Active protein quality control in quiescence: involvement of proteasomes, autophagy, and nucleus-vacuole junctions.

Abstract

Quiescence is a conserved, reversible state of proliferative arrest, characterized by changes in cell physiology and metabolism. Many cells spend a considerable part of their lifetime in quiescence, including adult stem cells or microorganisms facing unfavorable environmental conditions. Cells can remain quiescent for long periods of time while retaining their viability and reproductive capacity, indicating a need to maintain protein homeostasis. Given the changes in intracellular organization, it has been unclear how protein quality control (PQC) functions in quiescent cells. In our recent study, we examined model misfolded proteins expressed in glucose-depleted quiescent yeast cells and found that quiescent cells maintain an active PQC that relies primarily on selective protein degradation, requiring the ubiquitin-proteasome system, intact nucleus-vacuole junctions and autophagy. Our results highlight the relevance of mitigating misfolded proteins in quiescence.