title: Sphingosine kinase-mediated calcium signaling by muscarinic acetylcholine receptors.
abstract: Based on the finding that G protein-coupled receptors (GPCRs) can induce Ca2+ mobilization, apparently independent of the phospholipase C (PLC)/inositol-1,4,5-trisphosphate (IP3) pathway, we investigated whether sphingosine kinase, which generates sphingosine-1-phosphate (SPP), is involved in calcium signaling by mAChR and other GPCRs. Inhibition of sphingosine kinase by DL-threo-dihydrosphingosine and N,/N-dimethylsphingosine markedly inhibited [Ca2+]i increases elicited by M2 and M3 mAChRs in HEK-293 cells without affecting PLC activation. Activation of M2 and M3 mAChR rapidly and transiently stimulated production of SPP. Furthermore, microinjection of SPP into HEK-293 cells induced rapid and transient Ca2+ mobilization. Pretreatment of HEK-293 cells with the calcium chelator BAPTA/AM fully blocked mAChR-induced SPP production. On the other hand, incubation of HEK-293 cells with calcium ionophores activated SPP production. Similar findings were obtained for formyl peptide and P2Y2 purinergic receptors in HL-60 cells. On the basis of these studies we propose, that following initial IP3 production by receptor-mediated PLC activation, a local discrete increase in [Ca2+]i induces sphingosine kinase stimulation, which ultimately leads to full calcium mobilization. Thus, sphingosine kinase activation most likely represents an amplification system for calcium signaling by mAChRs and other GPCRs.
authors.affiliation: Institut für Pharmakologie, Universitätsklinikum Essen, Germany. van_koppen@uni-essen.de
authors.forename: C J
authors.initials: CJ
authors.lastname: van Koppen
authors.forename: D
authors.initials: D
authors.lastname: Meyer zu Heringdorf
authors.forename: R
authors.initials: R
authors.lastname: Alemany
authors.forename: K H
authors.initials: KH
authors.lastname: Jakobs
mesh_terms: D020013:Calcium Signaling; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D018679:Cholinergic Agonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011869:Radioligand Assay; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism*; D000099157:Sphingosine Kinase
chemical_list: D002217:Carbachol; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D015544:Inositol 1,4,5-Trisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); D011976:Receptors, Muscarinic; D013110:Sphingosine; D000099157:Sphingosine Kinase