Lyso-glycosphingolipids mobilize calcium from brain microsomes via multiple mechanisms.
Recently, we demonstrated that the GSL (glycosphingolipid), GlcCer (glucosylceramide), modulates Ca2+ release from intracellular stores and from microsomes by sensitizing the RyaR (ryanodine receptor), a major Ca2+-release channel of the endoplasmic reticulum, whereas the lyso derivative of GlcCer, namely GlcSph (glucosylsphingosine), induced Ca2+ release via a mechanism independent of the RyaR [Lloyd-Evans, Pelled, Riebeling, Bodennec, de-Morgan, Waller, Schiffmann and Futerman (2003) J. Biol. Chem. 278, 23594-23599]. We now systematically examine the mechanism by which GlcSph and other lyso-GSLs modulate Ca2+ mobilization from rat brain cortical and cerebellar microsomes. GlcSph, lactosylsphingosine and galactosylsphingosine all mobilized Ca2+, but at significantly higher concentrations than those required for GlcCer-mediated sensitization of the RyaR. GlcSph-induced Ca2+ mobilization was partially blocked by heparin, an inhibitor of the Ins(1,4,5) P3 receptor, and also partially blocked by thapsigargin or ADP, inhibitors of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase), but completely blocked when both acted together. In contrast, neither lactosylsphingosine nor galactosylsphingosine had any effect on Ca2+ release via either the Ins(1,4,5) P3 receptor or SERCA, but acted as agonists of the RyaR. Finally, and surprisingly, all three lyso-GSLs reversed inhibition of SERCA by thapsigargin. We conclude that different lyso-GSLs modulate Ca2+ mobilization via different mechanisms, and discuss the relevance of these findings to the GSL storage diseases in which lyso-GSLs accumulate.
Lloyd-Evans
Emyr
E
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Pelled
Dori
D
Riebeling
Christian
C
Futerman
Anthony H
AH
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D006028:Glycosphingolipids / Q000494:pharmacology*; D007295:Inositol Phosphates / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects* / Q000378:metabolism; D008954:Models, Biological; D011609:Psychosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000494:pharmacology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
D006028:Glycosphingolipids; D007295:Inositol Phosphates; D012433:Ryanodine; C023601:lactosylsphingosine; D011609:Psychosine; C092449:inositol 1,2,3-trisphosphate; C035742:sphingosyl beta-glucoside; D019284:Thapsigargin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D013110:Sphingosine; D002118:Calcium