Sphingosine 1-Phosphate Induces Platelet Activation through an Extracellular Action and Shares a Platelet Surface Receptor with Lysophosphatidic Acid

doi:10.1074/jbc.272.8.5291

Sphingosine 1-Phosphate Induces Platelet Activation through an Extracellular Action and Shares a Platelet Surface Receptor with Lysophosphatidic Acid*

From The Biomembrane Institute, Seattle, Washington 98119 and
^¶ Department of Pathobiology, University of Washington, Seattle, Washington 98195

** To whom correspondence should be addressed:
Fred Hutchinson Cancer Research Center, 1124 Columbia, M621, Seattle, WA 98104.
Tel.: 206-667-2844; Fax: 206-667-6519. E-mail: yigarash{at}fhcrc.org

↵^§ Present address: Dept. of Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan.
↵^∥ Present address: Pacific Northwest Research Foundation, Division of Biomembrane Research, Seattle, WA 98122.

Abstract

Sphingosine 1-phosphate (Sph-1-P) has been implicated as an intracellular second messenger in many studies. We investigated the metabolism of Sph-1-P and the mechanism by which Sph-1-P induces activation in enucleated and highly differentiated platelets. Platelets lack Sph-1-P lyase activity, possess persistently active sphingosine (Sph) kinase, and abundantly store Sph-1-P. Although exogenous Sph-1-P activated platelets, intracellular Sph-1-P, formed from exogenously added Sph by cytosolic Sph kinase, failed to do so. To support the notion that exogenous Sph-1-P stimulates platelets from outside, contact of platelet surfaces with immobilized Sph-1-P covalently linked to glass particles resulted in platelet activation. Furthermore, we detected the specific binding sites for radiolabeled Sph-1-P on the platelet surface, suggesting extracellular effects of Sph-1-P on plasma membrane receptors. This specific Sph-1-P binding was inhibited not by other sphingolipids but by lysophosphatidic acid (LPA), and platelet aggregation response to LPA was specifically desensitized by prior addition of Sph-1-P. Finally, internally stored Sph-1-P is released extracellularly upon stimulation, and the release correlated well with protein kinase C activation in intact platelets. These results suggest that Sph-1-P acts not intracellularly but intercellularly, following discharge from activated platelets, and shares a platelet surface receptor with LPA.

Footnotes

↵^‡ These two authors contributed equally to the study.
↵* This study was supported by funds from The Biomembrane Institute and in part under a research contract with Otsuka Pharmaceutical Co. and Seikagaku Corp. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

Sph-1-P

sphingosine-1-phosphate

LPA

lysophosphatidic acid

Cer

ceramide

TPA

12-O-tetradecanoylphorbol-13-acetate

Sph

sphingosine.
- Received September 5, 1996.
- Revision received December 6, 1996.