Molecular cloning and function of CD44 cytoplasmic domain associated molecules

为了阐明CD 44在炎症和肿瘤中的作用，本研究利用酵母双杂交技术，从HeLa细胞cDNA文库中筛选CD 44胞浆区相关分子。从HeLa细胞cDNA文库中克隆RanBPM和hMena的cDNA。将RanBPM的短干扰RNA转染到HeLa S3细胞中抑制了CD 44刺激下的细胞运动，而转染hMena的si-RNA诱导细胞运动而没有任何刺激。两种siRNA均影响Rho GTPases的激活和皮质F-肌动蛋白的形成。这些结果表明，CD 44分子介导的Rho GTP酶激活，然后，调节皮质F-肌动蛋白组装。因此，我们的研究表明，CD 44将通过Rho GT3信号调节细胞的形状和运动性。我们还研究了CD 44在酵母多糖诱导的CD 44（+/+）和（-/-）小鼠关节炎中的作用。与CD 44（+/+）小鼠相比，CD 44（-/-）小鼠总是发现严重的炎症反应。与野生型小鼠相比，CD 44（-/-）小鼠关节炎过程中Toll样受体向NFκB的信号传导增强。我们的研究表明，CD 44分子通过与细胞膜和/或细胞质中的分子相互作用，在炎症和肿瘤细胞行为的调节中发挥关键作用。对CD 44作用机制的深入研究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.