Thai Le M, Ashman Leonie K, Harbour Stacey N, Hogarth P Mark, Jackson Denise E
Austin Research Institute, Austin Hospital, Studley Road, Heidelberg, Victoria, Australia 3084.
Blood. 2003 Nov 15;102(10):3637-45. doi: 10.1182/blood-2003-02-0496. Epub 2003 Jul 31.
We and others have recently defined that Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1/CD31) functions as a negative regulator of platelet-collagen interactions involving the glycoprotein VI/Fc receptor gamma chain (GPVI/FcR-gamma chain) signaling pathway.1,2 In this study, we hypothesized that PECAM-1 may be physically and functionally associated with Fc gamma RIIa on the platelet membrane. The functional relationship between PECAM-1 and Fc gamma RIIa was assessed by determining the effect of anti-PECAM-1 monoclonal antibody Fab fragments on Fc gamma RIIa-mediated platelet aggregation and heparin-induced thrombocytopenia (HITS)-mediated platelet aggregation. Preincubation of washed platelets with monoclonal antibody fragments of 2BD4 directed against PECAM-1 and IV.3 directed against Fc gamma RIIa completely blocked Fc gamma RIIa-mediated platelet aggregation and HITS-mediated platelet aggregation, whereas anti-CD151 antibody had no blocking effect. Coengagement of Fc gamma RIIa and PECAM-1 resulted in negative regulation of Fc gamma RIIa-mediated phospholipase C gamma 2 activation, calcium mobilization, and phosphoinositide 3-kinase-dependent signaling pathways. In addition, the physical proximity of Fc gamma RIIa and PECAM-1 was confirmed by using fluorescence resonance energy transfer and coimmunoprecipitation studies. These results indicate that PECAM-1 and Fc gamma RIIa are colocalized on the platelet membrane and PECAM-1 down-regulates Fc gamma RIIa-mediated platelet responses.
我们和其他研究人员最近发现，血小板内皮细胞黏附分子-1（PECAM-1/CD31）作为血小板与胶原蛋白相互作用的负调节因子，参与糖蛋白VI/Fc受体γ链（GPVI/FcR-γ链）信号通路。1,2 在本研究中，我们假设PECAM-1可能在血小板膜上与FcγRIIa存在物理和功能上的关联。通过测定抗PECAM-1单克隆抗体Fab片段对FcγRIIa介导的血小板聚集和肝素诱导的血小板减少症（HITS）介导的血小板聚集的影响，评估了PECAM-1与FcγRIIa之间的功能关系。用针对PECAM-1的2BD4单克隆抗体片段和针对FcγRIIa的IV.3单克隆抗体片段预孵育洗涤后的血小板，完全阻断了FcγRIIa介导的血小板聚集和HITS介导的血小板聚集，而抗CD151抗体则没有阻断作用。FcγRIIa和PECAM-1的共同参与导致FcγRIIa介导的磷脂酶Cγ2激活、钙动员和磷酸肌醇3激酶依赖性信号通路的负调节。此外，通过荧光共振能量转移和共免疫沉淀研究证实了FcγRIIa和PECAM-1在物理上的接近性。这些结果表明，PECAM-1和FcγRIIa共定位于血小板膜上，且PECAM-1下调FcγRIIa介导的血小板反应。
