REGULATION BY CELL SURFACE RECEPTOR ADP-RIBOSYLATION

该项目的总体目标是研究限制炎性T细胞，特别是细胞毒性T细胞（CTL）功能的调节机制。 将检验从裂解细胞释放的组分可能通过为T细胞上存在的胞外酶提供底物而参与T细胞调节的假设。 在可能的底物中，NAD是一种在细胞内丰富但其胞外浓度极低的底物。 NAD可能在CTL功能中起调节作用的观点的支持是存在分裂NAD的酶，其导致蛋白质中丝氨酸的翻译后修饰，称为单ADP核糖基化。 同时发现各种CTL功能被抑制。 我们建议探讨如何单ADP核糖基化的细胞表面分子对淋巴细胞，调节其功能。将测定淋巴细胞类别上的细胞表面ADP-核糖基转移酶（ADPRT）的表达，并将其与NAD的抑制作用相关联。 为了阐明负责这种调节电路的精确机制，提出了实验来鉴定被修饰的细胞表面蛋白。初步实验表明，修饰影响共受体，这导致T细胞受体信号传导的抑制。描述的方法来支持这一假设，特别是在考虑到受体相互关联的必要性，以传递激活信号。

The overall goal of this project is to examine a regulatory mechanisms that limits the function of inflammatory T cells, specifically cytotoxic T cells (CTL). The hypothesis will be examined that components released from lysing cells may be involved in T cell regulation by providing a substrate for an ecto-enzyme present on T cells. Among the possible substrates, NAD is one which is abundant inside cells but its extracellular concentration is exceedingly low. Support for the notion that NAD may play a regulatory role in CTL function is the presence of enzymes that split NAD leading to a posttranslational modification of arginines in proteins, known as mono-ADP-ribosylation. Concomitantly various CTL functions are found to be inhibited. We propose to explore how mono-ADP-ribosylation of cell surface molecules on lymphocytes, regulates their function. The expression of cell surface ADP- ribosyltransferase (ADPRT) on lymphocyte classes will be assayed and correlated with inhibitory effects of NAD. To elucidate the precise mechanisms responsible for this regulatory circuit, experiments are proposed to identify the cell surface proteins which are modified. Preliminary experiments suggest that the modification affects co- receptors and that this causes inhibition of T cell receptor signaling. Approaches are described to support this hypothesis specifically in view of the necessity for receptors to associate with each other in order to transmit activation signals.