Animals use nervous systems to sense and respond to their environment. Yet single-celled organisms can also detect cues to execute diverse behaviors, suggesting that core components for animal sensation predate multicellularity and nervous systems. Here, we report that choanoflagellates, the closest living animal relatives, use an ancient sensory receptor family to detect bacterial prey. These receptors are related to transient receptor potential ion channels but are distinguished by WD40 domains, defining TRPW. TRPW1 detects specific bacterial lipids to modulate flagellar beating, providing a mechanism for attraction towards prey. TRPW emerged in early eukaryotes and reveals ancestral architectural and ligand-binding features that predate animal somatosensory receptors. In multicellular choanoflagellates, TRPW1 elicits collective responses, linking bacterial ecology to the evolution of receptors, sensory organelles, and multicellular life.

AMPA-subtype ionotropic glutamate receptors (AMPARs) mediate the fast component of excitatory neurotransmission. They govern synaptic plasticity that underlies learning and memory, while their dysregulation is implicated in numerous neurological disorders. The functional diversity of AMPARs arises from variations in their subunit composition and also their association with auxiliary subunits. While multiple structures of homomeric AMPARs have been reported, structural information for the heteromeric core - particularly in the absence of auxiliary subunits, which would serve as a functional and structural baseline - has been limited. Here, we report cryo-electron microscopy structures of GluA1/A2, the most abundant AMPAR di-heteromer in the brain, in the closed, open, and desensitized states. Using molecular dynamics (MD) simulations and cross-correlating structural and functional information, we find that auxiliary subunits increase the diameter of channel pore, which corresponds to larger conductance. Likewise, we find that recovery from desensitization slows with greater disruption of two-fold rotational symmetry of the ligand-binding domain dimer in the desensitized state. Both receptor activation and desensitization vary with the type and number of associated auxiliary proteins. These structures offer a foundation for uncovering how auxiliary subunits reshape structural asymmetry and functional plasticity in heterotetrameric AMPARs.

Transient receptor potential vanilloid type-1 (TRPV1) channel is a polymodal receptor involved in pain perception and neuronal signalling that represents a promising target for the development of analgesics and neuroprotective agents. In this study we implement a combination of computational techniques and targeted design of chemical libraries to discover benzothiophene-substituted TRPV1 agonists with high affinity and efficacy toward TRPV1. In vitro functional experiments show that prolonged or repeated exposure to these compounds induce calcium-dependent desensitization of TRPV1, making it insensitive to noxious stimuli. We solve a cryo-electron microscopy (cryo-EM) structure of human TRPV1 (hTRPV1) in complex with the most promising benzothiophene-substituted agonist MSP20. The structure reveals molecular details of MSP20 binding to the vanilloid site and a desensitized conformation of hTRPV1, characterized by the closed ion channel pore, α-helical C-terminus and distinct behaviour of annular lipids. Our in vivo experiments demonstrate that MSP20 exhibits robust and long-lasting antinociceptive activity with ex-vivo neuroprotective effects, supporting the perspective of benzothiophene-substituted vanilloids as future analgesics.

Polyamines are organic cations that are present at sub-millimolar concentrations in the cytoplasm and extracellular fluids and serve as versatile modulators of TRP channels, fine-tuning their functions in physiological and pathological contexts, including pain, inflammation and cancer. Despite extensive functional studies, the structural basis by which polyamines regulate TRP channels remains unclear. Here, we combine calcium imaging, electrophysiology, cryo-electron microscopy, mutagenesis and molecular dynamics simulations to study regulation of human TRPV6 by polyamine spermine. Our functional experiments demonstrate voltage-dependent block of TRPV6-mediated currents by spermine. Cryo-electron microscopy reveals that spermine binds in the open pore of TRPV6, extending along the pore axis through the selectivity filter and central cavity. Mutagenesis and molecular dynamics simulations confirm the main binding site of spermine in the selectivity filter and suggest a stepwise molecular mechanism of channel block that includes two more binding sites in the pore transiently occupied by spermine. Our findings enrich the knowledge about TRPV6 regulation by endogenous factors and provide details of the ion channel blocking mechanism that can be explored for inhibition of this channel in disease conditions.

