Eilers Wouter, Jaspers Richard T, de Haan Arnold, Ferrié Céline, Valdivieso Paola, Flück Martin
Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, John Dalton Building, Oxford Road, M1 5GD, Manchester, United Kingdom.
Laboratory for Myology, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands.
BMC Physiol. 2014 Dec 17;14:7. doi: 10.1186/s12899-014-0007-z.
The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main CaMK in skeletal muscle and its expression increases with endurance training. CaMK family members are implicated in contraction-induced regulation of calcium handling, fast myosin type IIA expression and mitochondrial biogenesis. The objective of this study was to investigate the role of an increased CaMKII content for the expression of the contractile and mitochondrial phenotype in vivo. Towards this end we attempted to co-express alpha- and beta-CaMKII isoforms in skeletal muscle and characterised the effect on the contractile and mitochondrial phenotype.
Fast-twitch muscle m. gastrocnemius (GM) and slow-twitch muscle m. soleus (SOL) of the right leg of 3-month old rats were transfected via electro-transfer of injected expression plasmids for native α/β CaMKII. Effects were identified from the comparison to control-transfected muscles of the contralateral leg and non-transfected muscles. α/β CaMKII content in muscle fibres was 4-5-fold increased 7 days after transfection. The transfection rate was more pronounced in SOL than GM muscle (i.e. 12.6 vs. 3.5%). The overexpressed α/β CaMKII was functional as shown through increased threonine 287 phosphorylation of β-CaMKII after isometric exercise and down-regulated transcripts COXI, COXIV, SDHB after high-intensity exercise in situ. α/β CaMKII overexpression under normal cage activity accelerated excitation-contraction coupling and relaxation in SOL muscle in association with increased SERCA2, ANXV and fast myosin type IIA/X content but did not affect mitochondrial protein content. These effects were observed on a background of regenerating muscle fibres.
Elevated CaMKII content promotes a slow-to-fast type fibre shift in regenerating muscle but is not sufficient to stimulate mitochondrial biogenesis in the absence of an endurance stimulus.
多聚体钙/钙调蛋白依赖性蛋白激酶II（CaMKII）是骨骼肌中的主要CaMK，其表达随耐力训练而增加。CaMK家族成员参与收缩诱导的钙处理调节、快肌球蛋白IIA型表达和线粒体生物发生。本研究的目的是探讨体内CaMKII含量增加对收缩和线粒体表型表达的作用。为此，我们试图在骨骼肌中共表达α-和β-CaMKII亚型，并表征其对收缩和线粒体表型的影响。
通过电转染注射的天然α/β CaMKII表达质粒，对3个月大的大鼠右腿的快肌腓肠肌（GM）和慢肌比目鱼肌（SOL）进行转染。通过与对侧腿的对照转染肌肉和未转染肌肉进行比较来确定效果。转染7天后，肌纤维中的α/β CaMKII含量增加了4-5倍。转染率在SOL肌肉中比GM肌肉更明显（即12.6%对3.5%）。过表达的α/β CaMKII具有功能，如等长运动后β-CaMKII的苏氨酸287磷酸化增加以及原位高强度运动后转录本COXI、COXIV、SDHB下调所示。在正常笼内活动条件下，α/β CaMKII过表达加速了SOL肌肉中的兴奋-收缩偶联和舒张，同时SERCA2、ANXV和快肌球蛋白IIA型/X含量增加，但不影响线粒体蛋白含量。这些效应是在再生肌纤维的背景下观察到的。
CaMKII含量升高促进再生肌肉中慢肌纤维向快肌纤维类型的转变，但在没有耐力刺激的情况下不足以刺激线粒体生物发生。
