Cessac-Guillemet A L, Mounier F, Borot C, Bakala H, Perichon M, Schaeverbeke M, Schaeverbeke J
Laboratoire de Biologie Cellulaire, Université Paris 7, France.
Am J Physiol. 1996 Jul;271(1 Pt 2):F101-7. doi: 10.1152/ajprenal.1996.271.1.F101.
The mechanism by which proteins that pass through the glomerular basal lamina are taken up by proximal tubule cells is incompletely characterized. Past work has identified the kinetics of albumin binding to renal brush-border membrane. We have now purified and characterized albumin binding protein (ABP) and shown its distribution in renal proximal tubular cells. ABP was purified from rat renal proximal tubular cell brush-border membrane by affinity chromatography with rat serum albumin-Sepharose. The resulting ABP had two apparent molecular masses (55 and 31 kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antibodies to ABP were raised in rabbits and checked by immunoassay and immunoblotting. Light-microscopic immunohistochemistry showed ABP all along the proximal tubule in the pars convoluta and pars recta. Electron-microscopic immunohistochemistry showed labeling on microvilli and in apical endocytic vacuoles, dense apical tubules, and lysosomes. These results indicate that ABP is involved in proximal tubule endocytosis.
穿过肾小球基底膜的蛋白质被近端小管细胞摄取的机制尚未完全明确。过去的研究已经确定了白蛋白与肾刷状缘膜结合的动力学。我们现已纯化并鉴定了白蛋白结合蛋白（ABP），并展示了其在肾近端小管细胞中的分布。通过用大鼠血清白蛋白-琼脂糖进行亲和层析，从大鼠肾近端小管细胞刷状缘膜中纯化出ABP。经十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析，所得ABP有两种明显的分子量（55和31 kDa）。用兔制备抗ABP抗体，并通过免疫测定和免疫印迹进行检测。光学显微镜免疫组织化学显示，ABP存在于曲部和直部的整个近端小管中。电子显微镜免疫组织化学显示，微绒毛、顶端内吞泡、致密顶端小管和溶酶体上有标记。这些结果表明，ABP参与近端小管的内吞作用。
