Functional consequences of caspase activation in cardiac myocytes
Functional consequences of caspase activation in cardiac myocytes
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DOI：
10.1073/pnas.092022999
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发表时间：
2002-04-30
影响因子：
11.1
通讯作者：
Hajjar, RJ
中科院分区：
文献类型：
--
作者：
Communal, C;Sumandea, M;Hajjar, RJ
心肌细胞凋亡存在于许多心脏疾病状态中，包括心力衰竭和缺血性心脏病。细胞凋亡与介导生命蛋白和结构蛋白裂解的半胱天冬酶的激活有关。然而，细胞凋亡对这些病症的功能贡献尚不清楚。此外，在心肌细胞中，细胞凋亡可能不完全，使细胞在心肌内持续很长时间。因此，我们研究了caspase-3是否切割心肌肌原纤维蛋白，如果是，它是否影响收缩功能。在体外研究了半胱天冬酶-3对心肌肌丝的各个组分的影响，包括α-肌动蛋白、α-辅肌动蛋白、肌球蛋白重链、肌球蛋白轻链1/2、原肌球蛋白、心肌肌钙蛋白（T、I、Q）和三聚体肌钙蛋白复合物。将肌原纤维蛋白（如上所列）暴露于胱天蛋白酶-3 4小时，导致α-肌动蛋白和α-辅肌动蛋白裂解，但肌球蛋白重链、肌球蛋白轻链1/2和原肌球蛋白不裂解，分别裂解为三个片段（30、20和15 kDa）和一个主要片段（45 kDa）。当cTnT、cTnI和cTnC分别与caspase-3孵育时，未检测到切割。然而，当重组肌钙蛋白复合物暴露于胱天蛋白酶-3时，cTnT被切割，产生25 kDa的片段。此外，大鼠心肌肌丝暴露于caspase-3表现出类似的肌原纤维蛋白裂解模式。用半胱天冬酶抑制剂DEVD-CHO或z-VAD-favorite处理消除了切割。从成年大鼠心室肌细胞中分离出的肌丝，在通过β-肾上腺素能刺激诱导凋亡途径后，显示出类似的肌动蛋白和TnT裂解模式。暴露于caspase-3的皮肤纤维的最大Ca 2+激活力和肌原纤维ATP酶活性下降。我们的研究结果表明，caspase-3裂解肌原纤维蛋白，导致力/Ca 2+关系和肌原纤维ATP酶活性受损。心肌细胞凋亡的诱导与类似的肌丝分裂有关。因此，凋亡途径的激活可能导致细胞死亡前的收缩功能障碍。
Cardiomyocyte apoptosis is present in many cardiac disease states, including heart failure and ischemic heart disease. Apoptosis is associated with the activation of caspases that mediate the cleavage of vital and structural proteins. However, the functional contribution of apoptosis to these conditions is not known. Furthermore, in cardiac myocytes, apoptosis may not be complete, allowing the cells to persist for a prolonged period within the myocardium. Therefore, we examined whether caspase-3 cleaved cardiac myofibrillar proteins and, if so, whether it affects contractile function. The effects of caspase-3 were studied in vitro on individual components of the cardiac myofilament including a-actin, a-actinin, myosin heavy chain, myosin light chain 1/2, tropomyosin, cardiac troponins (T, 1, Q, and the trimeric troponin complex. Exposure of the myofibrillar protein (listed above) to caspase-3 for 4 h resulted in the cleavage of a-actin and a-actinin, but not myosin heavy chain, myosin light chain 1/2, and tropomyosin, into three fragments (30, 20, and 15 kDa) and one major fragment (45 kDa), respectively. When cTnT, cTnI, and cTnC were incubated individually with caspase-3, there was no detectable cleavage. However, when the recombinant troponin complex was exposed to caspase-3, cTnT was cleaved, resulting in fragments of 25 kDa. Furthermore, rat cardiac myofilaments exposed to caspase-3 exhibited similar patterns of myofibrillar protein cleavage. Treatment with the caspase inhibitor DEVD-CHO or z-VAD-fmk abolished the cleavage. Myofilaments, isolated from adult rat ventricular myocytes after induction of apoptotic pathway by using beta-adrenergic stimulation, displayed a similar pattern of actin and TnT cleavage. Exposure of skinned fiber to caspase-3 decreased maximal Ca2+-activated force and myofibrillar ATPase activity. Our results indicate that caspase-3 cleaved myofibrillar proteins, resulting in an impaired force/Ca2+ relationship and myofibrillar ATPase activity. Induction of apoptosis in cardiac cells was associated with similar cleavage of myofilaments. Therefore, activation of apoptotic pathways may lead to contractile dysfunction before cell death.