Molecular architecture of the G_i-bound TRPC5 ion channel

G-protein coupled receptors (GPCRs) and ion channels serve as keymolecular switches through which extracellular stimuli are transformed into intracellular effects, and it has long been postulated that ion channels are direct effector molecules of the alpha subunit of G-proteins (G alpha). However, no complete structural evidence supporting the direct interaction between G alpha and ion channels is available. Here, we present the cryo-electron microscopy structures of the human transient receptor potential canonical 5 (TRPC5)-G alpha(i3) complexes with a 4:4 stoichiometry in lipid nanodiscs. Remarkably, G alpha(i3) binds to the ankyrin repeat edge of TRPC5 similar to 50 A away from the cell membrane. Electrophysiological analysis shows that G alpha(i3) increases the sensitivity of TRPC5 to phosphatidylinositol 4,5-bisphosphate (PIP2), thereby rendering TRPC5 more easily opened in the cell membrane, where the concentration of PIP2 is physiologically regulated. Our results demonstrate that ion channels are one of the direct effector molecules of Ga proteins triggered by GPCR activation-providing a structural framework for unraveling the crosstalk between two major classes of transmembrane proteins: GPCRs and ion channels.