title: Ezrin is down-regulated in diabetic kidney glomeruli and regulates actin reorganization and glucose uptake via GLUT1 in cultured podocytes.
abstract: Diabetic nephropathy is a complication of diabetes and a major cause of end-stage renal disease. To characterize the early pathophysiological mechanisms leading to glomerular podocyte injury in diabetic nephropathy, we performed quantitative proteomic profiling of glomeruli isolated from rats with streptozotocin-induced diabetes and controls. Fluorescence-based two-dimensional difference gel electrophoresis, coupled with mass spectrometry, identified 29 differentially expressed spots, including actin-binding protein ezrin and its interaction partner, NHERF2, which were down-regulated in the streptozotocin group. Knockdown of ezrin by siRNA in cultured podocytes increased glucose uptake compared with control siRNA-transfected cells, apparently by increasing translocation of glucose transporter GLUT1 to the plasma membrane. Knockdown of ezrin also induced actin remodeling under basal conditions, but reduced insulin-stimulated actin reorganization. Ezrin-dependent actin remodeling involved cofilin-1 that is essential for the turnover and reorganization of actin filaments. Phosphorylated, inactive cofilin-1 was up-regulated in diabetic glomeruli, suggesting altered actin dynamics. Furthermore, IHC analysis revealed reduced expression of ezrin in the podocytes of patients with diabetes. Our findings suggest that ezrin may play a role in the development of the renal complication in diabetes by regulating transport of glucose and organization of the actin cytoskeleton in podocytes.
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Anita A
authors.initials: AA
authors.lastname: Wasik
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Susanna
authors.initials: S
authors.lastname: Koskelainen
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland; Children's Hospital, University of Helsinki, Helsinki, Finland.
authors.forename: Mervi E
authors.initials: ME
authors.lastname: Hyvönen
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Luca
authors.initials: L
authors.lastname: Musante
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland; Laboratory Animal Centre, University of Helsinki, Helsinki, Finland.
authors.forename: Eero
authors.initials: E
authors.lastname: Lehtonen
authors.affiliation: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Kerttu
authors.initials: K
authors.lastname: Koskenniemi
authors.affiliation: Department of Pathology, HUSLAB, Helsinki University Central Hospital, Helsinki and Hyvinkää, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Tienari
authors.affiliation: Department of Virology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Vaheri
authors.affiliation: Clinical Institute of Pathology, Medical University of Vienna, Vienna, Austria.
authors.forename: Dontscho
authors.initials: D
authors.lastname: Kerjaschki
authors.affiliation: Institute of Pathophysiology, Semmelweis University, Budapest, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Szalay
authors.affiliation: Institute of Pathophysiology, Semmelweis University, Budapest, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Révész
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Varmanen
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Tuula A
authors.initials: TA
authors.lastname: Nyman
authors.affiliation: Institute of Pathophysiology, Semmelweis University, Budapest, Hungary.
authors.forename: Peter
authors.initials: P
authors.lastname: Hamar
authors.affiliation: Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Harry
authors.initials: H
authors.lastname: Holthöfer
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland. Electronic address: sanna.h.lehtonen@helsinki.fi.
authors.forename: Sanna
authors.initials: S
authors.lastname: Lehtonen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000473:pathology; D000199:Actins / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D003928:Diabetic Nephropathies / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D008297:Male; D050199:Podocytes / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000099149:Ezrin
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D005947:Glucose; D051272:Glucose Transporter Type 1; D000099149:Ezrin; C495677:SLC2A1 protein, human; C495679:Slc2a1 protein, rat