Binding of Gα_o N-Terminus is Responsible for the Voltage-Resistant Inhibition of α_1A (P/Q-Type, Ca_v2.1) Ca²⁺ Channels

Abstract

G-protein-mediated inhibition of presynaptic voltage-dependent Ca²⁺ channels is comprised of voltage-dependent and -resistant components. The former is caused by a direct interaction of Ca²⁺ channel α₁ subunits with Gβγ, whereas the latter has not been well characterized. Here, we show that the N-terminus of Gα_o is critical for the interaction with the C-terminus of the P/Q-type channel subunit, and that the binding induces voltage-resistant inhibition. A P/Q-type C-terminal peptide, an antiserum raised against the Gα_o N-terminus, and a Gα_o N-terminal peptide all attenuated the voltage-resistant inhibition of P/Q-type currents. Furthermore, the N-terminus of Gα_o bound to the C-terminus of α_1A in vitro, which was prevented either by the P/Q-type channel C-terminal or Gα_o N-terminal peptide. Although the C-terminal domain of the N-type channel showed similar ability to binding with Gα_o N-terminus, the above-mentioned treatments were ineffective in the N-type channel current. These findings demonstrate that the voltage-resistant inhibition of the P/Q-type channel is caused by the interaction between the C-terminal domain of the Ca²⁺ channel α_1A subunit and the N-terminal region of Gα_o.