Self‐clearance mechanism of mitochondrial E3 ligase MARCH5 contributes to mitochondria quality control

Abstract

, and has been proposed to play a role in mitochondria quality control. However, it remains unclear how mutant MARCH5 found in cancer tissues is removed from cells. Here, we show that mutation in the MARCH5 ligase domain increased its half-life fourfold, resulting in a drastic increase in its protein level. Abnormal accumulation of the E3 ligase-defective MARCH5 mutants MARCH5H43W and MARCH5 C65/68S was diminished by overexpression of active MARCH5WT ; the mutant proteins were degraded through the ubiquitin-proteasome pathway. Coimmunoprecipitation revealed that MARCH5 forms homodimers, and that substitution of Gly to Leu at the first putative GxxxG dimerization motif, but not the second, resulted in a loss of dimeric interaction. Moreover, overexpression of the dimerization-defective mutant MARCH5 4GL could not decrease the level of accumulated MARCH5 H43W , suggesting that dimerization of MARCH5 is necessary for self-clearance. Abnormal accumulation of MARCH5 H43W and mitochondrial hyperfusion led to NF-KB activation, which was suppressed by overexpression of MARCH5 WT . Together, the data reveal a self-protective mechanism involving MARCH5, which can target its own dysfunctional mutant for degradation in order to maintain mitochondrial homeostasis.

Mitochondrial E3 ligase MARCH 5 regulates FUNDC 1 to fine‐tune hypoxic mitophagy

“…We observed that hypoxia progressively enhanced the interaction between MARCH5 and FUNDC1 (Fig A), whereas the self‐interaction of MARCH5 was significantly decreased (Fig B and C). MARCH5 is able to form dimers or oligomers, which mediate degradation of dysfunctional mutant MARCH5 proteins to maintain mitochondrial quality . Indeed, cross‐linking analysis showed that MARCH5 homo‐oligomers were reduced under hypoxic conditions (Fig EV2).…”

“…Indeed, cross‐linking analysis showed that MARCH5 homo‐oligomers were reduced under hypoxic conditions (Fig EV2). A previous study showed that the MARCH5 G103/107L mutant (GL) fails to form oligomers . We thus constructed the MARCH5 GL mutant and co‐transfected it with wild‐type MARCH5.…”

Novel regulatory roles of Mff and Drp1 in E3 ubiquitin ligase MARCH5–dependent degradation of MiD49 and Mcl1 and control of mitochondrial dynamics

“…Given that MARCH5 forms oligomers (Karbowski et al. , 2007; Kim et al. , 2016) and assuming that MARCH5 mutants could interact with endogenous MARCH5 and therefore make data interpretation difficult (e.g., due to detection of proteins interacting with endogenous MARCH5 potentially being pulled down with the MARCH5 mutant), we used MARCH5 −/− instead of wild-type cells.…”

Chimeric mitochondrial peptides from contiguous regular and swinger RNA

“…Possibly, chimeric peptides integrated in regular proteins perturb proper protein folding. Incorrect folding induces various degradation mechanisms associated with mitophagy [5] , [42] , [122] , which could explain that only few chimeric peptides are detected within regular proteins. These findings are not incompatible with the possibility that at least some swinger transcripts and peptides are functional.…”