J. Biol. Chem., Vol. 261, Issue 23, 10493-10495, 08, 1986
Phorbol 12,13-dibutyrate and 1-oleyl-2-acetyldiacylglycerol stimulate inositol trisphosphate dephosphorylation in human platelets
LM Molina y Vedia and EG Lapetina
Inositol trisphosphate (IP3) is formed in response to specific agonists
that cause activation of phospholipase C and degradation of
phosphatidylinositol bisphosphate. IP3 is a second messenger that releases
Ca2+ from the dense tubular system to the cytosol in stimulated platelets.
Our present information indicates that [3H]IP3 is dephosphorylated to
[3H]inositol bisphosphate (IP2) and [3H]inositol monophosphate (IP) by
human platelets treated with 0.05-0.10% Triton X- 100. This
dephosphorylation of [3H]IP3 to [3H]IP2 and [3H]IP is also observed when
platelets are permeabilized by electrical stimulation or by 20
micrograms/ml saponin. These detergents or electropermeabilization allow
IP3 to access cytosolic IP3 phosphatase. Pretreatment of intact platelets
with phorbol dibutyrate and 1-oleyl-2- acetyldiacylglycerol for 30 s, at
concentrations that maximally activate protein kinase C, stimulates the
conversion of IP3 to IP2 and IP. This suggests a role for protein kinase C
in the regulation of IP3 degradation.