ATP-dependent activation of K(Ca) and ROMK-type K(ATP) channels in human submandibular gland ductal cells.
[Ca(2+)](i) and membrane current were measured in human submandibular gland ductal (HSG) cells to determine the regulation of salivary cell function by ATP. 1-10 microM ATP activated internal Ca(2+) release, outward Ca(2+)-dependent K(+) channel (K(Ca)), and inward store-operated Ca(2+) current (I(SOC)). The subsequent addition of 100 microM ATP activated an inwardly rectifying K(+) current, without increasing [Ca(2+)](i). The K(+) current was also stimulated by ATP in cells treated with thapsigargin in a Ca(2+)-free medium and was blocked by glibenclamide and tolbutamide, but not by charybdotoxin. This suggests the involvement of a Ca(2+)-independent, sulfonylurea-sensitive K(+) channel (K(ATP)). UTP mimicked the low [ATP] effects, while benzoyl-ATP activated internal Ca(2+) release, a Ca(2+) influx pathway, and K(Ca). Thus, ATP acts via P(2U) (P2Y(2)) and P(2Z) (P2X(7)) receptors to increase [Ca(2+)](i) and activate K(Ca), but not K(ATP). Importantly, (i) ROMK1 and the cystic fibrosis transmembrane regulator protein (but not SUR1, SUR2A, or SUR2B) and (ii) cAMP-stimulated Cl(-) and K(+) currents were detected in HSG cells. These data demonstrate for the first time that a ROMK-type K(ATP) channel is present in salivary gland duct cells that is regulated by extracellular ATP and possibly by the cystic fibrosis transmembrane regulator. This reveals a potentially novel mechanism for K(+) secretion in these cells.
Liu
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Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA.
Singh
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Ambudkar
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D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013363:Submandibular Gland / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
C505032:CFTR protein, human; C086989:KCNJ1 protein, human; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D018999:Charybdotoxin; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D019284:Thapsigargin; D007811:Lanthanum; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D000242:Cyclic AMP; D002118:Calcium; D014544:Uridine Triphosphate