Degradation of poly-phosphoinositides in brain subcellular membranes in response to decapitation insult.
Although it has been well demonstrated that decapitation insult results in a rapid breakdown of the poly-phosphoinositides in brain, the subcellular site(s) for this event has not been examined in detail. Using rats that were injected intracerebrally with (32)Pi to label the brain membrane phosphoinositides, decapitation treatment (0.5, 1.5 and 3.5 min) resulted in a decrease in labeled phosphatidylinositol 4,5-bisphosphates and phosphatidylinositol 4-phosphates in almost all subcellular fractions except myelin. However, the fractions exhibiting the most changes were synaptic vesicles, synaptic plasma membranes and the non-synaptic plasma membranes. The rapid response of poly-phosphoinositides in synaptic vesicles towards decapitation insult demonstrated a role of these phospholipids in vesicular membrane function. Besides the decrease in labeled phosphatidylinositol 4,5-bisphosphates which is attributed mainly to the action of phospholipase C, decapitation insult also elicited a near parallel decrease in labeled phosphatidylinositol 4-phosphates, and this was accompanied by a concomitant increase in labeled phosphatidylinositol which was observed mainly in the synaptic vesicles and synaptic plasma membrane fractions. This latter event suggests that besides degradation of phosphatidylinositol 4,5-bisphosphates by phospholipase C, some phosphatidylinositol 4-phosphates may have been degraded through the phosphomonoesterase pathway.
Sun
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Sinclair Comparative Research Farm and Biochemistry Department, University of Missouri, Columbia, MO 65203, U.S.A.
Yoa
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Lin
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