The effect of alpha2-delta and other accessory subunits on expression and properties of the calcium channel alpha1G.

1. The effect has been examined of the accessory alpha2-delta and beta subunits on the properties of alpha1G currents expressed in monkey COS-7 cells and Xenopus oocytes. 2. In immunocytochemical experiments, the co-expression of alpha2-delta increased plasma membrane localization of expressed alpha1G and conversely, the heterologous expression of alpha1G increased immunostaining for endogenous alpha2-delta, suggesting an interaction between the two subunits. 3. Heterologous expression of alpha2-delta together with alpha1G in COS-7 cells increased the amplitude of expressed alpha1G currents by about 2-fold. This finding was confirmed in the Xenopus oocyte expression system. The truncated delta construct did not increase alpha1G current amplitude, or increase its plasma membrane expression. This indicates that it is the exofacial alpha2 domain that is involved in the enhancement by alpha2-delta. 4. Beta1b also produced an increase of functional expression of alpha1G, either in the absence or the presence of heterologously expressed alpha2-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 alpha1G currents. These results therefore suggest that alpha2-delta and beta1b interact with alpha1G to increase trafficking of, or stabilize, functional alpha1G channels expressed at the plasma membrane.