Role for protein phosphatase in the regulation of Ca2+ influx in parotid gland acinar cells.
Stimulation of Ca2+ (and Mn2+) entry in salivary epithelial cells by carbachol, or thapsigargin, is mediated by an, as yet, unknown mechanism that is dependent on the depletion of Ca2+ from intracellular Ca2+ stores. This study assesses the possible role of protein phosphorylation in the regulation of Ca2+ entry in rat parotid gland acinar cells. Treatment of cells with the protein phosphatase inhibitors okadaic acid, calyculin A, and pervanadate induced a dose-dependent inhibition of carbachol and thapsigargin stimulation of Ca2+ and Mn2+ entry. All three inhibitors decreased carbachol stimulation of internal Ca2+ release, which likely accounts for the inhibition of carbachol-stimulated Ca2+ entry. Thapsigargin-induced internal Ca2+ release was not affected by the treatments. Additionally, all three phosphatase inhibitors decreased Mn2+ entry into cells with depleted internal Ca2+ store(s) (achieved by incubation with either carbachol or thapsigargin in Ca2+-free medium). Treatment of cells with phorbol 12-myristate 13-acetate, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, or staurosporine did not affect divalent cation entry into unstimulated cells or thapsigargin treated cells. Importantly, when cells with depleted internal Ca2+ store(s) were pretreated with staurosporine, or K-252a, the inhibition of Ca2+ entry by calyculin A and okadaic acid, but not by pervanadate, was attenuated. Although the effect of pervanadate remains to be clarified, these results demonstrate a role for protein phosphorylation in the regulation of divalent cation influx in rat parotid acinar cells.
Sakai
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Secretory Physiology Section, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ambudkar
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D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000378:metabolism; D008387:Marine Toxins; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D047428:Protein Kinase Inhibitors; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical; D019284:Thapsigargin / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D047428:Protein Kinase Inhibitors; C076715:pervanadate; D019319:Okadaic Acid; D014638:Vanadates; D008345:Manganese; D019284:Thapsigargin; C059041:calyculin A; D002217:Carbachol; D010749:Phosphoprotein Phosphatases; D002118:Calcium