Protein kinase C enhances exocytosis from chromaffin cells by increasing the size of the readily releasable pool of secretory granules.
We have used membrane capacitance measurements to assay Ca2+-triggered exocytosis in single bovine adrenal chromatin cells. Brief application of phorbol ester (PMA) enhances depolarization-evoked exocytosis severalfold while actually decreasing the Ca2+ current. Ca2+ metabolism is unchanged. Three different protocols were used to show that PMA increases the size of the readily releasable pool of secretory granules. PMA treatment leads to a large increase in amplitude, but little change in the time course of the exocytic burst that results from rapid elevation of [Ca2+]i upon photolysis of DMI-Nitrophen. Thus, PKC appears to affect a late step in secretion but not the Ca2+ sensitivity of the final step.
Gillis
K D
KD
Department of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Federal Republic of Germany.
Mossner
R
R
Neher
E
E
D000818:Animals; D002118:Calcium / Q000502:physiology; D002417:Cattle; D002838:Chromaffin System / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology*
D011493:Protein Kinase C; D002118:Calcium