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Ca 2+ and Calmodulin‐Dependent Phosphorylation of Endogenous Synaptic Vesicle Tubulin by a Vesicle‐Bound Calmodulin Kinase System
Author(s) -
Burke Briant E.,
DeLorenzo Robert J.
Publication year - 1982
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.1471-4159.1982.tb07892.x
Subject(s) - synaptic vesicle , calmodulin , biology , microbiology and biotechnology , vesicle , tubulin , phosphorylation , biochemistry , protein kinase a , protein phosphorylation , microtubule , enzyme , membrane
Endogenous synaptic vesicle α‐and β‐tubulin were shown to be the major substrates for a Ca 2+ ‐calmodulin‐regulated protein kinase system in enriched synaptic vesicle preparations from rat cortex as determined by two‐dimensional gel electrophoresis and peptide mapping. The activation of this endogenous tubulin kinase system was dependent on Ca 2+ and the Ca 2+ binding protein, calmodulin. Under maximally stimulated conditions, approximately 40% of the tubulin present in enriched synaptic vesicles was phosphorylated within less than 50 s by the vesicle Ca 2+ ‐calmodulin kinase. Evidence is presented indicating that the Ca 2+ ‐calmodulin tubulin kinase is an enzyme system distinct from previously described cyclic AMP protein kinases. α‐Tubulin and β‐tubulin were identified as major components of previously designated vesicle phosphorylation bands DPH‐L and DPH‐M. The C a2+ ‐calmodulin tubulin kinase is very labile and specialized isolation procedures were necessary to retain activity. Ca 2+ ‐activated synaptic vesicle tubulin phosphorylation correlated with vesicle neurotransmitter release. Depolarization‐dependent Ca 2+ uptake in intact synaptosomes simultaneously stimulated the release of neurotransmitters and the phosphorylation of synaptic vesicle α‐and β‐tubulin. The results indicate that regulation of the synaptic vesicle tubulin kinase by Ca 2+ and calmodulin may play a role in the functional utilization of synaptic vesicle tubulin and may mediate some of the effects of Ca 2+ on vesicle function and neurosecretion.