup 2}) increased TCF/LEF activity and stimulated translocation of β-catenin to the nucleus with the distinct activity patterns of Rac1 and Cdc42. The shear stress-induced TCF/LEF activity was blocked by the inhibition of Rac1 and Cdc42 with their dominant negative mutants or selective drugs, but not by a dominant negative mutant of RhoA. In contrast, constitutively active Rac1 and Cdc42 mutants caused a significant enhancement of TCF/LEF activity. Moreover, activation of Rac1 and Cdc42 increased the basal level of TCF/LEF activity, while their inhibition decreased the basal level. Interestingly, disruption of cytoskeletal structures or inhibition of myosin activity did not significantly affect shear stress-induced TCF/LEF activity. Although Rac1 is reported to be involved in β-catenin in cancer cells, the involvement of Cdc42 in β-catenin signaling in osteoblasts has not been identified. Our findings in this study demonstrate

  16. MODELING MERCURY CONTROL WITH POWDERED ACTIVATED CARBON

    EPA Science Inventory

    The paper presents a mathematical model of total mercury removed from the flue gas at coal-fired plants equipped with powdered activated carbon (PAC) injection for Mercury control. The developed algorithms account for mercury removal by both existing equipment and an added PAC in...

  17. EPA'S RESEARCH PROGRAM IN GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Research into Granular Activated Carbon (GAC) for use in drinking water treatment has a long history in the Drinking Water Research Division and its predecessor organizations. tudies were conducted by the U.S. Public Health Service in the late fifties and early sixties to examine...

  18. USING POWDERED ACTIVATED CARBON: A CRITICAL REVIEW

    EPA Science Inventory

    Because the performance of powdered activated carbon (PAC) for uses other than taste and odor control is poorly documented, the purpose of this article is to critically review uses that have been reported (i.e., pesticides and herbicides, synthetic organic chemicals, and trihalom...

  19. ACTIVATED CARBON TREATMENT OF KRAFT BLEACHING EFFLUENTS

    EPA Science Inventory

    The removal of color and organic contaminants by adsorption on activated carbon from the effluent of a kraft pulp bleaching plant was investigated in a pilot plant. The caustic bleach effluent, which contains 80% of the color from pulp bleaching, was decolorized successfully when...

  20. Liposome reconstitution and modulation of recombinant prenylated human Rac1 by GEFs, GDI1 and Pak1.

    PubMed

    Zhang, Si-Cai; Gremer, Lothar; Heise, Henrike; Janning, Petra; Shymanets, Aliaksei; Cirstea, Ion C; Krause, Eberhard; Nürnberg, Bernd; Ahmadian, Mohammad Reza

    2014-01-01

    Small Rho GTPases are well known to regulate a variety of cellular processes by acting as molecular switches. The regulatory function of Rho GTPases is critically dependent on their posttranslational modification at the carboxyl terminus by isoprenylation and association with proper cellular membranes. Despite numerous studies, the mechanisms of recycling and functional integration of Rho GTPases at the biological membranes are largely unclear. In this study, prenylated human Rac1, a prominent member of the Rho family, was purified in large amount from baculovirus-infected Spodoptera frugiperda insect cells using a systematic detergent screening. In contrast to non-prenylated human Rac1 purified from Escherichia coli, prenylated Rac1 from insect cells was able to associate with synthetic liposomes and to bind Rho-specific guanine nucleotide dissociation inhibitor 1 (GDI1). Subsequent liposome reconstitution experiments revealed that GDI1 efficiently extracts Rac1 from liposomes preferentially in the inactive GDP-bound state. The extraction was prevented when Rac1 was activated to its GTP-bound state by Rac-specific guanine nucleotide exchange factors (GEFs), such as Vav2, Dbl, Tiam1, P-Rex1 and TrioN, and bound by the downstream effector Pak1. We found that dissociation of Rac1-GDP from its complex with GDI1 strongly correlated with two distinct activities of especially Dbl and Tiam1, including liposome association and the GDP/GTP exchange. Taken together, our results provided first detailed insights into the advantages of the in vitro liposome-based reconstitution system to study both the integration of the signal transducing protein complexes and the mechanisms of regulation and signaling of small GTPases at biological membranes. PMID:25014207

  1. Liposome Reconstitution and Modulation of Recombinant Prenylated Human Rac1 by GEFs, GDI1 and Pak1

    PubMed Central

    Zhang, Si-Cai; Gremer, Lothar; Heise, Henrike; Janning, Petra; Shymanets, Aliaksei; Cirstea, Ion C.; Krause, Eberhard; Nürnberg, Bernd; Ahmadian, Mohammad Reza

    2014-01-01

    Small Rho GTPases are well known to regulate a variety of cellular processes by acting as molecular switches. The regulatory function of Rho GTPases is critically dependent on their posttranslational modification at the carboxyl terminus by isoprenylation and association with proper cellular membranes. Despite numerous studies, the mechanisms of recycling and functional integration of Rho GTPases at the biological membranes are largely unclear. In this study, prenylated human Rac1, a prominent member of the Rho family, was purified in large amount from baculovirus-infected Spodoptera frugiperda insect cells using a systematic detergent screening. In contrast to non-prenylated human Rac1 purified from Escherichia coli, prenylated Rac1 from insect cells was able to associate with synthetic liposomes and to bind Rho-specific guanine nucleotide dissociation inhibitor 1 (GDI1). Subsequent liposome reconstitution experiments revealed that GDI1 efficiently extracts Rac1 from liposomes preferentially in the inactive GDP-bound state. The extraction was prevented when Rac1 was activated to its GTP-bound state by Rac-specific guanine nucleotide exchange factors (GEFs), such as Vav2, Dbl, Tiam1, P-Rex1 and TrioN, and bound by the downstream effector Pak1. We found that dissociation of Rac1-GDP from its complex with GDI1 strongly correlated with two distinct activities of especially Dbl and Tiam1, including liposome association and the GDP/GTP exchange. Taken together, our results provided first detailed insights into the advantages of the in vitro liposome-based reconstitution system to study both the integration of the signal transducing protein complexes and the mechanisms of regulation and signaling of small GTPases at biological membranes. PMID:25014207

  2. RAC3 more than a nuclear receptor coactivator: a key inhibitor of senescence that is downregulated in aging

    PubMed Central

    Fernández Larrosa, P N; Ruíz Grecco, M; Mengual Gómez, D; Alvarado, C V; Panelo, L C; Rubio, M F; Alonso, D F; Gómez, D E; Costas, M A

    2015-01-01

    Receptor-associated coactivator 3 (RAC3) is a nuclear receptor coactivator usually overexpressed in tumors that exerts oncogenic functions in the cytoplasm and the nucleus. Although as part of its oncogenic actions it was previously identified as an inhibitor of apoptosis and autophagy, its expression is required in order to preserve the pluripotency and embryonic stem cell self-renewal. In this work we investigated its role in cellular senescence. We found that RAC3 overexpression in the nontumoral HEK293 cells inhibits the premature senescence induced by hydrogen peroxide or rapamycin. The mechanism involves not only the inhibition of autophagy early induced by these stimuli in the pathway to senescence, but also the increase in levels and nuclear localization of both the cell cycle suppressors p53/p21 and the longevity promoters FOXO1A, FOXO3A and SIRT1. Furthermore, we found that RAC3 overexpression is required in order to maintain the telomerase activity. In tumoral HeLa cells its activity was inhibited by depletion of RAC3 inducing replicative senescence. Moreover, we demonstrated that in vivo, levels of RAC3 are downregulated in the liver from aged as compared with young rats, whereas the levels of p21 are increased, correlating with the expected senescent cell contents in aged tissues. A similar downregulation of RAC3 was observed in the premature and replicative senescence of human fetal WI-38 cells and premature senescence of hepatocyte HepG2 cell line. Taken together, all these results demonstrate that RAC3 is an inhibitor of senescence whose downregulation in aged individuals could be probably a tumor suppressor mechanism, avoiding the clonal expansion of risky old cells having damaged DNA. PMID:26469953

  3. Making Activated Carbon for Storing Gas

    NASA Technical Reports Server (NTRS)

    Wojtowicz, Marek A.; Serio, Michael A.; Suuberg, Eric M.

    2005-01-01

    Solid disks of microporous activated carbon, produced by a method that enables optimization of pore structure, have been investigated as means of storing gas (especially hydrogen for use as a fuel) at relatively low pressure through adsorption on pore surfaces. For hydrogen and other gases of practical interest, a narrow distribution of pore sizes <2 nm is preferable. The present method is a variant of a previously patented method of cyclic chemisorption and desorption in which a piece of carbon is alternately (1) heated to the lower of two elevated temperatures in air or other oxidizing gas, causing the formation of stable carbon/oxygen surface complexes; then (2) heated to the higher of the two elevated temperatures in flowing helium or other inert gas, causing the desorption of the surface complexes in the form of carbon monoxide. In the present method, pore structure is optimized partly by heating to a temperature of 1,100 C during carbonization. Another aspect of the method exploits the finding that for each gas-storage pressure, gas-storage capacity can be maximized by burning off a specific proportion (typically between 10 and 20 weight percent) of the carbon during the cyclic chemisorption/desorption process.

  4. Junctional actin assembly is mediated by Formin-like 2 downstream of Rac1

    PubMed Central

    Grikscheit, Katharina; Frank, Tanja; Wang, Ying

    2015-01-01

    Epithelial integrity is vitally important, and its deregulation causes early stage cancer. De novo formation of an adherens junction (AJ) between single epithelial cells requires coordinated, spatial actin dynamics, but the mechanisms steering nascent actin polymerization for cell–cell adhesion initiation are not well understood. Here we investigated real-time actin assembly during daughter cell–cell adhesion formation in human breast epithelial cells in 3D environments. We identify formin-like 2 (FMNL2) as being specifically required for actin assembly and turnover at newly formed cell–cell contacts as well as for human epithelial lumen formation. FMNL2 associates with components of the AJ complex involving Rac1 activity and the FMNL2 C terminus. Optogenetic control of Rac1 in living cells rapidly drove FMNL2 to epithelial cell–cell contact zones. Furthermore, Rac1-induced actin assembly and subsequent AJ formation critically depends on FMNL2. These data uncover FMNL2 as a driver for human epithelial AJ formation downstream of Rac1. PMID:25963818

  5. Junctional actin assembly is mediated by Formin-like 2 downstream of Rac1.

    PubMed

    Grikscheit, Katharina; Frank, Tanja; Wang, Ying; Grosse, Robert

    2015-05-11

    Epithelial integrity is vitally important, and its deregulation causes early stage cancer. De novo formation of an adherens junction (AJ) between single epithelial cells requires coordinated, spatial actin dynamics, but the mechanisms steering nascent actin polymerization for cell-cell adhesion initiation are not well understood. Here we investigated real-time actin assembly during daughter cell-cell adhesion formation in human breast epithelial cells in 3D environments. We identify formin-like 2 (FMNL2) as being specifically required for actin assembly and turnover at newly formed cell-cell contacts as well as for human epithelial lumen formation. FMNL2 associates with components of the AJ complex involving Rac1 activity and the FMNL2 C terminus. Optogenetic control of Rac1 in living cells rapidly drove FMNL2 to epithelial cell-cell contact zones. Furthermore, Rac1-induced actin assembly and subsequent AJ formation critically depends on FMNL2. These data uncover FMNL2 as a driver for human epithelial AJ formation downstream of Rac1. PMID:25963818

  6. Nuclear localization of coactivator RAC3 is mediated by a bipartite NLS and importin {alpha}3

    SciTech Connect

    Yeung, Percy Luk; Zhang, Aihua; Chen, J. Don . E-mail: chenjd@umdnj.edu

    2006-09-15

    The nuclear receptor coactivator RAC3 (also known as SRC-3/ACTR/AIB1/p/CIP/TRAM-1) belongs to the p160 coactivator family, which are involved in several physiological processes and diseases. Here we have investigated how RAC3 is translocated into the nucleus and show that it is mediated through a bipartite NLS and importin {alpha}3. This bipartite NLS is located within the conserved bHLH domain, and its mutation abolished nuclear localization. The NLS is also sufficient to cause nuclear import of EGFP, and the activity requires basic amino acids within the NLS. RAC3 binds strongly to importin {alpha}3, which also depends on the basic amino acids. Functionally, RAC3 cytoplasmic mutant loses its ability to enhance transcription, suggesting that nuclear localization is essential for coactivator function. Together, these results reveal a previous unknown mechanism for nuclear translocation of p160 coactivators and a critical function of the conserved bHLH within the coactivator.

  7. Sbds is required for Rac2-mediated monocyte migration and signaling downstream of RANK during osteoclastogenesis.

    PubMed

    Leung, Roland; Cuddy, Karl; Wang, Yongqiang; Rommens, Johanna; Glogauer, Michael

    2011-02-10

    Shwachman-Diamond syndrome (SDS) results from mutations in the SBDS gene, characterized by exocrine pancreatic insufficiency and hematologic and skeletal abnormalities. Neutropenia and neutrophil dysfunction are hallmark features of SDS; however, causes for the bone defects are unknown. Dysfunction of bone-resorbing osteoclasts, formed by the fusion of monocytic progenitors derived from the same granulocytic precursors as neutrophils, could be responsible. We report that Sbds is required for in vitro and in vivo osteoclastogenesis (OCG). Sbds-null murine monocytes formed osteoclasts of reduced number and size because of impaired migration and fusion required for OCG. Phenotypically, Sbds-null mice exhibited low-turnover osteoporosis consistent with findings in SDS patients. Western blotting of Rho GTPases that control actin dynamics and migration showed a 5-fold decrease in Rac2, whereas Rac1, Cdc42, and RhoA were unchanged or only mildly reduced. Although migration was rescued on Rac2 supplementation, OCG was not. This was attributed to impaired signaling downstream of receptor activator of nuclear factor-κB (RANK) and reduced expression of the RANK-ligand-dependent fusion receptor DC-STAMP. We conclude that Sbds is required for OCG by regulating monocyte migration via Rac2 and osteoclast differentiation signaling downstream of RANK. Impaired osteoclast formation could disrupt bone homeostasis, resulting in skeletal abnormalities seen in SDS patients. PMID:21084708

  8. Staphylococcus aureus keratinocyte invasion is mediated by integrin-linked kinase and Rac1.

    PubMed

    Sayedyahossein, Samar; Xu, Stacey X; Rudkouskaya, Alena; McGavin, Martin J; McCormick, John K; Dagnino, Lina

    2015-02-01

    Staphylococcus aureus is a major component of the skin microbiota and causes a large number of serious infections. S. aureus first interacts with epidermal keratinocytes to breach the epidermal barrier through mechanisms not fully understood. By use of primary keratinocytes from mice with epidermis-restricted Ilk gene inactivation and control integrin-linked kinase (ILK)-expressing littermates, we investigated the role of ILK in epidermal S. aureus invasion. Heat-killed, but not live, bacteria were internalized to Rab5- and Rab7-positive phagosomes, and incubation with keratinocyte growth factor increased their uptake 2.5-fold. ILK-deficient mouse keratinocytes internalized bacteria 2- to 4-fold less efficiently than normal cells. The reduced invasion by live S. aureus of ILK-deficient cells was restored in the presence of exogenous, constitutively active Rac1. Thus, Rac1 functions downstream from ILK during invasion. Further, invasion by S. aureus of Rac1-deficient cells was 2.5-fold lower than in normal cells. Paradoxically, staphylococcal cutaneous penetration of mouse skin explants with ILK-deficient epidermis was 35-fold higher than that of normal skin, indicating defects in epidermal barrier function in the absence of ILK. Thus, we identified an ILK-Rac1 pathway essential for bacterial invasion of keratinocytes, and established ILK as a key contributor to prevent invasive staphylococcal cutaneous infection. PMID:25416549

  9. Hospital industry pushes back against the RACs.

    PubMed

    2013-01-01

    Groups ranging from the American Hospital Association to the U.S. Congress have taken up the issues posed by the Recovery Audit Contractors and other Medicare and Medicaid auditors. The high percentage of denials overturned upon appeal and large number of records requests are getting attention. Hospitals may get relief, but it's not likely to be immediate so they should continue preparing for the audits. Meanwhile, in addition to the Recovery Audit Contractors (RACs), hospitals are facing scrutiny from the Zoned Program Integrity Contractors (ZPICs), Medicare Prepayment Reviews, and Medicare Administrative Contractor (MAC) on-site audits. PMID:23339269

  10. 75 FR 54846 - Hood/Willamette Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-09

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Hood/Willamette Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Action of meeting. SUMMARY: The Hood/Willamette Resource Advisory Committee (RAC... FURTHER INFORMATION CONTACT: For more information regarding this meeting, contact Connie Athman; Mt....

  11. 75 FR 21220 - Hood/Willamette Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-23

    ... Forest Service Hood/Willamette Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Action of meeting. SUMMARY: The Hood/Willamette Resource Advisory Committee (RAC) will meet on Tuesday... meeting, contact Connie Athman; Mt. Hood National Forest; 16400 Champion Way; Sandy, Oregon 97055;...

  12. 75 FR 18144 - Hood/Willamette Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-09

    ...; ] DEPARTMENT OF AGRICULTURE Hood/Willamette Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Hood/Willamette Resource Advisory Committee (RAC) will meet on... INFORMATION CONTACT: For more information regarding this meeting, contact Connie Athman; Mt. Hood...

  13. 76 FR 39434 - Notice of Utah's Resource Advisory Council (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-06

    ... Bureau of Land Management Notice of Utah's Resource Advisory Council (RAC) AGENCY: Bureau of Land Management, Interior. ACTION: Notice of Utah's Resource Advisory Council (RAC). SUMMARY: In accordance with... Park & Ride, and Friday, August 5, 2011, (8:30 a.m.--3:30 p.m.) in Salt Lake City, Utah. ADDRESSES:...

  14. 75 FR 11104 - Del Norte Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-10

    ... Forest Service Del Norte Resource Advisory Committee (RAC) AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Del Norte Resource Advisory Committee (RAC) will meet in Crescent City... and Designated Federal Official roles and (5) review operational guidelines; (6) selection of...

  15. The biomass derived activated carbon for supercapacitor

    NASA Astrophysics Data System (ADS)

    Senthilkumar, S. T.; Selvan, R. Kalai; Melo, J. S.

    2013-06-01

    In this work, the activated carbon was prepared from biowaste of Eichhornia crassipes by chemical activation method using KOH as the activating agent at various carbonization temperatures (600 °C, 700 °C and 800 °C). The disordered nature, morphology and surface functional groups of ACs were examined by XRD, SEM and FT-IR. The electrochemical properties of AC electrodes were studied in 1M H2SO4 in the potential range of -0.2 to 0.8 V using cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques in a three electrode system. Subsequently, the fabricated supercapacitor using AC electrode delivered the higher specific capacitance and energy density of 509 F/g at current density of 1 mA/cm2 and 17 Wh/kg at power density of 0.416 W/g.

  16. Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Dolah, B. N. M.; Othman, M. A. R.; Deraman, M.; Basri, N. H.; Farma, R.; Talib, I. A.; Ishak, M. M.

    2013-04-01

    Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburg's slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

  17. Rac-mediated actin remodeling and myosin II are involved in KATP channel trafficking in pancreatic β-cells

    PubMed Central

    Han, Young-Eun; Lim, Ajin; Park, Sun-Hyun; Chang, Sunghoe; Lee, Suk-Ho; Ho, Won-Kyung

    2015-01-01

    AMP-activated protein kinase (AMPK) is a metabolic sensor activated during metabolic stress and it regulates various enzymes and cellular processes to maintain metabolic homeostasis. We previously reported that activation of AMPK by glucose deprivation (GD) and leptin increases KATP currents by increasing the surface levels of KATP channel proteins in pancreatic β-cells. Here, we show that the signaling mechanisms that mediate actin cytoskeleton remodeling are closely associated with AMPK-induced KATP channel trafficking. Using F-actin staining with Alexa 633-conjugated phalloidin, we observed that dense cortical actin filaments present in INS-1 cells cultured in 11 mM glucose were disrupted by GD or leptin treatment. These changes were blocked by inhibiting AMPK using compound C or siAMPK and mimicked by activating AMPK using AICAR, indicating that cytoskeletal remodeling induced by GD or leptin was mediated by AMPK signaling. AMPK activation led to the activation of Rac GTPase and the phosphorylation of myosin regulatory light chain (MRLC). AMPK-dependent actin remodeling induced by GD or leptin was abolished by the inhibition of Rac with a Rac inhibitor (NSC23766), siRac1 or siRac2, and by inhibition of myosin II with a myosin ATPase inhibitor (blebbistatin). Immunocytochemistry, surface biotinylation and electrophysiological analyses of KATP channel activity and membrane potentials revealed that AMPK-dependent KATP channel trafficking to the plasma membrane was also inhibited by NSC23766 or blebbistatin. Taken together, these results indicate that AMPK/Rac-dependent cytoskeletal remodeling associated with myosin II motor function promotes the translocation of KATP channels to the plasma membrane in pancreatic β-cells. PMID:26471000

  18. Modulation of dendritic spines and synaptic function by Rac1: A possible link to Fragile X syndrome pathology

    PubMed Central

    Bongmba, Odelia Y. N.; Martinez, Luis A.; Elhardt, Mary E.; Butler, Karlis; Tejada-Simon, Maria V.

    2011-01-01

    Rac1, a protein of the Rho GTPase subfamily, has been implicated in neuronal and spine development as well as the formation of synapses with appropriate partners. Dendrite and spine abnormalities have been implicated in several psychiatric disorders such as Fragile-X syndrome, where neurons show a high density of long, thin, and immature dendritic spines. Although abnormalities in dendrites and spines have been correlated with impaired cognitive abilities in mental retardation, the causes of these malformations are not yet well understood. Fragile X syndrome is the most common type of inherited mental retardation caused by the absence of FMRP protein, a RNA-binding protein implicated in the regulation of mRNA translation and transport, leading to protein synthesis. We suggest that FMRP might act as a negative regulator on the synthesis of Rac1. Maintaining an optimal level of Rac1 and facilitating the reorganization of the cytoskeleton likely leads to normal neuronal morphology during activity-dependent plasticity. In our study, we first demonstrated that Rac1 is not only associated but necessary for normal spine development and long-term synaptic plasticity. We further showed that, in Fmr1 knockout mice, lack of FMRP induces an overactivation of Rac1 in the mouse brain and other organs that have been shown to be altered in Fragile X syndrome. In those animals, pharmacological manipulation of Rac1 partially reverses their altered long-term plasticity. Thus, regulation of Rac1 may provide a functional link among deficient neuronal morphology, aberrant synaptic plasticity and cognition impairment in Fragile X syndrome. PMID:21645877

  19. Glutaminase 2 is a novel negative regulator of small GTPase Rac1 and mediates p53 function in suppressing metastasis

    PubMed Central

    Zhang, Cen; Liu, Juan; Zhao, Yuhan; Yue, Xuetian; Zhu, Yu; Wang, Xiaolong; Wu, Hao; Blanco, Felix; Li, Shaohua; Bhanot, Gyan; Haffty, Bruce G; Hu, Wenwei; Feng, Zhaohui

    2016-01-01

    Glutaminase (GLS) isoenzymes GLS1 and GLS2 are key enzymes for glutamine metabolism. Interestingly, GLS1 and GLS2 display contrasting functions in tumorigenesis with elusive mechanism; GLS1 promotes tumorigenesis, whereas GLS2 exhibits a tumor-suppressive function. In this study, we found that GLS2 but not GLS1 binds to small GTPase Rac1 and inhibits its interaction with Rac1 activators guanine-nucleotide exchange factors, which in turn inhibits Rac1 to suppress cancer metastasis. This function of GLS2 is independent of GLS2 glutaminase activity. Furthermore, decreased GLS2 expression is associated with enhanced metastasis in human cancer. As a p53 target, GLS2 mediates p53’s function in metastasis suppression through inhibiting Rac1. In summary, our results reveal that GLS2 is a novel negative regulator of Rac1, and uncover a novel function and mechanism whereby GLS2 suppresses metastasis. Our results also elucidate a novel mechanism that contributes to the contrasting functions of GLS1 and GLS2 in tumorigenesis. DOI: http://dx.doi.org/10.7554/eLife.10727.001 PMID:26751560

  20. FilGAP and its close relatives: a mediator of Rho-Rac antagonism that regulates cell morphology and migration.

    PubMed

    Nakamura, Fumihiko

    2013-07-01

    Cell migration, phagocytosis and cytokinesis are mechanically intensive cellular processes that are mediated by the dynamic assembly and contractility of the actin cytoskeleton. GAPs (GTPase-activating proteins) control activities of the Rho family proteins including Cdc42, Rac1 and RhoA, which are prominent upstream regulators of the actin cytoskeleton. The present review concerns a class of Rho GAPs, FilGAP (ARHGAP24 gene product) and its close relatives (ARHGAP22 and AHRGAP25 gene products). FilGAP is a GAP for Rac1 and a binding partner of FLNa (filamin A), a widely expressed F-actin (filamentous actin)-cross-linking protein that binds many different proteins that are important in cell regulation. Phosphorylation of FilGAP serine/threonine residues and binding to FLNa modulate FilGAP's GAP activity and, as a result, its ability to regulate cell protrusion and spreading. FLNa binds to FilGAP at F-actin-enriched sites, such as at the leading edge of the cell where Rac1 activity is controlled to inhibit actin assembly. FilGAP then dissociates from FLNa in actin networks by myosin-dependent mechanical deformation of FLNa's FilGAP-binding site to relocate at the plasma membrane by binding to polyphosphoinositides. Since actomyosin contraction is activated downstream of RhoA-ROCK (Rho-kinase), RhoA activity regulates Rac1 through FilGAP by signalling to the force-generating system. FilGAP and the ARHGAP22 gene product also act as mediators between RhoA and Rac1 pathways, which lead to amoeboid and mesenchymal modes of cell movements respectively. Therefore FilGAP and its close relatives are key regulators that promote the reciprocal inhibitory relationship between RhoA and Rac1 in cell shape changes and the mesenchymal-amoeboid transition in tumour cells. PMID:23763313

  1. Tetrandrine inhibits migration and invasion of rheumatoid arthritis fibroblast-like synoviocytes through down-regulating the expressions of Rac1, Cdc42, and RhoA GTPases and activation of the PI3K/Akt and JNK signaling pathways.

