Involvement of Lyp1 in TCR signaling. (A) Lyp immunoprecipitates from thymocytes (80 × 106cells) stimulated with anti-CD3 were blotted with antiphophotyrosine. A single phosphorylated band of 116 kD was detected coimmunoprecipitating with Lyp. Lyp protein loading was quantitated by anti-Lyp Western blot after stripping. (B) Immunoblotting with anti-Cbl identified the 116-kD phosphorylated protein as Cbl, whereas immunoblotting with anti-FAK or anti-p110 (subunit of PI-3 kinase) showed them not to be associated with Lyp. (C) Lyp1 was transfected into COS-7 cells and Cbl immunoprecipitates prepared from these and untransfected cells. Western blotting was performed with Lyp antibodies. The position of lyp is indicated by an arrow. Cbl immunoprecipitates were also prepared and blotted with antiphosphotyrosine (D) and then anti-cbl after stripping.
