title: Stimulation of P2 (P2X7) receptors in human dendritic cells induces the release of tissue factor-bearing microparticles.
abstract: Receptors for extracellular nucleotides are the focus of increasing attention for their ability to cause release of plasma membrane vesicles (microparticles, MPs). Here, we show that monocyte-derived human dendritic cells (DCs) stimulated with a P2X7 receptor (P2X7R) agonist undergo a large release of MPs endowed with procoagulant activity. Functional and Western blot studies revealed that MPs contain the membrane-bound form of tissue factor (TF), a glycoprotein acting as essential cofactor of activated factor VII and triggering blood coagulation. Quiescent DCs express the membrane-bound (full length), as well as truncated alternatively spliced TF forms. DC reactivity to anti-TF Abs disappeared almost completely on stimulation with ATP or benzoyl ATP (BzATP), as shown by immunoblot and confocal microscopy analysis. Concurrently, TF reactivity and activity appeared in the vesicular fraction, indicating that MPs are important carriers for the dissemination of full-length TF form. Activity of MP-bound TF, comparable to that of relipidated recombinant TF, was dose dependently inhibited by the addition of a specific anti-human TF antibody. We infer that a large fraction of this protein, and its procoagulant potential, are "deliverable" after physiological or pathological stimuli. These findings might have implications for triggering and propagating coagulation in healthy and atherosclerotic vessels.
authors.affiliation: Department of Biochemistry, University of Ferrara, Ferrara, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Baroni
authors.forename: Cinzia
authors.initials: C
authors.lastname: Pizzirani
authors.forename: Mirko
authors.initials: M
authors.lastname: Pinotti
authors.forename: Davide
authors.initials: D
authors.lastname: Ferrari
authors.forename: Elena
authors.initials: E
authors.lastname: Adinolfi
authors.forename: Sara
authors.initials: S
authors.lastname: Calzavarini
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Caruso
authors.forename: Francesco
authors.initials: F
authors.lastname: Bernardi
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Virgilio
mesh_terms: D050197:Atherosclerosis; D001777:Blood Coagulation; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure*; D003713:Dendritic Cells / Q000648:ultrastructure*; D006801:Humans; D010316:Particle Size; D018048:Receptors, Purinergic P2 / Q000378:metabolism* / Q000502:physiology; D058486:Receptors, Purinergic P2X7; D013925:Thromboplastin / Q000032:analysis* / Q000502:physiology
chemical_list: C546468:P2RX7 protein, human; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D013925:Thromboplastin