Down regulation of the α-factor pheromone receptor in S. cerevisiae

Abstract

The peptide pheromone, α-factor, was found to elicit down regulation of receptor sites on yeast a cell targets. Cellular uptake of α-factor accompanied the loss of receptor sites. Receptor-deficient a cells bearing a deletion of teh STE2 gene were unable to internalize α-factor. Cultures were found to reaccumulate receptor sites following the initial period of down regulation; reaccumulation was dependent upon protein synthesis. Pheromone-resistant mutants, ste4-3 and ste5-3, retained the ability to down regulate receptors but failed to show reaccumulation. Our results suggest that α-factor-receptor complexes enter the cell by receptor-mediated endocytosis and that receptors are continuously lost and resynthesized in the presence of α-factor. We found no reduction of α-factor binding capacity in a cell cultures that had adapted to α-factor.