    PubMed

    Lv, Qi; Zhu, Xian-Yang; Xia, Yu-Feng; Dai, Yue; Wei, Zhi-Feng

    2015-11-01

    Tetrandrine (Tet), the main active constituent of Stephania tetrandra root, has been demonstrated to alleviate adjuvant-induced arthritis in rats. The present study was designed to investigate the effects of Tet on the migration and invasion of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and explore the underlying mechanisms. By using cultures of primary FLS isolated from synoviums of RA patients and cell line MH7A, Tet (0.3, 1 μmol·L(-1)) was proven to significantly impede migration and invasion of RA-FLS, but not cell proliferation. Tet also greatly reduced the activation and expressions of matrix degrading enzymes MMP-2/9, the expression of F-actin and the activation of FAK, which controlled the morphologic changes in migration process of FLS. To identify the key signaling pathways by which Tet exerts anti-migration effect, the specific inhibitors of multiple signaling pathways LY294002, Triciribine, SP600125, U0126, SB203580, and PDTC (against PI3K, Akt, JNK, ERK, p38 MAPK and NF-κB-p65, respectively) were used. Among them, LY294002, Triciribine, and SP600125 were shown to obviously inhibit the migration of MH7A cells. Consistently, Tet was able to down-regulate the activation of Akt and JNK as demonstrated by Western blotting assay. Moreover, Tet could reduce the expressions of migration-related proteins Rho GTPases Rac1, Cdc42, and RhoA in MH7A cells. In conclusion, Tet can impede the migration and invasion of RA-FLS, which provides a plausible explanation for its protective effect on RA. The underlying mechanisms involve the reduction of the expressions of Rac1, Cdc42, and RhoA, inhibition of the activation of Akt and JNK, and subsequent down-regulation of activation and/or expressions of MMP-2/9, F-actin, and FAK. PMID:26614458

  2. Carbon nanomaterials: Biologically active fullerene derivatives.

    PubMed

    Bogdanović, Gordana; Djordjević, Aleksandar

    2016-01-01

    Since their discovery, fullerenes, carbon nanotubes, and graphene attract significant attention of researches in various scientific fields including biomedicine. Nano-scale size and a possibility for diverse surface modifications allow carbon nanoallotropes to become an indispensable nanostructured material in nanotechnologies, including nanomedicine. Manipulation of surface chemistry has created diverse populations of water-soluble derivatives of fullerenes, which exhibit different behaviors. Both non-derivatized and derivatized fullerenes show various biological activities. Cellular processes that underline their toxicity are oxidative, genotoxic, and cytotoxic responses.The antioxidant/cytoprotective properties of fullerenes and derivatives have been considered in the prevention of organ oxidative damage and treatment. The same unique physiochemical properties of nanomaterials may also be associated with potential health hazards. Non-biodegradability and toxicity of carbon nanoparticles still remain a great concern in the area of biomedical application. In this review, we report on basic physical and chemical properties of carbon nano-clusters--fullerenes, nanotubes, and grapheme--their specificities, activities, and potential application in biological systems. Special emphasis is given to our most important results obtained in vitro and in vivo using polyhydroxylated fullerene derivative C₆₀(OH)₂₄. PMID:27483572

  3. Inhibition of prostate smooth muscle contraction and prostate stromal cell growth by the inhibitors of Rac, NSC23766 and EHT1864

    PubMed Central

    Wang, Y; Kunit, T; Ciotkowska, A; Rutz, B; Schreiber, A; Strittmatter, F; Waidelich, R; Liu, C; Stief, C G; Gratzke, C; Hennenberg, M

    2015-01-01

    Background and Purpose Medical therapy of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) targets smooth muscle contraction in the prostate, or prostate growth. However, current therapeutic options are insufficient. Here, we investigated the role of Rac in the control of smooth muscle tone in human prostates and growth of prostate stromal cells. Experimental Approach Experiments were performed using human prostate tissues from radical prostatectomy and cultured stromal cells (WPMY-1). Expression of Rac was examined by Western blot and fluorescence staining. Effects of Rac inhibitors (NSC23766 and EHT1864) on contractility were assessed in the organ bath. The effects of Rac inhibitors were assessed by pull-down, cytotoxicity using a cell counting kit, cytoskeletal organization by phalloidin staining and cell growth using an 5-ethynyl-2′-deoxyuridine assay. Key Results Expression of Rac1–3 was observed in prostate samples from each patient. Immunoreactivity for Rac1–3 was observed in the stroma, where it colocalized with the smooth muscle marker, calponin. NSC23766 and EHT1864 significantly reduced contractions of prostate strips induced by noradrenaline, phenylephrine or electrical field stimulation. NSC23766 and EHT1864 inhibited Rac activity in WPMY-1 cells. Survival of WPMY-1 cells ranged between 64 and 81% after incubation with NSC23766 (50 or 100 μM) or EHT1864 (25 μM) for 24 h. NSC23766 and EHT1864 induced cytoskeletal disorganization in WPMY-1 cells. Both inhibitors impaired the growth of WPMY-1 cells. Conclusions and Implications Rac may be a link connecting the control of prostate smooth muscle tone with proliferation of smooth muscle cells. Improvements in LUTS suggestive of BPH by Rac inhibitors appears possible. PMID:25631101

  4. Enhanced capacitive properties of commercial activated carbon by re-activation in molten carbonates

    NASA Astrophysics Data System (ADS)

    Lu, Beihu; Xiao, Zuoan; Zhu, Hua; Xiao, Wei; Wu, Wenlong; Wang, Dihua

    2015-12-01

    Simple, affordable and green methods to improve capacitive properties of commercial activated carbon (AC) are intriguing since ACs possess a predominant role in the commercial supercapacitor market. Herein, we report a green reactivation of commercial ACs by soaking ACs in molten Na2CO3-K2CO3 (equal in mass ratios) at 850 °C combining the merits of both physical and chemical activation strategies. The mechanism of molten carbonate treatment and structure-capacitive activity correlations of the ACs are rationalized. Characterizations show that the molten carbonate treatment increases the electrical conductivity of AC without compromising its porosity and wettability of electrolytes. Electrochemical tests show the treated AC exhibited higher specific capacitance, enhanced high-rate capability and excellent cycle performance, promising its practical application in supercapacitors. The present study confirms that the molten carbonate reactivation is a green and effective method to enhance capacitive properties of ACs.

  5. Kinetics of adsorption with granular, powdered, and fibrous activated carbon

    SciTech Connect

    Shmidt, J.L.; Pimenov, A.V.; Lieberman, A.I.; Cheh, H.Y.

    1997-08-01

    The properties of three different types of activated carbon, fibrous, powdered, and granular, were investigated theoretically and experimentally. The adsorption rate of the activated carbon fiber was found to be two orders of magnitude higher than that of the granular activated carbon, and one order of magnitude higher than that of the powdered activated carbon. Diffusion coefficients of methylene blue in the fibrous, powdered, and granular activated carbons were determined experimentally. A new method for estimating the meso- and macropore surface areas in these carbons was proposed.

  6. Adsorption of chlorophenols on granular activated carbon

    SciTech Connect

    Yang, M.

    1993-12-31

    Studies were undertaken of the adsorption of chlorinated phenols from aqueous solution on granular activated carbon (Filtrasorb-400, 30 x 40 mesh). Single-component equilibrium adsorption data on the eight compounds in two concentration ranges at pH 7.0 fit the Langmuir equation better than the Freundlich equation. The adsorptive capacities at pH 7.0 increase from pentachlorophenol to trichlorophenols and are fairly constant from trichlorophenols to monochlorophenols. The adsorption process was found to be exothermic for pentachlorophenol and 2,4,6-trichlorophenol, and endothermic for 2,4-dichlorophenol and 4-chlorophenol. Equilibrium measurements were also conducted for 2,4,5-trichlorophenol, 2,4-dichlorophenol, and 4-chlorophenol over a wide pH range. A surface complexation model was proposed to describe the effect of pH on adsorption equilibria of chlorophenols on activated carbon. The simulations of the model are in excellent agreement with the experimental data. Batch kinetics studies were conducted of the adsorption of chlorinated phenols on granular activated carbon. The results show that the surface reaction model best describes both the short-term and long-term kinetics, while the external film diffusion model describes the short-term kinetics data very well and the linear-driving-force approximation improved its performance for the long-term kinetics. Multicomponent adsorption equilibria of chlorophenols on granular activated carbon was investigated in the micromolar equilibrium concentration range. The Langmuir competitive and Ideal Adsorbed Solution (IAS) models were tested for their performance on the three binary systems of pentachlorophenol/2,4,6-trichlorophenol, 2,4,6-trichlorophenol/2,4-dichlorophenol, and 2,4-dichlorophenol/4-chlorophenol, and the tertiary system of 2,4,6-trichlorophenol/2,4-dichlorophenol/4-chlorophenol, and found to fail to predict the two-component adsorption equilibria of the former two binary systems and the tertiary system.

  7. Stereoselective Alkali-Metal Catalysts for Highly Isotactic Poly(rac-lactide) Synthesis.

    PubMed

    Sun, Yangyang; Xiong, Jiao; Dai, Zhongran; Pan, Xiaobo; Tang, Ning; Wu, Jincai

    2016-01-01

    A high degree of chain end control in the isoselective ring-opening polymerization (ROP) of rac-lactide is a challenging research goal. In this work, eight highly active sodium and potassium phenolates as highly isoselective catalysts for the ROP of rac-lactide are reported. The best isoselectivity value of Pm = 0.94 is achieved. The isoselective mechanism is chain-end control through the analysis of the stereoerrors in the microstructure of a final polymer; thus, isotactic multiblock structure polymers are obtained, and the highest melt point can reach 192.5 °C. The donating group in phenolate can clearly accelerate the ROP reaction, potassium complexes are more active than the analogous sodium complexes, and the big spacial hindrance of the ligand can decrease the activity. The high isoselectivities of these complexes mostly result from their sandwich structure constructed by the plane of the crown and the plane of the anthryl group. PMID:26684962

  8. Aqueous mercury adsorption by activated carbons.

    PubMed

    Hadi, Pejman; To, Ming-Ho; Hui, Chi-Wai; Lin, Carol Sze Ki; McKay, Gordon

    2015-04-15

    Due to serious public health threats resulting from mercury pollution and its rapid distribution in our food chain through the contamination of water bodies, stringent regulations have been enacted on mercury-laden wastewater discharge. Activated carbons have been widely used in the removal of mercuric ions from aqueous effluents. The surface and textural characteristics of activated carbons are the two decisive factors in their efficiency in mercury removal from wastewater. Herein, the structural properties and binding affinity of mercuric ions from effluents have been presented. Also, specific attention has been directed to the effect of sulfur-containing functional moieties on enhancing the mercury adsorption. It has been demonstrated that surface area, pore size, pore size distribution and surface functional groups should collectively be taken into consideration in designing the optimal mercury removal process. Moreover, the mercury adsorption mechanism has been addressed using equilibrium adsorption isotherm, thermodynamic and kinetic studies. Further recommendations have been proposed with the aim of increasing the mercury removal efficiency using carbon activation processes with lower energy input, while achieving similar or even higher efficiencies. PMID:25644627

  9. APPRAISAL OF POWDERED ACTIVATED CARBON PROCESSES FOR MUNICIPAL WASTEWATER TREATMENT

    EPA Science Inventory

    Powdered activated carbon has been the subject of several developmental efforts directed towards producing improved methods for treating municipal wastewaters. Granular activated carbon has proven itself as an effective means of reducing dissolved organic contaminant levels, but ...

  10. The Small GTPases RhoA and Rac1 Regulate Cerebellar Development by Controlling Cell Morphogenesis, Migration and Foliation

    PubMed Central

    Mulherkar, Shalaka; Uddin, Mohammad Danish; Couvillon, Anthony D.; Sillitoe, Roy V.; Tolias, Kimberley F.

    2014-01-01

    The small GTPases RhoA and Rac1 are key cytoskeletal regulators that function in a mutually antagonistic manner to control the migration and morphogenesis of a broad range of cell types. However, their role in shaping the cerebellum, a unique brain structure composed of an elaborate set of folia separated by fissures of different lengths, remains largely unexplored. Here we show that dysregulation of both RhoA and Rac1 signaling results in abnormal cerebellar ontogenesis. Ablation of RhoA from neuroprogenitor cells drastically alters the timing and placement of fissure formation, the migration and positioning of granule and Purkinje cells, the alignment of Bergmann glia, and the integrity of the basement membrane, primarily in the anterior lobules. Furthermore, in the absence of RhoA, granule cell precursors located at the base of fissures fail to undergo cell shape changes required for fissure initiation. Many of these abnormalities can be recapitulated by deleting RhoA specifically from granule cell precursors but not postnatal glia, indicating that RhoA functions in granule cell precursors to control cerebellar morphogenesis. Notably, mice with elevated Rac1 activity due to loss of the Rac1 inhibitors Bcr and Abr show similar anterior cerebellar deficits, including ectopic neurons and defects in fissure formation, Bergmann glia organization and basement membrane integrity. Together, our results suggest that RhoA and Rac1 play indispensable roles in patterning cerebellar morphology. PMID:25128586

  11. Raft endocytosis of AMF regulates mitochondrial dynamics through Rac1 signaling and the Gp78 ubiquitin ligase.

    PubMed

    Shankar, Jay; Kojic, Liliana D; St-Pierre, Pascal; Wang, Peter T C; Fu, Min; Joshi, Bharat; Nabi, Ivan R

    2013-08-01

    Gp78 is a cell surface receptor that also functions as an E3 ubiquitin ligase in the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway. The Gp78 ligand, the glycolytic enzyme phosphoglucose isomerase (PGI; also called autocrine motility factor, AMF), functions as a cytokine upon secretion by tumor cells. AMF is internalized through a PI3K- and dynamin-dependent raft endocytic pathway to the smooth ER; however, the relationship between AMF and Gp78 ubiquitin ligase activity remains unclear. AMF uptake to the smooth ER is inhibited by the dynamin inhibitor, dynasore, is reduced in Gp78 knockdown cells and induces the dynamin-dependent downregulation of its cell surface receptor. AMF uptake is Rac1-dependent and is inhibited by expression of dominant-negative Rac1 and the Rac1 inhibitor NSC23766, and is therefore distinct from Cdc42- and RhoA-dependent raft endocytic pathways. AMF stimulates Rac1 activation, but this is reduced by dynasore treatment and is absent in Gp78-knockdown cells; therefore, AMF activities require Gp78-mediated endocytosis. AMF also prevents Gp78-induced degradation of the mitochondrial fusion proteins, mitofusin 1 and 2 in a dynamin-, Rac1- and phosphoinositide 3-kinase (PI3K)-dependent manner. Gp78 induces mitochondrial clustering and fission in a manner dependent on GP78 ubiquitin ligase activity, and this is also reversed by uptake of AMF. The raft-dependent endocytosis of AMF, therefore, promotes Rac1-PI3K signaling that feeds back to promote AMF endocytosis and also inhibits the ability of Gp78 to target the mitofusins for degradation, thereby preventing Gp78-dependent mitochondrial fission. Through regulation of an ER-localized ubiquitin ligase, the raft-dependent endocytosis of AMF represents an extracellular regulator of mitochondrial fusion and dynamics. PMID:23690547

  12. Factors affecting the behavior of unburned carbon upon steam activation

    NASA Astrophysics Data System (ADS)

    Lu, Zhe

    The main objective of this study is to investigate the factors that could affect the behavior of unburned carbon samples upon steam activation. Through this work, the relationships among the factors that could influence the carbon-steam reaction with the surface area of the produced activated carbon were explored. Statistical analysis was used to relate the chemical and physical properties of the unburned carbon to the surface area of the activated carbon. Six unburned carbons were selected as feedstocks for activated carbon, and marked as UCA through UCF. The unburned carbons were activated using steam at 850°C for 90 minutes, and the surface areas of their activated counterparts were measured using N2 adsorption isotherms at 77K. The activated carbons produced from different unburned carbon precursors presented different surface areas at similar carbon burn-off levels. Moreover, in different carbon burn-off regions, the sequences for surface area of activated carbons from different unburned carbon samples were different. The factors that may affect the carbon-steam gasification reactions, including the concentration of carbon active sites, the crystallite size of the carbon, the intrinsic porous structure of carbon, and the inorganic impurities, were investigated. All unburned carbons investigated in this study were similar in that they showed the very broad (002) and (10 ) carbon peaks, which are characteristic of highly disordered carbonaceous materials. In this study, the unburned carbon samples contained about 17--48% of inorganic impurities. Compared to coals, the unburned carbon samples contain a larger amount of inorganic impurities as a result of the burn-off, or at lease part, of the carbon during the combustion process. These inorganic particles were divided into two groups in terms of the way they are associated with carbon particles: free single particles, and particles combined with carbon particles. As indicated from the present work, unburned

  13. 75 FR 52551 - Notice of Utah's Resource Advisory Council (RAC) Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... Bureau of Land Management Notice of Utah's Resource Advisory Council (RAC) Meeting AGENCY: Bureau of Land Management, Interior. ACTION: Notice of Utah's Resource Advisory Council (RAC) Meeting. SUMMARY: In... Advisory Council (RAC) will meet as indicated below. DATES: The Utah RAC will meet Monday, September...

  14. REACTION OF ACTIVATED CARBON WITH AQUEOUS CHLORINE AND CHLORINE DIOXIDE

    EPA Science Inventory

    The objective of this research was to determine whether aqueous chlorine and chlorine dioxide react with activated carbon, or with compounds adsorbed on activated carbon, to produce compounds that would not form in the absence of activated carbon. The experimental conditions were...

  15. Less-costly activated carbon for sewage treatment

    NASA Technical Reports Server (NTRS)

    Ingham, J. D.; Kalvinskas, J. J.; Mueller, W. A.

    1977-01-01

    Lignite-aided sewage treatment is based on absorption of dissolved pollutants by activated carbon. Settling sludge is removed and dried into cakes that are pyrolyzed with lignites to yield activated carbon. Lignite is less expensive than activated carbon previously used to supplement pyrolysis yield.

  16. The impact of RAC audits on US hospitals.

    PubMed

    Harrison, Jeffrey P; Barksdale, Rachel M

    2013-01-01

    The Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (MMA) authorized a three-year demonstration program using recovery audit contractors (RACs) to identify and correct improper payments in the Medicare Fee-For-Service program. More recently, Section 6411 of the Affordable Care Act (ACA) expanded the RAC program to include the Medicaid program. This shows the Cent ers for Medicare & Medicaid Services (CMS) believe RAC audits are a cost-effective method to ensure health care providers are paid correctly and thereby protect the Medicare Trust Fund. RAC audits are highly complex and require significant manpower to handle the large volume of requests received during a short period of time. Additionally, the RAC audit appeal process is complicated and requires a high level of technical expertise. The demonstration project found that RAC audits resulted in sizeable amounts of overpayments collected ("take-backs") from many providers. This research study assesses the potential impact of the RAC audit program on US acute care hospitals. Data obtained from CMS show that RAC overpayments collected for FY 2010 were $75.4 million, increased to $797.4 million in FY 2011, and increased to $986.2 million in the first six months of FY 2012. According to the American Hospital Association (AHA) RACTrac audit survey, the vast majority of these collections represent complex denials where hospitals are required to provide medical record documents in support of their billed claims. This study found that the RAC audit program collections are increasing significantly over time. As a result, these collections are having a significant negative impact on the profitability of US hospitals. PMID:24003757

  17. Rac1 modulates cardiomyocyte adhesion during mouse embryonic development

    SciTech Connect

    Abu-Issa, Radwan

    2015-01-24

    Highlights: • Conditional knockout of Rac1 using Nkx2.5 Cre line is lethal at E13.5. • The myocardium of the mutant is thin and disorganized. • The phenotype is not due to cardiomyocyte low proliferation or apoptosis. • The phenotype is due to specific defect in cardiomyocyte adhesion. - Abstract: Rac1, a member of the Rho subfamily of small GTPases, is involved in morphogenesis and differentiation of many cell types. Here we define a role of Rac1 in cardiac development by specifically deleting Rac1 in the pre-cardiac mesoderm using the Nkx2.5-Cre transgenic driver line. Rac1-conditional knockout embryos initiate heart development normally until embryonic day 11.5 (E11.5); their cardiac mesoderm is specified, and the heart tube is formed and looped. However, by E12.5-E13.5 the mutant hearts start failing and embryos develop edema and hemorrhage which is probably the cause for the lethality observed soon after. The hearts of Rac1-cKO embryos exhibit disorganized and thin myocardial walls and defects in outflow tract alignment. No significant differences of cardiomyocyte death or proliferation were found between developing control and mutant embryos. To uncover the role of Rac1 in the heart, E11.5 primary heart cells were cultured and analyzed in vitro. Rac1-deficient cardiomyocytes were less spread, round and loosely attached to the substrate and to each other implying that Rac1-mediated signaling is required for appropriate cell–cell and/or cellmatrix adhesion during cardiac development.

  18. Hierarchically structured activated carbon for ultracapacitors

    NASA Astrophysics Data System (ADS)

    Kim, Mok-Hwa; Kim, Kwang-Bum; Park, Sun-Min; Roh, Kwang Chul

    2016-02-01

    To resolve the pore-associated bottleneck problem observed in the electrode materials used for ultracapacitors, which inhibits the transport of the electrolyte ions, we designed hierarchically structured activated carbon (HAC) by synthesizing a mesoporous silica template/carbon composite and chemically activating it to simultaneously remove the silica template and increase the pore volume. The resulting HAC had a well-designed, unique porous structure, which allowed for large interfaces for efficient electric double-layer formation. Given the unique characteristics of the HAC, we believe that the developed synthesis strategy provides important insights into the design and fabrication of hierarchical carbon nanostructures. The HAC, which had a specific surface area of 1,957 m2 g-1, exhibited an extremely high specific capacitance of 157 F g-1 (95 F cc-1), as well as a high rate capability. This indicated that it had superior energy storage capability and was thus suitable for use in advanced ultracapacitors.

  19. Hierarchically structured activated carbon for ultracapacitors

    PubMed Central

    Kim, Mok-Hwa; Kim, Kwang-Bum; Park, Sun-Min; Roh, Kwang Chul

    2016-01-01

    To resolve the pore-associated bottleneck problem observed in the electrode materials used for ultracapacitors, which inhibits the transport of the electrolyte ions, we designed hierarchically structured activated carbon (HAC) by synthesizing a mesoporous silica template/carbon composite and chemically activating it to simultaneously remove the silica template and increase the pore volume. The resulting HAC had a well-designed, unique porous structure, which allowed for large interfaces for efficient electric double-layer formation. Given the unique characteristics of the HAC, we believe that the developed synthesis strategy provides important insights into the design and fabrication of hierarchical carbon nanostructures. The HAC, which had a specific surface area of 1,957 m2 g−1, exhibited an extremely high specific capacitance of 157 F g−1 (95 F cc−1), as well as a high rate capability. This indicated that it had superior energy storage capability and was thus suitable for use in advanced ultracapacitors. PMID:26878820

  20. Chemoenzymatic resolution of rac-malathion

    PubMed Central

    Hitt, David M.; Belabassi, Yamina; Suhy, Joyce; Berkman, Clifford E.; Thompson, Charles M.

