Dependence of cross-bridge kinetics on myosin light chain isoforms in rabbit and rat skeletal muscle fibres
Dependence of cross-bridge kinetics on myosin light chain isoforms in rabbit and rat skeletal muscle fibres
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DOI：
10.1113/jphysiol.2005.099770
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发表时间：
2006-02-15
影响因子：
5.5
通讯作者：
Galler, S
中科院分区：
文献类型：
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作者：
Andruchov, O;Andruchova, O;Galler, S
本文研究了兔和大鼠骨骼肌肌球蛋白轻链（MLC）亚型不同的肌纤维在牵张诱导力瞬变过程中的跨桥动力学。力瞬变由施加在最大Ca 2+活化的皮肤纤维上的逐步拉伸（< 0.3%的纤维长度）引起。分别研究了IIB、IID（或IIX）和IIA型快纤维和含有肌球蛋白重链亚型MHC-IIb、MHC-IId（或MHC-IIx）、MHC-IIa和MHC-I的I型慢纤维。MLC异构体含量在纤维类型内变化。快速纤维类型包含快速调节MLC亚型MLC 2f和不同比例的快速碱性MLC亚型MLC 1f和MLC 3f。I型纤维含有慢调节MLC亚型MLC 2和慢碱性MLC亚型MLC 1。慢MLC亚型也存在于几个IIA型纤维。力瞬变的动力学在纤维类型之间相差约30倍（从最快到最慢的动力学顺序：IIB > IID > IIA >> I）。力瞬变的动力学不依赖于MLC 1f和MLC 3f的相对含量。含有快和慢MLC亚型的IIA型纤维比仅含有快MLC亚型的IIA型纤维慢约1.2倍。我们的结论是，虽然跨桥动力学主要是由MHC异构体存在，它是由快速和慢速MLC异构体的影响，但不是由MLC 1f和MLC 3f的相对含量。因此，快和慢MLC亚型在IIA型纤维中的生理作用是对跨桥动力学的微调。
Cross-bridge kinetics underlying stretch-induced force transients was studied in fibres with different myosin light chain (MLC) isoforms from skeletal muscles of rabbit and rat. The force transients were induced by stepwise stretches (< 0.3% of fibre length) applied on maximally Ca2+-activated skinned fibres. Fast fibre types IIB, IID (or IIX) and IIA and the slow fibre type I containing the myosin heavy chain isoforms MHC-IIb, MHC-IId (or MHC-IIx), MHC-IIa and MHC-I, respectively, were investigated. The MLC isoform content varied within fibre types. Fast fibre types contained the fast regulatory MLC isoform MLC2f and different proportions of the fast alkali MLC isoforms MLC1f and MLC3f. Type I fibres contained the slow regulatory MLC isoform MLC2s and the slow alkali MLC isoform MLC1s. Slow MLC isoforms were also present in several type IIA fibres. The kinetics of force transients differed by a factor of about 30 between fibre types (order from fastest to slowest kinetics: IIB > IID > IIA >> I). The kinetics of the force transients was not dependent on the relative content of MLC1f and MLC3f. Type IIA fibres containing fast and slow MLC isoforms were about 1.2 times slower than type IIA fibres containing only fast MLC isoforms. We conclude that while the cross-bridge kinetics is mainly determined by the MHC isoforms present, it is affected by fast and slow MLC isoforms but not by the relative content of MLC1f and MLC3f. Thus, the physiological role of fast and slow MLC isoforms in type IIA fibres is a fine-tuning of the cross-bridge kinetics.