title: Sphingosine 1-phosphate mobilizes sequestered calcium, activates calcium entry, and stimulates deoxyribonucleic acid synthesis in thyroid FRTL-5 cells.
abstract: Sphingosine 1-phosphate (SPP) potently mobilizes sequestered calcium and is a mitogen in several cell types. In the present investigation, we have evaluated the effect of SPP on intracellular free calcium concentration ([Ca2+]i) and synthesis of DNA in thyroid FRTL-5 cells. SPP rapidly and transiently mobilized sequestered calcium and stimulated entry of extracellular calcium. The entry of calcium, but not the mobilization, was in part inhibited by pretreatment with pertussis toxin (Ptx), and by activation of protein kinase C. SPP did not stimulate the production of inositol 1,4,5-trisphosphate. SPP stimulated the incorporation of 3H-thymidine in a time- and dose-dependent manner. The effect was not inhibited by Ptx. Furthermore, SPP stimulated the activation of the proto-oncogene c-fos. SPP rapidly tyrosine-phosphorylated an approximately 66 kDa protein. This phosphorylation persisted for at least 1 h. Pretreatment of the cells with genistein abolished the SPP-evoked tyrosine phosphorylation, and attenuated the SPP-evoked increase in [Ca2+]i. Furthermore, the SPP-evoked activation of Na+-H+ exchange was inhibited by genistein. The phosphorylation was not attenuated by pretreatment of the cells with Ptx. SPP per se did not affect cellular cAMP levels but attenuated the TSH-evoked increase in cAMP. As the effect of SPP might be due to activation of phospholipase D, we tested whether phosphatidic acid (PA) mobilized calcium or stimulated the incorporation of 3H-thymidine. PA mobilized sequestered calcium but did not stimulate calcium entry. PA very modestly enhanced the incorporation of 3H-thymidine. Our results suggest, that SPP stimulates DNA synthesis and activates entry of calcium in FRTL-5 cells. The effect on calcium entry appears to be dependent, at least in part, on one or several tyrosine kinases.
authors.affiliation: Department of Biosciences, University of Helsinki, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Törnquist
authors.forename: P
authors.initials: P
authors.lastname: Saarinen
authors.forename: M
authors.initials: M
authors.lastname: Vainio
authors.forename: M
authors.initials: M
authors.lastname: Ahlström
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001483:Base Sequence; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D004247:DNA / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D017931:DNA Primers / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein; D006863:Hydrogen-Ion Concentration; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007529:Isoflavones / Q000494:pharmacology; D008246:Lysophospholipids; D037342:Pertussis Toxin; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000235:genetics; D051381:Rats; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013961:Thyroid Gland / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D004791:Enzyme Inhibitors; D007529:Isoflavones; D008246:Lysophospholipids; D016760:Proto-Oncogene Proteins c-fos; D010566:Virulence Factors, Bordetella; D014316:Tritium; C060506:sphingosine 1-phosphate; D016718:Arachidonic Acid; D015544:Inositol 1,4,5-Trisphosphate; D004247:DNA; D019833:Genistein; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D013110:Sphingosine; D002118:Calcium; D013936:Thymidine