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Effects of ATP on Phosphatidylinositol‐Phospholipase C and Inositol 1‐Phosphate Accumulation in Rat Brain Synaptosomes
Author(s) -
Huang H.M.,
Sun G. Y.
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.tb02921.x
Subject(s) - inositol , phosphatidylinositol , phospholipase c , inositol phosphate , inositol trisphosphate , phospholipase , biochemistry , phosphate , sugar phosphates , synaptosome , chemistry , incubation , biology , enzyme , in vitro , receptor , signal transduction
Incubation of rat brain synaptosomes prelabeled with [2‐ 3 H]inositol resulted in a time‐dependent release of labeled inositol 1 ‐phosphate. This process was Ca 2+ dependent, and ATP (1 m M ) enhanced the inositol 1‐phosphate formation three‐ to fivefold. Using [l‐ 14 C]arachidonoyl‐phosphatidylinositol which was introduced into saponin‐permeabilized synaptosomes, ATP (1 m M ) and free Ca 2+ (˜20 μ M ) enhanced the phospholipase C hydrolysis of this substrate to form labeled diacylglycerol. When the same permeabilized synaptosomal preparation was incubated with [2‐ 3 H]inositol‐phosphatidylinositol, ATP not only enhanced the formation of labeled inositol 1‐phosphate, but also inhibited the conversion of inositol 1‐phosphate to inositol. Furthermore, ATP appeared to reduce the Ca 2+ requirement of the phosphatidylinositol‐phospholipase C. Inhibition of the conversion of inositol 1‐phosphate to inositol could not be overcome by increasing the Mg 2+ concentration in the incubation medium. Although the ATP effect is not viewed as a receptor‐mediated event, it is possible that such an event may occur in synaptosomes under conditions in which intrasynaptic Ca 2+ concentration becomes elevated.