J Biol Chem, Vol. 274, Issue 48, 34036-34044, November 26, 1999
Lipid-dependent Activation of Protein Kinase C-
by
Normal Alcohols
Yu-Ming A.
Shen,
Olga I.
Chertihin,
Rodney L.
Biltonen, and
Julianne J.
Sando
From the Department of Pharmacology and the Biophysics Program and
the Cancer Center, The University of Virginia Health Sciences Center,
Charlottesville, Virginia 22903
Significant stimulation of protein kinase C-
(PKC
) by n-alcohols was observed in characterized lipid systems
composed of phosphatidylcholine/phosphatidylserine/dioleoylglycerol
(PC/PS/DO). The logarithm of the alcohol concentrations to achieve
half-maximal PKC stimulation (ED50) and of the
maximal PKC stimulation by alcohols were both linear functions of
alcohol chain length, consistent with the Meyer-Overton effect. Binding
of phorbol esters to PKC was not significantly affected by octanol.
Octanol increased, up to 4-fold, the affinity of PKC binding to the
lipid bilayers in both the absence and presence of DO. However, octanol
increased PKC activity much more significantly than it enhanced binding of the enzyme to the lipid bilayers, suggesting that the stimulation of
PKC is not merely a reflection of the increase in PKC bilayer binding
affinity. 31P NMR experiments did not reveal formation of
non-lamellar phases with octanol. Differential scanning calorimetry
suggested that alcohols, like diacylglycerol, induce formation of
compositionally distinct domains and the maximal enzyme activity with
alcohol resided roughly in the putative domain-coexistence region.
These results suggest that alcohols are mimicking diacylglycerol in activating PKC, not by binding to the high affinity phorbol ester binding site, but by altering lipid structure and by enhancing PKC-bilayer binding.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.