Sphingosylphosphorylcholine activates Gq, Gi-2, and Gi-3 in thyroid FRTL-5 cells: implications for the activation of calcium fluxes and Na+-H+ exchange

In the present investigation of rat thyroid FRTL-5 cells, we show using reverse-transcriptase PCR that these cells express both Edg-1 and Edg-5. We show using a [35S]GTPgammaS-binding assay that sphingosylphosphorylcholine (SPC), which binds to both Edg-1 and EDG-5, activates Gq, Gi-2, and Gi-3 prot...

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Bibliographic Details
Published inBiochemical and biophysical research communications Vol. 258; no. 3; p. 812
Main Authors Nikmo, A, Björklund, S, Vainio, M, Ekokoski, E, Törnquist, K
Format Journal Article
LanguageEnglish
Published United States 19.05.1999
Subjects
Animals
Base Sequence
Biopolymers
Calcium - metabolism
Cell Line
DNA Primers
GTP-Binding Proteins - metabolism
Ion Transport
Phosphorylcholine - analogs & derivatives
Phosphorylcholine - pharmacology
Rats
Sodium-Hydrogen Exchangers - metabolism
Sphingosine - analogs & derivatives
Sphingosine - pharmacology
Tetradecanoylphorbol Acetate - pharmacology
Thyroid Gland - cytology
Thyroid Gland - drug effects
Thyroid Gland - metabolism
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Summary:In the present investigation of rat thyroid FRTL-5 cells, we show using reverse-transcriptase PCR that these cells express both Edg-1 and Edg-5. We show using a [35S]GTPgammaS-binding assay that sphingosylphosphorylcholine (SPC), which binds to both Edg-1 and EDG-5, activates Gq, Gi-2, and Gi-3 proteins. SPC potently increases intracellular free calcium concentrations ([Ca2+]i). This effect is mediated through both Gq and Gi proteins, as the mobilization of sequestered calcium was insensitive to pertussis toxin (i.e., mediated by Gq), while the SPC-evoked calcium entry was inhibited by pretreatment with pertussis toxin (i.e., mediated by Gi). Furthermore, SPC in a concentration-dependent manner increases intracellular pH in acidified cells via a Na+-H+ exchange mechanism. The enhanced activation of Na+-H+ exchange is independent of both an increase in [Ca2+]i and an activation of protein kinase C. The effect of SPC on Na+-H+ exchange is insensitive to pertussis toxin, suggesting an effect mediated via Gq.
ISSN:0006-291X