tailieunhanh - Báo cáo khoa học: Changes in acetylcholine receptor function induce shifts in muscle fiber type composition

AChRe )⁄ ) mice lacke-subunits of the acetylcholine receptor and thus fail to express adult-type receptors. The expression of fetal-type receptors throughout postnatal life alters postsynaptic signal transduction and causes a fast-to-slow fiber type transition, both in slow-twitch soleus muscle and in fast-twitch extensor digitorum longus muscle. | ễFEBS Journal Changes in acetylcholine receptor function induce shifts in muscle fiber type composition Tae-Eun Jin1 z Anton Wernig2 and Veit Witzemann1 1 Abt. Zellphysiologie Max-Planck-Institut fur Medizinische Forschung Heidelberg Germany 2 Institut fur Physiologie Universitat Bonn Germany Keywords acetylcholine receptor acetylcholine receptor e-subunit knockout mice fast and slow muscle fiber type real-time PCR Correspondence V. Witzemann Abt. Zellphysiologie Max-Planck-Institut fur Medizinische Forschung Jahnstr. 29 D-69120 Heidelberg Germany Fax 49 6221 486459 Tel 49 6221 486475 E-mail witzeman@ Present address Center for CellSignaling Research Ewha Woman s University Seoul South Korea Received 9 January 2008 revised 12 February 2008 accepted 25 February 2008 doi AC iRe mice lack e-subunits of the acetylcholine receptor and thus fail to express adult-type receptors. The expression of fetal-type receptors throughout postnatal life alters postsynaptic signal transduction and causes a fast-to-slow fiber type transition both in slow-twitch soleus muscle and in fast-twitch extensor digitorum longus muscle. In comparison to wildtype muscle the proportion of type 1 slow fibers is significantly increased 6 whereas the proportion of fast fibers is reduced in soleus type 2A by 12 and in extensor digitorum longus type 2B 2D by 10 . The increased levels of troponin Islow transcripts clearly support a fast-to-slow fiber type transition. Shifts of protein and transcript levels are not restricted to myogenic genes but also affect synaptogenic genes. Clear increases are observed for acetylcholine receptor a-subunits and the post-synaptically located utrophin. Although the fast-to-slow fiber type transition appears to occur in a coordinated manner in both muscle types muscle-specific differences are retained. Most prominently the differential expression level of the synaptic regulator MuSK is significantly lower in .