Nephrocystin interacts with Pyk2, p130(Cas), and tensin and triggers phosphorylation of Pyk2.
Juvenile nephronophthisis type 1 is caused by mutations of NPHP1, the gene encoding for nephrocystin. The function of nephrocystin is presently unknown, but the presence of a Src homology 3 domain and its recently described interaction with p130(Cas) suggest that nephrocystin is part of the focal adhesion signaling complex. We generated a nephrocystin-specific antiserum and analyzed the interaction of native nephrocystin with endogenous proteins. Immunoprecipitation of nephrocystin revealed that nephrocystin forms protein complexes with p130(Cas), proline-rich tyrosine kinase 2 (Pyk2), and tensin, indicating that these proteins participate in a common signaling pathway. Expression of nephrocystin resulted in phosphorylation of Pyk2 on tyrosine 402 as well as activation of downstream mitogen-activated protein kinases, such as ERK1 and ERK2. Our findings suggest that nephrocystin helps to recruit Pyk2 to cell matrix adhesions, thereby initiating phosphorylation of Pyk2 and Pyk2-dependent signaling. A lack of functional nephrocystin may compromise Pyk2 signaling in a subset of renal epithelial cells.
Benzing
T
T
Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany; and Children's Hospital, and Molecular Medicine, University of Freiburg, 79106 Freiburg, Germany.
Gerke
P
P
Höpker
K
K
Hildebrandt
F
F
Kim
E
E
Walz
G
G
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D004847:Epithelial Cells / Q000378:metabolism; D051418:Focal Adhesion Kinase 2; D006801:Humans; D007685:Kidney Tubules, Collecting / Q000166:cytology; D020935:MAP Kinase Signaling System; D046911:Macromolecular Substances; D008565:Membrane Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130; D000070876:Tensins; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; C493841:BCAR1 protein, human; C493842:Bcar1 protein, mouse; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008840:Microfilament Proteins; C108725:NPHP1 protein, human; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D050717:Retinoblastoma-Like Protein p130; D000070876:Tensins; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C496053:Ptk2b protein, mouse