Regulation and Function of Uroplankin Genes

哺乳动物尿路上皮的顶端表面几乎完全被坚硬的尿路上皮斑块覆盖，这些斑块由六边形包装成二维晶体的16 nm尿斑蛋白颗粒组成。高度纯化的尿路上皮斑由四种主要的尿斑蛋白（UP）组成，即，尿斑蛋白Ia（27 kDa）、Ib（28 kDa）、II（15 kDa）和III（47 kDa）。两个四跨膜蛋白成员UPIa和UPIb分别优先与两个单一的跨膜域尿斑蛋白II和III相互作用，形成两个尿斑蛋白对 由UPIa/II和UPIb/III组成。在最后一次资助期间，我们从基因上消除了编码uroplakins II和III的小鼠基因。缺乏这两种主要尿路上皮分化产物的小鼠具有严重异常的尿路上皮，缺乏典型的伞细胞;具有异常小的尿路上皮斑块;并且患有膀胱输尿管反流、肾积水，并且在某些情况下，新生儿死亡。这些结果表明，uroplakins的尿路上皮斑块，这有助于渗透性屏障功能的组成亚基，和尿路上皮缺陷可能在某些尿路疾病中发挥作用。然而，关于尿斑蛋白缺陷如何影响尿路上皮和膀胱的整体功能，尿斑蛋白如何与尿斑蛋白相互作用， 细胞质和其他膜相关蛋白质，以及尿路致病细菌的尿斑蛋白受体的表面可及性。本项目拟开展的研究将试图回答其中一些问题，通过研究uroptakin基因的缺失如何影响膀胱的渗透性屏障和排尿功能（目的1）; uroptakin如何与一些可能在介导uropaldn中发挥作用的细胞质蛋白相互作用：细胞间相互作用和信号转导（目的2）;尿斑蛋白分子在尿路上皮伞细胞顶面的可及性，以及是否有其他尿斑蛋白相关的 细胞表面蛋白质，可能与尿路上皮“糖萼”涂层， 假设在几种膀胱疾病中起关键作用（目的3）。本项目的研究结果将有助于阐明尿路上皮斑块的结构、功能和调控，并将对间质性膀胱炎、尿路感染和膀胱癌形成等几种重要膀胱疾病的分子病因学和发病机制产生重要影响。

The apical surface of mammalian urothelium is almost completely covered by rigid-looking urothelial plaques consisting of 16 nm uroplakin particles that are hexagonally packed into two-dimensional crystals. Highly purified urothelial plaques are comprised of four major uroplakins (UP), i.e., uroplakin Ia (27 kDa), Ib (28 kDa), II (15 kDa) and III (47 kDa). The two tetraspanin members UPIa and UPIb interact preferentially with the two single transmembrane-domained uroplakins II and III, respectively, forming two uroplakin pairs consisting of UPIa/II and UPIb/III. During the last grant period, we genetically ablated mouse genes encoding for uroplakins II and III. Mice deficient in these two major urothelial differentiation products have a grossly abnormal urothelium lacking typical umbrella cells; have abnormally small urothelial plaques; and suffer from vesicoureteral reflux, hydronephrosis and, in some cases, neonatal death. These results indicate that uroplakins are integral subunits of the urothelial plaques which contribute to the permeability barrier function, and that urothelial defects may play a role in certain urinary tract diseases. Little is known, however, about how uroplakin defects may affect urothelial and bladder function as a whole, how uroplakins interact with cytoplasmic and other membrane-associated proteins, and how surface-accessible are the uroplakin receptors to the uropathogenic bacteria. The proposed studies in this Project will attempt to answer some of these questions, by studying how the ablation of uroptakin genes affects the permeability barrier and micturition functions of the bladder (Aim 1); how uroplakins interact with some cytoplasmic proteins that may play a role in mediating uroplaldn:cytosketetal interaction and signal transduction (Aim 2); and how accessible uroplakin molecules are on the apical surface of urothelial umbrella cells, and whether there are other uroplakin-associated cell surface proteins that may be related to the urotheliat 'glycocalyx' coating that has been hypothesized to play a key role in several bladder diseases (Aim 3). Results from this Project will shed light on the structure, function and regulation of urothelial plaques, and will have major implications on the molecular etiology and pathogenesis of several important bladder diseases including interstitial cystitis, urinary tract infection and bladder cancer formation.