scholarly journals Drug-induced ion channel opening tuned by the voltage sensor charge profile

2014 ◽  
Vol 143 (2) ◽  
pp. 173-182 ◽  
Author(s):  
Nina E. Ottosson ◽  
Sara I. Liin ◽  
Fredrik Elinder
Keyword(s):  
Small Molecule ◽  
Voltage Sensor ◽  
K Channel ◽  
Detailed Knowledge ◽  
Drug Induced ◽  
New Class ◽  
Channel Opening ◽  
Future Drug ◽  
Small Molecule Compound ◽  
Voltage Gated Ion Channels

Polyunsaturated fatty acids modulate the voltage dependence of several voltage-gated ion channels, thereby being potent modifiers of cellular excitability. Detailed knowledge of this molecular mechanism can be used in designing a new class of small-molecule compounds against hyperexcitability diseases. Here, we show that arginines on one side of the helical K-channel voltage sensor S4 increased the sensitivity to docosahexaenoic acid (DHA), whereas arginines on the opposing side decreased this sensitivity. Glutamates had opposite effects. In addition, a positively charged DHA-like molecule, arachidonyl amine, had opposite effects to the negatively charged DHA. This suggests that S4 rotates to open the channel and that DHA electrostatically affects this rotation. A channel with arginines in positions 356, 359, and 362 was extremely sensitive to DHA: 70 µM DHA at pH 9.0 increased the current >500 times at negative voltages compared with wild type (WT). The small-molecule compound pimaric acid, a novel Shaker channel opener, opened the WT channel. The 356R/359R/362R channel drastically increased this effect, suggesting it to be instrumental in future drug screening.

scholarly journals An electrostatic potassium channel opener targeting the final voltage sensor transition

2011 ◽  
Vol 137 (6) ◽  
pp. 563-577 ◽  
Author(s):  
Sara I. Börjesson ◽  
Fredrik Elinder
Keyword(s):  
Ion Channels ◽  
Epileptic Seizures ◽  
Voltage Sensor ◽  
K Channel ◽  
Voltage Gated ◽  
Pharmacological Mechanism ◽  
Channel Opening ◽  
Channel Surface ◽  
Future Drug ◽  
Voltage Gated Ion Channels

Free polyunsaturated fatty acids (PUFAs) modulate the voltage dependence of voltage-gated ion channels. As an important consequence thereof, PUFAs can suppress epileptic seizures and cardiac arrhythmia. However, molecular details for the interaction between PUFA and ion channels are not well understood. In this study, we have localized the site of action for PUFAs on the voltage-gated Shaker K channel by introducing positive charges on the channel surface, which potentiated the PUFA effect. Furthermore, we found that PUFA mainly affects the final voltage sensor movement, which is closely linked to channel opening, and that specific charges at the extracellular end of the voltage sensor are critical for the PUFA effect. Because different voltage-gated K channels have different charge profiles, this implies channel-specific PUFA effects. The identified site and the pharmacological mechanism will potentially be very useful in future drug design of small-molecule compounds specifically targeting neuronal and cardiac excitability.

scholarly journals Hydrophobic interaction between contiguous residues in the S6 transmembrane segment acts as a stimuli integration node in the BK channel

2014 ◽  
Vol 145 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Willy Carrasquel-Ursulaez ◽  
Gustavo F. Contreras ◽  
Romina V. Sepúlveda ◽  
Daniel Aguayo ◽  
Fernando González-Nilo ◽  
...  
Keyword(s):  
Transmembrane Helix ◽  
Energy Difference ◽  
Bk Channel ◽  
Voltage Sensor ◽  
K Channel ◽  
Open Probability ◽  
Channel Opening ◽  
Integration Node ◽  
Sensor Activation ◽  
Dynamics Simulations

Large-conductance Ca2+- and voltage-activated K+ channel (BK) open probability is enhanced by depolarization, increasing Ca2+ concentration, or both. These stimuli activate modular voltage and Ca2+ sensors that are allosterically coupled to channel gating. Here, we report a point mutation of a phenylalanine (F380A) in the S6 transmembrane helix that, in the absence of internal Ca2+, profoundly hinders channel opening while showing only minor effects on the voltage sensor active–resting equilibrium. Interpretation of these results using an allosteric model suggests that the F380A mutation greatly increases the free energy difference between open and closed states and uncouples Ca2+ binding from voltage sensor activation and voltage sensor activation from channel opening. However, the presence of a bulky and more hydrophobic amino acid in the F380 position (F380W) increases the intrinsic open–closed equilibrium, weakening the coupling between both sensors with the pore domain. Based on these functional experiments and molecular dynamics simulations, we propose that F380 interacts with another S6 hydrophobic residue (L377) in contiguous subunits. This pair forms a hydrophobic ring important in determining the open–closed equilibrium and, like an integration node, participates in the communication between sensors and between the sensors and pore. Moreover, because of its effects on open probabilities, the F380A mutant can be used for detailed voltage sensor experiments in the presence of permeant cations.

