Respective contributions of single and compound granule fusion to secretion by activated platelets

Anita Eckly, Jean Yves Rinckel, Fabienne Proamer, Neslihan Ulas, Smita Joshi, Sidney W. Whiteheart, Christian Gachet

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

Although granule secretion is pivotal in many platelet responses, the fusion routes of α and δ granule release remain uncertain. We used a 3D reconstruction approach based on electron microscopy to visualize the spatial organization of granules in unstimulated and activated platelets. Two modes of exocytosis were identified: a single mode that leads to release of the contents of individual granules and a compound mode that leads to the formation of granule-to-granule fusion, resulting in the formation of large multigranular compartments. Both modes occur during the course of platelet secretion. Single fusion events are more visible at lower levels of stimulation and early time points, whereas large multigranular compartments are present at higher levels of agonist and at later time points. Although α granules released their contents through both modes of exocytosis, δ granules underwent only single exocytosis. To define the underlying molecular mechanisms, we examined platelets from vesicle-associated membrane protein 8 (VAMP8) null mice. After weak stimulation, compound exocytosis was abolished and single exocytosis decreased in VAMP8 null platelets. Higher concentrations of thrombin bypassed the VAMP8 requirement, indicating that this isoform is a key but not a required factor for single and/or compound exocytosis. Concerning the biological relevance of our findings, compound exocytosis was observed in thrombi formed after severe laser injury of the vessel wall with thrombin generation. After superficial injury without thrombin generation, no multigranular compartments were detected. Our studies suggest that platelets use both modes of membrane fusion to control the extent of agonist-induced exocytosis.

Original languageEnglish
Pages (from-to)2538-2549
Number of pages12
JournalBlood
Volume128
Issue number21
DOIs
StatePublished - Nov 24 2016

Bibliographical note

Funding Information:
The authors thank François Lanza, Pierre Mangin, and Catherine Léon for critical reading of the manuscript and C. Ravanat and N. Receveur for their excellent expert technical assistance. The authors also thank Juliette N. Mulvihill for reviewing the English in the manuscript. This work was supported by the Association de Recherche et Développement en Médecine et Santé Publique and the European Union through the European Regional Development Fund.

Publisher Copyright:
© 2016 by The American Society of Hematology.

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

Fingerprint

Dive into the research topics of 'Respective contributions of single and compound granule fusion to secretion by activated platelets'. Together they form a unique fingerprint.

Cite this