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Research Square
2693-5015
American Journal Experts

10.21203/rs.3.rs-4985689/v1
10.21203/rs.3.rs-4985689
preprint
1
Article
CALHM2 is a mitochondrial protein import channel that regulates fatty acid metabolism
Jonas Elizabeth https://orcid.org/0000-0002-1624-5999

Mnatsakanyan Nelli
Rivera-Molina Felix
Robson Andrew
Garfinkel Alexandra MacColl https://orcid.org/0000-0002-4434-3262

Kumar Amrendra https://orcid.org/0000-0002-3599-7520

Batter Stephen
Padovano Valeria https://orcid.org/0000-0002-0142-3385

Webster Kaitlin
Cardone Rebecca
Berg Justin
Toomre Derek
IV Richard Kibbey
Caplan Michael https://orcid.org/0000-0001-5768-4405

Khokha Mustafa https://orcid.org/0000-0002-9846-7076

13 9 2024
rs.3.rs-4985689https://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License, which allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use.
https://www.researchsquare.com/article/rs-4985689/v1
nihpp-rs4985689v1.pdf
Abstract

For mitochondrial metabolism to occur in the matrix, multiple proteins must be imported across the two (inner and outer) mitochondrial membranes. Classically, two protein import channels, TIM/TOM, are known to perform this function, but whether other protein import channels exist is not known. Here, using super-resolution microscopy, proteomics, and electrophysiological techniques, we identify CALHM2 as the import channel for the ECHA subunit of the mitochondrial trifunctional protein (mTFP), which catalyzes β-oxidation of fatty acids in the mitochondrial matrix. We find that CALHM2 sits specifically at the inner mitochondrial and cristae membranes and is critical for membrane morphology. Depletion of CALHM2 leads to a mislocalization of ECHA outside of the mitochondria leading to severe cellular metabolic defects. These defects include cytosolic accumulation of fatty acids, depletion of tricarboxylic acid cycle enzymes and intermediates, and reduced cellular respiration. Our data identify CALHM2 as an essential protein import channel that is critical for fatty acid- and glucose-dependent aerobic metabolism. 
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