Microscopic heat pulses activate cardiac thin filaments
Microscopic heat pulses activate cardiac thin filaments
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DOI：
10.1085/jgp.201812243
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发表时间：
2019-06-01
影响因子：
3.8
通讯作者：
Ishiwata, Shin'ichi
中科院分区：
文献类型：
--
作者：
Ishii, Shuya;Oyama, Kotaro;Ishiwata, Shin'ichi
在心脏的兴奋-收缩偶联期间，肌节通过细丝结构变化（即，从“关”状态到“开”状态），以响应肌浆网释放的Ca 2+。这个过程涉及高度依赖于环境温度的化学反应;例如，肌动球蛋白ATP酶的催化活性随温度升高而升高。在这里，我们研究了快速加热聚焦红外（IR）激光照射的影响，在体外运动试验中与人α-原肌球蛋白和牛心室肌钙蛋白重组的细丝滑动。我们进行高精度的分析测量温度的荧光强度的罗丹明鬼笔环肽标记的F-肌动蛋白加上荧光热敏片含有温度敏感染料铕（III）thenoyltrifluoroacetonate三水合物。这种方法能够在0.2秒内将温度从25摄氏度转变到46摄氏度。我们发现，在没有Ca 2+和ATP的存在下，IR激光照射eltered滑动运动的重组细丝的滑动速度，增加作为温度的函数。加热引起的细丝滑动加速同样发生在Ca 2+和ATP的存在下，然而，温度依赖性是两倍以上不太明显。这些发现可能表明，在哺乳动物心脏中，在生理体温下，心脏细丝状态的开-关平衡部分地向心脏中的开状态转移，从而使心脏收缩期的心肌动力学快速而有效。
During the excitation-contraction coupling of the heart, sarcomeres are activated via thin filament structural changes (i.e., from the "off" state to the "on" state) in response to a release of Ca2+ from the sarcoplasmic reticulum. This process involves chemical reactions that are highly dependent on ambient temperature; for example, catalytic activity of the actomyosin ATPase rises with increasing temperature. Here, we investigate the effects of rapid heating by focused infrared (IR) laser irradiation on the sliding of thin filaments reconstituted with human a-tropomyosin and bovine ventricular troponin in an in vitro motility assay. We perform high-precision analyses measuring temperature by the fluorescence intensity of rhodamine-phalloidin-labeled F-actin coupled with a fluorescent thermosensor sheet containing the temperature-sensitive dye Europium (III) thenoyltrifluoroacetonate trihydrate. This approach enables a shift in temperature from 25 degrees C to similar to 46 degrees C within 0.2 s. We find that in the absence of Ca2+ and presence of ATP, IR laser irradiation elicits sliding movements of reconstituted thin filaments with a sliding velocity that increases as a function of temperature. The heating-induced acceleration of thin filament sliding likewise occurs in the presence of Ca2+ and ATP; however, the temperature dependence is more than twofold less pronounced. These findings could indicate that in the mammalian heart, the on-off equilibrium of the cardiac thin filament state is partially shifted toward the on state in diastole at physiological body temperature, enabling rapid and efficient myocardial dynamics in systole.