Extracellular mechanism through the Edg family of receptors might be responsible for sphingosine-1-phosphate-induced regulation of DNA synthesis and migration of rat aortic smooth-muscle cells.
Exogenous sphingosine 1-phosphate (S1P) increased cytosolic Ca(2+) concentration, stimulated thymidine incorporation (DNA synthesis) and inhibited cell migration in rat aortic smooth-muscle cells (AoSMCs). Although exogenous sphingosine, a substrate of sphingosine kinase or a precursor of S1P, markedly induced the intracellular accumulation of S1P, the lipid failed to mimic the S1P-induced actions. In contrast, dihydrosphingosine 1-phosphate (DHS1P), an S1P receptor agonist, duplicated these S1P actions even though DHS1P was approx. 20-50-fold less potent than S1P. The pharmacological properties of DHS1P for the S1P receptor subtypes Edg-1, Edg-3, Edg-5 and Edg-6 were compared in Chinese hamster ovary (CHO) cells that were overexpressing the respective receptor. In these S1P-receptor-overexpressing cells, DHS1P was approx. 20-30-fold less potent than S1P for the displacement of [(3)H]S1P binding and inositol phosphate response in Edg-5-expressing CHO cells, as was the case for AoSMCs. However, it was slightly (not more than 3-fold) less potent than S1P in cells expressing Edg-1, Edg-3 or Edg-6. Of the above-mentioned four types of S1P receptor, Edg-5 was abundantly expressed in AoSMCs, as demonstrated by Northern blotting. These results suggest that the intracellular accumulation of S1P is not necessary for the S1P-induced Ca(2+) response, for the stimulation of DNA synthesis or for the inhibition of cell migration. Thus these S1P-induced actions might be mediated through extracellular (or cell-surface) S1P receptors in AoSMCs: Edg-5 might be a most important receptor subtype.
Tamama
K
K
Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan.
Kon
J
J
Sato
K
K
Tomura
H
H
Kuwabara
A
A
Kimura
T
T
Kanda
T
T
Ohta
H
H
Ui
M
M
Kobayashi
I
I
Okajima
F
F
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008246:Lysophospholipids; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D013379:Substrate Specificity; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007295:Inositol Phosphates; D008246:Lysophospholipids; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D010566:Virulence Factors, Bordetella; C060504:dihydrosphingosine 1-phosphate; C060506:sphingosine 1-phosphate; D004247:DNA; D013110:Sphingosine; D002118:Calcium