Journal
MOLECULAR CELL
Volume 51, Issue 1, Pages 20-34Publisher
CELL PRESS
DOI: 10.1016/j.molcel.2013.04.023
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Funding
- Ministry of Education, Culture, Sports, Science, and Technology
- Japan Society for the Promotion of Science
- Naito Foundation
- Sumitomo Foundation
- Grants-in-Aid for Scientific Research [24111545, 24112003, 25640040, 25460074, 24790903] Funding Source: KAKEN
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The mitochondrial ubiquitin ligase MITOL regulates mitochondria! dynamics. We report here that MITOL regulates mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) domain formation through nnitofusin2 (Mfn2). MITOL interacts with and ubiquitinates mitochondrial Mfn2, but not ER-associated Mfn2. Mutation analysis identified a specific interaction between MITOL C-terminal domain and Mfn2 HR1 domain. MITOL mediated lysine-63-linked polyubiquitin chain addition to Mfn2, but not its proteasomal degradation. MITOL knockdown inhibited Mfn2 complex formation and caused Mfn2 mislocalization and MAM dysfunction. Sucrose-density gradient centrifugation and blue native PAGE retardation assay demonstrated that MITOL is required for GTP-dependent Mfn2 oligomerization. MITOL knockdown reduced Mfn2 GTP binding, resulting in reduced GTP hydrolysis. We identified K192 in the GTPase domain of Mfn2 as a major ubiquitination site for MITOL. A K192R mutation blocked oligomerization even in the presence of GTP. Taken together, these results suggested that MITOL regulates ER tethering to mitochondria by activating Mfn2 via K192 ubiquitination.
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