title: Nephrin regulates lamellipodia formation by assembling a protein complex that includes Ship2, filamin and lamellipodin.
abstract: Actin dynamics has emerged at the forefront of podocyte biology. Slit diaphragm junctional adhesion protein Nephrin is necessary for development of the podocyte morphology and transduces phosphorylation-dependent signals that regulate cytoskeletal dynamics. The present study extends our understanding of Nephrin function by showing in cultured podocytes that Nephrin activation induced actin dynamics is necessary for lamellipodia formation. Upon activation Nephrin recruits and regulates a protein complex that includes Ship2 (SH2 domain containing 5' inositol phosphatase), Filamin and Lamellipodin, proteins important in regulation of actin and focal adhesion dynamics, as well as lamellipodia formation. Using the previously described CD16-Nephrin clustering system, Nephrin ligation or activation resulted in phosphorylation of the actin crosslinking protein Filamin in a p21 activated kinase dependent manner. Nephrin activation in cell culture results in formation of lamellipodia, a process that requires specialized actin dynamics at the leading edge of the cell along with focal adhesion turnover. In the CD16-Nephrin clustering model, Nephrin ligation resulted in abnormal morphology of actin tails in human podocytes when Ship2, Filamin or Lamellipodin were individually knocked down. We also observed decreased lamellipodia formation and cell migration in these knock down cells. These data provide evidence that Nephrin not only initiates actin polymerization but also assembles a protein complex that is necessary to regulate the architecture of the generated actin filament network and focal adhesion dynamics.
authors.affiliation: Division of Nephrology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.
authors.forename: Madhusudan
authors.initials: M
authors.lastname: Venkatareddy
authors.forename: Leslie
authors.initials: L
authors.lastname: Cook
authors.forename: Kamal
authors.initials: K
authors.lastname: Abuarquob
authors.forename: Rakesh
authors.initials: R
authors.lastname: Verma
authors.forename: Puneet
authors.initials: P
authors.lastname: Garg
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism*; D064448:Filamins; D055785:Gene Knockdown Techniques; D006801:Humans; D000072181:Inositol Polyphosphate 5-Phosphatases; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D050199:Podocytes / Q000378:metabolism / Q000473:pathology; D011479:Protamines / Q000378:metabolism; D011485:Protein Binding; D011554:Pseudopodia / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D054462:p21-Activated Kinases / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003285:Contractile Proteins; D064448:Filamins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D046912:Multiprotein Complexes; C078332:Nck protein; D015513:Oncogene Proteins; D018129:Phosphatidylinositol Phosphates; D011479:Protamines; C493339:RAPH1 protein, human; D034741:RNA, Small Interfering; C113267:nephrin; C060980:phosphatidylinositol 3,4-diphosphate; D019000:Phosphotyrosine; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606435:Inppl1 protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases