Genome-wide CRISPRi screening identifies OCIAD1 as a prohibitin client and regulatory determinant of mitochondrial Complex III assembly in human cells

• Published in: eLife 2021-05, Vol.10
• Main Authors: Le Vasseur, Maxence, Friedman, Jonathan, Jost, Marco, Xu, Jiawei, Yamada, Justin, Kampmann, Martin, Horlbeck, Max A, Salemi, Michelle R, Phinney, Brett S, Weissman, Jonathan S, Nunnari, Jodi
• Format: Article
• Language: English
• Subjects: Antigens; Antimycin A - pharmacology; Biosynthesis; Cell Biology; Cells; Clustered Regularly Interspaced Short Palindromic Repeats; Complex III; CRISPR-Associated Protein 9 - genetics; CRISPR-Associated Protein 9 - metabolism; CRISPR-Cas Systems; Cytochrome; Cytochrome b; Cytochrome c1; Electron transport; Electron transport chain; Electron Transport Complex III - antagonists & inhibitors; Electron Transport Complex III - genetics; Electron Transport Complex III - metabolism; Endopeptidases - genetics; Endopeptidases - metabolism; Genes; Genome-Wide Association Study; Genomes; Genomics; Genotype & phenotype; Humans; K562 Cells; Membrane proteins; Metabolism; Mitochondria; Mitochondria - drug effects; Mitochondria - enzymology; Mitochondria - genetics; Mitochondrial DNA; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Ontology; Ovarian cancer; Ovarian carcinoma; Ovaries; Oxidative Phosphorylation; Prohibitin; Prohibitins; protease; Proteins; Proteolysis; Quality control; Repressor Proteins - genetics; Repressor Proteins - metabolism
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.67624

Dysfunction of the mitochondrial electron transport chain (mETC) is a major cause of human mitochondrial diseases. To identify determinants of mETC function, we screened a genome-wide human CRISPRi library under oxidative metabolic conditions with selective inhibition of mitochondrial Complex III and identified ovarian carcinoma immunoreactive antigen (OCIA) domain-containing protein 1 (OCIAD1) as a Complex III assembly factor. We find that OCIAD1 is an inner mitochondrial membrane protein that forms a complex with supramolecular prohibitin assemblies. Our data indicate that OCIAD1 is required for maintenance of normal steady-state levels of Complex III and the proteolytic processing of the catalytic subunit cytochrome (CYC1). In OCIAD1 depleted mitochondria, unprocessed CYC1 is hemylated and incorporated into Complex III. We propose that OCIAD1 acts as an adaptor within prohibitin assemblies to stabilize and/or chaperone CYC1 and to facilitate its proteolytic processing by the IMMP2L protease.