UFC1 maintains ACSL3 abundance through UFMylation-associated mechanisms to modulate lipid metabolism in skeletal muscle myoblasts.

Abstract

Ordered proliferation of skeletal muscle myoblasts is essential for muscle development and repair and requires coordinated metabolic remodeling. Acyl-CoA synthetase long-chain family member 3 (ACSL3) activates long-chain fatty acids and thereby supports lipid metabolic flux, but the post-translational mechanisms regulating ACSL3 in myoblasts remain incompletely defined. UFMylation is a ubiquitin-like post-translational modification mediated by a cascade that includes the E2-conjugating enzyme UFC1. Here, we investigated whether UFC1 regulates ACSL3 abundance and lipid metabolism in C2C12 myoblasts and primary mouse skeletal muscle myoblasts. UFC1 knockout or knockdown reduced ACSL3 protein abundance, decreased myoblast proliferation, and lowered cellular neutral and polar lipid signals. Transcriptomic gene set enrichment analysis further indicated suppression of pathways related to unsaturated fatty acid biosynthesis and fatty acid metabolism after UFC1 loss. Co-immunoprecipitation showed an association between UFC1 and ACSL3, and endogenous immunoprecipitation detected a UFC1-dependent UFM1 signal on ACSL3. Cycloheximide chase assays indicated accelerated ACSL3 degradation in UFC1-deficient cells, whereas the proteasome inhibitor MG132 partially restored ACSL3 protein abundance. Overexpression of ACSL3 alleviated lipid metabolic defects and partially rescued proliferation in UFC1-deficient myoblasts. These findings suggest that UFC1 contributes to ACSL3 protein abundance, probably through UFMylation-associated suppression of proteasomal degradation, thereby supporting lipid homeostasis and proliferation in skeletal muscle myoblasts.