C Termini of theEscherichia coliMechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening

At its most fundamental level, touch sensation requires the translation of mechanical energy into mechanosensitive ion channel opening, thereby generating electro-chemical signals. Our understanding of this process, especially how the cytoskeleton influences it, remains unknown. Here we demonstrate that mice lacking the α-tubulin acetyltransferase Atat1 in sensory neurons display profound deficits in their ability to detect mechanical stimuli. We show that all cutaneous afferent subtypes, including nociceptors have strongly reduced mechanosensitivity upon Atat1 deletion, and that consequently, mice are largely insensitive to mechanical touch and pain. We establish that this broad loss of mechanosensitivity is dependent upon the acetyltransferase activity of Atat1, which when absent leads to a decrease in cellular elasticity. By mimicking α-tubulin acetylation genetically, we show both cellular rigidity and mechanosensitivity can be restored in Atat1 deficient sensory neurons. Hence, our results indicate that by influencing cellular stiffness, α-tubulin acetylation sets the force required for touch.

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Calcium-dependent events at fertilization of the frog egg: Injection of a calcium buffer blocks ion channel opening, exocytosis, and formation of pronuclei

Developmental Biology ◽

10.1016/0012-1606(88)90145-5 ◽

1988 ◽

Vol 126 (2) ◽

pp. 346-361 ◽

Cited By ~ 122

Author(s):

Douglas Kline

Keyword(s):

Ion Channel ◽

Calcium Dependent ◽

Calcium Buffer ◽

Channel Opening ◽

Egg Injection

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Allosteric binding site in a Cys-loop receptor ligand-binding domain unveiled in the crystal structure of ELIC in complex with chlorpromazine

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1603101113 ◽

2016 ◽

Vol 113 (43) ◽

pp. E6696-E6703 ◽

Cited By ~ 18

Author(s):

Mieke Nys ◽

Eveline Wijckmans ◽

Ana Farinha ◽

Özge Yoluk ◽

Magnus Andersson ◽

...

Keyword(s):

Ligand Binding ◽

Ion Channel ◽

Binding Site ◽

Binding Domain ◽

Ligand Binding Domain ◽

Channel Pore ◽

X Ray ◽

Electrophysiological Recordings ◽

Channel Opening ◽

Dynamics Simulations

Pentameric ligand-gated ion channels or Cys-loop receptors are responsible for fast inhibitory or excitatory synaptic transmission. The antipsychotic compound chlorpromazine is a widely used tool to probe the ion channel pore of the nicotinic acetylcholine receptor, which is a prototypical Cys-loop receptor. In this study, we determine the molecular determinants of chlorpromazine binding in the Erwinia ligand-gated ion channel (ELIC). We report the X-ray crystal structures of ELIC in complex with chlorpromazine or its brominated derivative bromopromazine. Unexpectedly, we do not find a chlorpromazine molecule in the channel pore of ELIC, but behind the β8–β9 loop in the extracellular ligand-binding domain. The β8–β9 loop is localized downstream from the neurotransmitter binding site and plays an important role in coupling of ligand binding to channel opening. In combination with electrophysiological recordings from ELIC cysteine mutants and a thiol-reactive derivative of chlorpromazine, we demonstrate that chlorpromazine binding at the β8–β9 loop is responsible for receptor inhibition. We further use molecular-dynamics simulations to support the X-ray data and mutagenesis experiments. Together, these data unveil an allosteric binding site in the extracellular ligand-binding domain of ELIC. Our results extend on previous observations and further substantiate our understanding of a multisite model for allosteric modulation of Cys-loop receptors.

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Apocalmodulin Itself Promotes Ion Channel Opening and Ca2+ Regulation

Cell ◽

10.1016/j.cell.2014.09.047 ◽

2014 ◽

Vol 159 (3) ◽

pp. 608-622 ◽

Cited By ~ 48

Author(s):

Paul J. Adams ◽

Manu Ben-Johny ◽

Ivy E. Dick ◽

Takanari Inoue ◽

David T. Yue

Keyword(s):

Ion Channel ◽

Channel Opening

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Evidence that ion conduction in 5-HT3A receptors proceeds through lateral portals in the cytosol

10.1101/2020.02.10.943084 ◽

2020 ◽

Author(s):

Antonia G. Stuebler ◽

Michaela Jansen

Keyword(s):