    2014-01-01

    Malathion, diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate, is an organophosphate used to control insect pests. Malathion contains a diethyl succinate moiety that is a known functional group susceptible to desymmetrizing enzymes such as esterases that selectively react with a single enantiomer. Purified rac-malathion was subjected to hydrolysis at the diethyl succinate moiety of malathion under various conditions using wild type pig liver esterase to form (S)-malathion (12 % ee) and ~ 3:2 mixture of α- and β-monoacids of (R)-malathion. Technical malathion could not be enriched due to the presence of esterase inhibitors. Further investigation of this resolution using a panel of six PLE isoenzymes also demonstrated formation of (S)-malathion, however, an improvement of up to 56 % ee was obtained. PMID:24839353

  1. Vitreous-induced cytoskeletal rearrangements via the Rac1 GTPase-dependent signaling pathway in human retinal pigment epithelial cells

    SciTech Connect

    Huang, Xionggao; Wei, Yantao; Ma, Haizhi; Zhang, Shaochong

    2012-03-09

    Highlights: Black-Right-Pointing-Pointer Vitreous induces morphological changes and cytoskeletal rearrangements in RPE cells. Black-Right-Pointing-Pointer Rac1 is activated in vitreous-transformed RPE cells. Black-Right-Pointing-Pointer Rac inhibition prevents morphological changes in vitreous-transformed RPE cells. Black-Right-Pointing-Pointer Rac inhibition suppresses cytoskeletal rearrangements in vitreous-transformed RPE cells. Black-Right-Pointing-Pointer The vitreous-induced effects are mediated by a Rac1 GTPase/LIMK1/cofilin pathway. -- Abstract: Proliferative vitreoretinopathy (PVR) is mainly caused by retinal pigment epithelial (RPE) cell migration, invasion, proliferation and transformation into fibroblast-like cells that produce the extracellular matrix (ECM). The vitreous humor is known to play an important role in PVR. An epithelial-to-mesenchymal transdifferentiation (EMT) of human RPE cells induced by 25% vitreous treatment has been linked to stimulation of the mesenchymal phenotype, migration and invasion. Here, we characterized the effects of the vitreous on the cell morphology and cytoskeleton in human RPE cells. The signaling pathway that mediates these effects was investigated. Serum-starved RPE cells were incubated with 25% vitreous, and the morphological changes were examined by phase-contrast microscopy. Filamentous actin (F-actin) was examined by immunofluorescence and confocal microscopy. Protein phosphorylation of AKT, ERK1/2, Smad2/3, LIM kinase (LIMK) 1 and cofilin was analyzed by Western blot analysis. Vitreous treatment induced cytoskeletal rearrangements, activated Rac1 and enhanced the phosphorylation of AKT, ERK1/2 and Smad2/3. When the cells were treated with a Rac activation-specific inhibitor, the cytoskeletal rearrangements were prevented, and the phosphorylation of Smad2/3 was blocked. Vitreous treatment also enhanced the phosphorylation of LIMK1 and cofilin and the Rac inhibitor blocked this effect. We propose that vitreous

  2. Rac1 recruitment to the archipelago structure of the focal adhesion through the fluid membrane as revealed by single-molecule analysis.

    PubMed

    Shibata, Akihiro C E; Chen, Limin H; Nagai, Rie; Ishidate, Fumiyoshi; Chadda, Rahul; Miwa, Yoshihiro; Naruse, Keiji; Shirai, Yuki M; Fujiwara, Takahiro K; Kusumi, Akihiro

    2013-03-01

    The focal adhesion (FA) is an integrin-based structure built in/on the plasma membrane (PM), linking the extracellular matrix to the actin stress-fibers, working as cell migration scaffolds. Previously, we proposed the archipelago architecture of the FA, in which FA largely consists of fluid membrane, dotted with small islands accumulating FA proteins: membrane molecules enter the inter-island channels in the FA zone rather freely, and the integrins in the FA-protein islands rapidly exchanges with those in the bulk membrane. Here, we examined how Rac1, a small G-protein regulating FA formation, and its activators αPIX and βPIX, are recruited to the FA zones. PIX molecules are recruited from the cytoplasm to the FA zones directly. In contrast, majorities of Rac1 molecules first arrive from the cytoplasm on the general inner PM surface, and then enter the FA zones via lateral diffusion on the PM, which is possible due to rapid Rac1 diffusion even within the FA zones, slowed only by a factor of two to four compared with that outside. The constitutively-active Rac1 mutant exhibited temporary and all-time immobilizations in the FA zone, suggesting that upon PIX-induced Rac1 activation at the FA-protein islands, Rac1 tends to be immobilized at the FA-protein islands. PMID:23341328

  3. Rac1 modulates the formation of primordial follicles by facilitating STAT3-directed Jagged1, GDF9 and BMP15 transcription in mice

    PubMed Central

    Zhao, Lihua; Du, Xinhua; Huang, Kun; Zhang, Tuo; Teng, Zhen; Niu, Wanbao; Wang, Chao; Xia, Guoliang

    2016-01-01

    The size of the primordial follicle pool determines the reproductive potential of mammalian females, and establishment of the pool is highly dependent on specific genes expression. However, the molecular mechanisms by which the essential genes are regulated coordinately to ensure primordial follicle assembly remain a mystery. Here, we show that the small GTPase Rac1 plays an indispensable role in controlling the formation of primordial follicles in mouse ovary. Employing fetal mouse ovary organ culture system, we demonstrate that disruption of Rac1 retarded the breakdown of germline cell cysts while Rac1 overexpression accelerated the formation of primordial follicles. In addition, in vivo inhibitor injection resulted in the formation of multi-oocyte follicles. Subsequent investigation showed that Rac1 induced nuclear import of STAT3 by physical binding. In turn, nuclear STAT3 directly activated the transcription of essential oocyte-specific genes, including Jagged1, GDF9, BMP15 and Nobox. Further, GDF9 and BMP15 regulated the translation of Notch2 via mTORC1 activation in pregranulosa cells. Overexression or addition of Jagged1, GDF9 and BMP15 not only reversed the effect of Rac1 disruption, but also accelerated primordial follicle formation via Notch2 signaling activation. Collectively, these results indicate that Rac1 plays important roles as a key regulator in follicular assembly. PMID:27050391

  4. MT1-MMP is required for myeloid cell fusion via regulation of Rac1 signaling

    PubMed Central

    Gonzalo, Pilar; Guadamillas, Marta C.; Hernández-Riquer, Mª Victoria; Pollán, Ángela; Grande-García, Araceli; Bartolomé, Rubén A.; Vasanji, Amit; Ambrogio, Chiara; Chiarle, Roberto; Teixidó, Joaquín; Risteli, Juha; Apte, Suneel S.; del Pozo, Miguel A.; Arroyo, Alicia G.

    2009-01-01

    SUMMARY Cell fusion is essential for fertilization, myotube formation, and inflammation. Macrophages fuse in various circumstances but the molecular signals involved in the distinct steps of their fusion are not fully characterized. Using null mice and derived cells, we show that the protease MT1-MMP is necessary for macrophage fusion during osteoclast and giant cell formation in vitro and in vivo. Specifically, MT1-MMP is required for lamellipodia formation and for proper cell morphology and motility of bone marrow myeloid progenitors prior to membrane fusion. These functions of MT1-MMP do not depend on MT1-MMP catalytic activity or downstream pro-MMP-2 activation. Instead, MT1-MMP-null cells show a decreased Rac1 activity and reduced membrane targeting of Rac1 and the adaptor protein p130Cas. Retroviral rescue experiments and protein binding assays delineate a signaling pathway in which MT1-MMP, via its cytosolic tail, contributes to macrophage migration and fusion by regulating Rac1 activity through an association with p130Cas. PMID:20152179

  5. Theoretical study of carbon dioxide activation by metals (Co, Cu, Ni) supported on activated carbon.

    PubMed

    Ha, Nguyen Ngoc; Ha, Nguyen Thi Thu; Van Khu, Le; Cam, Le Minh

    2015-12-01

    The activation of carbon dioxide (CO2) by catalytic systems comprising a transition metal (Co, Cu,Ni) on an activated carbon (AC) support was investigated using a combination of different theoretical calculation methods: Monte Carlo simulation, DFT and DFT-D, molecular dynamics (MD), and a climbing image nudged elastic band (CI-NEB) method. The results obtained indicate that CO2 is easily adsorbed by AC or MAC (M: Cu, Co, Ni). The results also showed that the process of adsorbing CO2 does not involve a transition state, and that NiAC and CoAC are the most effective of the MAC catalysts at adsorbing CO2. Adsorption on NiAC led to the strongest activation of the C-O bond, while adsorption on CuAC led to the weakest activation. Graphical Abstract Models of CO2 activation on: a)- activated carbon; b)- metal supported activated carbon (M-AC), where M: Co, Cu, Ni. PMID:26637187

  6. Loss of Either Rac1 or Rac3 GTPase Differentially Affects the Behavior of Mutant Mice and the Development of Functional GABAergic Networks

    PubMed Central

    Pennucci, Roberta; Talpo, Francesca; Astro, Veronica; Montinaro, Valentina; Morè, Lorenzo; Cursi, Marco; Castoldi, Valerio; Chiaretti, Sara; Bianchi, Veronica; Marenna, Silvia; Cambiaghi, Marco; Tonoli, Diletta; Leocani, Letizia; Biella, Gerardo; D'Adamo, Patrizia; de Curtis, Ivan

    2016-01-01

    Rac GTPases regulate the development of cortical/hippocampal GABAergic interneurons by affecting the early development and migration of GABAergic precursors. We have addressed the function of Rac1 and Rac3 proteins during the late maturation of hippocampal interneurons. We observed specific phenotypic differences between conditional Rac1 and full Rac3 knockout mice. Rac1 deletion caused greater generalized hyperactivity and cognitive impairment compared with Rac3 deletion. This phenotype matched with a more evident functional impairment of the inhibitory circuits in Rac1 mutants, showing higher excitability and reduced spontaneous inhibitory currents in the CA hippocampal pyramidal neurons. Morphological analysis confirmed a differential modification of the inhibitory circuits: deletion of either Rac caused a similar reduction of parvalbumin-positive inhibitory terminals in the pyramidal layer. Intriguingly, cannabinoid receptor-1-positive terminals were strongly increased only in the CA1 of Rac1-depleted mice. This increase may underlie the stronger electrophysiological defects in this mutant. Accordingly, incubation with an antagonist for cannabinoid receptors partially rescued the reduction of spontaneous inhibitory currents in the pyramidal cells of Rac1 mutants. Our results show that Rac1 and Rac3 have independent roles in the formation of GABAergic circuits, as highlighted by the differential effects of their deletion on the late maturation of specific populations of interneurons. PMID:26582364

  7. Zinc Complexes of Sequential Tetradentate Monoanionic Ligands in the Isoselective Polymerization of rac-Lactide.

    PubMed

    Rosen, Tomer; Popowski, Yanay; Goldberg, Israel; Kol, Moshe

    2016-08-01

    Zinc complexes of {ONNN}-type sequential tetradentate monoanionic ligands reacted with diethylzinc to give the mononuclear ethylzinc complexes. The benzyloxy complexes were formed readily and were found to be highly active as well as living/immortal catalysts for ring-opening polymerization of rac-lactic acid with a clear isospecific inclination. Chiral gas chromatography analysis revealed a mild preference for a given lactide enantiomer by the chiral catalysts. PMID:27325142

  8. Vibration damping with active carbon fiber structures

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Kunze, Holger; Riedel, Mathias; Roscher, Hans-Jürgen

    2007-04-01

    This paper presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was done with a finite element model (ANSYS). This paper describes how state space models are generated out of a structure based on the finite element model and how controller codes are integrated into finite element models for transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.

  9. Adsorbed natural gas storage with activated carbon

    SciTech Connect

    Sun, Jian; Brady, T.A.; Rood, M.J.

    1996-12-31

    Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

  10. Charcoal and activated carbon at elevated pressure

    SciTech Connect

    Antal, M.J. Jr.; Dai, Xiangfeng; Norberg, N.

    1995-12-01

    High quality charcoal has been produced with very high yields of 50% to 60% from macadamia nut and kukui nut shells and of 44% to 47% from Eucalyptus and Leucaena wood in a bench scale unit at elevated pressure on a 2 to 3 hour cycle, compared to commercial practice of 25% to 30% yield on a 7 to 12 day operating cycle. Neither air pollution nor tar is produced by the process. The effects of feedstock pretreatments with metal additives on charcoal yield are evaluated in this paper. Also, the influences of steam and air partial pressure and total pressure on yields of activated carbon from high yield charcoal are presented.

  11. Impaired cell death and mammary gland involution in the absence of Dock1 and Rac1 signaling

    PubMed Central

    Bagci, H; Laurin, M; Huber, J; Muller, W J; Côté, J-F

    2014-01-01

    Throughout life, the tight equilibrium between cell death and the prompt clearance of dead corpses is required to maintain a proper tissue homeostasis and prevent inflammation. Following lactation, mammary gland involution is triggered and results in the death of excessive epithelial cells that are rapidly cleared by phagocytes to ensure that the gland returns to its prepregnant state. Orthologs of Dock1 (dedicator of cytokinesis 1), Elmo and Rac1 (ras-related C3 botulinum toxin substrate 1) in Caenorhabditis elegans are part of a signaling module in phagocytes that is linking apoptotic cell recognition to cytoskeletal reorganization required for engulfment. In mammals, Elmo1 was shown to interact with the phosphatidylserine receptor Bai1 and relay signals to promote phagocytosis of apoptotic cells. Still, the role of the RacGEF Dock1 in the clearance of dying cells in mammals was never directly addressed. We generated two mouse models with conditional inactivation of Dock1 and Rac1 and revealed that the expression of these genes is not essential in the mammary gland during puberty, pregnancy and lactation. We induced mammary gland involution in these mice to investigate the role of Dock1/Rac1 signaling in the engulfment of cell corpses. Unpredictably, activation of Stat3 (signal transducer and activator of transcription 3), a key regulator of mammary gland involution, was impaired in the absence of Rac1 and Dock1 expression. Likewise, failure to activate properly Stat3 was coinciding with a significant delay in the initiation and progression of mammary gland involution in mutant animals. By using an in vitro phagocytosis assay, we observed that Dock1 and Rac1 are essential to mediate engulfment in epithelial phagocytes. In vivo, cell corpses accumulated at late time points of involution in Dock1 and Rac1 mutant mammary glands. Overall, our study demonstrated an unsuspected role for Dock1/Rac1 signaling in the initiation of mammary gland involution, and also

  12. Impaired cell death and mammary gland involution in the absence of Dock1 and Rac1 signaling.

    PubMed

    Bagci, H; Laurin, M; Huber, J; Muller, W J; Côté, J-F

    2014-01-01

    Throughout life, the tight equilibrium between cell death and the prompt clearance of dead corpses is required to maintain a proper tissue homeostasis and prevent inflammation. Following lactation, mammary gland involution is triggered and results in the death of excessive epithelial cells that are rapidly cleared by phagocytes to ensure that the gland returns to its prepregnant state. Orthologs of Dock1 (dedicator of cytokinesis 1), Elmo and Rac1 (ras-related C3 botulinum toxin substrate 1) in Caenorhabditis elegans are part of a signaling module in phagocytes that is linking apoptotic cell recognition to cytoskeletal reorganization required for engulfment. In mammals, Elmo1 was shown to interact with the phosphatidylserine receptor Bai1 and relay signals to promote phagocytosis of apoptotic cells. Still, the role of the RacGEF Dock1 in the clearance of dying cells in mammals was never directly addressed. We generated two mouse models with conditional inactivation of Dock1 and Rac1 and revealed that the expression of these genes is not essential in the mammary gland during puberty, pregnancy and lactation. We induced mammary gland involution in these mice to investigate the role of Dock1/Rac1 signaling in the engulfment of cell corpses. Unpredictably, activation of Stat3 (signal transducer and activator of transcription 3), a key regulator of mammary gland involution, was impaired in the absence of Rac1 and Dock1 expression. Likewise, failure to activate properly Stat3 was coinciding with a significant delay in the initiation and progression of mammary gland involution in mutant animals. By using an in vitro phagocytosis assay, we observed that Dock1 and Rac1 are essential to mediate engulfment in epithelial phagocytes. In vivo, cell corpses accumulated at late time points of involution in Dock1 and Rac1 mutant mammary glands. Overall, our study demonstrated an unsuspected role for Dock1/Rac1 signaling in the initiation of mammary gland involution, and also

  13. Rac1 drives intestinal stem cell proliferation and regeneration

    PubMed Central

    Myant, Kevin B; Scopelliti, Alessandro; Haque, Sara; Vidal, Marcos; Sansom, Owen J; Cordero, Julia B

    2013-01-01

    Adult stem cells are responsible for maintaining the balance between cell proliferation and differentiation within self-renewing tissues. The molecular and cellular mechanisms mediating such balance are poorly understood. The production of reactive oxygen species (ROS) has emerged as an important mediator of stem cell homeostasis in various systems. Our recent work demonstrates that Rac1-dependent ROS production mediates intestinal stem cell (ISC) proliferation in mouse models of colorectal cancer (CRC). Here, we use the adult Drosophila midgut and the mouse small intestine to directly address the role of Rac1 in ISC proliferation and tissue regeneration in response to damage. Our results demonstrate that Rac1 is necessary and sufficient to drive ISC proliferation and regeneration in an ROS-dependent manner. Our data point to an evolutionarily conserved role of Rac1 in intestinal homeostasis and highlight the value of combining work in the mammalian and Drosophila intestine as paradigms to study stem cell biology. PMID:23974108

  14. Production of activated carbon from TCR char

    NASA Astrophysics Data System (ADS)

    Stenzel, Fabian; Heberlein, Markus; Klinner, Tobias; Hornung, Andreas

    2016-04-01

    The utilization of char for adsorptive purposes is known since the 18th century. At that time the char was made of wood or bones and used for decoloration of fluids. In the 20th century the production of activated carbon in an industrial scale was started. The today's raw materials for activated carbon production are hard coal, peat, wood or coconut shells. All these materials entail costs especially the latter. Thus, the utilization of carbon rich residues (biomass) is an interesting economic opportunity because it is available for no costs or even can create income. The char is produced by thermo-catalytic reforming (TCR®). This process is a combination of an intermediate pyrolysis and subsequently a reforming step. During the pyrolysis step the material is decomposed in a vapor and a solid carbon enriched phase. In the second step the vapor and the solid phase get in an intensive contact and the quality of both materials is improved via the reforming process. Subsequently, the condensables are precipitated from the vapor phase and a permanent gas as well as oil is obtained. Both are suitable for heat and power production which is a clear advantage of the TCR® process. The obtained biochar from the TCR® process has special properties. This material has a very low hydrogen and oxygen content. Its stability is comparable to hard coal or anthracite. Therefore it consists almost only of carbon and ash. The latter depends from input material. Furthermore the surface structure and area can be influenced during the reforming step. Depending from temperature and residence time the number of micro pores and the surface area can be increased. Preliminary investigations with methylene blue solution have shown that a TCR® char made of digestate from anaerobic digestion has adsorptive properties. The decoloration of the solution was achieved. A further influencing factor of the adsorption performance is the particle size. Based on the results of the preliminary tests a

  15. The Calponin Family Member CHDP-1 Interacts with Rac/CED-10 to Promote Cell Protrusions

    PubMed Central

    Zhang, Jingyan; Liu, Jia-Jia; Wang, Yingchun; Ding, Mei

    2016-01-01

    Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo. PMID:27415421

  16. The Calponin Family Member CHDP-1 Interacts with Rac/CED-10 to Promote Cell Protrusions.

    PubMed

    Guan, Liying; Ma, Xuehua; Zhang, Jingyan; Liu, Jia-Jia; Wang, Yingchun; Ding, Mei

    2016-07-01

    Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo. PMID:27415421

  17. The regeneration of polluted activated carbon by radiation techniques

    NASA Astrophysics Data System (ADS)

    Minghong, Wu; Borong, Bao; Ruimin, Zhou; Jinliang, Zhu; Longxin, Hu

    1998-10-01

    In this paper, the regeneration of used activated carbon from monosodium glutamate factory was experimented using radiation and acid-alkali chemical cleaning method. Results showed that the activated carbon saturated with pollutants can be wash away easily by flushing with chemical solution prior irradiation. DSC was used to monitor the change of carbon adsorption

  18. Preparation of binderless activated carbon monolith from pre-carbonization rubber wood sawdust by controlling of carbonization and activation condition

    NASA Astrophysics Data System (ADS)

    Taer, E.; Deraman, M.; Taslim, R.; Iwantono

    2013-09-01

    Binderless activated carbon monolith (ACM) was prepared from pre-carbonized rubber wood sawdust (RWSD). The effect of the carbonization temperature (400, 500, 600, 700, 800 dan 900 °C) on porosity characteristic of the ACM have been studied. The optimum carbonization temperature for obtaining ACM with high surface area of 600 °C with CO2 activation at 800 °C for one hour. At this condition, the surface area as high as 733 m2 g-1 could be successfully obtained. By improved the activation temperature at 900 °C for 2.5 h, it was found that the surface area of 860 m2 g-1. For this condition, the ACM exhibit the specific capacitance of 90 F g-1. In addition the termogravimertic (TG)-differential termografimertic (DTG) and field emission scanning electron microscope (FESEM) measurement were also performed on the ACMs and the result has been studied. Finally, it was conclude that the high surface area of ACM from RWSD could be produced by proper selections of carbonization and activation condition.

  19. Rac1 and Cdc42 Play Important Roles in Arsenic Neurotoxicity in Primary Cultured Rat Cerebellar Astrocytes.

    PubMed

    An, Yuan; Liu, Tingting; Liu, Xiaona; Zhao, Lijun; Wang, Jing

    2016-03-01

    This study aimed to explore whether Rac1 and Cdc42, representative members of Ras homologue guanosine triphosphatases (Rho GTPases), are involved in neurotoxicity induced by arsenic exposure in rat nervous system. Expressions of Rac1 and Cdc42 in rat cerebellum and cerebrum exposed to different doses of NaAsO2 (Wistar rats drank 0, 2, 10, and 50 mg/L NaAsO2 water for 3 months) were examined. Both Rac1 and Cdc42 expressions increased significantly in a dose-dependent manner in cerebellum (P < 0.01) by Western blot and immunohistochemistry assay, but in cerebrum, Rac1 and Cdc42 expressions only in 2 mg/L exposure groups were significantly higher than those in control groups (P < 0.01). Five to 50 μM NaAsO2 decreased cell viability in a dose-dependent manner in primary cultured rat astrocytes, whereas 1 μM NaAsO2 increased the cell viability in these cells. Rac1 inhibitor, NSC23766, decreased NaAsO2-induced apoptosis and increased the cell viability in primary cultured rat cerebellar astrocytes exposed to 30 μM NaAsO2. Cdc42 inhibitor, ZCL278, increased cell viability in the cells exposed to 30 μM NaAsO2. Taken together, our current studies in vivo and in vitro indicate that activations of Rac1 and Cdc42 play a very important role in arsenic neurotoxicity in rat cerebellum, providing a new insight into arsenic neurotoxicity. PMID:26231544

  20. Plant diversity increases soil microbial activity and soil carbon storage.

    PubMed

    Lange, Markus; Eisenhauer, Nico; Sierra, Carlos A; Bessler, Holger; Engels, Christoph; Griffiths, Robert I; Mellado-Vázquez, Perla G; Malik, Ashish A; Roy, Jacques; Scheu, Stefan; Steinbeiss, Sibylle; Thomson, Bruce C; Trumbore, Susan E; Gleixner, Gerd

    2015-01-01

    Plant diversity strongly influences ecosystem functions and services, such as soil carbon storage. However, the mechanisms underlying the positive plant diversity effects on soil carbon storage are poorly understood. We explored this relationship using long-term data from a grassland biodiversity experiment (The Jena Experiment) and radiocarbon ((14)C) modelling. Here we show that higher plant diversity increases rhizosphere carbon inputs into the microbial community resulting in both increased microbial activity and carbon storage. Increases in soil carbon were related to the enhanced accumulation of recently fixed carbon in high-diversity plots, while plant diversity had less pronounced effects on the decomposition rate of existing carbon. The present study shows that elevated carbon storage at high plant diversity is a direct function of the soil microbial community, indicating that the increase in carbon storage is mainly limited by the integration of new carbon into soil and less by the decomposition of existing soil carbon. PMID:25848862

  1. CDC-42 and RAC-1 regulate opposite chemotropisms in Neurospora crassa.

    PubMed

    Lichius, Alexander; Goryachev, Andrew B; Fricker, Mark D; Obara, Boguslaw; Castro-Longoria, Ernestina; Read, Nick D

    2014-05-01

    Cell polarization and fusion are crucial developmental processes that occur in response to intracellular and extracellular signals. Asexual spores (conidia) of the mold Neurospora crassa differentiate two types of polarized cell protrusions, germ tubes and conidial anastomosis tubes (CATs), which exhibit negative and positive chemotropism, respectively. We provide the first evidence that shared and separate functions of the Rho-type GTPases CDC-42 and RAC-1 regulate these opposite chemotropisms. We demonstrate that RAC-1 is essential for CAT formation and cell fusion, whereas CDC-42 is necessary and sufficient for normal germ tube development. Cdc42-Rac-interactive-binding (CRIB) reporters were constructed to exclusively label locally activated GTP-bound GTPases. Time course analyses showed that repositioning of these activated GTPase clusters within germ tube and CAT tip apices controls directional growth in the absence of a tip-localized vesicle supply center (Spitzenkörper). We propose a model in which the local assembly of a plasma-membrane-associated GTPase-PAK-MAPK signaling platform regulates chemoattractant perception and secretion in order to synchronize oscillatory cell-cell communication and directional CAT tip growth. PMID:24790223

  2. Deletion of Rac in Mature Osteoclasts Causes Osteopetrosis, an Age-Dependent Change in Osteoclast Number, and a Reduced Number of Osteoblasts In Vivo

    PubMed Central

    Zhu, Meiling; Sun, Ben-hua; Saar, Katarzyna; Simpson, Christine; Troiano, Nancy; Dallas, Sarah L; Tiede-Lewis, LeAnn M; Nevius, Erin; Pereira, João P; Weinstein, Robert S; Tommasini, Steven M; Insogna, Karl L

    2016-01-01

    Rac1 and Rac2 are thought to have important roles in osteoclasts. Therefore, mice with deletion of both Rac1 and Rac2 in mature osteoclasts (DKO) were generated by crossing Rac1flox/flox mice with mice expressing Cre in the cathepsin K locus and then mating these animals with Rac2−/− mice. DKO mice had markedly impaired tooth eruption. Bone mineral density (BMD) was increased 21% to 33% in 4- to 6-week-old DKO mice at all sites when measured by dual-energy X-ray absorptiometry (DXA) and serum cross-linked C-telopeptide (CTx) was reduced by 52%. The amount of metaphyseal trabecular bone was markedly increased in DKO mice, but the cortices were very thin. Spinal trabecular bone mass was increased. Histomorphometry revealed significant reductions in both osteoclast and osteoblast number and function in 4- to 6-week-old DKO animals. In 14- to 16-week-old animals, osteoclast number was increased, although bone density was further increased. DKO osteoclasts had severely impaired actin ring formation, an impaired ability to generate acid, and reduced resorptive activity in vitro. In addition, their life span ex vivo was reduced. DKO osteoblasts expressed normal differentiation markers except for the expression of osterix, which was reduced. The DKO osteoblasts mineralized normally in vitro, indicating that the in vivo defect in osteoblast function was not cell autonomous. Confocal imaging demonstrated focal disruption of the osteocytic dendritic network in DKO cortical bone. Despite these changes, DKO animals had a normal response to treatment with once-daily parathyroid hormone (PTH). We conclude that Rac1 and Rac2 have critical roles in skeletal metabolism. PMID:26496249

  3. REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...

  4. DISINFECTION OF BACTERIA ATTACHED TO GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Heterotrophic plate count bacteria, coliform organisms, and pathogenic microorganisms attached to granular activated carbon (GAC) particles were examined for their susceptibility to chlorine disinfection. When these bacteria were grown on carbon particles and then disinfected wit...

