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J. Exp. Med.,
Volume 189, Number 9, May 3, 1999 1383-1390
By



From the * Department of Microbiology and Immunology, Tohoku University School of Medicine,
Sendai 980-8575, Japan; the We molecularly cloned a new Grb2 family member, named Grf40, containing the common
SH3-SH2-SH3 motif. Expression of Grf40 is predominant in hematopoietic cells, particularly
T cells. Grf40 binds to the SH2 domain-containing leukocyte protein of 76 kD (SLP-76) via
its SH3 domain more tightly than Grb2. Incidentally, Grf40 binds to linker for activation of
T cells (LAT) possibly via its SH2 domain. Overexpression of wild-type Grf40 in Jurkat cells induced a significant increase of SLP-76-dependent interleukin (IL)-2 promoter and nuclear factor of activated T cell (NF-AT) activation upon T cell receptor (TCR) stimulation, whereas the COOH-terminal SH3-deleted Grf40 mutant lacked any recognizable increase in IL-2 promoter
activity. Furthermore, the SH2-deleted Grf40 mutant led to a marked inhibition of these regulatory activities, the effect of which is apparently stronger than that of the SH2-deleted Grb2 mutant. Our data suggest that Grf40 is an adaptor molecule involved in TCR-mediated signaling
through a more efficient interaction than Grb2 with SLP-76 and LAT.
Department of Pediatric Oncology, Institute of Development, Aging
and Cancer, Tohoku University, Sendai 980-8575, Japan; the § Research Institute, Miyagi Cancer
Center, Natori 981-1293, Japan; and
Core Research for Evolutional Science and Technology
(CREST), Japan Science and Technology Corporation, Tokyo 101-0062, Japan
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