Sphingosine releases Ca2+ from intracellular stores via the ryanodine receptor in sea urchin egg homogenates.
Various reports have demonstrated that the sphingolipids sphingosine and sphingosine-1-phosphate are able to induce Ca2+ release from intracellular stores in a similar way to second messengers. Here, we have used the sea urchin egg homogenate, a model system for the study of intracellular Ca2+ release mechanisms, to investigate the effect of these sphingolipids. While ceramide and sphingosine-1-phosphate did not display the ability to release Ca2+, sphingosine stimulated transient Ca2+ release from thapsigargin-sensitive intracellular stores. This release was inhibited by ryanodine receptor blockers (high concentrations of ryanodine, Mg2+, and procaine) but not by pre-treatment of homogenates with cADPR, 8-bromo-cADPR or blockers of other intracellular Ca2+ channels. However, sphingosine rendered the ryanodine receptor refractory to cADPR. We propose that, in the sea urchin egg, sphingosine is able to activate the ryanodine receptor via a mechanism distinct from that used by cADPR.
Floriddia
E M
EM
DiSCAFF, Universita' del Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy.
Pace
D
D
Genazzani
A A
AA
Canonico
P L
PL
Condorelli
F
F
Billington
R A
RA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002413:Cations, Divalent / Q000378:metabolism; D010063:Ovum / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012617:Sea Urchins / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D013110:Sphingosine / Q000494:pharmacology*
D002413:Cations, Divalent; D019837:Ryanodine Receptor Calcium Release Channel; D013110:Sphingosine; D002118:Calcium