  5. REACTIONS OF CHLORITE WITH ACTIVATED CARBON AND WITH VANILLIC ACID AND INDAN ADSORBED ON ACTIVATED CARBON

    EPA Science Inventory

    The reaction between chlorite (CO2(-1)) and vanillic acid, at pH 6.0 in the presence of granular activated carbon (GAC), yielded several reaction products identifiable by GC/MS; no products were found in the absence of GAC. Indan and ClO2 or ClO2(-1) reacted in aqueous solution a...

  6. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    SciTech Connect

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2003-09-30

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be

  7. Cholecystokinin-Mediated RhoGDI Phosphorylation via PKCα Promotes both RhoA and Rac1 Signaling

    PubMed Central

    Sabbatini, Maria Eugenia; Williams, John A.

    2013-01-01

    RhoA and Rac1 have been implicated in the mechanism of CCK-induced amylase secretion from pancreatic acini. In all cell types studied to date, inactive Rho GTPases are present in the cytosol bound to the guanine nucleotide dissociation inhibitor RhoGDI. Here, we identified the switch mechanism regulating RhoGDI1-Rho GTPase dissociation and RhoA translocation upon CCK stimulation in pancreatic acini. We found that both Gα13 and PKC, independently, regulate CCK-induced RhoA translocation and that the PKC isoform involved is PKCα. Both RhoGDI1 and RhoGDI3, but not RhoGDI2, are expressed in pancreatic acini. Cytosolic RhoA and Rac1 are associated with RhoGDI1, and CCK-stimulated PKCα activation releases the complex. Overexpression of RhoGDI1, by binding RhoA, inhibits its activation, and thereby, CCK-induced apical amylase secretion. RhoA translocation is also inhibited by RhoGDI1. Inactive Rac1 influences CCK-induced RhoA activation by preventing RhoGDI1 from binding RhoA. By mutational analysis we found that CCK-induced PKCα phosphorylation on RhoGDI1 at Ser96 releases RhoA and Rac1 from RhoGDI1 to facilitate Rho GTPases signaling. PMID:23776598

  8. Metal-carbon nanocomposites based on activated IR pyrolized polyacrylonitrile

    NASA Astrophysics Data System (ADS)

    Efimov, Mikhail N.; Zhilyaeva, Natalya A.; Vasilyev, Andrey A.; Muratov, Dmitriy G.; Zemtsov, Lev M.; Karpacheva, Galina P.

    2016-05-01

    In this paper we report about new approach to preparation of metal-carbon nanocomposites based on activated carbon. Polyacrylonitrile is suggested as a precursor for Co, Pd and Ru nanoparticles carbon support which is prepared under IR pyrolysis conditions of a precursor. The first part of the paper is devoted to study activated carbon structural characteristics dependence on activation conditions. In the second part the effect of type of metal introduced in precursor on metal-carbon nanocomposite structural characteristics is shown. Prepared AC and nanocomposite samples are characterized by BET, TEM, SEM and X-ray diffraction.

  9. Merging allylic carbon-hydrogen and selective carbon-carbon bond activation

    NASA Astrophysics Data System (ADS)

    Masarwa, Ahmad; Didier, Dorian; Zabrodski, Tamar; Schinkel, Marvin; Ackermann, Lutz; Marek, Ilan

    2014-01-01

    Since the nineteenth century, many synthetic organic chemists have focused on developing new strategies to regio-, diastereo- and enantioselectively build carbon-carbon and carbon-heteroatom bonds in a predictable and efficient manner. Ideal syntheses should use the least number of synthetic steps, with few or no functional group transformations and by-products, and maximum atom efficiency. One potentially attractive method for the synthesis of molecular skeletons that are difficult to prepare would be through the selective activation of C-H and C-C bonds, instead of the conventional construction of new C-C bonds. Here we present an approach that exploits the multifold reactivity of easily accessible substrates with a single organometallic species to furnish complex molecular scaffolds through the merging of otherwise difficult transformations: allylic C-H and selective C-C bond activations. The resulting bifunctional nucleophilic species, all of which have an all-carbon quaternary stereogenic centre, can then be selectively derivatized by the addition of two different electrophiles to obtain more complex molecular architecture from these easily available starting materials.

  10. Activated Carbon Composites for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Tsouris, Costas; Burchell, Timothy D

    2011-09-01

    Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.

  11. Nodal signaling regulates endodermal cell motility and actin dynamics via Rac1 and Prex1

    PubMed Central

    Housley, Michael P.; Weiner, Orion D.

    2012-01-01

    Embryo morphogenesis is driven by dynamic cell behaviors, including migration, that are coordinated with fate specification and differentiation, but how such coordination is achieved remains poorly understood. During zebrafish gastrulation, endodermal cells sequentially exhibit first random, nonpersistent migration followed by oriented, persistent migration and finally collective migration. Using a novel transgenic line that labels the endodermal actin cytoskeleton, we found that these stage-dependent changes in migratory behavior correlated with changes in actin dynamics. The dynamic actin and random motility exhibited during early gastrulation were dependent on both Nodal and Rac1 signaling. We further identified the Rac-specific guanine nucleotide exchange factor Prex1 as a Nodal target and showed that it mediated Nodal-dependent random motility. Reducing Rac1 activity in endodermal cells caused them to bypass the random migration phase and aberrantly contribute to mesodermal tissues. Together, our results reveal a novel role for Nodal signaling in regulating actin dynamics and migration behavior, which are crucial for endodermal morphogenesis and cell fate decisions. PMID:22945937

  12. Highly porous activated carbons prepared from carbon rich Mongolian anthracite by direct NaOH activation

    NASA Astrophysics Data System (ADS)

    Byamba-Ochir, Narandalai; Shim, Wang Geun; Balathanigaimani, M. S.; Moon, Hee

    2016-08-01

    Highly porous activated carbons (ACs) were prepared from Mongolian raw anthracite (MRA) using sodium hydroxide as an activation agent by varying the mass ratio (powdered MRA/NaOH) as well as the mixing method of chemical agent and powdered MRA. The specific BET surface area and total pore volume of the prepared MRA-based activated carbons (MACs) are in the range of 816-2063 m2/g and of 0.55-1.61 cm3/g, respectively. The pore size distribution of MACs show that most of the pores are in the range from large micropores to small mesopores and their distribution can be controlled by the mass ratio and mixing method of the activating agent. As expected from the intrinsic property of the MRA, the highly graphitic surface morphology of prepared carbons was confirmed from Raman spectra and transmission electron microscopy (TEM) studies. Furthermore the FTIR and XPS results reveal that the preparation of MACs with hydrophobic in nature is highly possible by controlling the mixing conditions of activating agent and powdered MRA. Based on all the results, it is suggested that the prepared MACs could be used for many specific applications, requiring high surface area, optimal pore size distribution, proper surface hydrophobicity as well as strong physical strength.

  13. Characterization of Activated Carbons from Oil-Palm Shell by CO2 Activation with No Holding Carbonization Temperature

    PubMed Central

    Herawan, S. G.; Hadi, M. S.; Ayob, Md. R.; Putra, A.

    2013-01-01

    Activated carbons can be produced from different precursors, including coals of different ranks, and lignocellulosic materials, by physical or chemical activation processes. The objective of this paper is to characterize oil-palm shells, as a biomass byproduct from palm-oil mills which were converted into activated carbons by nitrogen pyrolysis followed by CO2 activation. The effects of no holding peak pyrolysis temperature on the physical characteristics of the activated carbons are studied. The BET surface area of the activated carbon is investigated using N2 adsorption at 77 K with selected temperatures of 500, 600, and 700°C. These pyrolysis conditions for preparing the activated carbons are found to yield higher BET surface area at a pyrolysis temperature of 700°C compared to selected commercial activated carbon. The activated carbons thus result in well-developed porosities and predominantly microporosities. By using this activation method, significant improvement can be obtained in the surface characteristics of the activated carbons. Thus this study shows that the preparation time can be shortened while better results of activated carbon can be produced. PMID:23737721

  14. Bistability in the Rac1, PAK, and RhoA Signaling Network Drives Actin Cytoskeleton Dynamics and Cell Motility Switches

    PubMed Central

    Byrne, Kate M.; Monsefi, Naser; Dawson, John C.; Degasperi, Andrea; Bukowski-Wills, Jimi-Carlo; Volinsky, Natalia; Dobrzyński, Maciej; Birtwistle, Marc R.; Tsyganov, Mikhail A.; Kiyatkin, Anatoly; Kida, Katarzyna; Finch, Andrew J.; Carragher, Neil O.; Kolch, Walter; Nguyen, Lan K.; von Kriegsheim, Alex; Kholodenko, Boris N.

    2016-01-01

    Summary Dynamic interactions between RhoA and Rac1, members of the Rho small GTPase family, play a vital role in the control of cell migration. Using predictive mathematical modeling, mass spectrometry-based quantitation of network components, and experimental validation in MDA-MB-231 mesenchymal breast cancer cells, we show that a network containing Rac1, RhoA, and PAK family kinases can produce bistable, switch-like responses to a graded PAK inhibition. Using a small chemical inhibitor of PAK, we demonstrate that cellular RhoA and Rac1 activation levels respond in a history-dependent, bistable manner to PAK inhibition. Consequently, we show that downstream signaling, actin dynamics, and cell migration also behave in a bistable fashion, displaying switches and hysteresis in response to PAK inhibition. Our results demonstrate that PAK is a critical component in the Rac1-RhoA inhibitory crosstalk that governs bistable GTPase activity, cell morphology, and cell migration switches. PMID:27136688

  15. Bistability in the Rac1, PAK, and RhoA Signaling Network Drives Actin Cytoskeleton Dynamics and Cell Motility Switches.

    PubMed

    Byrne, Kate M; Monsefi, Naser; Dawson, John C; Degasperi, Andrea; Bukowski-Wills, Jimi-Carlo; Volinsky, Natalia; Dobrzyński, Maciej; Birtwistle, Marc R; Tsyganov, Mikhail A; Kiyatkin, Anatoly; Kida, Katarzyna; Finch, Andrew J; Carragher, Neil O; Kolch, Walter; Nguyen, Lan K; von Kriegsheim, Alex; Kholodenko, Boris N

    2016-01-27

    Dynamic interactions between RhoA and Rac1, members of the Rho small GTPase family, play a vital role in the control of cell migration. Using predictive mathematical modeling, mass spectrometry-based quantitation of network components, and experimental validation in MDA-MB-231 mesenchymal breast cancer cells, we show that a network containing Rac1, RhoA, and PAK family kinases can produce bistable, switch-like responses to a graded PAK inhibition. Using a small chemical inhibitor of PAK, we demonstrate that cellular RhoA and Rac1 activation levels respond in a history-dependent, bistable manner to PAK inhibition. Consequently, we show that downstream signaling, actin dynamics, and cell migration also behave in a bistable fashion, displaying switches and hysteresis in response to PAK inhibition. Our results demonstrate that PAK is a critical component in the Rac1-RhoA inhibitory crosstalk that governs bistable GTPase activity, cell morphology, and cell migration switches. PMID:27136688

  16. Downregulation of microRNA-100 enhances the ICMT-Rac1 signaling and promotes metastasis of hepatocellular carcinoma cells.

    PubMed

    Zhou, Hui-Chao; Fang, Jian-Hong; Luo, Xu; Zhang, Lei; Yang, Jine; Zhang, Chong; Zhuang, Shi-Mei

    2014-12-15

    Metastasis is responsible for rapid recurrence of hepatocellular carcinoma (HCC) and poor survival of HCC patients. Here we showed that miR-100 downregulation in HCC tissues was significantly associated with venous invasion, advanced TNM stage, tumor nodule without complete capsule, poorer cell differentiation, and shorter recurrence-free survival. Both gain- and loss-of-function studies showed that miR-100 dramatically suppressed the ability of HCC cells to migrate and to invade through Matrigel in vitro. Analyses using mouse orthotopic xenograft model further revealed that xenografts of miR-100-stable-expressing HCC cells displayed a significant reduction in pulmonary metastasis, compared with control group. Subsequent investigations revealed that miR-100 directly inhibited the expression of isoprenylcysteine carboxyl methyltransferase (ICMT) and ras-related C3 botulinum toxin substrate 1 (Rac1) by binding to their 3'-UTRs, and in turn suppressed lamellipodia formation and matrix metallopeptidase 2 (MMP2) activation. Furthermore, knockdown of ICMT and Rac1 phenocopied the anti-metastasis effect of miR-100, whereas overexpression of the constitutively active Rac1 (Q61L) antagonized the function of miR-100. Taken together, miR-100 represses metastasis of HCC cells by abrogating the ICMT-Rac1 signaling. Downregulation of miR-100 contributes to HCC metastasis and the restoration of miR-100 is a potential strategy for cancer therapy. PMID:25361001

  17. SOD1 mutations disrupt redox-sensitive Rac regulation of NADPH oxidase in a familial ALS model

    PubMed Central

    Harraz, Maged M.; Marden, Jennifer J.; Zhou, Weihong; Zhang, Yulong; Williams, Aislinn; Sharov, Victor S.; Nelson, Kathryn; Luo, Meihui; Paulson, Henry; Schöneich, Christian; Engelhardt, John F.

    2008-01-01

    Neurodegeneration in familial amyotrophic lateral sclerosis (ALS) is associated with enhanced redox stress caused by dominant mutations in superoxide dismutase–1 (SOD1). SOD1 is a cytosolic enzyme that facilitates the conversion of superoxide (O2•–) to H2O2. Here we demonstrate that SOD1 is not just a catabolic enzyme, but can also directly regulate NADPH oxidase–dependent (Nox-dependent) O2•– production by binding Rac1 and inhibiting its GTPase activity. Oxidation of Rac1 by H2O2 uncoupled SOD1 binding in a reversible fashion, producing a self-regulating redox sensor for Nox-derived O2•– production. This process of redox-sensitive uncoupling of SOD1 from Rac1 was defective in SOD1 ALS mutants, leading to enhanced Rac1/Nox activation in transgenic mouse tissues and cell lines expressing ALS SOD1 mutants. Glial cell toxicity associated with expression of SOD1 mutants in culture was significantly attenuated by treatment with the Nox inhibitor apocynin. Treatment of ALS mice with apocynin also significantly increased their average life span. This redox sensor mechanism may explain the gain-of-function seen with certain SOD1 mutations associated with ALS and defines new therapeutic targets. PMID:18219391

  18. Construction and characterization of a mercury-independent MerR activator (MerRAC): transcriptional activation in the absence of Hg(II) is accompanied by DNA distortion.

    PubMed Central

    Parkhill, J; Ansari, A Z; Wright, J G; Brown, N L; O'Halloran, T V

    1993-01-01

    The MeR regulatory protein of transposon Tn501 controls the expression of the mercury resistance (mer) genes in response to the concentration of mercuric ions. MerR is unique among prokaryotic regulatory proteins so far described in that it acts as a repressor [-Hg(II)] and an activator [+Hg(II)] of transcription of the mer genes, but binds to a single site on the DNA in both cases. This transcriptional activation process has been postulated to involve a protein-induced conformational change in the DNA that allows RNA polymerase more readily to form an open complex at the promoter. It has been shown [Frantz and O'Halloran (1990) Biochemistry, 29, 4747-4751] that activation of transcription by MerR in the presence of mercury is accompanied by hypersensitivity of the operator to chemical nucleases that are sensitive to local distortion in DNA structure. Here we describe specific mutations in MerR that allow the protein to stimulate transcription in the absence of the allosteric activator Hg(II). We demonstrate that the degree of activation caused by these mutants directly correlates with the degree of DNA distortion as measured by the hypersensitivity of MerR-DNA complexes to the nuclease Cu-5-phenyl-o-phenanthroline. These results support the model described above. Images PMID:8440234

  19. Activated carbons from North Dakota lignite and leonardite

    SciTech Connect

    Young, B.C.; Olson, E.S.; Knudson, C.L.; Timpe, R.C.

    1995-12-31

    The EERC is undertaking a research and development program on carbon development, part of which is directed towards investigating the key parameters in the preparation of activated carbons from low-rank coals indigenous to North Dakota. Carbons have been prepared and characterized for potential sorption applications in flue gas and waste liquid streams. Lignite, owing to its wide occurrence and variability in properties, has received significant attention as a precursor of active carbon manufacture. Mineral matter content and its alkaline nature are two highly variable properties that can have important consequences on the production of suitable activated carbons. Other factors affecting the production include carbonizing conditions, the activation agents, activation temperature, and activation time. However, as previously noted, the relationship between the above factors and the sorption activity is particularly complex. Part of the difficulty is that sorption activity encompasses at least three parameters, namely, surface area, pore distribution, and surface acidity/basicity. The presence of mineral matter in the coal can affect not only carbonization but also the activation and subsequent sorption and desorption processes. This paper presents results of an investigation of demineralization, carbonization temperature, activation temperature, and activation time for one lignite and leonardite from North Dakota.

  20. Phenol adsorption by activated carbon produced from spent coffee grounds.

    PubMed

    Castro, Cínthia S; Abreu, Anelise L; Silva, Carmen L T; Guerreiro, Mário C

    2011-01-01

    The present work highlights the preparation of activated carbons (ACs) using spent coffee grounds, an agricultural residue, as carbon precursor and two different activating agents: water vapor (ACW) and K(2)CO(3) (ACK). These ACs presented the microporous nature and high surface area (620-950 m(2) g(-1)). The carbons, as well as a commercial activated carbon (CAC) used as reference, were evaluated as phenol adsorbent showing high adsorption capacity (≈150 mg g(-1)). The investigation of the pH solution in the phenol adsorption was also performed. The different activating agents led to AC with distinct morphological properties, surface area and chemical composition, although similar phenol adsorption capacity was verified for both prepared carbons. The production of activated carbons from spent coffee grounds resulted in promising adsorbents for phenol removal while giving a noble destination to the residue. PMID:22105129

  1. Histamine acting on H1 receptor promotes inhibition of proliferation via PLC, RAC, and JNK-dependent pathways

    SciTech Connect

    Notcovich, Cintia; Diez, Federico; Tubio, Maria Rosario; Baldi, Alberto; Kazanietz, Marcelo G.; Davio, Carlos; Shayo, Carina

    2010-02-01

    It is well established that histamine modulates cell proliferation through the activation of the histamine H1 receptor (H1R), a G protein-coupled receptor (GPCR) that is known to couple to phospholipase C (PLC) activation via Gq. In the present study, we aimed to determine whether H1R activation modulates Rho GTPases, well-known effectors of Gq/G{sub 11}-coupled receptors, and whether such modulation influences cell proliferation. Experiments were carried out in CHO cells stably expressing H1R (CHO-H1R). By using pull-down assays, we found that both histamine and a selective H1R agonist activated Rac and RhoA in a time- and dose-dependent manner without significant changes in the activation of Cdc42. Histamine response was abolished by the H1R antagonist mepyramine, RGS2 and the PLC inhibitor U73122, suggesting that Rac and RhoA activation is mediated by H1R via Gq coupling to PLC stimulation. Histamine caused a marked activation of serum response factor activity via the H1R, as determined with a serum-responsive element (SRE) luciferase reporter, and this response was inhibited by RhoA inactivation with C3 toxin. Histamine also caused a significant activation of JNK which was inhibited by expression of the Rac-GAP {beta}2-chimaerin. On the other hand, H1R-induced ERK1/2 activation was inhibited by U73122 but not affected by C3 or {beta}2-chimaerin, suggesting that ERK1/2 activation was dependent on PLC and independent of RhoA or Rac. [{sup 3}H]-Thymidine incorporation assays showed that both histamine and the H1R agonist inhibited cell proliferation in a dose-dependent manner and that the effect was independent of RhoA but partially dependent on JNK and Rac. Our results reveal that functional coupling of the H1R to Gq-PLC leads to the activation of RhoA and Rac small GTPases and suggest distinct roles for Rho GTPases in the control of cell proliferation by histamine.

  2. Lck/PLCγ control migration and proliferation of interleukin (IL)-2-stimulated T cells via the Rac1 GTPase/glycogen phosphorylase pathway.

    PubMed

    Llavero, Francisco; Artaso, Alain; Lacerda, Hadriano M; Parada, Luis A; Zugaza, José L

    2016-11-01

    Recently, we have reported that the IL-2-stimulated T cells activate PKCθ in order to phosphorylate the serine residues of αPIX-RhoGEF, and to switch on the Rac1/PYGM pathway resulting in T cell migration and proliferation. However, the molecular mechanism connecting the activated IL-2-R with the PKCθ/αPIX/Rac1/PYGM pathway is still unknown. In this study, the use of a combined pharmacological and genetic approach identified Lck, a Src family member, as the tyrosine kinase phosphorylating PLCγ leading to Rac1 and PYGM activation in the IL-2-stimulated Kit 225 T cells via the PKCθ/αPIX pathway. The PLCγ tyrosine phosphorylation was required to activate first PKCθ, and then αPIX and Rac1/PYGM. The results presented here delineate a novel signalling pathway ranking equally in importance to the three major pathways controlled by the IL-2-R, i.e. PI3K, Ras/MAPK and JAK/STAT pathways. The overall evidence strongly indicates that the central biological role of the novel IL-2-R/Lck/PLCγ/PKCθ/αPIX/Rac1/PYGM signalling pathway is directly related to the control of fundamental cellular processes such as T cell migration and proliferation. PMID:27519475

  3. Epidermal growth factor attenuates blood-spinal cord barrier disruption via PI3K/Akt/Rac1 pathway after acute spinal cord injury.

    PubMed

    Zheng, Binbin; Ye, Libing; Zhou, Yulong; Zhu, Sipin; Wang, Qingqing; Shi, Hongxue; Chen, Daqing; Wei, Xiaojie; Wang, Zhouguang; Li, Xiaokun; Xiao, Jian; Xu, Huazi; Zhang, Hongyu

    2016-06-01

    After spinal cord injury (SCI), disruption of blood-spinal cord barrier (BSCB) elicits blood cell infiltration such as neutrophils and macrophages, contributing to permanent neurological disability. Previous studies show that epidermal growth factor (EGF) produces potent neuroprotective effects in SCI models. However, little is known that whether EGF contributes to the integrity of BSCB. The present study is performed to explore the mechanism of BSCB permeability changes which are induced by EGF treatment after SCI in rats. In this study, we demonstrate that EGF administration inhibits the disruption of BSCB permeability and improves the locomotor activity in SCI model rats. Inhibition of the PI3K/Akt pathways by a specific inhibitor, LY294002, suppresses EGF-induced Rac1 activation as well as tight junction (TJ) and adherens junction (AJ) expression. Furthermore, the protective effect of EGF on BSCB is related to the activation of Rac1 both in vivo and in vitro. Blockade of Rac1 activation with Rac1 siRNA downregulates EGF-induced TJ and AJ proteins expression in endothelial cells. Taken together, our results indicate that EGF treatment preserves BSCB integrity and improves functional recovery after SCI via PI3K-Akt-Rac1 signalling pathway. PMID:26769343

  4. Rac1-mediated indentation of resting neurons promotes the chain migration of new neurons in the rostral migratory stream of post-natal mouse brain.

    PubMed

    Hikita, Takao; Ohno, Akihisa; Sawada, Masato; Ota, Haruko; Sawamoto, Kazunobu

    2014-03-01

    New neurons generated in the ventricular-subventricular zone in the post-natal brain travel toward the olfactory bulb by using a collective cell migration process called 'chain migration.' These new neurons show a saltatory movement of their soma, suggesting that each neuron cycles through periods of 'rest' during migration. Here, we investigated the role of the resting neurons in chain migration using post-natal mouse brain, and found that they undergo a dynamic morphological change, in which a deep indentation forms in the cell body. Inhibition of Rac1 activity resulted in less indentation of the new neurons in vivo. Live cell imaging using a Förster resonance energy transfer biosensor revealed that Rac1 was activated at the sites of contact between actively migrating and resting new neurons. On the cell surface of resting neurons, Rac1 activation coincided with the formation of the indentation. Furthermore, Rac1 knockdown prevented the indentation from forming and impaired migration along the resting neurons. These results suggest that Rac1 regulates a morphological change in the resting neurons, which allows them to serve as a migratory scaffold, and thereby non-cell-autonomously promotes chain migration. PMID:24188721

  5. Shear stress–induced endothelial cell polarization is mediated by Rho and Rac but not Cdc42 or PI 3-kinases

    PubMed Central

    Wojciak-Stothard, Beata; Ridley, Anne J.

