Attenuation of length dependence of calcium activation in myofilaments of transgenic mouse hearts expressing slow skeletal troponin I
Attenuation of length dependence of calcium activation in myofilaments of transgenic mouse hearts expressing slow skeletal troponin I
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DOI：
10.1111/j.1469-7793.2000.t01-1-00541.x
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发表时间：
2000-08-01
影响因子：
5.5
通讯作者：
Solaro, RJ
中科院分区：
文献类型：
--
作者：
Arteaga, GM;Palmiter, KA;Solaro, RJ
1.我们比较了从野生型(WT)和表达慢速骨骼肌钙蛋白I(ssTnI-TG)的转基因小鼠心脏中分离的洗涤剂提取的纤维束的肌节长度(SL)与时间的钙-力关系。来自心脏的纤维束表明，肌钙蛋白I(CTnI)被肌钙蛋白I(CTnI)完全取代。与WT对照相比，在短SL(1.9±0.1微米)和长SL(2.3±0.1微米)下，ssTnI-TG纤维束对钙离子的敏感性都较高。然而，与WT对照组相比，与SL增加相关的钙敏感性的增加(一半最大激活游离钙的变化；Delta EC50)在ssTnI-TG肌丝中显著减弱。通过促进肌动蛋白-肌球蛋白反应(肌动蛋白-肌球蛋白反应)57033和CGp-48506使肌丝对钙敏感的药物)显著降低了当WT肌丝的SL从1.9µm增加到2.3µm时，钙激活的长度依赖的Delta EC50。将肌丝暴露于卡咪唑(CDZ)，CDZ与cTNC结合并增加其对钙离子的亲和力，使WT肌丝在SL 1.9微米处对钙离子产生敏感力，在SL 2.3微米处使WT肌丝失敏，CDZ对SSTnI-TG肌丝在两个剂量组均无显著影响。我们的结果表明，依赖于长度的钙激活被Thill细丝蛋白的特定变化和促进肌动蛋白-肌球蛋白相互作用的试剂所改变。因此，这些体外结果为使用这些模型来测试原位激活的长度依赖关系的相对重要性提供了基础。
1. We compared sarcomere length (SL) dependence of time Ca2+-force relation of detergent extracted bundles of fibres dissected from the left ventricle of wild-type (WT) and transgenic mouse hearts expressing slow skeletal troponin I (ssTnI-TG). Fibre bundles from the hearts of the ssTnI-TG demonstrated a complete replacement of the cardiac troponin I (cTnI) by ssTnI.2. Compared to WT controls, ssTnI-TG fibre bundles were more sensitive to Ca2+ at both short SL (1.9 + 0.1 mu m) and long SL (2.3 + 0.1 mu m). However, compared to WT controls, the increase in Ca2+ sensitivity (change in half-maximally activating free Ca2+; Delta EC50) associated with the increase in SL was significantly blunted in the ssTnI-TG myofilaments.3. Agents that sensitize the myofilaments to Ca2+ by promoting the actin-myosin reaction (EMI) 57033 and CGP-48506) significantly reduced the length-dependent Delta EC50 for Ca2+ activation, when SL in WT myofilaments was increased from 1.9 to 2.3 mu m.4. Exposure of myofilaments to calmidazolium (CDZ), which binds to cTnC and increases its affinity for Ca2+, sensitized force developed, by WT myofilaments to Ca2+ at SL 1.9 mu m and desensitized the WT myofilaments at SL 2.3 mu m. There were no significant effects of CDZ on ssTnI-TG myofilaments at either XL.5. Our results indicate that length-dependent Ca2+ activation is modified by specific changes in thill filament proteins and by agents that promote the actin-myosin interaction. Thus, these in vitro results provide a basis for using these models to test the relative significance of the length dependence of activation in situ.