Abolition of G protein inhibition ofα1Aandα1Bcalcium channels by co-expression of theβ3subunit

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Abstract
Three different classes of α 1 Ca2+ channel (α 1A, α 1B, α 1C) were expressed in Xenopus oocytes to determine whether G protein-mediated inhibition is an inherent property of the α 1, subunit itself, and if so, whether co-expression of auxiliary subunits modulates the inhibition seen. From our data it is apparent that either α 1A or α 1B Ca2+ channels expressed alone are sufficient for voltage-dependent G protein inhibition. α 1C Ca2+ channels expressed alone do not exhibit the G protein inhibition seen in α 1A and α 1B channels. Additionally, co-expression of the β 3 subunit abolishes the ability of G proteins to inhibit currents through α 1A and α 1B Ca2+ channels. Differential sensitivity of α 1 as well as modulation of properties by β 3 provide a potential mechanism for the regulation of G protein-mediated inhibition in neurons.