IRE1α regulates skeletal muscle regeneration through myostatin mRNA decay
Shengqi He, … , Zhenji Gan, Yong Liu
Shengqi He, … , Zhenji Gan, Yong Liu
Published July 20, 2021
Citation Information: J Clin Invest. 2021;131(17):e143737. https://doi.org/10.1172/JCI143737.
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Research Article Muscle biology

IRE1α regulates skeletal muscle regeneration through myostatin mRNA decay

Abstract

Skeletal muscle can undergo a regenerative process in response to injury or disease to preserve muscle mass and function, which are critically influenced by cellular stress responses. Inositol-requiring enzyme 1 (IRE1) is an ancient endoplasmic reticulum stress sensor and mediates a key branch of the unfolded protein response. In mammals, IRE1α is implicated in the homeostatic control of stress responses during tissue injury and regeneration. Here, we show that IRE1α serves as a myogenic regulator in skeletal muscle regeneration in response to injury and muscular dystrophy. We found in mice that IRE1α was activated during injury-induced muscle regeneration, and muscle-specific IRE1α ablation resulted in impaired regeneration upon cardiotoxin-induced injury. Gain- and loss-of-function studies in myocytes demonstrated that IRE1α acts to sustain both differentiation in myoblasts and hypertrophy in myotubes through regulated IRE1-dependent decay (RIDD) of mRNA encoding myostatin, a key negative regulator of muscle repair and growth. Furthermore, in the mouse model of Duchenne muscular dystrophy, loss of muscle IRE1α resulted in augmented myostatin signaling and exacerbated the dystrophic phenotypes. These results reveal a pivotal role for the RIDD output of IRE1α in muscle regeneration, offering insight into potential therapeutic strategies for muscle loss diseases.

Authors

Shengqi He, Tingting Fu, Yue Yu, Qinhao Liang, Luyao Li, Jing Liu, Xuan Zhang, Qian Zhou, Qiqi Guo, Dengqiu Xu, Yong Chen, Xiaolong Wang, Yulin Chen, Jianmiao Liu, Zhenji Gan, Yong Liu

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Figure 4

IRE1α downregulates myostatin expression and promotes hypertrophy of differentiated myotubes.

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IRE1α downregulates myostatin expression and promotes hypertrophy of dif...
(A–J) C2C12 myoblast cells were differentiated for 4 days into myotubes and then infected for 48 hours with adenoviruses expressing a scramble control shRNA (Sh-Con) or shRNA directed against IRE1α (Sh-Ern1) (A–E), or with empty control adenovirus (Ad-Con) or that expressing human IRE1α (Ad-IRE1α) (F–J) (n = 4 independent experiments). (A and F) Quantitative RT-PCR analysis of Xbp1 mRNA splicing and the mRNA abundance of the indicated genes. (B and G) ELISA analysis of myostatin protein in culture medium. (C and H) Immunoblot analysis of the indicated proteins from myotube extracts. Averaged MyHC/actin, p-S6K/S6K, and p-Smad3/Smad3 ratios were normalized to the value of Sh-Con or Ad-Con myotubes. (D and I) MyHC immunostaining of myotubes. Myotube diameters were quantified using ImageJ software. (E and J) Total cellular protein content relative to genomic DNA was measured in myotubes. (K) C2C12 myotubes were infected with empty control or adenoviruses expressing the WT or indicated mutant IRE1α protein. Quantitative RT-PCR analysis of Xbp1 mRNA splicing and the mRNA abundance of Blos1 and Mstn (n = 4 independent experiments). All data represent mean ± SEM. Significance was calculated by unpaired 2-tailed Student’s t test (A–J) or 1-way ANOVA (K) with Bonferroni’s multiple-comparison test. *P < 0.05, **P < 0.01, ***P < 0.001 vs. Sh-Con or Ad-Con. Scale bars: 100 μm.