Biology Commons^™

Proteasome Storage Granules Protect Proteasomes From Autophagic Degradation Upon Carbon Starvation, Richard S. Marshall, Richard D. Vierstra

Biology Faculty Publications & Presentations

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 …

Purification Of 26s Proteasomes And Their Subcomplexes From Plants, Richard S. Marshall, David C. Gemperline, Richard D. Vierstra

Biology Faculty Publications & Presentations

The 26S proteasome is a highly dynamic, multisubunit, ATP-dependent protease that plays a central role in cellular housekeeping and many aspects of plant growth and development by degrading aberrant polypeptides and key cellular regulators that are first modified by ubiquitin. Although the 26S proteasome was originally enriched from plants over 30 years ago, only recently have significant advances been made in our ability to isolate and study the plant particle. Here, we describe two robust methods for purifying the 26S proteasome and its subcomplexes from Arabidopsis thaliana; one that involves conventional chromatography techniques to isolate the complex from wild-type …

Autophagic Turnover Of Inactive 26s Proteasomes In Yeast Is Directed By The Ubiquitin Receptor Cue5 And The Hsp42 Chaperone, Richard S. Marshall, Fionn Mcloughlin, Richard D. Vierstra

Biology Faculty Publications & Presentations

Highlights

• The yeast 26S proteasome is degraded by Atg8-mediated autophagy
• Nitrogen starvation and inactivation stimulate proteaphagy via distinct pathways
• Proteasome inhibition is accompanied by extensive ubiquitylation of the complex
• Proteaphagy engages the Cue5 autophagy receptor and the Hsp42 chaperone

Summary

The autophagic clearance of 26S proteasomes (proteaphagy) is an important homeostatic mechanism within the ubiquitin system that modulates proteolytic capacity and eliminates damaged particles. Here, we define two proteaphagy routes in yeast that respond to either nitrogen starvation or particle inactivation. Whereas the core autophagic machineries required for Atg8 lipidation and vesiculation are essential for both routes, the upstream Atg1 …

Ubiquitin Goes Green, Zhihua Hua, Richard D. Vierstra

Biology Faculty Publications & Presentations

Chloroplasts depend on the nucleus for much of their proteome. Consequently, strong transcriptional coordination exists between the genomes, which is attuned to the developmental and physiological needs of the organelle. Recent studies highlight that the post-translational modifier ubiquitin adds another layer to plastid homeostasis and even helps eliminate damaged chloroplasts.