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1.
Kwon Moo Park Sun-Don Kim Jin Bong Park Sung-Jong Hong Pan Dong Ryu 《The Korean journal of parasitology》2021,59(4):329
Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (Po) was ~0.3 in the voltage range of −60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl− to K+ (PCl/PK) was ~0.5 and PNa/PK was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and PCl/PK was 8.6±0.8. Po was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further. 相似文献
2.
Anthony J. Roecker Melissa Egbertson Kristen L.G. Jones Robert Gomez Richard L. Kraus Yuxing Li Amy Jo Koser Mark O. Urban Rebecca Klein Michelle Clements Jacqueline Panigel Christopher Daley Jixin Wang Eleftheria N. Finger John Majercak Vincent Santarelli Irene Gregan Matthew Cato Mark E. Layton 《Bioorganic & medicinal chemistry letters》2017,27(10):2087-2093
The voltage-gated sodium channel Nav1.7 is a genetically validated target for the treatment of pain with gain-of-function mutations in man eliciting a variety of painful disorders and loss-of-function mutations affording insensitivity to pain. Unfortunately, drugs thought to garner efficacy via Nav1 inhibition have undesirable side effect profiles due to their lack of selectivity over channel isoforms. Herein we report the discovery of a novel series of orally bioavailable arylsulfonamide Nav1.7 inhibitors with high levels of selectivity over Nav1.5, the Nav isoform responsible for cardiovascular side effects, through judicious use of parallel medicinal chemistry and physicochemical property optimization. This effort produced inhibitors such as compound 5 with excellent potency, selectivity, behavioral efficacy in a rodent pain model, and efficacy in a mouse itch model suggestive of target modulation. 相似文献
3.
A. V. Zholos T. B. Bolton A. V. Dresvyannikov M. V. Kustov V. V. Tsvilovskii M. F. Shuba 《Neurophysiology》2004,36(5-6):398-406
Acetylcholine, the main neurotransmitter of the parasympathetic nervous system, depolarizes various smooth muscles and initiates their contraction via activating muscarinic cholinergic receptors. In most visceral smooth muscle tissues, such as the gastrointestinal tract, airways, and the urinary system, muscarinic receptors are comprised of predominant M2 (about 80%)and minor M3 (about 20%) subtypes. Cholinergic excitation is generally mediated by the opening of ion channels selective for monovalent cations (under physiological conditions, Na+ and K+); among them the cationic channel of an about 60 pS unitary conductance has been recently identified as the main target for acetylcholine action. The signal transduction leading to channel opening is very complex and involves activation of Go protein (an M2 effect), activation of phospholipase C (an M3 effect), and [Ca2+]i and voltage dependence of channel opening. These multiple signaling pathways were difficult to reconcile with the channel gating mechanisms since only a simplified two-state channel mechanism (e.g., one open and one shut state) was until recently available. However, our recent studies of channel gating in isolated outside-out membrane patches revealed a greater complexity. Thus, this cationic channel shows transitions between at least eight states, four open and four shut, with strong connections between adjacent shut and open states. Therefore, four pairs of connected states have been identified, which showed voltage-dependent transitions in each pair of shut/open states. Since the membrane potential did not affect the relative proportions between the pairs, we have assumed that these effects are controlled by ligands that bind to the channel and, thus, stabilize its various open conformations. In this work, direct tests of the above hypothesis have been performed, and their results showed that spontaneous brief channel gating exists in the absence of receptor or G-protein activation, which is strongly voltage-dependent (increasing at depolarized potentials). Furthermore, this activity was potentiated at a low agonist concentration, while channel openings generally remained brief. An increasing receptor occupancy by the agonist produced long channel openings, indicating a shift of gating towards a long open/brief shut pair of the channel states. These findings are interpreted in the context of the established signal transduction pathways;certain predictions for the whole-cell current are also examined.Neirofiziologiya/Neurophysiology, Vol. 36, Nos. 5/6, pp. 446–454, September–December, 2004.This revised version was published online in April 2005 with a corrected cover date and copyright year. 相似文献
4.
