Requirement of Endoplasmic Reticulum-shaping Poroteins for PMN Vesicle Formation during Piecemeal Microautophagy of the Nucleus

Abstract

Autophagy occurs to prevent nutritional deficiencies and accumulation of unnecessary substances in cells. Piecemeal microautophagy of nucleus (PMN), a special type of autophagy in Saccharomyces cerevisiae, occurs in the nucleus-vacuole junction (NVJ). PMN occurs as a process in which the perinuclear ER membrane fuses with the vacuole to form double membrane vesicles, which requires ER membrane curvature generation, fusion, and fission. However, ER proteins involved in these processes have not been identified. In this study, to identify which proteins are involved in the formation of PMN vesicles, I deleted a series of genes encoding proteins involved in shaping the ER and analyzed whether the deletion impaired the formation of PMN vesicles. PMN vesicle formation was markedly reduced in yeast cells in which SEY1, LNP1, or RTN1 was deleted. Taken together, the ER-shaping proteins Sey1p, Lnp1p, and Rtn1p are involved in PMN vesicle formation.