ABSTRACT

Ergosterol Depletion Leads to Reduced Ste2p Activity in Saccharomyces cereviseae
Nicole Billings and Amanda Dalton, Tennessee Wesleyan College

Ste2p is a highly characterized G-protein coupled receptor that mediates mating between haploid yeast cells. Receptor activation initiates a signal transduction pathway leading to nuclear fusion between yeast cells of opposing mating types. In this study, we have looked at the function of ergosterol in Ste2p activity. Ergosterol levels were reduced by treating cells with ketoconazole, an azole antifungal agent known to inhibit oxisterol synthesis. Previously studies indicated that reduction of ergosterol levels resulted in a change in Ste2p activity, resulting in reduced binding capacity for the pheromone and increased growth inhibition after exposure to pheromone. In this study, we observed that ergosterol depletion resulted in a significant reduction in mating projection (shmoo) formation. In addition, proteolytic cleavage of Ste2p in ergosterol-depleted cells indicated a conformational change in the receptor, offering an explanation for altered receptor function.