title: Lack of sphingosine 1-phosphate-degrading enzymes in erythrocytes.
abstract: Platelets are known to store a large amount of the bioactive lipid molecule sphingosine 1-phosphate (S1P) and to release it into the plasma in a stimuli-dependent manner. Erythrocytes can also release S1P, independently from any stimuli. We measured the S1P and sphingosine (Sph) levels in erythrocytes by HPLC and found that the contribution of erythrocyte S1P to whole blood S1P levels is actually higher than that of platelets. In vitro assays demonstrated that erythrocytes possess much weaker Sph kinase activity compared to platelets but lack the S1P-degrading activities of either S1P lyase or S1P phosphohydrolase. This combination may enable erythrocytes to maintain a high S1P content relative to Sph. The absence of both S1P-degrading enzymes has not been reported for other cell types. Thus, erythrocytes may be specialized cells for storing and supplying plasma S1P.
authors.affiliation: Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Kiyoharu
authors.initials: K
authors.lastname: Ito
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Anada
authors.forename: Motohiro
authors.initials: M
authors.lastname: Tani
authors.forename: Mika
authors.initials: M
authors.lastname: Ikeda
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Sano
authors.forename: Akio
authors.initials: A
authors.lastname: Kihara
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D000446:Aldehyde-Lyases / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism*; D002478:Cells, Cultured; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D008246:Lysophospholipids; D008565:Membrane Proteins; C060506:sphingosine 1-phosphate; C401298:sphingosine-1-phosphate phosphatase; D010744:Phosphoric Monoester Hydrolases; D000446:Aldehyde-Lyases; C022649:sphingosine 1-phosphate lyase (aldolase); D013110:Sphingosine