Expression of titin isoforms in red and white muscle fibres of carp (Cyprinus carpio L.) exposed to different sarcomere strains during swimming.
Expression of titin isoforms in red and white muscle fibres of carp (Cyprinus carpio L.) exposed to different sarcomere strains during swimming.
复制标题
游泳期间接触不同肌节菌株的鲤鱼（Cyprinus carpio L.）红色和白色肌纤维中肌联蛋白亚型的表达。
DOI：
10.1007/s003600050107
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Granzier,HL
中科院分区：
文献类型：
--
作者：
Spierts,IL;Akster,HA;Granzier,HL
肌联蛋白（也称为连接蛋白）是一种横纹肌特异性蛋白，跨越肌节的Z线和M线之间的距离。I带肌联蛋白分子的弹性部分被认为负责产生被动张力和维持收缩肌节中粗丝的中心位置。不同的肌肉类型表达不同分子量的肌联蛋白亚型。为了帮助阐明肌联蛋白亚型的发生和不同的纤维类型的功能特性之间的关系，我们调查了存在不同的肌联蛋白亚型的红色和白色纤维的鲤鱼的轴肌。单纤维的凝胶电泳显示，肌联蛋白的分子量较大，在红色比在白色纤维。还比较了前、后轴肌的纤维。对于白色和红色纤维的肌联蛋白的分子量在后肌纤维大于在前肌纤维。因此，相同的纤维类型可以表达不同的肌联蛋白亚型，这取决于其沿着体轴的位置。还测定了肌联蛋白对红色前、后纤维被动张力和刚度的贡献。单纤维剥皮和肌节长度的被动张力和被动刚度的依赖性进行了测定。在用0.6 mol·l− 1 KCl和1 mol·l− 1 KI的松弛溶液提取细丝和粗细丝之前和之后进行测量。 假设在提取前测量的张力和刚度是由肌联蛋白和中间丝引起的，并且仅从中间丝提取后的张力。与哺乳动物骨骼肌相比，中间纤维在后部和前部纤维中都产生了高水平的张力和刚度。肌联蛋白的被动张力-肌节长度曲线在红色前纤维中比在红色后纤维中增加得更陡，并且曲线在较短的肌节长度处达到平台。因此，对于给定的肌节应变，前纤维的较小肌联蛋白同种型导致更多的被动张力和刚度。在连续游泳过程中，红色纤维比白色纤维暴露于更大的肌节应变变化，后部纤维比前部纤维暴露于更大的应变变化。我们建议，肌节应变是一个功能参数，调节不同的肌联蛋白异构体的表达在轴向肌纤维的鲤鱼。
Titin (also known as connectin) is a striated-muscle-specific protein that spans the distance between the Z- and M-lines of the sarcomere. The elastic segment of the titin molecule in the I-band is thought to be responsible for developing passive tension and for maintaining the central position of thick filaments in contracting sarcomeres. Different muscle types express isoforms of titin that differ in their molecular mass. To help to elucidate the relation between the occurrence of titin isoforms and the functional properties of different fibre types, we investigated the presence of different titin isoforms in red and white fibres of the axial muscles of carp. Gel electrophoresis of single fibres revealed that the molecular mass of titin was larger in red than in white fibres. Fibres from anterior and posterior axial muscles were also compared. For both white and red fibres the molecular mass of titin in posterior muscle fibres was larger than in anterior muscle fibres. Thus, the same fibre type can express different titin isoforms depending on its location along the body axis. The contribution of titin to passive tension and stiffness of red anterior and posterior fibres was also determined. Single fibres were skinned and the sarcomere length dependencies of passive tension and passive stiffness were determined. Measurements were made before and after extracting thin and thick filaments using relaxing solutions with 0.6 mol · l−1KCl and 1 mol · l−1KI. Tension and stiffness measured before extraction were assumed to result from both titin and intermediate filaments, and tension after extraction from only intermediate filaments. Compared to mammalian skeletal muscle, intermediate filaments developed high levels of tension and stiffness in both posterior and anterior fibres. The passive tension-sarcomere length curve of titin increased more steeply in red anterior fibres than in red posterior fibres and the curve reached a plateau at a shorter sarcomere length. Thus, the smaller titin isoform of anterior fibres results in more passive tension and stiffness for a given sarcomere strain. During continuous swimming, red fibres are exposed to larger changes in sarcomere strain than white fibres, and posterior fibres to larger changes in strain than anterior fibres. We propose that sarcomere strain is one of the functional parameters that modulates the expression of different titin isoforms in axial muscle fibres of carp.