A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex restrains excessive mitophagy to prevent mitochondrial disease

Jiang, H.; Cao, Y.

doi:10.1101/2022.11.11.516094

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bioRxiv · 10.1101/2022.11.11.516094

A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex restrains excessive mitophagy to prevent mitochondrial disease

Jiang, H.·Cao, Y.

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Abstract

Mitophagy is a fundamental quality control mechanism of mitochondria. Its regulatory mechanisms and pathological implications remain poorly understood. Here via a mitochondria-targeted screen, we found that knockout (KO) of FBXL4, a mitochondrial disease gene, hyperactivates mitophagy at basal conditions. Subsequent counter screen revealed that FBXL4-KO hyperactivates mitophagy via two mitophagy receptors BNIP3 and NIX. We determined that FBXL4 functions as an integral outer-membrane protein that forms an SCF-FBXL4 ubiquitin E3 ligase complex. SCF-FBXL4 ubiquitinates BNIP3 and NIX to target them for degradation. Pathogenic FBXL4 mutations disrupt SCF-FBXL4 assembly and impair substrate degradation. Fbxl4-/- mice exhibit elevated BNIP3 and NIX proteins, hyperactive mitophagy, and perinatal lethality. Importantly, knockout of either Bnip3 or Nix rescues metabolic derangements and viability of the Fbxl4-/- mice. Together, beyond identifying SCF-FBXL4 as a novel mitochondrial ubiquitin E3 ligase restraining basal mitophagy, our results reveal hyperactivated mitophagy as a cause of mitochondrial disease and suggest therapeutic strategies.

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Jiang, H., Cao, Y.. 2022-11-12. A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex restrains excessive mitophagy to prevent mitochondrial disease. https://doi.org/10.1101/2022.11.11.516094

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