title: Physical proximity and functional interplay of PECAM-1 with the Fc receptor Fc gamma RIIa on the platelet plasma membrane.
abstract: 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.
authors.affiliation: Austin Research Institute, Austin Hospital, Studley Road, Heidelberg, Victoria, Australia 3084.
authors.forename: Le M
authors.initials: le M
authors.lastname: Thai
authors.forename: Leonie K
authors.initials: LK
authors.lastname: Ashman
authors.forename: Stacey N
authors.initials: SN
authors.lastname: Harbour
authors.forename: P Mark
authors.initials: PM
authors.lastname: Hogarth
authors.forename: Denise E
authors.initials: DE
authors.lastname: Jackson
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism* / Q000502:physiology; D001792:Blood Platelets / Q000378:metabolism* / Q000502:physiology; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D010446:Peptide Fragments / Q000276:immunology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010973:Platelet Adhesiveness / Q000187:drug effects; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding; D017452:Receptors, IgG / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C080568:Fc gamma receptor IIA; D008565:Membrane Proteins; D010446:Peptide Fragments; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D017452:Receptors, IgG; D006493:Heparin; D019869:Phosphatidylinositol 3-Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma