SIGNALING THROUGH CD27, A MEMBER OF THE TNFR FAMILY

通过 TNFR 家族成员 CD27 发出信号

• 批准号: 2694678
• 负责人: Prasad V. S. Kanteti
• 金额: $ 21.18万
• 依托单位: DANA-FARBER CANCER INST
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2694678
• 关键词: CD antigens; CD95 molecule; apoptosis; binding proteins; biological signal transduction; cytokine receptors; gene mutation; laboratory mouse; laboratory rabbit; molecular cloning; protein sequence; tumor necrosis factor alpha; yeast two hybrid system

CD27 belongs to the TNF-Receptor (TNFR) family, members of which regulate the propensity of a cell to grow or die. The ligand for CD27 is CD70, which belongs to the TNF family of ligands. Extensive work done by several groups have shown that CD27/CD70 interaction provides costimulatory signals for T cell growth and enhances B cell differentiation and Ig synthesis. Regulated expression of CD27 in mature thymocytes implies a role for it in thymic differentiation. A soluble form of the receptor (sCD27) has been detected in the serum of normal individuals and its levels were found to be elevated in patients with autoimmune disorders and certain B cell cancers. During our attempts to understand mechanisms underlying CD27 signaling, unexpectedly, we found that ligation of CD27 by CD70 transfectants resulted in apoptosis in the B cell lines Raji and Ramos. Since CD27 is clearly involved in costimulation and cell signaling with carefully regulated expression in vivo, we believe that CD27 induced apoptosis plays a major role in the clearance of activated T or B cell clones. The elevated sCD27 observed in patients with autoimmune disorders and B cell cancers may well contribute to the pathologic process by interfering with CD27 induced apoptosis. The cytoplasmic tails of TNFR1 and Fas (but not CD27) have the 'death domain' which is indispensable for induction of apoptosis through these receptors. How then is CD27 able to induce apoptosis? and does it occur in cells where Fas is ineffective? In order to understand the molecular mechanisms underlying this novel apoptotic pathway, using CD27 cytoplasmic tail as the bait in the yeast two hybrid system, we cloned a novel CD27 cytoplasmic tail binding protein Siva-1 which when expressed in various mammalian cells can induce apoptosis. Accordingly, we propose that Siva-1 mediates the apoptotic effects of CD27. Structural features of Siva-1 include a death domain homology region (DDHR), box-B like ring finger and a Zn finger like domain. We also identified an alternate splice form of Siva-1 (Siva-2) which lacks most of the DDHR and does not induce apoptosis, supporting our proposal that the DDHR of Siva-1 is the downstream conduit of the proapoptotic function of CD27. We propose to fully define the roles of Siva-1 and -2 in CD27 induced apoptosis, map the functional domains of Siva-1 and Siva-2 and determine whether Siva-1 and Siva-2 work in concert to regulate the apoptotic function of CD27. These studies should provide important insights into the regulatory role of cell surface molecules in T and B cell function.

CD27属于肿瘤坏死因子受体(TNFR)家族。 调节细胞生长或死亡的倾向。CD27的配体 是CD70，属于肿瘤坏死因子配体家族。广泛的工作已完成 几个小组的研究表明，CD27/CD70相互作用提供 共刺激信号促进T细胞生长和增强B细胞 分化和免疫球蛋白合成。CD27在人卵巢癌中的调控表达 成熟的胸腺细胞暗示了它在胸腺分化中的作用。一个 血清中检测到可溶性形式的受体(SCD27)。 在患者中发现正常人及其水平升高。 患有自身免疫性疾病和某些B细胞癌。在我们的 试图了解CD27信号转导的机制， 出乎意料的是，我们发现CD70转基因细胞对CD27的连接 导致B细胞系Raji和Ramos发生凋亡。自CD27以来 显然参与了共刺激和细胞信号转导 在体内精心调控的表达，我们认为CD27诱导 细胞凋亡在清除活化的T或B细胞中起主要作用 克隆人。自身免疫性疾病患者外周血中sCD27的升高 疾病和B细胞癌很可能是病理上的原因 通过干扰CD27诱导的细胞凋亡过程。细胞质 TNFR1和Fas的尾部(但不包括CD27)具有‘死亡结构域’，即 是通过这些受体诱导细胞凋亡所必需的。多么 那么CD27能诱导细胞凋亡吗？它是否发生在下列细胞中 Fas是无效的？为了了解其分子机制 在这一新的凋亡途径的基础上，使用CD27细胞质尾巴作为 在酵母双杂交系统中，我们克隆了一个新的CD27 胞质尾部结合蛋白SIVA-1在不同的细胞中表达 哺乳动物细胞可以诱导细胞凋亡。因此，我们建议 SIVA-1介导CD27的凋亡效应。的结构特点 SIVA-1包括死亡结构域同源区域(DDHR)、B盒样环 指状结构域和锌指状结构域。我们还确定了一名替补 SIVA-1(SIVA-2)的剪接体，它缺乏大部分DDHR，也不 诱导细胞凋亡，支持我们提出的SIVA-1的DDHR是 CD27促凋亡功能的下游管道。我们建议 充分认识SIVA-1和SIVA-2在CD27诱导的细胞凋亡中的作用 SIVA-1和SIVA-2的功能结构域并确定SIVA-1是否 与SIVA-2协同作用，调节CD27的凋亡功能。 这些研究应该为监管角色提供重要的见解 细胞表面分子在T细胞和B细胞中的功能。