Calpain-mediated proteolytic cleavage of troponin I induced by hypoxia or metabolic inhibition in cultured neonatal cardiomyocytes
Calpain-mediated proteolytic cleavage of troponin I induced by hypoxia or metabolic inhibition in cultured neonatal cardiomyocytes
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DOI：
10.1023/a:1007160702275
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发表时间：
2000-11-01
影响因子：
4.3
通讯作者：
Lee, TC
中科院分区：
文献类型：
--
作者：
Kositprapa, C;Zhang, BC;Lee, TC
虽然肌原纤维蛋白的缺血性损伤被认为是心脏功能低下的部分原因，但肌丝蛋白分解和慢性缺氧之间的关系尚未确定。我们先前表征了由1 mM叠氮化物介导的新生心肌细胞的化学缺氧模型，其表现出钙蛋白酶激活的特征（Mol Cell Biochem 178：141-149，1998）。我们发现缺氧和叠氮化物介导的代谢抑制均诱导血红素加氧酶-1表达，并导致与脂质过氧化相关的细胞死亡。虽然阻断钙内流或抑制钙蛋白酶活性有效地减弱缺氧诱导的细胞损伤，但它未能防止由肿瘤抑制蛋白p53的腺病毒过表达引起的细胞损伤。另一方面，半胱天冬酶抑制剂抑制p53过表达引起的细胞损伤。缺氧引起选择性切割肌钙蛋白I（TnI），这可以抑制硝苯地平或calpeptin。其他肌丝蛋白如肌钙蛋白T、肌球蛋白重链和肌动蛋白似乎基本保持完整。p53介导的细胞损伤表现出半胱天冬酶蛋白底物核纤层蛋白B的蛋白水解，而没有明显的TnI分解。我们认为钙蛋白酶诱导的肌钙蛋白I分解可能是一个独特的生化标志物与慢性缺氧心肌细胞。
While ischemic damage to myofibrillar proteins is thought to be responsible in part for depressed cardiac function, the relation between myofilament protein breakdown and chronic hypoxia has not been defined. We previously characterized a chemical hypoxia model of neonatal cardiomyocytes mediated by 1 mM azide that exhibits features of calpain activation (Mol Cell Biochem 178:141-149, 1998). We here show that both hypoxia and azide-mediated metabolic inhibition induced heme oxygenase-1 expression, and caused cell death associated with lipid peroxidation. While blocking calcium influx or inhibiting calpain activity efficiently attenuated hypoxia-induced cell injury, it failed to prevent cell injury caused by adenoviral overexpression of the tumor suppressor protein p53. Inhibitors of caspases, on the other hand, suppressed cell injury caused by p53 overexpression. Hypoxia caused selective cleavage of troponin I (TnI), which could be suppressed by either nifedipine or calpeptin. Other myofilament proteins such as troponin T, myosin heavy chain, and actin appeared to remain largely intact. p53-mediated cell injury exhibited proteolysis of the caspase protein substrate lamin B without appreciable breakdown of TnI. We suggest that calpain-induced TnI breakdown may constitute a unique biochemical marker associated with chronically hypoxic cardiomyocytes.