The research program described in this application deals with the mechanism of protein import into the mitochondrion. The experimental model is the budding yeast Saccharomyces cerevisiae, which is an ideal model for mammalian systems because protein import is highly conserved. Previous work has identified a new import pathway for proteins of the mitochondrial inner membrane, which is distinct from the pathway used by precursors with an amino-terminal targeting presequence. Components of this import pathway include the soluble Tim8/Tim13 and Tim9/Tim10 complexes of the intermembrane space and the TIM22 Complex (Tim12, Tim22, and Tim54) of the inner membrane. Mutations in DDP1 (deafness/dystonia protein; homologous to Tim8) cause the human disease Mohr-Tranebjaerg Syndrome, which is most likely caused by a defective protein import machinery. The objective of the research proposed here is to define the molecular mechanisms of this import pathway with a combined biochemical, biophysical and genetic approach. Specifically, the inner membrane substrates and their motifs, which are recognized by the Tim8/Tim13 and Tim9/Tim10 complexes, will be determined. Moreover, the mechanism by which the Tim8/Tim13 and Tim9/Tim10 complexes escort the substrates to the inner membrane will be elucidated. Using temperature-sensitive tim12 and tim22 mutants, additional components of the TIM22 complex will be identified and characterized with respect to location and function. The proposed project will expand fundamental knowledge about the mechanism of protein insertion into the mitochondrial inner membrane, extending present studies that have focused generally on how proteins reach the soluble compartments of the mitochondria. Also, these studies will contribute to the basic understanding of how proteins insert into membranes and how defects in mitochondrial biogenesis can contribute to mitochondrial diseases.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Shapiro, Bert I
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California Los Angeles
Schools of Arts and Sciences
Los Angeles
United States
Zip Code
Yien, Yvette Y; Shi, Jiahai; Chen, Caiyong et al. (2018) FAM210B is an erythropoietin target and regulates erythroid heme synthesis by controlling mitochondrial iron import and ferrochelatase activity. J Biol Chem 293:19797-19811
Steffen, Janos; Koehler, Carla M (2018) ER-mitochondria contacts: Actin dynamics at the ER control mitochondrial fission via calcium release. J Cell Biol 217:15-17
Steffen, Janos; Vashisht, Ajay A; Wan, Jijun et al. (2017) Rapid degradation of mutant SLC25A46 by the ubiquitin-proteasome system results in MFN1/2-mediated hyperfusion of mitochondria. Mol Biol Cell 28:600-612
Miyata, Non; Tang, Zhiye; Conti, Michael A et al. (2017) Adaptation of a Genetic Screen Reveals an Inhibitor for Mitochondrial Protein Import Component Tim44. J Biol Chem 292:5429-5442
Sangwan, Smriti; Zhao, Anni; Adams, Katrina L et al. (2017) Atomic structure of a toxic, oligomeric segment of SOD1 linked to amyotrophic lateral sclerosis (ALS). Proc Natl Acad Sci U S A 114:8770-8775
Neal, Sonya E; Dabir, Deepa V; Wijaya, Juwina et al. (2017) Osm1 facilitates the transfer of electrons from Erv1 to fumarate in the redox-regulated import pathway in the mitochondrial intermembrane space. Mol Biol Cell 28:2773-2785
Thangamani, Shankar; Maland, Matthew; Mohammad, Haroon et al. (2017) Repurposing Approach Identifies Auranofin with Broad Spectrum Antifungal Activity That Targets Mia40-Erv1 Pathway. Front Cell Infect Microbiol 7:4
Filipuzzi, Ireos; Steffen, Janos; Germain, Mitchel et al. (2017) Stendomycin selectively inhibits TIM23-dependent mitochondrial protein import. Nat Chem Biol 13:1239-1244
Lu, Ya-Wen; Galbraith, Laura; Herndon, Jenny D et al. (2016) Defining functional classes of Barth syndrome mutation in humans. Hum Mol Genet 25:1754-70
Wu, Ting-Hsiang; Sagullo, Enrico; Case, Dana et al. (2016) Mitochondrial Transfer by Photothermal Nanoblade Restores Metabolite Profile in Mammalian Cells. Cell Metab 23:921-9

Showing the most recent 10 out of 55 publications