Structural and functional studies of sTALL-1

TALL-1最近被鉴定为肿瘤坏死因子(TNF)配体家族的成员，它能刺激B细胞的增殖和免疫球蛋白的分泌。在小鼠中过表达TALL-1会导致自身免疫样症状，如成熟B细胞数量增加，类风湿因子水平升高，循环免疫复合体，抗DNA自身抗体，以及肾脏中Ig沉积。TALL-1的两种受体已被鉴定，它们是BCMA和TACI。BCMA是肿瘤坏死因子受体家族(TNFR)的一种孤儿受体，由B细胞或B细胞来源的细胞特异性表达，并且只含有一个富含半胱氨酸的基序，与其他家族成员的三到四个基序形成鲜明对比。Tall-1(Stall-1)的功能可溶部分的结构已被确定为3.0埃单位。Stall-1通过新颖的三聚体-三聚体相互作用形成病毒样结构。这种类似病毒的结构也存在于溶液中。我们推测这种新的结构可能是体内TALL-1的功能单位。最后，通过肿瘤坏死因子/肿瘤坏死因子受体从细胞膜外到细胞膜内的信号转导还不是很清楚。本研究的目的是通过X射线结晶学的研究，阐明TALL-1和TALL-1受体的独特调控机制以及整个肿瘤坏死因子/肿瘤坏死因子受体超家族成员的普遍调控机制。还将使用其他方法，如电子显微镜、单分子跟踪三维显微镜重建技术、诱变、动态光散射和超速离心法。提出了三个具体目标。目的1：STALL-1的结构和功能鉴定。目的2：确定Stall-1与BCMA和TACI胞外结构域相互作用的结构基础。目的3：研究TALL-1、BCMA和TACI通过细胞膜的信号转导机制。从上述目标获得的所有信息都可用于确定药物开发的分子靶点，以对抗由TALL-1或其他肿瘤坏死因子家族成员故障引起的自身免疫性疾病和癌症。

TALL-1 was recently identified as a member of the tumor necrosis factor (TNF) ligand family, which stimulates B cell proliferation, and the secretion of immunoglobulins. Overexpression of TALL-1 in mice lead to autoimmune-like manifestations such as increased number of mature B cells, high levels of rheumatoid factors, circulating immune complexes, anti- DNA autoantibodies, and Ig deposition in the kidney. Two receptors for the TALL-1 have been identified, which are BCMA and TACI. BCMA, an orphan receptor of the TNF receptor family (TNFR), is specifically expressed by B cells or B cell derived cells and contains only one cysteine rich motif contrasting three to four motifs in other family members. The structure of the functional soluble portion of TALL-1 (sTALL-1) has been determined at 3.0 Angstrom units. sTALL-1 forms a virus-like structure through novel trimer-trimer interactions. This virus- like structure also exists in solution. We speculate that this novel structure could be the functional unit for TALL-1 in vivo. Finally, signal transduction from outside the cell membrane to inside the cell membrane by TNF/TNFR is not clearly understood. The goal of this proposal is to elucidate the unique regulation mechanisms of TALL-1 and TALL-1 receptors and universal mechanisms for the whole TNF/TNFR super family members through x- ray crystallography. Other approaches such as electron microscopy, single molecule tracking 3-D microscopy rebuilding techniques, mutagenisis, dynamic light scattering, and ultracentrifugation will also be used. Three specific aims are proposed. Aim 1: Structural and functional characterization of sTALL-1. Aim 2: Determining the structural basis of sTALL-1 interaction with extra cellular domains of BCMA and TACI. Aim 3: Characterizing the signal transduction mechanisms of TALL-1 BCMA or TACI through the cell membrane. All information derived from the above goal can be used to identify molecular targets for drug development against autoimmune diseases and cancer induced by TALL-1 or other TNF family member malfunctioning.