title: TM4SF10 and ADAP interaction in podocytes: role in Fyn activity and nephrin phosphorylation.
abstract: TM4SF10 [transmembrane tetra(4)-span family 10] is a claudin-like cell junction protein that is transiently expressed during podocyte development where its expression is downregulated in differentiating podocytes coincident with the appearance of nephrin at the slit diaphragm. In a yeast two-hybrid screen, we identified adhesion and degranulation-promoting adaptor protein (ADAP), a well-known Fyn substrate and Fyn binding partner, as a TM4SF10 interacting protein in mouse kidney. Using coimmunoprecipitation and immunohistochemistry experiments in cultured human podocytes, we show that TM4SF10 colocalizes with Fyn and ADAP but does not form a stable complex with Fyn. Cytoskeletal changes and phosphorylation events mediated by Fyn activity were reversed by TM4SF10 overexpression, including a decrease in the activating tyrosine phosphorylation of Fyn (Y(421)), suggesting TM4SF10 may have a regulatory role in suppressing Fyn activity. In addition, TM4SF10 was reexpressed following podocyte injury by puromycin aminonucleoside treatment, and its expression enhanced the abundance of high-molecular-weight forms of nephrin indicating it may participate in a mechanism controlling nephrin's appearance at the plasma membrane. Therefore, these studies have identified ADAP as another Fyn adapter protein expressed in podocytes, and that TM4SF10, possibly through ADAP, may regulate Fyn activity. Since TM4SF10 expression is temporally regulated during kidney development, these studies may help define a mechanism by which the slit diaphragm matures as a highly specialized cell junction during podocyte differentiation.
authors: Rammelkamp Center for Education and Research, Division of Neonatology, Department of Pediatrics, MetroHealth Medical Center, 2500 MetroHealth Dr., Cleveland, OH 44109, USA.
authors: Timur A
authors: TA
authors: Azhibekov
authors: Zhenzhen
authors: Z
authors: Wu
authors: Aparna
authors: A
authors: Padiyar
authors: Leslie A
authors: LA
authors: Bruggeman
authors: Jeffrey S
authors: JS
authors: Simske
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007365:Intercellular Junctions / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D050199:Podocytes / Q000166:cytology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism*; D051381:Rats; D014161:Transduction, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C106957:FYB1 protein, human; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C491469:TMEM47 protein, human; C113267:nephrin; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn