REGULATION OF CD28 SIGNAL TRNSDUCTION

描述(改编自《调查者摘要》)：在 对外来抗原的反应T细胞必须同时收到TCR信号和 共刺激信号。一种重要的T细胞共刺激受体是 CD28分子还具有保护T细胞免受 抗原诱导的无能和细胞凋亡。除了对以下问题的回应 外来抗原T细胞需要CD28信号来启动有害信号 自身免疫性疾病中对自身抗原的反应。因此，一种能力 专门操纵CD28信号将代表着一种有效的 控制这些异常免疫反应的手段。要确定 治疗的潜在分子靶点这一长期目标 建议理解CD28细胞内信号的性质 小路。先前的研究已经确定CD28信号涉及 PI3-激酶和GRB-2对酪氨酸磷酸化CD28的募集作用 细胞质尾巴。然而，有证据表明，其他信号 分子被招募到CD28尾巴上，这些分子发挥作用 CD28在信号转导中的重要作用。最近，额外的CD28 鉴定了结合蛋白。一种是以前没有描述过的双重- MAP激酶磷酸酶家族的特异性磷酸酶，MKP5，它 结合CD28尾部，不依赖于酪氨酸磷酸化。另一个是 与GRB-2相关但又不同的GRAP接头蛋白， 并且也只与磷酸化的CD28尾巴结合。初步证据 提示MKP5是CD28信号的负调节因子 转导。相反，GRAP可能在CD28中扮演积极的角色 发信号。具体地说，这里建议使用各种 分子遗传学、生化和细胞技术以1)证实 MKP5和GRAP分别具有负信号和正信号作用， 2)确定这些分子在CD28中的确切功能 信号转导途径。此外，使用了一种新型的酵母基 已在实验室中开发的遗传分析，建议 为了表征其他信号中间体结合 磷酸化的CD28胞浆尾巴。

DESCRIPTION (Adapted from Investigator's Abstract): To proliferate in response to foreign antigens T cells must receive both TCR signals and co-stimulatory signals. An important T cell co-stimulatory receptor is the CD28 molecule that additionally functions to protect T cells from antigen induced anergy and apoptosis. In addition to responses to foreign antigens T cells require CD28 signals to initiate harmful responses to self antigens in autoimmune disease. Therefore, an ability to specifically manipulate CD28 signals would represent an effective means of controlling these aberrant immune responses. To identify potential molecular targets for therapy the long-term aims of this proposal are to understand the nature of CD28 intracellular signaling pathways. Previous studies have determined that CD28 signaling involves recruitment of PI3-kinase and Grb-2 to the tyrosine phosphorylated CD28 cytoplasmic tail. However, there is evidence that other signaling molecules are recruited to the CD28 tail and that these molecules play important roles in CD28 signal transduction. Recently, additional CD28 binding proteins were identified. One is a previously un-described dual- specific phosphatase of the MAP kinase phosphatase family, MKP5, which binds the CD28 tail independent of tyrosine phosphorylation. Another is the GRAP adaptor protein, which is related to but distinct from Grb-2, and also binds only the phosphorylated CD28 tail. Preliminary evidence indicates that MKP5 functions as a negative regulator of CD28 signal transduction. In contrast, GRAP likely performs a positive role in CD28 signaling. Specifically, here it is proposed to use a variety of molecular genetic, biochemical and cellular techniques to 1) Confirm negative and positive signaling roles for MKP5 and GRAP respectively, and 2) Determine the precise function of these molecules in the CD28 signal transduction pathway. In addition, using a novel yeast-based genetic assay that has been developed in the laboratory, it is proposed to characterize other signaling intermediates that bind the phosphorylated CD28 cytoplasmic tail.