Down_regulation of the mitochondrial i_AAA protease Yme1L induces muscle atrophy via FoxO3a and myostatin activation

Authors
YJ Lee, GH Kim, SI Park, JH Lim

Lab
Division of Endocrine and Metabolic Disease, Center for Biomedical Sciences, Korea National Institute of Health, Cheongju, Chungbuk 28159, Korea.

Journal
Journal of Cellular and Molecular Medicine

Abstract
Muscle atrophy is closely associated with many diseases, including diabetes and car_diac failure. Growing evidence has shown that mitochondrial dysfunction is related to muscle atrophy; however, the underlying mechanisms are still unclear. To elucidate how mitochondrial dysfunction causes muscle atrophy, we used hindlimb_immobilized mice. Mitochondrial function is optimized by balancing mitochondrial dynamics, and we observed that this balance shifted towards mitochondrial fission and that MuRF1 and atrogin_1 expression levels were elevated in these mice. We also found that the expression of yeast mitochondrial escape 1_like ATPase (Yme1L), a mitochondrial AAA protease was significantly reduced both in hindlimb_immobilized mice and carbonyl cyanide m_chlorophenylhydrazone (CCCP)_treated C2C12 myotubes. When Yme1L was depleted in myotubes, the short form of optic atrophy 1 (Opa1) accumulated, leading to mitochondrial fragmentation. Moreover, a loss of Yme1L, but not of LonP1, activated AMPK and FoxO3a and concomitantly increased MuRF1 in C2C12 myotubes. Intriguingly, the expression of myostatin, a myokine responsible for muscle protein degradation, was significantly increased by the transient knock_down of Yme1L. Taken together, our results suggest that a deficiency in Yme1L and the consequential imbalance in mitochondrial dynamics result in the activation of FoxO3a and myostatin, which contribute to the pathological state of muscle atrophy.

BIOSEB Instruments Used:
Grip strength test (BIO-GS3)