Department of Medicine, Weill Cornell Medical College, New York, New York 10065.
Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853.
J Biol Chem. 2014 Mar 7;289(10):6513-6525. doi: 10.1074/jbc.M113.532523. Epub 2014 Jan 22.
The p53 tumor suppressor gene encodes a homotetrameric transcription factor which is activated in response to a variety of cellular stressors, including DNA damage and oncogene activation. p53 mutations occur in >50% of human cancers. Although p53 has been shown to regulate Wnt signaling, the underlying mechanisms are not well understood. Here we show that silencing p53 in colon cancer cells led to increased expression of Aha1, a co-chaperone of Hsp90. Heat shock factor-1 was important for mediating the changes in Aha1 levels. Increased Aha1 levels were associated with enhanced interactions with Hsp90, resulting in increased Hsp90 ATPase activity. Moreover, increased Hsp90 ATPase activity resulted in increased phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β), leading to enhanced expression of Wnt target genes. Significantly, levels of Aha1, Hsp90 ATPase activity, Akt, and GSK3β phosphorylation and expression of Wnt target genes were increased in the colons of p53-null as compared with p53 wild type mice. Using p53 heterozygous mutant epithelial cells from Li-Fraumeni syndrome patients, we show that a monoallelic mutation of p53 was sufficient to activate the Aha1/Hsp90 ATPase axis leading to stimulation of Wnt signaling and increased expression of Wnt target genes. Pharmacologic intervention with CP-31398, a p53 rescue agent, inhibited recruitment of Aha1 to Hsp90 and suppressed Wnt-mediated gene expression in colon cancer cells. Taken together, this study provides new insights into the mechanism by which p53 regulates Wnt signaling and raises the intriguing possibility that p53 status may affect the efficacy of anticancer therapies targeting Hsp90 ATPase.
p53 肿瘤抑制基因编码一种同源四聚体转录因子，该因子在响应多种细胞应激物（包括 DNA 损伤和癌基因激活）时被激活。p53 突变发生在超过 50%的人类癌症中。尽管已经表明 p53 调节 Wnt 信号通路，但潜在的机制尚不清楚。在这里，我们显示在结肠癌细胞中沉默 p53 导致 Aha1 的表达增加，Aha1 是 Hsp90 的共伴侣。热休克因子-1对于介导 Aha1 水平的变化很重要。Aha1 水平的增加与与 Hsp90 的增强相互作用有关，导致 Hsp90 ATP 酶活性增加。此外，增加的 Hsp90 ATP 酶活性导致 Akt 和糖原合酶激酶-3β（GSK3β）的磷酸化增加，从而导致 Wnt 靶基因的表达增强。重要的是，与 p53 野生型小鼠相比，p53 缺失的结肠中 Aha1、Hsp90 ATP 酶活性、Akt 和 GSK3β 磷酸化以及 Wnt 靶基因的表达水平均增加。使用来自 Li-Fraumeni 综合征患者的 p53 杂合突变上皮细胞，我们表明 p53 的单等位基因突变足以激活 Aha1/Hsp90 ATP 酶轴，从而刺激 Wnt 信号通路并增加 Wnt 靶基因的表达。用 CP-31398（一种 p53 挽救剂）进行药物干预抑制了 Aha1 向 Hsp90 的募集，并抑制了结肠癌细胞中的 Wnt 介导的基因表达。总之，这项研究提供了新的见解，了解 p53 调节 Wnt 信号通路的机制，并提出了一个有趣的可能性，即 p53 状态可能影响针对 Hsp90 ATP 酶的抗癌治疗的疗效。
