Hamawy M M, Minoguchi K, Swaim W D, Mergenhagen S E, Siraganian R P
Laboratory of Immunology, NIDR, National Institutes of Health, Bethesda, Maryland 20892-1188, USA.
J Biol Chem. 1995 May 19;270(20):12305-9. doi: 10.1074/jbc.270.20.12305.
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.
粘着斑激酶pp125FAK是一种新的非受体蛋白酪氨酸激酶，在包括肥大细胞在内的不同细胞中表达。在此我们报告，在肥大细胞类似物大鼠嗜碱性白血病（RBL-2H3）细胞中，一种77 kDa的蛋白与pp125FAK相关联。当对pp125FAK免疫沉淀物进行体外激酶分析时，pp125FAK和一种77 kDa蛋白的酪氨酸上有显著的磷酸化。通过V8蛋白酶消化图谱分析以及用两种不同的抗pp125FAK抗体进行免疫印迹分析，发现该77 kDa蛋白与pp125FAK不同。这种与Fak相关的蛋白或FAP在RBL-2H3细胞中被检测到，但在成纤维细胞中未被检测到。高亲和力IgE受体FcεRI的聚集诱导了FAP在体内的酪氨酸磷酸化。然而，来自FcεRI聚集细胞的免疫沉淀物中FAP的体外磷酸化显著降低。这两种FcεRI介导的效应都因细胞粘附而增强。FAP与非酪氨酸磷酸化的pp125FAK有很强的关联。因此，这种相互作用似乎不是由Src同源2结构域介导的。这些数据共同表明FAP与pp125FAK相关联，并提示FAP可能在FcεRI信号传导中发挥作用。
