Biomedical Research

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Research Article - Biomedical Research (2019) Volume 30, Issue 4

Independent behaviors of myostatin and E3 ubiquitin ligases in atrophied fast and slow skeletal muscles

In skeletal muscle, the expression of myostatin and activation of muscle-specific E3 ubiquitin ligases play roles in protein degradation and atrophy. Although fiber-type dependency of myostatin expression has been reported, it is unclear whether the relationship between myostatin expression and activation of muscle-specific E3 ubiquitin ligases shows a similar tendency The objective of this study was to determine whether expressions of myostatin and muscle-specific E3 ubiquitin ligases differ, depending on fiber type in muscle atrophy induced by nerve crush injury (NCI) to the rat sciatic nerve. Soleus (rich in slow-twitch fibers) and plantaris (rich in fast-twitch fibers) muscles were analysed by Western blotting and immunohistochemistry. The wet weight of the plantaris muscle decreased gradually, reaching a minimum on 14th day after NCI, while the wet weight of the soleus muscle was lowest after 7th day. The cross sectional area (CSA) of type II muscle significantly reduced both soleus and plantaris muscle, but the type I muscle did not significantly decrease in plantaris muscle. The expression of muscle RING finger protein 1 (MuRF1) and muscle atrophy F-box (MAFbx)/atrogin-1, muscle-specific E3 ubiquitin ligases, were significantly higher in both soleus and plantaris muscles on day 3 after NCI compared to the untreated control group. A significantly increased level of myostatin was seen in plantaris muscle only on day 14 after NCI. We conclude that myostatin expression in NCI-induced muscle atrophy plays a role in only fast-twitch muscle atrophy. On the other hand, expressions of the MuRF1 and MAFbx are independent from fiber type.

Author(s): Kihyuk Lee, Takahiro Maekawa, Karina Kouzaki, Hongsun Song, Koichi Nakazato

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