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Reports from Prof. V. Tsetlin's symposium, made during the integrated Forum in Dagomys were published (2016, 4-8th of October)
Reports form the section "Signaling ion channels from the spatial structure of physiological mechanisms" organized by Prof. V. Tsetlin made during the Forum, integrated V Congress of the Russian biochemists and V Congress of Physiologists in Dagomys (4-8 October 2016), were published on the page of the Institute of Bioorganic Chemistry in the channel YouTube. Videos of the lectures in English languages were published here.
Interaction of Cys-loop ion channels with neurotoxins and endogenous modulators
V. Tsetlin, Shemyakin-Ovchinnikov Institute of bioorganic chemistry RAS, Moscow
Light in modulation ofreceptor-operated channels function
P. Brezhestovsky, Institute for Systems Neuroscience, Aix-Marseille University, Marseille, France
Pentameric ligand-gated ion channels functioning at the atomic resolution
P.J. Corringer Pasteur Institute, Channel-receptor Unit, CNRS UMR 3571, 25 rue du Docteur Roux, Paris, France
Pentameric channel-receptors, including nicotinic acetylcholine, glycine and GABAA receptors, play a key role in fast excitatory and inhibitory transmission in the nervous system and are the target of numerous therapeutic and addictive drugs. They carry several neurotransmitter binding sites which govern the opening of a transmembrane ion channel. Extensively expressed in animals, they were found in several bacteria, especially the homolog from the cyanobacteria Gloeobacter violaceus (GLIC) which functions as a proton-gated ion channel. The simplified architecture of this archaic homologue, as well as its prokaryotic origin, allowed solving its X-ray structure in two closed and one open conformation. Those static structures suggest that channel opening occurs through symmetrical quaternary twist and “blooming” motions, together with tertiary deformation, according to a global transition that couples channel opening with reorganization of the binding pockets for neurotransmitters and allosteric effectors. To investigate the dynamics of the protein, we further engineered multiple fluorescent reporters, each incorporating a bimane and a tryptophan/tyrosine, whose close contact causes fluorescence quenching. We show that proton application causes a global compaction of the extracellular subunit interface, coupled to an outward motion of the M2-M3 loop near the channel gate, and that these movements are highly conserved in lipid vesicles and detergent micelles. Real-time recordings show that most structural reorganizations are completed within 2ms, much faster than channel opening. Our work thus identifies and structurally characterizes a new pre-active intermediate state in the transition pathway towards activation. Altogether, these combined structural and functional data give insights into the allosteric mechanisms operating in these integral membrane proteins, and pave the way for the rational design of new classes of allosteric modulators.
Modulation of glutamate receptor function by interecting membrane-resident proteins
Michael Hollmann, Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum, Bochum, Germany & NIH/NICHD, Bethesda, MD, USA.
Although ionotropic glutamate receptors (iGluRs) are able to function as tetrameric complexes on their own, many interacting and modulating auxiliary subunits have been identified over the last 15 years. Some of them influence biophysical properties of iGluRs, others modulate the trafficking of the receptors to the plasma membrane, and still other do both. The most commonly known auxiliary proteins are the transmembrane AMPA receptor regulatory proteins (TARPs), the cornichon homologs (CNIH), and the neuropilin- and tolloid-like proteins (NETOs). We used two different heterologous expression systems, Xenopus oocytes and HEK-293 cells, to characterize another class of proteins that modulate AMPA receptor function. We show that certain members of the claudin family, which have high structure and sequence homology with the TARP proteins, act as AMPAR modulators. Claudins are generally known as tight junction proteins that seal passageways within and in between plasma membranes. Of the 22-24 different claudin genes identified in rat, mouse, and humans, few have been functionally characterized. We show that claudin-20 and claudin-24 potentiate the current amplitude and modulate the desensitization of certain AMPA receptors. Other iGluR subtypes such as NMDARs and kainate receptors are not affected, and other claudins do not show this modulatory action. Amplitude potentiation was seen with GluA1 and GluA2 receptors, with effects being more pronounced with flip than with flop splice variants and with R than with Q editing variants. We further show that both claudin-20 and claudin-24 are expressed in the brain, particularly in the granule cell layers of the cerebellum and the olfactory bulb, with claudin-24 in addition found at low levels in principal cells of the hippocampus. Moreover, using FRET after acceptor bleaching, we demonstrated that claudin-20 interacts directly with GluA1. In summary, we identified an unexpected new class of AMPAR modulators that show exquisitely editing variant-specific effects, which are reminiscent of the properties of the type II-TARP g5.
3D-structure and allostery of pentameric ligand-gated ion channel
P.J. Corringer Pasteur Institute, Channel-receptor Unit, CNRS UMR 3571, 25 rue du Docteur Roux, Paris, France
Spider toxins affecting voltage-gated sodium channels
A. Vassilevski, Shemyakin-Ovchinnikov Institute of bioorganic chemistry RAS, Moscow
New properties of classical toxins
Y. Utkin, Shemyakin-Ovchinnikov Institute of bioorganic chemistry RAS, Moscow
Actin-gated sodium channels in nonexcitable cells
A. Sudarikova, Institute of Cytology RAS, St. Petersburg, Russia
Temperature-sensitive gating of TRPV-1 channel as probed by atomistic simulations
A. Chugunov, Shemyakin-Ovchinnikov Institute of bioorganic chemistry RAS, Moscow
Structural studies of isolated voltage-sensing domains of K+ and Na+ channels
Z. Shenkarev, Shemyakin-Ovchinnikov Institute of bioorganic chemistry RAS, Moscow
february 15, 2017