Investigation of the mechanism responsible for the modulation of myosin heavy chain expression in muscle fibers.

• Project/Area Number: 24890301
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Environmental physiology (including Physical medicine and Nutritional physiology)
• Research Institution: Japan Aerospace Exploration Agency
• Principal Investigator: OHIRA Takashi 独立行政法人宇宙航空研究開発機構, 有人宇宙ミッション本部, 宇宙航空プロジェクト研究員 (40633532)
• Project Period (FY): 2012-08-31 – 2014-03-31
• Project Status: Completed (Fiscal Year 2013)
• Budget Amount: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000); Fiscal Year 2013: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2012: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: 骨格筋 / タンパク質発現調節

Research Abstract

Gravitational unloading causes a shift of fiber phenotype toward fast-twitch type in soleus muscle. However some fibers are remain slow-twitch type. It has not known why the transformation of myosin heavy chain (MHC) phenotype is induced only in specific fibers expressing type I MHC originally. The current study was performed to investigate the effects of mechanical and/or neural factors on the fiber phenotype. Responses of MHC expression in soleus muscles to 2-week inhibition of mechanical activity or neural activity by hindlimb suspension or ablation of sciatic nerve respectively, were studied in rats. As a result, both experimental model was induced the increase of the type II MHC mRNA and protein expression. And the % distribution of fibers co-expressing type I and II MHC was increased. But fibers expressing pure type I MHC were still noted. It was suggested that the cause for de novo expression of type II MHC might be regulated by mechanical and neural activity and other factors.