scholarly journals Transfer of Voltage Independence from a Rat Olfactory Channel to the Drosophila Ether-à-go-go K+ Channel

1997 ◽  
Vol 109 (3) ◽  
pp. 301-311 ◽  
Author(s):  
Chih-Yung Tang ◽  
Diane M. Papazian
Keyword(s):  
Cyclic Nucleotide ◽  
Voltage Sensor ◽  
K Channel ◽  
Voltage Range ◽  
Voltage Gated ◽  
Cyclic Nucleotide Gated Channels ◽  
Voltage Dependent ◽  
Relative Stabilization ◽  
Voltage Gated Ion Channels ◽  
S4 Segment

The S4 segment is an important part of the voltage sensor in voltage-gated ion channels. Cyclic nucleotide-gated channels, which are members of the superfamily of voltage-gated channels, have little inherent sensitivity to voltage despite the presence of an S4 segment. We made chimeras between a voltage-independent rat olfactory channel (rolf) and the voltage-dependent ether-à-go-go K+ channel (eag) to determine the basis of their divergent gating properties. We found that the rolf S4 segment can support a voltage-dependent mechanism of activation in eag, suggesting that rolf has a potentially functional voltage sensor that is silent during gating. In addition, we found that the S3-S4 loop of rolf increases the relative stability of the open conformation of eag, effectively converting eag into a voltage-independent channel. A single charged residue in the loop makes a significant contribution to the relative stabilization of the open state in eag. Our data suggest that cyclic nucleotide-gated channels such as rolf contain a voltage sensor which, in the physiological voltage range, is stabilized in an activated conformation that is permissive for pore opening.

S4 Charges Move Close to Residues in the Pore Domain during Activation in a K Channel

2001 ◽  
Vol 118 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Fredrik Elinder ◽  
Roope Männikkö ◽  
H. Peter Larsson
Keyword(s):  
Close Approach ◽  
Voltage Sensor ◽  
K Channel ◽  
Slow Inactivation ◽  
Transmembrane Voltage ◽  
Activated State ◽  
Ion Conducting ◽  
Voltage Gated Ion Channels ◽  
Modification Rate ◽  
Positively Charged

Voltage-gated ion channels respond to changes in the transmembrane voltage by opening or closing their ion conducting pore. The positively charged fourth transmembrane segment (S4) has been identified as the main voltage sensor, but the mechanisms of coupling between the voltage sensor and the gates are still unknown. Obtaining information about the location and the exact motion of S4 is an important step toward an understanding of these coupling mechanisms. In previous studies we have shown that the extracellular end of S4 is located close to segment 5 (S5). The purpose of the present study is to estimate the location of S4 charges in both resting and activated states. We measured the modification rates by differently charged methanethiosulfonate regents of two residues in the extracellular end of S5 in the Shaker K channel (418C and 419C). When S4 moves to its activated state, the modification rate by the negatively charged sodium (2-sulfonatoethyl) methanethiosulfonate (MTSES−) increases significantly more than the modification rate by the positively charged [2-(trimethylammonium)ethyl] methanethiosulfonate, bromide (MTSET+). This indicates that the positive S4 charges are moving close to 418C and 419C in S5 during activation. Neutralization of the most external charge of S4 (R362), shows that R362 in its activated state electrostatically affects the environment at 418C by 19 mV. In contrast, R362 in its resting state has no effect on 418C. This suggests that, during activation of the channel, R362 moves from a position far away (>20 Å) to a position close (8 Å) to 418C. Despite its close approach to E418, a residue shown to be important in slow inactivation, R362 has no effect on slow inactivation or the recovery from slow inactivation. This refutes previous models for slow inactivation with an electrostatic S4-to-gate coupling. Instead, we propose a model with an allosteric mechanism for the S4-to-gate coupling.

scholarly journals Biaryl sulfonamide motifs up- or down-regulate ion channel activity by activating voltage sensors

2018 ◽  
Vol 150 (8) ◽  
pp. 1215-1230 ◽  
Author(s):  
Sara I. Liin ◽  
Per-Eric Lund ◽  
Johan E. Larsson ◽  
Johan Brask ◽  
Björn Wallner ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Action Potential ◽  
Ion Channel ◽  
Potassium Channel ◽  
Voltage Sensor ◽  
Pharmaceutical Drugs ◽  
Voltage Gated ◽  
Channel Opening ◽  
Ion Conducting ◽  
Voltage Gated Ion Channels

