Proteasome storage granules protect proteasomes from autophagic degradation upon carbon starvation
Abstract
26S proteasome abundance is tightly regulated at multiple levels, including the elimination of excess or inactive particles by autophagy. In yeast, this proteaphagy occurs upon nitrogen starvation but not carbon starvation, which instead stimulates the rapid sequestration of proteasomes into cytoplasmic puncta termed proteasome storage granules (PSGs). Here, we show that PSGs help protect proteasomes from autophagic degradation. Both the core protease and regulatory particle sub-complexes are sequestered separately into PSGs via pathways dependent on the accessory proteins Blm10 and Spg5, respectively. Modulating PSG formation, either by perturbing cellular energy status or pH, or by genetically eliminating factors required for granule assembly, not only influences the rate of proteasome degradation, but also impacts cell viability upon recovery from carbon starvation. PSG formation and concomitant protection against proteaphagy also occurs in Arabidopsis, suggesting that PSGs represent an evolutionarily conserved cache of proteasomes that can be rapidly re-mobilized based on energy availability.
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Funding
U.S. Department of Energy (DE-FG02-88ER13968)
- Richard David Vierstra
National Science Foundation (IOS-1329956)
- Richard David Vierstra
National Institutes of Health (R01-GM124452-01A1)
- Richard David Vierstra
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2018, Marshall & Vierstra
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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