Journal of Dental Research, Vol 65, 1057-1063, Copyright © 1986 by International & American Associations for Dental Research Online Journals
Exocytosis in rat parotid acini after in vitro treatment with forskolin is accompanied by cellular redistribution of regulatory subunits of cyclic AMP-dependent protein kinase
M. I. Mednieks, L. F. Cheng and A. R. Hand
Incubation of rat parotid acinar tissue with 1 mumol/L forskolin resulted
in progressive exocytosis which was virtually complete after a 30-minute
incubation period. Cyclic AMP binding to protein kinase (cA-PK) regulatory
(R) subunits, determined by photo-affinity labeling with [32P]-8-azido
cyclic AMP, was found to increase in a time-dependent manner in the
10,000-g supernatant fraction of a broken cell preparation. An apparent
redistribution of protein kinase R subunits took place in the 600-g
supernatant after in vitro treatment of cells with forskolin. In control
cells, RI and RII subunits and a 35-to-40-kdal fragment were present in
approximately equal amounts throughout the incubation. Azido labeling of
RII appeared either to increase or to remain unchanged, while that of RI
decreased in the 600-g pellet. Only type I isozyme R subunits were found in
the 600-g pellet in either the absence or presence of forskolin. These
finding indicate that a temporal relationship exists between stimulated
protein exocytosis and cyclic AMP-dependent protein kinase activation.
Forskolin stimulation of adenylate cyclase in salivary gland cells
therefore provides a defined system for the study of cyclic AMP-mediated
protein secretion.
