title: A novel mechanism regulating human platelet activation by MMP-2-mediated PAR1 biased signaling.
abstract: Platelets contain and release several matrix metalloproteinases (MMPs). Among these, active MMP-2 enhances platelet aggregation by favoring the activation of phosphatidylinositol 3- kinase (PI3K) and contributes to arterial thrombosis. The platelet surface target of MMP-2 and the mechanism through which it primes platelets to respond to subsequent stimuli are still unknown. We show that active MMP-2 enhances platelet activation induced by weak stimuli by cleaving PAR1 at a noncanonical extracellular site different from the thrombin-cleavage site and thus initiates biased receptor signaling, triggering only some of the signaling pathways normally activated by full PAR1 agonism. The novel PAR1-tethered ligand exposed by MMP-2 stimulates PAR1-dependent Gqand G12/13pathway activation, triggering p38-MAPK phosphorylation, Ca+2fluxes, and PI3K activation, but not Gisignaling; this is insufficient to cause platelet aggregation, but it is enough to predispose platelets to fully respond to Gi-activating stimuli. Integrin αIIbβ3is a necessary cofactor for PAR1 cleavage by MMP-2 by binding the MMP-2 hemopexin domain, thus favoring the interaction of the enzyme with PAR1. Our studies unravel a novel mechanism regulating platelet activation that involves the binding of MMP-2 to integrin αIIbβ3and the subsequent cleavage of PAR1 by active MMP-2 at a noncanonical site, exposing a previously undescribed tethered ligand that triggers biased G-protein agonism and thus predisposes platelets to full activation by other stimuli. These results identify the MMP-2-αIIbβ3-PAR1 interaction as a potential target for the prevention of arterial thrombosis.
authors.affiliation: Division of Internal and Cardiovascular Medicine, Department of Medicine, University of Perugia, Perugia, Italy; and.
authors.forename: Manuela
authors.initials: M
authors.lastname: Sebastiano
authors.affiliation: Division of Internal and Cardiovascular Medicine, Department of Medicine, University of Perugia, Perugia, Italy; and.
authors.forename: Stefania
authors.initials: S
authors.lastname: Momi
authors.affiliation: Division of Internal and Cardiovascular Medicine, Department of Medicine, University of Perugia, Perugia, Italy; and.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Falcinelli
authors.affiliation: Division of Internal and Cardiovascular Medicine, Department of Medicine, University of Perugia, Perugia, Italy; and.
authors.forename: Loredana
authors.initials: L
authors.lastname: Bury
authors.affiliation: Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Marc F
authors.initials: MF
authors.lastname: Hoylaerts
authors.affiliation: Division of Internal and Cardiovascular Medicine, Department of Medicine, University of Perugia, Perugia, Italy; and.
authors.forename: Paolo
authors.identifier: 0000-0001-5365-8445
authors.initials: P
authors.lastname: Gresele
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism*; D016466:CHO Cells; D003412:Cricetulus; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D051379:Mice; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D060066:Protein Interaction Maps; D044463:Receptor, PAR-1 / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D044463:Receptor, PAR-1; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2