Structure and Function of Tetraspanin Complexes

项目摘要 四跨膜蛋白是一个古老的和非常保守的家庭的四个通过跨膜蛋白- 在人类中有33个独特的成员-在许多不同的领域中具有重要但知之甚少的功能 细胞环境在四跨膜蛋白中，CD 81和C8亚家族在细胞凋亡中特别重要。 人类生物学CD 81是B细胞共受体复合物中CD 19的结合伴侣，是B细胞的关键调节因子 受体（BCR）信号传导。然而，关于CD 81与CD 82的动态关联如何， CD 19调节其与B细胞受体的结合以及诱导信号应答的能力，这是关键的 阻碍调节或靶向该途径的治疗努力的知识差距。四跨膜蛋白亚类 具有八个细胞外半胱氨酸残基（“C8”四跨膜蛋白）促进细胞的成熟和功能 跨膜金属蛋白酶ADAM 10在生理和疾病中具有许多重要作用。在 在免疫系统中，ADAM 10促进T细胞增殖和细胞因子产生，作为免疫系统的主要脱落酶。 低亲和力IgE受体CD 23，在T细胞受体的刺激下裂解Lag-3。Adam10 还催化配体依赖性生理Notch切割，这是Notch信号转导的重要步骤， 是负责阿尔茨海默病前体蛋白APP的组成型α分泌酶加工的蛋白酶， 导致产生无毒产物，而不是由β-内酰胺酶产生的毒性A-β（Aβ）片段。 分泌酶这项工作的目的是提供一个深入和全面的了解分子 使用结构、生物化学和动力学方法研究CD 81和C8四跨膜蛋白功能的基础， 建立在我们最近的进展，可视化的结构，CD 81在其自由和CD 19结合状态。到 为了实现这一目标，我们计划阐明CD 19-CD 81共受体复合物响应B的动力学 细胞活化，确定C8四跨膜蛋白识别ADAM 10的分子基础，并揭示如何识别细胞活化。 C8-四跨膜蛋白与ADAM 10的结合调节底物选择和蛋白水解活性。一起，成功 这些目标的完成将提供对CD 81如何调节信号转导的深入理解。 B细胞共受体，以及C8四跨膜蛋白如何影响ADAM 10金属蛋白酶功能。这些发现将 为未来针对这些重要生物过程的治疗工作提供信息。

Project Summary Tetraspanins are an ancient and exceptionally well-conserved family of four pass transmembrane proteins – numbering 33 unique members in humans – that have essential but poorly understood functions in many different cellular contexts. Among tetraspanin proteins, CD81 and the C8 subfamily stand out as particularly important in human biology. CD81 is a binding partner of CD19 in the B cell co-receptor complex, a key regulator of B cell receptor (BCR) signaling. Relatively little is known, however, about how the dynamic association of CD81 with CD19 regulates its association with the B cell receptor and ability to induce a signaling response, critical knowledge gaps that impede therapeutic efforts to modulate or target this pathway. The subset of tetraspanins with eight extracellular cysteine residues (the “C8” tetraspanins) facilitate the maturation and function of the transmembrane metalloprotease ADAM10, which has numerous important roles in physiology and disease. In the immune system, ADAM10 promotes T cell proliferation and cytokine production as the primary sheddase of the low-affinity IgE receptor CD23, and it cleaves Lag-3 in response to stimulation of the T cell receptor. ADAM10 also catalyzes ligand-dependent physiologic Notch cleavage, an essential step in Notch signal transduction, and is the protease responsible for constitutive alpha secretase processing of the Alzheimer’s precursor protein APP, resulting in production of a non-toxic product instead of the toxic A-beta (Aβ) fragment produced by beta- secretase. The objective of this work is to provide a deep and comprehensive understanding of the molecular basis for the function of CD81 and the C8 tetraspanins using structural, biochemical, and dynamic approaches, building from our recent progress in visualizing the structure of CD81 in its free and CD19-bound states. To achieve this goal, we plan to elucidate the dynamics of the CD19-CD81 co-receptor complex in response to B cell activation, determine the molecular basis for recognition of ADAM10 by C8 tetraspanins, and uncover how C8-tetraspanin binding to ADAM10 modulates substrate selection and proteolytic activity. Together, successful completion of these aims will provide a deep understanding of how CD81 modulates signal transduction by the B cell co-receptor, and how the C8 tetraspanins influence ADAM10 metalloprotease function. These findings will inform future therapeutic efforts targeting these important biological processes.