The guanine nucleotide exchange factor Gea1 rescues an isoform-specific 14-3-3 phenotype

14-3-3 proteins are abundant modulators of cellular processes, in particular signal transduction. They function by binding to a broad spectrum of client proteins, thus affecting client protein localisation or function[1]Gardino 2011 [1]Morrison 2009 [2][2]. Animals and plants express 14-3-3 proteins encoded by several genes, which has made it difficult to study their unique rather than shared functions. The yeast Saccharomyces cerevisiae possesses only two highly homologous 14-3-3 genes, BMH1 and BMH2. Using this model system we now uncover novel aspects of functional specificity between the two yeast 14-3-3s. We show that bmh1 but not bmh2 cells display an altered morphology of the endomembrane system and specific trafficking defects under glucose starvation. This but not a second phenotype specific to the bmh1 strain, that is, the accumulation of glycogen, was rescued by overexpression of the nucleotide exchange factor Gea1, suggesting a role for Bmh1 in Gea1’s function or regulation.