A CDC25 family protein phosphatase gates cargo recognition by the Vps26 retromer subunit.

We describe a regulatory mechanism that controls the activity of retromer, an evolutionarily conserved sorting device that orchestrates cargo export from the endosome. A spontaneously arising mutation that activates the yeast ( Saccharomyces cerevisiae ) CDC25 family phosphatase, Mih1, results in accelerated turnover of a subset of endocytosed plasma membrane proteins due to deficient sorting into a retromer-mediated recycling pathway. Mih1 directly modulates the phosphorylation state of the Vps26 retromer subunit; mutations engineered to mimic these states modulate the binding affinities of Vps26 for a retromer cargo, resulting in corresponding changes in cargo sorting at the endosome. The results suggest that a phosphorylation-based gating mechanism controls cargo selection by yeast retromer, and they establish a functional precedent for CDC25 protein phosphatases that lies outside of their canonical role in regulating cell cycle progression.