Dynamin-Related Protein-1 Controls Fusion Pore Dynamics During Platelet Granule Exocytosis

Abstract

Objective Platelet granule exocytosis serves a central role in hemostasis and thrombosis. Recently, single-cell amperometry has shown that platelet membrane fusion during granule exocytosis results in the formation of a fusion pore that subsequently expands to enable the extrusion of granule contents. However, the molecular mechanisms that control platelet fusion pore expansion and collapse are not known. Methods and Results We identified dynamin-related protein 1 (Drp1) in platelets and found that an inhibitor of Drp1, mdivi-1, blocked exocytosis of both platelet dense and α-granules. We used single-cell amperometry to monitor serotonin release from individual dense granules and thereby measured the effect of Drp1 inhibition on fusion pore dynamics. Inhibition of Drp1 increased spike width and decreased pre-spike foot events, indicating that Drp1 influences fusion pore formation and expansion. Platelet-mediated thrombus formation in vivo following laser-induced injury of mouse cremaster arterioles was impaired following infusion of mdivi-1. Conclusions These results demonstrate that inhibition of Drp1 disrupts platelet fusion pore dynamics and indicate that Drp1 can be targeted to control thrombus formation in vivo.

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“…Moreover, pore formation may be a reversible event. Amperometric measurements of membrane capacitance show a “flickering” in capacitance values during the release reaction suggesting that pores are unstable [34–36]. The stability of the α-granule ghost membrane indicates that α-granule are not a major source of the membrane needed for pseudopodia formation during platelet activation and, in fact, platelets begin to form pseudopods before α-granule release.…”