Geranylgeranylated SCFFBXO10 regulates selective outer mitochondrial membrane proteostasis and function

Compartment-specific cellular membrane protein turnover is not well understood. We show that FBXO10, the interchangeable component of the cullin-RING-ligase 1 complex, undergoes lipid modification with geranylgeranyl isoprenoid at cysteine953, facilitating its dynamic trafficking to the outer mitochondrial membrane (OMM). FBXO10 polypeptide lacks a canonical mitochondrial targeting sequence (MTS); instead, its geranylgeranylation at C953 and interaction with two cytosolic factors, cytosolic factor-like δ subunit of type 6 phosphodiesterase (PDE6δ; a prenyl-group-binding protein) and heat shock protein 90 (HSP90; a chaperone), orchestrate specific OMM targeting of prenyl-FBXO10. The FBXO10(C953S) mutant redistributes away from the OMM, impairs mitochondrial ATP production and membrane potential, and increases fragmentation. Phosphoglycerate mutase-5 (PGAM5) was identified as a potential substrate of FBXO10 at the OMM using comparative quantitative proteomics of enriched mitochondria. FBXO10 loss or expression of prenylation-deficient FBXO10(C953S) inhibited PGAM5 degradation, disrupted mitochondrial homeostasis, and impaired myogenic differentiation of human induced pluripotent stem cells (iPSCs) and murine myoblasts. Our studies identify a mechanism for FBXO10-mediated regulation of selective mitochondrial proteostasis potentially amenable to therapeutic intervention. [Display omitted] •Prenylation of SCFFBXO10 is required for trafficking to the outer mitochondrial membrane•Mitochondrial trafficking of FBXO10 depends on binding to PDE6δ and HSP90•Unbiased proteomics identifies trafficking-dependent mitochondrial targets of FBXO10•Impaired trafficking or depletion of FBXO10 suppresses myogenic differentiation Bhat et al. show that the E3-ligase SCFFBXO10 is prenylated at C953 in its C-terminal CaaX motif. Prenylated FBXO10 is specifically delivered to the outer mitochondrial membrane via combined actions of cytosolic PDE6δ and HSP90. The expression of prenylation-deficient FBXO10(C953S) impairs mitochondrial proteostasis and functions. FBXO10 loss impairs myogenic differentiation of human iPSCs and murine myoblasts.