FUNCTIONAL STUDIES OF HTM4, A CD20/FCE RIB HOMOLOGUE

描述(改编自调查人员摘要)：HTm4是一种新的 发现了编码4-跨膜的造血细胞特异性基因 与B细胞特异性抗原CD20同源的蛋白质和β-亚基 高亲和力IgE Fc受体FcecRIB。蛋白质结构 三个基因在同一染色体上的相似性和定位 II qI2-13.1中的区域提供了第一个实质性证据 4-跨膜蛋白家族。有数据表明，CD20是 钙离子通道。CD20和HTm4很可能与 膜蛋白，因为FceRIB是形成的复合体的一条链 肥大细胞上的高亲和力受体Far IgE及其功能 由FceRI转换的信号的放大器。这三个白细胞 蛋白质与基础研究和临床研究都高度相关。 应用：抗CD20抗体用于临床试验 非霍奇金B细胞淋巴瘤的治疗与遗传学和生物学资料 提示包括HTm4在内的FceRIB变异是导致IgE的原因之一 响应性。我们正在进行遗传关联研究，在 与牛津大学合作，看看HTm4是否有一个专业 对过敏症和哮喘的影响。 这是一项研究这一细胞和分子功能的建议。 本实验室发现了一种新的造血特异性基因HTm4。 该基因具有在原始G0中表达的显著特征 造血干细胞，但在非静止干细胞中被关闭， 处于增殖和分化阶段。小区的HTM4代码 与分子相互作用的表膜蛋白(TRAF蛋白和 KAP)对两条重要的细胞通路至关重要，即细胞凋亡/转录 激活和细胞周期。HTM4激活核因子-kB。所有这些证据 提示HTm4是一种新的可能的受体，介导重要的 造血干细胞中的信号转导。HTm4的作用可能与 循环细胞比GO造血祖细胞多。我们的目标是 通过以下方式确定HTm4是否参与干细胞周期和分化 (I)反义和反义抑制Htm4在G0细胞中的表达 显性否定策略，使用功能分离的G0干细胞； (Ii)在积极的自行车运动中过度表达野生型或显性阴性的HTm4 CD34造血干细胞。我们将进一步调查，看看HTm4是否 在(III)特应性和哮喘以及对细胞凋亡的调节中有任何作用 计划；以及(4)阐明其与KAP和其他项目互动的性质 免疫共沉淀技术在哺乳动物细胞中表达traf相关蛋白。 这一提议不仅将导致关于HTm4的新发现，而且还将导致 更好地理解一种新的重要信号通路和 可能会对免疫疾病的机制和它们的 治疗。

DESCRIPTION (Adapted from Investigator's abstract): HTm4 is a newly discovered hematopoietic cell-specific gene encoding a 4-transmembrane protein homologous to the B cell-specific antigen CD20, and the beta-subunit of the high affinity IgE Fc receptor, FcecRIB. Protein structural similarities and the localization of all three genes to the same chromosomal region in II qI2-13.1 provide the first substantial evidence for a distinct family of 4-transmembrane proteins. There are data to suggest that CD20 is a Ca2+ channel. It seems likely that CD20 and HTm4 are associated with membrane proteins since the FceRIB is one chain of the complex which forms the high affinity receptor far IgE on mast cells and functions as an amplifier of signals transduced by the FceRI. These three leucocyte proteins are highly relevant for both basic research and clinical applications: Anti-CD20 antibody is used in clinical trials in the treatment of non-Hodgkin's B-cell lymphoma and genetic and biological data suggest that variants of FceRIB, including HTm4, are one cause of IgE responsiveness. We are conducting genetic association studies, in collaboration with the University of Oxford, to see if HTm4 has a major impact on atopy and asthma. This is a proposal to study the cellular and molecular function of this novel hematopoietic-specific gene identified in our laboratory named HTm4. The gene has the distinctive feature of being expressed in primitive G0 hematopoietic stem cells but is shut off in non-quiescent stem cells that are in the proliferating and differentiating phase. HTm4 codes for a cell surface membrane protein that interacts with molecules (TRAF proteins and KAP) essential to two important cellular pathways, apoptosis/transcriptional activation and cell cycle. HTm4 activates NF-kB. All these evidence indicate that HTm4 is a novel putative receptor that mediates important signaling in hematopoietic stem cells. The role of HTm4 may be different in cycling cells than in GO hematopoietic progenitors. Our aims are to determine if HTm4 is involved in stem cell cycling and differentiation by (i) inhibiting the expression of HTm4 in G0 cells with antisense and dominant negative strategies, using functionally isolated G0 stem cells; (ii) over-expressing wild type or dominant-negative HTm4 in actively cycling CD34+ hematopoietic stem cells. We will further investigate to see if HTm4 has any role in (iii) atopy and asthma and in modulation of the apoptotic program; and (iv) elucidate the nature of its interaction with KAP and other TRAF-related proteins in mammalian cells by coimmunoprecipitation technique. This proposal will not only lead to new findings about HTm4 but also to a better understanding of a novel signaling pathway of emerging importance and likely to fresh insights into mechanisms of immune diseases and their treatment.