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Differential Regulation by Calmodulin of Basal, GTP‐, and Dopamine‐Stimulated Adenylate Cyclase Activities in Bovine Striatum
Author(s) -
Harrison Jeffrey K.,
Mickevicius Cynthia K.,
Gnegy Margaret E.
Publication year - 1988
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.1471-4159.1988.tb01045.x
Subject(s) - calmodulin , cyclase , gtp' , adenylate kinase , egta , endocrinology , medicine , long term potentiation , biology , chemistry , biochemistry , stimulation , calcium , receptor , enzyme
The concentration requirements of calmodulin in altering basal, GTP‐, and dopamine‐stimulated adenylate cyclase activities in an EGTA‐washed paniculate fraction from bovine striatum were examined. In the bovine striatal paniculate fraction, calmodulin activated basal adenylate cyclase activity 3.5‐fold, with an EC 50 of 110 n M . Calmodulin also potentiated the activation of adenylate cyclase by GTP by decreasing the EC 50 for GTP from 303 ± 56 n M to 60 ± 10 n M Calmodulin did not alter the maximal response to GTP. The EC 50 for calmodulin in potentiating the GTP response was only 11 n M as compared to 110 n M for activation of basal activity. Similarly, calmodulin increased the maximal stimulation of adenylate cyclase by dopamine by 50–60%. The EC 50 for calmodulin in eliciting this response was 35 n M . These data demonstrate that calmodulin can both activate basal adenylate cyclase and potentiate adenylate cyclase activities that involve the activating GTP‐binding protein, N s . Mechanisms that involve potentiation of N s ‐mediated effects are much more sensitive to calmodulin than is the activation of basal adenylate cyclase activity. Potentiation of GTP‐stimulated adenylate cyclase activity by calmodulin was apparent at 3 and 5 m M MgCl 2 , but not at 1 or 10 m M MgCl 2 . These data further support a role for calmodulin in hormonal signalling and suggest that calmodulin can regulate cyclic AMP formation by more than one mechanism.