title: Shp2 Associates with and Enhances Nephrin Tyrosine Phosphorylation and Is Necessary for Foot Process Spreading in Mouse Models of Podocyte Injury.
abstract: In most forms of glomerular diseases, loss of size selectivity by the kidney filtration barrier is associated with changes in the morphology of podocytes. The kidney filtration barrier is comprised of the endothelial lining, the glomerular basement membrane, and the podocyte intercellular junction, or slit diaphragm. The cell adhesion proteins nephrin and neph1 localize to the slit diaphragm and transduce signals in a Src family kinase Fyn-mediated tyrosine phosphorylation-dependent manner. Studies in cell culture suggest nephrin phosphorylation-dependent signaling events are primarily involved in regulation of actin dynamics and lamellipodium formation. Nephrin phosphorylation is a proximal event that occurs both during development and following podocyte injury. We hypothesized that abrogation of nephrin phosphorylation following injury would prevent nephrin-dependent actin remodeling and foot process morphological changes. Utilizing a biased screening approach, we found nonreceptor Src homology 2 (sh2) domain-containing phosphatase Shp2 to be associated with phosphorylated nephrin. We observed an increase in nephrin tyrosine phosphorylation in the presence of Shp2 in cell culture studies. In the human glomerulopathies minimal-change nephrosis and membranous nephropathy, there is an increase in Shp2 phosphorylation, a marker of increased Shp2 activity. Mouse podocytes lacking Shp2 do not develop foot process spreading when subjected to podocyte injury in vivo using protamine sulfate or nephrotoxic serum (NTS). In the NTS model, we observed a lack of foot process spreading in mouse podocytes with Shp2 deleted and smaller amounts of proteinuria. Taken together, these results suggest that Shp2-dependent signaling events are necessary for changes in foot process structure and function following injury.
authors.affiliation: Division of Nephrology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Verma
authors.affiliation: Division of Nephrology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA.
authors.forename: Madhusudan
authors.initials: M
authors.lastname: Venkatareddy
authors.affiliation: Division of Nephrology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Kalinowski
authors.affiliation: Division of Nephrology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA.
authors.forename: Sanjeevkumar R
authors.initials: SR
authors.lastname: Patel
authors.affiliation: Division of Nephrology, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Salant
authors.affiliation: Division of Nephrology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA pungarg@umich.edu.
authors.forename: Puneet
authors.initials: P
authors.lastname: Garg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004195:Disease Models, Animal; D017353:Gene Deletion; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009393:Nephritis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D050199:Podocytes / Q000378:metabolism / Q000473:pathology*; D011479:Protamines; D060066:Protein Interaction Maps; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000032:analysis / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D011479:Protamines; C113267:nephrin; D014443:Tyrosine; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; C516725:Ptpn11 protein, mouse