Interactions between a Pore-Blocking Peptide and the Voltage Sensor of the Sodium Channel: An Electrostatic Approach to Channel Geometry

French, Robert J.; Prusak-Sochaczewski, Elzbieta; Zamponi, Gerald W.; Becker, Stefan; Kularatna, A.Shavantha; Horn, Richard

doi:10.1016/s0896-6273(00)80058-6

Cited by 93 publications

(87 citation statements)

References 38 publications

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“…The highly charged pore blocking peptide, μ-conotoxin (μ-CTX), has been previously suggested to shift the voltage dependence of activation by a small degree by modifying the surface charge (55). Our prediction will be that μ-CTX, which has a nominal net charge of +6 at neutral pH, will have a much larger effect on gating pore currents if these interactions are determined solely by electrostatics (56).…”

Section: Resultsmentioning

confidence: 87%

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor

Capes

Arcísio-Miranda

Jarecki

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Voltage-dependent ion channels are crucial for generation and propagation of electrical activity in biological systems. The primary mechanism for voltage transduction in these proteins involves the movement of a voltage-sensing domain (D), which opens a gate located on the cytoplasmic side. A distinct conformational change in the selectivity filter near the extracellular side has been implicated in slow inactivation gating, which is important for spike frequency adaptation in neural circuits. However, it remains an open question whether gating transitions in the selectivity filter region are also actuated by voltage sensors. Here, we examine conformational coupling between each of the four voltage sensors and the outer pore of a eukaryotic voltage-dependent sodium channel. The voltage sensors of these sodium channels are not structurally symmetric and exhibit functional specialization. To track the conformational rearrangements of individual voltagesensing domains, we recorded domain-specific gating pore currents. Our data show that, of the four voltage sensors, only the domain IV voltage sensor is coupled to the conformation of the selectivity filter region of the sodium channel. Trapping the outer pore in a particular conformation with a high-affinity toxin or disulphide crossbridge impedes the return of this voltage sensor to its resting conformation. Our findings directly establish that, in addition to the canonical electromechanical coupling between voltage sensor and inner pore gates of a sodium channel, gating transitions in the selectivity filter region are also coupled to the movement of a voltage sensor. Furthermore, our results also imply that the voltage sensor of domain IV is unique in this linkage and in the ability to initiate slow inactivation in sodium channels. electrophysiology | Nav1.4 | outer pore conformation

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Section: Resultsmentioning

confidence: 87%

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor

Capes

Arcísio-Miranda

Jarecki

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…For example, one possibility is to estimate the distance that VSD charges would have to move to account for voltage sensitivity of activation or measured gating currents. Energetic calculations, based on activation shifts resulting from discrete perturbations in the local electric field sensed by the VSDs when a GIIIA derivative binds to and dissociates from the pore, are consistent with a net movement of the center of the gating charge of a few angstroms (14) but require assumptions of the shape of the potential profile across the VSD and the resting position of the center of the gating charge. The present results are consistent with those previous estimates, but further experiments will be needed to construct a complete picture of mammalian Nav VSD charge movement and gating dynamics.…”

Section: Discussionmentioning

confidence: 96%

“…Therefore, techniques that provide dynamic structural information are needed to elucidate the mechanisms of voltagesensing operation in mammalian Navs. In earlier functional studies on skeletal muscle Navs, we used derivatives of μ-conotoxin GIIIA to obtain approximate estimates of distances within the pore vestibule (13), and of a "mean" distance moved by gating charges during activation (14), obtained from electrostatic calculations in both cases.…”

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confidence: 99%

Mapping of voltage sensor positions in resting and inactivated mammalian sodium channels by LRET

