Both enantiomers of "para-hydroxymexiletine" (PHM), one of the main metabolites of mexiletine, were synthesized and fully characterized. Properties of (R)- and (S)-PHM, in terms of blocking potency and stereoselectivity on frog skeletal muscle Na(+) channels, were evaluated. The presence of a hydroxy group on the aryloxy moiety in the 4-position, as in PHM, reduced potency with respect to mexiletine in reducing I(Na max). However, PHM showed clear use-dependent behavior similar to that of mexiletine and, in contrast with what is observed with the parent compound, maintained its stereoselectivity during the use-dependent block. Chirality 16:72-78, 2004. 相似文献
The tetrodotoxin‐resistant (TTX‐R) voltage‐gated sodium channel Nav1.8 is predominantly expressed in peripheral afferent neurons, but in case of neuronal injury an ectopic and detrimental expression of Nav1.8 occurs in neurons of the CNS. In CNS neurons, Nav1.2 and Nav1.6 channels accumulate at the axon initial segment, the site of the generation of the action potential, through a direct interaction with the scaffolding protein ankyrin G (ankG). This interaction is regulated by protein kinase CK2 phosphorylation. In this study, we quantitatively analyzed the interaction between Nav1.8 and ankG. GST pull‐down assay and surface plasmon resonance technology revealed that Nav1.8 strongly and constitutively interacts with ankG, in comparison to what observed for Nav1.2. An ion channel bearing the ankyrin‐binding motif of Nav1.8 displaced the endogenous Nav1 accumulation at the axon initial segment of hippocampal neurons. Finally, Nav1.8 and ankG co‐localized in skin nerves fibers. Altogether, these results indicate that Nav1.8 carries all the information required for its localization at ankG micro‐domains. The constitutive binding of Nav1.8 with ankG could contribute to the pathological aspects of illnesses where Nav1.8 is ectopically expressed in CNS neurons.
Novel diphenylpiperazine derivatives were synthesized and evaluated for their inhibitory activity against T-type calcium channel by whole-cell patch clamp recordings on HEK293 cells. Among the test compounds, 2 and 3d were effective in decreasing the response to formalin in both the first and second phases and demonstrated antiallodynic effects in a rat model of neuropathic pain. 相似文献
In cardiac and skeletal myocytes, and in most neurons, the opening of voltage‐gated Na+ channels (NaV channels) triggers action potentials, a process that is regulated via the interactions of the channels’ intercellular C‐termini with auxiliary proteins and/or Ca2+. The molecular and structural details for how Ca2+ and/or auxiliary proteins modulate NaV channel function, however, have eluded a concise mechanistic explanation and details have been shrouded for the last decade behind controversy about whether Ca2+ acts directly upon the NaV channel or through interacting proteins, such as the Ca2+ binding protein calmodulin (CaM). Here, we review recent advances in defining the structure of NaV intracellular C‐termini and associated proteins such as CaM or fibroblast growth factor homologous factors (FHFs) to reveal new insights into how Ca2+ affects NaV function, and how altered Ca2+‐dependent or FHF‐mediated regulation of NaV channels is perturbed in various disease states through mutations that disrupt CaM or FHF interaction. 相似文献
FGF13 (FHF2), the major fibroblast growth factor homologous factor (FHF) in rodent heart, directly binds to the C-terminus of the main cardiac sodium channel, NaV1.5. Knockdown of FGF13 in cardiomyocytes induces slowed ventricular conduction by altering NaV1.5 function. FGF13 has five splice variants, each of which possess the same core region and C terminus but differing in their respective N termini. Whether and how these alternatively spliced N termini impart isoform-specific regulation of NaV1.5, however, has not been reported. Here, we exploited a heterologous expression to explore the specific modulatory effects of FGF13 splice variants FGF13S, FGF13U and FGF13YV on NaV1.5 function. We found these three splice variants differentially modulated NaV1.5 current density. Although steady-state activation was unaltered by any of the FGF13 isoforms (compared to control cells expressing Nav1.5 but not expressing FGF13), open-state fast inactivation and closed-state fast inactivation were markedly slowed, steady-state availability was significantly shifted toward the depolarizing direction, and the window current was increased by each of FGF13 isoforms. Most strikingly, FGF13S hastened the rate of NaV1.5 entry into the slow inactivation state and induced a dramatic slowing of recovery from inactivation, which caused a large decrease in current after either low or high frequency stimulation. Overall, these data showed the diversity of the roles of the FGF13 N-termini in NaV1.5 channel modulation and suggested the importance of isoform-specific regulation. 相似文献
Epilepsy is a common neurological disorder affecting approximately 1% of the population. Mutations in voltage‐gated sodium channels are responsible for several monogenic epilepsy syndromes. More than 800 mutations in the voltage‐gated sodium channel SCN1A have been reported in patients with generalized epilepsy with febrile seizures plus and Dravet syndrome. Heterozygous loss‐of‐function mutations in SCN1A result in Dravet syndrome, a severe infant‐onset epileptic encephalopathy characterized by intractable seizures, developmental delays and increased mortality. A common feature of monogenic epilepsies is variable expressivity among individuals with the same mutation, suggesting that genetic modifiers may influence clinical severity. Mice with heterozygous deletion of Scn1a (Scn1a+/?) model a number of Dravet syndrome features, including spontaneous seizures and premature lethality. Phenotype severity in Scn1a+/? mice is strongly dependent on strain background. On the 129S6/SvEvTac strain Scn1a+/? mice exhibit no overt phenotype, whereas on the (C57BL/6J × 129S6/SvEvTac)F1 strain Scn1a+/? mice exhibit spontaneous seizures and early lethality. To systematically identify loci that influence premature lethality in Scn1a+/? mice, we performed genome scans on reciprocal backcrosses. Quantitative trait locus mapping revealed modifier loci on mouse chromosomes 5, 7, 8 and 11. RNA‐seq analysis of strain‐dependent gene expression, regulation and coding sequence variation provided a list of potential functional candidate genes at each locus. Identification of modifier genes that influence survival in Scn1a+/? mice will improve our understanding of the pathophysiology of Dravet syndrome and may suggest novel therapeutic strategies for improved treatment of human patients. 相似文献
Activation and inactivation of ion channels involve volume changes from conformational rearrangements of channel proteins. These volume changes are highly susceptible to changes in ambient pressure. Depending on the pressure level, channel function may be irreversibly altered by pressure. The corresponding structural changes persist through the post-decompression phase. High-pressure applications are a useful tool to evaluate the pressure dependence as well as pressure limits for reversibility of such alterations. Mammalian cells are only able to tolerate much lower pressures than microorganisms. Although some limits for pressure tolerance in mammalian cells have been evaluated, the mechanisms of pressure-induced alteration of membrane physiology, in particular of channel function, are unknown. To address this question, we recorded fast inward sodium (I(Na)) and slowly activating L-type calcium (I(Ca)) currents in single mammalian muscle fibers in the post-decompression phase after a prolonged 3-h, high-pressure treatment of up to 20 MPa. I(Na) and I(Ca) peak amplitudes were markedly reduced after pressure treatment at 20 MPa. This was not from a general breakdown of membrane integrity as judged from in situ high-pressure fluorescence microscopy. Membrane integrity was preserved even for pressures as high as 35 MPa at least for pressure applications of shorter durations. Therefore, the underlying mechanisms for the observed amplitude reductions have to be determined from the activation (time-to-peak [TTP]) and inactivation (tau(dec)) kinetics of I(Na) and I(Ca). No major changes in I(Na) kinetics, but marked increases, both in TTP and tau(dec) for I(Ca), were detected after 20 MPa. The apparent molecular volume changes (activation volumes) deltaV(double dagger) for the pressure-dependent irreversible alteration of channel gating approached zero for Na+ channels. For Ca2+ channels, deltaV(double dagger) was very large, with approx 2.5-fold greater values for channel activation than inactivation (approx 210 A3). We conclude, that in skeletal muscle, high pressure differentially and irreversibly affects the gating properties and the density of functional Na+ and Ca2+ channels. Based on these results, a model of high pressure-induced alterations to the channel conformation is proposed. 相似文献
Several azaline B analogs (2-10) were synthesized and evaluated for their ability to antagonize GnRH in vitro and for duration of action in inhibiting luteinizing hormone secretion in a castrated male rat assay in vivo. Analogs, 8 (IC(50) = 1.85 nM), and 9 (IC(50) = 1.78 nM), are equipotent with azaline B (1, IC(50) = 1.36 nM) in vitro. Whereas 9 is short acting, 8 is as long acting as azaline B. Other analogs have IC(50) greater than 2.0 nM and are all short acting. 相似文献
Summary A simple model of the action of amiloride to block apical Na channels in the toad urinary bladder was tested. According to the model, the positively charged form of the drug binds to a site in the lumen of the channel within the electric field of the membrane. In agreement with the predictions of the model: (1) The voltage dependence of amiloride block was consistent with the assumption of a single amiloride binding site, at which about 15% of the transmembrane voltage is sensed, over a voltage range of ±160 mV. (2) The time course of the development of voltage dependence was consistent with that predicted from the rate constants for amiloride binding previously determined. (3) The ability of organic cations to mimic the action of amiloride showed a size dependence implying a restriction of access to the binding site, with an effective diameter of about 5 angstroms. In a fourth test, divalent cations (Ca, Mg, Ba and Sr) were found to block Na channels with a complex voltage dependence, suggesting that these ions interact with two or more sites. at least one of which may be within the lumen of the pore. 相似文献
