The <i>S. pombe</i> CDK5 ortholog Pef1 regulates sexual differentiation through control of the TORC1 pathway and autophagy

Abstract

In <i>Schizosaccharomyces pombe</i>, a general strategy for survival in response to environmental changes is sexual differentiation, which is triggered by TORC1 inactivation. However, mechanisms of TORC1 regulation in fission yeast remain poorly understood. In this study, we found that Pef1, which is an ortholog of mammalian CDK5, regulates the initiation of sexual differentiation through positive regulation of TORC1 activity. Conversely, deletion of <i>pef1</i> leads to activation of autophagy and subsequent excessive TORC1 reactivation during the early phases of the nitrogen starvation response. This excessive TORC1 reactivation results in the silencing of the Ste11-Mei2 pathway and mating defects. Additionally, we found that <i>pef1</i> genetically interacts with <i>tsc1</i> and <i>tsc2</i> for TORC1 regulation, and physically interacts with three cyclins, Clg1, Pas1 and Psl1. The double deletion of <i>clg1</i> and <i>pas1</i> promotes activation of autophagy and TORC1 during nitrogen starvation, similar to what is seen in <i>pef1Δ</i> cells. Overall, our work suggests that Pef1-Clg1 and Pef1-Pas1 complexes regulate initiation of sexual differentiation through control of the TSC-TORC1 pathway and autophagy.