Investigating the Effects of Gpa2 Phosphorylation on Yeast Sporulation

Gpa2 is a G alpha protein in budding yeast, Saccharomyces cerevisiae, that functions in the nutrient signaling pathway. In diploid yeast cells, Gpa2 interacts with the cytoplasmic protein Ime2 and acts as an inhibitor to prevent Ime2 from inappropriate activation of sporulation. It is unclear how the inhibitory effect of Gpa2 on Ime2 is regulated. Recently, we found that Gpa2 undergoes phosphorylation and that its level of phosphorylation increases upon nitrogen starvation, a condition that triggers sporulation in yeast. Interestingly, phosphorylation enhances plasma membrane localization of Gpa2, raising the possibility that Gpa2 phosphorylation may play a role in the regulation of yeast sporulation. Accordingly, we investigated the sporulation efficiency of diploid cells that express either wild type Gpa2 or Gpa2‐10SA mutant, which lacks 10 serine residues required for phosphorylation. Using confocal microscopy to analyze the cells with clear indicators of the presence of spores, we found that more cells expressing wild type Gpa2 underwent sporulation than cells expressing Gpa2‐10SA mutant did. Our findings suggest that regulated phosphorylation of Gpa2 is a potential mechanism that relieves the inhibitory effect of Gpa2 on Ime2.Support or Funding InformationKnoedler Undergraduate Fund from Saint Louis University