title: SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation.
abstract: Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation.
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.|Department of Chemistry, Tokyo University of Science, Tokyo, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ohtsuka
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Iguchi
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Moyuru
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Kaneda
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Iida
authors.affiliation: Department of Chemistry, Tokyo University of Science, Tokyo, Japan.
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Shimonaka
authors.affiliation: Stem Cell Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Hara
authors.affiliation: Baxalta Japan Ltd., Tokyo, Japan.
authors.forename: Morio
authors.initials: M
authors.lastname: Arai
authors.affiliation: Department of Drug Metabolism and Clinical Pharmacokinetics, School of Pharmaceutical Sciences, Ohu University, Fukushima, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Koike
authors.affiliation: Department of Biochemistry, School of Pharmaceutical Sciences, Ohu University, Fukushima, Japan.
authors.forename: Naomasa
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Kohji
authors.initials: K
authors.lastname: Kasahara
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D054377:Chemokine CXCL12 / Q000378:metabolism*; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D010974:Platelet Aggregation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism*
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019718:Receptors, CXCR4; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt