Platelets function by secreting components necessary for primary clot formation. This report describes an in vitro assay that measures α-granule secretion. Using permeabilized platelets, it is possible to recreate Ca2+-stimulated release of platelet factor 4 (PF4) that is ATP- and temperature-dependent. Though other divalent cations can replace Ca2+ (i.e., Sr2+, Mn2+, Zn2+), there is no effect of Ba2+. Analysis by electron microscopy indicates that the in vitro assay also mimics the cytoskeletal rearrangements and granule centralization that occurs upon platelet activation in vivo. Antibody inhibition studies show that PF4 release requires the general membrane fusion protein N-ethylmaleimide-sensitive factor (NSF) and well as the target membrane SNAP receptors (t-SNAREs), syntaxin 2, 4, and SNAP-23. As shown by electron microscopy, the anti-t-SNARE antibodies block granule to target membrane fusion. This finding is unique in that it is the first report of a role for two syntaxins in the same exocytosis event. (C) 2000 Academic Press.
|Number of pages||6|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Jan 27 2000|
Bibliographical noteFunding Information:
The authors thank the staff of the Central Kentucky Blood Center for their assistance and the members of the Whiteheart lab for their helpful discussions. We especially thank Dr. Bruce Maley, Mary Gail Engle, and Richard Watson at the College of Medicine Imaging Facility, University of Kentucky, for their assistance with the electron microscopy studies. This work was supported by Grant HL56652 from the Heart, Lung, and Blood Institute of the National Institutes of Health.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology