Nephrin is specifically located at the slit diaphragm of glomerular podocytes

Abstract

We describe here the size and location of nephrin, the first protein to be identified at the glomerular podocyte slit diaphragm. In Western blots, nephrin antibodies generated against the two terminal extracellular Ig domains of recombinant human nephrin recognized a 180-kDa protein in lysates of human glomeruli and a 150-kDa protein in transfected COS-7 cell lysates. In immunof luorescence, antibodies to this transmembrane protein revealed reactivity in the glomerular basement membrane region, whereas the podocyte cell bodies remained negative. In immunogold-stained thin sections, nephrin label was found at the slit between podocyte foot processes. The congenital nephrotic syndrome of the Finnish type (NPHS1), a disease in which the nephrin gene is mutated, is characterized by massive proteinuria already in utero and lack of slit diaphragm and foot processes. These features, together with the now demonstrated localization of nephrin to the slit diaphragm area, suggests an essential role for this protein in the normal glomerular filtration barrier. A zipper-like model for nephrin assembly in the slit diaphragm is discussed, based on the present and previous data.

Functional and molecular alterations of the glomerular barrier in long-term diabetes in mice

“…For a long time the glomerular basement membrane (GBM) has been considered to be the main barrier for filtration. More recently, focus has shifted to the podocytes, since several novel proteins in the podocyte slit diaphragm have been found to be important for the barrier function [1][2][3]. In addition, we have suggested a role for the glomerular endothelial cell glycocalyx [4][5][6][7][8][9][10], an idea supported also by others [11,12].…”

“…Under normal conditions, the glomerular barrier restricts the passage of macromolecules such as albumin, while it is highly permeable to water and small solutes. The underlying mechanisms leading to proteinuria are still poorly understood, although the importance of the podocyte for glomerular integrity has been clearly documented [1][2][3]. Consequently, there is no specific therapy for diabetic nephropathy.…”

Nephrin Forms a Complex with Adherens Junction Proteins and CASK in Podocytes and in Madin-Darby Canine Kidney Cells Expressing Nephrin

“…Thus the distribution of nephrin in MDCK cells resembles that in the glomerulus where nephrin has been localized in both the junctional or slit diaphragm region and at the apical domain of podocytes. [3][4][5] …”

“…1 NPHS1 encodes for nephrin, 1 a member of the immunoglobulin (Ig) superfamily of cell adhesion molecules, 2 which is localized in the glomerular slit diaphragm and has been suggested to form the framework of this specialized cell adhesion structure. [3][4][5] Slit diaphragms are important components of the glomerular filtration barrier. They bridge the urinary spaces between the foot processes of the glomerular epithelium and serve to attach foot processes to one another.…”

Renoprotective effects of vasopeptidase inhibition in an experimental model of diabetic nephropathy

“…Furthermore, detailed assessment of renal structural injury and investigation of molecular mechanisms suggested to play a potential role in diabetes associated albuminuria and renal extra cellular matrix accumulation were also explored. Specifically, the recently described slit-pore protein nephrin, which has been postulated to modulate glomerular albumin permeability, was assessed [20]. In addition, expression of TGFβ, a prosclerotic cytokine implicated in diabetes-associated extracellular matrix accumulation [21] and the TGFβ dependent matrix protein, βig-h3 [22] were evaluated.…”