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C 6 ‐ceramide inhibited Na + currents by intracellular Ca 2+ release in rat myoblasts
Author(s) -
Liu Zheng,
Xu JianGuang,
Zhang Hua,
Fang YanJia,
Mei YanAi
Publication year - 2007
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.21106
Subject(s) - ceramide , second messenger system , bapta , ryanodine receptor , intracellular , chemistry , biophysics , inositol , endoplasmic reticulum , biochemistry , receptor , biology , apoptosis
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 µM, 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 GTPγS also induced a gradual decrease in I Na amplitude, while the G‐protein antagonist GDPβS 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. J. Cell. Physiol. 213: 151–160, 2007. © 2007 Wiley‐Liss, Inc.