Kubota

Durek

Dang

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Voltage-gated sodium channels (Navs) play crucial roles in excitable cells. Although vertebrate Nav function has been extensively studied, the detailed structural basis for voltage-dependent gating mechanisms remain obscure. We have assessed the structural changes of the Nav voltage sensor domain using lanthanide-based resonance energy transfer (LRET) between the rat skeletal muscle voltage-gated sodium channel (Nav1.4) and fluorescently labeled Nav1.4-targeting toxins. We generated donor constructs with genetically encoded lanthanide-binding tags (LBTs) inserted at the extracellular end of the S4 segment of each domain (with a single LBT per construct). Three different Bodipy-labeled, Nav1.4-targeting toxins were synthesized as acceptors: β-scorpion toxin (Ts1)-Bodipy, KIIIA-Bodipy, and GIIIA-Bodipy analogs. Functional Nav-LBT channels expressed in Xenopus oocytes were voltage-clamped, and distinct LRET signals were obtained in the resting and slow inactivated states. Intramolecular distances computed from the LRET signals define a geometrical map of Nav1.4 with the bound toxins, and reveal voltage-dependent structural changes related to channel gating.V oltage-gated sodium channels (Navs) play an essential role in the generation and propagation of action potentials in excitable cells (1). Eukaryotic Navs are composed of a poreforming α subunit and auxiliary β subunits. The α subunit is a large single-polypeptide chain organized in four different domains (DI-DIV), each of which has a voltage-sensing domain (VSD; S1-S4 segments) and a pore-forming domain (S5-S6 segments). Each domain has a different amino acid composition, pointing to some level of functional specialization. Site-directed fluorimetry shows that the VSDs in DI, DII, and DIII of the rat skeletal muscle voltage-gated sodium channel (Nav1.4) are activated by depolarization faster than in DIV (2). From this observation, it has been hypothesized that DI-III VSDs control the pore opening of the mammalian Nav, whereas the DIV VSD governs its fast inactivation (2-5).Although mammalian Nav function has been studied comprehensively, the precise structural basis for the gating mechanisms has not been fully elucidated. The crystal structures of several prokaryotic Navs have been solved recently; however, in contrast to the mammalian Navs, they are homotetrameric, and thus structurally more closely related to the organization of voltage-gated potassium channels (Kvs) (6-9). The structure of a human L-type voltage-gated calcium channel type 1.1 (Cav1.1), which is a large single polypeptide composed of four different domains similar to mammalian Navs, has been resolved using cryoelectron microscopy (10, 11). However, functional studies have shown that gating mechanisms of mammalian Cav channels are indeed different from gating mechanisms in mammalian Navs (12). Furthermore, such structural studies only provide static snapshots of the channels in one of many possible conformational states. Therefore, techniques that provide dynamic structural information are nee...

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“…3). The magnitude of molecular gating forces, Z, as obtained from fitting the gating-spring model, are of the order of tens to hundreds of fN (Russell & Kossl, 1992;Jaramillo & Hudspeth, 1993;Markin & Hudspeth, 1995;van Netten & Kros, 2000), which, when considering the lever action of the hair bundle, corresponds at the molecular level to forces (z) of up to the order of ten pico-Newtons and are thus comparable to those found to move the transmembrane voltage sensors that gate Na + channels (French et al, 1996) or unbind motor molecules (Nishizaka et al, 1995), while they present lower values found for receptor-ligand bonds (Merkel et al, 1999). Recently much larger gating forces have been observed in rat outer hair cells, forces that are more difficult to explain by a simple gating process .…”

Section: Forces Related To Gatingmentioning

confidence: 92%

Mechano-electrical Transduction: New Insights into Old Ideas

et al. 2006

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The gating-spring theory of hair cell mechanotransduction channel activation was first postulated over twenty years ago. The basic tenets of this hypothesis have been reaffirmed in hair cells from both auditory and vestibular systems and across species. In fact, the basic findings have been reproduced in every hair cell type tested. A great deal of information regarding the structural, mechanical, molecular and biophysical properties of the sensory hair bundle and the mechanotransducer channel has accumulated over the past twenty years. The goal of this review is to investigate new data, using the gating spring hypothesis as the framework for discussion. Mechanisms of channel gating are presented in reference to the need for a molecular gating spring or for tethering to the intra-or extracellular compartments. Dynamics of the sensory hair bundle and the presence of motor proteins are discussed in reference to passive contributions of the hair bundle to gating compliance. And finally, the molecular identity of the channel is discussed in reference to known intrinsic properties of the native transducer channel.

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Interactions between a Pore-Blocking Peptide and the Voltage Sensor of the Sodium Channel: An Electrostatic Approach to Channel Geometry

Cited by 93 publications

References 38 publications

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor

Mapping of voltage sensor positions in resting and inactivated mammalian sodium channels by LRET

Mechano-electrical Transduction: New Insights into Old Ideas

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