A novel mechanism regulating human platelet activation by MMP-2-mediated PAR1 biased signaling

作者：Sebastiano Manuela; Momi Stefania; Falcinelli Emanuela; Bury Loredana; Hoylaerts Marc F; Gresele Paolo^*

来源：Blood, 2017, 129(7): 883-895.

DOI：10.1182/blood-2016-06-724245

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 Gq and G(12/13) pathway activation, triggering p38-MAPK phosphorylation, Ca+2 fluxes, and PI3K activation, but not G(i) signaling; this is insufficient to cause platelet aggregation, but it is enough to predispose platelets to fully respond to G(i)-activating stimuli. Integrin alpha(IIb)beta(3) is 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 alpha(IIb)beta(3) and 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-alpha(II)beta(3)-PAR1 interaction as a potential target for the prevention of arterial thrombosis.

• 出版日期2017-2-16
• 单位Perugia