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Depolarization‐Induced Phosphorylation of the Protein Kinase C Substrate B‐50 (GAP‐43) in Rat Cortical Synaptosomes
Author(s) -
Dekker L. V.,
Graan P. N. E.,
Wit M.,
Hens J. J. H.,
Gispen W. H.
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb01217.x
Subject(s) - depolarization , phosphorylation , protein kinase c , staurosporine , biology , protein kinase a , protein phosphorylation , kinase , trifluoperazine , diacylglycerol kinase , extracellular , biophysics , biochemistry , calmodulin , chemistry , enzyme
We studied the molecular events underlying K + ‐induced phosphorylation of the neuron‐specific protein kinase C substrate B‐50. Rat cortical synaptosomes were prelabelled with 32 P‐labelled orthophosphate. B‐50 phosphorylation was measured by an immunoprecipitation assay. In this system, various phorbol esters, as well as a synthetic diacylglycerol derivative, enhance B‐50 phosphorylation. K + depolarization induces a transient enhancement of B‐50 phosphorylation, which is totally dependent on extracellular Ca 2+ . Also, the application of the Ca 2+ ionophore A23187 induces B‐50 phosphorylation, but the magnitude and kinetics of A23187‐induced B‐50 phosphorylation differ from those induced by depolarization. The protein kinase inhibitors 1‐(5‐isoquinolinylsulfonyl)‐2‐methylpiperazine (H‐7), N ‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide (W‐7), and staurosporine antagonize K + ‐ as well as PDB‐induced B‐50 phosphorylation, whereas trifluoperazine and calmidazolium are ineffective under both conditions. We suggest that elevation of the intracellular Ca 2+ level after depolarization is a trigger for activation of protein kinase C, which subsequently phosphorylates its substrate B‐50. This sequence of events could be of importance for the mechanism of depolarization‐induced transmitter release.