BIOLOGY OF HUMAN PLATELET FC(GAMMA) RECEPTORS

人类血小板 FC(GAMMA) 受体的生物学

• 批准号: 6435892
• 负责人: Alan D Schreiber
• 金额: $ 19.72万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6435892
• 关键词: antibody receptor; biological signal transduction; gel mobility shift assay; genetic regulation; genetic regulatory element; genetic transcription; genetically modified animals; hemostasis; immunoglobulin genes; laboratory mouse; megakaryocytes; phosphorylation; platelet activation; polymerase chain reaction; protein structure function; protein tyrosine kinase; receptor binding; receptor expression; thrombocytopenia; tissue /cell culture; transcription factor

We have determined that human platelets and megakaryocytes have receptors for the Pc portion of IgG encoded by the FcgammaRIIA gene. Engagement of the platelet Fcgamma receptor by immune complexes and anti-platelet antibodies leads to accelerated platelet clearance and platelet activation, the release of biologically active products and thrombosis. Therapy to intervene in these pathologic processes will require understanding the regulation of receptor expression level and the mechanism of the transmission of the receptor's activation signals. The goal of this research project is to gain a greater understanding of the biologic role of the platelet Fcgamma receptor in platelet activation. The first specific aim examines the regulation of expression of the platelet Fcgamma receptor. Alterations in the level of platelet surface FcgammaRIIA expression leads to alterations in receptor mediated activation of platelets. We have identified cis-acting sequences and trans-acting factors important for FcgammaRIIA basal transcription and will identify those responsible for the modulation of FcgammaRIIA transcription by cytokines and glucocorticoids using reporter gene assays in megakaryotic cells. Our transgenic mouse model will enable determination of the effect of these regulatory molecule on platelet FcgammaRIIA expression in vivo. The second specific aim examines structure/function relationships in platelet/megakaryocyte Fcgamma receptor signaling. FcgammaRIIA has three cytoplasmic tyrosines in an ITAM-(immunoreceptor tyrosine-based activation motif)-like sequence. We have established that all three cytoplasmic tyrosines and the tyrosine kinase Syk are important in the early events following receptor crosslinking. Syk antisense oligodeoxynucleotides will be used to identify the effect of Syk ablation on protein tyrosine phosphorylation and Ca2+ signaling in megakaryocytic cells. These signal transduction events will be studied in megakaryocytic cells transfected with wild-type and mutant FcgammaRIIA cytoplasmic domain sequences. We will also use platelets from our FcgammaRIIA transgenic mice to study the FcgammaRIIA mediated secretory response. Finally, the third specific aim examines the role of FcgammaRIIA in platelet clearance and activation in vivo. Our hypothesis is that the expression of human FcgammaRIIA leads to more extensive thrombocytopenia triggered by anti-platelet antibodies and by immune complexes and to enhanced intravascular platelet activation. Following challenge with anti-platelet antibody and immune complex, platelet counts and a marker of intravascular platelet activation in our FcgammaRIIA transgenic mice will be compared to wild-type mice and mice expressing FcgammaRIIA only in platelets.

我们已经确定人血小板和巨核细胞具有受体 对于由fcgammariia基因编码的IgG的PC部分。参与 免疫复合物和抗血清的血小板fcgamma受体 抗体导致加速血小板间隙和血小板 激活，生物活性产物和血栓形成的释放。 干预这些病理过程的治疗将需要 了解受体表达水平和 受体激活信号传播的机理。这 该研究项目的目标是对 血小板受体在血小板激活中的生物学作用。这 第一个特定目的检查了血小板表达的调节 Fcgamma受体。血小板表面fcgammariia水平的改变 表达导致受体介导的激活改变 血小板。我们已经确定了顺式作用序列和反式作用 对fcgammariia基础转录重要的因素，并将确定 负责通过 使用报告基因测定法中的细胞因子和糖皮质激素 细胞。我们的转基因小鼠模型将确定效果 这些调节性分子在体内的血小板fcmamariia表达上。 第二个特定目的研究了结构/功能关系 血小板/巨核细胞FCGAMMA受体信号传导。 fcgammariia有三个 ITAM-（免疫受体酪氨酸激活）中的细胞质酪氨酸 图案）类似序列。我们已经确定所有三个细胞质 酪氨酸和酪氨酸激酶SYK在早期事件中很重要 以下受体交联。 SYK反义寡脱氧核苷酸将 用于识别Syk消融对蛋白质酪氨酸的影响 巨核细胞中的磷酸化和Ca2+信号传导。这些信号 转导事件将在转染的巨核细胞中进行研究 具有野生型和突变的fcgammariia细胞质结构域序列。我们 还将使用我们的fcgammariia转基因小鼠的血小板来研究 Fcgammariia介导的分泌反应。最后，第三个特定目标 检查fcgammariia在血小板清除和激活中的作用 体内。我们的假设是人类fcgammariia的表达导致 由抗血小板抗体触发的更广泛的血小板减少症和 通过免疫复合物并增强了血管内血小板激活。 在抗血小板抗体和免疫复合物的挑战之后， 血小板计数和我们的血管内血小板激活标记 将Fcgammariia转基因小鼠与野生型小鼠和小鼠进行比较 仅在血小板中表达fcgammariia。