《International journal for parasitology》2023,53(8):427-434
The parasitic flatworm ion channel, TRPMPZQ, is a non-selective cation channel that mediates Ca2+ entry and membrane depolarization when activated by the anthelmintic drug, praziquantel (PZQ). TRPMPZQ is conserved in all platyhelminth genomes scrutinized to date, with the sensitivity of TRPMPZQ in any particular flatworm correlating with the overall sensitivity of the worm to PZQ. Conservation of this channel suggests it plays a role in flatworm physiology, but the nature of the endogenous cues that activate this channel are currently unknown. Here, we demonstrate that TRPMPZQ is activated in a ligand-independent manner by membrane stretch, with the electrophysiological signature of channel opening events being identical whether evoked by negative pressure, or by PZQ. TRPMPZQ is therefore a multimodal ion channel gated by both physical and chemical cues. The mechanosensitivity of TRPMPZQ is one route for endogenous activation of this ion channel that holds relevance for schistosome physiology given the persistent pressures and mechanical cues experienced throughout the parasite life cycle. 相似文献
5.
Single IKCa channels of human erythrocytes were studied with the patch-clamp technique to define their modulation by endogenous protein kinase C (PKC). The perfusion of the cytoplasmic side of freshly excised patches with the PKC activator, phorbol 12-myristate 13-acetate (PMA), inhibited channel activity. This effect was blocked by PKC19-31, a peptide inhibitor specific for PKC. Similar results were obtained by perfusing the membrane patches with the structurally unrelated PKC activator 1-oleoyl-2-acetylglycerol (OAG). Blocking of this effect was induced by perfusion with PKC19-31 or chelerythrine. Channel activity was not inhibited by the PMA analog 4α-phorbol 12,13-didecanoate (4αPDD), which has no effect on PKC. Activation of endogenous cAMP-dependent protein kinase (PKA), which is known to up-modulate IKCa channels, restored channel activity previously inhibited by OAG. The application of OAG induced a reversible reduction of channel activity previously up-modulated by the activation of PKA, indicating that the effects of the two kinases are commutative, and antagonistic. Kinetic analysis showed that down-regulation by PKC mainly changes the opening frequency without significantly affecting mean channel open time and conductance. These results provide evidence that an endogenous PKC down-modulates the activity of native IKCa channels of human erythrocytes. Our results show that PKA and PKC signal transduction pathways integrate their effects, determining the open probability of the IKCa channels. 相似文献
6.
7.
SYNOPSIS. The inter- and intralamellar types of Henneguya exilis Kudo (Myxosporida) infections from channel catfish are similar in spore structure and sporogenesis, but differ in the structure of their plasmodium wall and surface coat and in their relationship with the host cells. The 2 clinical types differ also in the sites of development and growth patterns of plasmodia within a gill filament. Interlamellar plasmodia are limited by 2 outer unit membranes which give rise to both single-and double-membraned pinocytic canals. Intralamellar plasmodia are limited by a single outer unit membrane which gives rise to single-membraned pinocytic canals. Interlamellar plasmodia are covered by a fine granular coat of highly variable thicknesses; in some regions there is direct contact between the parasite and cells of the host. There is some evidence that host cell cytoplasm as well as interstitial material are taken in by interlamellar plasmodia. In contrast, intralamellar plasmodia are covered by a fine granular coat of almost uniform thickness, which prevents direct contact between the parasite and cells of the host; probably only interstitial material is taken by these plasmodia. 相似文献
8.
