The effect of α2-δ and other accessory subunits on expression and properties cf the calcium channel α1G

1. The effect has been examined of the accessory alpha 2-delta and beta subunits on the properties of alpha 1G-currents expressed in monkey COS-7 cells and Xenopus oocytes. 2. In immunocytochemical experiments, the co-expression of alpha 2-delta increased plasma membrane localization of expressed alpha 1G and conversely the heterologous expression of alpha 1G increased immunostaining for endogenous alpha 2-delta, suggesting an interaction between the two subunits. 3. Heterologous expression of alpha 2-delta together with alpha 1G in COS-7 cells increased the amplitude of expressed alpha 1G currents by about 2-fold. This finding was confirmed in the Xenopus oocyte expression system. The truncated delta construct did not increase alpha 1G current amplitude, or increase its plasma membrane expression. This indicates that it is the exofacial alpha 2 domain that is involved in the enhancement by alpha 2-delta. 4. beta 1b also produced an increase of functional expression of alpha 1G, either in the absence or the presence of heterologously expressed alpha 2-delta, whereas the other beta subunits had much smaller effects. 5. None of the accessory subunits had any marked influence on the voltage dependence or kinetics of the expressed alpha 1G currents. These results therefore suggest that alpha 2-delta and beta 1b interact with alpha 1G to increase trafficking of, or stabilize, functional alpha 1G channels expressed at the plasma membrane.