    2003-01-01

    Shear stress induces endothelial polarization and migration in the direction of flow accompanied by extensive remodeling of the actin cytoskeleton. The GTPases RhoA, Rac1, and Cdc42 are known to regulate cell shape changes through effects on the cytoskeleton and cell adhesion. We show here that all three GTPases become rapidly activated by shear stress, and that each is important for different aspects of the endothelial response. RhoA was activated within 5 min after stimulation with shear stress and led to cell rounding via Rho-kinase. Subsequently, the cells respread and elongated within the direction of shear stress as RhoA activity returned to baseline and Rac1 and Cdc42 reached peak activation. Cell elongation required Rac1 and Cdc42 but not phosphatidylinositide 3-kinases. Cdc42 and PI3Ks were not required to establish shear stress–induced polarity although they contributed to optimal migration speed. Instead, Rho and Rac1 regulated directionality of cell movement. Inhibition of Rho or Rho-kinase did not affect the cell speed but significantly increased cell displacement. Our results show that endothelial cells reorient in response to shear stress by a two-step process involving Rho-induced depolarization, followed by Rho/Rac-mediated polarization and migration in the direction of flow. PMID:12719476

  6. Synthesis of fluorescent carbon nanoparticles directly from active carbon via a one-step ultrasonic treatment

    SciTech Connect

    Li, Haitao; He, Xiaodie; Liu, Yang; Yu, Hang; Kang, Zhenhui; Lee, Shuit-Tong

    2011-01-15

    Water-soluble fluorescent carbon nanoparticles were synthesized directly from active carbon by a one-step hydrogen peroxide-assisted ultrasonic treatment. The carbon nanoparticles were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometer. The results showed that the surface of carbon nanoparticles was rich of hydroxyl groups resulting in high hydrophilicity. The carbon nanoparticles could emit bright and colorful photoluminescence covering the entire visible-to-near infrared spectral range. Furthermore, these carbon nanoparticles also had excellent up-conversion fluorescent properties.

  7. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  8. Interaction forces between waterborne bacteria and activated carbon particles.

    PubMed

    Busscher, Henk J; Dijkstra, Rene J B; Langworthy, Don E; Collias, Dimitris I; Bjorkquist, David W; Mitchell, Michael D; Van der Mei, Henny C

    2008-06-01

    Activated carbons remove waterborne bacteria from potable water systems through attractive Lifshitz-van der Waals forces despite electrostatic repulsion between negatively charged cells and carbon surfaces. In this paper we quantify the interaction forces between bacteria with negatively and positively charged, mesoporous wood-based carbons, as well as with a microporous coconut carbon. To this end, we glued carbon particles to the cantilever of an atomic force microscope and measured the interaction forces upon approach and retraction of thus made tips. Waterborne Raoultella terrigena and Escherichia coli adhered weakly (1-2 nN) to different activated carbon particles, and the main difference between the activated carbons was the percentage of curves with attractive sites revealed upon traversing of a carbon particle through the bacterial EPS layer. The percentage of curves showing adhesion forces upon retraction varied between 21% and 69%, and was highest for R. terrigena with positively charged carbon (66%) and a coconut carbon (69%). Macroscopic bacterial removal by the mesoporous carbon particles increased with increasing percentages of attractive sites revealed upon traversing a carbon particle through the outer bacterial surface layer. PMID:18405910

  9. JPL Activated Carbon Treatment System (ACTS) for sewage

    NASA Technical Reports Server (NTRS)

    1976-01-01

    An Activated Carbon Treatment System (ACTS) was developed for sewage treatment and is being applied to a one-million gallon per day sewage treatment pilot plant in Orange County California. Activities reported include pyrolysis and activation of carbon-sewage sludge, and activated carbon treatment of sewage to meet ocean discharge standards. The ACTS Sewage treatment operations include carbon-sewage treatment, primary and secondary clarifiers, gravity (multi-media) filter, filter press dewatering, flash drying of carbon-sewage filter cake, and sludge pyrolysis and activation. Tests were conducted on a laboratory scale, 10,000 gallon per day demonstration plant and pilot test equipment. Preliminary economic studies are favorable to the ACTS process relative to activated sludge treatment for a 175,000,000 gallon per day sewage treatment plant.

  10. Activated Carbon Modified with Copper for Adsorption of Propanethiol

    PubMed Central

    Moreno-Piraján, Juan Carlos; Tirano, Joaquín; Salamanca, Brisa; Giraldo, Liliana

    2010-01-01

    Activated carbons were characterized texturally and chemically before and after treatment, using surface area determination in the BET model, Boehm titration, TPR, DRX and immersion calorimetry. The adsorption capacity and the kinetics of sulphur compound removal were determined by gas chromatography. It was established that the propanethiol retention capacity is dependent on the number of oxygenated groups generated on the activated carbon surface and that activated carbon modified with CuO at 0.25 M shows the highest retention of propanethiol. Additionally is proposed a mechanism of decomposition of propenothiol with carbon-copper system. PMID:20479992

  11. MST3 promotes proliferation and tumorigenicity through the VAV2/Rac1 signal axis in breast cancer

    PubMed Central

    Cho, Chien-Yu; Lee, Kuo-Ting; Chen, Wei-Ching; Wang, Chih-Yang; Chang, Yung-Sheng; Huang, Hau-Lun; Hsu, Hui-Ping; Yen, Meng-Chi; Lai, Ming-Zong; Lai, Ming-Derg

    2016-01-01

    MST3 (mammalian STE20-like kinase 3) belongs to the Ste20 serine/threonine protein kinase family. The role of MST3 in tumor growth is less studied; therefore, we investigates the function of MST3 in breast cancer. Here, we demonstrate that MST3 is overexpressed in human breast tumors. Online Kaplan-Meier plotter analysis reveals that overexpression of MST3 predicts poor prognosis in breast cancer patients. Knockdown of MST3 with shRNA inhibits proliferation and anchorage-independent growth in vitro. Downregulation of MST3 in triple-negative MDA-MB-231 and MDA-MB-468 breast cancer cells decreases tumor formation in NOD/SCID mice. MST3 interacts with VAV2, but not VAV3, as demonstrated by co-immunoprecipitation and confocal microscopy. By domain mapping of MST3, we determine that the proline-rich region of MST3 (353KDIPKRP359) interacts with the SH3 domain of VAV2. Mutation of the two proline residues in this domain significantly attenuates the interaction between MST3 and VAV2. Overexpression of wild-type MST3 (WT-MST3), but not proline-rich-deleted MST3 (ΔP-MST3), enhances the proliferation rate and anchorage-independent growth of MDA-MB-468 cells. Overexpression of MST3 increases VAV2 phosphorylation and GTP-Rac1, whereas downregulation of MST3 or delivery of ΔP-MST3 results in a reduction of VAV2 and Rac1 activation. Knockdown of MST3 inhibits cyclin D1 protein expression. The Rac1 inhibitor EHop-016 attenuates cell proliferation induced by WT-MST3. Finally, Knockdown of MST3 or Rac1 inhibitor decreases cyclin D protein expression, which is important for tumor growth. These results indicate that MST3 interacts with VAV2 to activate Rac1 and promote the tumorigenicity of breast cancer. PMID:26910843

  12. Acoustical Evaluation of Carbonized and Activated Cotton Nonwovens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The process of manufacturing a carbonized and activated nonwoven made by cotton fiber was investigated in this paper. The study was focused on the acoustic application and nonwoven composites with cotton nonwoven as a base layer and glass fiber nonwoven, cotton nonwoven, and carbonized and activated...

  13. Preparation of nitrogen-enriched activated carbons from brown coal

    SciTech Connect

    Robert Pietrzak; Helena Wachowska; Piotr Nowicki

    2006-05-15

    Nitrogen-enriched activated carbons were prepared from a Polish brown coal. Nitrogen was introduced from urea at 350{sup o}C in an oxidizing atmosphere both to carbonizates obtained at 500-700{sup o}C and to activated carbons prepared from them. The activation was performed at 800{sup o}C with KOH in argon. It has been observed that the carbonization temperature determines the amount of nitrogen that is incorporated (DC5U, 8.4 wt % N{sup daf}; DC6U, 6.3 wt % N{sup daf}; and DC7U, 5.4 wt % N{sup daf}). X-ray photoelectron spectroscopy (XPS) measurements have shown that nitrogen introduced both at the stage of carbonizates and at the stage of activated carbons occurs mainly as -6, -5, and imine, amine and amide groups. On the other hand, the activation of carbons enriched with nitrogen results in the formation of pyridonic nitrogen and N-Q. The introduction of nitrogen at the activated carbon stage leads to a slight decrease in surface area. It has been proven that the most effective way of preparing microporous activated carbons enriched with nitrogen to a considerable extent and having high surface area ({approximately} 3000 m{sup 2}/g) is the following: carbonization - activation - reaction with urea. 40 refs., 1 fig., 6 tabs.

  14. Lanthanum complexes containing a bis(phenolate) ligand with a ferrocene-1,1'-diyldithio backbone: synthesis, characterization, and ring-opening polymerization of rac-lactide.

    PubMed

    Hermans, Catherine; Rong, Weifeng; Spaniol, Thomas P; Okuda, Jun

    2016-05-10

    Lanthanum complexes [(L)LaX] (X = N(SiMe3)2, O(i)Pr , BH4) supported by a ferrocene-based (OSSO)-type ligand LH2 were synthesized and characterized by elemental analysis, NMR spectroscopy and cyclic voltammetry. The structure of was confirmed by single crystal X-ray diffraction. These complexes were highly active initiators for the ring-opening polymerization of rac-lactide (rac-LA). The activity depended on the initiating group in the order of ≈ > . The activities of and during polymerization were controlled in situ with external redox reagents by reversibly switching the oxidation state of the iron center. PMID:27088967

  15. p35 and Rac1 underlie the neuroprotection and cognitive improvement induced by CDK5 silencing

    PubMed Central

    Posada-Duque, Rafael Andres; López-Tobón, Alejandro; Piedrahita, Diego; González-Billault, Christian; Cardona-Gomez, Gloria Patricia

    2015-01-01

    CDK5 plays an important role in neurotransmission and synaptic plasticity in the normal function of the adult brain, and dysregulation can lead to Tau hyperphosphorylation and cognitive impairment. In a previous study, we demonstrated that RNAi knock down of CDK5 reduced the formation of neurofibrillary tangles and prevented neuronal loss in triple transgenic Alzheimer’s mice. Here, we report that CDK5 RNAi protected against glutamate-mediated excitotoxicity using primary hippocampal neurons transduced with AAV2.5 viral vector eGFP-tagged SCR or CDK5 shRNA-miR during 12 days. Protection was dependent on a concomitant increase in p35 and was reversed using p35 RNAi, which affected the down-stream Rho GTPase activity. Furthermore, p35 overexpression and constitutively active Rac1 mimicked CDK5 silencing-induced neuroprotection. In addition, 3xTg-AD mice (24 months old) were injected in the hippocampus with SCR or CDK5 shRNA-miR, and spatial learning and memory were performed three weeks post injection using “Morris” water maze test. Our data showed that CDK5 knock down induced an increase in p35 protein levels and Rac activity in triple transgenic Alzheimer’s mice, which correlated with the recovery of cognitive function; these findings confirm that increased p35 and active Rac are involved in neuroprotection. In summary, our data suggest that p35 acts as a mediator of Rho GTPase activity and contributes to the neuroprotection induced by CDK5 RNAi. PMID:25864429

  16. p35 and Rac1 underlie the neuroprotection and cognitive improvement induced by CDK5 silencing.

    PubMed

    Posada-Duque, Rafael Andres; López-Tobón, Alejandro; Piedrahita, Diego; González-Billault, Christian; Cardona-Gomez, Gloria Patricia

    2015-07-01

    CDK5 plays an important role in neurotransmission and synaptic plasticity in the normal function of the adult brain, and dysregulation can lead to Tau hyperphosphorylation and cognitive impairment. In a previous study, we demonstrated that RNAi knock down of CDK5 reduced the formation of neurofibrillary tangles (NFT) and prevented neuronal loss in triple transgenic Alzheimer's mice. Here, we report that CDK5 RNAi protected against glutamate-mediated excitotoxicity using primary hippocampal neurons transduced with adeno-associated virus 2.5 viral vector eGFP-tagged scrambled or CDK5 shRNA-miR during 12 days. Protection was dependent on a concomitant increase in p35 and was reversed using p35 RNAi, which affected the down-stream Rho GTPase activity. Furthermore, p35 over-expression and constitutively active Rac1 mimicked CDK5 silencing-induced neuroprotection. In addition, 3xTg-Alzheimer's disease mice (24 months old) were injected in the hippocampus with scrambled or CDK5 shRNA-miR, and spatial learning and memory were performed 3 weeks post-injection using 'Morris' water maze test. Our data showed that CDK5 knock down induced an increase in p35 protein levels and Rac activity in triple transgenic Alzheimer's mice, which correlated with the recovery of cognitive function; these findings confirm that increased p35 and active Rac are involved in neuroprotection. In summary, our data suggest that p35 acts as a mediator of Rho GTPase activity and contributes to the neuroprotection induced by CDK5 RNAi. PMID:25864429

  17. A Magnesium-Activated Carbon Hybrid Capacitor

    SciTech Connect

    Yoo, HD; Shterenberg, I; Gofer, Y; Doe, RE; Fischer, CC; Ceder, G; Aurbach, D

    2013-12-11

    Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionic complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.

  18. Ozone Removal by Filters Containing Activated Carbon: A Pilot Study

    SciTech Connect

    Fisk, William; Spears, Mike; Sullivan, Douglas; Mendell, Mark

    2009-09-01

    This study evaluated the ozone removal performance of moderate-cost particle filters containing activated carbon when installed in a commercial building heating, ventilating, and air conditioning (HVAC) system. Filters containing 300 g of activated carbon per 0.09 m2 of filter face area were installed in two 'experimental' filter banks within an office building located in Sacramento, CA. The ozone removal performance of the filters was assessed through periodic measurements of ozone concentrations in the air upstream and downstream of the filters. Ozone concentrations were also measured upstream and downstream of a 'reference' filter bank containing filters without any activated carbon. The filter banks with prefilters containing activated carbon were removing 60percent to 70percent of the ozone 67 and 81 days after filter installation. In contrast, there was negligible ozone removal by the reference filter bank without activated carbon.

  19. Selecting activated carbon for water and wastewater treatability studies

    SciTech Connect

    Zhang, W.; Chang, Q.G.; Liu, W.D.; Li, B.J.; Jiang, W.X.; Fu, L.J.; Ying, W.C.

    2007-10-15

    A series of follow-up investigations were performed to produce data for improving the four-indicator carbon selection method that we developed to identify high-potential activated carbons effective for removing specific organic water pollutants. The carbon's pore structure and surface chemistry are dependent on the raw material and the activation process. Coconut carbons have relatively more small pores than large pores; coal and apricot nutshell/walnut shell fruit carbons have the desirable pore structures for removing adsorbates of all sizes. Chemical activation, excessive activation, and/or thermal reactivation enlarge small pores, resulting in reduced phenol number and higher tannic acid number. Activated carbon's phenol, iodine, methylene blue, and tannic acid numbers are convenient indicators of its surface area and pore volume of pore diameters < 10, 10-15, 15-28, and > 28 angstrom, respectively. The phenol number of a carbon is also a good indicator of its surface acidity of oxygen-containing organic functional groups that affect the adsorptive capacity for aromatic and other small polar organics. The tannic acid number is an indicator of carbon's capacity for large, high-molecular-weight natural organic precursors of disinfection by-products in water treatment. The experimental results for removing nitrobenzene, methyl-tert-butyl ether, 4,4-bisphenol, humic acid, and the organic constituents of a biologically treated coking-plant effluent have demonstrated the effectiveness of this capacity-indicator-based method of carbon selection.

  20. Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl 2 activation

    NASA Astrophysics Data System (ADS)

    Uçar, Suat; Erdem, Murat; Tay, Turgay; Karagöz, Selhan

    2009-08-01

    In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl 2. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m 2 g -1. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m 2 g -1 and 0.329 cm 3 g -1. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature.

  1. Studies relevant to the catalytic activation of carbon monoxide

    SciTech Connect

    Ford, P.C.

    1992-06-04

    Research activity during the 1991--1992 funding period has been concerned with the following topics relevant to carbon monoxide activation. (1) Exploratory studies of water gas shift catalysts heterogenized on polystyrene based polymers. (2) Mechanistic investigation of the nucleophilic activation of CO in metal carbonyl clusters. (3) Application of fast reaction techniques to prepare and to investigate reactive organometallic intermediates relevant to the activation of hydrocarbons toward carbonylation and to the formation of carbon-carbon bonds via the migratory insertion of CO into metal alkyl bonds.

  2. Impact of Sulfur Oxides on Mercury Capture by Activated Carbon

    SciTech Connect

    Presto, A.A.; Granite, E.J.

    2007-09-15

    Recent field tests of mercury removal with activated carbon injection (ACI) have revealed that mercury capture is limited in flue gases containing high concentrations of sulfur oxides (SOx). In order to gain a more complete understanding of the impact of SOx on ACI, mercury capture was tested under varying conditions of SO2 and SO3 concentrations using a packed bed reactor and simulated flue gas (SFG). The final mercury content of the activated carbons is independent of the SO2 concentration in the SFG, but the presence of SO3 inhibits mercury capture even at the lowest concentration tested (20 ppm). The mercury removal capacity decreases as the sulfur content of the used activated carbons increases from 1 to 10%. In one extreme case, an activated carbon with 10% sulfur, prepared by H2SO4 impregnation, shows almost no mercury capacity. The results suggest that mercury and sulfur oxides are in competition for the same binding sites on the carbon surface.

  3. Ofloxacin induces apoptosis via β1 integrin-EGFR-Rac1-Nox2 pathway in microencapsulated chondrocytes

    SciTech Connect

    Sheng, Zhi-Guo; Huang, Wei; Liu, Yu-Xiang; Yuan, Ye; Zhu, Ben-Zhan

    2013-02-15

    Quinolones (QNs)-induced arthropathy is an important toxic side-effect in immature animals leading to the restriction of their therapeutic use in pediatrics. Ofloxacin, a typical QN, was found to induce the chondrocytes apoptosis in the early phase (12–48 h) of arthropathy in our previous study. However, the exact mechanism(s) is unclear. Microencapsulated juvenile rabbit joint chondrocytes, a three-dimensional culture system, is utilized to perform the present study. Ofloxacin, at a therapeutically relevant concentration (10 μg/ml), disturbs the interaction between β1 integrin and activated intracellular signaling proteins at 12 h, which is inhibited when supplementing Mg{sup 2+}. Intracellular reactive oxygen species (ROS) significantly increases in a time-dependent manner after exposure to ofloxacin for 12–48 h. Furthermore, ofloxacin markedly enhances the level of activated Rac1 and epidermal growth factor receptor (EGFR) phosphorylation, and its inhibition in turn reduces the ROS production, apoptosis and Rac1 activation. Silencing Nox2, Rac1 or supplementing Mg{sup 2+} inhibits ROS accumulation, apoptosis occurrence and EGFR phosphorylation induced by ofloxacin. However, depletion of Nox2, Rac1 and inhibition of EGFR do not affect ofloxacin-mediated loss of interaction between β1 integrin and activated intracellular signaling proteins. In addition, ofloxacin also induces Vav2 phosphorylation, which is markedly suppressed after inactivating EGFR or supplementing Mg{sup 2+}. These results suggest that ofloxacin causes Nox2-mediated intracellular ROS production by disrupting the β1 integrin function and then activating the EGFR-Vav2-Rac1 pathway, finally resulting in apoptosis within 12–48 h exposure. The present study provides a novel insight regarding the potential role of Nox-driven ROS in QNs-induced arthropathy. - Highlights: ► Ofloxacin induces Nox2-driven ROS in encapsulated chondrocyte at 12–48 h. ► Ofloxacin stimulates ROS production via

  4. Cellulosic carbon fibers with branching carbon nanotubes for enhanced electrochemical activities for bioprocessing applications.

    PubMed

    Zhao, Xueyan; Lu, Xin; Tze, William Tai Yin; Kim, Jungbae; Wang, Ping

    2013-09-25

    Renewable biobased carbon fibers are promising materials for large-scale electrochemical applications including chemical processing, energy storage, and biofuel cells. Their performance is, however, often limited by low activity. Herein we report that branching carbon nanotubes can enhance the activity of carbonized cellulosic fibers, such that the oxidation potential of NAD(H) was reduced to 0.55 V from 0.9 V when applied for bioprocessing. Coordinating with enzyme catalysts, such hierarchical carbon materials effectively facilitated the biotransformation of glycerol, with the total turnover number of NAD(H) over 3500 within 5 h of reaction. PMID:24020801

  5. Hydrogen adsorption on functionalized nanoporous activated carbons.

    PubMed

    Zhao, X B; Xiao, B; Fletcher, A J; Thomas, K M

    2005-05-12

    There is considerable interest in hydrogen adsorption on carbon nanotubes and porous carbons as a method of storage for transport and related energy applications. This investigation has involved a systematic investigation of the role of functional groups and porous structure characteristics in determining the hydrogen adsorption characteristics of porous carbons. Suites of carbons were prepared with a wide range of nitrogen and oxygen contents and types of functional groups to investigate their effect on hydrogen adsorption. The porous structures of the carbons were characterized by nitrogen (77 K) and carbon dioxide (273 K) adsorption methods. Hydrogen adsorption isotherms were studied at 77 K and pressure up to 100 kPa. All the isotherms were Type I in the IUPAC classification scheme. Hydrogen isobars indicated that the adsorption of hydrogen is very temperature dependent with little or no hydrogen adsorption above 195 K. The isosteric enthalpies of adsorption at zero surface coverage were obtained using a virial equation, while the values at various surface coverages were obtained from the van't Hoff isochore. The values were in the range 3.9-5.2 kJ mol(-1) for the carbons studied. The thermodynamics of the adsorption process are discussed in relation to temperature limitations for hydrogen storage applications. The maximum amounts of hydrogen adsorbed correlated with the micropore volume obtained from extrapolation of the Dubinin-Radushkevich equation for carbon dioxide adsorption. Functional groups have a small detrimental effect on hydrogen adsorption, and this is related to decreased adsorbate-adsorbent and increased adsorbate-adsorbate interactions. PMID:16852056

  6. Role of nitrogen in pore development in activated carbon prepared by potassium carbonate activation of lignin

    NASA Astrophysics Data System (ADS)

    Tsubouchi, Naoto; Nishio, Megumi; Mochizuki, Yuuki

    2016-05-01

    The present work focuses on the role of nitrogen in the development of pores in activated carbon produced from lignin by K2CO3 activation, employing a fixed bed reactor under a high-purity He stream at temperatures of 500-900 °C. The specific surface area and pore volume obtained by activation of lignin alone are 230 m2/g and 0.13 cm3/g at 800 °C, and 540 m2/g and 0.31 cm3/g at 900 °C, respectively. Activation of a mixture of lignin and urea provides a significant increase in the surface area and volume, respectively reaching 3300-3400 m2/g and 2.0-2.3 cm3/g after holding at 800-900 °C for 1 h. Heating a lignin/urea/K2CO3 mixture leads to a significant decrease in the yield of released N-containing gases compared to the results for urea alone and a lignin/urea mixture, and most of the nitrogen in the urea is retained in the solid phase. X-ray photoelectron spectroscopy and X-ray diffraction analyses clearly show that part of the remaining nitrogen is present in heterocyclic structures (for example, pyridinic and pyrrolic nitrogen), and the rest is contained as KOCN at ≤600 °C and as KCN at ≥700 °C, such that the latter two compounds can be almost completely removed by water washing. The fate of nitrogen during heating of lignin/urea/K2CO3 and role of nitrogen in pore development in activated carbon are discussed on the basis of the results mentioned above.

  7. Reprocessing of used tires into activated carbon and other products

    SciTech Connect

    Teng, H.; Serio, M.A.; Wojtowicz, M.A.; Bassilakis, R.; Solomon, P.R.

    1995-09-01

    Landfilling used tires which are generated each year in the US is increasingly becoming an unacceptable solution. A better approach, from an environmental and economic standpoint, is to thermally reprocess the tires into valuable products such as activated carbon, other solid carbon forms (carbon black, graphite, and carbon fibers), and liquid fuels. In this study, high surface area activated carbons (> 800 m{sup 2}/g solid product) were produced in relatively high yields by pyrolysis of tires at up to 900 C, followed by activation in CO{sub 2} at the same temperature. The surface areas of these materials are comparable with those of commercial activated carbons. The efficiency of the activation process (gain in specific surface area/loss in mass) was greatest (up to 138 m{sup 2}/g original tire) when large pieces of tire material were used ({approximately} 170 mg). Oxygen pretreatment of tires was found to enhance both the yield and the surface area of the carbon product. High-pressure treatment of tires at low temperatures (< 400 C) is an alternative approach if the recovery of carbon black or fuel oils is the primary objective.

