Reciprocal targeting of Hath1 and β-catenin by wnt glycogen synthase kinase 3β in human colon cancer
Reciprocal targeting of Hath1 and β-catenin by wnt glycogen synthase kinase 3β in human colon cancer
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DOI：
10.1053/j.gastro.2006.10.031
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发表时间：
2007-01-01
期刊：
影响因子：
29.4
通讯作者：
Watanabe, Mamoru
中科院分区：
文献类型：
--
作者：
Tsuchiya, Kiichiro;Nakamura, Tetsuya;Watanabe, Mamoru
背景与目的：转录因子Hath1在人肠道上皮分化过程中起着至关重要的作用。本研究旨在探讨人类结肠细胞Writ通路下Hath1表达的分子机制及其与β -连环蛋白/糖原合成酶激酶3 β (GSK3 β)的密切关系。方法：采用Northern blot法检测人体组织中Hath1信使RNA的组织分布。通过在人细胞系中表达flag标记的Hath1，分析了Hath1蛋白的稳定性。通过特异性抑制GSK-3 β功能来确定GSK3 β靶向Hath1蛋白。免疫组化法检测结直肠癌组织中Hath1蛋白的表达。结果：人成人组织中Hath1信使RNA的表达仅限于下胃肠道。在结肠癌细胞中，虽然也检测到Hath1信使RNA，但Hath1蛋白被蛋白酶体介导的蛋白水解正向降解。令人惊讶的是，GSK3 β依赖性蛋白降解通过Writ信号在Hath1和β -catenin之间切换，分别导致细胞状态在增殖和分化之间发生巨大变化。仅在正常结肠组织中检测到Hath1蛋白，而在存在核定位β -连环蛋白的癌症组织中未检测到Hath1蛋白。结论：本研究提示了典型Wnt信号在人结肠癌细胞中的新功能，分别通过GSK3 β介导的β -catenin或Hath1的相互降解调节细胞增殖和分化，进一步强调了异常Wnt信号在结肠细胞转化中的重要性。
Background & Aims: The transcription factor Hath1 plays a crucial role in the differentiation program of the human gut epithelium. The present study was conducted to investigate the molecular mechanism of Hath1 expression and its close association with beta-catenin/glycogen synthase kinase 3 beta (GSK3 beta) under the Writ pathway in human colonocytes. Methods: Tissue distribution of Hath1 messenger RNA in human tissues was examined by Northern blot. Stability of Hath1 protein was analyzed by expression of FLAG-tagged Hath1 in human cell lines. Targeting of Hath1 protein by GSK3 beta was determined by specific inhibition of GSK-3 beta function. Expression of Hath1 protein in colorectal cancers was examined by immunohistochemistry. Results: Hath1 messenger RNA expression was confined to the lower gastrointestinal tract in human adult tissues. In colon cancer cells, although Hath1 messenger RNA was also detected, Hath1 protein was positively degradated by proteasome-mediated proteolysis. Surprisingly, the GSK3 beta-dependent protein degradation was switched between Hath1 and beta-catenin by Writ signaling, leading to the dramatic alteration of cell status between proliferation and differentiation, respectively. Hath1 protein was detected exclusively in normal colon tissues but not in cancer tissues, where nuclear-localized beta-catenin was present. Conclusions: The present study suggests a novel function of the canonical Writ signaling in human colon cancer cells, regulating cell proliferation and differentiation by GSK3 beta-mediated, reciprocal degradation of beta-catenin or Hath1, respectively, which further emphasizes the importance of aberrant Wnt signaling in colonocyte transformation.