Ion channels exhibit stochastic conformational changes determining their gating behavior. In addition, the process of protein turnover leads to a natural variability of the number of membrane and gap junctional channels. Nevertheless, in computational models, these two aspects are scarcely considered and their impacts are largely unknown. We investigated the effects of stochastic current fluctuations and channel distributions on action potential duration (APD), intercellular conduction delays (ICDs) and conduction blocks using a modified ventricular cell model (Rudy et al.) with Markovian formulations of the principal ion currents (to simulate their stochastic open-close gating behavior) and with channel counts drawn from Poisson distributions (to simulate their natural variability). In single cells, APD variability (coefficient of variation: 1.6% at BCL=1000 ms) was essentially caused by stochastic channel gating of IKs, persistent INa and ICa,L. In cell strands, ICD variability induced by stochastic channel gating and Poissonian channel distributions was low under normal conditions. Nonetheless, at low intercellular coupling levels, Poissonian gap junctional channel distribution resulted in a large ICD variability (coefficient of variation >20%), highly heterogeneous conduction patterns and conduction blocks. Therefore, the stochastic behavior of current fluctuations and channel distributions can contribute to the heterogeneity of conduction patterns and to conduction block, as observed previously in experiments in cardiac tissue with altered intercellular coupling. 相似文献
9.
Summary The mammalian urinary bladder contains in its apical membrane and cytoplasmic vesicles, a cation-selective channel or activating fragment which seems to partition between the apical membrane and the luminal (or vesicular space). To determine whether it is an activating fragment or whole channel, we first demonstrate that solution known to contain this moiety can be concentrated and when added back to the bladder causes a conductance increase, with a percent recovery of 139±25%. Next, we show that using tip-dip bilayer techniques (at 21°C) and a patch-clamp recorder, the addition of concentrated solution resulted in the appearance of discrete current shots, consistent with the incorporation of a channel (as opposed to an activating fragment) into the bilayer. The residency time of the channel in the bilayer was best described by the sum of two exponentials, suggesting that the appearance of the channel involves an association of the channel with the membrane before insertion. The channel is cation selective and more conductive to K+ than Na+ (by a factor of 1.6). It has a linearI–V relationship, but a singlechannel conductance that saturates as KCl concentration is raised. This saturation is best described by the Michaelis-Menten equation with aK
m of 160mm KCl and aG
max of 20 pS. The kinetics of the channel are complex, showing at least two open and two closed states.Since the characteristics of this channel are similar to a channel produced by the degradation of amiloride-sensitive Na+ channels by the proteolytic enzyme kallikrein (which is released by the cortical collecting duct of the kidney), we suggest that this channel then is not synthesized by the cell but is rather a degraded form of the epithelial Na+ channel. 相似文献
10.
Samantha Hover Barnabas King Bradley Hall Eleni-Anna Loundras Hussah Taqi Janet Daly Mark Dallas Chris Peers Esther Schnettler Clive McKimmie Alain Kohl John N. Barr Jamel Mankouri 《The Journal of biological chemistry》2016,291(7):3411-3422
Bunyaviruses are considered to be emerging pathogens facilitated by the segmented nature of their genome that allows reassortment between different species to generate novel viruses with altered pathogenicity. Bunyaviruses are transmitted via a diverse range of arthropod vectors, as well as rodents, and have established a global disease range with massive importance in healthcare, animal welfare, and economics. There are no vaccines or anti-viral therapies available to treat human bunyavirus infections and so development of new anti-viral strategies is urgently required. Bunyamwera virus (BUNV; genus Orthobunyavirus) is the model bunyavirus, sharing aspects of its molecular and cellular biology with all Bunyaviridae family members. Here, we show for the first time that BUNV activates and requires cellular potassium (K+) channels to infect cells. Time of addition assays using K+ channel modulating agents demonstrated that K+ channel function is critical to events shortly after virus entry but prior to viral RNA synthesis/replication. A similar K+ channel dependence was identified for other bunyaviruses namely Schmallenberg virus (Orthobunyavirus) as well as the more distantly related Hazara virus (Nairovirus). Using a rational pharmacological screening regimen, two-pore domain K+ channels (K2P) were identified as the K+ channel family mediating BUNV K+ channel dependence. As several K2P channel modulators are currently in clinical use, our work suggests they may represent a new and safe drug class for the treatment of potentially lethal bunyavirus disease. 相似文献
11.
