Structural and functional analyses of a GPCR-inhibited ion channel TRPM3
Chen Zhao1, Roderick MacKinnon1
1Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, the Rockefeller University, New York, NY 10065, United States.
Abstract:
G-protein coupled receptors (GPCRs) govern the physiological response to stimuli by modulating the activity of downstream effectors, including ion channels. TRPM3 is an ion channel inhibited by GPCRs through direct interaction with G protein (Gβγ) released upon their activation. This GPCR-TRPM3 signaling pathway contributes to the analgesic effect of morphine. Here, we characterized Gβγ inhibition of TRPM3 using electrophysiology and single particle cryo-electron microscopy (cryo-EM). From electrophysiology, we obtained a half inhibition constant (IC50) of ∼240 nM. Using cryo-EM, we determined structures of mouse TRPM3 expressed in human cells with and without Gβγ and with and without PIP2, a lipid required for TRPM3 activity, at resolutions of 2.7-4.7 Å. Gβγ-TRPM3 interfaces vary depending on PIP2 occupancy; however, in all cases, Gβγ appears loosely attached to TRPM3. The IC50 in electrophysiology experiments raises the possibility that additional unknown factors may stabilize the TRPM3-Gβγ complex.
Related Concept Videos
Ligand-Gated Ion Channel Receptor: Gating Mechanism
Mechanically-gated Ion Channels
Non-gated Ion Channels
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism....
Voltage-gated Ion Channels
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several...
Ligand-gated Ion Channels
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
G-Protein Gated Ion Channels
Sensory...


