Structures of the TRPM5 channel elucidate mechanisms of activation and inhibition

Nat Struct Mol Biol. 2021 Jul;28(7):604-613. doi: 10.1038/s41594-021-00607-4. Epub 2021 Jun 24.


The Ca2+-activated TRPM5 channel plays essential roles in taste perception and insulin secretion. However, the mechanism by which Ca2+ regulates TRPM5 activity remains elusive. We report cryo-EM structures of the zebrafish TRPM5 in an apo closed state, a Ca2+-bound open state, and an antagonist-bound inhibited state. We define two novel ligand binding sites: a Ca2+ site (CaICD) in the intracellular domain and an antagonist site in the transmembrane domain (TMD). The CaICD site is unique to TRPM5 and has two roles: modulating the voltage dependence and promoting Ca2+ binding to the CaTMD site, which is conserved throughout TRPM channels. Conformational changes initialized from both Ca2+ sites cooperatively open the ion-conducting pore. The antagonist NDNA wedges into the space between the S1-S4 domain and pore domain, stabilizing the transmembrane domain in an apo-like closed state. Our results lay the foundation for understanding the voltage-dependent TRPM channels and developing new therapeutic agents.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / physiology
  • Calcium / metabolism
  • Cell Membrane / physiology*
  • Cryoelectron Microscopy
  • Enzyme Activation
  • Humans
  • Patch-Clamp Techniques
  • Protein Conformation
  • TRPM Cation Channels / antagonists & inhibitors
  • TRPM Cation Channels / metabolism*
  • Zebrafish / metabolism*


  • TRPM Cation Channels
  • Calcium