Lysophosphatidylcholine Augments Cav3.2 but Not Cav3.1 T-Type Ca2+ Channel Current Expressed in HEK-293 Cells

Abstract

Lysophosphatidylcholine (LPC) has been shown to induce electrophysiological disturbances to arrhythmogenesis. However, the effects of LPC on the low-voltage-activated T-type Ca²⁺ channels in the heart are not understood yet. We found that LPC increases the T-type Ca²⁺ channel current (I_Ca.T) in neonatal rat cardiomyocytes. To further investigate the underlying modulatory mechanism of LPC on T-type Ca²⁺ channels, we utilized HEK-293 cells stably expressing α1G and α1H subunits (HEK-293/α1G and HEK-293/α1H), by use of patch-clamp techniques. A low concentration of LPC (10 µmol/l) significantly increased Ca_v3.2 I_Ca.T (α1H) that were similar to those observed in neonatal rat cardiomyocytes. Activation and steady-state inactivation curves were shifted in the hyperpolarized direction by 5.1 ± 0.2 and 4.6 ± 0.4 mV, respectively, by application of 10 µmol/l LPC. The pretreatment of cells with a protein kinase C inhibitor (chelerythrine) attenuated the effects of LPC on I_Ca.T (α1H). However, the application of LPC failed to modify Ca_v3.1 (α1G) I_Ca.T at concentrations of 10–50 µmol/l. In conclusion, these data demonstrate that extracellularly applied LPC augments Ca_v3.2 I_Ca.T (α1H) but not Ca_v3.1 I_Ca.T (α1G) in a heterologous expression system, possibly by modulating protein kinase C signaling.