Molecular Biology of the alpha IIb/betaPlatelet Receptor

alphIIb/ β 3整合素受体仅在巨核细胞和血小板表面高度表达。该受体通过纤维蛋白原和其他配体在血小板聚集中起关键作用。拟建的研究将研究巨核生成过程中alphaIIb/beta3的调控表达以及alphaIIb/beta3受体的功能生物学。这些研究涉及三个具体目的：1 .确定调节alphaalib表达的近端启动子元件，alphaIIb/beta3的限制性组织表达依赖于alphaIlb链，因为beta3在许多组织中表达。我们发现，对alphaIIb表达至关重要的是造血转录因子复合物GATA-1、FOG、1和Fti-1与其近端启动子的结合。事实上，许多其他巨核细胞特异性基因的调控表达可能与这种复合体的结合有关。我们将描述这个复合体的dna结合位点，以及这个复合体内外与其他核因子相互作用的位点。还将研究与转录因子bKLF结合的alphaIIb近端启动子中的沉默元件。2。表征alphaIIb基因的远端调控区域，我们分析了alphaIIb基因位点周围的bb0 200 kb，并定义了两个系统发育上保守的区域，一个上游区域对拷贝数依赖的表达很重要，一个下游区域提高了10/3倍的表达。我们计划在体外和转基因小鼠中检查这些区域，以了解这些区域分别作为绝缘体和增强子的行为。3。alphaIIb/beta3受体的功能分析。我们已经促成了对alphaIIb的n端区域对配体结合很重要的理解。新的研究表明，该区域也可能决定了RGD寡肽对阻断纤维蛋白原结合的敏感性的alphaIIb/beta3物种差异。我们还将研究α iib与β a3异源二聚化的物种差异。综上所述，提出的alphaIIb基因调控研究将为巨核形成过程中如何调控alphaIIb和其他巨核细胞特异性基因提供新的见解。对alphaib / β a3受体的功能研究将进一步深入了解alphaIIb/ β a3如何结合其配体，以及alphaIIb和β a3链如何异二聚化。

The alphIIb/beta3 integrin receptor is highly expressed only on the surface of megakaryocytes and platelets. This receptor has a critical role in platelet aggregation through fibrinogen and other ligands. The proposed studies will examine both the regulated expression of alphaIIb/beta3 during megakaryopoiesis and the functional biology of the alphaIIb/beta3 receptor. These studies involve three specific aims: I. Define the proximal promoter elements regulating alphalIb expression, alphaIIb/beta3's restricted tissue expression is dependent on the alphaIlb chain, since beta3 is expressed by many tissues. We have found that critical to alphaIIb expression is the binding of a complex of hematopoietic transcription factors, GATA-1, FOG,1 and Fti-1, to its proximal promoter. Indeed, the regulated expression of many other megakaryocyte-specific genes may involve binding of this same complex. We will characterize this complex's DNA-binding site, and the sites of interactions within and outside of this complex with other nuclear factors. A silencer element in the alphaIIb proximal promoter that binds the transcription factor bKLF will also be studied. II. Characterize distal regulatory regions of the alphaIIb gene, We have analyzed >200 kb around the alphaIIb gene locus and have defined two phylogenetically-conserved regions, an upstream domain important for copy-number dependent expression and a downstream domain that enhances expression 10/3-fold. We plan to examine these regions both in vitro and in transgenic mice to understand how these regions behave as insulator and enhancer, respectively. III. Functional analysis of the alphaIIb/beta3 receptor. We have contributed to the understanding that an N-terminal region of alphaIIb is important for ligand-binding. New studies show that this region may also define alphaIIb/beta3 species differences in RGD oligopeptide sensitivity for blocking fibrinogen binding. We will also examine species differences in the heterodimerization of alphaIIb with beta3. In summary, the proposed alphaIIb gene regulation studies will provide new insights into how the alphaIIb and other megakaryocyte-specific genes are regulated during megakaryopoiesis. The functional studies on the alphaIlb/beta3 receptor will provide additional insights into how alphaIIb/beta3 bind its ligands, and how the alphaIIb and beta3 chains heterodimerize.