Journal of Neuroscience, Vol 5, 2672-2676, Copyright © 1985 by Society for Neuroscience
Calcium/phosphatidylserine/diacylglycerol-dependent protein phosphorylation in the Aplysia nervous system
SA DeRiemer, P Greengard and LK Kaczmarek
It has been shown that intracellular injection of protein kinase C
(calcium/phosphatidylserine/diacylglycerol-dependent protein kinase),
purified from mammalian brain, or application of the tumor-promoting
phorbol diester, 12-O-tetradecanoyl-13-phorbol acetate (TPA), leads to an
enhancement of calcium currents in the bag cell neurons of Aplysia. We now
present evidence of an endogenous enzyme in bag cell neurons which is
activated by TPA and which has properties similar to those of mammalian
protein kinase C. Calcium/phosphatidylserine/diacylglycerol- dependent
protein kinase activity was found in both cytosolic and particulate
fractions prepared from isolated clusters of bag cell neurons. This
endogenous enzyme phosphorylated an 87,000-dalton protein from bovine
brain, which appears to be a specific substrate for protein kinase C, as
well as several substrates present in cytosolic fractions prepared from
isolated bag cell clusters. Similar results were obtained using
preparations made from pooled head ganglia from Aplysia. The
pharmacological properties of the
calcium/phosphatidylserine/diacylglycerol-dependent protein kinase activity
in the Aplysia nervous system were similar to those of protein kinase C
from mammalian tissues. Thus, the same group of endogenous substrate
proteins were phosphorylated when diacylglycerol was replaced by TPA in
cytosolic fractions prepared from isolated bag cell clusters.
Non-tumor-promoting phorbols (4-alpha-phorbol, 4-alpha-phorbol-12,13-
didecanoate, and 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate) did not
stimulate protein phosphorylation in these preparations. Phosphorylation by
the Aplysia calcium/phosphatidylserine/diacylglycerol-dependent protein
kinase was inhibited by polymixin B sulfate, by calmodulin, and by the
"calmodulin antagonists" trifluoperazine, calmidazolium and W7.(ABSTRACT
TRUNCATED AT 250 WORDS)