Structures of the M1 and M2 muscarinic acetylcholine receptor/G-protein complexes

Abstract

Muscarinic acetylcholine receptors are G protein–coupled receptors that respond to acetylcholine and play important signaling roles in the nervous system. There are five muscarinic receptor subtypes (M1R to M5R), which, despite sharing a high degree of sequence identity in the transmembrane region, couple to different heterotrimeric GTP-binding proteins (G proteins) to transmit signals. M1R, M3R, and M5R couple to the Gq/11 family, whereas M2R and M4R couple to the Gi/o family. Here, we present and compare the cryo–electron microscopy structures of M1R in complex with G11 and M2R in complex with GoA. The M1R-G11 complex exhibits distinct features, including an extended transmembrane helix 5 and carboxyl-terminal receptor tail that interacts with G protein. Detailed analysis of these structures provides a framework for understanding the molecular determinants of G-protein coupling selectivity.

Novel M2‐selective, Gi‐biased agonists of muscarinic acetylcholine receptors

“…Comparison of cryo‐EM structures 6OIJ and 6KOI of G‐protein complexes of iperoxo bound receptors in an active conformation (Maeda, Qu, Robertson, Skiniotis, & Kobilka, ) shows that the outward tilt of TM6 and intracellular shift of TM5 are greater in M 1 –G 11 complex than M 2 –G oA complex (Figure S7). The distance between TM3 and TM6 is greater at M 1 (16.9 Å) than at M 2 receptor (14.6 Å).…”

“…It has been shown that coupling of various GPCRs to G s G‐proteins requires a greater degree of TM6 movement than coupling to G i G‐proteins (Glukhova et al, ). Cryo–electron microscopy (cryo‐EM) structures 6OIJ and 6KOI of complexes of muscarinic receptors with G‐proteins (Maeda et al, ) further show that greater conformational change of the receptor is needed to accommodate C‐terminus of G 11 G‐protein than G oA G‐protein (Figure S7). The molecular modelling data presented here showed that agonist‐specific conformations of compounds 6A or 7A differed from agonist‐specific conformations of iperoxo or carbachol by having less effects in increasing the distance between TM5 and TM7 than that between TM3 and TM6 (Figures and S5 through S7).…”

GemSpot: A Pipeline for Robust Modeling of Ligands into CryoEM Maps

“…Icilin/Ion channel TRPM8 (PDB:6NR3, EMD:0487) 41 ; LY2119620/M2R (PDB:6OIK, EMD:20079) 38 ; Iperoxo/M2R (PDB:6OIK, EMD:20079) 38 ; Saxitoxin/Nav1.7 (PDB: 6J8G, EMD:9781) 39 ; Biculine/GABAA (PDB:6HUK, EMD:0280) 37 ; Xanax/GABAA (PDB:6HUO, EMD:0282) 37 ; Valium, GABAA (PDB:6HUP, EMD:0283) 37 ; NDI-091143/ATP Citrate Lyase (PDB:6O0H, EMD:0567) 7 ; paroxetine/serotonin transporter (PDB:6DZW, EMD:8941) 40 ;…”

“…Using GlideEM we were able to identify candidate poses in this resolution range with cross correlations that were comparable to the deposited poses for all of the structures that we studied. For GABAA in complex with three different ligands 37 , the M2 muscarinic acetylcholine receptor in complex with two different ligands 38 , the sodium channel Nav1.7 with one ligand 39 , ATP citrate lyase with one ligand 7 , and the serotonin transporter with two different ligands 40 the poses we identified with GlideEM largely agreed with what was deposited in the PDB ( Supplementary Fig. 7) (although it should be noted that for the deposited structures of the M2 receptor and serotonin transporter the ligands were docked with the traditional version of Glide).…”

Structure of the Visual Signaling Complex between Transducin and Phosphodiesterase 6

“…Based on primary sequence similarity of the Gα subunits, heterotrimeric G proteins are divided into 4 classes: GS, Gi/o, Gq/11 and G12/13 (Simon et al, 1991). Several recent high-resolution structures of various GPCRs in complex with different G proteins have yielded important information on how this class of receptors selectively couple to and activate their signaling partners García-Nafría and Tate, 2019;Kato et al, 2019;Krishna Kumar et al, 2019;Maeda et al, 2019). By contrast, structural information about how activated Gα subunits engage and activate full-length downstream effectors are limited to a crystal structure of Gαq in a complex with phospholipase C-β3 (PLCβ3) (Lyon et al, 2013) and a recent cryoEM structure of a GαS-adenylyl cyclase 9 (AC9) complex (Qi et al, 2019).…”