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Mol. Cell. Biol., May 1996, 2255-2263, Vol 16, No. 5
JP Northrop, MJ Pustelnik, AT Lu and JR Grove
Activation of the T-cell antigen receptor initiates a complex signaling
cascade leading to changes in cytokine gene transcription. Several proteins
containing Src homology 2 (SH2) domains, capable of interacting with
phosphotyrosine-containing sequences within other proteins, are involved in
the activation of signaling intermediates such as p2l(ras) and
phospholipase Cgamma1. In this study, we used dominant negative SH2 domains
to determine the importance of SH2 domain- containing proteins for T-cell
activation. We show that tandem SH2 domains of either Zap70 or Syk tyrosine
kinase are potent inhibitors of signaling initiated by the T-cell receptor
zeta chain in vivo while individual SH2 domains are ineffective. Thus,
while only the C-terminal SH2 domains appear to have significant affinity
for immunoreceptor tyrosine-based activation motifs in vitro, the
N-terminal SH2 domains are necessary in vivo. We find the spacing between
the tandem SH2 domains of Zap70 to be critical for in vivo interactions.
The SH2 domain of the adapter protein Grb2 is an effective inhibitor in our
dominant negative assay, although it has little affinity for immunoreceptor
tyrosine-based activation motifs. A single point mutation that abolishes
phosphotyrosine binding renders the Grb2 SH2 domain incapable of this
inhibition. In contrast, the SH2 domain of Shc does not inhibit this
signaling cascade. We conclude that Grb2, but not Shc, is involved in
T-cell receptor signaling.
Copyright © 1996, American Society for Microbiology
Characterization of the roles of SH2 domain-containing proteins in T- lymphocyte activation by using dominant negative SH2 domains
Affymax Research Institute, Santa Clara, California, USA.
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