Mutations in TRPV3, a temperature-sensitive ion channel critical for skin physiology, cause severe genodermatosis called Olmsted syndrome (OS). Here we integrate single-channel recordings and cryo-EM to characterize five OS mutants. All exhibit reduced temperature sensitivity in the temperature range relevant to normal skin physiology and disrupt structural elements stabilizing non-conducting states, including vanilloid lipid coordination and S4-S5 linker-TRP helix contacts. Despite shared gain-of-function phenotype, the mutations cause different distributions of the TRPV3 closed, open, and inactivated states. One mutation expands the conformational ensemble with noncanonical two-fold-symmetrical states featuring dramatic domain swapping. Our findings highlight conserved TRP channel gating mechanisms and suggest that OS mutations alter TRPV3 function by triggering the conformational wave that mediates gating in wild-type channels. These insights establish a framework to decode genotype-structure-function relationships in TRP channelopathies and guide future therapeutic strategies.

AMPA receptors (AMPARs) mediate fast excitatory neurotransmission. Gating of AMPARs starts with agonist binding and transition into a non-conducting pre-active state, followed by transition into conducting open or non-conducting desensitized states. While the terminal apo, open and desensitized states have been structurally characterized, the intermediate pre-active state has remained an enigma. Compared to full agonist glutamate, partial agonists reduce the maximal occupancy of the open state and increase the probability of the pre-active state occurrence. Here we use different partial agonists and time-resolved cryo-electron microscopy (cryo-EM) to capture a structural ensemble of GluA2-γ2 AMPAR complexes in the closed apo, pre-active, open and desensitized states. Binding of partial agonists to the ligand-binding domain (LBD) results in different extents of LBD clamshell closure, with closures exceeding a threshold of ~17° resulting in the open and desensitized states and smaller closures stabilizing the pre-active state. The pre-active state has a distinct gate conformation intermediate between the other two discrete states, completely open and closed. Combined with single-channel current recordings and molecular dynamics simulations, our structural results reveal the complete gating pathway of AMPARs and shed light on the molecular mechanisms of partial agonism and pre-activation.

High-fidelity fast excitatory neurotransmission in the mammalian central nervous system is conducted by the AMPA receptor (AMPAR) subfamily of ionotropic glutamate receptors. AMPARs exist as complexes of the pore-lining α subunits GluA1-4 and a number of auxiliary subunits shaping their functional properties. The first discovered family of auxiliary subunits comprises the transmembrane AMPAR regulatory proteins (TARPs). Together with germ cell-specific gene 1-like (GSG1L), they belong to the PMP-22/EMP/MP20/claudin superfamily sharing substantial sequence homology and a 4-transmembrane domain (4-TMD) topology. Here, we identify the claudin Cldn24 as a novel AMPAR auxiliary subunit in cerebellar granule cells (CGCs). Specifically accelerating the recovery of desensitized receptors, Cldn24 counterbalances gating modulation of GluA by TARP-γ2 and GSG1L in CGCs and hence enables fast reactivation of native receptors. These features substantially expand the tuning properties of hitherto known AMPAR auxiliary subunits and render Cldn24 a powerful enhancer of AMPAR fidelity.

AMPA receptors (AMPARs) facilitate excitatory neurotransmission and are implicated in neurological and neuropsychiatric disorders. Binding of the neurotransmitter glutamate triggers AMPAR activation, which is modulated by potentiating and inhibitory auxiliary subunits. While modulation by potentiating auxiliary subunits has been studied extensively, activation involving inhibitory subunits has not been examined. Here, we present structures of the activated GluA2 AMPAR alone and in complex with inhibitory subunits GSG1L or γ5. Our results suggest that gating kinetics strongly depend on auxiliary subunit identity, while pore size and conductance do not. We find that receptor deactivation becomes slower if an auxiliary subunit promotes tightening of the interface between two ligand-binding domain dimers during activation. In addition, we functionally characterize the effects of epilepsy-associated disease mutations on AMPAR activation and desensitization kinetics, displaying strong dependence on the type of bound auxiliary subunit. Modulation by auxiliary subunits therefore has to be considered when designing AMPAR-targeting therapeutics. AMPA receptors mediate the majority of excitatory neurotransmission. Here, the authors report structural and functional regulation of GluA2 AMPA receptor by inhibitory auxiliary subunits GSG1L and TARP γ5 and by epilepsy-associated disease mutations.

