National Hellenic Research Foundation, Institute of Biological Research and Biotechnology, Athens 11635, Greece.
Free Radic Biol Med. 2011 Jan 1;50(1):157-65. doi: 10.1016/j.freeradbiomed.2010.10.701. Epub 2010 Oct 23.
p53 regulates several biological processes, including senescence. Its protein stability is regulated by ubiquitination and proteasomal degradation, mainly mediated by Mdm2. However, other E3 ligases have been identified, such as the chaperone-associated ligase CHIP, although their precise function regarding p53 degradation remains elusive. Interestingly, CHIP deficiency has been recently shown to result in accelerated aging in mice, although the molecular basis of this phenotype was not completely understood. In this study, we explore the role of CHIP in regulating p53 in senescence. We demonstrate that in senescent human fibroblasts, CHIP is up-regulated concomitant with a significant down-regulation of p53. Moreover, CHIP partially translocates to the nucleus and acquires higher ubiquitination levels in senescent cells. Notably, CHIP overexpression in young cells, to levels similar to those recorded during senescence, leads to p53 degradation to below its basal levels. In addition, whereas CHIP silencing has no effect on p53 stability in young cells, a considerable p53 accumulation occurs in their senescent counterparts. Finally, we have observed an attenuation of the CHIP-associated molecular folding-refolding machinery during senescence, and supportively, inhibition of Hsp90 activity leads to rapid p53 degradation only in senescent cells. Taking these results together, we conclude that CHIP-dependent p53 regulation occurs specifically during senescence.
p53 调节多种生物过程，包括衰老。其蛋白稳定性受泛素化和蛋白酶体降解调节，主要由 Mdm2 介导。然而，已经鉴定出其他 E3 连接酶，例如伴侣相关连接酶 CHIP，尽管它们在 p53 降解方面的确切功能仍不清楚。有趣的是，最近的研究表明 CHIP 缺乏会导致小鼠加速衰老，尽管这种表型的分子基础尚未完全理解。在这项研究中，我们探讨了 CHIP 在调节衰老过程中 p53 的作用。我们证明在衰老的人成纤维细胞中，CHIP 上调，同时 p53 显著下调。此外，CHIP 部分易位到细胞核，并在衰老细胞中获得更高的泛素化水平。值得注意的是，在年轻细胞中过表达 CHIP，使其水平与衰老过程中记录的水平相似，会导致 p53 降解至低于其基础水平。此外，尽管 CHIP 沉默对年轻细胞中 p53 的稳定性没有影响，但在衰老的细胞中会发生相当大的 p53 积累。最后，我们观察到衰老过程中 CHIP 相关分子折叠-重折叠机制的衰减，并且支持性地，抑制 Hsp90 活性仅在衰老细胞中导致 p53 迅速降解。综合这些结果，我们得出结论，CHIP 依赖性 p53 调节仅在衰老过程中发生。
