Modulation of Phospholipase A2 Lytic Activity by Actin and Myosin

Prostacylin PGI2 productions closely coupled with endothelial cell shape and F-actin distribution in vitro. These findings may implicate cytoskeletal constituents in a mechanism regulating eicosanoid metabolism. To determine the potential for such a regulatory mechanism, cytoskeletal protein effects on the rate-limiting eicosanoid cascade enzyme phospholipase A2, PLA2 were studied. Membrane phospholipid degradation was indirectly determined by spectrophotometric measurement of PLA 2 induced rat red blood cell ghost RBC-G hemolysis. PLA 2 was incubated with actin skeletal, smooth, or non-muscle cell at a non-muscle cell concentration 100 micromoles and then exposed to the RBC-G Comparisons in the presence or absence of actin revealed that F-actin stimulated whereas G-action suppressed PLA2 lytic behavior significantly P 0.05. When a 10 or 100 1 F-actin to myosin-ratio was used, the F-actin stimulatory effect was significantly P0.05 reduced. These finding s suggest that the in vitro correlation between PGI 2 production and endothelial cell shape may be the result of PLA 2 regulation by cytoskeletal elements that impart cellular form.