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 language | English |
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Pages (from-to) | 1581-1589 |
Number of pages | 9 |
Journal | Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids |
Volume | 1841 |
Issue number | 11 |
DOIs | |
State | Published - 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