Absence of modulation of the expressed calcium channel α1G subunit by α2δ subunits

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Abstract
The modulatory action of the α2δ subunit on various high-voltage-activated calcium channels has been demonstrated previously. However, very little is known about auxiliary subunit modulation of low-voltage-activated (LVA) calcium channels. We have examined the modulation of the α1G subunit corresponding to the neuronal T-type calcium channel by the ubiquitously expressed α2δ-1 and brain-specific α2δ-3 subunits. The α1G subunit was expressed alone or in combination with either the α2δ-1 or α2δ-3 subunit in human embryonic kidney (HEK 293) cells and whole-cell barium currents were measured. The current density-voltage relationships for peak and sustained current, kinetics of current activation and inactivation, voltage dependence of current inactivation and time course of the recovery from inactivation were analysed for each type of expressed channel. No significant difference was found for any of the examined parameters. These results suggest that the LVA α1G channel is not regulated by known auxiliary α2δ subunits.