Dual sources of vitronectin in the human lower urinary tract: synthesis by urothelium vs. extravasation from the bloodstream.
Dual sources of vitronectin in the human lower urinary tract: synthesis by urothelium vs. extravasation from the bloodstream.
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人类下尿路中玻连蛋白的双重来源：尿路上皮合成与血液外渗。
DOI：
10.1152/ajprenal.00407.2010
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Bassuk,JamesA
中科院分区：
文献类型：
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作者：
Zhang,Dianzhong;Hudson,AmberE;Delostrinos,CatherineF;Carmean,Nicole;EastmanJr,Rocky;Hicks,Bryson;Hurst,RobertE;Bassuk,JamesA
玻璃体连接蛋白（VN）由肝细胞分泌到血液中，已知通过与细胞表面整合素受体的相互作用将上皮细胞固定在基底膜上。我们在这里报道了尿路上皮细胞在体内和体外也能合成VN。对尿路上皮细胞mRNA、cDNA、组织和蛋白提取物进行原位杂交、双脱氧测序、免疫组化和ELISA检测，结果表明VN基因在体内和体外均具有活性。据推测，尿路上皮表达VN是将基底细胞锚定在下层基质上的几种途径之一，并解释了为什么尿路上皮细胞粘附在玻璃上并在无血清条件下繁殖。因此，人类膀胱内VN有两种来源：1)尿路上皮细胞局部合成和2)肝VN通过开孔毛细血管外渗。通过变性肝素亲和层析分离人血浆，分离出具有生物活性的VN，支持体外无血清条件下尿路上皮细胞的快速扩散。基质细胞蛋白SPARC通过Ca+2依赖机制将VN与SPARC直接结合，从而抑制了这种活性。从同一肝素亲和层析柱中分离出的一种新型VN(c)也支持细胞扩散，但不能与SPARC相互作用。因此，尿路上皮细胞、它们的细胞外环境和基质细胞蛋白之间的稳态平衡构成了尿路上皮在面对不断的膀胱循环时被固定在底层的主要机制。
Vitronectin (VN), secreted into the bloodstream by liver hepatocytes, is known to anchor epithelial cells to basement membranes through interactions with cell surface integrin receptors. We report here that VN is also synthesized by urothelial cells of urothelium in vivo and in vitro. In situ hybridization, dideoxy sequencing, immunohistochemistry, and ELISA of urothelial cell mRNA, cDNA, tissue, and protein extracts demonstrated that the VN gene is active in vivo and in vitro. The expression of VN by urothelium is hypothesized to constitute one of several pathways that anchor basal cells to an underlying substratum and explains why urothelial cells adhere to glass and propagate under serum-free conditions. Therefore, two sources of VN in the human urinary bladder are recognized:1) localized synthesis by urothelial cells and2) extravasation of liver VN through fenestrated capillaries. When human plasma was fractionated by denaturing heparin affinity chromatography, VN was isolated in a biologically active form that supported rapid spreading of urothelial cells in vitro under serum-free conditions. This activity was inhibited by the matricellular protein SPARC via direct binding of VN to SPARC through a Ca+2-dependent mechanism. A novel form of VN, isolated from the same heparin affinity chromatography column and designated as the VN(c) chromatomer, also supported cell spreading but failed to interact with SPARC. Therefore, the steady-state balance among urothelial cells, their extracellular milieu, and matricellular proteins constitutes a principal mechanism by which urothelia are anchored to an underlying substrata in the face of constant bladder cycling.