Control of cyclic adenosine 3',5'-monophosphate levels by depolarizing agents in fungi

Abstract

Diverse treatments which depolarize the plasma membrane of Neurospora crassa produce rapid increases in cyclic[c]AMP levels. Membrane active antibiotics, which are known or putative depolarizing agents, produced similar cAMP increases in N. crassa and in the distantly related fungi Saccharomyces cerevisiae and Mucor racemosus. Uncouplers of oxidative phosphorylation, which depolarized Neurospora, produced cAMP increases in all 3 fungi. The time course of the cAMP response to these various treatments was similar in all 3 fungi. The fungal studies and studies on depolarized central nervous tissue suggest that cAMP increases may be produced in response to plasma membrane depolarization in diverse eukaryotic cells. A model is proposed for eukaryotic microorganisms in which membrane depolarization serves as a signal of breakdown of the plasma membrane integrity. The subsequent cAMP increase may mediate cellular response to help protect the plasma membrane from chemical and mechanical threats to its integrity.