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Combined single-molecule spectroscopy, hydrogen–deuterium exchange and molecular dynamics approaches reveal that agonist activation of metabotropic glutamate receptors entails population of several intermediary states before G protein coupling.

Voltage-sensing phosphatases dephosphorylate PIPs upon membrane depolarization. Here, authors provide a model for a dynamic assembly by which the voltage sensor controls the catalytic site with the aid of the N-terminus.

In vitro studies of neuronal function have mainly been limited to two-dimensional networks of cultured neurons. Use of transparent colloids as a moveable support for neuronal growth allows user-guided construction of optically accessible three-dimensional networks whose function can be manipulated and measured.

Super-resolution quantal imaging relates transmission at excitatory synapses to presynaptic molecular composition. The authors find that evoked transmission varies greatly between synapses and is uncorrelated and physically separate from spontaneous transmission, and identify responsible presynaptic proteins.

The molecular basis of functional diversity between obligatorily dimeric mGluRs is not understood. The authors show that functional differences typically attributed to differences in the agonist binding pocket emerge from differences between homomeric and heteromeric Group II and III Gi-coupled mGluRs in dimerization interface interactions.

Voltage-gated K⁺ channels assemble into complexes with Kvβs, a group of aldoketoreductases. The Kvβs regulate channel gating and localization, and voltage-dependent changes in the channel regulate AKR activity. Pan and colleagues now propose a new type of modulation of this complex. Cortisone disrupts the complex and relieves channel inactivation—which should reduce neuronal excitability.

The activity of the voltage-sensitive phosphatase from Ciona intestinalis, VSP, towards PIP3 and PIP2 is dictated by the sequential switching between two active conformations of the phosphatase domain that is also correlated with conformational changes in the voltage sensor.

N-Methyl-D-aspartate receptors (NMDARs) activation involves closure of the GluN1 and GluN2 subunit ligand binding domains, which is regulated allosterically by the amino-terminal domain (ATD). Here, smFRET, used to monitor conformational rearrangements of the NMDAR ATD, reveals that glutamate binding to GluN2 subunits elicits two identical, sequential steps of ATD dimer separation that are regulated by protons.

Glutamate is the major excitatory neurotransmitter in the mammalian nervous system. Here, a glutamate receptor is reported that has properties intermediate to those of bacterial and eukaryotic glutamate-gated ion channels, suggesting a link in the evolution of ionotropic glutamate receptors.

Voltage- and patch-clamp fluorometry reveal structural rearrangements of the S1 helix and its surroundings that are important for gating of the Hv1 voltage-gated proton channel.

Metabotropic glutamate receptors (mGluRs) are dimeric G-protein–coupled receptors that operate at neural synapses. Here authors use FRET assays in live cells to monitor mGluR2/7’s activation and reveal how heterodimerization can alter the glutamate response of an mGluR.

Activating the spared neurons downstream of rods and cones is a potential therapeutic approach for retinal degeneration, but has been limited by the characteristics of the opsins available. Here, the authors use medium wavelength cone opsin which has faster kinetics than others and show that it resolves some of these difficulties in a mouse model.

A fluorescence resonance energy transfer biosensor called Rango enables examination of the Ran–importin-β system in cells. Small changes in RanGTP concentration tip the balance between positive and negative mitotic regulators, thereby promoting spindle assembly and function.

Functionally coupled motions between the voltage-sensing and the phosphatidylinositol phosphatase domains of the sea squirt protein Ci-VSP are mediated by PtdIns(4,5)P₂ binding to the segment linking these domains, as shown by electrophysiology and voltage clamp fluorometry.

Adaptive optics (AO) corrects sample aberrations and allows high spatial resolution at depth in vivo. Here the authors report an AO method for Bessel focus; they apply AO Bessel focus scanning fluorescence microscopy to volumetric imaging and measure synaptic calcium and glutamate activity in vivo.

The photoactivatable calcium sensors reported in this paper allow simultaneous highlighting of cellular morphology and recording of calcium activity, which is demonstrated in neuronal cultures, in Drosophila and in zebrafish.

