The TORC1-Nem1/Spo7-Pah1/lipin axis regulates microautophagy induction in budding yeast.

Nutrient starvation and inactivation of target of rapamycin complex 1 (TORC1) protein kinase promotes macroautophagy. Macroautophagy is a lipid-consuming process, and Nem1/Spo7 protein phosphatase and Pah1/lipin phosphatidate phosphatase are activated after TORC1 inactivation, supporting macroautophagy induction in the budding yeast Saccharomyces cerevisiae. On the other hand, whether and how microautophagy, which also consumes lipids, is regulated by TORC1 is controversial. Here we show that TORC1 inactivation induces microautophagy in budding yeast. Vps27, but not Atg1, Atg7, or Atg8, was required for TORC1 inactivation-induced microautophagy. Furthermore, the Nem1/Spo7–Pah1 axis was also critical for microautophagy induction. Thus, the TORC1–Nem1/Spo7–Pah1 axis is a master regulator of not only macroautophagy but also microautophagy in budding yeast.