Nephrin regulates lamellipodia formation by assembling a protein complex that includes Ship2, filamin and lamellipodin

• Published in: PloS one Vol. 6; no. 12; p. e28710
• Main Authors: Venkatareddy, Madhusudan, Cook, Leslie, Abuarquob, Kamal, Verma, Rakesh, Garg, Puneet
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.12.2011; Public Library of Science (PLoS)
• Subjects: Actin; Actins - metabolism; Adaptor Proteins, Signal Transducing - metabolism; Adhesion; Animals; Biology; Breast cancer; Carrier Proteins - metabolism; CD16 antigen; Cell activation; Cell adhesion & migration; Cell culture; Cell division; Cell growth; Cell Membrane - metabolism; Cell migration; Clustering; Contractile Proteins - metabolism; Crosslinking; Cytoskeleton; Diaphragm; Diaphragm (anatomy); Dynamic tests; Dynamics; Epidermal growth factor; Fc receptors; Fibroblasts; Filamins; Gene Knockdown Techniques; GTP-binding protein; Humans; Inositol; Inositol polyphosphate 5-phosphatase; Inositol Polyphosphate 5-Phosphatases; Kinases; Lamellipodia; Leukocyte migration; Ligands; Medical schools; Medicine; Membrane Proteins - metabolism; Mice; Microfilament Proteins - metabolism; Models, Biological; Morphology; Multiprotein Complexes - metabolism; Muscle proteins; Mutation; myo-Inositol-1 (or 4)-monophosphatase; Nephrology; Oncogene Proteins - metabolism; p21-activated kinase; p21-Activated Kinases - metabolism; Phosphatase; Phosphatases; Phosphatidylinositol Phosphates - metabolism; Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; Phosphoric Monoester Hydrolases - metabolism; Phosphorylation; Phosphotyrosine - metabolism; Podocytes - metabolism; Podocytes - pathology; Polymerization; Protamines - metabolism; Protein Binding; Proteins; Pseudopodia; Pseudopodia - metabolism; RNA, Small Interfering - metabolism; Signal Transduction; src Homology Domains; Trends; Ann Arbor Michigan; United States > US; Michigan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0028710

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.