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

描述（由申请人提供）：NF-kB信号传导在适应性免疫应答中调节淋巴细胞的活化、增殖和效应子功能中具有关键作用。这一过程的失调导致免疫缺陷、自身免疫性疾病或肿瘤性疾病。在存在额外的共刺激信号的情况下，NF-kB通过TCR与MHC结合的抗原肽的接合或BCR与抗原的相互作用而被激活。蛋白激酶C？(PKC?) T细胞和蛋白激酶C的B细胞在抗原受体触发期间被募集到脂筏，并分别在TCR和BCR诱导的NF-κ B活化中起关键作用。CARMA 1 [半胱天冬酶募集结构域（CARD）膜相关鸟苷酸激酶（MAGUK）蛋白1，也称为CARD 11]，Bcl 10（B细胞淋巴瘤10）和MALT 1（粘膜相关淋巴组织淋巴瘤易位蛋白1）的三元复合物在PKC？和PKC β诱导B和T淋巴细胞中IkB激酶（IKK）的活化（图1）。CARMA 1似乎与细胞质膜组成型相关。在TCR刺激后，CARMA 1重新分布到免疫突触处的脂筏，以募集Bcl 10和MALT 1，形成CARMA 1-Bcl 10-MALT 1（CBM）复合物。目前没有关于CBM复合物或其组分蛋白质的结构信息。此外，尽管具有属于已知蛋白质家族的结构域，但CARMA 1、Bcl 10和MALT 1与任何已知蛋白质表现出非常有限的序列同源性。为了填补这一空白，我们提出了一个完整的全面的CBM复合物的结构分析，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为这个重要的信号复合体提供见解。 公共卫生相关性：CBM复合物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。CARMA 1过表达已在成人T细胞白血病、原发性胃B细胞淋巴瘤和弥漫性大B细胞淋巴瘤（DLBCL）中发现。在DLBCL（最常见的非霍奇金淋巴瘤形式）中，在CARMA 1的卷曲螺旋区域发现了CARMA 1的错义突变，其与组成性NF-κ B活化相关。在粘膜相关淋巴组织（MALT）淋巴瘤中发现了Bcl 10和MALT 1的染色体易位。MALT淋巴瘤中最常见的染色体畸变是t（11;18）（q21：q21）和t（14;18）（q32：q21）易位，约占所有MALT淋巴瘤的一半。前者易位产生包含cIAP 2的BIR结构域和MALT 1的meta-半胱天冬酶结构域以及组成性NF-κ B活化的融合蛋白。t（14;18）易位导致MALT 1基因定位于IG重链基因座。类似地，对于Bcl 10，t（1;14）（p22：q32）易位将Bcl 10置于IG重链基因座。这些易位可能通过MALT 1和Bcl 10过表达激活NF-κ B。总的来说，这些研究表明，CBM复合物是一个有吸引力的治疗目标的淋巴细胞肿瘤性疾病。

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.