Granule stores from cellubrevin/VAMP-3 null mouse platelets exhibit normal stimulus-induced release.
It is widely accepted that the platelet release reaction is mediated by heterotrimeric complexes of integral membrane proteins known as SNAREs (SNAP receptors). In an effort to define the precise molecular machinery required for platelet exocytosis, we have analyzed platelets from cellubrevin/VAMP-3 knockout mice. Cellubrevin/VAMP-3 has been proposed to be a critical v-SNARE for human platelet exocytosis; however, data reported here suggest that it is not required for platelet function. Upon stimulation with increasing concentrations of thrombin, collagen, or with thrombin for increasing time there were no differences in secretion of [3H]-5HT (dense core granules), platelet factor IV (alpha granules), or hexosaminidase (lysosomes) between null and wild-type platelets. There were no gross differences in bleeding times nor in agonist-induced aggregation measured in platelet-rich plasma or with washed platelets. Western blotting of wild-type, heterozygous, and null platelets confirmed the lack of cellubrevin/VAMP-3 in nulls and showed that most elements of the secretion machinery are expressed at similar levels. While the secretory machinery in mice was similar to humans, mice did express apparently higher levels of synaptobrevin/VAMP-2. These data show that the v-SNARE, cellubrevin/VAMP-3 is not a requirement for the platelet release reaction in mice.
Schraw
Todd D
TD
Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, 800 Rose St, Lexington, KY 40536, USA. whitehe@pop.uky.edu
Rutledge
Tara W
TW
Crawford
Garland L
GL
Bernstein
Audrey M
AM
Kalen
Amanda L
AL
Pessin
Jeffery E
JE
Whiteheart
Sidney W
SW
D000818:Animals; D001760:Bleeding Time; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D005838:Genotype; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010974:Platelet Aggregation; D011480:Protease Inhibitors / Q000494:pharmacology; D050683:R-SNARE Proteins; D051040:Vesicle-Associated Membrane Protein 3
D008565:Membrane Proteins; D011480:Protease Inhibitors; D050683:R-SNARE Proteins; D051040:Vesicle-Associated Membrane Protein 3