Pep12 is important for proteasome microautophagy under low glucose conditions.

Autophagic degradation of proteasomes is a highly conserved mechanism for regulating proteasome homeostasis in eukaryotes. Here we show that Pep12, a t-SNARE protein, is important for intralumenal vesicle formation in the vacuole and proteasome microautophagy under low glucose conditions. Deleting PEP12 in yeast cells, Saccharomyces cerevisiae , blocked proteasome fragmentation, by which the ESCRT-dependent microautophagy selectively degrades aberrant proteasomes. Accumulation of aberrant proteasomes interfered with proteasome condensate formation in pep12∆ cells. Autophagic bodies were present, but intralumenal vesicles and proteasome microautophagy were absent in the vacuole of pep12∆ cells. Therefore, Pep12 plays an important role in proteasome microautophagy.