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Abstract Pain therapy has remained conceptually stagnant since the opioid crisis, which highlighted the dangers of treating pain with opioids. An alternative addiction-free strategy to conventional painkiller-based treatment is targeting receptors at the origin of the pain pathway, such as transient receptor potential (TRP) ion channels. Thus, a founding member of the vanilloid subfamily of TRP channels, TRPV1, represents one of the most sought-after pain therapy targets. The need for selective TRPV1 inhibitors extends beyond pain treatment, to other diseases associated with this channel, including psychiatric disorders. Here we report the cryo-electron microscopy structures of human TRPV1 in the apo state and in complex with the TRPV1-specific nanomolar-affinity analgesic antagonist SB-366791. SB-366791 binds to the vanilloid site and acts as an allosteric hTRPV1 inhibitor. SB-366791 binding site is supported by mutagenesis combined with electrophysiological recordings and can be further explored to design new drugs targeting TRPV1 in disease conditions. 

Intrinsically disordered regions within human proteins play critical roles in cellular information processing, including signaling, transcription, stress response, DNA repair, genome organization, and RNA processing. Here, we summarize current challenges in the field and propose cutting-edge approaches to address them in normal physiology and disease, with a focus on cancer. 

Abstract Ionotropic glutamate receptors (iGluRs) are tetrameric ligand-gated ion channels that open their pores in response to binding of the agonist glutamate 1–3 . An ionic current through a single iGluR channel shows up to four discrete conductance levels (O1–O4) 4–6 . Higher conductance levels have been associated with an increased number of agonist molecules bound to four individual ligand-binding domains (LBDs) 6–10 . Here we determine structures of a synaptic complex of AMPA-subtype iGluR and the auxiliary subunit γ2 in non-desensitizing conditions with various occupancy of the LBDs by glutamate. We show that glutamate binds to LBDs of subunits B and D only after it is already bound to at least the same number of LBDs that belong to subunits A and C. Our structures combined with single-channel recordings, molecular dynamics simulations and machine-learning analysis suggest that channel opening requires agonist binding to at least two LBDs. Conversely, agonist binding to all four LBDs does not guarantee maximal channel conductance and favours subconductance states O1 and O2, with O3 and O4 being rare and not captured structurally. The lack of subunit independence and low efficiency coupling of glutamate binding to channel opening underlie the gating of synaptic complexes to submaximal conductance levels, which provide a potential for upregulation of synaptic activity. 

Abstract Transient receptor potential (TRP) channels are polymodal molecular sensors involved in numerous physiological processes and implicated in a variety of human diseases. Several structures of the founding member of the TRP channel family, TRPV1, are available, all of which were determined for the protein missing the N- and C-termini and the extracellular S5-P-loop. Here, we present structures of the full-length thirteen-lined ground squirrel TRPV1 solved by cryo-EM. Our structures resolve the extracellular cap domain formed by the S5-P-loops and the C-terminus that wraps around the three-stranded β-sheet connecting elements of the TRPV1 intracellular skirt. The cap domain forms a dome above the pore’s extracellular entrance, with four portals leading to the ion conductance pathway. Deletion of the cap increases the TRPV1 average conductance, reduces the open probability and affects ion selectivity. Our data show that both the termini and the cap domain are critical determinants of TRPV1 function. 

Fast excitatory neurotransmission is mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of ionotropic glutamate receptor (AMPAR). AMPARs initiate depolarization of the postsynaptic neuron by allowing cations to enter through their ion channel pores in response to binding of the neurotransmitter glutamate. AMPAR function is dramatically affected by auxiliary subunits, which are regulatory proteins that form various complexes with AMPARs throughout the brain. The most well-studied auxiliary subunits are the transmembrane AMPAR regulatory proteins (TARPs), which alter the assembly, trafficking, localization, kinetics, and pharmacology of AMPARs. Recent structural and functional studies of TARPs and the TARP-fold germ cell-specific gene 1-like (GSG1L) subunit have provided important glimpses into how auxiliary subunits regulate the function of synaptic complexes. In this review, we put these recent structures in the context of new functional findings in order to gain insight into the determinants of AMPAR regulation by TARPs. We thus reveal why TARPs display a broad range of effects despite their conserved modular architecture. 

Background and PurposeAMPA receptors, which shape excitatory postsynaptic currents and are directly involved in overactivation of synaptic function during seizures, represent a well‐accepted target for anti‐epileptic drugs. Trans‐4‐butylcyclohexane carboxylic acid (4‐BCCA) has emerged as a new promising anti‐epileptic drug in several in vitro and in vivo seizure models, but the mechanism of its action remained unknown. The purpose of this study is to characterize structure and dynamics of 4‐BCCA interaction with AMPA receptors. Experimental ApproachWe studied the molecular mechanism of AMPA receptor inhibition by 4‐BCCA using a combination of X‐ray crystallography, mutagenesis, electrophysiological assays, and molecular dynamics simulations. Key ResultsWe identified 4‐BCCA binding sites in the transmembrane domain (TMD) of AMPA receptor, at the lateral portals formed by transmembrane segments M1–M4. At this binding site, 4‐BCCA is very dynamic, assumes multiple poses, and can enter the ion channel pore. Conclusion and Implications4‐BCCA represents a low‐affinity inhibitor of AMPA receptors that acts at the TMD sites distinct from non‐competitive inhibitors, such as the anti‐epileptic drug perampanel and the ion channel blockers. Further studies might examine the possibsility of synergistic use of these inhibitors in treatment of epilepsy and a wide range of neurological disorders and gliomas. LINKED ARTICLESThis article is part of a themed issue on Structure Guided Pharmacology of Membrane Proteins (BJP 75th Anniversary). To view the other articles in this section visithttp://onlinelibrary.wiley.com/doi/10.1111/bph.v179.14/issuetoc