Yoni Haitin Reuven Wiener Dana Shaham Asher Peretz Enbal Ben‐Tal Cohen Liora Shamgar Olaf Pongs Joel A Hirsch Bernard Attali 《The EMBO journal》2009,28(14):1994-2005
Voltage‐gated K+ channels co‐assemble with auxiliary β subunits to form macromolecular complexes. In heart, assembly of Kv7.1 pore‐forming subunits with KCNE1 β subunits generates the repolarizing K+ current IKS. However, the detailed nature of their interface remains unknown. Mutations in either Kv7.1 or KCNE1 produce the life‐threatening long or short QT syndromes. Here, we studied the interactions and voltage‐dependent motions of IKS channel intracellular domains, using fluorescence resonance energy transfer combined with voltage‐clamp recording and in vitro binding of purified proteins. The results indicate that the KCNE1 distal C‐terminus interacts with the coiled‐coil helix C of the Kv7.1 tetramerization domain. This association is important for IKS channel assembly rules as underscored by Kv7.1 current inhibition produced by a dominant‐negative C‐terminal domain. On channel opening, the C‐termini of Kv7.1 and KCNE1 come close together. Co‐expression of Kv7.1 with the KCNE1 long QT mutant D76N abolished the K+ currents and gated motions. Thus, during channel gating KCNE1 is not static. Instead, the C‐termini of both subunits experience molecular motions, which are disrupted by the D76N causing disease mutation. 相似文献
12.
Sharan K Bagal Brian E Marron Robert M Owen R Ian Storer Nigel A Swain 《Channels (Austin, Tex.)》2015,9(6):360-366
Voltage-gated sodium (NaV) channels are a family of transmembrane ion channel proteins. They function by forming a gated, water-filled pore to help establish and control cell membrane potential via control of the flow of ions between the intracellular and the extracellular environments. Blockade of NaVs has been successfully accomplished in the clinic to enable control of pathological firing patterns that occur in a diverse range of conditions such as chronic pain, epilepsy, and cardiac arrhythmias. First generation sodium channel modulator drugs, despite low inherent subtype selectivity, preferentially act on over-excited cells which reduces undesirable side effects in the clinic. However, the limited therapeutic indices observed with the first generation demanded a new generation of sodium channel inhibitors. The structure, function and the state of the art in sodium channel modulator drug discovery are discussed in this chapter. 相似文献
13.
The effects of SK&F 96365, a blocker of the receptor-operated Ca2+ channel, on contractilities and the Na+ channel of mouse diaphragm were studied. SK&F 96365 (10–50 µM) reversibly inhibited twitches, tetanic contractions and muscle and nerve action potentials. The IC50 was 17–24 µM. The inward Na+ current was suppressed and its recovery from inactivations delayed. Crotamine, a peptide toxin that binds to neurotoxin receptor site 3 of the muscle Na+ channel, enhanced the inhibitory effects of SK&F 96365 and reduced the IC50 to about 4 µM. Veratridine had similar effects, although it was less effective than crotamine. On the other hand, the crotamine-induced membrane depolarizations and spontaneous discharges of muscle action potentials were inhibited by SK&F 96365 noncompetitively. The inhibitory effects of tetrodotoxin and tetracaine were additive with those of SK&F 96365 but were enhanced slightly by crotamine. The results suggested that SK&F 96365 acts on a distinct site and blocks the Na+ channel of excitable membranes at a concentration range that inhibits the receptor-operated calcium channel. 相似文献
14.
