Role for protein kinase in Ca2+-dependent feedback modulation of divalent cation influx in internal-Ca2+-store-depleted rat parotid gland cells.
Divalent cation (Ca2+ and Mn2+) influx, stimulated by internal Ca2+ store depletion, into rat parotid acinar cells is inhibited by conditions which increase protein phosphorylation [T. Sakai and I.S. Ambudkar (1996) Am J Physiol 271:C284-C294]. The present study examines the involvement of this protein phosphorylation and Ca2+ in the store-dependent inactivation of divalent cation entry. Internal Ca2+ store depletion, achieved by incubation (30 min) of cells in nominally Ca2+-free medium containing either carbachol or thapsigargin, stimulated Ca2+, and Mn2+, influx into cells. In either case, inclusion of 1.5 mM Ca2+ for the last 5 min of incubation resulted in a decrease in Ca2+ (33-41%) and Mn2+ (50%) influx, which could not be accounted for by internal Ca2+ store refill. The inhibition was prevented when internal-store-depleted cells were treated (prior to incubation with Ca2+) with either staurosporine or K-252a, but not with H-7 or KN-93. Refilling of internal Ca2+ store(s) in carbachol-treated cells (incubation with Ca2++atropine) induced complete inhibition of divalent cation influx, which was not prevented by treatment with protein kinase inhibitors. These data suggest the staurosporine-sensitive (and K-252a-sensitive) protein phosphorylation is not involved in Ca2+-store-refilling-dependent inactivation of Ca2+ influx but mediates a Ca2+-dependent feedback modulation of divalent cation influx in rat parotid gland acinar cells.
Sakai
T
T
Secretory Physiology Section, Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda MD 20892, USA.
Ambudkar
I S
IS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology*; D005246:Feedback / Q000187:drug effects / Q000502:physiology*; D017136:Ion Transport / Q000502:physiology; D008297:Male; D010306:Parotid Gland / Q000378:metabolism*; D011494:Protein Kinases / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D019284:Thapsigargin / Q000494:pharmacology
D002412:Cations; D019284:Thapsigargin; D011494:Protein Kinases; D002118:Calcium