Pabpn1-driven cytoskeletal rearrangement induces muscle wasting

Poly(A) binding protein nuclear 1 (PABPN1) is a multifunctional regulator of mRNA processing. PABPN1 inhibits alternative polyadenylation (APA), and in conditions with reduced PABPN1 levels APA utilization causes genome-wide mRNA dysregulation. PABPN1 levels decline from midlife onwards in Oculopharyngeal Muscular Dystrophy (OPMD) and in aged muscles. Reduced PABPN1 levels cause muscle atrophy by altering mRNA levels of the ubiquitin proteasome system. The effect of PABPN1-mediated APA utilization on the proteome has not been investigated yet. We report the PABPN1-mediated proteome in Tibialis anterior (TA) mouse muscles, signifying functional impact for the mitochondria, cytoskeleton and translation cellular machineries. Central nucleation and split myofibers marked PABPN1-derived muscle histology. We show that up-regulation of the cytoskeletal proteins: Murc, Pfn1 and Csrp3, is highly associated with PABPN1-mediated muscle pathology and with reduced PABPN1 levels. Elevation of PABPN1 levels by sirtinol treatment reversed muscle pathology and restored levels of those cytoskeletal proteins. We suggest that restoration of PABPN1 levels in aged muscles could be a novel therapeutic strategy to mitigate muscle waste.