From the Vascular Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Departments of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Biol Chem. 2010 Feb 5;285(6):3651-3663. doi: 10.1074/jbc.M109.068577. Epub 2009 Nov 23.
Hypoxia-inducible factors (HIFs) are transcription factors that mediate adaptive responses to reduced oxygen availability. HIF-alpha subunits are stabilized under conditions of acute hypoxia. However, prolonged hypoxia leads to decay of HIF-1alpha but not HIF-2alpha protein levels by unknown mechanisms. Here, we identify Hsp70 and CHIP (carboxyl terminus of Hsc70-interacting protein) as HIF-1alpha-interacting proteins. Hsp70, through recruiting the ubiquitin ligase CHIP, promotes the ubiquitination and proteasomal degradation of HIF-1alpha but not HIF-2alpha, thereby inhibiting HIF-1-dependent gene expression. Disruption of Hsp70-CHIP interaction blocks HIF-1alpha degradation mediated by Hsp70 and CHIP. Inhibition of Hsp70 or CHIP synthesis by RNA interference increases protein levels of HIF-1alpha but not HIF-2alpha and attenuates the decay of HIF-1alpha levels during prolonged hypoxia. Thus, Hsp70- and CHIP-dependent ubiquitination represents a molecular mechanism by which prolonged hypoxia selectively reduces the levels of HIF-1alpha but not HIF-2alpha protein.
缺氧诱导因子(HIFs)是转录因子,可介导对氧供应减少的适应性反应。在急性缺氧条件下,HIF-α亚基稳定。然而,通过未知机制,长期缺氧会导致 HIF-1α 而非 HIF-2α 蛋白水平的衰减。在这里,我们确定 Hsp70 和 CHIP(Hsc70 相互作用蛋白的羧基末端)为 HIF-1α 相互作用蛋白。Hsp70 通过招募泛素连接酶 CHIP,促进 HIF-1α 的泛素化和蛋白酶体降解,但不促进 HIF-2α 的降解,从而抑制 HIF-1 依赖性基因表达。破坏 Hsp70-CHIP 相互作用会阻止 Hsp70 和 CHIP 介导的 HIF-1α 降解。通过 RNA 干扰抑制 Hsp70 或 CHIP 的合成会增加 HIF-1α 但不增加 HIF-2α 的蛋白水平,并减轻长期缺氧期间 HIF-1α 水平的衰减。因此,Hsp70 和 CHIP 依赖性泛素化代表了一种分子机制,通过该机制,长期缺氧选择性降低 HIF-1α 而非 HIF-2α 蛋白水平。