Wells Center for Pediatric Research, Department of Pediatrics, Indiana University, 980 W. Walnut St., Indianapolis, IN 46202, USA.
Cell Signal. 2012 Jun;24(6):1222-8. doi: 10.1016/j.cellsig.2012.02.004. Epub 2012 Feb 18.
Hedgehog (Hh) signaling, via the key signal transducer Smoothened (SMO) and Gli transcription factors, is essential for embryonic development and carcinogenesis. While the biological relevance of hedgehog signaling to cancer is well established, very little is known about the molecular mechanisms by which signaling transduction of this pathway occurs. Rab23 was discovered as a negative regulator of the Hh pathway through a mouse genetic study. Here we report that Rab23 directly associates with Su(Fu) and inhibits Gli1 function in a Su(Fu)-dependent manner. By confocal microscope and immunoprecipitation, we detected interaction between Rab23 and Su(Fu). Using Gli1-mediated reporter gene analysis, we found that Rab23 can suppress Gli1 transcriptional activity in wild type but not Su(Fu) null fibroblasts. Similarly, Rab23 expression reduced the nuclear localization of Gli1 in wild type but not Su(Fu) null fibroblast cells. Consistent with the GTPase motif in the protein, we showed that Rab23 has GTPase activity. The dominant negative form of Rab23 was unable to suppress Gli1-mediated transcriptional activity. Taken together, these data provide evidence to support that Rab23 negatively regulates Gli1 activity in a Su(Fu)-dependent manner.
刺猬 (Hh) 信号通过关键信号转导 Smoothened (SMO) 和 Gli 转录因子对于胚胎发育和癌发生是必不可少的。虽然刺猬信号对癌症的生物学相关性已经得到很好的确立，但对于该途径信号转导发生的分子机制知之甚少。Rab23 是通过一项小鼠遗传研究作为刺猬途径的负调节剂被发现的。在这里，我们报告 Rab23 与 Su(Fu) 直接相关，并以 Su(Fu) 依赖性方式抑制 Gli1 功能。通过共聚焦显微镜和免疫沉淀，我们检测到 Rab23 和 Su(Fu) 之间的相互作用。使用 Gli1 介导的报告基因分析，我们发现 Rab23 可以在野生型但不能在 Su(Fu) 缺失成纤维细胞中抑制 Gli1 转录活性。同样，Rab23 的表达减少了野生型而非 Su(Fu) 缺失成纤维细胞中 Gli1 的核定位。与该蛋白中的 GTPase 基序一致，我们表明 Rab23 具有 GTPase 活性。Rab23 的显性失活形式不能抑制 Gli1 介导的转录活性。总之，这些数据提供了证据支持 Rab23 以 Su(Fu) 依赖性方式负调节 Gli1 活性。