Characterization of a 25-pS nonselective cation channel in a cultured secretory epithelial cell line
Summary We have studied a 25-pS nonselective cation channel from the apical membranes of cell line ST885, derived from neonatal mouse mandibular glands. Its Cl– permeability was not significantly different from zero. The permeabilities (relative to Na+) for inorganic cations were NH
4
+
(1.87)>K+(1.12)>Li+ (1.02)>Na+(1)>Rb+(0.81)>Mg2+(0.07)>Ca2+(0.002), and for organic cations, guanidinium (1.61)4-aminopyridine (0.66)>diethylamine (0.54)>piperazine (0.25)>Tris (0.18)>N-methylglucamine (0.12). The Tris and N-methylglucamine permeabilities differed significantly from zero. Fitting the Renkin equation indicated that the channel had an equivalent pore radius of 0.49 nm. The channel was activated by Ca2+ on the cytosolic surface (>0.1 mmol/liter) with a Hill coefficient of 1.2; it was also activated by depolarization. Open- and closed-time histograms indicated that it had at least two open and two closed states. The channel was blocked by cytosolic AMP or ATP (0.1 mmol/liter). It was also blocked by the Cl– channel blocker, diphenylamine-2-carboxylate (DPC; 0.1 mmol/liter), applied to the extracellular but not the cytosolic surface. 4-Aminopyridine, which permeated the channel when applied to the extracellular surface, blocked it when applied in low concentrations (5 mmol/liter) to the cytosolic surface. Quinine (0.1 mmol/liter) blocked from both the extracellular and cytosolic surfaces, blockade from either side being enhanced by depolarization. The channel was held open by application of SITS (0.1 mmol/liter) to the cytosolic surface. The channel shows striking similarities to the nicotinic acetylcholine receptor channel,viz., both channel types are abnormally permeable to 4-aminopyridine applied externally, and their selectivity sequences for inorganic ions are similar and for organic cations are identical. 相似文献
15.
《Journal of molecular biology》2022,434(19):167789
Regulation of pancreatic KATP channels involves orchestrated interactions of their subunits, Kir6.2 and SUR1, and ligands. Previously we reported KATP channel cryo-EM structures in the presence and absence of pharmacological inhibitors and ATP, focusing on the mechanisms by which inhibitors act as pharmacological chaperones of KATP channels (Martin et al., 2019). Here we analyzed the same cryo-EM datasets with a focus on channel conformational dynamics to elucidate structural correlates pertinent to ligand interactions and channel gating. We found pharmacological inhibitors and ATP enrich a channel conformation in which the Kir6.2 cytoplasmic domain is closely associated with the transmembrane domain, while depleting one where the Kir6.2 cytoplasmic domain is extended away into the cytoplasm. This conformational change remodels a network of intra- and inter-subunit interactions as well as the ATP and PIP2 binding pockets. The structures resolved key contacts between the distal N-terminus of Kir6.2 and SUR1′s ABC module involving residues implicated in channel function and showed a SUR1 residue, K134, participates in PIP2 binding. Molecular dynamics simulations revealed two Kir6.2 residues, K39 and R54, that mediate both ATP and PIP2 binding, suggesting a mechanism for competitive gating by ATP and PIP2. 相似文献
16.
Keiji Naruse Qiong-Yao Tang 《Biochemical and biophysical research communications》2009,385(4):634-568
We previously reported that SAKCA, a stretch-activated, large-conductance, calcium- and voltage-activated potassium (BKCa) channel is present in chick embryonic heart. Here, we cloned SAKCA and identified that Stress-Axis Regulated Exon (STREX) is responsible for the stretch sensitivity. Single patch-clamp recordings from CHO cells transfected with the cloned SAKCA showed stretch sensitivity, whereas deletion of the STREX insert diminished the stretch sensitivity of the channel. Sequence analysis revealed that the ERA 672-674 sequence of the STREX is indispensable for channel stretch sensitivity and single amino acid substitution from Ala674 to Thr674 completely eliminated the stretch sensitivity. Co-expression of chick STREX-EGFP and SAKCA in CHO cells, induced a strong GFP signal in the cell membrane and inhibited the stretch sensitivity significantly. These results suggest that SAKCA senses membrane tension through an interaction between STREX and submembranous components. 相似文献
17.
