ENHANCEMENT OF STRESS-INDUCED SYNTHESIS OF STRESS PROTEINS BY MASTOPARAN IN C6 RAT GLIOMA-CELLS

The levels of two small stress proteins, hsp27 and alphaB crystallin, were low in C6 glioma cells confluency, However, the levels of the two proteins increased after exposure of cells to heat (42 degrees C for 30 min) or arsenite (50-100 mu M for 1 h) stress, When cells were expo sed to arsenite or heat in the presence of mastoparan, a peptide toxin from wasp venom, the induction of hsp27 and alphaB crystallin was mar kedly stimulated, as detected by means of specific immunoassays, Weste rn blot analysis, and Northern blot analysis. The response of hsp70 to each stress was also enhanced in the presence of mastoparan, Treatmen t of cells with 40 mu M mastoparan alone barely induced the accumulati on of hsp27 and alphaB crystallin. The stimulatory effect of mastopara n was little affected in cells that had been treated with pertussis to xin, but it was strongly suppressed in the presence of quinacrine, an inhibitor of phospholipase A(2). These results suggest that mastoparan , which is an activator of phospholipase A(2), enhances the responses to stress of hsp27, alphaB crystallin and hsp70 by increasing the meta bolic activity of the arachidonic acid cascade.