(-)-Englerin A binding to human TRPC5 exposes an aromatic interaction network in channel activation.

TRPC4/5 cation channels are polymodal cellular sensors and emerging drug targets in various human pathologies. The plant natural product (-)-englerin A (EA) is a potent, selective TRPC4/5 agonist that has transformed TRPC4/5 research. However, the structural basis of EA-mediated TRPC4/5 activation has remained elusive, limiting our ability to understand and exploit EA's pharmacology. Here, we present nine high-resolution cryo-EM structures of human TRPC5, representing different states and ligand occupancies, which show that EA occupies a conserved lipid binding site between channel subunits. Conformational changes of residues surrounding this binding site - most notably in the aromatic interaction network around Phe520 - result in rearrangement of the pore helices into a pre-open state. Our structural models are consistent with the effects of mutagenesis on EA's potency, efficacy and activation kinetics, and allow us to rationalise competitive inhibition by other TRPC4/5 modulators as well as EA's selectivity profile within the TRPC family. Our structural insights into the mode-of-action of a widely used TRPC4/5 agonist will underpin fundamental TRPC4/5 research and ongoing drug discovery programmes.