Pbs2 regulates late-stage macroautophagy in Saccharomyces cerevisiae

Autophagy is crucial for maintaining cellular homeostasis and is linked to various diseases. In Saccharomyces cerevisiae, the Polymyxin B Sensitivity 2 (Pbs2) protein is a member of the mitogen-activated protein kinase (MAPK) family and plays a role in mitophagy. To explore the potential role of Pbs2 in macroautophagy, we engineered wild-type and PBS2-deficient cells using plasmid construction and yeast transformation techniques, followed by a series of autophagy assays. First, after nitrogen starvation, the levels of autophagic activity were evaluated with the classical GFP-Atg8 cleavage assay and the Pho8Δ60 activity assay at different time points. Deleting PBS2 significantly decreased both GFP-Atg8 protein cleavage and Pho8Δ60 activity, indicating that Pbs2 is essential for macroautophagy. Furthermore, the influence of Pbs2 on macroautophagy was shown to be independent of Hog1, a well-known downstream factor of Pbs2. Second, the Atg8 lipidation assay demonstrated that Atg8 lipidation levels increased upon PBS2 deletion, suggesting that Pbs2 acts after Atg8 lipidation. Third, the proteinase K protection assay indicated that the loss of PBS2 led to a higher proportion of closed autophagosomes, implying that Pbs2 impacts the later stages of macroautophagy following autophagosome closure. In conclusion, Pbs2 regulates the late stages of macroautophagy induced by nitrogen starvation.