Ionotropic glutamate receptors (iGluRs) are crucial for fast excitatory neurotransmission in the mammalian central nervous system (CNS). Kainate receptors (KARs), a subclass of iGluRs, are tetrameric, ligand-gated ion channels that play key modulatory roles at both pre- and post-synaptic sites within neuronal circuits and in the regulation of synaptic plasticity. KARs are composed of GluK1-GluK5 subunits, with subunits GluK1-GluK3 forming functional homo- and heteromeric channels, while GluK4-GluK5 assemble as obligate heteromers, partnering with subunits GluK1-GluK3. Over the past two decades, numerous homomeric and heteromeric structures of isolated domains and the full-length receptor have been solved in various functional states, providing detailed descriptions of functional mechanisms, thereby addressing several longstanding questions in the field of KAR biology. These studies revealed overall structural similarity of KARs with other iGluRs, particularly AMPA receptors in the closed and activated states, and the agonist-bound non-conducting state adopting a conformation which is different from other iGluRs. This review highlights recent structural insights into gating and pharmacological regulation of KARs, offering deeper understanding of their roles in synaptic transmission and neuronal signaling.

Kainate receptors (KARs) are tetrameric, ligand-gated ion channels of the ionotropic glutamate receptor family that mediate excitatory neurotransmission and modulate neuronal circuits and synaptic plasticity during development of the central nervous system. KARs are implicated in psychiatric and neurological diseases and represent a target of therapeutic intervention. Native KARs form complexes with neuropilin and tolloid-like auxiliary subunits (Neto1 and Neto2), which modulate their function, trafficking and synaptic localization. Here we present structures of rat GluK2 KAR in the apo closed state and in the open states activated by agonist kainate and positive allosteric modulator BPAM344, solved in the presence and absence of Neto2 using time-resolved cryo-electron microscopy. While the binding of Neto2 does not change the behavior of individual or dimeric ligand-binding domains (LBDs) or the ion channel, it prevents tightening of the interface between two LBD dimers during activation and slows the kinetics of deactivation. Our structures illuminate the mechanism of KAR activation and its modulation by Neto2.

TRPV6 is a Ca2+ selective channel that mediates calcium uptake in the gut and contributes to the development and progression of human cancers. TRPV6 is represented by the ancestral and derived haplotypes that differ by three non-synonymous polymorphisms, located in the N-terminal ankyrin repeat domain (C157R), S1-S2 extracellular loop (M378V), and C-terminus (M681T). The ancestral and derived haplotypes were proposed to serve as genomic factors causing a different outcome for cancer patients of African ancestry. We solved cryoelectron microscopy (cryo-EM) structures of ancestral and derived TRPV6 in the open and calmodulin (CaM)-bound inactivated states. Neither state shows substantial structural differences caused by the non-synonymous polymorphisms. Functional properties assessed by electrophysiological recordings and Ca2+ uptake measurements, and water and ion permeation evaluated by molecular modeling also appear similar between the haplotypes. Therefore, ancestral and derived TRPV6 have similar structure and function, implying that other factors are responsible for the differences in susceptibility to cancer.

The Transient Receptor Potential Vanilloid 1 (TRPV1) ion channel is expressed in primary nociceptive afferents, which participate in processes such as pain and inflammation. Considerable efforts have been directed toward finding inhibitors of TRPV1 and understanding the molecular details of their interactions with this channel. α-humulene (AH) is a sesquiterpene derived from plants such as hops and other members of Cannabaceae family, with a long history of popular use as an analgesic and anti-inflammatory. Using a combination of behavioral assays, electrophysiology, site-directed mutagenesis, cryo-EM, and molecular dynamics simulations, we show that AH inhibits TRPV1-related pain responses and currents by interacting with a region composed of the S2, S2-S3 linker, and S3 transmembrane segments and stabilizing the closed conformation of the channel. The interaction of ligands in this region of the TRPV1 channel has not been previously described and the results of the present study highlight that it may constitute part of a negative regulatory region. These findings allow us to understand the molecular basis by which substances such as some sesquiterpenes, abundantly found in medicinal plants used by humans for hundreds of years, reduce pain. Pain management can include the use of opioids, which results in hepatic and renal damage and possible addiction. Our study offers insight into a poorly understood group of compounds that could be used as scaffold to produce novel nonopioid analgesic therapies and clarifies the molecular mechanisms that underlie the effects of these analgesic molecules.

