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J. Cell Biol.,
Volume 145, Number 2, April 19, 1999 377-389
Chain through Phosphotyrosine-Src Homology
Domain-2 Interactions
Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York 10021
The first 10 residues within the Src homology
domain (SH)-4 domain of the Src family kinase Fyn are
required for binding to the immune receptor tyrosine-based activation motif (ITAM) of T cell receptor
(TCR) subunits. Recently, mutation of glycine 2, cysteine 3, and lysines 7 and 9 was shown to block binding of Fyn to TCR
chain ITAMs, prompting the designation of these 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 residues do not mediate direct interactions with TCR ITAMs, but rather are required for efficient myristoylation and palmitoylation of Fyn. Specifically, coexpression of a K7,9A-Fyn mutant with N-myristoyltransferase
restored myristoylation, membrane binding, and association with the cytoplasmic tail of TCR
fused to CD8.
Conversely, treatment of cells with 2-hydroxymyristate, a myristoylation inhibitor, blocked association of wild-type Fyn with
. The Fyn NH2 terminus was necessary
but not sufficient for interaction with
and both Fyn kinase and SH2 domains were required, directing phosphorylation of
ITAM tyrosines and binding to
ITAM phosphotyrosines. Fyn/
interaction was sensitive to octylglucoside and filipin, agents that disrupt
membrane rafts. Moreover, a plasma membrane bound,
farnesylated Fyn construct, G2A,C3S-FynKRas, was not
enriched in the detergent insoluble fraction and did not
associate with
. We conclude that the Fyn SH4 domain provides the signals for fatty acylation and specific
plasma membrane localization, stabilizing the interactions between the Fyn SH2 domain and phosphotyrosines in TCR
chain ITAMs.
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