Ion Channel ◽

Disulfide Bond ◽

Conformational Changes ◽

Bond Formation ◽

Disulfide Bond Formation ◽

Transmembrane Segment ◽

Ion Conduction ◽

Intracellular Domain ◽

Channel Opening ◽

Conduction Pathway

AbstractThe intracellular domain of the serotonin type 3A receptor, a pentameric ligand-gated ion channel, is crucial for regulating conductance. However, the specific ion conduction pathway through this domain is less clear. The intracellular domain starts with a short loop after the third transmembrane segment, followed by a short α-helical segment, a large unstructured loop, and finally the membrane-associated MA-helix that continues into the last transmembrane segment. The MA-helices from all five subunits form the extension of the transmembrane ion channel and shape what has been described as a “closed vestibule”, with their lateral portals obstructed by loops and their cytosolic ends forming a tight hydrophobic constriction. The question remains whether the lateral portals or cytosolic constriction conduct ions upon channel opening. In the present study, we used disulfide bond formation between pairs of engineered cysteines to probe the proximity and mobility of segments of the MA-helices most distal to the membrane bilayer. Our results indicate that the proximity and orientation for cysteine pairs at I409C/R410C, in close proximity to the lateral windows, and L402C/L403C, at the cytosolic ends of the MA-helices, are conducive for disulfide bond formation. While conformational changes associated with gating promote crosslinking for I409C/R410C, which in turn decreases channel currents, crosslinking of L402C/L403C is functionally silent in macroscopic currents. These results support the hypothesis that concerted conformational changes open the lateral portals for ion conduction, rendering ion conduction through the vertical portal unlikely.SignificanceThe intracellular domain (ICD) of pentameric ligand-gated ion channels (pLGICs) is the most diverse domain within receptors of the Cys-loop superfamily. Despite being the least understood domain of pLGICs, its impact on ion-channel function and contribution to the cytosolic exit pathway of the channel have been investigated. X-ray and cryo-EM structures have captured the structured segments of the ICD of 5-HT3A receptors in different conformational states with lower resolution of the ICD as compared to the other domains. Here, we provide experimentally derived evidence for the importance of the differential mobility of the cytosolic segment of the MA-helices, which supports the existence of lateral portals as opposed to a vertical pathway for 5-HT3A receptors.

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Cryo-EM Captures the Dynamics of Ion Channel Opening

Cell ◽

10.1016/j.cell.2017.01.011 ◽

2017 ◽

Vol 168 (3) ◽

pp. 341-343 ◽

Cited By ~ 8

Author(s):

John L. Rubinstein

Keyword(s):

Ion Channel ◽

Channel Opening

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Control of the CFTR channel's gates

Biochemical Society Transactions ◽

10.1042/bst0331003 ◽

2005 ◽

Vol 33 (5) ◽

pp. 1003-1007 ◽

Cited By ~ 13

Author(s):

P. Vergani ◽

C. Basso ◽

M. Mense ◽

A.C. Nairn ◽

D.C. Gadsby

Keyword(s):

Cystic Fibrosis ◽

Ion Channel ◽

Single Channel ◽

Atp Binding ◽

Transmembrane Conductance Regulator ◽

Binding Domains ◽

Abc Protein ◽

Channel Opening ◽

Atp Binding And Hydrolysis ◽

Opening And Closing

Unique among ABC (ATP-binding cassette) protein family members, CFTR (cystic fibrosis transmembrane conductance regulator), also termed ABCC7, encoded by the gene mutated in cystic fibrosis patients, functions as an ion channel. Opening and closing of its anion-selective pore are linked to ATP binding and hydrolysis at CFTR's two NBDs (nucleotide-binding domains), NBD1 and NBD2. Isolated NBDs of prokaryotic ABC proteins form homodimers upon binding ATP, but separate after hydrolysis of the ATP. By combining mutagenesis with single-channel recording and nucleotide photolabelling on intact CFTR molecules, we relate opening and closing of the channel gates to ATP-mediated events in the NBDs. In particular, we demonstrate that two CFTR residues, predicted to lie on opposite sides of its anticipated NBD1–NBD2 heterodimer interface, are energetically coupled when the channels open but are independent of each other in closed channels. This directly links ATP-driven tight dimerization of CFTR's cytoplasmic NBDs to opening of the ion channel in the transmembrane domains. Evolutionary conservation of the energetically coupled residues in a manner that preserves their ability to form a hydrogen bond argues that this molecular mechanism, involving dynamic restructuring of the NBD dimer interface, is shared by all members of the ABC protein superfamily.

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Dimer interaction in the Hv1 proton channel

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2010032117 ◽

2020 ◽

Vol 117 (34) ◽

pp. 20898-20907

Author(s):

Laetitia Mony ◽

David Stroebel ◽

Ehud Y. Isacoff

Keyword(s):

Functional Analysis ◽

Ion Channel ◽

Coiled Coil ◽

Voltage Sensor ◽

Proton Channel ◽

Dimer Interface ◽

Voltage Sensors ◽

Voltage Gated ◽

Channel Opening ◽

The Stability

The voltage-gated proton channel Hv1 is a member of the voltage-gated ion channel superfamily, which stands out in design: It is a dimer of two voltage-sensing domains (VSDs), each containing a pore pathway, a voltage sensor (S4), and a gate (S1) and forming its own ion channel. Opening of the two channels in the dimer is cooperative. Part of the cooperativity is due to association between coiled-coil domains that extend intracellularly from the S4s. Interactions between the transmembrane portions of the subunits may also contribute, but the nature of transmembrane packing is unclear. Using functional analysis of a mutagenesis scan, biochemistry, and modeling, we find that the subunits form a dimer interface along the entire length of S1, and also have intersubunit contacts between S1 and S4. These interactions exert a strong effect on gating, in particular on the stability of the open state. Our results suggest that gating in Hv1 is tuned by extensive VSD–VSD interactions between the gates and voltage sensors of the dimeric channel.

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