Biology of Platelet Factor 4

血小板包含一个独特的趋化因子血小板因子4 (PF4),这是在大量网站发布的血小板激活。而许多潜在PF4的角色在心血管系统提出基于体外数据,其体内生物作用(s)尚不清楚。在本应用中，我们将定义PF4在血小板生物学中的作用，扩展我们关于PF4与低密度脂蛋白（LDL）及其受体LDL- r和相关受体LRP相互作用的初步体外数据。我们还将延长这些观察体内。具体目的包括：1 .表征PF4在体外与LDL-R和LRP的相互作用。这些研究将描述PF4与LDL-受体(R)结合的相互作用，使用定义的嵌合体和突变体确定PF4和LDL-R内的相关结构域，并探索细胞蛋白聚糖对PF4的寡聚化会阻碍LDL/LDL-R复合物的内吞作用的假设。我们还将研究PF4与LRP相互作用的特异性，并进一步表征其影响尿激酶进入细胞摄取的能力。数字2:PF4对动脉粥样硬化发展的影响聚焦于转基因小鼠方法。我们建立了PF4缺失小鼠（mPF4）和过表达人PF4的小鼠（hPF4+）。这些动物将被研究PF4水平对LDL代谢的影响。这些动物还将被杂交到几个定义明确的动脉粥样硬化模型上，以测试PF4对LDL代谢和动脉粥样硬化发展的影响的具体问题。编号3:PF4对心血管生物学的影响聚焦于转基因小鼠方法。强劲的体外数据由我们组和其他人建议PF4的角色发展的血栓形成,血管生成和megakaryopoiesis。然而，PF4在这些过程中的生理作用尚未得到证实。在这个特定目标中，我们计划使用mPF4-/-和hPF4+小鼠开始定义文献中和第一个特定目标中提出的体外研究的生物学相关性。穿越到其他的转基因动物模型,将提高我们对分子机制的理解(s)的PF4有助于这些生物过程也提出了。我们相信，通过该应用获得的新信息将具有临床相关性。PF4的生物学研究将为一些心血管相关过程的调控提供新的见解，并可能为心血管疾病的治疗提供新的方法。

Platelets contain a unique chemokine Platelet Factor 4 (PF4), which is released in large amounts at sites of platelet activation. While a number of potential roles of PF4 in the cardiovascular system have been suggested based on in vitro data, its in vivo biological role(s) is unclear. In this application we will define the role of PF4 in platelet biology, extending our preliminary in vitro data of PF4's interaction with low-density lipoprotein (LDL), with its receptor LDL-R and with the related receptor LRP. We will also extend these observations in vivo. Specific aims include: Number 1: Characterize PF4's interactions with LDL-R and LRP in vitro. These studies will characterize the interactions of PF4 with LDL binding to the LDL-receptor (R), identifying the responsible domains within PF4 and LDL-R using defined chimeras and mutants, and exploring the hypothesis that oligomerization of PF4 by cellular proteoglycans frustrates the endocytosis of LDL/LDL-R complexes. We will also examine the specificity of PF4's interactions with LRP and further characterize its ability to influence the uptake of urokinase into cells. Number 2: Effect of PF4 on the development of atherosclerosis focusing on a transgenic mice approach. We have created PF4 null mice (mPF4) and mice overexpressing human PF4 (hPF4+). These animals will be studied to see the effect of PF4 level on LDL metabolism. The animals will also be crossed onto several well-defined atherogenic models that will test specific issues related to PF4's affect on LDL metabolism and the development of atherosclerosis. Number 3: Effect of PF4 on the cardiovascular biology focusing on a transgenic mice approach. Strong in vitro data developed by our group and others have suggested a role of PF4 in the development of thrombosis, angiogenesis and megakaryopoiesis. However, a physiologic role of PF4 in these processes has yet to be demonstrated. In this specific aim, we plan to use the mPF4-/- and hPF4+ mice to begin to define the biological relevance of the in vitro studies in the literature and presented in the 1st specific aim. Crosses onto other transgenic animal models that will enhance our understanding of the molecular mechanism(s) by which PF4 contributes to these biological processes are also proposed. We believe that new information derived by this application will have clinical relevance. The biological studies of PF4 should provide new insights into the regulation of several cardiovascular-related processes, and may offer novel approaches for the treatment of cardiovascular diseases.