Vesicle-associated membrane protein 3 (VAMP-3) and VAMP-8 are present in human platelets and are required for granule secretion.
Secretion of platelet granules is necessary for normal hemostasis. Platelet secretion requires soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) complex formation between different members of the syntaxin, SNAP-25, and vesicle-associated membrane protein (VAMP) gene families. Using microcapillary reverse-phase high-performance liquid chromatography-nano-electrospray tandem mass spectrometry, we identified VAMP-3 and VAMP-8 as VAMP isoforms coimmunoprecipitated from platelets with syntaxin 4. Immunoblotting experiments confirmed the presence of VAMP-3 and VAMP-8 but not VAMP-1 or VAMP-2 in platelets. To examine the effect of VAMP proteins on platelet secretion, soluble recombinant (r) VAMP-2, rVAMP-3, and rVAMP-8 were incubated with streptolysin O-permeabilized platelets. Secretion of alpha granules (monitored by flow cytometric measurement of P-selectin) was blocked, and dense-granule secretion (assessed by release of carbon 14-serotonin) was almost completely inhibited by rVAMP-3, whereas rVAMP-8 inhibited secretion of dense granules but not alpha granules. In contrast, rVAMP-2, which formed SNARE complexes in vitro, had no effect on platelet exocytosis. We conclude that VAMP-3 and VAMP-8 form SNARE complexes with platelet syntaxin 4 and are required for platelet granule secretion.
Polgár
János
J
Cardiovascular Biology Laboratory, Harvard School of Public Health, Boston, MA 02115, USA.
Chung
Sul-Hee
SH
Reed
Guy L
GL
D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002463:Cell Membrane Permeability; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D011233:Precipitin Tests; D011485:Protein Binding; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D051040:Vesicle-Associated Membrane Protein 3; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; C112938:VAMP8 protein, human; D051040:Vesicle-Associated Membrane Protein 3; D033921:Vesicular Transport Proteins