| Differential interaction of Crkl with Cbl or C3G , Hef 1 , and gamma subunit immunoreceptor tyrosine based activation motif in signaling of myeloid high affinity Fc receptor for IgG ( Fc gamma RI ) . ^^^ To gain insight into the role of Crkl in myeloid ITAM signaling , we investigated Cbl Crkl and Crkl C3G interactions following Fc gamma RI aggregation in U937IF cells . ^^^ Fc gamma RI cross linking of U937IF cells results in the tyrosine phosphorylation of Cbl , Crkl , and Hef 1 , an increase in the association of Crkl with Cbl via direct SH 2 domain interaction and increased Crkl Hef 1 binding . ^^^ Anti Crkl immunoprecipitations demonstrate that the ITAM containing gamma subunit of Fc gamma RI is induced to form a complex with the Crkl protein , and Crkl binds to the cytoskeletal protein , Hef 1 . ^^^ The induced association of Crkl with Cbl , Hef 1 , and Fc gamma RI gamma after Fc gamma RI activation and the constitutive association between C3G and Crkl provide the first evidence that a Fc gamma RI gamma Crkl C3G complex may link ITAM receptors to the activation of Rap 1 in myeloid cells . . ^^^ |