title: A 77-kDa protein associates with pp125FAK in mast cells and becomes tyrosine-phosphorylated by high affinity IgE receptor aggregation.
abstract: The focal adhesion kinase, pp125FAK, is a novel non-receptor protein tyrosine kinase expressed in different cells including mast cells. Here we report that a 77-kDa protein associates with pp125FAK in the mast cell analog, rat basophilic leukemia (RBL-2H3) cells. When pp125FAK immunoprecipitates were subjected to an in vitro kinase assay, there was prominent phosphorylation on tyrosine of pp125FAK and of a 77-kDa protein. By V8 protease digestion mapping and by immunoblotting with two different anti-pp125FAK antibodies, the 77-kDa protein was distinct from pp125FAK. This Fak Associated Protein or FAP was detected in RBL-2H3 cells but not in fibroblasts. The aggregation of the high affinity IgE receptor, Fc epsilon RI, induced the in vivo tyrosine phosphorylation of FAP. However, there was a marked decrease in the in vitro phosphorylation of FAP in the immunoprecipitates from Fc epsilon RI aggregated cells. Both of these Fc epsilon RI-mediated effects were enhanced by cell adhesion. There was strong association of FAP with non-tyrosine-phosphorylated pp125FAK. Thus this interaction does not appear to be mediated by the Src homology 2 domain. Together the data indicate that FAP associates with pp125FAK and suggest that FAP may play a role in Fc epsilon RI signaling.
authors.affiliation: Laboratory of Immunology, NIDR, National Institutes of Health, Bethesda, Maryland 20892-1188, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Hamawy
authors.forename: K
authors.initials: K
authors.lastname: Minoguchi
authors.forename: W D
authors.initials: WD
authors.lastname: Swaim
authors.forename: S E
authors.initials: SE
authors.lastname: Mergenhagen
authors.forename: R P
authors.initials: RP
authors.lastname: Siraganian
mesh_terms: D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007073:Immunoglobulin E / Q000276:immunology*; D007152:Immunologic Capping; D015471:Leukemia, Basophilic, Acute / Q000473:pathology; D008407:Mast Cells / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D017455:Receptors, IgE / Q000276:immunology*; D014407:Tumor Cells, Cultured
chemical_list: D015815:Cell Adhesion Molecules; D009363:Neoplasm Proteins; D017455:Receptors, IgE; D007073:Immunoglobulin E; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; C496052:Ptk2 protein, rat