Relative contributions of G protein, channel, and receptor to voltage-dependent inhibition of neuronal N-type and P/Q-type calcium channels in HEK 293 cell lines.

The voltage-dependent modulation of neuronal voltage-gated calcium channels by heterotrimeric G protein-coupled receptors potentially provides a means for activity-dependent modulation of synaptic efficacy. Recent attention has focused upon the molecular mechanisms by which such G proteins influence the biophysical properties of calcium channels. We have used an HEK 293-based heterologous system which stably expresses human neuronal calcium channels to address the relative contributions of receptor, G protein, and channel to voltage-dependent inhibition. We find that the receptor and channel subtype only insignificantly influence the time it takes to re-establish modulation following voltage-dependent relief of inhibition. In contrast, the G protein subtype mediating inhibition appears to play a significant part in this process. These results emphasize the importance of G protein subtype in the modulation of neuronal calcium channels.