Expression of galectin-1, a new component of slit diaphragm, is altered in minimal change nephrotic syndrome.
Nephrin is an essential structural component of the glomerular slit diaphragm (SD), a highly organized intercellular junction that constitutes the ultrafiltration barrier of the kidney. Recent studies have identified two additional nephrin-interacting SD proteins (NEPH1 and NEPH2), suggesting that the zipper-like pattern of the SD is formed through complex intra- and intermolecular interactions of these proteins. However, the complexity of the SD structure suggests that additional SD components remain to be discovered. In this study, we identified galectin-1 (Gal-1) as a new component of the SD, binding to the ectodomain of nephrin. Using dual-immunofluorescence and confocal microscopy and dual-immunoelectron microscopy, we found Gal-1 co-localizing with the ectodomain of nephrin at the SD in normal human kidney. By immunoprecipitation and surface plasmon resonance, we confirmed a direct molecular interaction between Gal-1 and nephrin. Moreover, recombinant Gal-1 induced tyrosine phosphorylation of the cytoplasmic domain of nephrin and activation of the extracellular signal-regulated kinase 1/2 in podocytes. We also showed that podocytes are a major site of biosynthesis of Gal-1 in the glomerulus and that the normal expression patterns and levels of Gal-1 are altered in patients with minimal change nephrotic syndrome. Finally, in puromycin aminonucleoside-induced rat nephrosis, an apparent reduction in the levels of Gal-1 and nephrin around the onset of heavy proteinuria was also revealed. Our data present Gal-1 as a new extracellular ligand of nephrin localized at the glomerular SD, and provide further insight into the complex molecular organization, interaction, and structure of the SD, which is an active site of intracellular signaling necessary for podocyte function.
Shimizu
Mariko
M
Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
Khoshnoodi
Jamshid
J
Akimoto
Yoshihiro
Y
Kawakami
Hayato
H
Hirano
Hiroshi
H
Higashihara
Eiji
E
Hosoyamada
Makoto
M
Sekine
Yuji
Y
Kurayama
Ryota
R
Kurayama
Hideaki
H
Joh
Kensuke
K
Hirabayashi
Jun
J
Kasai
Kenichi
K
Tryggvason
Karl
K
Ito
Noriko
N
Yan
Kunimasa
K
D000818:Animals; D002461:Cell Line, Transformed; D004195:Disease Models, Animal; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D037483:Galectin 1 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D048052:Mitogen-Activated Protein Kinase 3 / Q000096:biosynthesis; D009402:Nephrosis, Lipoid / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D011994:Recombinant Proteins; D014443:Tyrosine / Q000378:metabolism
D037483:Galectin 1; D008565:Membrane Proteins; D011994:Recombinant Proteins; C113267:nephrin; D014443:Tyrosine; D048052:Mitogen-Activated Protein Kinase 3