Role of the cytosolic chaperones Hsp70 and Hsp90 in maturation of the cardiac potassium channel hERG
Role of the cytosolic chaperones Hsp70 and Hsp90 in maturation of the cardiac potassium channel hERG
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DOI：
10.1161/01.res.0000079028.31393.15
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发表时间：
2003-06-27
影响因子：
20.1
通讯作者：
Brown, AM
中科院分区：
文献类型：
--
作者：
Ficker, E;Dennis, AT;Brown, AM
人类乙醚-a-GOGO相关基因(HERG)编码心肌钾电流I-Kr的α亚基。HERG的几个突变产生运输缺陷的通道，可能导致遗传性长QT综合征和心脏性猝死。虽然HERG电流已被广泛研究，但对参与HERG成熟和运输的蛋白质知之甚少。利用免疫沉淀，我们发现在成熟过程中，胞浆伴侣热休克蛋白(HSP)70和HSP90，而不是Grp94与Herg野生型(WT)相互作用。特定的Hsp90抑制剂格尔达那霉素阻止HERG WT的成熟并增加其蛋白酶体的降解，同时减少异源表达系统中的HERG电流。在心室肌细胞中，抑制Hsp90也可降低I-Kr，而格尔达霉素对I-Ks无影响或异源表达Kv2.1和Kv1.5电流。Hsp90和Hsp70都直接与内质网中存在的核心糖基化形式的Herg WT相互作用，但不与完全糖化的细胞表面形式相互作用。对于运输缺陷的LQT2突变体，Herg R752W和Herg G601S与Hsp90和Hsp70的相互作用增加，因为这两个突变体都与内质网中的Hsp90和Hsp70紧密相关。在较低温度下孵育R752W或与HERG阻滞剂阿司咪唑孵育G601S可解离通道-伴侣复合体，恢复转运。相反，无功能但具有贩运能力的Herg G628S在成熟过程中从伴侣复合体中释放出来，与WT相当。我们得出结论，Hsp90和Hsp70对于Herg WT的成熟以及运输缺陷LQT2突变体的保留至关重要。本文全文可在网上查阅，网址为：http://www.circresaha.org.
The human ether-a-gogo-related gene (hERG) encodes the alpha subunit of the cardiac potassium current I-Kr. Several mutations in hERG produce trafficking-deficient channels that may cause hereditary long-QT syndrome and sudden cardiac death. Although hERG currents have been studied extensively, little is known about the proteins involved in maturation and trafficking of hERG. Using immunoprecipitations, we show that the cytosolic chaperones heat shock protein (Hsp) 70 and Hsp90, but not Grp94, interact with hERG wild type (WT) during maturation. The specific Hsp90 inhibitor geldanamycin prevents maturation and increases proteasomal degradation of hERG WT, while reducing hERG currents in heterologous expression systems. In ventricular myocytes, inhibition of Hsp90 also decreases I-Kr, whereas geldanamycin had no effect on I-Ks or heterologously expressed Kv2.1 and Kv1.5 currents. Both Hsp90 and Hsp70 interact directly with the core-glycosylated form of hERG WT present in the endoplasmic reticulum but not the fully glycosylated, cell-surface form. For the trafficking-deficient LQT2 mutants, hERG R752W and hERG G601S, interactions with Hsp90 and Hsp70 are increased as both mutants remained tightly associated with Hsp90 and Hsp70 in the endoplasmic reticulum. Incubation at lower temperature for R752W or with the hERG blocker astemizole for G601S dissociates channel-chaperone complexes and restores trafficking. In contrast, nonfunctional but trafficking-competent hERG G628S is released from chaperone complexes during maturation comparable to WT. We conclude that Hsp90 and Hsp70 are crucial for the maturation of hERG WT as well as the retention of trafficking-deficient LQT2 mutants. The full text of this article is available online at http://www.circresaha.org.