title: Expression of galectin-1, a new component of slit diaphragm, is altered in minimal change nephrotic syndrome.
abstract: 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.
authors.affiliation: Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Jamshid
authors.initials: J
authors.lastname: Khoshnoodi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Akimoto
authors.forename: Hayato
authors.initials: H
authors.lastname: Kawakami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirano
authors.forename: Eiji
authors.initials: E
authors.lastname: Higashihara
authors.forename: Makoto
authors.initials: M
authors.lastname: Hosoyamada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sekine
authors.forename: Ryota
authors.initials: R
authors.lastname: Kurayama
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kurayama
authors.forename: Kensuke
authors.initials: K
authors.lastname: Joh
authors.forename: Jun
authors.initials: J
authors.lastname: Hirabayashi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kasai
authors.forename: Karl
authors.initials: K
authors.lastname: Tryggvason
authors.forename: Noriko
authors.initials: N
authors.lastname: Ito
authors.forename: Kunimasa
authors.initials: K
authors.lastname: Yan
mesh_terms: 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
chemical_list: D037483:Galectin 1; D008565:Membrane Proteins; D011994:Recombinant Proteins; C113267:nephrin; D014443:Tyrosine; D048052:Mitogen-Activated Protein Kinase 3