肾小球上皮蛋白1在发育中小鼠肾脏中的分子克隆、表达及分布

Molecular cloning, expression, and distribution of glomerular epithelial protein 1 in developing mouse kidney.

作者信息

Wang R, St John P L, Kretzler M, Wiggins R C, Abrahamson D R

机构信息

Department of Cell Biology, University of Alabama at Birmingham, USA.

出版信息

Kidney Int. 2000 May;57(5):1847-59. doi: 10.1046/j.1523-1755.2000.00034.x.

DOI:10.1046/j.1523-1755.2000.00034.x

PMID:10792603

Abstract

BACKGROUND

Glomerular epithelial protein 1 (GLEPP1) is a receptor-like membrane protein tyrosine phosphatase (RPTP) with a large ectodomain consisting of multiple fibronectin type III repeats, a single transmembrane segment, and a single cytoplasmic phosphatase active site sequence. In adult human and rabbit kidneys, GLEPP1 is found exclusively on apical membranes of podocytes and especially on surfaces of foot processes. Although neither ligand nor function for this protein is known, other RPTPs with similar topologies have been implicated in mediating adherence behavior of cells.

METHODS

To evaluate potential roles of GLEPP1 further, we cloned the full-length mouse GLEPP1 cDNA and examined its expression patterns in developing kidney by Northern blot analysis, in situ hybridization, and immunofluorescence microscopy.

RESULTS

Nucleotide sequencing showed that mouse GLEPP1 was approximately 80% identical to rabbit and human GLEPP1 and approximately 91% identical at the amino acid level. The membrane-spanning and phosphatase domains of mouse GLEPP1 shared> 99% homology with PTPphi, a murine macrophage cytoplasmic phosphatase. Northern analysis identified a single GLEPP1 transcript of approximately 5.5 kb in fetal kidney that became approximately threefold more abundant in adults. In situ hybridization of newborn mouse kidney revealed GLEPP1 mRNA in visceral epithelial cells (developing podocytes) of comma- and S-shaped nephric figures, and expression increased in capillary loop and maturing stage glomeruli. Beginning on embryonic day 14, GLEPP1 protein was first observed on cuboidal podocytes of capillary loop stage glomeruli, but nascent podocytes of earlier comma- and S-shaped nephric figures were negative. At later stages of glomerular maturation, where foot process elongation and interdigitation occurs, GLEPP1 immunolabeling intensified on podocytes and then persisted at high levels in fully developed glomeruli.

CONCLUSION

Our findings are consistent with a role for GLEPP1 in mediating and maintaining podocyte differentiation specifically.

摘要

背景

肾小球上皮蛋白1（GLEPP1）是一种受体样膜蛋白酪氨酸磷酸酶（RPTP），其大的胞外结构域由多个III型纤连蛋白重复序列、一个单一跨膜片段和一个单一胞质磷酸酶活性位点序列组成。在成年人类和兔肾脏中，GLEPP1仅存在于足细胞的顶端膜上，尤其是在足突表面。尽管该蛋白的配体和功能均未知，但具有相似拓扑结构的其他RPTP已被认为参与介导细胞的黏附行为。

方法

为了进一步评估GLEPP1的潜在作用，我们克隆了全长小鼠GLEPP1 cDNA，并通过Northern印迹分析、原位杂交和免疫荧光显微镜检查了其在发育中肾脏的表达模式。

结果

核苷酸测序表明，小鼠GLEPP1与兔和人类GLEPP1的同源性约为80%，在氨基酸水平上约为91%。小鼠GLEPP1的跨膜和磷酸酶结构域与小鼠巨噬细胞胞质磷酸酶PTPphi的同源性>99%。Northern分析在胎儿肾脏中鉴定出一个约5.5 kb的单一GLEPP1转录本，在成体中其丰度增加约三倍。新生小鼠肾脏的原位杂交显示，逗号状和S形肾单位的脏层上皮细胞（发育中的足细胞）中有GLEPP1 mRNA，在毛细血管袢和成熟阶段的肾小球中表达增加。从胚胎第14天开始，首先在毛细血管袢阶段肾小球的立方形足细胞上观察到GLEPP1蛋白，但早期逗号状和S形肾单位的新生足细胞为阴性。在肾小球成熟的后期阶段，足突伸长和交叉指状化发生时，GLEPP1免疫标记在足细胞上增强，然后在完全发育的肾小球中持续高水平存在。