RPGRIP1L调控桥粒形成的机理

Desmosome is a type of cell-cell junction, and abnormalities in desmosomes can cause pemphigus in the skin or arrhythmogenic right ventricular cardiomyopathy in the heart. RPGRIP1L is known to participate in cilia formation. We found that in epidermal keratinocyes, RPGRIP1L not only controls primary cilia formation but also participates in desmosome formation. Disrupting the mouse Rpgrip1l gene can cause interepidermal blistering, reminiscent that of pemphigus vulgaris. Transmission electron microscopy demonstrated abnormal desmosome ultrastructure. In vitro studies showed that knocking down RPGRIP1L can accelerated internalization of desmoglein, by which the homeostasis of assembly and disassembly of the desmosomes are impaired. These findings suggest the RPGRIP1L is required for stabilizing desmosome through desmoglein. This proposal is aimed at understanding the molecular mechanism of RPGRIP1L-mediated desmosome formation. We will focus our study on potential physical interaction between RPGRIP1L and desmosomal proteins, how RPGRIP1L participates in desmosome stability through regulating desmoglein internalization, and whether RPGRIP1L indirectly control demosome formation through regulating the ubiquitin-proteasome system. This study will not only expand the molecular functions of RPGRIP1L, and establishing a new member of the desmosome family, but also provide insight into mechanism associated desmosomal diseases.

桥粒是一种细胞之间连接，其异常可导致天疱疮或致心律失常性右室心肌病。RPGRIP1L是一个参与纤毛形成的蛋白。我实验组发现RPGRIP1L不仅可以调节纤毛形成，而且参与表皮角质形成细胞间桥粒的形成。RPGRIP1L基因敲除会导致小鼠的表皮内出现由细胞粘附障碍引发的、类似天疱疮的表皮内疱。电镜显示RPGRIP1L的缺失在超微结构上导致桥粒形态异常。体外试验揭示RPGRIP1L的缺失会导致桥粒芯糖蛋白的加速内吞，进而打破桥粒形成和解聚平衡，提示RPGRIP1L对桥粒芯糖蛋白有固化作用。本项目将探索RPGRIP1L参与桥粒形成的分子机制。主要研究内容包括RPGRIP1L与桥粒组成蛋白之间作用，桥粒蛋白的稳态以及桥粒芯糖蛋白的内吞，泛素-蛋白酶系统与桥粒蛋白的稳定性。此课题不仅扩展了RPGRIP1L的分子功能，为桥粒研究提供新的方向，并且可为与桥粒相关的疾病提供理论基础。

桥粒是一种细胞之间连接，其异常可导致天疱疮或致心律失常性右室心肌病。RPGRIP1L是一个参与纤毛形成的蛋白。我实验组发现RPGRIP1L不仅可以调节纤毛形成，而且参与表皮角质形成细胞间桥粒的形成。RPGRIP1L基因敲除会导致小鼠的表皮内出现由细胞粘附障碍引发的、类似天疱疮的表皮内疱。本项目中发现干扰不形成纤毛的HaCaT细胞的RPGRIP1L基因的表达，会导致桥粒结构蛋白错误定位于细胞质，该发现表明了RPGRIP1L蛋白具有独立于纤毛的新功能。我们发现在角质形成细胞中抑制RPGRIP1L的表达，会异常加速桥粒芯糖蛋白的内吞，且抑制细胞的内吞作用能够有效地缓解抑制RPGRIP1L造成的细胞粘附异常。另外我们还发现抑制RPGRIP1L的表达还会加重EGTA-或PV IgG（寻常天疱疮IgG）诱导的桥粒芯糖蛋白的内吞，且使用抑制剂或蔗糖抑制细胞胞吞作用能够有效地挽救其桥粒异常的表型。细胞表面蛋白的生物素化检测提示RPGRIP1L可能更广泛地参与细胞内吞作用的调节。本研究发现RPGRIP1L不仅是桥粒的调节因子，而且扩大了我们对桥粒连接形成过程中纤毛相关蛋白的理解。