Absence of modulation of the expressed calcium channel alpha1G subunit by alpha2delta subunits.

1. The modulatory action of the alpha2delta 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 alpha1G subunit corresponding to the neuronal T-type calcium channel by the ubiquitously expressed alpha2delta-1 and brain-specific alpha2delta-3 subunits. 2. The alpha1G subunit was expressed alone or in combination with either the alpha2delta-1 or alpha2delta-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. 3. These results suggest that the LVA alpha1G channel is not regulated by known auxiliary alpha2delta subunits.