Regulation of plasminogen-dependent cell functions by the novel receptor, Plg-RKT

描述（由申请人提供）：细胞表面的纤溶酶原定位是细胞表面纤溶酶蛋白水解活性正向调节的关键控制点，促进需要细胞迁移的生理和病理过程。我们实验室的长期目标是了解纤溶酶原受体调节病理和生理过程的机制。这一建议是基于我们发现的一种新的蛋白，纤溶酶原受体，Plg-RKT，具有独特的结构：Plg-RKT是一种完整的膜蛋白，在细胞表面暴露c端赖氨酸，以结合纤溶酶原的方向。Plg-RKT作为一种发育调节的纤溶酶原受体，促进纤溶酶原在单核细胞上的激活，并通过细胞外基质调节单核细胞的侵袭。Plg-RKT是体内炎症反应中纤溶酶原依赖性巨噬细胞募集的必要条件。在其他新的研究结果中，Plg-RKT与巨噬细胞合成的主要纤溶酶原激活剂尿激酶纤溶酶原激活剂受体（uPAR）高度共定位，并与uPAR物理相关。本应用的目的是阐明Plg-RKT在炎症反应中调节纤溶酶原依赖性巨噬细胞募集的分子机制。要解决的中心假设是，Plg-RKT通过促进纤溶酶原激活、细胞外基质侵袭和趋化来调节依赖纤溶酶原的巨噬细胞募集。为了验证我们的假设，我们的具体目标是：1)验证Plg-RKT调节特定的uPAR依赖功能的假设，以及uPAR调节纤溶酶原激活和细胞迁移中特定的Plg-RKT依赖功能的假设；2)确定Plg-RKT与uPAR物理关联的分子决定因素；3)探讨Plg-RKT在体内调控纤溶酶原功能的机制。研究将在基于细胞的分析和体内进行，使用新的功能阻断抗Plg-RKT抗体，肽模拟物和新的Plg-RKT敲除小鼠模型。我们期望完成我们的特定目标将为理解炎症调节机制以及依赖于细胞迁移的其他生理和病理过程的调节提供基本见解。

DESCRIPTION (provided by applicant): Localization of plasminogen on cell surfaces is a crucial control point for positive regulation of cell surface plasmin proteolytic activity that facilitates both physiological and pathological processes requiring cell migration. The long-term goal of our laboratory is to understand mechanisms by which plasminogen receptors regulate pathological and physiological processes. This proposal is based on our discovery of a new protein, the plasminogen receptor, Plg-RKT that has a unique structure: Plg-RKT is an integral membrane protein that exposes a C-terminal lysine on the cell surface, in an orientation to bind plasminogen. Plg-RKT functions as a developmentally regulated plasminogen receptor that promotes plasminogen activation on monocytes and regulates invasion of monocytes through extracellular matrices. Plg-RKT is necessary for optimal plasminogen- dependent macrophage recruitment in the inflammatory response in vivo. In other novel results, Plg-RKT is highly co-localized with the receptor for the major plasminogen activator synthesized by macrophages, the urokinase plasminogen activator receptor (uPAR) and physically associates with uPAR. The objective of this application is to elucidate the molecular mechanisms by which Plg-RKT regulates plasminogen-dependent macrophage recruitment in the inflammatory response. The central hypothesis to be addressed is that Plg-RKT regulates plasminogen-dependent macrophage recruitment by promoting plasminogen activation, extracellular matrix invasion and chemotaxis. To address our hypothesis, our specific aims are: 1) to test the hypothesis that Plg-RKT regulates specific uPAR-dependent functions and that uPAR regulates specific Plg-RKT-dependent functions in plasminogen activation and cell migration; 2) to identify molecular determinants of the physical association of Plg-RKT with uPAR; 3) To identify mechanisms by which Plg-RKT regulates functions of plasminogen in vivo. Studies will be performed in cell based assays and in vivo using novel function blocking anti- Plg-RKT antibodies, peptide mimetics and a new Plg-RKT knockout mouse model. We expect that accomplishment of our specific aims will provide fundamental insights that should apply to understanding mechanisms of regulation of inflammation as well as regulation of other physiological and pathological processes dependent on cell migration.