TRPV6 is a member of the vanilloid subfamily of transient receptor potential channels, which serves as the master regulator of Ca2+ homeostasis. TRPV6 functions as a constitutively active Ca2+ channel, and emerging evidence indicates that its overactivity underpins the progression of several human diseases, including cancer. Hence, there is a pressing need to identify TRPV6 inhibitors in conjunction with a deep mechanistic understanding of their effects on the channel activity. Here we combine cryo-electron microscopy, mutagenesis, electrophysiology and molecular dynamics modeling to decipher the molecular mechanism of TRPV6 inhibition by intracellular Mg2+. Mg2+ appears to bind to four, one per subunit, sites around the intracellular entrance to the TRPV6 channel pore, contributed by the negatively charged residues, D489 in the transmembrane helix S5 and D580 in S6. When bound to the D489-D580 site, Mg2+ prevents the α-to-π transition in the middle of S6 that accompanies channel opening, thus maintaining S6 entirely α-helical, locking the channel in the closed state and inhibiting TRPV6-mediated currents. Further exploration of this inhibitory mechanism may help to develop future strategies for the treatment of TRPV6-associated diseases.

Designing safe and effective oligonucleotide (ON) therapeutics requires thorough understanding of structural-activity relationship (SAR) with the intended on-target(s) as well as the unintended off-target(s). Despite encouraging pharmacodynamic activity in a Phase 1b study, development of the first-generation anti-miR-17 ON RGLS4326 for the treatment of autosomal dominant polycystic kidney disease was discontinued due to dose-limiting central nervous system (CNS)-related toxicity observed in nonclinical chronic toxicity studies. Here, we provide SAR evidence that the nucleobase guanine at the 3'-terminus of RGLS4326 drives an unexpected off-target aptamer-like direct interaction with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), thereby causing CNS toxicity. By replacing the 3'-terminal guanine with adenine, we discover the next-generation anti-miR-17 RGLS8429 that is devoid of off-target AMPAR interaction and CNS toxicity while preserving the potency against the on-target miR-17. Here, we show a way to avoid off-target CNS effects and, more importantly, data that support the clinical development of RGLS8429.

The endothelium in brain microcirculation functions not only as a barrier but also as a signal transduction component within a system that regulates multiple vascular processes, including muscle tone, permeability, and structural integrity. The control of local blood flow is vital to ensure adequate oxygen and nutrient supply, efficient removal of catabolic waste, and the maintenance of proper brain cell function. The role of endothelial glutamate receptors in brain pathology is an emerging area of research, particularly important for understanding how these receptors contribute to neurological diseases and disorders. Endothelial cells (ECs), which are considered active players in maintaining brain homeostasis, express glutamate receptors on their surface. Activation of these receptors can trigger a cascade of signaling events, including synthesis of nitric oxide (NO) and proinflammatory molecules. N-Methyl-D-Aspartate receptors (NMDARs) play a significant role in functional hyperemia, also known as neurovascular coupling (NVC), which is essential for maintaining the energy balance in brain cells. Growing evidence suggests that disturbance of this balance is implicated in several neurological diseases, such as Alzheimer’s disease, stroke, and traumatic brain injury (TBI), where endothelial dysfunction may impair blood flow regulation, contributing to further neuronal damage and cognitive decline. This review focuses on the glutamate receptor-mediated alterations in endothelial permeability and the prevention of the brain pathology through direct modulation of these receptors. Notably, the metabotropic glutamate receptor mGluR1, along with NMDARs, may cause deleterious effects in brain ischemia, as their activation increases the permeability of the vessel wall. Stimulation of NMDARs may also lead to ferroptosis in ECs. EC dysfunction results in significant blood-brain barrier (BBB) disruption, allowing infiltration by inflammatory cells and the accumulation in brain of pathological proteins, such as amyloid-beta (Aβ) or autoantibodies. This contributes to neuronal dystrophy and apoptosis, as seen in Alzheimer’s disease and autoimmune encephalopathy. Activated ECs generate proinflammatory mediators that attract leukocytes and sustain the neuroinflammatory response. Infiltrating peripheral white blood cells are key contributors to inflammatory damage following TBI. Regulation of ECs through glutamate receptors therefore represents a promising therapeutic strategy for treatment of neurodegenerative diseases, as well as ischemic and traumatic brain injuries.

Fast excitatory neurotransmission in the mammalian central nervous system is mediated primarily by AMPA-subtype ionotropic glutamate receptors (iGluRs) that are activated by agonist glutamate. Several auxiliary subunits, including TARPs and CNIHs, associate with the transmembrane domain region of the receptor and modulate the kinetics and trafficking of the receptor. In this study, we present cryo-EM structures of GluA2 AMPAR complexes with inhibitory TARP-γ5 and potentiating cornichon-2 (CNIH2) auxiliary subunits in closed and desensitized states bound to antiepileptic drug perampanel and polyamine as channel blocker.