  8. 76 FR 51344 - Butte County Resource Advisory Committee (RAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-18

    ...The Butte County Resource Advisory Committee (RAC) will hold a meeting on August 29, 2011 in Oroville, CA. The purpose of the meeting is to review Cycle 2 project applications for potential funding recommendations to Lassen, Plumas or Mendocino National Forest Supervisors. The funding is made available under Title II provisions of the Secure Rural Schools and Community Self-Determination Act......

  9. Liquid-phase adsorption of organic compounds by granular activated carbon and activated carbon fibers

    SciTech Connect

    Lin, S.H.; Hsu, F.M.

    1995-06-01

    Liquid-phase adsorption of organic compounds by granular activated carbon (GAC) and activated carbon fibers (ACFs) is investigated. Acetone, isopropyl alcohol (IPA), phenol, and tetrahydrofuran (THF) were employed as the model compounds for the present study. It is observed from the experimental results that adsorption of organic compounds by GAC and ACF is influenced by the BET (Brunauer-Emmett-Teller) surface area of adsorbent and the molecular weight, polarity, and solubility of the adsorbate. The adsorption characteristics of GAC and ACFs were found to differ rather significantly. In terms of the adsorption capacity of organic compounds, the time to reach equilibrium adsorption, and the time for complete desorption, ACFs have been observed to be considerably better than GAC. For the organic compounds tested here, the GAC adsorptions were shown to be represented well by the Langmuir isotherm while the ACF adsorption could be adequately described by the Langmuir or the Freundlich isotherm. Column adsorption tests indicated that the exhausted ACFs can be effectively regenerated by static in situ thermal desorption at 150 C, but the same regeneration conditions do not do as well for the exhausted GAC.

  10. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation.

    PubMed

    Wei, Mingyu; Gao, Long; Li, Jun; Fang, Jia; Cai, Wenxuan; Li, Xiaoxia; Xu, Aihua

    2016-10-01

    Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants. PMID:27214000

  11. Physicochemical and porosity characteristics of thermally regenerated activated carbon polluted with biological activated carbon process.

    PubMed

    Dong, Lihua; Liu, Wenjun; Jiang, Renfu; Wang, Zhansheng

    2014-11-01

    The characteristics of thermally regenerated activated carbon (AC) polluted with biological activated carbon (BAC) process were investigated. The results showed that the true micropore and sub-micropore volume, pH value, bulk density, and hardness of regenerated AC decreased compared to the virgin AC, but the total pore volume increased. XPS analysis displayed that the ash contents of Al, Si, and Ca in the regenerated AC respectively increased by 3.83%, 2.62% and 1.8%. FTIR spectrum showed that the surface functional groups of virgin and regenerated AC did not change significantly. Pore size distributions indicated that the AC regeneration process resulted in the decrease of micropore and macropore (D>10 μm) volume and the increase of mesopore and macropore (0.1 μm

  12. JV Task 90 - Activated Carbon Production from North Dakota Lignite

    SciTech Connect

    Steven Benson; Charlene Crocker; Rokan Zaman; Mark Musich; Edwin Olson

    2008-03-31

    The Energy & Environmental Research Center (EERC) has pursued a research program for producing activated carbon from North Dakota lignite that can be competitive with commercial-grade activated carbon. As part of this effort, small-scale production of activated carbon was produced from Fort Union lignite. A conceptual design of a commercial activated carbon production plant was drawn, and a market assessment was performed to determine likely revenue streams for the produced carbon. Activated carbon was produced from lignite coal in both laboratory-scale fixed-bed reactors and in a small pilot-scale rotary kiln. The EERC was successfully able to upgrade the laboratory-scale activated carbon production system to a pilot-scale rotary kiln system. The activated carbon produced from North Dakota lignite was superior to commercial grade DARCO{reg_sign} FGD and Rheinbraun's HOK activated coke product with respect to iodine number. The iodine number of North Dakota lignite-derived activated carbon was between 600 and 800 mg I{sub 2}/g, whereas the iodine number of DARCO FGD was between 500 and 600 mg I{sub 2}/g, and the iodine number of Rheinbraun's HOK activated coke product was around 275 mg I{sub 2}/g. The EERC performed both bench-scale and pilot-scale mercury capture tests using the activated carbon made under various optimization process conditions. For comparison, the mercury capture capability of commercial DARCO FGD was also tested. The lab-scale apparatus is a thin fixed-bed mercury-screening system, which has been used by the EERC for many mercury capture screen tests. The pilot-scale systems included two combustion units, both equipped with an electrostatic precipitator (ESP). Activated carbons were also tested in a slipstream baghouse at a Texas power plant. The results indicated that the activated carbon produced from North Dakota lignite coal is capable of removing mercury from flue gas. The tests showed that activated carbon with the greatest iodine number

  13. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S

    2013-02-19

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  14. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S.

    2010-06-01

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  15. Nickel adsorption by sodium polyacrylate-grafted activated carbon.

    PubMed

    Ewecharoen, A; Thiravetyan, P; Wendel, E; Bertagnolli, H

    2009-11-15

    A novel sodium polyacrylate grafted activated carbon was produced by using gamma radiation to increase the number of functional groups on the surface. After irradiation the capacity for nickel adsorption was studied and found to have increased from 44.1 to 55.7 mg g(-1). X-ray absorption spectroscopy showed that the adsorbed nickel on activated carbon and irradiation-grafted activated carbon was coordinated with 6 oxygen atoms at 2.04-2.06 A. It is proposed that this grafting technique could be applied to other adsorbents to increase the efficiency of metal adsorption. PMID:19576692

  16. Grafting of activated carbon cloths for selective adsorption

    NASA Astrophysics Data System (ADS)

    Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S.

    2016-05-01

    Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

  17. Production and characterization of activated carbons from cereal grains

    SciTech Connect

    Venkatraman, A.; Walawender, W.P.; Fan, L.T.

    1996-12-31

    The term, activated carbon, is a generic name for a family of carbonaceous materials with well-developed porosities and consequently, large adsorptive capacities. Activated carbons are increasingly being consumed worldwide for environmental applications such as separation of volatiles from bulk gases and purification of water and waste-water streams. The global annual production is estimated to be around 300 million kilograms, with a rate of increase of 7% each year. Activated carbons can be prepared from a variety of raw materials. Approximately, 60% of the activated carbons generated in the United States is produced from coal; 20%, from coconut shells; and the remaining 20% from wood and other sources of biomass. The pore structure and properties of activated carbons are influenced by the nature of the starting material and the initial physical and chemical conditioning as well as the process conditions involved in its manufacture. The porous structures of charcoals and activated carbons obtained by the carbonization of kernels have been characterized.

  18. Microstructure and surface properties of lignocellulosic-based activated carbons

    NASA Astrophysics Data System (ADS)

    González-García, P.; Centeno, T. A.; Urones-Garrote, E.; Ávila-Brande, D.; Otero-Díaz, L. C.

    2013-01-01

    Low cost activated carbons have been produced via chemical activation, by using KOH at 700 °C, from the bamboo species Guadua Angustifolia and Bambusa Vulgaris Striata and the residues from shells of the fruits of Castanea Sativa and Juglans Regia as carbon precursors. The scanning electron microscopy micrographs show the conservation of the precursor shape in the case of the Guadua Angustifolia and Bambusa Vulgaris Striata activated carbons. Transmission electron microscopy analyses reveal that these materials consist of carbon platelet-like particles with variable length and thickness, formed by highly disordered graphene-like layers with sp2 content ≈ 95% and average mass density of 1.65 g/cm3 (25% below standard graphite). Textural parameters indicate a high porosity development with surface areas ranging from 850 to 1100 m2/g and average pore width centered in the supermicropores range (1.3-1.8 nm). The electrochemical performance of the activated carbons shows specific capacitance values at low current density (1 mA/cm2) as high as 161 F/g in the Juglans Regia activated carbon, as a result of its textural parameters and the presence of pseudocapacitance derived from surface oxygenated acidic groups (mainly quinones and ethers) identified in this activated carbon.

  19. Hydrogen storage on activated carbon. Final report

    SciTech Connect

    Schwarz, J.A.

    1994-11-01

    The project studied factors that influence the ability of carbon to store hydrogen and developed techniques to enhance that ability in naturally occurring and factory-produced commercial carbon materials. During testing of enhanced materials, levels of hydrogen storage were achieved that compare well with conventional forms of energy storage, including lead-acid batteries, gasoline, and diesel fuel. Using the best materials, an electric car with a modern fuel cell to convert the hydrogen directly to electricity would have a range of over 1,000 miles. This assumes that the total allowable weight of the fuel cell and carbon/hydrogen storage system is no greater than the present weight of batteries in an existing electric vehicle. By comparison, gasoline cars generally are limited to about a 450-mile range, and battery-electric cars to 40 to 60 miles. The project also developed a new class of carbon materials, based on polymers and other organic compounds, in which the best hydrogen-storing factors discovered earlier were {open_quotes}molecularly engineered{close_quotes} into the new materials. It is believed that these new molecularly engineered materials are likely to exceed the performance of the naturally occurring and manufactured carbons seen earlier with respect to hydrogen storage.

  20. Activated carbons from North Dakota lignite and leonardite

    SciTech Connect

    Young, B.C.; Olson, E.S.; Knudson, C.L.; Timpe, R.C.

    1995-12-01

    In a research and development program on carbon development, the EERC investigated key factors in the preparation of activated carbons from low-rank coals indigenous to North Dakota. The carbons were prepared for potential sorption applications with flue gas and waste liquid streams. Testing involved as-received, physically cleaned, and demineralized samples of a lignite and a leonardite. The following variables were examined: mineral matter content (7-19 wt%), carbonization temperature (350{degrees}-550{degrees}C), activation temperature (700{degrees}-1000{degrees}C), and activation time (10-60 minutes). Activated carbon samples were characterized by sorption of gaseous sulfur dioxide and liquid iodine. For both lignite and leonardite, sorption activity increased with lower mineral content and correlated with medium carbonization temperature and relatively high activation temperature but relatively short activation time. Steam activation did not significantly enhance the char`s sorptive capacity. Physically cleaned leonardite char had SO{sub 2} sorptive capacities as high as 10.9% of the sample weight at ambient temperatures.

  1. DESIGN AND CONSTRUCTION OF A MOBILE ACTIVATED CARBON REGENERATOR SYSTEM

    EPA Science Inventory

    Activated carbon adsorption has become a standard procedure for the cleanup of contaminated water streams. To facilitate such cleanup at hazardous waste and spill sites, mobile carbon adsorption units have been constructed and are now in use. Their primary drawback is the logisti...

  2. Activated carbon testing for the 200 area effluent treatment facility

    SciTech Connect

    Wagner, R.N.

    1997-01-17

    This report documents pilot and laboratory scale testing of activated carbon for use in the 200 Area Effluent Treatment Facility peroxide decomposer columns. Recommendations are made concerning column operating conditions and hardware design, the optimum type of carbon for use in the plant, and possible further studies.

  3. ACTIVATED CARBON PROCESS FOR TREATMENT OF WASTEWATERS CONTAINING HEXAVALENT CHROMIUM

    EPA Science Inventory

    The removal of hexavalent chromium, Cr(VI), from dilute aqueous solution by an activated carbon process has been investigated. Two removal mechanisms were observed; hexavalent chromium species were removed by adsorption onto the interior carbon surface and/or through reduction to...

  4. Discriminative Stimulus Effects of the GABAB Receptor-Positive Modulator rac-BHFF: Comparison with GABAB Receptor Agonists and Drugs of Abuse

    PubMed Central

    Cheng, Kejun; Rice, Kenner C.

    2013-01-01

    GABAB receptor-positive modulators are thought to have advantages as potential medications for anxiety, depression, and drug addiction. They may have fewer side effects than GABAB receptor agonists, because selective enhancement of activated receptors could have effects different from nonselective activation of all receptors. To examine this, pigeons were trained to discriminate the GABAB receptor-positive modulator (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF) from its vehicle. The discriminative stimulus effects of rac-BHFF were not mimicked by the GABAB receptor agonists baclofen and γ-hydroxybutyrate (GHB), not by diazepam, and not by alcohol, cocaine, and nicotine, whose self-administration has been reported to be attenuated by GABAB receptor-positive modulators. The discriminative stimulus effects of rac-BHFF were not antagonized by the GABAB receptor antagonist 3-aminopropyl (diethoxymethyl)phosphinic acid (CGP35348) but were attenuated by the less efficacious GABAB receptor-positive modulator 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl)phenol (CGP7930), suggesting the possibility that rac-BHFF produces its discriminative stimulus effects by directly activating GABAB2 subunits of GABAB receptors. At a dose 10-fold lower than the training dose, rac-BHFF enhanced the discriminative stimulus effects of baclofen, but not of GHB. This study provides evidence that the effects of GABAB receptor-positive modulators are not identical to those of GABAB receptor agonists. In addition, the results suggest that positive modulation of GABAB receptors does not produce discriminative stimulus effects similar to those of benzodiazepines, alcohol, cocaine, and nicotine. Finally, the finding that rac-BHFF enhanced effects of baclofen but not of GHB is consistent with converging evidence that the populations of GABAB receptors mediating the effects of baclofen and GHB are not identical. PMID:23275067

  5. TESTING GUIDELINES FOR TECHNETIUM-99 ABSORPTION ON ACTIVATED CARBON

    SciTech Connect

    BYRNES ME

    2010-09-08

    CH2M HILL Plateau Remediation Company (CHPRC) is currently evaluating the potential use of activated carbon adsorption for removing technetium-99 from groundwater as a treatment method for the Hanford Site's 200 West Area groundwater pump-and-treat system. The current pump-and-treat system design will include an ion-exchange (IX) system for selective removal of technetium-99 from selected wells prior to subsequent treatment of the water in the central treatment system. The IX resin selected for technetium-99 removal is Purolite A530E. The resin service life is estimated to be approximately 66.85 days at the design technetium-99 loading rate, and the spent resin must be replaced because it cannot be regenerated. The resulting operating costs associated with resin replacement every 66.85 days are estimated at $0.98 million/year. Activated carbon pre-treatment is being evaluated as a potential cost-saving measure to offset the high operating costs associated with frequent IX resin replacement. This document is preceded by the Literature Survey of Technetium-99 Groundwater Pre-Treatment Option Using Granular Activated Carbon (SGW-43928), which identified and evaluated prior research related to technetium-99 adsorption on activated carbon. The survey also evaluated potential operating considerations for this treatment approach for the 200 West Area. The preliminary conclusions of the literature survey are as follows: (1) Activated carbon can be used to selectively remove technetium-99 from contaminated groundwater. (2) Technetium-99 adsorption onto activated carbon is expected to vary significantly based on carbon types and operating conditions. For the treatment approach to be viable at the Hanford Site, activated carbon must be capable of achieving a designated minimum technetium-99 uptake. (3) Certain radionuclides known to be present in 200 West Area groundwater are also likely to adsorb onto activated carbon. (4) Organic solvent contaminants of concern (COCs) will

  6. Selection and preparation of activated carbon for fuel gas storage

    DOEpatents

    Schwarz, James A.; Noh, Joong S.; Agarwal, Rajiv K.

    1990-10-02

    Increasing the surface acidity of active carbons can lead to an increase in capacity for hydrogen adsorption. Increasing the surface basicity can facilitate methane adsorption. The treatment of carbons is most effective when the carbon source material is selected to have a low ash content i.e., below about 3%, and where the ash consists predominantly of alkali metals alkali earth, with only minimal amounts of transition metals and silicon. The carbon is washed in water or acid and then oxidized, e.g. in a stream of oxygen and an inert gas at an elevated temperature.

  7. Natural gas storage with activated carbon from a bituminous coal

    USGS Publications Warehouse

    Sun, Jielun; Rood, M.J.; Rostam-Abadi, M.; Lizzio, A.A.

    1996-01-01

    Granular activated carbons ( -20 + 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (Vm/Vs) of some of the granular carbons produced by physical activation are about 70 cm3/cm3 which is comparable to that of BPL, a commercial activated carbon. Vm/Vs values above 100 cm3/cm3 are obtainable by grinding the granular products to - 325 mesh (<0.044 mm). The increase in Vm/Vs is due to the increase in bulk density of the carbons. Volumetric methane adsorption capacity increases with increasing pore surface area and micropore volume when normalizing with respect to sample bulk volume. Compared with steam-activated carbons, granular carbons produced by KOH activation have higher micropore volume and higher methane adsorption capacities (g/g). Their volumetric methane adsorption capacities are lower due to their lower bulk densities. Copyright ?? 1996 Elsevier Science Ltd.

  8. Sustainable Regeneration of Nanoparticle Enhanced Activated Carbon in Water

    EPA Science Inventory

    The regeneration and reuse of exhausted granular activated carbon (GAC) is an appropriate method for lowering operational and environmental costs. Advanced oxidation is a promising environmental friendly technique for GAC regeneration. The main objective of this research was to ...

  9. GRANULAR ACTIVATED CARBON ADSORPTION AND INFRARED REACTIVATION: A CASE STUDY

    EPA Science Inventory

    A study evaluated the effectiveness and cost of removing trace organic contaminants and surrogates from drinking water by granular activated carbon (GAC) adsorption. The effect of multiple reactivations of spent GAC was also evaluated. Results indicated that reactivated GAC eff...

  10. PREDICTING PREFERENTIAL ADSORPTION OF ORGANICS BY ACTIVATED CARBON

    EPA Science Inventory

    Preferential adsorption of organic compounds onto activated carbon from dilute aqueous solutions was studied to develop a comprehensive theoretical basis for predicting adsorption of multicomponent solutes. The research program investigates why some solutes are strong adsorbers, ...

  11. Preparation and characterization of activated carbon from sugarcane bagasse by physical activation with CO2 gas

    NASA Astrophysics Data System (ADS)

    Bachrun, Sutrisno; AyuRizka, Noni; Annisa, SolichaHidayat; Arif, Hidayat

    2016-01-01

    A series of experiments have been conducted to study the effects of different carbonization temperatures (400, 600, and 800oC) on characteristics of porosity in activated carbon derived from carbonized sugarcane bagassechar at activation temperature of 800oC. The results showed that the activated carbon derived from high carbonized temperature of sugarcane bagassechars had higher BET surface area, total volume, micropore volume and yield as compared to the activated carbon derived from low carbonized temperature. The BET surface area, total volume and micropore volume of activated carbon prepared from sugarcane bagassechars obtained at 800oC of carbonized temperature and activation time of 120 min were 661.46m2/g, 0.2455cm3/g and 0.1989cm3/g, respectively. The high carbonization temperature (800oC) generated a highly microporous carbonwith a Type-I nitrogen adsorption isotherm, while the low carbonization temperature (400 and 600oC) generated a mesoporous one with an intermediate between types I and IInitrogen adsorption isotherm.

  12. Dictyostelium Dock180-related RacGEFs regulate the actin cytoskeleton during cell motility.

    PubMed

    Para, Alessia; Krischke, Miriam; Merlot, Sylvain; Shen, Zhouxin; Oberholzer, Michael; Lee, Susan; Briggs, Steven; Firtel, Richard A

    2009-01-01

    Cell motility of amoeboid cells is mediated by localized F-actin polymerization that drives the extension of membrane protrusions to promote forward movements. We show that deletion of either of two members of the Dictyostelium Dock180 family of RacGEFs, DockA and DockD, causes decreased speed of chemotaxing cells. The phenotype is enhanced in the double mutant and expression of DockA or DockD complements the reduced speed of randomly moving DockD null cells' phenotype, suggesting that DockA and DockD are likely to act redundantly and to have similar functions in regulating cell movement. In this regard, we find that overexpressing DockD causes increased cell speed by enhancing F-actin polymerization at the sites of pseudopod extension. DockD localizes to the cell cortex upon chemoattractant stimulation and at the leading edge of migrating cells and this localization is dependent on PI3K activity, suggesting that DockD might be part of the pathway that links PtdIns(3,4,5)P(3) production to F-actin polymerization. Using a proteomic approach, we found that DdELMO1 is associated with DockD and that Rac1A and RacC are possible in vivo DockD substrates. In conclusion, our work provides a further understanding of how cell motility is controlled and provides evidence that the molecular mechanism underlying Dock180-related protein function is evolutionarily conserved. PMID:19037099

  13. Carbon Nanotube Materials for Substrate Enhanced Control of Catalytic Activity

    SciTech Connect

    Heben, M.; Dillon, A. C.; Engtrakul, C.; Lee, S.-H.; Kelley, R. D.; Kini, A. M.

    2007-05-01

    Carbon SWNTs are attractive materials for supporting electrocatalysts. The properties of SWNTs are highly tunable and controlled by the nanotube's circumferential periodicity and their surface chemistry. These unique characteristics suggest that architectures constructed from these types of carbon support materials would exhibit interesting and useful properties. Here, we expect that the structure of the carbon nanotube support will play a major role in stabilizing metal electrocatalysts under extreme operating conditions and suppress both catalyst and support degradation. Furthermore, the chemical modification of the carbon nanotube surfaces can be expected to alter the interface between the catalyst and support, thus, enhancing the activity and utilization of the electrocatalysts. We plan to incorporate discrete reaction sites into the carbon nanotube lattice to create intimate electrical contacts with the catalyst particles to increase the metal catalyst activity and utilization. The work involves materials synthesis, design of electrode architectures on the nanoscale, control of the electronic, ionic, and mass fluxes, and use of advanced optical spectroscopy techniques.

  14. Effects of CO 2 activation on porous structures of coconut shell-based activated carbons

    NASA Astrophysics Data System (ADS)

    Guo, Shenghui; Peng, Jinhui; Li, Wei; Yang, Kunbin; Zhang, Libo; Zhang, Shimin; Xia, Hongying

    2009-07-01

    In this paper, textural characterization of an activated carbon derived from carbonized coconut shell char obtained at carbonization temperature of 600 °C for 2 h by CO 2 activation was investigated. The effects of activation temperature, activation time and flow rate of CO 2 on the BET surface area, total volume, micropore volume and yield of activated carbons prepared were evaluated systematically. The results showed that: (i) enhancing activation temperature was favorable to the formation of pores, widening of pores and an increase in mesopores; (ii) increasing activation time was favorable to the formation of micropores and mesopores, and longer activation time would result in collapsing of pores; (iii) increasing flow rate of CO 2 was favorable to the reactions of all active sites and formation of pores, further increasing flow rate of CO 2 would lead carbon to burn out and was unfavorable to the formation of pores. The degree of surface roughness of activated carbon prepared was measured by the fractal dimension which was calculated by FHH (Frenkel-Halsey-Hill) theory. The fractal dimensions of activated carbons prepared were greater than 2.6, indicating the activated carbon samples prepared had very irregular structures, and agreed well with those of average micropore size.

  15. Water vapor adsorption on activated carbon preadsorbed with naphtalene.

    PubMed

    Zimny, T; Finqueneisel, G; Cossarutto, L; Weber, J V

    2005-05-01

    The adsorption of water vapor on a microporous activated carbon derived from the carbonization of coconut shell has been studied. Preadsorption of naphthalene was used as a tool to determine the location and the influence of the primary adsorbing centers within the porous structure of active carbon. The adsorption was studied in the pressure range p/p0=0-0.95 in a static water vapor system, allowing the investigation of both kinetic and equilibrium experimental data. Modeling of the isotherms using the modified equation of Do and Do was applied to determine the effect of preadsorption on the mechanism of adsorption. PMID:15797395

  16. Activated carbon fiber composite material and method of making

    DOEpatents

    Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

    2001-01-01

    An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

  17. Activated carbon fiber composite material and method of making

    DOEpatents

    Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

    2000-01-01

    An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

  18. Carbon-carbon bond cleavage in activation of the prodrug nabumetone.

    PubMed

    Varfaj, Fatbardha; Zulkifli, Siti N A; Park, Hyoung-Goo; Challinor, Victoria L; De Voss, James J; Ortiz de Montellano, Paul R

    2014-05-01

    Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs. PMID:24584631

  19. Carbon-Carbon Bond Cleavage in Activation of the Prodrug Nabumetone

    PubMed Central

    Varfaj, Fatbardha; Zulkifli, Siti N. A.; Park, Hyoung-Goo; Challinor, Victoria L.; De Voss, James J.

    2014-01-01

    Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs. PMID:24584631

  20. Heterotypic RPE-choroidal endothelial cell contact increases choroidal endothelial cell transmigration via PI 3-kinase and Rac1.

