Sphingosine 1-phosphate stimulates rho-mediated tyrosine phosphorylation of focal adhesion kinase and paxillin in Swiss 3T3 fibroblasts.
Sphingosine 1-phosphate (SPP), a sphingolipid second messenger implicated in the mitogenic action of platelet-derived growth factor [Olivera, A. and Spiegel, S. (1993) Nature (London) 365, 557-560], induced rapid reorganization of the actin cytoskeleton resulting in stress-fibre formation. SPP also induced transient tyrosine phosphorylation of focal adhesion kinase (p125(FAK)), a cytosolic tyrosine kinase that localizes in focal adhesions, and of the cytoskeleton-associated protein paxillin. Exoenzyme C3 transferase, which ADP-ribosylates Rho (a Ras-related small GTP binding protein) on asparagine-41 and renders it biologically inactive, inhibited both stress-fibre formation and protein tyrosine phosphorylation induced by SPP. Thus Rho may be an upstream regulator of both stress-fibre formation and tyrosine phosphorylation of p125(FAK) and paxillin. Pretreatment with PMA, an activator of protein kinase C (PKC), inhibited the stimulation of stress-fibre formation induced by 1-oleoyl-lysophosphatidic acid (LPA) but not that by SPP. Similarly, PMA also decreased LPA-induced tyrosine phosphorylation of p125(FAK) and paxillin without abrogating the response to SPP. Thus PKC is involved in LPA- but not SPP-dependent signalling. The polyanionic drug suramin, a broad-specificity inhibitor of ligand-receptor interactions, did not inhibit either the mitogenic effect of SPP or its stimulation of tyrosine phosphorylation of p125(FAK). However, suramin markedly inhibited these responses induced by LPA. These results suggest that in contrast with LPA, SPP may be acting intracellularly in Swiss 3T3 fibroblasts to stimulate tyrosine phosphorylation of p125(FAK) and paxillin and cell growth.
Wang
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Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington DC 20007, USA.
Nobes
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CD
Hall
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A
Spiegel
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S
D016475:3T3 Cells / Q000187:drug effects / Q000201:enzymology; D036002:ADP Ribose Transferases / Q000494:pharmacology; D008841:Actin Cytoskeleton / Q000187:drug effects*; D000199:Actins / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019204:GTP-Binding Proteins / Q000502:physiology*; D008246:Lysophospholipids / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051379:Mice; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D015290:Second Messenger Systems; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013268:Stimulation, Chemical; D013498:Suramin / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020741:rho GTP-Binding Proteins
D000199:Actins; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D008246:Lysophospholipids; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011994:Recombinant Proteins; C060506:sphingosine 1-phosphate; D013498:Suramin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D011493:Protein Kinase C; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; C032881:lysophosphatidic acid