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      Cryo-electron microscopy structure of the TRPV2 ion channel

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          Abstract

          Transient receptor potential vanilloid (TRPV) cation channels are polymodal sensors involved in a variety of physiological processes. TRPV2, a member of the TRPV family, is regulated by temperature, by ligands, such as probenecid and cannabinoids, and by lipids. TRPV2 has been implicated in many biological functions, including somatosensation, osmosensation and innate immunity. Here we present the atomic model of rabbit TRPV2 in its putative desensitized state, as determined by cryo-EM at a nominal resolution of ~4 Å. In the TRPV2 structure, the transmembrane segment 6 (S6), which is involved in gate opening, adopts a conformation different from the one observed in TRPV1. Structural comparisons of TRPV1 and TRPV2 indicate that a rotation of the ankyrin-repeat domain is coupled to pore opening via the TRP domain, and this pore opening can be modulated by rearrangements in the secondary structure of S6.

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          Most cited references 44

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          Structure of the TRPV1 ion channel determined by electron cryo-microscopy

          Transient receptor potential (TRP) channels are sensors for a wide range of cellular and environmental signals, but elucidating how these channels respond to physical and chemical stimuli has been hampered by a lack of detailed structural information. Here, we exploit advances in electron cryo-microscopy to determine the structure of a mammalian TRP channel, TRPV1, at 3.4Å resolution, breaking the side-chain resolution barrier for membrane proteins without crystallization. Like voltage-gated channels, TRPV1 exhibits four-fold symmetry around a central ion pathway formed by transmembrane helices S5–S6 and the intervening pore loop, which is flanked by S1–S4 voltage sensor-like domains. TRPV1 has a wide extracellular ‘mouth’ with short selectivity filter. The conserved ‘TRP domain’ interacts with the S4–S5 linker, consistent with its contribution to allosteric modulation. Subunit organization is facilitated by interactions among cytoplasmic domains, including N-terminal ankyrin repeats. These observations provide a structural blueprint for understanding unique aspects of TRP channel function.
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            An introduction to TRP channels.

            The aim of this review is to provide a basic framework for understanding the function of mammalian transient receptor potential (TRP) channels, particularly as they have been elucidated in heterologous expression systems. Mammalian TRP channel proteins form six-transmembrane (6-TM) cation-permeable channels that may be grouped into six subfamilies on the basis of amino acid sequence homology (TRPC, TRPV, TRPM, TRPA, TRPP, and TRPML). Selected functional properties of TRP channels from each subfamily are summarized in this review. Although a single defining characteristic of TRP channel function has not yet emerged, TRP channels may be generally described as calcium-permeable cation channels with polymodal activation properties. By integrating multiple concomitant stimuli and coupling their activity to downstream cellular signal amplification via calcium permeation and membrane depolarization, TRP channels appear well adapted to function in cellular sensation. Our review of recent literature implicating TRP channels in neuronal growth cone steering suggests that TRPs may function more widely in cellular guidance and chemotaxis. The TRP channel gene family and its nomenclature, the encoded proteins and alternatively spliced variants, and the rapidly expanding pharmacology of TRP channels are summarized in online supplemental material.
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              TRPV1 structures in distinct conformations reveal mechanisms of activation

              TRP channels are polymodal signal detectors that respond to a wide range of physical and chemical stimuli. Elucidating how these channels integrate and convert physiological signals into channel opening is essential to understanding how they regulate cell excitability under normal and pathophysiological conditions. Here we exploit pharmacological probes (a peptide toxin and small vanilloid agonists) to determine structures of two activated states of the capsaicin receptor, TRPV1. A domain (S1-S4) that moves during activation of voltage-gated channels remains stationary in TRPV1, highlighting differences in gating mechanisms for these structurally related channel superfamilies. TRPV1 opening is associated with major structural rearrangements in the outer pore, including the pore helix and selectivity filter, as well as pronounced dilation of a hydrophobic constriction at the lower gate, suggesting a dual gating mechanism. Allosteric coupling between upper and lower gates may account for rich physiologic modulation exhibited by TRPV1 and other TRP channels.
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                Author and article information

                Journal
                101186374
                31761
                Nat Struct Mol Biol
                Nat. Struct. Mol. Biol.
                Nature structural & molecular biology
                1545-9993
                1545-9985
                23 March 2016
                18 January 2016
                February 2016
                18 July 2016
                : 23
                : 2
                : 180-186
                Affiliations
                [1 ]Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, USA.
                [2 ]Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA.
                Author notes
                Correspondence should be addressed to S.-Y.L. ( sylee@ 123456biochem.duke.edu ) or G.C.L. ( glander@ 123456scripps.edu ).
                Article
                NIHMS771401
                10.1038/nsmb.3159
                4876856
                26779611

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                Molecular biology

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