Induction of activator protein (AP)-1 and nuclear factor-kappaB by CD28 stimulation involves both phosphatidylinositol 3-kinase and acidic sphingomyelinase signals.
Induction of activator protein (AP)-1 and nuclear factor-kappaB by CD28 stimulation involves both phosphatidylinositol 3-kinase and acidic sphingomyelinase signals.
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CD28 刺激诱导激活蛋白 (AP)-1 和核因子 kappaB 涉及磷脂酰肌醇 3-激酶和酸性鞘磷脂酶信号。
作者：
C. Edmead;Y. I. Patel;A. Wilson;G. Boulougouris;N. Hall;S. Ward;D. Sansom
理解CD 28受体连接后的信号传导事件的主要障碍来自于CD 28作为TCR接合的共刺激物的事实，使得难以评估CD 28信号与TCR信号不同的相对贡献。为了克服这个问题，我们已经利用了这样的观察结果，即活化的人T细胞母细胞可以在不存在抗原攻击的情况下通过CD 28表面分子刺激;因此，我们已经能够观察正常T细胞对孤立的CD 28活化的反应。使用这个系统，我们观察到，CD 28刺激B7转染的CHO细胞诱导T细胞的增殖反应，这是不伴随着可测量的IL-2的生产。然而，随后的转录因子生成分析显示，B7刺激诱导激活蛋白-1（AP-1）和核因子-κ B（NF-κ B）复合物，但不诱导NF-AT。相比之下，II类MHC/超抗原与TCR的接合，无论有或没有CD 28连接，都导致NF-AT、AP-1和NF-κ B的诱导以及IL-2的产生。使用选择性抑制剂，我们研究了参与CD 28介导的AP-1和NF-κ B诱导的信号通路。这表明NF-κ B的产生对酸性鞘磷脂酶抑制剂氯喹敏感，但对磷脂酰肌醇3-激酶抑制剂渥曼青霉素不敏感。而AP-1的产生被渥曼青霉素抑制，对氯喹也不敏感。这些数据表明，在活化的正常T细胞，CD 28衍生的信号可以刺激增殖至少部分通过NF-κ B和AP-1的产生，这种反应使用酸性鞘磷脂酶和磷脂酰肌醇3-激酶连接的途径。
A major obstacle in understanding the signaling events that follow CD28 receptor ligation arises from the fact that CD28 acts as a costimulus to TCR engagement, making it difficult to assess the relative contribution of CD28 signals as distinct from those of the TCR. To overcome this problem, we have exploited the observation that activated human T cell blasts can be stimulated via the CD28 surface molecule in the absence of antigenic challenge; thus, we have been able to observe the response of normal T cells to CD28 activation in isolation. Using this system, we observed that CD28 stimulation by B7-transfected CHO cells induced a proliferative response in T cells that was not accompanied by measurable IL-2 production. However, subsequent analysis of transcription factor generation revealed that B7 stimulation induced both activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) complexes, but not NF-AT. In contrast, engagement of the TCR by class II MHC/superantigen, either with or without CD28 ligation, resulted in the induction of NF-AT, AP-1, and NF-kappaB as well as IL-2 production. Using selective inhibitors, we investigated the signaling pathways involved in the CD28-mediated induction of AP-1 and NF-kappaB. This revealed that NF-kappaB generation was sensitive to chloroquine, an inhibitor of acidic sphingomyelinase, but not to the phosphatidylinositol 3-kinase inhibitor, wortmannin. In contrast, AP-1 generation was inhibited by wortmannin and was also variably sensitive to chloroquine. These data suggest that in activated normal T cells, CD28-derived signals can stimulate proliferation at least in part via NF-kappaB and AP-1 generation, and that this response uses both acidic sphingomyelinase and phosphatidylinositol 3-kinase-linked pathways.