Ca2+-dependent inactivation of a store-operated Ca2+ current in human submandibular gland cells. Role of a staurosporine-sensitive protein kinase and the intracellular Ca2+ pump.
Stimulation of human submandibular gland cells with carbachol, inositol trisphosphate (IP3), thapsigargin, or tert-butylhydroxyquinone induced an inward current that was sensitive to external Ca2+ concentration ([Ca2+]e) and was also carried by external Na+ or Ba2+ (in a Ca2+-free medium) with amplitudes in the order Ca2+ > Ba2+ > Na+. All cation currents were blocked by La3+ and Gd3+ but not by Zn2+. The IP3-stimulated current with 10 microM 3-deoxy-3-fluoro-D-myo-inositol 1,4,5-triphosphate and 10 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid in the pipette solution, showed 50% inactivation in <5 min and >5 min with 10 and 1 mM [Ca2+]e, respectively. The Na+ current was not inactivated, whereas the Ba2+ current inactivated at a slower rate. The protein kinase inhibitor, staurosporine, delayed the inactivation and increased the amplitude of the current, whereas the protein Ser/Thr phosphatase inhibitor, calyculin A, reduced the current. Thapsigargin- and tert-butylhydroxyquinone-stimulated Ca2+ currents inactivated faster. Importantly, these agents accelerated the inactivation of the IP3-stimulated current. The data demonstrate that internal Ca2+ store depletion-activated Ca2+ current (ISOC) in this salivary cell line is regulated by a Ca2+-dependent feedback mechanism involving a staurosporine-sensitive protein kinase and the intracellular Ca2+ pump. We suggest that the Ca2+ pump modulates ISOC by regulating [Ca2+]i in the region of Ca2+ influx.
Liu
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Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDR, National Institutes of Health, Bethesda, Maryland 20892, USA.
O'Connell
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Ambudkar
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IS
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005246:Feedback; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology*; D013363:Submandibular Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D006873:Hydroquinones; D047428:Protein Kinase Inhibitors; D019284:Thapsigargin; D011494:Protein Kinases; D000252:Calcium-Transporting ATPases; D019311:Staurosporine; D002118:Calcium