MAGI-1 is a component of the glomerular slit diaphragm that is tightly associated with nephrin

Lab Invest. 2005 Dec;85(12):1528-43. doi: 10.1038/labinvest.3700347.

Abstract

MAGUK with inverted domain structure-1 (MAGI-1) is a membrane-associated protein with one guanylate kinase, six PSD-95/Dlg-A/ZO-1 (PDZ), and two WW domains and is localized at tight junctions in epithelial cells. MAGI-1 interacts with various proteins and is proposed to function as a scaffold protein. In the previous study, we discovered a MAGI-1-interacting cell adhesion molecule junctional adhesion molecule 4 (JAM4). Both proteins are highly expressed in glomerular podocytes in the kidney and partially colocalized. In this study, we have further searched for a binding partner of MAGI-1 in the kidney through yeast two-hybrid screening and obtained nephrin. Nephrin is a cell adhesion molecule specifically localized at the slit diaphragm between neighboring foot processes of podocytes. Biochemical studies reveal that nephrin directly binds to the middle PDZ domains of MAGI-1 through its carboxyl terminus but does not bind to ZO-1. MAGI-1 forms a tripartite complex with nephrin and JAM4 in vitro. Immunoelectron microscopy shows that the localization of MAGI-1 is restricted to the slit diaphragm, whereas JAM4 is also distributed on apical membranes of podocytes. In puromycin aminonucleoside-induced nephrotic podocytes, MAGI-1 is localized with nephrin at the displaced slit diaphragm. These data indicate that MAGI-1 is a component of the slit diaphragm and tightly interacts with nephrin and JAM4 in vivo. MAGI-1 may play a role in determining the boundary between the apical and the bosolateral domain at the level of slit diaphragm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • COS Cells
  • Cell Adhesion Molecules / metabolism*
  • Cell Adhesion Molecules / ultrastructure
  • Chlorocebus aethiops
  • Fluorescent Antibody Technique, Indirect
  • Glomerular Mesangium / metabolism*
  • Glomerular Mesangium / ultrastructure
  • Guanylate Kinases
  • Humans
  • Membrane Proteins / metabolism*
  • Membrane Proteins / ultrastructure
  • Microscopy, Immunoelectron
  • Nephrosis / chemically induced
  • Nephrosis / metabolism*
  • Nephrosis / pathology
  • Phosphoproteins / metabolism
  • Podocytes / enzymology*
  • Podocytes / ultrastructure
  • Protein Binding
  • Rats
  • Tight Junctions / enzymology
  • Two-Hybrid System Techniques
  • Zonula Occludens-1 Protein

Substances

  • Adaptor Proteins, Signal Transducing
  • Cell Adhesion Molecules
  • Igsf5 protein, rat
  • Membrane Proteins
  • Phosphoproteins
  • TJP1 protein, human
  • Tjp1 protein, mouse
  • Tjp1 protein, rat
  • Zonula Occludens-1 Protein
  • nephrin
  • Guanylate Kinases
  • Magi1 protein, mouse