Persistent sodium currents through brain sodium channels induced by G protein beta gamma subunits

Persistent Na+ currents are thought to be important for integration of neuronal responses. Here, we show that beta gamma subunits of G proteins can induce persistent Na+ currents. Coexpression of G beta(2) gamma(3), G beta(1) gamma(3), or G beta(5) gamma(3), but not G beta(1) gamma(1) subunits with rat brain type IIA Na+ channel alpha subunits in tsA-201 cells greatly enhances a component of Na+ current with a normal voltage dependence of activation but with dramatically slowed and incomplete inactivation and with steady-state inactivation shifted +37 mV. Synthetic peptides containing the proposed G beta gamma-binding motif, Gln-X-X-Glu-Arg, from either adenylyl cyclase 2 or the Na+ channel alpha subunit C-terminal domain reversed the effect of G beta(2) gamma(3), subunits. These results are consistent with direct binding of G beta gamma subunits to the C-terminal domain of the Na+ channel, stabilizing a gating mode responsible for slowed and persistent Na+ current. Modulation of Na+ channel gating by G beta gamma subunits is expected to have profound effects on neuronal excitability.