Published online before print February 15, 2007, doi: 10.1161/ATVBAHA.106.139287
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© 2007 American Heart Association, Inc.
Thrombosis |
Platelets Possess and Require an Active Protein Palmitoylation Pathway for Agonist-Mediated Activation and In Vivo Thrombus Formation
From the Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass. Present address for D.S.S.: Portola Pharmaceuticals Inc, 270 East Grand Ave., South San Francisco, Calif.
Correspondence to Robert Flaumenhaft, MD, PhD, Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02115. E-mail rflaumen{at}bidmc.harvard.edu
Objective— Several platelet proteins are palmitoylated, but whether protein palmitoylation functions in platelet activation is unknown. We sought to determine the role of platelet protein palmitoylation in platelet activation and thrombus formation.
Methods and Results— Platelet proteins were depalmitoylated by infusing acyl-protein thioesterase 1 into permeabilized platelets. In intact platelets, platelet protein palmitoylation was blocked using the protein palmitoylation inhibitor cerulein. The effects of inhibiting platelet protein palmitoylation on platelet function and on thrombus formation in vivo were evaluated. When infused into permeabilized platelets, acyl-protein thioesterase 1 reduced total platelet protein palmitoylation and inhibited protease-activated receptor-1–mediated 
-granule secretion with an IC50 of 175 nmol/L and maximal inhibition of 
90%. Gq and SNAP-23, membrane-associated proteins that are constitutively palmitoylated, translocated to the cytosol when permeabilized platelets were exposed to recombinant acyl-protein thioesterase 1. The protein palmitoylation inhibitor cerulein also inhibited platelet granule secretion and aggregation. Studies using intravital microscopy showed that incubation with cerulein decreased the rate of platelet accumulation into thrombi formed after laser-induced injury of mouse arterioles and inhibited maximal platelet accumulation by >60%.
Conclusion— These studies show that platelets possess a protein palmitoylation machinery that is required for both platelet activation and platelet accumulation into thrombi. These studies show that inhibition of platelet protein palmitoylation blocks platelet aggregation and granule secretion. In a murine model of thrombus formation, inhibition of protein palmitoylation markedly inhibits platelet accumulation into thrombi at sites of vascular injury.
Several platelet proteins are palmitoylated, but whether protein palmitoylation functions in platelet activation is unknown. We sought to determine the role of platelet protein palmitoylation in platelet activation and thrombus formation. Our studies show that platelets possess a protein palmitoylation machinery that is required for both platelet activation and platelet accumulation into thrombi. These studies show that inhibition of platelet protein palmitoylation blocks platelet aggregation and granule secretion. In a murine model of thrombus formation, inhibition of protein palmitoylation markedly inhibits platelet accumulation into thrombi at sites of vascular injury.
Key Words: granule secretion • platelet • protein palmitoylation • signal transduction • thrombus formation
Related Article:
Arterioscler. Thromb. Vasc. Biol. 2007 27: 1496-1499.
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