多囊蛋白2离子通道功能及在常染色体显性多囊肾发病中的作用机制

多囊蛋白2 (polycystin-2,PC2,或称TRPP2,PKD2)是一种瞬时受体电位通道(transient receptor potential channel,TRP),在维持细胞正常的Ca²⁺信号传导中起着关键作用,也是最常见的单基因常染色体显性遗传多囊肾病(transient receptor potential channel,ADPKD)的潜在病因之一。PC2可自身组装为同源四聚体离子通道或与其他蛋白质形成异源受体-离子通道复合物,参与调节机械感觉、细胞极性、细胞增殖和凋亡等多种生理功能,导致囊性细胞从正常的吸收、静止状态转变为病理性分泌、增殖状态。本文阐述了PC2蛋白相关结构域以及通道特性在维持细胞内Ca²⁺信号传导中的关键作用,并总结了PC2在细胞膜、纤毛、内质网以及线粒体等特定亚细胞定位形成多囊蛋白复合物,参与多种细胞分化、增殖、存活和凋亡相关信号通路,为确定特异性的有效的ADPKD干预治疗途径和靶点药物提供新的思考方向。

Polycystin-2 Ion Channel Function and Pathogenesis in Autosomal Dominant Polycystic Kidney

Polycystin-2 (also known as PC2, TRPP2, PKD2) is a major contributor to the underlying etiology of autosomal dominant polycystic kidney disease (ADPKD), which is the most prevalent monogenic kidney disease in the world. As a transient receptor potential (TRP) channel protein, PC2 exhibits cation-permeable, Ca²⁺-dependent channel properties, and plays a crucial role in maintaining normal Ca²⁺ signaling in systemic physiology, particularly in ADPKD chronic kidney disease. Structurally, PC2 protein consists of six transmembrane structural domains (S1-S6), a polycystin-specific “tetragonal opening for polycystins” (TOP) domain located between the S1 and S2 transmembrane structures, and cytoplasmic N- and C-termini. Although the cytoplasmic N-terminus and C-terminus of PC2 may not be significant in the gating of PC2 channels, there is still much protein structural information that needs to be thoroughly investigated, including the regulation of channel function and the assembly of homotetrameric ion channels. This is further supported by the presence of human disease-associated mutation sites on the PC2 structure. Moreover, PC2 synthesized in the endoplasmic reticulum is enriched in specific subcellular localization via membrane transport and can assemble itself into homotetrameric ion channels, as well as form heterotrimeric receptor-ion channel complexes with other proteins. These complexes are involved in a wide range of physiological functions, including the regulation of mechanosensation, cell polarity, cell proliferation, and apoptosis. In particular, PC2 assembles with chaperone proteins to form polycystic protein complexes that affect Ca²⁺ transport in cell membranes, cilia, endoplasmic reticulum, and mitochondria, and are involved in activating cell fate-related signaling pathways, particularly cell differentiation, proliferation, survival, and apoptosis, and more recently, autophagy. This leads to a shift of cystic cells from a normal uptake, quiescent state to a pathologically secreted, proliferative state. In conclusion, the complex structural and functional roles of PC2 highlight its critical importance in the pathogenesis of ADPKD, making it a promising target for therapeutic intervention.