Analysis of signal transduction of OX40/gp34 and its role in pathogenesis of hematologic diseases

(1) OX40信号的分子机制我们之前报道过OX40信号通过TRAF2和TRAF5导致NF-κB活化。TRAF3也与细胞质结构域或OX40结合，但在抑制NF-κB活化方面起负作用。在本研究中，我们发现TRAF3不影响nik介导的NF-κB激活，TRAF3的n端和c端缺失突变体都有抑制作用。这些结果表明，TRAF3在TRAF2和NIK之间的通路上抑制NF-κB的激活，这并不一定是由于OX40和TRAF2之间的结合受到竞争性抑制。(2) gp34的胞浆内信号传导我们检测了在小鼠上皮细胞系的人gp34稳定转染系MMCE-gp34和人脐静脉内皮细胞（HUVEC）中，当可溶性OX40刺激时，c-fos和c-jun mRNA的表达诱导情况。Northern blot分析显示，MMCE-gp34中c-fos和c-jun mRNA均受到诱导，HUVEC中c-jun mRNA受到诱导。这表明OX40/gp34系统的信号是双向的。(3)内皮细胞通过OX40/gp34系统共刺激T细胞纯化的CD4^+ T细胞在辐照的HUVEC存在下对固定化的抗cd3单抗有增殖反应。这种增殖反应被证明是由IL-2自分泌机制介导的，并被添加抗gp34单抗抑制。抗gp34的抑制作用强于抗icam -1和抗lfa1，提示OX40/gp34系统是内皮细胞共刺激的主要途径之一。(4) OX40/gp34在ATL细胞白血病发生中的可能作用我们研究了OX40信号与ATL细胞凋亡的关系。与MMCE-gp34共培养时，ATL组成性表达OX40，并对抗fas诱导的细胞凋亡产生抗性，而与MMCE-mock共培养则没有影响。这种抗凋亡的获得伴随着抗凋亡蛋白XIAP的表达诱导。这表明ATL细胞通过OX40/gp34系统接收到有利于生存的信号。少

(1) Moleclar mechanism of OX40 signalingWe previously reported that OX40 signaling leads to NF-κB activation via TRAF2 and TRAF5. TRAF3 also binds to the cytoplasmic domain or OX40 but functions rather negatively to suppress NF-κB activation. In the present study we found that TRAF3 did not affect NIK-mediated NF-κB activation and that both N-terminus and C-terminus deletion mutants of TRAF3 have inhibitory effects. These results indicate that TRAF3 suppresses NF-κB activation at the pathway between TRAF2 and NIK, which is not necessarily due to competitive inhibition of binding between OX40 and TRAF2.(2) Intracytoplasmic signaling of gp34We exzmined expression induction of c-fos and c-jun mRNA in MMCE-gp34, a human gp34 stable transfectant line of a mouse epithelial cell line as well as human umbilical vein endothelial cells (HUVEC) when stimulated wth soluble OX40. Northern blot analysis showed that both c-fos and c-jun mRNA were induced in MMCE-gp34, and c-jun mRNA in HUVEC upon bin … More ding of soluble OX40. This indicates that signlaing of the OX40/gp34 system is bidirectional.(3) Costimulation of T cells by endothelial cells via the OX40/gp34 systemPurified CD4^+ T cells responded with proliferation to immobilized anti-CD3 mAb in the presence of irradiated HUVEC.This proliferative response was shown to be mediated by IL-2 autocrine mechanism and inhibited by addition of anti-gp34 mAb. The inhibitory effect of anti-gp34 was stronger than that of anti-ICAM-1 or anti-LFA1, indicating that the OX40/gp34 system is one of the major pathways of costimulation by endothelial cells.(4) Possible role of the OX40/gp34 in the leukemogenesis of ATLWe studied the relationship between OX40 signals and apoptosis of ATL cells. ATL constitutively express OX40 and became resistant to anti-Fas-induced apoptosis when cocultured MMCE-gp34 while coculture with MMCE-mock had no effects. This acquisition of resistance to apoptosis was accompanied by expression induction of XIAP, an anti-apoptotic protein. It is suggested that ATL cells receive favoraous sigals for survival through the OX40/gp34 system. Less