    PubMed

    Peterson, Lynda J; Wittchen, Erika S; Geisen, Pete; Burridge, Keith; Hartnett, M Elizabeth

    2007-04-01

    Age-related macular degeneration (AMD) is the major cause of non-preventable blindness. Severe forms of AMD involve breaching of the retinal pigment epithelial (RPE) barrier by underlying choroidal endothelial cells (CECs), followed by migration into, and subsequent neovascularization of the neurosensory retina. However, little is known about the interactions between RPE and CECs and the signaling events leading to CEC transmigration. While soluble chemotactic factors secreted from RPE can contribute to inappropriate CEC transmigration, other unidentified stimuli may play an additional role. Using a coculture model that maintains the natural structural orientation of CECs to the basal aspect of RPE, we show that "contact" with RPE and/or RPE extracellular matrix increases CEC transmigration of the RPE barrier. From a biochemical standpoint, contact between CECs and RPE results in an increase in the activity of the GTPase Rac1 within the CECs; this increase is dependent on upstream activation of PI 3-K and Akt1. To confirm a link between these signaling molecules and increased CEC transmigration, we performed transmigration assays while inhibiting both PI 3-K and Rac1 activity, and observed that both decreased CEC transmigration. We hypothesize that contact between CECs and RPE stimulates a signaling pathway involving PI 3-K, Akt1, and Rac1 that facilitates CEC transmigration across the RPE barrier, an important step in the development of neovascular AMD. PMID:17292356

  1. Heterotypic RPE-choroidal endothelial cell contact increases choroidal endothelial cell transmigration via PI 3-kinase and Rac1

    PubMed Central

    Peterson, Lynda J.; Wittchen, Erika S.; Geisen, Pete; Burridge, Keith; Hartnett, M. Elizabeth

    2008-01-01

    Age-related macular degeneration (AMD) is the major cause of non-preventable blindness. Severe forms of AMD involve breaching of the retinal pigment epithelial (RPE) barrier by underlying choroidal endothelial cells (CECs), followed by migration into, and subsequent neovascularization of the neurosensory retina. However, little is known about the interactions between RPE and CECs and the signaling events leading to CEC transmigration. While soluble chemotactic factors secreted from RPE can contribute to inappropriate CEC transmigration, other unidentified stimuli may play an additional role. Using a coculture model that maintains the natural structural orientation of CECs to the basal aspect of RPE, we show that “contact” with RPE and/or RPE extracellular matrix increases CEC transmigration of the RPE barrier. From a biochemical standpoint, contact between CECs and RPE results in an increase in the activity of the GTPase Rac1 within the CECs; this increase is dependent on upstream activation of PI 3-K and Akt1. To confirm a link between these signaling molecules and increased CEC transmigration, we performed transmigration assays while inhibiting both PI 3-K and Rac1 activity, and observed that both decreased CEC transmigration. We hypothesize that contact between CECs and RPE stimulates a signaling pathway involving PI 3-K, Akt1, and Rac1 that facilitates CEC transmigration across the RPE barrier, an important step in the development of neovascular AMD. PMID:17292356

  2. Rac1 Participates in Thermally Induced Alterations of the Cytoskeleton, Cell Morphology and Lipid Rafts, and Regulates the Expression of Heat Shock Proteins in B16F10 Melanoma Cells

    PubMed Central

    Gungor, Burcin; Gombos, Imre; Crul, Tim; Ayaydin, Ferhan; Szabó, László; Török, Zsolt; Mátés, Lajos; Vígh, László; Horváth, Ibolya

    2014-01-01

    Eukaryotic cells exhibit a characteristic response to hyperthermic treatment, involving morphological and cytoskeletal alterations and the induction of heat shock protein synthesis. Small GTPases of the Ras superfamily are known to serve as molecular switches which mediate responses to extracellular stimuli. We addressed here how small GTPase Rac1 integrates signals from heat stress and simultaneously induces various cellular changes in mammalian cells. As evidence that Rac1 is implicated in the heat shock response, we first demonstrated that both mild (41.5°C) and severe (43°C) heat shock induced membrane translocation of Rac1. Following inhibition of the activation or palmitoylation of Rac1, the size of its plasma membrane-bound pool was significantly decreased while the heat shock-induced alterations in the cytoskeleton and cell morphology were prevented. We earlier documented that the size distribution pattern of cholesterol-rich rafts is temperature dependent and hypothesized that this is coupled to the triggering mechanism of stress sensing and signaling. Interestingly, when plasma membrane localization of Rac1 was inhibited, a different and temperature independent average domain size was detected. In addition, inhibition of the activation or palmitoylation of Rac1 resulted in a strongly decreased expression of the genes of major heat shock proteins hsp25 and hsp70 under both mild and severe heat stress conditions. PMID:24586549

  3. The positive allosteric GABAB receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice.

    PubMed

    Zemoura, Khaled; Ralvenius, William T; Malherbe, Pari; Benke, Dietmar

    2016-09-01

    Neuropathic pain is associated with impaired inhibitory control of spinal dorsal horn neurons, which are involved in processing pain signals. The metabotropic GABAB receptor is an important component of the inhibitory system and is highly expressed in primary nociceptors and intrinsic dorsal horn neurons to control their excitability. Activation of GABAB receptors with the orthosteric agonist baclofen effectively reliefs neuropathic pain but is associated with severe side effects that prevent its widespread application. The recently developed positive allosteric GABAB receptor modulators lack most of these side effects and are therefore promising drugs for the treatment of pain. Here we tested the high affinity positive allosteric modulator rac-BHFF for its ability to relief neuropathic pain induced by chronic constriction of the sciatic nerve in mice. rac-BHFF significantly increased the paw withdrawal threshold to mechanical stimulation in healthy mice, indicating an endogenous GABABergic tone regulating the sensitivity to mechanical stimuli. Surprisingly, rac-BHFF displayed no analgesic activity in neuropathic mice although GABAB receptor expression was not affected in the dorsal horn as shown by quantitative receptor autoradiography. However, activation of spinal GABAB receptors by intrathecal injection of baclofen reduced hyperalgesia and its analgesic effect was considerably potentiated by co-application of rac-BHFF. These results indicate that under conditions of neuropathic pain the GABAergic tone is too low to provide a basis for allosteric modulation of GABAB receptors. However, allosteric modulators would be well suited as an add-on to reduce the dose of baclofen required to achieve analgesia. PMID:27108932

  4. The IQGAP-related protein DGAP1 interacts with Rac and is involved in the modulation of the F-actin cytoskeleton and control of cell motility.

    PubMed

    Faix, J; Clougherty, C; Konzok, A; Mintert, U; Murphy, J; Albrecht, R; Mühlbauer, B; Kuhlmann, J

    1998-10-01

    DGAP1 of Dictyostelium discoideum is a cell cortex associated 95 kDa protein that shows homology to both RasGTPase-activating proteins (RasGAPs) and RasGAP-related proteins. When tested for RasGAP activity, recombinant DGAP1 protein did not promote the GTPase activity of human H-Ras or of Dictyostelium RasG in vitro. Instead, DGAP1 bound to Dictyostelium Rac1A and human Rac1, but not to human Cdc42. DGAP1 preferentially interacted with the activated GTP-bound forms of Rac1 and Rac1A, but did not affect the GTPase activities. Since Rho-type GTPases are implicated in the formation of specific F-actin structures and in the control of cell morphology, the microfilament system of mutants that either lack or overexpress DGAP1 has been analysed. DGAP1-null mutants showed elevated levels of F-actin that was organised in large leading edges, membrane ruffles or numerous large filopods. Expression of actin fused to green fluorescent protein (GFP) was used to monitor the actin dynamics in these cells, and revealed that the F-actin cytoskeleton of DGAP1-null cells was rapidly re-arranged to form ruffles and filopods. Conversely, in DGAP1-overexpressing cells, the formation of cellular projections containing F-actin was largely suppressed. Measurement of cell migration demonstrated that DGAP1 expression is inversely correlated with the speed of cell motility. PMID:9739079

  5. Wet oxidative regeneration of activated carbon loaded with reactive dye.

    PubMed

    Shende, R V; Mahajani, V V

    2002-01-01

    Wet Oxidative Regeneration (WOR) of powdered activated carbon (PAC) and granular activated carbon (GAC) loaded with the reactive dyes, namely chemictive brilliant blue R and cibacron turquoise blue G, was studied. Attempts were made to regenerate the loaded carbons designated now as spent carbon. A slurry (10% w/v) of spent carbon in distilled water was oxidized by wet oxidation in the temperature range of 150-250 degrees C using oxygen partial pressures between 0.69-1.38 MPa in an 1 1 SS 316 autoclave. The percent regeneration was determined from a ratio, X(RC)/X(VC), corresponding to an equilibrium adsorption capacity of regenerated carbon/equilibrium adsorption capacity of virgin carbon from an initial adsorption period of 3 h. It was observed that the regeneration mainly occurred due to the oxidation of the adsorbates taking place on the surface of carbon. It was possible to regenerate the spent GAC and PAC to the extent of more than 98% (approximately X(RC)/X(VC) > 0.98) by wet oxidation. After four consecutive cycles of adsorption and regeneration using the same stocks of GAC, carbon weight loss observed at 200 degrees C was about 40%. SEM studies of the regenerated carbon showed widening of the pores and loss of structure between the adjacent pores as compared with the virgin carbon. PAC was found to be more suitable as compared with GAC for the adsorption and wet oxidative regeneration processes to treat the aqueous solution containing lower concentration of unhydrolyzed reactive dye. The suitability of wet oxidative regeneration is demonstrated at a bench scale to treat the synthetic reactive dye solution. PMID:11942707

  6. mTOR Directs Breast Morphogenesis through the PKC-alpha-Rac1 Signaling Axis

    PubMed Central

    Morrison, Meghan M.; Young, Christian D.; Wang, Shan; Sobolik, Tammy; Sanchez, Violeta M.; Hicks, Donna J.; Cook, Rebecca S.; Brantley-Sieders, Dana M.

    2015-01-01

    Akt phosphorylation is a major driver of cell survival, motility, and proliferation in development and disease, causing increased interest in upstream regulators of Akt like mTOR complex 2 (mTORC2). We used genetic disruption of Rictor to impair mTORC2 activity in mouse mammary epithelia, which decreased Akt phosphorylation, ductal length, secondary branching, cell motility, and cell survival. These effects were recapitulated with a pharmacological dual inhibitor of mTORC1/mTORC2, but not upon genetic disruption of mTORC1 function via Raptor deletion. Surprisingly, Akt re-activation was not sufficient to rescue cell survival or invasion, and modestly increased branching of mTORC2-impaired mammary epithelial cells (MECs) in culture and in vivo. However, another mTORC2 substrate, protein kinase C (PKC)-alpha, fully rescued mTORC2-impaired MEC branching, invasion, and survival, as well as branching morphogenesis in vivo. PKC-alpha-mediated signaling through the small GTPase Rac1 was necessary for mTORC2-dependent mammary epithelial development during puberty, revealing a novel role for Rictor/mTORC2 in MEC survival and motility during branching morphogenesis through a PKC-alpha/Rac1-dependent mechanism. PMID:26132202

  7. Detecting Extracellular Carbonic Anhydrase Activity Using Membrane Inlet Mass Spectrometry

    PubMed Central

    Delacruz, Joannalyn; Mikulski, Rose; Tu, Chingkuang; Li, Ying; Wang, Hai; Shiverick, Kathleen T.; Frost, Susan C.; Horenstein, Nicole A.; Silverman, David N.

    2010-01-01

    Current research into the function of carbonic anhydrases in cell physiology emphasizes the role of membrane-bound carbonic anhydrases, such as carbonic anhydrase IX that has been identified in malignant tumors and is associated with extracellular acidification as a response to hypoxia. We present here a mass spectrometric method to determine the extent to which total carbonic anhydrase activity is due to extracellular carbonic anhydrase in whole cell preparations. The method is based on the biphasic rate of depletion of 18O from CO2 measured by membrane inlet mass spectrometry. The slopes of the biphasic depletion are a sensitive measure of the presence of carbonic anhydrase outside and inside of the cells. This property is demonstrated here using suspensions of human red cells in which external carbonic anhydrase was added to the suspending solution. It is also applied to breast and prostate cancer cells which both express exofacial carbonic anhydrase IX. Inhibition of external carbonic anhydrase is achieved by use of a membrane impermeant inhibitor that was synthesized for this purpose, p-aminomethylbenzenesulfonamide attached to a polyethyleneglycol polymer. PMID:20417171

  8. Intact vinculin protein is required for control of cell shape, cell mechanics, and rac-dependent lamellipodia formation

    NASA Technical Reports Server (NTRS)

    Goldmann, Wolfgang H.; Ingber, Donald E.

    2002-01-01

    Studies were carried out using vinculin-deficient F9 embryonic carcinoma (gamma229) cells to analyze the relationship between structure and function within the focal adhesion protein vinculin, in the context of control of cell shape, cell mechanics, and movement. Atomic force microscopy studies revealed that transfection of the head (aa 1-821) or tail (aa 811-1066) domain of vinculin, alone or together, was unable to fully reverse the decrease in cell stiffness, spreading, and lamellipodia formation caused by vinculin deficiency. In contrast, replacement with intact vinculin completely restored normal cell mechanics and spreading regardless of whether its tyrosine phosphorylation site was deleted. Constitutively active rac also only induced extension of lamellipodia when microinjected into cells that expressed intact vinculin protein. These data indicate that vinculin's ability to physically couple integrins to the cytoskeleton, to mechanically stabilize cell shape, and to support rac-dependent lamellipodia formation all appear to depend on its intact three-dimensional structure.

  9. Adsorption of dissolved natural organic matter by modified activated carbons.

    PubMed

    Cheng, Wei; Dastgheib, Seyed A; Karanfil, Tanju

    2005-06-01

    Adsorption of dissolved natural organic matter (DOM) by virgin and modified granular activated carbons (GACs) was studied. DOM samples were obtained from two water treatment plants before (i.e., raw water) and after coagulation/flocculation/sedimentation processes (i.e., treated water). A granular activated carbon (GAC) was modified by high temperature helium or ammonia treatment, or iron impregnation followed by high temperature ammonia treatment. Two activated carbon fibers (ACFs) were also used, with no modification, to examine the effect of carbon porosity on DOM adsorption. Size exclusion chromatography (SEC) and specific ultraviolet absorbance (SUVA(254)) were employed to characterize the DOMs before and after adsorption. Iron-impregnated (HDFe) and ammonia-treated (HDN) activated carbons showed significantly higher DOM uptakes than the virgin GAC. The enhanced DOM uptake by HDFe was due to the presence of iron species on the carbon surface. The higher uptake of HDN was attributed to the enlarged carbon pores and basic surface created during ammonia treatment. The SEC and SUVA(254) results showed no specific selectivity in the removal of different DOM components as a result of carbon modification. The removal of DOM from both raw and treated waters was negligible by ACF10, having 96% of its surface area in pores smaller than 1 nm. Small molecular weight (MW) DOM components were preferentially removed by ACF20H, having 33% of its surface area in 1--3 nm pores. DOM components with MWs larger than 1600, 2000, and 2700 Da of Charleston raw, Charleston-treated, and Spartanburg-treated waters, respectively, were excluded from the pores of ACF20H. In contrast to carbon fibers, DOM components from entire MW range were removed from waters by virgin and modified GACs. PMID:15927230

  10. Preparation of activated carbons from bituminous coals with zinc chloride activation

    SciTech Connect

    Teng, H.; Yeh, T.S.

    1998-01-01

    Activated carbons were prepared by chemical activation from two Australian bituminous coals in this study. The preparation process consisted of zinc chloride impregnation followed by carbonization in nitrogen. The carbonization temperature ranges from 400 to 700 C. Experimental results reveal that an acid-washing process following the carbonization with ZnCl{sub 2} is necessary for preparing high-porosity carbons. Surface area, pore volume, and average pore diameter of the resulting carbons increase with the carbonization temperature to a maximum at 500 C and then begin to decrease. The maximum values of surface area and pore volume are larger for the carbon prepared from the coal with a lower O/C atomic ratio, while earlier findings from physical activation with CO{sub 2} have shown an opposite trend. An increase in particle size of the coal precursor leads to a reduction in porosity of the resulting carbons. The duration of the carbonization period affects the porosity of the resulting carbons, and the influence varies with the activation temperature.

  11. Composite electrodes of activated carbon derived from cassava peel and carbon nanotubes for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Taer, E.; Iwantono, Yulita, M.; Taslim, R.; Subagio, A.; Salomo, Deraman, M.

    2013-09-01

    In this paper, a composite electrode was prepared from a mixture of activated carbon derived from precarbonization of cassava peel (CP) and carbon nanotubes (CNTs). The activated carbon was produced by pyrolysis process using ZnCl2 as an activation agent. A N2 adsorption-desorption analysis for the sample indicated that the BET surface area of the activated carbon was 1336 m2 g-1. Difference percentage of CNTs of 0, 5, 10, 15 and 20% with 5% of PVDF binder were added into CP based activated carbon in order to fabricate the composite electrodes. The morphology and structure of the composite electrodes were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The SEM image observed that the distribution of CNTs was homogeneous between carbon particles and the XRD pattern shown the amorphous structure of the sample. The electrodes were fabricated for supercapacitor cells with 316L stainless steel as current collector and 1 M sulfuric acid as electrolyte. An electrochemical characterization was performed by using an electrochemical impedance spectroscopy (EIS) method using a Solatron 1286 instrument and the addition of CNTs revealed to improve the resistant and capacitive properties of supercapacitor cell.

  12. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons

    NASA Astrophysics Data System (ADS)

    Brooks, A. J.; Lim, Hyung-nam; Kilduff, James E.

    2012-07-01

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7-8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π-π electron donor-acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion effects

  13. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons.

    PubMed

    Brooks, A J; Lim, Hyung-nam; Kilduff, James E

    2012-07-27

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7-8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π-π electron donor-acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion effects

  14. Involvement of geranylgeranylation of Rho and Rac GTPases in adipogenic and RANKL expression, which was inhibited by simvastatin.

    PubMed

    Baba, T T; Ohara-Nemoto, Y; Miyazaki, T; Nemoto, T K

    2013-12-01

    Simvastatin suppresses myoblast differentiation via inhibition of Rac GTPase, which is involved in the mevalonic acid pathway that produces cholesterol. Statins also inhibit adipogenic differentiation and receptor activator of NFκB ligand (RANKL) expression, possibly through the mevalonic acid pathway, although the involvement of that pathway and effector proteins in these cellular events has not been fully clarified. In the present study, we aimed to elucidate the mechanism of the effects of simvastatin on adipogenic differentiation and calcitriol-induced RANKL expression in bone marrow stromal ST2 cells. Adipogenesis and mRNA up-regulation of peroxisome proliferator-activated receptor γ and adipocyte fatty acid-binding protein were induced by troglitazone, and those events were efficiently inhibited by simvastatin. In addition, RANKL expression induced by calcitriol was abrogated by simvastatin in ST2 cells. The inhibitory effects of simvastatin were adequately compensated by the addition of either mevalonic acid or an intermediate of the mevalonic acid pathway, geranylgeranyl pyrophosphate, but not by another intermediate, farnesyl pyrophosphate. These findings suggest that protein geranylgeranylation is related to cellular differentiation in those two directions. Furthermore, inhibitor analysis demonstrated that Rac GTPase is involved in adipogenic differentiation, whereas Rho GTPase was found to be involved in RANKL expression. Taken together, the present findings suggest that geranylgeranylation of Rho family GTPase is involved in both adipogenesis and RANKL expression of stromal cells, while Rac GTPase is involved in adipogenesis and Rho GTPase in RANKL expression. PMID:23339033

  15. Survival of selected bacterial species in sterilized activated carbon filters and biological activated carbon filters.

    PubMed Central

    Rollinger, Y; Dott, W

    1987-01-01

    The survival of selected hygienically relevant bacterial species in activated carbon (AC) filters on a bench scale was investigated. The results revealed that after inoculation of the test strains the previously sterilized AC absorbed all bacteria (10(6) to 10(7)). After a period of 6 to 13 days without countable bacteria in the effluent, the numbers of Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas putida increased up to 10(4) to 10(5) CFU/ml of effluent and 10(6) to 10(7) CFU/g of AC. When Klebsiella pneumoniae and Streptococcus faecalis were used, no growth in filters could be observed. The numbers of E. coli, P. aeruginosa, and P. putida, however, decreased immediately and showed no regrowth in nonsterile AC from a filter which had been continuously connected to running tap water for 2 months. Under these conditions an autochthonous microflora developed on the carbon surface which could be demonstrated by scanning electron microscopy and culturing methods (heterotrophic plate count). These bacteria reduced E. coli, P. aeruginosa, and P. putida densities in the effluent by a factor of more than 10(5) within 1 to 5 days. The hypothesis that antagonistic substances of the autochthonous microflora were responsible for the elimination of the artificial contamination could not be confirmed because less than 1% of the isolates of the autochthonous microflora were able to produce such substances as indicated by in vitro tests. Competition for limiting nutrients was thought to be the reason for the observed effects. PMID:3579281

  16. Scalable Total Synthesis of rac-Jungermannenones B and C.

    PubMed

    Liu, Weilong; Li, Houhua; Cai, Pei-Jun; Wang, Zhen; Yu, Zhi-Xiang; Lei, Xiaoguang

    2016-02-24

    Reported is the first scalable synthesis of rac-jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6-dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6-dienyne reductive radical cyclization. PMID:26823176

  17. Activated Carbon Composites for Air Separation

    SciTech Connect

    Contescu, Cristian I; Baker, Frederick S; Tsouris, Costas; McFarlane, Joanna

    2008-03-01

    In continuation of the development of composite materials for air separation based on molecular sieving properties and magnetic fields effects, several molecular sieve materials were tested in a flow system, and the effects of temperature, flow conditions, and magnetic fields were investigated. New carbon materials adsorbents, with and without pre-loaded super-paramagnetic nanoparticles of Fe3O4 were synthesized; all materials were packed in chromatographic type columns which were placed between the poles of a high intensity, water-cooled, magnet (1.5 Tesla). In order to verify the existence of magnetodesorption effect, separation tests were conducted by injecting controlled volumes of air in a flow of inert gas, while the magnetic field was switched on and off. Gas composition downstream the column was analyzed by gas chromatography and by mass spectrometry. Under the conditions employed, the tests confirmed that N2 - O2 separation occurred at various degrees, depending on material's intrinsic properties, temperature and flow rate. The effect of magnetic fields, reported previously for static conditions, was not confirmed in the flow system. The best separation was obtained for zeolite 13X at sub-ambient temperatures. Future directions for the project include evaluation of a combined system, comprising carbon and zeolite molecular sieves, and testing the effect of stronger magnetic fields produced by cryogenic magnets.

  18. Preparation and characterization of activated carbon aerogel spheres

    NASA Astrophysics Data System (ADS)

    Liu, Ning; Liu, Fengshou

    2014-03-01

    Activated carbon aerogel spheres (A-CAS) were successfully prepared by imposing KOH activation on aerogel spheres. It was found that the activation treatment did not destroy the order of the surface of the carbon aerogel spheres (CAS), but it improved the pore structure and adsorption performance of the products. With increasing burn-off, the amount of mesopores first decreased and then increased, with the amount of micropores continuously increasing. The highest measured BET surface area and micropore surface area reached 1198 and 786 m2/g, respectively. The adsorption capacity of benzene organic vapour on the A-CAS is more than eight times as large as that on CAS.

  19. Porous texture evolution in Nomex-derived activated carbon fibers.

    PubMed

    Villar-Rodil, S; Denoyel, R; Rouquerol, J; Martínez-Alonso, A; Tascón, J M D

    2002-08-01

    In the present work, the textural evolution of a series of activated carbon fibers with increasing burn-off degree, prepared by the pyrolysis and steam activation of Nomex aramid fibers, is followed by measurements of physical adsorption of N(2) (77 K) and CO(2) (273 K) and immersion calorimetry into different liquids (dichloromethane, benzene, cyclohexane). The immersion calorimetry results are discussed in depth, paying special attention to the choice of the reference material. The activated carbon fibers studied possess an essentially homogeneous microporous texture, which suggests that these materials may be applied in gas separation, either directly or with additional CVD treatment. PMID:16290775

  20. Thermochemically activated carbon as an electrode material for supercapacitors.

    PubMed

    Ostafiychuk, Bogdan K; Budzulyak, Ivan M; Rachiy, Bogdan I; Vashchynsky, Vitalii M; Mandzyuk, Volodymyr I; Lisovsky, Roman P; Shyyko, Lyudmyla O

    2015-01-01

    The results of electrochemical studies of nanoporous carbon as electrode material for electrochemical capacitors (EC) are presented in this work. Nanoporous carbon material (NCM) was obtained from the raw materials of plant origin by carbonization and subsequent activation in potassium hydroxide. It is established that there is an optimal ratio of 1:1 between content of KOH and carbon material at chemical activation, while the maximum specific capacity of NCM is 180 F/g. An equivalent electrical circuit, which allows modeling of the impedance spectra in the frequency range of 10(-2) to 10(5) Hz, is proposed, and a physical interpretation of each element of the electrical circuit is presented. PMID:25852362

  1. Measured Enthalpies of Adsorption of Boron-Doped Activated Carbons

    NASA Astrophysics Data System (ADS)

    Beckner, M.; Romanos, J.; Dohnke, E.; Singh, A.; Schaeperkoetter, J.; Stalla, D.; Burress, J.; Jalisatgi, S.; Suppes, G.; Hawthorne, M. F.; Yu, P.; Wexler, C.; Pfeifer, P.

    2012-02-01

    There is significant interest in the properties of boron-doped activated carbons for their potential to improve hydrogen storage.ootnotetextMultiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage, P. Pfeifer et al. DOE Hydrogen Program 2011 Annual Progress Report, IV.C.3, 444-449 (2011). Boron-doped activated carbons have been produced using a process involving the pyrolysis of decaborane (B10H14) and subsequent high-temperature annealing. In this talk, we will present a systematic study of the effect of different boron doping processes on the samples' structure, hydrogen sorption, and surface chemistry. Initial room temperature experiments show a 20% increase in the hydrogen excess adsorption per surface area compared to the undoped material. Experimental enthalpies of adsorption will be presented for comparison to theoretical predictions for boron-doped carbon materials. Additionally, results from a modified version of the doping process will be presented.

