TY - JOUR
T1 - SNARE-dependent membrane fusion initiates α-granule matrix decondensation in mouse platelets
AU - Pokrovskaya, Irina D.
AU - Joshi, Smita
AU - Tobin, Michael
AU - Desai, Rohan
AU - Aronova, Maria A.
AU - Kamykowski, Jeffrey A.
AU - Zhang, Guofeng
AU - Whiteheart, Sidney W.
AU - Leapman, Richard D.
AU - Storrie, Brian
N1 - Publisher Copyright:
© American Society of Hematology. All rights reserved.
PY - 2018/11/13
Y1 - 2018/11/13
N2 - Platelet α-granule cargo release is fundamental to both hemostasis and thrombosis. Granule matrix hydration is a key regulated step in this process, yet its mechanism is poorly understood. In endothelial cells, there is evidence for 2modes of cargo release: A jack-in-The-box mechanism of hydration-dependent protein phase transitions and an actin-driven granule constriction/extrusion mechanism. The third alternative considered is a prefusion, channel-mediated granule swelling, analogous to the membrane "ballooning" seen in procoagulant platelets. Using thrombin-stimulated platelets from a set of secretion-deficient, soluble N-ethylmaleimide factor attachment protein receptor (SNARE) mutant mice and various ultrastructural approaches, we tested predictions of these mechanisms to distinguish which best explains the α-granule release process.We found that the granule decondensation/ hydration required for cargo expulsion was (1) blocked in fusion-protein-deficient platelets; (2) characterized by a fusion-dependent transition in granule size in contrast to a preswollen intermediate; (3) determined spatially with α-granules located close to the plasma membrane (PM) decondensing more readily; (4) propagated from the site of granule fusion; and (5) traced, in 3-dimensional space, to individual granule fusion events at the PM or less commonly at the canalicular system. In sum, the properties of α-granule decondensation/ matrix hydration strongly indicate that α-granule cargo expulsion is likely by a jack-in-The-box mechanism rather than by gradual channel-regulated water influx or by a granule-constriction mechanism. These experiments, in providing a structural and mechanistic basis for cargo expulsion, should be informative in understanding the α-granule release reaction in the context of hemostasis and thrombosis.
AB - Platelet α-granule cargo release is fundamental to both hemostasis and thrombosis. Granule matrix hydration is a key regulated step in this process, yet its mechanism is poorly understood. In endothelial cells, there is evidence for 2modes of cargo release: A jack-in-The-box mechanism of hydration-dependent protein phase transitions and an actin-driven granule constriction/extrusion mechanism. The third alternative considered is a prefusion, channel-mediated granule swelling, analogous to the membrane "ballooning" seen in procoagulant platelets. Using thrombin-stimulated platelets from a set of secretion-deficient, soluble N-ethylmaleimide factor attachment protein receptor (SNARE) mutant mice and various ultrastructural approaches, we tested predictions of these mechanisms to distinguish which best explains the α-granule release process.We found that the granule decondensation/ hydration required for cargo expulsion was (1) blocked in fusion-protein-deficient platelets; (2) characterized by a fusion-dependent transition in granule size in contrast to a preswollen intermediate; (3) determined spatially with α-granules located close to the plasma membrane (PM) decondensing more readily; (4) propagated from the site of granule fusion; and (5) traced, in 3-dimensional space, to individual granule fusion events at the PM or less commonly at the canalicular system. In sum, the properties of α-granule decondensation/ matrix hydration strongly indicate that α-granule cargo expulsion is likely by a jack-in-The-box mechanism rather than by gradual channel-regulated water influx or by a granule-constriction mechanism. These experiments, in providing a structural and mechanistic basis for cargo expulsion, should be informative in understanding the α-granule release reaction in the context of hemostasis and thrombosis.
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U2 - 10.1182/bloodadvances.2018019158
DO - 10.1182/bloodadvances.2018019158
M3 - Article
C2 - 30401752
AN - SCOPUS:85072747371
SN - 2473-9529
VL - 2
SP - 2947
EP - 2958
JO - Blood advances
JF - Blood advances
IS - 21
ER -