Subcellular Mechanisms pf Platelet Activation

血小板激活的亚细胞机制

• 批准号: 7474410
• 负责人: LAWRENCE F BRASS
• 金额: $ 47.78万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7474410
• 关键词: Binding; Blood Platelets; Blood Vessels; CD100 antigen; CD72 gene; Cell Adhesion Molecules; Cell surface; Cyclophosphamide; Cytoplasmic Tail; Data; Deposition; Ensure; Ephrin Receptor EphB1; Ephrin-A1; Ephrin-B1; Event; Family; Family member; Funding; Genes; Goals; Growth; Hemorrhage; Hemostatic Agents; In Vitro; Injury; Integrins; Knockout Mice; Ligand Binding; Ligands; Localized; Microscopy; Modeling; Molecular; Mus; Pathologic; Phosphotransferases; Platelet Activation; Platelet aggregation; Play; Process; Proteins; Recruitment Activity; Role; Scaffolding Protein; Signal Transduction; Surface; Testing; Thrombus; Time; Tissues; Work; base; comparative; digital; in vivo; instrument; novel; plexin; prevent; protein protein interaction; receptor; response to injury; restraint; scaffold

Platelet activation begins with the initial deposition of platelets on a damaged vessel wall, then continues as additional platelets are recruited and adhere to each other. These events bring platelets into stable contact with each other, forming junctions where protein:protein interactions can occur between adjacent platelets. The long term goal of this project is to understand how events at platelet junctions contribute to the platelet response to injury. Our hypothesis is that 1) relevant signaling continues after platelet aggregation has begun, 2) some of the signaling arises from interactions between molecules other than integrins on the surface of adjacent platelets, and 3) these contact-dependent interactions at junctions can serve either as positive regulators, promoting the growth and stability of the hemostatic mass to prevent re-bleeding, or as negative regulators, limiting growth and stability so that vascular occlusion is avoided. During the most recent funding period we have identified ephrin B1 and semaphorin 4D on the platelet surface, and shown that the binding of these ligands to their respective receptors (EphB1 and EphA4 for ephrinBI; CD72 and plexin B1 for sema4D) promotes thrombus growth. We have also determined that ESAM, a putative cell adhesion molecule in the CTX family, translocates to junctions when platelets are activated and then acts as a negative regulator, so that loss of ESAM expression promotes, rather than impairs, extension of the platelet mass. The studies described in this proposal are divided into four specific aims focusing on platelet junctions and contact-dependent interactions. Aim #1 will test our current model that ESAM is a negative regulator of platelet:platelet interactions and explore the consequences of a loss of ESAM function on platelet activation using an existing line of ESAM knockout mice. Aim #2 will focus on the molecular basis for ESAM's contribution, starting with our recent identification of two scaffold proteins, NHERF-1 and CAL, that bind to the ESAM cytoplasmic domain. Aim #3 is a comparative analysis of the three other CTX family members expressed in platelets (JAM-A, JAM-C and CD226) to determine whether their role is the same as ESAM. Initial results obtained with JAM-A knockout mice, suggest that this may be the case. Aim #4 is devoted to the characterization of additional junction molecules in platelets, starting with ephrin A1 on platelets and continuing with an unbiased search for novel proteins.

血小板活化始于血小板最初沉积在受损的血管壁上，然后继续 额外的血小板被募集并相互粘附。这些事件使血小板稳定接触 彼此之间形成连接，相邻血小板之间可以发生蛋白质：蛋白质相互作用。 该项目的长期目标是了解血小板连接处的事件如何影响血小板 对伤害的反应。我们的假设是 1）相关信号传导在血小板聚集后继续存在 开始，2）一些信号传导源自除整合素之外的分子之间的相互作用 相邻血小板的表面，3）这些连接处依赖于接触的相互作用可以充当 正调节剂，促进止血块的生长和稳定以防止再出血，或作为 负调节剂，限制生长和稳定性，从而避免血管闭塞。期间最 最近的资助期间，我们在血小板表面鉴定了肝配蛋白 B1 和信号蛋白 4D，并显示 这些配体与其各自的受体（ephrinBI 的 EphB1 和 EphA4；CD72 和 sema4D 的丛蛋白 B1) 促进血栓生长。我们还确定了 ESAM，一种假定的细胞 CTX家族中的粘附分子，当血小板被激活时易位至连接处，然后充当 负调节因子，因此 ESAM 表达的丧失会促进而不是削弱 血小板质量。该提案中描述的研究分为四个具体目标，重点关注血小板 连接点和依赖于接触的相互作用。目标 #1 将测试我们当前的模型，即 ESAM 是否定的 血小板调节剂：血小板相互作用，并探讨 ESAM 功能丧失对血小板的影响 使用现有的 ESAM 基因敲除小鼠品系激活血小板。目标#2 将重点关注以下方面的分子基础： ESAM 的贡献始于我们最近鉴定的两种支架蛋白 NHERF-1 和 CAL， 结合 ESAM 细胞质结构域。目标 #3 是对其他三个 CTX 系列的比较分析 血小板中表达的成员（JAM-A、JAM-C 和 CD226）以确定它们的作用是否与 埃萨姆。 JAM-A 敲除小鼠获得的初步结果表明情况可能如此。目标#4 是 致力于血小板中其他连接分子的表征，从肝配蛋白 A1 开始 血小板并继续公正地寻找新蛋白质。