Inactivation of ATG13 stimulates chronic demyelinating pathologies in muscle-serving nerves and spinal cord.

Abstract

Chronic muscle fatigue is a condition characterized by debilitating muscle weakness and pain. Based on our recent finding to study the potential effect of mTOR on ATG13 inactivation in chronic muscle fatigue, we report that biweekly oral administration with MHY1485, a potent inducer of mTOR, develops chronic illness in mice resulting in severe muscle weakness. As a mechanism, we observed that MHY1485 feeding impaired ATG13-dependent autophagy, caused the infiltration of inflammatory M1 macrophages (Mφ), upregulated IL6 and RANTES by STAT3 activation, and augmented demyelination in muscle-serving nerve fibers. Interestingly, these mice displayed worsened muscle fatigue during 2-day post-treadmill exercise, suggesting the critical role of chronic mTOR activation in potential PEM pathogenesis. Interestingly, ATG13-repressor mice exhibited enhanced infiltration of M1Mφ cells, STAT3 activation, demyelination of nerve fibers, and PEM-like symptoms, suggesting the potential role of ATG13 impairment in post-exertional fatigue. HIGHLIGHTS: The potential role of mTOR activation in post-exertional fatigue is highlighted. As a molecular mechanism, mTOR activation augments autophagy impairment via ATG13 inactivation. Autophagy impairment induces IL-6 and RANTES via STAT3, demyelinates nerves in the muscle and spinal cord. ATG13 repressor mice (Tg-ATG13) displayed inflammatory demyelination and post-treadmill fatigue.