Abstract

The cellular prion protein (PrP^C) is required for skeletal muscle function. Here, we report that a higher level of PrP^C accumulates in the cytoplasm of the skeletal muscle of six myopathy patients compared to controls. PrP^C inhibits skeletal muscle cell autophagy, and blocks myoblast differentiation. PrP^C selectively binds to a subset of miRNAs during myoblast differentiation, and the colocalization of PrP^C and miR-214-3p was observed in the skeletal muscle of six myopathy patients with excessive PrP^C. We demonstrate that PrP^C is overexpressed in skeletal muscle cells under pathological conditions, inhibits muscle cell differentiation by physically interacting with a subset of miRNAs, and selectively recruits these miRNAs into its phase-separated condensate in living myoblasts, which in turn enhances liquid–liquid phase separation of PrP^C, promotes pathological aggregation of PrP, and results in the inhibition of autophagy-related protein 5-dependent autophagy and muscle bundle formation in myopathy patients characterized by incomplete muscle regeneration.