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Lipid rafts are important for the association of RANK and TRAF6
하현일,HanBokKwak,SooWoongLee,Hong-HeeKim,이장희 생화학분자생물학회 2003 Experimental and molecular medicine Vol.35 No.4
Rafts, cholesterol- and sphingolipid-rich membrane microdomains, have been shown to play an im-portant role in immune cell activation. More re-cently rafts were implicated in the signal trans-receptor (TNFR) family. In this study, we provide evidences that the raft microdomain has a crucial role in RANK (receptor activator of NF-κB) signaling. We found that the majority of the ectopically expressed RANK and substantial portion of endogenous TRAF2 and TRAF6 were detected in the low-den-sity raft fractions. In adition, TRAF6 association with rafts was increased by RANKL stimulation. The disruption of rafts blocked the TRAF6 trans-teraction betwen RANK and TRAF6. Our obser-vations demonstrate that proper RANK signaling requires the function of raft membrane microdo-mains.
(Soo Woong Lee),(Sang In Han),(Hong Hee Kim),(Zang Hee Lee) 생화학분자생물학회 2002 BMB Reports Vol.35 No.4
The receptor activator of nuclear factor kappa B (RANK) is a member of the tumor necrosis factor (TNF) receptor superfamily. It plays a critical role in osteoclast differentiation, lymph node organogenesis, and mammary gland development. The stimulation of RANK causes the activation of transcription factors NF-kB and activator protein 1 (AP1), and the mitogen activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK). In the signal transduction of RANK, the recruitment of the adaptor molecules, TNF receptor-associated factors (TRAFs), is an initial cytoplasmic event. Recently, the association of the MAPK kinase kinase, transforming growth factor-β-activated kinase 1 (TAK1), with TRAF6 was shown to mediate the IL-1 signaling to NF-kB and JNK. We investigated whether or not TAK1 plays a role in RANK signaling. A dominant-negative form of TAK1 was discovered to abolish the RANK-induced activation of AP1 and JNK. The AP1 activation by TRAF2, TRAF5, and TRAF6 was also greatly suppressed by the dominant-negative TAK1. The inhibitory effect of the TAK1 mutant on RANK- and TRAF-induced NF-kB activation was also observed, but less efficiently. Our findings indicate that TAK1 is involved in the MAPK cascade and NF-kB pathway that is activated by RANK.
The Anti-proliferative Gene TIS21 Is Involved in Osteoclast Differentiation
( Soo Woong Lee ),( Han Bok Kwak ),( Hong Chan Lee ),( Seung Ku Lee ),( Hong Hee Kim ),( Zang Hee Lee ) 생화학분자생물학회 2002 BMB Reports Vol.35 No.6
The remodeling process of bone is accompanied by complex changes in the expression levels of various genes. Several approaches have been employed to detect differentially-expressed genes in regard to osteoclast differentiation. In order to identify the genes that are involved in osteoclast differentiation, we used a cDNA-array-nylon membrane. Among 1,200 genes that showed a measurable signal, 19 genes were chosen for further study. Eleven genes were up-regulated; eight genes were down-regulated. TIS21 was one of the up-regulated genes which were highly expressed in mature osteoclasts. To verify the cDNA microarray results, we carried out RT-PCR and real-time RT-PCR for the TIS21 gene. The TIS21 mRNA level was higher in differentiated-osteoclasts when compared to undifferentiated bone-marrow macrophages. Furthermore, the treatment with 1 μM of a TIS21 antisense oligonucleotide reduced the formation of osteoclasts from the bone-marrow-precursor cells by ∼30%. These results provide evidence for the potential role of TIS21 in the differentiation of osteoclasts.