Redox-regulated cochaperone activity of the human DnaJ homolog Hdj2

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• 作者：Hoon-In Choi ; Sang Pil Lee ; Kyung Soon Kim ; Chae Young Hwang ; Yu-Ran Lee ; Suhn-Kee Chae ; Yeon-Soo Kim ; Ho Zoon Chae and Ki-Sun Kwon
• 关键词：Oxidative stress ; Protein folding ; Chaperone ; Zinc finger ; Thioredoxin ; Free radical
• 刊名：Free Radical Biology and Medicine
• 出版年：2006
• 出版时间：15 February 2006
• 年：2006
• 卷：40
• 期：4
• 页码：651-659
• 全文大小：529 K

文摘

The human DnaJ homolog Hdj2 is a cochaperone containing a cysteine-rich zinc finger domain. We identified a specific interaction of Hdj2 with the cellular redox enzyme thioredoxin using a yeast two-hybrid assay and a coimmunoprecipitation assay, thereby investigating how the redox environment of the cell regulates Hdj2 function. In reconstitution experiments with Hsc70, we found that treatment with H₂O₂ caused the oxidative inactivation of Hdj2 cochaperone activity. Hdj2 inactivation paralleled the oxidation of cysteine thiols and concomitant release of coordinated zinc, suggesting a role of cysteine residues in the zinc finger domain of Hdj2 as a redox sensor of chaperone-mediated protein-folding machinery. H₂O₂-induced negative regulation of Hdj2 cochaperone activity was also confirmed in mammalian cells using luciferase as a foreign reporter cotransfected with Hsc70 and Hdj2. The in vivo oxidation of cysteine residues in Hdj2 was detected only in thioredoxin-knockdown cells, implying that thioredoxin is involved in the in vivo reduction. The oxidative inactivation of Hdj2 was reversible. Wild-type thioredoxin notably recovered the oxidatively inactivated Hdj2 activity accompanied by the reincorporation of zinc, whereas the catalytically inactive mutant thioredoxin (Cys32Ser/Cys35Ser) did not. Taken together, we propose that oxidation and reduction reversibly regulate Hdj2 function in response to the redox states of the cell.