title: Sphingosine-1-phosphate, a platelet-derived lysophospholipid mediator, negatively regulates cellular Rac activity and cell migration in vascular smooth muscle cells.
abstract: Previous studies demonstrated that sphingosine-1-phosphate (S1P) induced migration of human umbilical vein endothelial cells (HUVECs) whereas it inhibited that of vascular smooth muscle cells (SMCs). This study explored the molecular mechanisms underlying the contrasting S1P actions on vascular cell motility. In rat and human aortic SMCs, the chemoattractant platelet-derived growth factor B-chain (PDGF) induced rapid 5- to 6-fold increases in the cellular amount of GTP-bound, active form of Rac. S1P did not affect PDGF-stimulated tyrosine phosphorylation of PDGF-beta receptor, but strongly inhibited PDGF-induced Rac activation, with a dose-response relationship similar to that for inhibition of PDGF-elicited chemotaxis. Dihydrosphingosine-1-phosphate, which is a weaker agonist for the S1P receptors, but not an inactive ligand sphingosine, also inhibited PDGF-stimulated chemotaxis and Rac activation although to lesser extents compared with S1P, suggesting that negative regulation by S1P of both chemotaxis and Rac was a receptor-mediated process. In contrast, S1P by itself stimulated Rac activity in HUVECs. Among the five S1P receptor isoforms, SMCs prominently expressed Edg-5 mRNA, whereas HUVECs expressed abundant Edg-1 mRNA but lacked detectable expression of Edg-5 mRNA. Adenovirus-mediated expression of a dominant-negative form of either Rac or Cdc42, but not RhoA, markedly attenuated chemotaxis of SMCs and HUVECs toward PDGF and S1P, respectively. Overexpression of Edg-1 in SMCs and Edg-5 in HUVECs reduced S1P-induced inhibition and stimulation, respectively, of Rac activity and migration. These results together indicate that Edg isoform-specific, negative or positive regulation of cellular Rac activity is critically involved in S1P-mediated bimodal regulation of cell motility in SMCs and HUVECs.
authors.affiliation: Department of Physiology, Kanazawa University, Graduate School of Medicine, Kanazawa, Ishikawa, Japan.
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Ryu
authors.forename: Noriko
authors.initials: N
authors.lastname: Takuwa
authors.forename: Naotoshi
authors.initials: N
authors.lastname: Sugimoto
authors.forename: Sotaro
authors.initials: S
authors.lastname: Sakurada
authors.forename: Soichiro
authors.initials: S
authors.lastname: Usui
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsui
authors.forename: Yoh
authors.initials: Y
authors.lastname: Takuwa
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D022081:Cell Surface Extensions / Q000187:drug effects; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D008246:Lysophospholipids / Q000378:metabolism* / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D049312:Receptors, Lysophospholipid; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D017874:Immediate-Early Proteins; D008246:Lysophospholipids; D009687:Nuclear Proteins; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D049312:Receptors, Lysophospholipid; D014157:Transcription Factors; C060506:sphingosine 1-phosphate; D020797:Receptor, Platelet-Derived Growth Factor beta; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D013110:Sphingosine