Proteins of the exocytotic core complex mediate platelet alpha-granule secretion. Roles of vesicle-associated membrane protein, SNAP-23, and syntaxin 4.
To understand the molecular basis of granule release from platelets, we examined the role of vesicle-associated membrane protein, SNAP-23, and syntaxin 4 in alpha-granule secretion. A vesicle-associated membrane protein, SNAP-23, and syntaxin 4 were detected in platelet lysate. These proteins form a SDS-resistant complex that disassembles upon platelet activation. To determine whether these proteins are involved in alpha-granule secretion, we developed a streptolysin O-permeabilized platelet model of alpha-granule secretion. Streptolysin O-permeabilized platelets released alpha-granules, as measured by surface expression of P-selectin, in response to Ca2+ up to 120 min after permeabilization. Incubation of streptolysin O-permeabilized platelets with an antibody directed against vesicle-associated membrane protein completely inhibited Ca2+-induced alpha-granule release. Tetanus toxin cleaved platelet vesicle-associated membrane protein and inhibited Ca2+-induced alpha-granule secretion from streptolysin O-permeabilized platelets. An antibody to syntaxin 4 also inhibited Ca2+-induced alpha-granule release by approximately 75% in this system. These results show that vesicle-associated membrane protein, SNAP-23, and syntaxin 4 form a heterotrimeric complex in platelets that disassembles with activation and demonstrate that alpha-granule release is dependent on vesicle SNAP receptor-target SNAP receptor (vSNARE-tSNARE) interactions.
Flaumenhaft
R
R
Center for Hemostasis and Thrombosis Research, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. rflaumen@bidmc.harvard.edu
Croce
K
K
Chen
E
E
Furie
B
B
Furie
B C
BC
D000906:Antibodies / Q000276:immunology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism*; D005089:Exocytosis; D006801:Humans; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D013744:Tetanus Toxin / Q000494:pharmacology
D000906:Antibodies; D002352:Carrier Proteins; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; C100493:SNAP23 protein, human; D013744:Tetanus Toxin; D002118:Calcium