title: C(6)-ceramide inhibited Na(+) currents by intracellular Ca(2+) release in rat myoblasts.
abstract: Ceramides are novel second messengers that may mediate signaling leading to apoptosis and the regulation of cell cycle progression. Moreover, ceramide analogs have been reported to directly modulate K(+) and Ca(2+) channels in different cell types. In this report, the effect of C(6)-ceramide on the voltage-gated inward Na(+) currents (I(Na)) in cultured rat myoblasts was investigated using whole-cell current recording and a fluorescent Ca(2+) imaging experiment. At concentrations of 1-100 microM, ceramide produced a dose-independent and reversible inhibition of I(Na). Ceramide also significantly shifted the steady-state inactivation curve of I(Na) by 16 mV toward the hyperpolarizing potential, but did not alter the steady-state activation properties. C(2)-ceramide caused a similar inhibitory effect on I(Na) amplitude. However, dihydro-C(6)-ceramide, the inactive analog of ceramide, failed to modulate I(Na). The effect of C(6)-ceramide on I(Na) was abolished by intracellular infusion of the Ca(2+)-chelating agent BAPTA, but was mimicked by application of caffeine. Blocking the release of Ca(2+) from the sarcoplasmic reticulum with xestospongin C or heparin, an inositol 1,4,5-trisphosphate (IP(3)) receptor blocker, induced a gradual increase in I(Na) amplitude and eliminated the effect of ceramide on I(Na). In contrast, ruthenium red, which is a blocker of the ryanodine-sensitive Ca(2+) receptor did not affect the action of C(6)-ceramide on I(Na). Intracellular application of the G-protein agonist GTPgammaS also induced a gradual decrease in I(Na) amplitude, while the G-protein antagonist GDPbetaS eliminated the effect of C(6)-ceramide on I(Na). Calcium imaging showed that C(6)-ceramide could give rise to a significant elevation of intracellular calcium. Our data show that increased calcium release through the IP(3)-sensitive Ca(2+) receptor, which probably occurred through the G-protein and phospholipase C pathway, may be responsible for C(6)-ceramide-induced inhibition of the I(Na) of rat myoblasts.
authors: School of Life Sciences, Institute of Brain Science, State Key Laboratory of Medical Neurobiology Fudan University, Shanghai, P.R. China.
authors: Zheng
authors: Z
authors: Liu
authors: Jian-Guang
authors: JG
authors: Xu
authors: Hua
authors: H
authors: Zhang
authors: Yan-Jia
authors: YJ
authors: Fang
authors: Yan-Ai
authors: YA
authors: Mei
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D002147:Calmodulin / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D032448:Myoblasts, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D002147:Calmodulin; D002518:Ceramides; D002614:Chelating Agents; D015222:Sodium Channels; C101954:N-caproylsphingosine; D004533:Egtazic Acid; D012964:Sodium; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid