scholarly journals Voltage-Gated Sodium Channel Modulation by a New Spider Toxin Ssp1a Isolated From an Australian Theraphosid

2021 ◽  
Vol 12 ◽  
Author(s):  
Yashad Dongol ◽  
Phil M. Choi ◽  
David T. Wilson ◽  
Norelle L. Daly ◽  
Fernanda C. Cardoso ◽  
...  
Keyword(s):  
Rank Order ◽  
Structural Features ◽  
Docking Studies ◽  
Resonance Spectroscopy ◽  
Voltage Gated ◽  
Recovery From Inactivation ◽  
Voltage Dependent ◽  
Dependent Inhibition ◽  
Voltage Sensing Domain ◽  
Subtype Selective

Given the important role of voltage-gated sodium (NaV) channel-modulating spider toxins in elucidating the function, pharmacology, and mechanism of action of therapeutically relevant NaV channels, we screened the venom from Australian theraphosid species against the human pain target hNaV1.7. Using assay-guided fractionation, we isolated a 33-residue inhibitor cystine knot (ICK) peptide (Ssp1a) belonging to the NaSpTx1 family. Recombinant Ssp1a (rSsp1a) inhibited neuronal hNaV subtypes with a rank order of potency hNaV1.7 > 1.6 > 1.2 > 1.3 > 1.1. rSsp1a inhibited hNaV1.7, hNaV1.2 and hNaV1.3 without significantly altering the voltage-dependence of activation, inactivation, or delay in recovery from inactivation. However, rSsp1a demonstrated voltage-dependent inhibition at hNaV1.7 and rSsp1a-bound hNaV1.7 opened at extreme depolarizations, suggesting rSsp1a likely interacted with voltage-sensing domain II (VSD II) of hNaV1.7 to trap the channel in its resting state. Nuclear magnetic resonance spectroscopy revealed key structural features of Ssp1a, including an amphipathic surface with hydrophobic and charged patches shown by docking studies to comprise the interacting surface. This study provides the basis for future structure-function studies to guide the development of subtype selective inhibitors.

scholarly journals Hydrophobic gasket mutation produces gating pore currents in closed human voltage-gated proton channels

2019 ◽  
Vol 116 (38) ◽  
pp. 18951-18961 ◽  
Author(s):  
Richard Banh ◽  
Vladimir V. Cherny ◽  
Deri Morgan ◽  
Boris Musset ◽  
Sarah Thomas ◽  
...  
Keyword(s):  
Proton Channel ◽  
Voltage Gated ◽  
Closed State ◽  
Channel Opening ◽  
Proton Current ◽  
Voltage Dependent ◽  
Current Flows ◽  
Voltage Gated Ion Channels ◽  
Dynamics Simulations ◽  
Voltage Sensing Domain

The hydrophobic gasket (HG), a ring of hydrophobic amino acids in the voltage-sensing domain of most voltage-gated ion channels, forms a constriction between internal and external aqueous vestibules. Cationic Arg or Lys side chains lining the S4 helix move through this “gating pore” when the channel opens. S4 movement may occur during gating of the human voltage-gated proton channel, hHV1, but proton current flows through the same pore in open channels. Here, we replaced putative HG residues with less hydrophobic residues or acidic Asp. Substitution of individuals, pairs, or all 3 HG positions did not impair proton selectivity. Evidently, the HG does not act as a secondary selectivity filter. However, 2 unexpected functions of the HG in HV1 were discovered. Mutating HG residues independently accelerated channel opening and compromised the closed state. Mutants exhibited open–closed gating, but strikingly, at negative voltages where “normal” gating produces a nonconducting closed state, the channel leaked protons. Closed-channel proton current was smaller than open-channel current and was inhibited by 10 μM Zn2+. Extreme hyperpolarization produced a deeper closed state through a weakly voltage-dependent transition. We functionally identify the HG as Val109, Phe150, Val177, and Val178, which play a critical and exclusive role in preventing H+ influx through closed channels. Molecular dynamics simulations revealed enhanced mobility of Arg208 in mutants exhibiting H+ leak. Mutation of HG residues produces gating pore currents reminiscent of several channelopathies.

scholarly journals Insights into the molecular mechanism for hyperpolarization-dependent activation of HCN channels

2018 ◽  
Vol 115 (34) ◽  
pp. E8086-E8095 ◽  
Author(s):  
Galen E. Flynn ◽  
William N. Zagotta
Keyword(s):  
Ion Channels ◽  
Cyclic Nucleotide ◽  
Electromechanical Coupling ◽  
Canonical Model ◽  
Hcn Channels ◽  
Voltage Gated ◽  
Kv Channels ◽  
Recovery From Inactivation ◽  
Voltage Dependent ◽  
Pore Domain