  2. Involvement of the Rac1-IRSp53-Wave2-Arp2/3 Signaling Pathway in HIV-1 Gag Particle Release in CD4 T Cells

    PubMed Central

    Thomas, Audrey; Mariani-Floderer, Charlotte; López-Huertas, Maria Rosa; Gros, Nathalie; Hamard-Péron, Elise; Favard, Cyril; Ohlmann, Theophile; Alcamí, José

    2015-01-01

    ABSTRACT During HIV-1 assembly, the Gag viral proteins are targeted and assemble at the inner leaflet of the cell plasma membrane. This process could modulate the cortical actin cytoskeleton, located underneath the plasma membrane, since actin dynamics are able to promote localized membrane reorganization. In addition, activated small Rho GTPases are known for regulating actin dynamics and membrane remodeling. Therefore, the modulation of such Rho GTPase activity and of F-actin by the Gag protein during virus particle formation was considered. Here, we studied the implication of the main Rac1, Cdc42, and RhoA small GTPases, and some of their effectors, in this process. The effect of small interfering RNA (siRNA)-mediated Rho GTPases and silencing of their effectors on Gag localization, Gag membrane attachment, and virus-like particle production was analyzed by immunofluorescence coupled to confocal microscopy, membrane flotation assays, and immunoblot assays, respectively. In parallel, the effect of Gag expression on the Rac1 activation level was monitored by G-LISA, and the intracellular F-actin content in T cells was monitored by flow cytometry and fluorescence microscopy. Our results revealed the involvement of activated Rac1 and of the IRSp53-Wave2-Arp2/3 signaling pathway in HIV-1 Gag membrane localization and particle release in T cells as well as a role for actin branching and polymerization, and this was solely dependent on the Gag viral protein. In conclusion, our results highlight a new role for the Rac1-IRSp53-Wave2-Arp2/3 signaling pathway in the late steps of HIV-1 replication in CD4 T lymphocytes. IMPORTANCE During HIV-1 assembly, the Gag proteins are targeted and assembled at the inner leaflet of the host cell plasma membrane. Gag interacts with specific membrane phospholipids that can also modulate the regulation of cortical actin cytoskeleton dynamics. Actin dynamics can promote localized membrane reorganization and thus can be involved in

  3. FENTON-DRIVEN REGENERATION OF GRANULAR ACTIVATED CARBON: A TECHNOLOGY OVERVIEW

    EPA Science Inventory

    A Fenton-driven mechanism for regenerating spent granular activated carbon (GAC) involves the combined, synergistic use of two reliable and well established treatment technologies - adsorption onto activated carbon and Fenton oxidation. During carbon adsorption treatment, enviro...

  4. Treatment of activated carbon to enhance catalytic activity for reduction of nitric oxide with ammonia

    SciTech Connect

    Ku, B.J.; Rhee, H.K. . Dept. of Chemical Engineering); Lee, J.K.; Park, D. )

    1994-11-01

    Catalytic activity of activated carbon treated with various techniques was examined in a fixed bed reactor for the reduction of nitric oxide with ammonia at 150 C. Activated carbon derived from coconut shell impregnated with an aqueous solution of ammonium sulfate, further treated with sulfuric acid, dried at 120 C, and then heated in an inert gas stream at 400 C, showed the highest catalytic activity within the range of experimental conditions. The enhancement of catalytic activity of modified activated carbon could be attributed to the increase in the amount of oxygen function groups which increased the adsorption site for ammonia. Catalytic activity of activated carbons depended on the surface area and the oxygen content as well.

  5. Bacteria associated with granular activated carbon particles in drinking water.

    PubMed Central

    Camper, A K; LeChevallier, M W; Broadaway, S C; McFeters, G A

    1986-01-01

    A sampling protocol was developed to examine particles released from granular activated carbon filter beds. A gauze filter/Swinnex procedure was used to collect carbon fines from 201 granular activated carbon-treated drinking water samples over 12 months. Application of a homogenization procedure (developed previously) indicated that 41.4% of the water samples had heterotrophic plate count bacteria attached to carbon particles. With the enumeration procedures described, heterotrophic plate count bacteria were recovered at an average rate of 8.6 times higher than by conventional analyses. Over 17% of the samples contained carbon particles colonized with coliform bacteria as enumerated with modified most-probable-number and membrane filter techniques. In some instances coliform recoveries were 122 to 1,194 times higher than by standard procedures. Nearly 28% of the coliforms attached to these particles in drinking water exhibited the fecal biotype. Scanning electron micrographs of carbon fines from treated drinking water showed microcolonies of bacteria on particle surfaces. These data indicate that bacteria attached to carbon fines may be an important mechanism by which microorganisms penetrate treatment barriers and enter potable water supplies. PMID:3767356

  6. Biofuel intercropping effects on soil carbon and microbial activity.

    PubMed

    Strickland, Michael S; Leggett, Zakiya H; Sucre, Eric B; Bradford, Mark A

    2015-01-01

    Biofuels will help meet rising demands for energy and, ideally, limit climate change associated with carbon losses from the biosphere to atmosphere. Biofuel management must therefore maximize energy production and maintain ecosystem carbon stocks. Increasingly, there is interest in intercropping biofuels with other crops, partly because biofuel production on arable land might reduce availability and increase the price of food. One intercropping approach involves growing biofuel grasses in forest plantations. Grasses differ from trees in both their organic inputs to soils and microbial associations. These differences are associated with losses of soil carbon when grasses become abundant in forests. We investigated how intercropping switchgrass (Panicum virgalum), a major candidate for cellulosic biomass production, in loblolly pine (Pinus taeda) plantations affects soil carbon, nitrogen, and microbial dynamics. Our design involved four treatments: two pine management regimes where harvest residues (i.e., biomass) were left in place or removed, and two switchgrass regimes where the grass was grown with pine under the same two biomass scenarios (left or removed). Soil variables were measured in four 1-ha replicate plots in the first and second year following switchgrass planting. Under switchgrass intercropping, pools of mineralizable and particulate organic matter carbon were 42% and 33% lower, respectively. These declines translated into a 21% decrease in total soil carbon in the upper 15 cm of the soil profile, during early stand development. The switchgrass effect, however, was isolated to the interbed region where switchgrass is planted. In these regions, switchgrass-induced reductions in soil carbon pools with 29%, 43%, and 24% declines in mineralizable, particulate, and total soil carbon, respectively. Our results support the idea that grass inputs to forests can prime the activity of soil organic carbon degrading microbes, leading to net reductions in stocks

  7. [Comparison study on adsorption of middle molecular substances with multiwalled carbon nanotubes and activated carbon].

    PubMed

    Li, Guifeng; Wan, Jianxin; Huang, Xiangqian; Zeng, Qiao; Tang, Jing

    2011-08-01

    In recent years, multi-walled carbon nanotubes (MWCTs) are very favorable to the adsorption of middle molecular substances in the hemoperfusion because of their multiporous structure, large surface area and high reactivity, which are beneficial to the excellent absorption properties. The purpose of this study was to study the MWCTs on the adsorption capacity of the middle molecular substances. Vitamin B12 (VB12) was selected as a model of the middle molecular substances. The morphologies of MWCTs and activated carbon from commercial "carbon kidney" were observed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The adsorption behavior of VB12 was compared to each other with UV-visible absorption spectra. The MWCTs formed a sophistaicate gap structure, and compared to the activated carbon, MWCTs had a larger surface area. By Langmuir equation and Freundlich equation fitting analysis, VB12 adsorption on MWCTs is fit for multi-molecular layer adsorption, and the adsorption type of activated carbon is more inclined to the model corresponding to Langmuir monolayer adsorption. The adsorption rate of MWCTs is faster than that of the activated carbon and the adsorption capacity is greater, which could be expected to become the new adsorbent in the hemoperfusion. PMID:21936376

  8. Carbon dioxide-activated carbons from almond tree pruning: Preparation and characterization

    NASA Astrophysics Data System (ADS)

    Gañán, J.; González, J. F.; González-García, C. M.; Ramiro, A.; Sabio, E.; Román, S.

    2006-06-01

    Activated carbons were prepared from almond tree pruning by non-catalytic and catalytic gasification with carbon dioxide and their surface characteristics were investigated. In both series a two-stage activation procedure (pyrolysis at 800 °C in nitrogen atmosphere, followed by carbon dioxide activation) was used for the production of activated samples. In non-catalytic gasification, the effect of the temperature (650-800 °C for 1 h) and the reaction time (1-12 h at 650 °C) on the surface characteristics of the prepared samples was investigated. Carbons were characterized by means of nitrogen adsorption isotherms at 77 K. The textural parameters of the carbons present a linear relation with the conversion degree until a value of approximately 40%, when they come independent from both parameters studied. The highest surface area obtained for this series was 840 m 2 g -1. In the catalytic gasification the effect of the addition of one catalyst (K and Co) and the gasification time (2-4 h) on the surface and porosity development of the carbons was also studied. At the same conditions, Co leads to higher conversion values than K but this last gives a better porosity development.

  9. A comparison of the electrochemical behavior of carbon aerogels and activated carbon fiber cloths

    SciTech Connect

    Tran, T.D.; Alviso, C.T.; Hulsey, S.S.; Nielsen, J.K.; Pekala, R.W.

    1996-05-10

    Electrochemical capacitative behavior of carbon aerogels and commercial carbon fiber cloths was studied in 5M KOH, 3M sulfuric acid, and 0.5M tetrethylammonium tetrafluoroborate/propylene carbonate electrolytes. The resorcinol-formaldehyde based carbon aerogels with a range of denisty (0.2-0.85 g/cc) have open-cell structures with ultrafine pore sizes (5-50 nm), high surface area (400-700 m{sup 2}/g), and a solid matrix composed of interconnected particles or fibers with characteristic diameters of 10 nm. The commercial fiber cloths in the density range 0.2-04g/cc have high surface areas (1000-2500 m{sup 2}/g). The volumetric capacitances of high-density aerogels are shown to be comparable to or exceeding those from activated carbon fibers. Electrochemical behavior of these materials in various electrolytes is compared and related to their physical properties.

  10. Regulation and function of P-Rex family Rac-GEFs

    PubMed Central

    Welch, Heidi CE

    2015-01-01

    The P-Rex family are Dbl-type guanine-nucleotide exchange factors for Rac family small G proteins. They are distinguished from other Rac-GEFs through their synergistic mode of activation by the lipid second messenger phosphatidyl inositol (3,4,5) trisphosphate and the Gβγ subunits of heterotrimeric G proteins, thus acting as coincidence detectors for phosphoinositide 3-kinase and G protein coupled receptor signaling. Work in genetically-modified mice has shown that P-Rex1 has physiological importance in the inflammatory response and the migration of melanoblasts during development, whereas P-Rex2 controls the dendrite morphology of cerebellar Purkinje neurons as well as glucose homeostasis in liver and adipose tissue. Deregulation of P-Rex1 and P-Rex2 expression occurs in many types of cancer, and P-Rex2 is frequently mutated in melanoma. Both GEFs promote tumor growth or metastasis. This review critically evaluates the P-Rex literature and tools available and highlights exciting recent developments and open questions. PMID:25961466

  11. Rac1 signaling in the establishment of the fucoid algal body plan.

    PubMed

    Hable, Whitney E

    2014-01-01

    Fucoid zygotes use environmental vectors, including sunlight, to initiate a growth axis a few hours after fertilization. The first division is then transversely oriented by the growth axis, producing daughter cells of distinct fates. The tip growing rhizoid cell gives rise to the holdfast, anchoring the alga to the intertidal substratum, while the opposite thallus cell mainly generates the photosynthetic and reproductive stipe and fronds. Elaboration of this simple growth axis thus establishes the basic body plan of the adult; and elucidating the mechanisms responsible for formation of the growth axis is paramount to understanding fucoid morphogenesis. Recent studies have culminated in a model whereby sunlight, and perhaps other environmental cues, activate the signaling protein Rac1 at the rhizoid pole. Here it sets in motion nucleation of a patch of actin filaments that in turn, targets ions, proteins, and cellular processes to the future growth site. At germination, Rac1 initiates morphogenesis by inducing transformation of the patch of actin filaments to a structure that delivers vesicles to the growing tip, and a few hours later orients the spindle and cytokinetic plate. PMID:25540648

  12. Magnetically Active Carbon Nanotubes at Work.

    PubMed

    Stopin, Antoine; Pineux, Florent; Marega, Riccardo; Bonifazi, Davide

    2015-06-22

    Endohedral and exohedral assembly of magnetic nanoparticles (MNPs) and carbon nanotubes (CNTs) recently gave birth to a large body of new hybrid nanomaterials (MNPs-CNTs) featuring properties that are otherwise not in reach with only the graphitic or metallic cores themselves. These materials feature enhanced magnetically guided motions (rotation and translation), magnetic saturation and coercivity, large surface area, and thermal stability. By guiding the reader through the most significant examples in this Concept paper, we describe how researchers in the field engineered and exploited the synergistic combination of these two types of nanoparticles in a large variety of current and potential applications, such as magnetic fluid hyperthermia therapeutics and in magnetic resonance imaging to name a few. PMID:26017389

  13. Wsp1 Is Downstream of Cin1 and Regulates Vesicle Transport and Actin Cytoskeleton as an Effector of Cdc42 and Rac1 in Cryptococcus neoformans

    PubMed Central

    Shen, Gui; Zhou, Erxun; Alspaugh, J. Andrew

    2012-01-01

    Human Wiskott-Aldrich syndrome protein (WASP) is a scaffold linking upstream signals to the actin cytoskeleton. In response to intersectin ITSN1 and Rho GTPase Cdc42, WASP activates the Arp2/3 complex to promote actin polymerization. The human pathogen Cryptococcus neoformans contains the ITSN1 homolog Cin1 and the WASP homolog Wsp1, which share more homology with human proteins than those of other fungi. Here we demonstrate that Cin1, Cdc42/Rac1, and Wsp1 function in an effector pathway similar to that of mammalian models. In the cin1 mutant, expression of the autoactivated Wsp1-B-GBD allele partially suppressed the mutant defect in endocytosis, and expression of the constitutively active CDC42Q61L allele restored normal actin cytoskeleton structures. Similar phenotypic suppression can be obtained by the expression of a Cdc42-green fluorescent protein (GFP)-Wsp1 fusion protein. In addition, Rac1, which was found to exhibit a role in early endocytosis, activates Wsp1 to regulate vacuole fusion. Rac1 interacted with Wsp1 and depended on Wsp1 for its vacuolar membrane localization. Expression of the Wsp1-B-GBD allele restored vacuolar membrane fusion in the rac1 mutant. Collectively, our studies suggest novel ways in which this pathogenic fungus has adapted conserved signaling pathways to control vesicle transport and actin organization, likely benefiting survival within infected hosts. PMID:22327008

  14. Breakthrough CO₂ adsorption in bio-based activated carbons.

    PubMed

    Shahkarami, Sepideh; Azargohar, Ramin; Dalai, Ajay K; Soltan, Jafar

    2015-08-01

    In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide (KOH) activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25-65°C and inlet CO2 concentration range of 10-30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm(3)/g and surface area of 1400 m(2)/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration. PMID:26257348

  15. P-Rex and Vav Rac-GEFs in platelets control leukocyte recruitment to sites of inflammation

    PubMed Central

    Pan, Dingxin; Amison, Richard T.; Riffo-Vasquez, Yanira; Spina, Domenico; Cleary, Simon J.; Wakelam, Michael J.; Page, Clive P.; Pitchford, Simon C.

    2015-01-01

    The small GTPase Rac is required for neutrophil recruitment during inflammation, but its guanine-nucleotide exchange factor (GEF) activators seem dispensable for this process, which led us to investigate the possibility of cooperation between Rac-GEF families. Thioglycollate-induced neutrophil recruitment into the peritoneum was more severely impaired in P-Rex1−/− Vav1−/− (P1V1) or P-Rex1−/− Vav3−/− (P1V3) mice than in P-Rex null or Vav null mice, suggesting cooperation between P-Rex and Vav Rac-GEFs in this process. Neutrophil transmigration and airway infiltration were all but lost in P1V1 and P1V3 mice during lipopolysaccharide (LPS)-induced pulmonary inflammation, with altered intercellular adhesion molecule 1-dependent slow neutrophil rolling and strongly reduced L- and E-selectin–dependent adhesion in airway postcapillary venules. Analysis of adhesion molecule expression, neutrophil adhesion, spreading, and migration suggested that these defects were only partially neutrophil-intrinsic and were not obviously involving vascular endothelial cells. Instead, P1V1 and P1V3 platelets recapitulated the impairment of LPS-induced intravascular neutrophil adhesion and recruitment, showing P-Rex and Vav expression in platelets to be crucial. Similarly, during ovalbumin-induced allergic inflammation, pulmonary recruitment of P1V1 and P1V3 eosinophils, monocytes, and lymphocytes was compromised in a platelet-dependent manner, and airway inflammation was essentially abolished, resulting in improved airway responsiveness. Therefore, platelet P-Rex and Vav family Rac-GEFs play important proinflammatory roles in leukocyte recruitment. PMID:25538043

  16. A General Methodology for Evaluation of Carbon Sequestration Activities and Carbon Credits

    SciTech Connect

    Klasson, KT

    2002-12-23

    A general methodology was developed for evaluation of carbon sequestration technologies. In this document, we provide a method that is quantitative, but is structured to give qualitative comparisons despite changes in detailed method parameters, i.e., it does not matter what ''grade'' a sequestration technology gets but a ''better'' technology should receive a better grade. To meet these objectives, we developed and elaborate on the following concepts: (1) All resources used in a sequestration activity should be reviewed by estimating the amount of greenhouse gas emissions for which they historically are responsible. We have done this by introducing a quantifier we term Full-Cycle Carbon Emissions, which is tied to the resource. (2) The future fate of sequestered carbon should be included in technology evaluations. We have addressed this by introducing a variable called Time-adjusted Value of Carbon Sequestration to weigh potential future releases of carbon, escaping the sequestered form. (3) The Figure of Merit of a sequestration technology should address the entire life-cycle of an activity. The figures of merit we have developed relate the investment made (carbon release during the construction phase) to the life-time sequestration capacity of the activity. To account for carbon flows that occur during different times of an activity we incorporate the Time Value of Carbon Flows. The methodology we have developed can be expanded to include financial, social, and long-term environmental aspects of a sequestration technology implementation. It does not rely on global atmospheric modeling efforts but is consistent with these efforts and could be combined with them.

  17. Cla4, but not Rac1, regulates the filamentous response of Ustilago maydis to low ammonium conditions

    PubMed Central

    Lovely, C. Ben

    2011-01-01

    Ustilago maydis, the fungal pathogen of maize, undergoes a dimorphic transition from budding yeast-like growth to filamentous growth, both as part of its program for pathogenesis and distinctly, in response to environmental cues, such as acid pH or low nitrogen availability. Smu1 is a p21-activated protein kinase (PAK) with roles in both the mating response required for the former function, as well as for the nutrient response. Hsl7 may be a negative regulator of Smu1 and appears to play a role in cell length and cell cycle.  Additional proteins that participate in cell polarity and filamentation pathways include the small G protein, Rac1, and its effector PAK kinase, Cla4. Here we describe further experiments that explore the roles of Cla4 and Rac1 in the response to nitrogen availability. While deletion of rac1severely delays filamentous growth on solid media low in ammonium (SLAD), we found that deletion of cla4 does not abolish filamentous cell morphology on solid SLAD. Unexpectedly, however, the Dcla4 mutants also filament in liquid SLAD. The filamentous cell morphology of the cla4 mutant in liquid SLAD has only been seen previously for one other mutant, a strain deleted for hsl7 that simultaneously over-expresses smu1.  PMID:22446524

  18. RacA-Mediated ROS Signaling Is Required for Polarized Cell Differentiation in Conidiogenesis of Aspergillus fumigatus

    PubMed Central

    Chi, Myoung-Hwan; Craven, Kelly D.

    2016-01-01

    Conidiophore development of fungi belonging to the genus Aspergillus involves dynamic changes in cellular polarity and morphogenesis. Synchronized differentiation of phialides from the subtending conidiophore vesicle is a good example of the transition from isotropic to multi-directional polarized growth. Here we report a small GTPase, RacA, which is essential for reactive oxygen species (ROS) production in the vesicle as well as differentiation of phialides in Aspergillus fumigatus. We found that wild type A. fumigatus accumulates ROS in these conidiophore vesicles and that null mutants of racA did not, resulting in the termination of conidiophore development in this early vesicle stage. Further, we found that stress conditions resulting in atypical ROS accumulation coincide with partial recovery of phialide emergence but not subsequent apical dominance of the phialides in the racA null mutant, suggesting alternative means of ROS generation for the former process that are lacking in the latter. Elongation of phialides was also suppressed by inhibition of NADPH-oxidase activity. Our findings provide not only insights into role of ROS in fungal cell polarity and morphogenesis but also an improved model for the developmental regulatory pathway of conidiogenesis in A. fumigatus. PMID:26890813

  19. Chars pyrolyzed from oil palm wastes for activated carbon preparation

    SciTech Connect

    Lua, A.C.; Guo, J.

    1999-01-01

    Chars pyrolyzed from extracted oil palm fibers for the preparation of activated carbons were studied. The effects of pyrolysis temperature and hold time on density, porosity, yield, BET and micropore surface areas, total pore volume, and pore size distributions of chars were investigated. The optimum conditions for pyrolysis were found to be at a pyrolysis temperature of 850 C for a hold time of 3.5 h. Scanning electron micrographs of the char surfaces verified the presence of porosities. The experimental results showed that it was feasible to produce chars with high BET and micropore surface areas from extracted oil palm fibers. The resulting chars will be subjected to steam or carbon dioxide activation to prepare activated carbons for use as gas adsorbents for air pollution control.

  20. Modified Activated Carbon to be Used in Clinical Applications

    NASA Astrophysics Data System (ADS)

    Fernando, M. S.; de Silva, W. R. M.; de Silva, K. M. N.

    2014-11-01

    In this study a novel nano composite of hydroxyapatite nano particles impregnated activated carbon (C-HAp), which was synthesized in our own method, was used in iron adsorption studies. The study was conducted in order to investigate the potential of using C-HAp nanocomposite to be used in clinical detoxifications such as acute iron toxicity where the use of Activated carbon (GAC) is not very effective. Adsorption studies were conducted for synthetic solutions of Fe2+, Fe3+ and iron syrup using GAC, C-HAp and neat HAp as adsorbents. According to the results C-HAp nano composite showed improved properties than GAC in adsorbing Fe2+, Fe3+ and also Fe ions in iron syrup solutions. Thus the results of the in-vitro studies of iron adsorption studies indicated the potential of using C-HAp as an alternative to activated carbon in such clinical applications.

  1. Impact of sulfur oxides on mercury capture by activated carbon.

    PubMed

    Presto, Albert A; Granite, Evan J

    2007-09-15

    Recent field tests of mercury removal with activated carbon injection (ACI) have revealed that mercury capture is limited in flue gases containing high concentrations of sulfur oxides (SOx). In order to gain a more complete understanding of the impact of SOx on ACl, mercury capture was tested under varying conditions of SO2 and SO3 concentrations using a packed bed reactor and simulated flue gas (SFG). The final mercury content of the activated carbons is independent of the SO2 concentration in the SFG, but the presence of SO3 inhibits mercury capture even at the lowest concentration tested (20 ppm). The mercury removal capacity decreases as the sulfur content of the used activated carbons increases from 1 to 10%. In one extreme case, an activated carbon with 10% sulfur, prepared by H2SO4 impregnation, shows almost no mercury capacity. The results suggest that mercury and sulfur oxides are in competition for the same binding sites on the carbon surface. PMID:17948811

  2. Impact of sulfur oxides on mercury capture by activated carbon

    SciTech Connect

    Albert A. Presto; Evan J. Granite

    2007-09-15

    Recent field tests of mercury removal with activated carbon injection (ACI) have revealed that mercury capture is limited in flue gases containing high concentrations of sulfur oxides (SOx). In order to gain a more complete understanding of the impact of SOx on ACI, mercury capture was tested under varying conditions of SO{sub 2} and SO{sub 3} concentrations using a packed bed reactor and simulated flue gas (SFG). The final mercury content of the activated carbons is independent of the SO{sub 2} concentration in the SFG, but the presence of SO{sub 3} inhibits mercury capture even at the lowest concentration tested (20 ppm). The mercury removal capacity decreases as the sulfur content of the used activated carbons increases from 1 to 10%. In one extreme case, an activated carbon with 10% sulfur, prepared by H{sub 2}SO{sub 4} impregnation, shows almost no mercury capacity. The results suggest that mercury and sulfur oxides are in competition for the same binding sites on the carbon surface. 30 refs., 3 figs., 2 tabs.

  3. Extending the Impact of RAC1b Overexpression to Follicular Thyroid Carcinomas.

    PubMed

    Faria, Márcia; Capinha, Liliana; Simões-Pereira, Joana; Bugalho, Maria João; Silva, Ana Luísa

    2016-01-01

    RAC1b is a hyperactive variant of the small GTPase RAC1 known to be a relevant molecular player in different cancers. Previous studies from our group lead to the evidence that its overexpression in papillary thyroid carcinoma (PTC) is associated with an unfavorable prognosis. In the present study, we intended to extend the analysis of RAC1b expression to thyroid follicular neoplasms and to seek for clinical correlations. RAC1b expression levels were determined by RT-qPCR in thyroid follicular tumor samples comprising 23 follicular thyroid carcinomas (FTCs) and 33 follicular thyroid adenomas (FTAs). RAC1b was found to be overexpressed in 33% of carcinomas while no RAC1b o