title: Endobrevin/VAMP-8-dependent dense granule release mediates thrombus formation in vivo.
abstract: Individuals whose platelets lack dense or alpha-granules suffer various degrees of abnormal bleeding, implying that granule cargo contributes to hemostasis. Despite these clinical observations, little is known regarding the effects of impaired platelet granule secretion on thrombus formation in vivo. In platelets, SNARE proteins mediate the membrane fusion events required for granule cargo release. Endobrevin/VAMP-8 is the primary vesicle-SNARE (v-SNARE) responsible for efficient release of dense and alpha-granule contents; thus, VAMP-8(-/-) mice are a useful model to evaluate the importance of platelet granule secretion in thrombus formation. Thrombus formation, after laser-induced vascular injury, in these mice is delayed and decreased, but not absent. In contrast, thrombus formation is almost completely abolished in the mouse model of Hermansky-Pudlak syndrome, ruby-eye, which lacks dense granules. Evaluation of aggregation of VAMP-8(-/-) and ruby-eye platelets indicates that defective ADP release is the primary abnormality leading to impaired aggregation. These results demonstrate the importance of dense granule release even in the earliest phases of thrombus formation and validate the distal platelet secretory machinery as a potential target for antiplatelet therapies.
authors.affiliation: Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: Gwenda J
authors.initials: GJ
authors.lastname: Graham
authors.forename: Qiansheng
authors.initials: Q
authors.lastname: Ren
authors.forename: James R
authors.initials: JR
authors.lastname: Dilks
authors.forename: Price
authors.initials: P
authors.lastname: Blair
authors.forename: Sidney W
authors.initials: SW
authors.lastname: Whiteheart
authors.forename: Robert
authors.initials: R
authors.lastname: Flaumenhaft
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D001160:Arterioles / Q000293:injuries; D001777:Blood Coagulation / Q000502:physiology*; D001778:Blood Coagulation Disorders / Q000097:blood* / Q000209:etiology; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004195:Disease Models, Animal; D022861:Hermanski-Pudlak Syndrome / Q000097:blood; D006801:Humans; D007834:Lasers / Q000009:adverse effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D010974:Platelet Aggregation / Q000502:physiology*; D050683:R-SNARE Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D050600:SNARE Proteins / Q000097:blood
chemical_list: D050683:R-SNARE Proteins; D050600:SNARE Proteins; C491831:Vamp8 protein, mouse; D000244:Adenosine Diphosphate