Possible involvement of a phosphatidylinositol-type signaling pathway in glucose-induced activation of plasma membrane H +-ATPase and cellular proton extrusion in the yeast Saccharomyces cerevisiae

Abstract

Addition of glucose to cells of the yeast Saccharomyces cerevisiae causes rapid activation of plasma membrane H +-ATPase and a stimulation of cellular H + extrusion. We show that addition of diacylglycerol and other activators of protein kinase C to intact cells also activates the H +-ATPase and causes at the same time a stimulation of H + extrusion from the cells. Both effects are reversed by addition of staurosporine, a protein kinase C inhibitor. Addition of staurosporine or calmidazolium, an inhibitor of Ca 2+/calmodulin-dependent protein kinases, separately, causes a partial inhibition of glucose-induced H +-ATPase activation and stimulation of cellular H + extrusion; together they cause a more potent inhibition. Addition of neomycin, which complexes with phosphatidylinositol 4,5-bisphosphate, or addition of compound 48 80 , a phospholipase C inhibitor, also causes near complete inhibition. Diacylglycerol and other protein kinase C activators had no effect on the activity of the K +-uptake system and the activity of trehalase and glucose-induced activation of the K +-uptake system and trehalase was not inhibited by neomycin, supporting the specificity of the effects observed on the H +-ATPase. The results support a model in which glucose-induced activation of H +-ATPase is mediated by a phosphatidylinositol-type signaling pathway triggering phosphorylation of the enzyme both by protein kinase C and one or more Ca 2+/calmodulin-dependent protein kinases.