Molecular cloning and function of CD44 cytoplasmic domain associated molecules

为了阐明CD44在炎症和癌症中的作用，采用酵母双杂交系统对HeLa细胞的CD44胞浆结构域相关分子进行了研究。分离了RanBPM和hMena的DNA片段，并从HeLa细胞的cDNA文库中克隆了它们的cDNA。将RanBPM的短干扰RNA导入HeLa S3细胞，可抑制CD44刺激下的细胞运动，而转染hMena的si-RNA可诱导细胞运动而不受任何刺激。两种siRNAs都影响Rho GTP酶的激活和皮质F-肌动蛋白的形成。这些结果表明，CD44分子介导了Rho GTP酶的激活，进而调节了皮质F-肌动蛋白的组装。因此，我们的研究表明，CD44通过Rho GTP酶信号调节细胞的形态和运动。我们还检测了CD44在酵母多糖诱导的CD44(/)和(-/-)小鼠关节炎中的作用。与CD44(/)小鼠相比，CD44(-/-)小鼠总是出现严重的炎症反应。在关节炎的发病过程中，CD44(-/-)小鼠的Toll样受体对核因子κB的信号转导较野生型小鼠增强。我们的研究结果表明，CD44分子通过与位于细胞膜和/或细胞质中的分子相互作用，在炎症和肿瘤细胞行为的调控中发挥关键作用。进一步深入研究CD44的作用机制将为炎症和肿瘤的分子靶向治疗提供有用的信息。

To elucidate the role of CD44 in the inflammation and cancer, the molecules associated with cytoplasmic domain of CD44 were surveyed in HeLa cell cDNA library by yeast-two hybrid system. DNA fragments of RanBPM and hMena were isolated and, then, their cDNAs were cloned from HeLa cell cDNA library. Transfection of short interference RNA from RanBPM into HeLa S3 cells suppressed the cell motility on CD44 stimulation, whereas transfection of si-RNA from hMena induced the cell motility without any stimulation. Both siRNAs affected on the activation of Rho GTPases and the formation of cortical F-actin. These results indicate that CD44 molecule mediates the Rho GTPases activation and, then, modulates cortical F-actin assembly. Thus, our study showed that CD44 would regulate cell shape and motility through Rho GTPase signaling. We also examined the role of CD44 in zymosan-induced arthritis of CD44 (+/+) and (-/-) mice. The severe inflammatory response was always found in CD44 (-/-) mice compared to CD44 (+/+) mice. In the process of the arthritis, the signaling from Toll-like receptors to NFκB was enhanced in CD44 (-/-) mice compared to wild mice. Our results indicate that CD44 would regulate the Toll-like receptor signaling.Summary : Our studies showed that CD44 molecule play a pivotal role on the regulation of inflammation and tumor cell behavior through its interaction with molecules residing at the plasma membrane and/or in the cytoplasm. Further precise study of the mechanism of CD44 action will provide the useful information of molecular target therapy in inflammation and cancer.