Molecular Bases for the Asynchronous Activation of Sodium and Potassium Channels Required for Nerve Impulse Generation

Lacroix, Jérôme J.; Campos, Fabiana V.; Frezza, Ludivine; Bezanilla, Francisco

doi:10.1016/j.neuron.2013.05.036

Cited by 53 publications

(68 citation statements)

References 31 publications

(44 reference statements)

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“…Previous mutational analysis of I287 showed that the side-chain hydrophobicity at this position affects VSD kinetics (46). Our present correlation analysis, made on a slightly larger number of mutations, reveals that both hydrophobicity and size matter at position I287 ( Table 2), suggesting that both chemical aspects of this lateral chain are important for VSD function.…”

Section: Vsd Parameters Correlate With Physicochemical Properties Of supporting

confidence: 54%

“…Because no gating current could be detected in the double mutant I287D-R4K, the occurrence of interactions between I287D and R4 cannot be excluded. I287 was previously shown to lie within atomic proximity of R1 in the resting state, to seal the gating pore from ionic leak and to finetune the kinetic differences between Kv and Nav channels' VSDs, further supporting the importance of I287 to control the VSD activation energy barrier (17,46).…”

Section: Vsd Parameters Correlate With Physicochemical Properties Of mentioning

confidence: 77%

“…Eight out of 10 residues forming the gating pore in the Shaker Kv channel (V236, I237, S240, F244, C286, I287, A319, and I320) ( Fig. 1 A and B) were individually mutated by a large number of amino acids, creating an exhaustive library of 114 point mutations [see Table 1, which also includes previously reported mutations of I241, I287, and F290 (38,46,47)]. Each mutant was heterologously expressed in Xenopus oocytes and characterized using the high-resolution cut-open voltage-clamp technique (48).…”

Section: Resultsmentioning

confidence: 99%

“…2F). This was surprising because hydrophilic mutations at position I287 were expected to speed up VSD kinetics (46). Intriguingly, whereas the gating currents generated in the I287D channel during depolarization (ON-pulse) appear normal, the gating currents produced during repolarization (OFF-pulse) seem to progressively disappear as the amplitude of the depolarizing ON-pulse increases (Fig.…”

Section: Vsd Parameters Correlate With Physicochemical Properties Of mentioning

confidence: 99%

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Moving gating charges through the gating pore in a Kv channel voltage sensor

Lacroix

Hyde

Campos

et al. 2014

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

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Voltage sensor domains (VSDs) regulate ion channels and enzymes by transporting electrically charged residues across a hydrophobic VSD constriction called the gating pore or hydrophobic plug. How the gating pore controls the gating charge movement presently remains debated. Here, using saturation mutagenesis and detailed analysis of gating currents from gating pore mutations in the Shaker Kv channel, we identified statistically highly significant correlations between VSD function and physicochemical properties of gating pore residues. A necessary small residue at position S240 in S1 creates a "steric gap" that enables an intracellular access pathway for the transport of the S4 Arg residues. In addition, the stabilization of the depolarized VSD conformation, a hallmark for most Kv channels, requires large side chains at positions F290 in S2 and F244 in S1 acting as "molecular clamps," and a hydrophobic side chain at position I237 in S1 acting as a local intracellular hydrophobic barrier. Finally, both size and hydrophobicity of I287 are important to control the main VSD energy barrier underlying transitions between resting and active states. Taken together, our study emphasizes the contribution of several gating pore residues to catalyze the gating charge transfer. This work paves the way toward understanding physicochemical principles underlying conformational dynamics in voltage sensors.energy landscape | kinetic model | global fit

