Structure and Function of Tetraspanin Complexes

项目概要 四跨膜蛋白是一个古老且极其保守的四次跨膜蛋白家族 - 人类中有 33 个独特的成员——它们在许多不同的领域具有重要但人们知之甚少的功能 细胞环境。在四跨膜蛋白中，CD81 和 C8 亚家族在 人类生物学。 CD81 是 B 细胞辅助受体复合物中 CD19 的结合伴侣，B 细胞辅助受体复合物是 B 细胞的关键调节因子 受体（BCR）信号传导。然而，关于 CD81 与 CD19 调节其与 B 细胞受体的关联以及诱导信号传导反应的能力，这一点至关重要 知识差距阻碍了调节或针对该途径的治疗努力。四跨膜蛋白的子集 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 ADAM10，在生理学和疾病中具有许多重要作用。在 在免疫系统中，ADAM10 作为主要脱落酶促进 T 细胞增殖和细胞因子产生 低亲和力 IgE 受体 CD23，它会响应 T 细胞受体的刺激而裂解 Lag-3。亚当10 还催化配体依赖性生理性 Notch 裂解，这是 Notch 信号转导的重要步骤，并且 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 β-产生的有毒 A-β (Aβ) 片段 分泌酶。这项工作的目的是提供对分子的深入和全面的了解 使用结构、生化和动力学方法为 CD81 和 C8 四跨膜蛋白的功能奠定基础， 基于我们最近在可视化 CD81 自由状态和 CD19 结合状态结构方面取得的进展。至 为了实现这一目标，我们计划阐明 CD19-CD81 共受体复合物响应 B 的动态 细胞激活，确定 C8 四跨膜蛋白识别 ADAM10 的分子基础，并揭示如何 C8-四跨膜蛋白与 ADAM10 结合可调节底物选择和蛋白水解活性。齐心协力，成功 完成这些目标将有助于深入了解 CD81 如何通过 B 细胞辅助受体，以及 C8 四跨膜蛋白如何影响 ADAM10 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.