To elucidate the process of TCR-mediated signaling pathways in lipid rafts,
we constructed a chimeric molecule that localizes activated SHP-1 to rafts
. Raft targeting of activated SHP-1 in Jurkat-derived transfectants complet
ely inhibited the expression of CD69 and transcriptional factors after TCR
cross-linking. Whereas the inducible tyrosine phosphorylation of TCR zeta a
nd ZAP-70 and the kinase activity of Lck were intact, phosphorylated LAT wa
s rapidly dephosphorylated by raft targeting of activated SHP-1, leading to
defects in LAT activation and subsequent downstream signaling events. Intr
iguingly, recruitment of endogenous SHP-1 to rafts and its association with
LAT were dramatically increased after TCR engagement, suggesting that SHP-
1 is involved in raft-mediated T cell activation.