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) ion channels are both voltage- and ligand-activated membrane proteins that contribute to electrical excitability and pace-making activity in cardiac and neuronal cells. These channels are members of the voltage-gated Kv channel superfamily and cyclic nucleotide-binding domain subfamily of ion channels. HCN channels have a unique feature that distinguishes them from other voltage-gated channels: the HCN channel pore opens in response to hyperpolarizing voltages instead of depolarizing voltages. In the canonical model of electromechanical coupling, based on Kv channels, a change in membrane voltage activates the voltage-sensing domains (VSD) and the activation energy passes to the pore domain (PD) through a covalent linker that connects the VSD to the PD. In this investigation, the covalent linkage between the VSD and PD, the S4-S5 linker, and nearby regions of spHCN channels were mutated to determine the functional role each plays in hyperpolarization-dependent activation. The results show that: (i) the S4-S5 linker is not required for hyperpolarization-dependent activation or ligand-dependent gating; (ii) the S4 C-terminal region (S4C-term) is not necessary for ligand-dependent gating but is required for hyperpolarization-dependent activation and acts like an autoinhibitory domain on the PD; (iii) the S5N-term region is involved in VSD–PD coupling and holding the pore closed; and (iv) spHCN channels have two voltage-dependent processes, a hyperpolarization-dependent activation and a depolarization-dependent recovery from inactivation. These results are inconsistent with the canonical model of VSD–PD coupling in Kv channels and elucidate the mechanism for hyperpolarization-dependent activation of HCN channels.

scholarly journals Comparative Effects of Halogenated Inhaled Anesthetics on Voltage-gated Na+Channel Function

2009 ◽  
Vol 110 (3) ◽  
pp. 582-590 ◽  
Author(s):  
Wei Ouyang ◽  
Karl F. Herold ◽  
Hugh C. Hemmings
Keyword(s):  
Rank Order ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Na Channel ◽  
Dependent Manner ◽  
Fast Inactivation ◽  
Inhaled Anesthetics ◽  
Voltage Gated ◽  
Channel Inhibition ◽  
Voltage Dependent

Background Inhibition of voltage-gated Na channels (Na(v)) is implicated in the synaptic actions of volatile anesthetics. We studied the effects of the major halogenated inhaled anesthetics (halothane, isoflurane, sevoflurane, enflurane, and desflurane) on Na(v)1.4, a well-characterized pharmacological model for Na(v) effects. Methods Na currents (I(Na)) from rat Na(v)1.4 alpha-subunits heterologously expressed in Chinese hamster ovary cells were analyzed by whole cell voltage-clamp electrophysiological recording. Results Halogenated inhaled anesthetics reversibly inhibited Na(v)1.4 in a concentration- and voltage-dependent manner at clinical concentrations. At equianesthetic concentrations, peak I(Na) was inhibited with a rank order of desflurane > halothane approximately enflurane > isoflurane approximately sevoflurane from a physiologic holding potential (-80 mV). This suggests that the contribution of Na channel block to anesthesia might vary in an agent-specific manner. From a hyperpolarized holding potential that minimizes inactivation (-120 mV), peak I(Na) was inhibited with a rank order of potency for tonic inhibition of peak I(Na) of halothane > isoflurane approximately sevoflurane > enflurane > desflurane. Desflurane produced the largest negative shift in voltage-dependence of fast inactivation consistent with its more prominent voltage-dependent effects. A comparison between isoflurane and halothane showed that halothane produced greater facilitation of current decay, slowing of recovery from fast inactivation, and use-dependent block than isoflurane. Conclusions Five halogenated inhaled anesthetics all inhibit a voltage-gated Na channel by voltage- and use-dependent mechanisms. Agent-specific differences in efficacy for Na channel inhibition due to differential state-dependent mechanisms creates pharmacologic diversity that could underlie subtle differences in anesthetic and nonanesthetic actions.

scholarly journals Structural basis of gating modulation of Kv4 channel complexes

Nature ◽  
2021 ◽  
Author(s):  
Yoshiaki Kise ◽  
Go Kasuya ◽  
Hiroyuki H. Okamoto ◽  
Daichi Yamanouchi ◽  
Kan Kobayashi ◽  
...  
Keyword(s):  
Structural Basis ◽  
Macromolecular Complex ◽  
Auxiliary Subunits ◽  
Voltage Gated ◽  
Kv Channels ◽  
C Terminus ◽  
Voltage Dependent ◽  
Gated Channel ◽  
Related Proteins ◽  
Voltage Sensing Domain

AbstractModulation of voltage-gated potassium (Kv) channels by auxiliary subunits is central to the physiological function of channels in the brain and heart1,2. Native Kv4 tetrameric channels form macromolecular ternary complexes with two auxiliary β-subunits—intracellular Kv channel-interacting proteins (KChIPs) and transmembrane dipeptidyl peptidase-related proteins (DPPs)—to evoke rapidly activating and inactivating A-type currents, which prevent the backpropagation of action potentials1–5. However, the modulatory mechanisms of Kv4 channel complexes remain largely unknown. Here we report cryo-electron microscopy structures of the Kv4.2–DPP6S–KChIP1 dodecamer complex, the Kv4.2–KChIP1 and Kv4.2–DPP6S octamer complexes, and Kv4.2 alone. The structure of the Kv4.2–KChIP1 complex reveals that the intracellular N terminus of Kv4.2 interacts with its C terminus that extends from the S6 gating helix of the neighbouring Kv4.2 subunit. KChIP1 captures both the N and the C terminus of Kv4.2. In consequence, KChIP1 would prevent N-type inactivation and stabilize the S6 conformation to modulate gating of the S6 helices within the tetramer. By contrast, unlike the reported auxiliary subunits of voltage-gated channel complexes, DPP6S interacts with the S1 and S2 helices of the Kv4.2 voltage-sensing domain, which suggests that DPP6S stabilizes the conformation of the S1–S2 helices. DPP6S may therefore accelerate the voltage-dependent movement of the S4 helices. KChIP1 and DPP6S do not directly interact with each other in the Kv4.2–KChIP1–DPP6S ternary complex. Thus, our data suggest that two distinct modes of modulation contribute in an additive manner to evoke A-type currents from the native Kv4 macromolecular complex.

scholarly journals Molecular Pathology of Sodium Channel Beta-Subunit Variants

2021 ◽  
Vol 12 ◽  
Author(s):  
Paweorn Angsutararux ◽  
Wandi Zhu ◽  
Taylor L. Voelker ◽  
Jonathan R. Silva
Keyword(s):  
Sodium Channel ◽  
Time Course ◽  
Macromolecular Complex ◽  
Excitable Cells ◽  
Recovery From Inactivation ◽  
Voltage Dependent ◽  
Channel Expression ◽  
Familial Atrial Fibrillation ◽  
Voltage Sensing Domain ◽  
Pore Domain

The voltage-gated Na+ channel regulates the initiation and propagation of the action potential in excitable cells. The major cardiac isoform NaV1.5, encoded by SCN5A, comprises a monomer with four homologous repeats (I-IV) that each contain a voltage sensing domain (VSD) and pore domain. In native myocytes, NaV1.5 forms a macromolecular complex with NaVβ subunits and other regulatory proteins within the myocyte membrane to maintain normal cardiac function. Disturbance of the NaV complex may manifest as deadly cardiac arrhythmias. Although SCN5A has long been identified as a gene associated with familial atrial fibrillation (AF) and Brugada Syndrome (BrS), other genetic contributors remain poorly understood. Emerging evidence suggests that mutations in the non-covalently interacting NaVβ1 and NaVβ3 are linked to both AF and BrS. Here, we investigated the molecular pathologies of 8 variants in NaVβ1 and NaVβ3. Our results reveal that NaVβ1 and NaVβ3 variants contribute to AF and BrS disease phenotypes by modulating both NaV1.5 expression and gating properties. Most AF-linked variants in the NaVβ1 subunit do not alter the gating kinetics of the sodium channel, but rather modify the channel expression. In contrast, AF-related NaVβ3 variants directly affect channel gating, altering voltage-dependent activation and the time course of recovery from inactivation via the modulation of VSD activation.

Homology Modeling of Mus Musculus CDK5 and Molecular Docking Studies with Flavonoids

2017 ◽  
Vol 9 (6) ◽  
Author(s):  
Sowmya Suri ◽  
Rumana Waseem ◽  
Seshagiri Bandi ◽  
Sania Shaik
Keyword(s):  
Molecular Docking ◽  
3D Model ◽  
Structural Features ◽  
Docking Studies ◽  
Amino Acid Residues ◽  
Cyclin Dependent Kinase ◽  
Ligand Complex ◽  
Ligand Interaction ◽  
Molecular Docking Studies ◽  
Cyclin Dependent Kinase 5