Voltage-gated ion channels are key molecules for the generation of cellular electrical excitability. Many pharmaceutical drugs target these channels by blocking their ion-conducting pore, but in many cases, channel-opening compounds would be more beneficial. Here, to search for new channel-opening compounds, we screen 18,000 compounds with high-throughput patch-clamp technology and find several potassium-channel openers that share a distinct biaryl-sulfonamide motif. Our data suggest that the negatively charged variants of these compounds bind to the top of the voltage-sensor domain, between transmembrane segments 3 and 4, to open the channel. Although we show here that biaryl-sulfonamide compounds open a potassium channel, they have also been reported to block sodium and calcium channels. However, because they inactivate voltage-gated sodium channels by promoting activation of one voltage sensor, we suggest that, despite different effects on the channel gates, the biaryl-sulfonamide motif is a general ion-channel activator motif. Because these compounds block action potential–generating sodium and calcium channels and open an action potential–dampening potassium channel, they should have a high propensity to reduce excitability. This opens up the possibility to build new excitability-reducing pharmaceutical drugs from the biaryl-sulfonamide scaffold.

Small-Molecule Antagonists of CCR5 and CXCR4: A Promising New Class of Anti-HIV-1 Drugs

2004 ◽  
Vol 10 (17) ◽  
pp. 2041-2062 ◽  
Author(s):  
Christoph Seibert ◽  
Thomas Sakmar
Keyword(s):  
Small Molecule ◽  
New Class ◽  
Anti Hiv ◽  
Hiv 1

Recent Development of Small Molecule Glutaminase Inhibitors

2018 ◽  
Vol 18 (6) ◽  
pp. 432-443 ◽  
Author(s):  
Minsoo Song ◽  
Soong-Hyun Kim ◽  
Chun Young Im ◽  
Hee-Jong Hwang
Keyword(s):  
Small Molecule ◽  
Cell Metabolism ◽  
Phase 1 ◽  
Vital Role ◽  
Glutamine Metabolism ◽  
Inhibition Mechanism ◽  
Tumor Cell Growth ◽  
X Ray ◽  
New Class ◽  
Preclinical And Clinical Studies

Glutaminase (GLS), which is responsible for the conversion of glutamine to glutamate, plays a vital role in up-regulating cell metabolism for tumor cell growth and is considered to be a valuable therapeutic target for cancer treatment. Based on this important function of glutaminase in cancer, several GLS inhibitors have been developed in both academia and industry. Most importantly, Calithera Biosciences Inc. is actively developing the glutaminase inhibitor CB-839 for the treatment of various cancers, and it is currently being evaluated in phase 1 and 2 clinical trials. In this review, recent efforts to develop small molecule glutaminase inhibitors that target glutamine metabolism in both preclinical and clinical studies are discussed. In particular, more emphasis is placed on CB-839 because it is the only small molecule GLS inhibitor being studied in a clinical setting. The inhibition mechanism is also discussed based on X-ray structure studies of thiadiazole derivatives present in glutaminase inhibitor BPTES. Finally, recent medicinal chemistry efforts to develop a new class of GLS inhibitors are described in the hopes of providing useful information for the next generation of GLS inhibitors.

scholarly journals A small molecule compound with an indole moiety inhibits the main protease of SARS-CoV-2 and blocks virus replication

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shin-ichiro Hattori ◽  
Nobuyo Higashi-Kuwata ◽  
Hironori Hayashi ◽  
Srinivasa Rao Allu ◽  
Jakka Raghavaiah ◽  
...  
Keyword(s):  
Small Molecule ◽  
Covalent Bond ◽  
Amino Acid Residues ◽  
X Ray ◽  
Viral Breakthrough ◽  
Main Protease ◽  
Small Molecule Compound ◽  
Polar Interactions ◽  
High Concentrations

AbstractExcept remdesivir, no specific antivirals for SARS-CoV-2 infection are currently available. Here, we characterize two small-molecule-compounds, named GRL-1720 and 5h, containing an indoline and indole moiety, respectively, which target the SARS-CoV-2 main protease (Mpro). We use VeroE6 cell-based assays with RNA-qPCR, cytopathic assays, and immunocytochemistry and show both compounds to block the infectivity of SARS-CoV-2 with EC50 values of 15 ± 4 and 4.2 ± 0.7 μM for GRL-1720 and 5h, respectively. Remdesivir permitted viral breakthrough at high concentrations; however, compound 5h completely blocks SARS-CoV-2 infection in vitro without viral breakthrough or detectable cytotoxicity. Combination of 5h and remdesivir exhibits synergism against SARS-CoV-2. Additional X-ray structural analysis show that 5h forms a covalent bond with Mpro and makes polar interactions with multiple active site amino acid residues. The present data suggest that 5h might serve as a lead Mpro inhibitor for the development of therapeutics for SARS-CoV-2 infection.

scholarly journals Positioning and Guidance of the Voltage Sensor S4 Within the Omega/Gating-Pore in the Shaker K-Channel

2012 ◽  
Vol 102 (3) ◽  
pp. 532a
Author(s):  
Claudia Lehmann ◽  
Hansjakob Heldstab ◽  
Nikolaus G. Greeff
Keyword(s):  
Voltage Sensor ◽  
K Channel
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