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  • American Physiological Society  (2)
  • 1
    Online Resource
    Online Resource
    Basolateral P2X 4 channels stimulate ENaC activity in Xenopus cortical collecting duct A6 cells
    American Physiological Society ; 2014
    In:  American Journal of Physiology-Renal Physiology Vol. 307, No. 7 ( 2014-10-01), p. F806-F813
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 307, No. 7 ( 2014-10-01), p. F806-F813
    Abstract: The polarized nature of epithelial cells allows for different responses to luminal or serosal stimuli. In kidney tubules, ATP is produced luminally in response to changes in luminal flow. Luminal increases in ATP have been previously shown to inhibit the renal epithelial Na + channel (ENaC). On the other hand, ATP is increased basolaterally in renal epithelia in response to aldosterone. We tested the hypothesis that basolateral ATP can stimulate ENaC function through activation of the P2X 4 receptor/channel. Using single channel cell-attached patch-clamp techniques, we demonstrated the existence of a basolaterally expressed channel stimulated by the P2X 4 agonist 2-methylthio-ATP (meSATP) in Xenopus A6 cells, a renal collecting duct principal cell line. This channel had a similar reversal potential and conductance to that of P2X 4 channels. Cell surface biotinylation of the basolateral side of these cells confirmed the basolateral presence of the P2X 4 receptor. Basolateral addition of meSATP enhanced the activity of ENaC in single channel patch-clamp experiments, an effect that was absent in cells transfected with a dominant negative P2X 4 receptor construct, indicating that activation of P2X 4 channels stimulates ENaC activity in these cells. The effect of meSATP on ENaC activity was reduced after chelation of basolateral Ca 2+ with EGTA or inhibition of phosphatidylinositol 3-kinase with LY-294002. Overall, our results show that ENaC is stimulated by P2X 4 receptor activation and that the stimulation is dependent on increases in intracellular Ca 2+ and phosphatidylinositol 3-kinase activation.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.00350.2013
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2014
    detail.hit.zdb_id: 1477287-5
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  • 2
    Online Resource
    Online Resource
    Molecular mechanisms underlying Ca 2+ -mediated motility of human pancreatic duct cells
    American Physiological Society ; 2010
    In:  American Journal of Physiology-Cell Physiology Vol. 299, No. 6 ( 2010-12), p. C1493-C1503
    Details
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 299, No. 6 ( 2010-12), p. C1493-C1503
    Abstract: We recently reported that transforming growth factor-β (TGF-β) induces an increase in cytosolic Ca 2+ ([Ca 2+ ] cyt ) in pancreatic cancer cells, but the mechanisms by which TGF-β mediates [Ca 2+ ] cyt homeostasis in these cells are currently unknown. Transient receptor potential (TRP) channels and Na + /Ca 2+ exchangers (NCX) are plasma membrane proteins that play prominent roles in controlling [Ca 2+ ] cyt homeostasis in normal mammalian cells, but little is known regarding their roles in the regulation of [Ca 2+ ] cyt in pancreatic cancer cells and pancreatic cancer development. Expression and function of NCX1 and TRPC1 proteins were characterized in BxPc3 pancreatic cancer cells. TGF-β induced both intracellular Ca 2+ release and extracellular Ca 2+ entry in these cells; however, 2-aminoethoxydiphenyl borate [2-APB; a blocker for both inositol 1,4,5-trisphosphate (IP 3 ) receptor and TRPC], LaCl 3 (a selective TRPC blocker), or KB-R7943 (a selective inhibitor for the Ca 2+ entry mode of NCX) markedly inhibited the TGF-β-induced increase in [Ca 2+ ] cyt . 2-APB or KB-R7943 treatment was able to dose-dependently reverse membrane translocation of PKCα induced by TGF-β. Transfection with small interfering RNA (siRNA) against NCX1 almost completely abolished NCX1 expression in BxPc3 cells and also inhibited PKCα serine phosphorylation induced by TGF-β. Knockdown of NCX1 or TRPC1 by specific siRNA transfection reversed TGF-β-induced pancreatic cancer cell motility. Therefore, TGF-β induces Ca 2+ entry likely via TRPC1 and NCX1 and raises [Ca 2+ ] cyt in pancreatic cancer cells, which is essential for PKCα activation and subsequent tumor cell invasion. Our data suggest that TRPC1 and NCX1 may be among the potential therapeutic targets for pancreatic cancer.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    URL: Article
    DOI: 10.1152/ajpcell.00242.2010
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2010
    detail.hit.zdb_id: 1477334-X
    SSG: 12
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