CD40 signalings play crucial roles in B-cell function.To identify molecules which transduce CD40 signalings, we have utilized the yeast two-hybrid system to clone cDNAs encoding proteins that bind the cytoplasmic tail of CD40. A cDNA encoding a putative signal transducer, designated TRAF6, has been molecularly cloned. TRAF6 has a tumor necrosis factor receptor (TNFR)-associated factor (TRAF) domain in its carboxyl terminus and has a RING finger domain, a cluster of zinc fingers and a coiled-coil domain, which are also present in other TRAF family proteins. TRAF6 does not associate with the cytoplasmic tails of TNFR2, CD30, lymphotoxin-␤ receptor, and LMP1 of Epstein-Barr virus. Deletion analysis showed that residues 246 -269 of CD40 which are required for its association with TRAF2, TRAF3, and TRAF5 are dispensable for its interaction with TRAF6, whereas residues 230 -245 were required. Overexpression of TRAF6 activates transcription factor NFB, and its TRAF-C domain suppresses NFB activation triggered by CD40 lacking residues 246 -277. These results suggest that TRAF6 could mediate the CD40 signal that is transduced by the amino-terminal domain (230 -245) of the CD40 cytoplasmic region and appears to be independent of other known TRAF family proteins.

N.Kobayashi and Y.Kadono contributed equally to this workSignals emanating from the receptor for interleukin-1 (IL-1), lipopolysaccharide (LPS) or osteoclast differentiation factor/receptor activator of NFkB ligand (ODF/RANKL) stimulate transcription factors AP-1 through mitogen-activated protein kinase (MAPK) activation and NFkB through IkB kinase (IKK) activation. These kinases are thought to be activated by tumor necrosis factor receptor-associated factor 6 (TRAF6). However, molecular mechanisms by which TRAF6 activates various downstream kinases remain to be elucidated. We identi®ed functional domains of TRAF6 under physiological conditions established by appropriate expression of TRAF6 mutants in TRAF6-de®cient cells. In IL-1 and LPS signaling pathways, the RING ®nger and ®rst zinc ®nger domains are not required for NFkB activation but are required for full activation of MAPK. However, IL-1 and LPS signals utilize distinct regions within the zinc ®nger domains of TRAF6 to activate NFkB. Furthermore, the RING ®nger domain is not required for differentiation of splenocytes to multinuclear osteoclasts, but is essential for osteoclast maturation. Thus, TRAF6 plays essential roles in both the differentiation and maturation of osteoclasts by activating various kinases via its multiple domains.

No abstract

We performed optical pulse propagation experiments in a system in which two ultrahigh-Q silica microspheres of different diameters were coupled in tandem to a fiber taper to yield coupled-resonator-induced transparency. Nearly Gaussian-shaped optical pulses propagated with a large positive delay of 8.5 ns through a transparent frequency window, without significant attenuation, amplification, or pulse deformation, demonstrating classical analogy of the extremely slow light obtained with electromagnetically induced transparency.