Lysophosphatidic acid-induced Ca2+ mobilization requires intracellular sphingosine 1-phosphate production. Potential involvement of endogenous EDG-4 receptors.
Lysophosphatidic acid (LPA)-mediated Ca(2+) mobilization in human SH-SY5Y neuroblastoma cells does not involve either inositol 1,4, 5-trisphosphate (Ins(1,4,5)P(3))- or ryanodine-receptor pathways, but is sensitive to inhibitors of sphingosine kinase. This present study identifies Edg-4 as the receptor subtype involved and investigates the presence of a Ca(2+) signaling cascade based upon the lipid second messenger molecule, sphingosine 1-phosphate. Both LPA and direct G-protein activation increase [(3)H]sphingosine 1-phosphate levels in SH-SY5Y cells. Measurements of (45)Ca(2+) release in premeabilized SH-SY5Y cells indicates that sphingosine 1-phosphate, sphingosine, and sphingosylphosphorylcholine, but not N-acetylsphingosine are capable of mobilizing intracellular Ca(2+). Furthermore, the effect of sphingosine was attenuated by the sphingosine kinase inhibitor dimethylsphingosine, or removal of ATP. Confocal microscopy demonstrated that LPA stimulated intracellular Ca(2+) "puffs," which resulted from an interaction between the sphingolipid Ca(2+) release pathway and Ins(1,4,5)P(3) receptors. Down-regulation of Ins(1,4,5)P(3) receptors uncovered a Ca(2+) response to LPA, which was manifest as a progressive increase in global cellular Ca(2+) with no discernible foci. We suggest that activation of an LPA-sensitive Edg-4 receptor solely utilizes the production of intracellular sphingosine 1-phosphate to stimulate Ca(2+) mobilization in SH-SY5Y cells. Unlike traditional Ca(2+) release processes, this novel pathway does not require the progressive recruitment of elementary Ca(2+) events.
Young
K W
KW
Department of Cell Physiology and Pharmacology, Medical Sciences Building, University of Leicester, University Road, Leicester, LE1 9HN United Kingdom.
Bootman
M D
MD
Channing
D R
DR
Lipp
P
P
Maycox
P R
PR
Meakin
J
J
Challiss
R A
RA
Nahorski
S R
SR
D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D008246:Lysophospholipids / Q000494:pharmacology*; D009447:Neuroblastoma; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008246:Lysophospholipids; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; C060506:sphingosine 1-phosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D020962:Heterotrimeric GTP-Binding Proteins; C061800:N,N-dimethylsphingosine; D013110:Sphingosine; D002118:Calcium