《Bioorganic & medicinal chemistry》2020,28(18):115655
Structural modifications of the neuronal calcium channel blocker MONIRO-1, including constraining the phenoxyaniline portion of the molecule and replacing the guanidinium functionality with tertiary amines, led to compounds with significantly improved affinities for the endogenously expressed CaV2.2 channel in the SH-SY5Y neuroblastoma cell line. These analogues also showed promising activity towards the CaV3.2 channel, recombinantly expressed in HEK293T cells. Both of these ion channels have received attention as likely targets for the treatment of neuropathic pain. The dibenzoazepine and dihydrobenzodiazepine derivatives prepared in this study show an encouraging combination of neuronal calcium ion channel inhibitory potency, plasma stability and potential to cross the blood–brain-barrier. 相似文献
18.
We investigated the effects of internal pH on Ca-activated, nucleotide-inhibited nonselective cation channels in the basolateral membranes of mouse collecting tubules, using the inside-out variant of the patch clamp technique. pH modulated the channel open probability (P o ), giving a bell-shaped curve peaking at pH 6.8/7.0: P o at pH 6.0 was 11±6% of P o at pH 7.2 and 32 ±7% at pH 8.0. The open and closed time distributions, best fitted to the sum of two exponentials, were differently sensitive to acid and alkaline conditions. Low pH reduced the short and long open times to 38 and 24% of their pH 7.2 values, while high pH produced a 4-fold increase in the long closed time. As previously reported, 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid (SITS) induced a quasi-permanent opening of the channel. The inhibition of the channel produced by high pH disappeared in the presence of SITS, while the inhibition produced by low pH was unaffected. These results suggest that the pH dependence of the channel is due to two separate mechanisms. pH was without effect on the ATP-evoked inhibition of the channel, while high pH profoundly reduced the steepness of the AMP inhibition curve, without altering the half-maximal inhibitory AMP concentration. 相似文献
19.
An anion channel of sarcoplasmic reticulum incorporated into planar lipid bilayers: Single-channel behavior and conductance properties 总被引:2,自引:0,他引:2
Summary An anion channel of sarcoplasmic reticulum vesicle has been incorporated into planar lipid bilayers by means of a fusion method and its basic properties were investigated. Analysis of fusion processes suggested that one SR vesicle contained approximately one anion channel. The conductance of this channel has several substates and shows a flickering behavior. The occupation probability of each substate was voltage dependent, which induced an inward rectification of macroscopic currents. Further, the anion channel was found to have the following properties. (1) The single-channel conductance is about 200 pS at 100mm Cl–. (2) The channel does not select among monovalent anions but SO
4
2–
hardly permeates through the channel. (3) SO
4
2–
added to thecis side (the side to which SR vesicles were added) inhibits Cl– current competitively in a voltage-dependent manner. (4) An analysis of this voltage dependence suggests that the binding site of SO
4
2–
is located at about 36% of the way across the channel from thecis entrance. 相似文献
20.
Fredrick H. Bahls Raj Lartius Louis-Eric Trudeau Robert T. Doyle Yu Fang Derrick Witcher Kevin Campbell Philip G. Haydon 《Developmental neurobiology》1998,35(2):198-208
The developmental regulation of the N-type calcium channel during synaptogenesis was studied using cultured rat hippocampal neurons to elucidate the roles of extrinsic versus intrinsic cues in the expression and distribution of this channel. Prior to synapse formation, α1B and β3 subunits of the N-type calcium channel were distributed diffusely throughout neurites, growth cones, and somata. As synaptogenesis proceeded, the subunit distributions became punctate and colocalized with the synaptic vesicle protein synaptotagmin. Isolated neurons were also examined to test for the requirement of extrinsic cues that control N-type calcium channel expression and distribution. These neurons expressed N-type calcium channel subunits, but their distributions remained diffuse. Functional ω-conotoxin GVIA-sensitive channels were expressed in isolated neurons, although the distribution of α1B subunits was diffuse. The distribution of the α1B subunit and synaptotagmin only became punctate when neuron-neuron contact was allowed. Thus, the expression of functional N-type calcium channels is the result of an intrinsic program while extrinsic regulatory cues mediated by neuron-neuron contact are required to control their distribution during synaptogenesis. © 1998 John Wiley & Sons, Inc. J Neurobiol 35: 198–208, 1998 相似文献