Biochemical isolation and characterization of the lateral border recycling compartment from human endothelial cells and determination of its regulatory role for transendothelial migration of leukocytes

血小板-内皮-细胞黏附分子-1(PECAM-1)属于免疫球蛋白(Ig)超家族细胞黏附分子。PECAM-1的表达仅限于血管系统的细胞。在融合的内皮细胞中，PECAM-1定位于细胞-细胞边界和血管内皮细胞面向管腔的质膜。在体内和体外，PECAM-1在中性粒细胞、单核细胞和自然杀伤细胞的迁移中起着重要的作用。用抗PECAM-1抗体或可溶性PECAM-1-Fc嵌合体阻断PECAM-1选择性地抑制70%-90%的跨内皮细胞迁移。在静息内皮细胞中，PECAM-1在细胞表面和一个新的内部承载PECAM-1的隔室之间循环。PECAM-1从这个隔室向内皮细胞边界进行结构性循环。在发育期，回收的PECAM直接针对内皮细胞边界接触迁移的单核细胞的区域，而不是沿着横向细胞边界循环。本项目的主要目标是对这个横向隔室进行彻底的生化分析。这应该会进一步深入了解这一间隔室在跨内皮细胞迁移过程中的作用。

Platelet-endothelial-cell adhesion molecule 1 (PECAM-1) belongs to the immunoglobulin (Ig) superfamily of cell adhesion molecules. The expression of PECAM-1 is restricted to cells of the vascular system. In confluent endothelial cells PECAM-1 localizes to cell-cell borders and to the lumen-facing plasmamembrane of the endothelium in blood vessels. PECAM-1 plays an important role in the transmigration of neutrophils, monocytes and natural killer cells, both in vivo and in vitro. Blocking PECAM-1 with anti-PECAM-1 antibodies or soluble PECAM-1-Fc chimera selectively inhibits transendothelial migration by 70-90%. In resting endothelial cells, PECAM-1 cycles between the cell surface and a novel internal PECAM-1-bearing compartment. PECAM-1 constitutively recycles from this compartment to the endothelial cell border. During diapedesis the recycling PECAM is directly targeted to the zone of the endothelial cell border that contacts the transmigrating monocytes, rather then recycling evently along the lateral cell borders.The major goal of this project is to perform a thorough biochemical analysis of this lateral compartment. This should give further insights into the role of this compartment in the process of transendothelial migration.