Titin isoform-dependent effect of calcium on passive myocardial tension
Titin isoform-dependent effect of calcium on passive myocardial tension
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DOI：
10.1152/ajpheart.00553.2004
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发表时间：
2004-12-01
影响因子：
4.8
通讯作者：
Granzier, HL
中科院分区：
文献类型：
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作者：
Fujita, H;Labeit, D;Granzier, HL
我们研究了Ca2+对主要表达N2B titin（大鼠右心室，RRV）或主要表达N2BA titin（牛左心房，BLA）的皮肤心肌中titin（连接蛋白）为基础的被动张力的影响。通过选择性地去除Ca2+不敏感凝胶片段（FX-45）的细丝，肌动球蛋白基张力被消除到无法检测到的低水平。在Ca2+存在和不存在的情况下拉伸心肌，并测量被动张力。Ca2+显著增加BLA拉伸期间和拉伸后的被动张力。这种增加对肌动球蛋白抑制剂2,3-丁二酮2-单肟不敏感，支持这种效应是基于titin的结论。在RRV中，被动张力对钙没有反应，表明N2B titin产生的被动张力对钙不敏感。Western blot分析和免疫荧光研究表明，N2BA titin表达富含e的PEVK基序，而N2B titin中不存在这些基序，这支持了早期的单分子研究，即富e基序是钙敏感性所必需的。我们得出的结论是，钙以一种titin亚型依赖的方式影响被动心肌张力。
We studied the effects of Ca2+ on titin (connectin)-based passive tension in skinned myocardium expressing either predominantly N2B titin (rat right ventricle, RRV) or predominantly N2BA titin (bovine left atrium, BLA). Actomyosin-based tension was abolished to undetectably low levels by selectively removing the thin filaments with a Ca2+-insensitive gelsolin fragment (FX-45). Myocardium was stretched in the presence and absence of Ca2+, and passive tension was measured. Ca2+ significantly increased passive tension during and after stretch in the BLA. The increase was insensitive to the actomyosin inhibitor 2,3-butanedione 2-monoxime, supporting the conclusion that the effect is titin based. Passive tension did not respond to calcium in the RRV, indicating that passive tension developed by N2B titin is calcium insensitive. Western blot analysis and immunofluorescence studies indicated that N2BA titin expresses E-rich PEVK motifs, whereas they are absent from N2B titin, supporting earlier single molecule studies that reported that E-rich motifs are required for calcium sensitivity. We conclude that calcium affects passive myocardial tension in a titin isoform-dependent manner.