RED CELL CYTOSKELETON PROTEIN 4.1R IN KIDNEY FUNCTION

蛋白4.1R是一种红细胞骨架蛋白，通过桥接谱蛋白-肌动蛋白骨架与特定的跨膜蛋白，在维持红细胞形状和可变形性中起关键作用。4.1 r在有核细胞的各种细胞器中的鉴定，以及最近与4.1 r具有非常高同源性的三个新基因的鉴定，使人们对4.1蛋白家族成员在非红系细胞中的作用的研究兴趣升级。在过去的几年里，人们已经清楚地认识到细胞骨架不仅为质膜提供支持或在特定区域分离膜蛋白，而且还可以调节包括各种转运蛋白在内的膜蛋白的功能。在肾上皮中，选择的溶质转运蛋白的功能和紧密连接的选择性通透性取决于肌动蛋白细胞骨架的完整性。四个4.1基因特异性探针的原位杂交表明，蛋白4.1家族的成员可能在包括脑和肾在内的选定组织中具有特异性分布。在肾脏中，4.1R似乎主要积聚在肾元近端小管，这是肾脏重吸收和/或分泌水和溶质的主要区域。我们的工作假设是4.1R可能通过与肾细胞上皮的膜转运蛋白相互作用来调节近端小管的这些功能。为了研究这种可能性，我们建议：1)鉴定4.1R的肾同种异构体及其同源物，并表征它们在肾脏中的分布模式；2)鉴定4.1R在肾脏中的结合伙伴；3)比较野生型和4.1R缺失小鼠的肾功能，以破译4.1R调节转运体重吸收和/或分泌的机制，并研究4.1R敲除小鼠的紧密连接组织是否受到损害。我们预计，对肾细胞上皮蛋白4.1家族成员功能的详细了解将有助于阐明与细胞骨架蛋白缺陷相关的肾脏病理。

Protein 4.1R is a red cell cytoskeletal protein which plays a key role in maintaining erythrocyte shape and deformability by bridging the spectrin-actin cytoskeleton to specific transmembrane proteins. The identification of 4.1R in various organelles of nucleated cells along with the recent characterization of three novel genes sharing very high homology with 4.1R have escalated the interest in studying the role of members of the protein 4.1 family in non erythroid cells. Over the past years, it has become clear that the cytoskeleton does not only provide support for the plasma membrane or segregate membrane proteins in specialized domains, but that it can also regulate the functions of such membrane proteins including various transporters. In kidney epithelia, functions of selected solute transporters and selective permeability of tight junctions depend on the integrity of the actin cytoskeleton. In situ hybridization of probes specific for each of the four 4.1 genes suggest that members of the protein 4.1 family may adopt specific distribution within selected tissues including brain and kidney. In the kidney, 4.1R seems to accumulate predominantly in the proximal tubule of the nephron, a region where most of renal reabsorption and/or secretion of water and solutes occur. Our working hypothesis is that 4.1R may regulate such functions of the proximal tubule by interacting with membrane transporters of the nephron epithelium. To investigate this possibility, we propose to 1) identify the renal isoforms of 4.1R and its homologs and characterize their distribution pattern within the kidney, 2) identify binding partners for 4.1R in the kidney, focusing in particular on membrane transporters and 3) compare renal function in wild type and 4.1R null mice in order to decipher the mechanisms by which 4.1R may regulate reabsorption and/or secretion by selected transporters and investigate whether the organization of tight junctions is compromised in 4.1R knock out mice. We anticipate that a detailed understanding of the functions of members of the protein 4.1 family in the epithelium of the nephron will shed light on kidney pathologies related to defects in cytoskeletal proteins.