Characterization of a Novel Membrane Protein Insertase in the Mitochondrial Outer Membrane

Citation

Stevens, Taylor Anthony (2024) Characterization of a Novel Membrane Protein Insertase in the Mitochondrial Outer Membrane. Dissertation (Ph.D.), California Institute of Technology. https://resolver.caltech.edu/CaltechTHESIS:12092023-142606831

Abstract

Mitochondria are eukaryotic organelles derived from the endosymbiosis of an ancient bacteria. As a result of their endosymbiotic origin, the mitochondrial proteome is composed of a mixture of ancient bacterial derived genes and others which are unique to eukaryotes. This dual bacterial/eukaryotic protein origin results in a complicated landscape for biogenesis of mitochondrial proteins. This is particularly true for mitochondrial membrane proteins, since mitochondria have both an inner and outer membrane each with unique protein composition. Proteins localized to the outer mitochondrial membrane (OMM) are of particular interest due to their connection to many important physiological pathways in humans. OMM proteins are known to be inserted into the lipid bilayer by the MIM complex in yeast and by ATOM36 in trypanosomes, however it is not known how they are inserted in human cells. In my Ph.D. thesis, I describe the development of improved biochemical tools for protein purification and characterization, and then use them as part of an effort to characterize MTCH2, which we identify as the human gene responsible for OMM protein insertion. After identifying MTCH2 in a genome-wide screen, we use a variety of cell biology and biochemical experiments to show that MTCH2 is both necessary and sufficient for OMM protein insertion. We further show that endogenous OMM proteins are affected by MTCH2 depletion, and that apoptosis, a pathway relying on OMM proteins, is sensitive to MTCH2 modulation. Additional work in my thesis demonstrates that MTCH2 is a deeply conserved gene across metazoans, that other OMM insertases likely evolved independently in separate multi-cellular eukaryotic lineages.

Thesis Files