Mechanism of (-)-Englerin A and calcium binding on the human TRPC5 channel.

The natural product (-)-Englerin A (EA) selectively inhibits renal cancer cell growth by potently activating TRPC4 and TRPC5-containing ion channels. However, its binding site on these channels has remained elusive. In this study, we present two cryo-EM structures of human TRPC5 in complex with EA at 2.5 and 2.6 à resolution, which reveal the EA-binding site and identify two major conformations influenced by calcium. EA binds between the pore helix and S5/S6 helices of hTRPC5, forming critical hydrophobic and polar interactions that underscore its specificity. Calcium binding at the intracellular domain of TRPC5 induces structural changes that stabilize the domain in a compact conformation. These findings expand our understanding of the structural pharmacology of TRPC5 and provide a framework for investigating calcium regulation in TRPC channels.