Role of calpain in the regulation of CFTR (cystic fibrosis transmembrane conductance regulator) turnover
Role of calpain in the regulation of CFTR (cystic fibrosis transmembrane conductance regulator) turnover
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DOI：
10.1042/bj20100344
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发表时间：
2010-09-01
影响因子：
4.1
通讯作者：
Melloni, Edon
中科院分区：
文献类型：
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作者：
Averna, Monica;Stifanese, Roberto;Melloni, Edon
质膜上成熟的天然 170 kDa 形式的 CFTR（囊性纤维化跨膜电导调节因子）的水平受到钙蛋白酶催化的选择性蛋白水解的控制。这种有限消化的产物由仍通过强相互作用结合的离散片段组成，从质膜上去除并内化在囊泡中并进行额外的降解。这一过程可以通过可视化增殖的人类白血病 T 细胞系和人类循环淋巴细胞中 100 kDa 片段的积累来监测。在重建系统和完整细胞中，天然 CFTR 转化为 100 kDa 片段与钙蛋白酶激活线性相关，并且通过添加合成钙蛋白酶抑制剂来阻止。通过阻断 NMDA（N-甲基-D-天冬氨酸）受体 Ca2+ 通道，Ca2+ 流入减少，抑制天然 170 kDa 片段向 100 kDa 片段的转化，而内体酸化阻断剂则促进消化的 100 kDa CFTR 形式的积累。 HSP90（热休克蛋白 90）在钙蛋白酶介导的 CFTR 周转中发挥着重要作用，它通过与蛋白质通道结合，通过选择性保护调节钙蛋白酶的降解作用。总而言之，这些结果表明 CFTR 周转是由钙蛋白酶激活引发的，钙蛋白酶激活是由 Ca2+ 流入增加诱导的，在裂解通道蛋白内化后，并由溶酶体蛋白酶完成。这些发现为人类病理中离子通道功能缺陷的分子机制提供了新的见解。
The level of the mature native 170 kDa form of CFTR (cystic fibrosis transmembrane conductance regulator) at the plasma membrane is under the control of a selective proteolysis catalysed by calpain. The product of this limited digestion, consisting of discrete fragments still associated by strong interactions, is removed from the plasma membrane and internalized in vesicles and subject to an additional degradation. This process can be monitored by visualizing the accumulation of a 100 kDa fragment in a proliferating human leukaemic T-cell line and in human circulating lymphocytes. In reconstructed systems, and in intact cells, the conversion of native CFTR into the 100 kDa fragment linearly correlated with calpain activation and was prevented by addition of synthetic calpain inhibitors. A reduction in Ca2+ influx, by blocking the NMDA (N-methyl-D-aspartate) receptor Ca2+ channel, inhibited the conversion of the native 170 kDa fragment into the 100 kDa fragment, whereas an endosome acidification blocker promoted accumulation of the digested 100 kDa CFTR form. An important role in calpain-mediated turnover of CFTR is exerted by HSP90 (heat-shock protein 90), which, via association with the protein channel, modulates the degradative effect of calpain through a selective protection. Taken together these results indicate that CFTR turnover is initiated by calpain activation, which is induced by an increased Ca2+ influx and, following internalization of the cleaved channel protein, and completed by the lysosomal proteases. These findings provide new insights into the molecular mechanisms responsible for the defective functions of ion channels in human pathologies.