Sphingosine kinase-mediated Ca2+ signalling by G-protein-coupled receptors.
Formation of inositol 1,4,5-trisphosphate (IP3) by phospholipase C (PLC) with subsequent release of Ca2+ from intracellular stores, is one of the major Ca2+ signalling pathways triggered by G-protein-coupled receptors (GPCRs). However, in a large number of cellular systems, Ca2+ mobilization by GPCRs apparently occurs independently of the PLC-IP3 pathway, mediated by an as yet unknown mechanism. The present study investigated whether sphingosine kinase activation, leading to production of sphingosine-1-phosphate (SPP), is involved in GPCR-mediated Ca2+ signalling as proposed for platelet-derived growth factor and FcepsilonRI antigen receptors. Inhibition of sphingosine kinase by DL-threo-dihydrosphingosine and N,N-dimethylsphingosine markedly inhibited [Ca2+]i increases elicited by m2 and m3 muscarinic acetylcholine receptors (mAChRs) expressed in HEK-293 cells without affecting mAChR-induced PLC stimulation. Activation of mAChRs rapidly and transiently stimulated production of SPP in HEK-293 cells. Finally, intracellular injection of SPP induced a rapid and transient Ca2+ mobilization in HEK-293 cells which was not antagonized by heparin. We conclude that mAChRs utilize the sphingosine kinase-SPP pathway in addition to PLC-IP3 to mediate Ca2+ mobilization. As Ca2+ signalling by various, but not all, GPCRs in different cell types was likewise attenuated by the sphingosine kinase inhibitors, we suggest a general role for sphingosine kinase, besides PLC, in mediation of GPCR-induced Ca2+ signalling.
Meyer zu Heringdorf
D
D
Institut für Pharmakologie, Universität GH Essen, Essen, Germany.
Lass
H
H
Alemany
R
R
Laser
K T
KT
Neumann
E
E
Zhang
C
C
Schmidt
M
M
Rauen
U
U
Jakobs
K H
KH
van Koppen
C J
CJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008246:Lysophospholipids; D008845:Microinjections; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D018002:Receptors, Bradykinin / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000099157:Sphingosine Kinase
D002118:Calcium; D004791:Enzyme Inhibitors; D019204:GTP-Binding Proteins; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D018002:Receptors, Bradykinin; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D011976:Receptors, Muscarinic; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C061800:N,N-dimethylsphingosine; C005682:safingol