The voltage-sensing domain of Ci-VSP regulates the enzymatic activity of its PTEN-like phosphatase domain. New structural and functional data identify a gating loop that controls access to the enzyme's active site and is coupled to voltage sensor movements.

The voltage-gated proton channel Hv1 forms a dimer, but each monomer contains a voltage sensor domain that forms a pore for proton conduction. Now functional work using voltage clamp fluorometry, current recording and modeling reveals that the 2 pores are gated in a cooperative manner.

We propose a model for a sequential, multistep activation mechanism of metabotropic glutamate receptor subtype 5, including a series of structures in lipid nanodiscs, from inactive to fully active, with agonist-bound intermediate states.

Generalized phase contrast and temporal focusing are combined to shape two-photon excitation patterns that elicit large photocurrents in ChR2-expressing neurons in culture and slices. This method allows precise aiming of the stimulating light at single neuronal processes, neurons or groups of neurons and can elicit simultaneous excitation of multiple cells using optogenetics.

A tethered ligand approach reveals that four ligand molecules are required for full desensitization of tetrameric iGluR (glutamate receptor) channels. When fewer ligands are bound, which might be the case during synaptic transmission, desensitization is incomplete or non-existent.

To restore sight after retinal degeneration, one approach is to express light-sensitive proteins in remaining cells. Here the authors combine a light-sensitive engineered G protein-coupled receptor and ion channels to restore ON and OFF responses as well as superior visual pattern discrimination.

Polycystic kidney disease family proteins form heteromeric complexes with transient receptor potential channel subunits of the TRPP subfamily. Yu and colleagues find that the polycystic kidney disease protein, PKD1L3, is an ion channel pore-forming subunit in the acid-sensing PKD1L3/TRPP3 complex.

Using cryo-EM structures, single-molecule fluorescence and electrophysiological studies, Kern et al. show how LRRC8A:C volume-regulated channels assemble into heteromers and use pore-bound lipids to block conduction in a closed state.

smFRET is used to probe the activation mechanism of two full-length mammalian glutamate receptors, revealing that the extracellular ligand-binding domains of these G-protein-coupled receptors interconvert between three confirmations (resting, activated and a short-lived intermediate state), and that the efficacy of an orthosteric agonist correlates with the degree of occupancy of the active state.

Copper contributes to regulating zebrafish rest–activity cycles through the locus coeruleus system by modulating the biosynthesis of norepinephrine; brain copper deficiency leads to lower levels of both synaptic norepinephrine and daytime activity.

A photoswitchable analog of spingosine-1-phosphate (S1P) that allows for modulation of the action of this bioactive lipid exhibits prolonged metabolic stability compared to S1P, activates S1P receptors in cells and mediates nociception in mice.

Organic cation transporters are important drug transporters that influence therapeutic outcomes. Here, the authors find that these transporters are regulated by tyrosine phosphorylation and propose that tyrosine kinase inhibitors can influence drug transporter function through post-translational mechanisms.

In vertebrates, the excitatory synaptic drive for inducing spinal central pattern generators (CPGs) — which are responsible for generating rhythmic movements — can originate from either supraspinal glutamatergic inputs or from within the spinal cord. A spinal input to the CPG is now identified using a combination of intersectional gene expression and optogenetics in zebrafish larvae; the results reveal that during early development Kolmer–Agduhr cells provide a positive drive to the spinal CPG for spontaneous locomotion.

This paper reports the development of a K⁺-selective glutamate receptor, HyLighter, that reversibly inhibits neuronal activity in response to light. The low light requirement and bi-stability of HyLighter could be useful for studying neural circuitry.

This Technical Report describes light-activatable metabotropic glutamate receptors based on synthetic photoswitchable tethered ligands, and demonstrates optogenetic control of G protein–coupled receptor activity in neurons in vivo and ex vivo.

This paper reports an in vivo imaging method that monitors real-time synaptic transmission simultaneously at many release sites with quantal resolution. The authors demonstrate the utility of this technique by using it to study the glutamatergic system of Drosophila larval NMJ.