Role for protein phosphatase in the regulation of ca2+ influx in
parotid gland acinar cells.
Sakai, Takayuki, and Indu S. Ambudkar.
Secretory Physiology Section, Clinical Investigations and Patient
Care Branch, National Institute of Dental Research, National
Institutes of Health, Bethesda MD 20892
APStracts 3:0052C, 1996.
Stimulation of Ca2+ (and Mn2+) entry in salivary epithelial cells by
carbachol, or thapsigargin, is mediated by an, as yet, unknown
mechanism which 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+ stores(s) (achieved by
incubation with either carbachol or thapsigargin in Ca2+-free
medium). Treatment of cells with phorbol myristate, H-7, 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 K252a, 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.
Received 9 June 1995; accepted in final form 16 January 1996.
APS Manuscript Number C324-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 14 February 96