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The activation of protein kinase C by the polyphosphoinositides phosphatidylinositol 4,5‐diphosphate and phosphatidylinositol 4‐monophosphate
Author(s) -
O'Brian Catherine A.,
Arthur W.Lane,
Weinstein I.Bernard
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)80083-2
Subject(s) - phosphatidylinositol , biochemistry , kinase , chemistry , microbiology and biotechnology , biology
Protein kinase C(PKC) is a Ca 2+ ‐ and phospholipid‐dependent protein kinase which can be activated by diacylglycerol, a product of polyphosphoinositide hydrolysis. In this report, we show that the polyphosphoinositides L‐α‐phosphatidylinositol 4‐monophosphate (PI 4P) and L‐α‐phosphatidylinositol 4,5‐diphosphate (PI 4,5DP) can serve as phospholipid cofactors of isolated rat brain PKC. The order of potency of the phosphoinositides in the activation of PKC, PI > PI 4P > PI 4,5DP, shows a negative correlation with the degree of acidity of the phospholipid head group, whether 1 mM Ca 2+ or 200 nM TPA is present in the reaction assay mixture. Although the polyphosphoinositides are by themselves weaker activators of PKC than PI, small amounts of PI 4,5DP cause a two‐fold enhancement of PKC in the presence of Ca 2+ and PI. While the endogenous phospholipid cofactors of PKC remain to be identified, these results suggest that the small amounts of polyphosphoinositides which are present in cell membranes may play a direct role in the activation of PKC in vivo, by serving as phospholipid cofactors of the enzyme.