Structures of the calcium-activated, non-selective cation channel TRPM4

Abstract

TRPM4 is a calcium-activated, phosphatidylinositol bisphosphate (PtdInsP2) modulated, non-selective cation channel, and belongs to the family of melastatin-related transient receptor potential (TRPM) channels. Here we present the cryo-EM structures of the mouse TRPM4 channel with and without ATP. TRPM4 consists of multiple transmembrane and cytosolic domains, which assemble into a three-tiered architecture. The N-terminal nucleotide binding domain (NBD) and the C-terminal coiled coil participate in the tetrameric assembly of the channel; ATP binds at NBD and inhibits channel activity. TRPM4 has an exceptionally wide filter but is only permeable to monovalent cations; filter residue Gln973 is essential in defining monovalent selectivity. S1-S4 domain and post-S6 TRP domain form the central gating apparatus that likely house the Ca2+ and PtdInsP2 binding sites. These structures provide an essential starting point for elucidating the complex gating mechanisms of TRPM4 and also reveal the molecular architecture of the TRPM family for the first time.

Mutations in the voltage‐sensing domain affect the alternative ion permeation pathway in the TRPM3 channel

“…B , homology model of the transmembrane region of TRPM3 (based on the cryo‐EM structure of TRPM4 (PDB: 6bco; Guo et al . ) depicting S1–S6 and indicating the four gating charge positions (R1–R4) in S4 as shown in A . Residues investigated in this study are shown in yellow stick representation.…”

“…As template, a TRPM4 cryo‐EM structure (PDB: 6bco; Guo et al . ) was used that has 31% sequence identity to TRPM3 in the modelled region. The generated model has a QMEAN score of −3.67, indicating acceptable overall quality (Benkert et al .…”

“…Yellow background indicates matched amino acids, blue background indicates amino acids belonging to similar subgroups. B, homology model of the transmembrane region of TRPM3 (based on the cryo-EM structure of TRPM4 (PDB: 6bco; Guo et al 2017) depicting S1-S6 and indicating the four gating charge positions (R1-R4) in S4 as shown in A. Residues investigated in this study are shown in yellow stick representation. Residues functionally important in mediating the alternative current in TRPM3 are underlined.…”

Cryo-EM for Small Molecules Discovery, Design, Understanding, and Application

“…This target validation step may be accomplished by generating just one or two structures, for example one of the target alone, and one in complex with its natural substrate or other modulators. In many cases, if the conformational differences between the various states are large enough, even medium to low resolution structures can be extremely useful in understanding the mechanism or identifying binding sites (Gao et al, 2016) (Guo et al, 2017b) (Meyerson et al, 2014). Early on in the project, structure determination can take a few months to a year, and still provide enough novel information to be useful.…”

The oncogenic roles of TRPM ion channels in cancer

“…Taken together, the existing evidence suggests that TRPM4 overexpression is associated with tumor progression and aggressiveness, although further studies are required to establish this, particularly in B-cell malignancies.Recently, the atomic-level structure of TRPM4 was revealed through cryo-EM by four independent groups. The transmembrane domain of TRPM4 contains a Ca 2+ binding site, and ATP is capable of binding its N-terminal nucleotide-binding domain (NBD), subsequently inhibiting TRPM4 activity(Autzen et al, 2018;Duan et al, 2018b;Guo et al, 2017; Winkler, Huang, Sun, Du, & Lu, 2017). These detailed atomic-level maps of TRPM4 are required to facilitate future development of additional specific TRPM4 inhibitors that might act through selectively obstructing its Ca 2+ -activation binding site or induce TRPM4 inhibition through NBD binding, providing expanded avenues to target TRPM4 in relevant diseases including cancer.…”