Dual fatty acylation of p59(Fyn) is required for association with the T cell receptor zeta chain through phosphotyrosine Src homology domain-2 interactions

The first 10 residues within the Src homology domain (SH)-4 domain of the S rc family kinase Fyn are required for binding to the immune receptor tyrosi ne-based activation motif (ITAM) of T cell receptor (TCR) subunits. Recentl y, mutation of glycine 2, cysteine 3, and lysines 7 and 9 was shown to bloc k binding of Fyn to TCR zeta chain ITAMs, prompting the designation of thes e residues as an ITAM recognition motif (Gauen, L.K.T., M,E. Linder, and A, S. Shaw. 1996. J, Cell Biol, 133:1007-1015), Here we show that these residu es do not mediate direct interactions with TCR ITAMs, but rather are requir ed for efficient myristoylation and palmitoylation of Fyn, Specifically, co expression of a K(7,9)A-Fyn mutant with N-myristoyltransferase restored myr istoylation, membrane binding, and association with the cytoplasmic tail of TCR zeta fused to CD8, Conversely, treatment of cells with 2-hydroxymyrist ate, a myristoylation inhibitor, blocked association of wildtype Fyn with z eta. The Fyn NH2 terminus was necessary but not sufficient for interaction with zeta and both Fyn kinase and SH2 domains were required, directing phos phorylation of zeta ITAM tyrosines and binding to zeta ITAM phosphotyrosine s. Fyn/zeta interaction was sensitive to octylglucoside and filipin, agents that disrupt membrane rafts. Moreover, a plasma membrane bound, farnesylat ed Fyn construct, G(2)A,C3S-FynKRas, was not enriched in the detergent inso luble fraction and did not associate with zeta. We conclude that the Fyn SH 4 domain provides the signals for fatty acylation and specific plasma membr ane localization, stabilizing the interactions between the Fyn SH2 domain a nd phosphotyrosines in TCR zeta chain ITAMs.