Granule-mediated release of sphingosine-1-phosphate by activated platelets

Deepa Jonnalagadda, Manjula Sunkara, Andrew J. Morris, Sidney W. Whiteheart

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Sphingosine-1-phosphate (S1P) is an intracellularly generated bioactive lipid essential for development, vascular integrity, and immunity. These functions are mediated by S1P-selective cell surface G-protein coupled receptors. S1P signaling therefore requires extracellular release of this lipid. Several cell types release S1P and evidence for both plasma membrane transporter-mediated and vesicle-dependent secretion has been presented. Platelets are an important source of S1P and can release it in response to agonists generated at sites of vascular injury. S1P release from agonist-stimulated platelets was measured in the presence of a carrier molecule (albumin) using HPLC-MS/MS. The kinetics and agonist-dependence of S1P release were similar to that of other granule cargo e.g. platelet factor IV (PF4). Agonist-stimulated S1P release was defective in platelets from Unc13dJinx (Munc13-4 null) mice demonstrating a critical role for regulated membrane fusion in this process. Consistent with this observation, platelets efficiently converted fluorescent NBD-sphingosine to its phosphorylated derivative which accumulated in granules. Fractionation of platelet organelles revealed the presence of S1P in both the plasma membrane and in α-granules. Resting platelets contained a second pool of constitutively releasable S1P that was more rapidly labeled by exogenously added sphingosine. Our studies indicate that platelets contain two pools of S1P that are released extracellularly: a readily-exchangeable, metabolically active pool of S1P, perhaps in the plasma membrane, and a granular pool that requires platelet activation and regulated exocytosis for release.

Original languageEnglish
Pages (from-to)1581-1589
Number of pages9
JournalBiochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
Volume1841
Issue number11
DOIs
StatePublished - Nov 2014

Bibliographical note

Publisher Copyright:
© 2014 Elsevier B.V.

Keywords

  • Munc13-4
  • Platelet
  • Platelet activation
  • Secretion
  • Sphingosine

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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