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Mol. Cell. Biol., 01 1998, 558-565, Vol 18, No. 1
RH Arch and CB Thompson
Members of the tumor necrosis factor (TNF)-nerve growth factor (NGF)
receptor family have been shown to be important costimulatory molecules for
cellular activation. 4-1BB and Ox40 are two recently described members of
this protein family which are expressed primarily on activated T cells. To
gain insight into the signaling pathways employed by these factors, yeast
two-hybrid library screens were performed with the cytoplasmic domains of
4-1BB and Ox40 as baits. TNF receptor- associated factor 2 (TRAF2) was
identified as an interacting protein in both screens. The ability of both
4-1BB and Ox40 to interact with TRAF2 was confirmed in mammalian cells by
coimmunoprecipitation studies. When the binding of the receptors to other
TRAF proteins was investigated, 4- 1BB and Ox40 displayed distinct binding
patterns. While 4-1BB bound TRAF2 and TRAF1, Ox40 interacted with TRAF3 and
TRAF2. Using deletion and alanine scanning analysis, we defined the
elements in the cytoplasmic domains of both receptors that mediate these
interactions. The 4-1BB receptor was found to have two independent
stretches of acidic residues that can mediate association of the TRAF
molecules. In contrast, a single TRAF binding domain was identified in the
cytoplasmic tail of Ox40. The cytoplasmic domains of both receptors were
shown to activate nuclear factor kappaB in a TRAF-dependent manner. Taken
together, our results indicate that 4-1BB and Ox40 bind TRAF proteins to
initiate a signaling cascade leading to activation of nuclear factor
kappaB.
Copyright © 1998, American Society for Microbiology
4-1BB and Ox40 are members of a tumor necrosis factor (TNF)-nerve growth factor receptor subfamily that bind TNF receptor-associated factors and activate nuclear factor kappaB
Department of Medicine, Howard Hughes Medical Institute, The University of Chicago, Illinois 60637, USA.
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