Molecular elucidation of the CBM complex in NF-kappaB activation by antigen recep

描述(申请人提供)：在适应性免疫反应中，核因子-kB信号在调节淋巴细胞的激活、增殖和效应功能方面起着至关重要的作用。放松对这一过程的管制会导致免疫缺陷、自身免疫性疾病或肿瘤疾病。在其他共刺激信号存在的情况下，通过TCR与MHC结合的抗原肽或BCR与抗原的相互作用来激活NF-kB。蛋白激酶C？(PKC？)T细胞和B细胞的PKC在抗原受体激活过程中被招募到脂筏中，并分别在TCR和BCR诱导的NF-kB激活中发挥关键作用。CARMA1[caspase募集结构域(CARD)膜相关鸟氨酸蛋白1，又称CARD11]、Bcl10(B细胞淋巴瘤10)和MALT1(粘膜相关淋巴组织淋巴瘤转位蛋白1)三元复合体作用于PKC？和PKC？，以诱导B和T淋巴细胞中IKB激酶(IKK)的激活(图1)。CARMA1似乎与细胞膜有结构性的联系。在TCR刺激下，CARMA1被重新分布到免疫突触的脂筏上，以招募Bcl10和MALT1形成CARMA1-Bcl10-MALT1(CBM)复合体。目前还没有关于煤层气复合体或其组成蛋白的结构信息。此外，尽管CARMA1、BCL10和MALT1具有属于已知蛋白质家族的结构域，但它们与任何已知蛋白质的序列同源性都非常有限。为了填补这一空白，我们建议对CBM复合体进行全面的结构分析，包括其组装机制、构象变化、酶活性和翻译后修饰。这些研究将不可避免地提供对这一重要信号复合体的见解。 公共卫生相关性：CBM复合体中的蛋白质在非霍奇金淋巴瘤中起关键作用，可能是真正的癌基因。CARMA1在成人T细胞白血病、原发胃B细胞淋巴瘤和弥漫性大B细胞淋巴瘤(DLBCL)中有过表达。在最常见的非霍奇金淋巴瘤DLBCL中，在CARMA1的卷曲线圈区域发现了CARMA1的错义突变，该错义突变与结构性的NF-kB激活有关。在黏膜相关淋巴组织(MALT)淋巴瘤中发现了Bcl10和MALT1的染色体易位。MALT淋巴瘤中最常见的染色体异常是t(11；18)(q21：q21)和t(14；18)(q32：q21)易位，约占所有MALT淋巴瘤的一半。前者的易位产生了一种融合蛋白，包括cIAP2的BIR结构域和MALT1的Meta-caspase结构域，以及结构性的NF-kB激活。T(14；18)易位导致MALT1基因定位于Ig重链基因。同样，对于Bcl10，t(1；14)(p22：q32)易位将Bcl10置于Ig重链上。这些易位可能通过MALT1和Bcl10的过度表达激活了核因子-kB。总之，这些研究表明，CBM复合体是一个有吸引力的淋巴细胞肿瘤性疾病的治疗靶点。

DESCRIPTION (provided by applicant): NF-kB signaling has a crucial role in regulating the activation, proliferation and effector functions of lymphocytes in adaptive immune responses. Deregulation of this process results in immunodeficiency, autoimmune diseases, or neoplastic disorders. In the presence of additional co-stimulatory signals, NF-kB is activated by the engagement of TCR with MHC-bound antigen peptides or the interaction of BCR with antigens. The protein kinase C ? (PKC?) of T-cells and PKC¿ of B-cells are recruited to lipid rafts during antigen-receptor triggering and play key roles in TCR- and BCR-induced NF-kB activation, respectively. The ternary complex of CARMA1 [caspase-recruitment domain (CARD) membrane-associated guanylate kinase (MAGUK) protein 1, also known as CARD11], Bcl10 (B-cell lymphoma 10) and MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) acts downstream of PKC? and PKC¿ to induced activation of the IkB kinase (IKK) in both B and T lymphocytes (Figure 1). CARMA1 appears to be constitutively associated with the cytoplasmic membrane. Upon TCR stimulation, CARMA1 is redistributed to the lipid rafts at the immunological synapse to recruit Bcl10 and MALT1 to form the CARMA1-Bcl10-MALT1 (CBM) complex. No structural information is currently available on the CBM complex or its component proteins. In addition, despite having domains that belong to known protein families, CARMA1, Bcl10 and MALT1 exhibit very limited sequence homology to any of the known proteins. To fill this gap, we propose a complete comprehensive structural analysis on the CBM complex, including its assembly mechanisms, conformational changes, enzymatic activities and post-translational modifications. These studies will inevitably provide insights into this important signaling complex. PUBLIC HEALTH RELEVANCE: The proteins in the CBM complex play critical roles in Non-Hodgkin's lymphomas and may be bona fide oncogenes. CARMA1 overexpression has been found in adult T-cell leukemia, primary gastric B-cell lymphoma, and diffuse large B-cell lymphoma (DLBCL). In DLBCL, the most common form of non-Hodgkin's lymphoma, missense mutations of CARMA1 have been found at the coiled coil region of CARMA1, which correlate with constitutive NF-kB activation. Chromosomal translocations of both Bcl10 and MALT1 have been found in mucosa-associated lymphoid tissue (MALT) lymphoma. The most frequent chromosomal aberrations in MALT lymphoma are the t(11;18)(q21:q21) and t(14;18)(q32:q21) translocations, which account for about half of all MALT lymphoma. The former translocation creates a fusion protein comprising the BIR domains of cIAP2 and the meta-caspase domain of MALT1 and constitutive NF-kB activation. The t(14;18) translocation results in positioning of the MALT1 genes to the Ig heavy chain locus. Similarly for Bcl10, the t(1;14)(p22:q32) translocation places the Bcl10 to the Ig heavy chain locus. These translocations likely activate NF-kB through MALT1 and Bcl10 overexpression. Collectively, these studies suggest that the CBM complex is an attractive therapeutic target neoplastic disorders of the lymphocytes.