The present study describes the synthesis, the characterization and the evaluation of some derivatives of N6-isopentenyladenosine on T24 human bladder carcinoma cells. In particular we have modified the hydroxyl groups in the ribose moiety, the position of the isopentenyl chain in the purine ring and the base moiety. The structures of the compounds were confirmed by standard studies of NMR, MS and elemental analysis. We here show that only two derivatives, 1-(3-methyl-2-butenylamino)-9-(3′-deoxy-β-d-ribofuranosyl)-purine hydrobromide and 2-amino-6-(3-methyl-2- butenylamino)-9-(β-d-ribofuranosyl)-purine, inhibit the growth of T24 cells, although to a lower extent than N6-isopentenyladenosine. We conclude that the integrity of ribosidic and purine moiety and the N6 position of the chain are essential for maintaining the antiproliferative activity. 相似文献
Several substituted phenoxy acetic acid derived pyrazolines were synthesized by the reaction between 2-{4-[3-(2,4-dihydroxyphenyl)-3-oxo-1-propenyl]-2-methoxyphenoxy} acetic acid and substituted acid hydrazides and were tested for their in vitro cytotoxicity and antiviral activity. None of the compounds showed any specific antiviral activity [50% antivirally effective concentration (EC50) ≥ 5-fold lower than minimum cytotoxic concentration]. The most cytotoxic of the series was 2-{4-[3-(2,4-dihydroxyphenyl)-1-(2-hydroxybenzoyl-4,5-dihydro-1H-5-pyrazolyl]-2-methoxyphenoxy}acetic acid (3j), with a minimum cytotoxic concentration of 0.16 μg/mL in human embryonic lung (HEL) cells. 相似文献
Neuronal sodium channels blockers interfere with ion flux and have been used for managing neuropathic pain, epilepsy, and cerebral ischemic disorders. In the current study, four groups of 2,4-diamino-1,3,5-triazine derivatives were synthesized and investigated for their neuronal sodium channels binding activity. 5-Aryl-1,3,5-triazaspiro[5.5]undeca-1,3-diene-2,4-diamines (4a–4j) were found to have the best neuronal sodium binding activity among the four groups of triazines evaluated. Derivatives 4a–4j blocked the sodium channels with IC50 values ranged from 4.0 to 14.7 μM. The result from this study showed that analogues of 2,4-diamino-1,3,5-triazines could be used as leads for the discovery of neuronal sodium channels blockers for managing central nervous system related disorders. 相似文献
Several substituted phenoxy acetic acid derived pyrazolines were synthesized by the reaction between 2-{4-[3-(2,4-dihydroxyphenyl)-3-oxo-1-propenyl]-2-methoxyphenoxy} acetic acid and substituted acid hydrazides and were tested for their in vitro cytotoxicity and antiviral activity. None of the compounds showed any specific antiviral activity [50% antivirally effective concentration (EC(50)) > or = 5-fold lower than minimum cytotoxic concentration]. The most cytotoxic of the series was 2-{4-[3-(2,4-dihydroxyphenyl)-1-(2-hydroxybenzoyl-4,5-dihydro-1H-5-pyrazolyl]-2-methoxyphenoxy}acetic acid (3(j)), with a minimum cytotoxic concentration of 0.16 microg/mL in human embryonic lung (HEL) cells. 相似文献
Sodium (Na+) is the major cation in extracellular space and, with its entry into cells, may act as a critical intracellular second messenger
that regulates many cellular functions. Through our investigations of mechanisms underlying the activity-dependent regulation
of N-methyl-d-aspartate (NMDA) receptors, we recently characterized intracellular Na+ as a possible signaling factor common to processes underlying the upregulation of NMDA receptors by non-NMDA glutamate channels,
voltage-gated Na+ channels, and remote NMDA receptors. Furthermore, although Ca2+ influx during the activation of NMDA receptors acts as a negative feedback mechanism that downregulates NMDA receptor activity,
Na+ influx provides an essential positive feedback mechanism to overcome Ca2+-induced inhibition, thereby potentiating both NMDA receptor activity and inward Ca2+ flow. NMDA receptors may be recruited to cause excitoxicity through a Na+-dependent mechanism. Therefore, the further characterization of mechanisms underlying the regulation of NMDA receptors by
intracellular Na+ is essential to understanding activity-dependent neuroplasticity in the nervous system. 相似文献
The voltage-gated sodium (Nav) channel is the molecular determinant of action potential in neurons. Protein-protein interactions (PPI) between the intracellular Nav1.6 C-tail and its regulatory protein fibroblast growth factor 14 (FGF14) provide an ideal and largely untapped opportunity for development of neurochemical probes. Based on a previously identified peptide FLPK, mapped to the FGF14:FGF14 PPI interface, we have designed and synthesized a series of peptidomimetics with the intent of increasing clogP values and improving cell permeability relative to the parental lead peptide. In-cell screening using the split-luciferase complementation (LCA) assay identified ZL0177 (13) as the most potent inhibitor of the FGF14:Nav1.6 channel complex assembly with an apparent IC50 of 11?μM. Whole-cell patch-clamp recordings demonstrated that ZL0177 significantly reduced Nav1.6-mediated transient current density and induced a depolarizing shift of the channel voltage-dependence of activation. Docking studies revealed strong interactions between ZL0177 and Nav1.6, mediated by hydrogen bonds, cation-π interactions and hydrophobic contacts. All together these results suggest that ZL0177 retains some key features of FGF14-dependent modulation of Nav1.6 currents. Overall, ZL0177 provides a chemical scaffold for developing Nav channel modulators as pharmacological probes with therapeutic potential of interest for a broad range of CNS and PNS disorders. 相似文献