Modulation of a brain voltage-gated K⁺ channel by syntaxin 1A requires the physical interaction of Gβγ with the channel

Recently we suggested that direct interactions between voltage-gated K⁺ channels and proteins of the exocytotic machinery, such as those observed between the Kv1.1/Kvβ channel, syntaxin 1A, and SNAP-25 may be involved in neurotransmitter release. Furthermore, we demonstrated that the direct interaction with syntaxin 1A enhances the fast inactivation of Kv1.1/Kvβ1.1 in oocytes. Here we show that G-protein βγ subunits play a crucial role in the enhancement of inactivation by syntaxin 1A. The effect caused by overexpression of syntaxin 1A is eliminated in the presence of chelators of endogenous βγ subunits in the whole cell and at the plasma membrane. Conversely, enhancement of inactivation caused by overexpression of β_1γ2 subunits is eliminated upon knock-down of endogenous syntaxin or its scavenging at the plasma membrane. We further show that the N terminus of Kv1.1 binds brain synaptosomal and recombinant syntaxin 1A and concomitantly binds β_1γ2; the binding of β_1γ2 enhances that of syntaxin 1A. Taken together, we suggest a mechanism whereby syntaxin and G protein βγ subunits interact concomitantly with a Kv channel to regulate its inactivation.