A protein quality control pathway at the mitochondrial outer membrane.


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Authors
Metzger, Meredith B  ORCID logo  https://orcid.org/0000-0002-6248-0009
Scales, Jessica L 
Dunklebarger, Mitchell F 
Loncarek, Jadranka 
Abstract

Maintaining the essential functions of mitochondria requires mechanisms to recognize and remove misfolded proteins. However, quality control (QC) pathways for misfolded mitochondrial proteins remain poorly defined. Here, we establish temperature-sensitive (ts-) peripheral mitochondrial outer membrane (MOM) proteins as novel model QC substrates in Saccharomyces cerevisiae. The ts- proteins sen2-1HAts and sam35-2HAts are degraded from the MOM by the ubiquitin-proteasome system. Ubiquitination of sen2-1HAts is mediated by the ubiquitin ligase (E3) Ubr1, while sam35-2HAts is ubiquitinated primarily by San1. Mitochondria-associated degradation (MAD) of both substrates requires the SSA family of Hsp70s and the Hsp40 Sis1, providing the first evidence for chaperone involvement in MAD. In addition to a role for the Cdc48-Npl4-Ufd1 AAA-ATPase complex, Doa1 and a mitochondrial pool of the transmembrane Cdc48 adaptor, Ubx2, are implicated in their degradation. This study reveals a unique QC pathway comprised of a combination of cytosolic and mitochondrial factors that distinguish it from other cellular QC pathways.

Description
Keywords
MAD, S. cerevisiae, UPS, cell biology, misfolded, quality control, yeast, Cytosol, Intracellular Membranes, Mitochondrial Proteins, Molecular Chaperones, Proteasome Endopeptidase Complex, Protein Binding, Protein Transport, Proteolysis, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Temperature, Ubiquitin, Ubiquitin-Protein Ligases
Journal Title
Elife
Conference Name
Journal ISSN
2050-084X
2050-084X
Volume Title
9
Publisher
eLife Sciences Publications, Ltd
Sponsorship
National Cancer Institute (Intramural Research Program)