A 3D model of Cyclin-dependent kinase 5 (CDK5) (Accession Number: Q543f6) is generated based on crystal structure of P. falciparum PFPK5-indirubin-5-sulphonate ligand complex (PDB ID: 1V0O) at 2.30 Å resolution was used as template. Protein-ligand interaction studies were performed with flavonoids to explore structural features and binding mechanism of flavonoids as CDK5 (Cyclin-dependent kinase 5) inhibitors. The modelled structure was selected on the basis of least modeler objective function. The model was validated by PROCHECK. The predicted 3D model is reliable with 93.0% of amino acid residues in core region of the Ramachandran plot. Molecular docking studies with flavonoids viz., Diosmetin, Eriodictyol, Fortuneletin, Apigenin, Ayanin, Baicalein, Chrysoeriol and Chrysosplenol-D with modelled protein indicate that Diosmetin is the best inhibitor containing docking score of -8.23 kcal/mol. Cys83, Lys89, Asp84. The compound Diosmetin shows interactions with Cys83, Lys89, and Asp84.

Insilico studies, synthesis and antitubercular activity of some novel quinoline – azitidinone derivatives

2020 ◽  
Vol 16 ◽  
Author(s):  
Trupti. S. Chitre ◽  
Kalyani. D. Asgaonkar ◽  
Amrut B. Vikhe ◽  
Shital M Patil ◽  
Dinesh. R. Garud ◽  
...  
Keyword(s):  
Combinatorial Library ◽  
3D Qsar ◽  
Antitubercular Activity ◽  
Structural Features ◽  
Docking Studies ◽  
Quinoline Derivatives ◽  
Qsar Models ◽  
Molecular Modeling Studies ◽  
Lead Generation ◽  
Mcf 7

Background: Diarylquinolines like Bedaquiline have shown promising antitubercular activity by their action of Mycobacterial ATPase. Objective: The structural features necessary for good antitubercular activity for a series of quinoline derivatives were explored through computational chemistry tools like QSAR and combinatorial library generation. In the current study, 3-Chloro-4-(2-mercaptoquinoline-3-yl)-1-substitutedphenylazitidin-2-one derivatives have been designed and synthesized based on molecular modeling studies as anti-tubercular agents. Method: 2D and 3DQSAR analysis was used to designed compounds having quinoline scaffold. The synthesized compounds were evaluated against active and dormant strains of Mycobacterium tuberculosis (MTB) H37 Ra and Mycobacterium bovis BCG. The compounds were also tested for cytotoxicity against MCF-7, A549 and Panc-1 cell lines using MTT assay. Binding affinity of designed compounds was gauged by molecular docking studies. Results: Statistically significant QSAR models generated by SA-MLR method for 2D QSAR exhibited r2 = 0.852, q2 = 0.811and whereas 3D QSAR with SA-kNN showed q2 = 0.77. The synthesized compounds exhibited MIC in the range of 1.38-14.59(µg/ml) .These compounds showed some crucial interaction with MTB Atpase. Conclusion: The present study has shown some promising results which can be further explored for lead generation.

scholarly journals 4-Phenethyl-1-Propargylpiperidine-Derived Dual Inhibitors of Butyrylcholinesterase and Monoamine Oxidase B

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4118
Author(s):  
Tjaša Mazej ◽  
Damijan Knez ◽  
Anže Meden ◽  
Stanislav Gobec ◽  
Matej Sova
Keyword(s):  
Monoamine Oxidase ◽  
Docking Studies ◽  
Monoamine Oxidase B ◽  
Mao B ◽  
Initial Expectation ◽  
Excellent Starting Point ◽  
Starting Point ◽  
Dependent Inhibition ◽  
Dual Inhibitors ◽  
Time Dependent Inhibition

The multi-target-directed ligands (MTDLs) strategy is encouraged for the development of novel modulators targeting multiple pathways in the neurodegenerative cascade typical for Alzheimer’s disease (AD). Based on the structure of an in-house irreversible monoamine oxidase B (MAO-B) inhibitor, we aimed to introduce a carbamate moiety on the aromatic ring to impart cholinesterase (ChE) inhibition, and to furnish multifunctional ligands targeting two enzymes that are intricately involved in AD pathobiology. In this study, we synthesized three dual hMAO-B/hBChE inhibitors 13–15, with compound 15 exhibiting balanced, low micromolar inhibition of hMAO-B (IC50 of 4.3 µM) and hBChE (IC50 of 8.5 µM). The docking studies and time-dependent inhibition of hBChE confirmed the initial expectation that the introduced carbamate moiety is responsible for covalent inhibition. Therefore, dual-acting compound 15 represents an excellent starting point for further optimization of balanced MTDLs.

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