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Section: Vsd Parameters Correlate With Physicochemical Properties Of supporting

confidence: 54%

Section: Vsd Parameters Correlate With Physicochemical Properties Of mentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Section: Vsd Parameters Correlate With Physicochemical Properties Of mentioning

confidence: 99%

See 2 more Smart Citations

Moving gating charges through the gating pore in a Kv channel voltage sensor

Lacroix

Hyde

Campos

et al. 2014

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

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“…This segment confers to VSDs their sensitivity to external voltages, by translating vertically in response to voltage changes (Fig. 1A), and determines their voltage dependency, which is tuned by the number of S4 charges and their specific interactions with their environment (8,9).…”

mentioning

confidence: 99%

Free-energy landscape of ion-channel voltage-sensor–domain activation

Delemotte

Kasimova

Klein

et al. 2014

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

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Voltage sensor domains (VSDs) are membrane-bound protein modules that confer voltage sensitivity to membrane proteins. VSDs sense changes in the transmembrane voltage and convert the electrical signal into a conformational change called activation. Activation involves a reorganization of the membrane protein charges that is detected experimentally as transient currents. These so-called gating currents have been investigated extensively within the theoretical framework of so-called discrete-state Markov models (DMMs), whereby activation is conceptualized as a series of transitions across a discrete set of states. Historically, the interpretation of DMM transition rates in terms of transition state theory has been instrumental in shaping our view of the activation process, whose free-energy profile is currently envisioned as composed of a few local minima separated by steep barriers. Here we use atomistic level modeling and well-tempered metadynamics to calculate the configurational free energy along a single transition from first principles. We show that this transition is intrinsically multidimensional and described by a rough free-energy landscape. Remarkably, a coarse-grained description of the system, based on the use of the gating charge as reaction coordinate, reveals a smooth profile with a single barrier, consistent with phenomenological models. Our results bridge the gap between microscopic and macroscopic descriptions of activation dynamics and show that choosing the gating charge as reaction coordinate masks the topological complexity of the network of microstates participating in the transition. Importantly, full characterization of the latter is a prerequisite to rationalize modulation of this process by lipids, toxins, drugs, and genetic mutations.Kv1.2 | voltage-gated ion channels | gating kinetics | electrophysiology | metadynamics V oltage sensor domains (VSDs) are key players of diverse physiological processes involving changes in transmembrane (TM) potential: electrical impulse propagation, cellular contraction, and activation of metabolic pathways are only few possible examples (1). As such, they are the target of toxins produced by many venomous animals (2) and are becoming a popular target for drug development (3). Most of what we know about VSDs comes from the study of voltage-gated cation channels, mainly potassium and sodium selective ones, each containing four distinct VSDs. VSDs are formed by a bundle of four TM helices (S1-S4) (4-7). The S4 segment contains a series of positively charged residues, called gating charges, arranged along its inward-facing side. This segment confers to VSDs their sensitivity to external voltages, by translating vertically in response to voltage changes (Fig. 1A), and determines their voltage dependency, which is tuned by the number of S4 charges and their specific interactions with their environment (8, 9).For several decades, the molecular details of the VSD activation mechanism have been investigated extensively using diverse experimental techniques such...

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Cell‐Derived Vesicles for Single‐Molecule Imaging of Membrane Proteins

et al. 2014

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A new approach is presented for the application of single‐molecule imaging to membrane receptors through the use of vesicles derived from cells expressing fluorescently labeled receptors. During the isolation of vesicles, receptors remain embedded in the membrane of the resultant vesicles, thus allowing these vesicles to serve as nanocontainers for single‐molecule measurements. Cell‐derived vesicles maintain the structural integrity of transmembrane receptors by keeping them in their physiological membrane. It was demonstrated that receptors isolated in these vesicles can be studied with solution‐based fluorescence correlation spectroscopy (FCS) and can be isolated on a solid substrate for single‐molecule studies. This technique was applied to determine the stoichiometry of α3β4 nicotinic receptors. The method provides the capability to extend single‐molecule studies to previously inaccessible classes of receptors.

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Molecular Bases for the Asynchronous Activation of Sodium and Potassium Channels Required for Nerve Impulse Generation

Cited by 53 publications

References 31 publications

Moving gating charges through the gating pore in a Kv channel voltage sensor

Moving gating charges through the gating pore in a Kv channel voltage sensor

Free-energy landscape of ion-channel voltage-sensor–domain activation

Cell‐Derived Vesicles for Single‐Molecule Imaging of Membrane Proteins

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