Overexpression of a Novel E3 Ligase leads to a Skeletal Muscle Myopathy through Alterations in Cytoskeleton Proteins and Enhanced Protein Degradation

Abstract

Multiple E3 ubiquitin ligases have been identified to be transcriptionally increased in skeletal muscle under atrophy‐inducing conditions. We have recently observed a novel E3 ligase, F‐box and Leucine‐rich protein 22 (FbxL22), to be elevated during denervation‐induced muscle atrophy. Little is known about the role of FbxL22 in skeletal muscle, with recent research highlighting its impact on cardiac muscle function and sarcomeric protein turnover (Spaich et al., 2012).Subsequently, male C57BL/6 mice (12‐week old) were subjected to in vivo electroporation with a mouse specific FbxL22 plasmid (20ug) in the tibialis anterior (TA) muscle with the contralateral leg serving as an empty vector control (pcDNA3.1). After 14 days, TA muscles were sectioned for H&E stain and GFP visualisation to confirm plasmid incorporation. Muscle mass and cross‐sectional area (CSA) were determined. Western blotting was performed to determine intermediate filament, autophagy and poly‐ubiquitin protein levels in the transfected TA muscles.Interestingly, we observed no difference in muscle mass after 14 days, but we did observe increased numbers of large and small fibers in the FbxL22 transfected muscle. At the protein level, there was a 75% reduction in alpha‐actinin‐2, which was accompanied by 4‐fold increase in desmin and vimentin. We additionally observed a 2‐fold increase in polyubquitination, and 1.5‐fold increase in autophagy markers (p62 and LCB II).Our data highlights the powerful impact of FbxL22 on skeletal muscle structure. Future studies will seek to investigate the chronic effect of FbxL22 on skeletal muscle and characterize its role during the process of muscle atrophy.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.