Atomic determinants of state-dependent block of sodium channels by charged local anesthetics and benzocaine.

Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ont., Canada L8N 3Z5.
FEBS Letters (Impact Factor: 3.34). 12/2006; 580(26):6027-32. DOI: 10.1016/j.febslet.2006.10.035
Source: PubMed

ABSTRACT Molecular modeling predicts that a local anesthetic (LA) lidocaine binds to the resting and open Na(v)1.5 in different modes, interacting with LA-sensing residues known from experiments. Besides the major pathway via the open activation gate, LAs can reach the inner pore via a "sidewalk" between D3S6, D4S6, and D3P. The ammonium group of a cationic LA binds in the focus of the pore-helices macrodipoles, which also stabilize a Na(+) ion chelated by two benzocaine molecules. The LA's cationic group and a Na(+) ion in the selectivity filter repel each other suggesting that the Na(+) depletion upon slow inactivation would stabilize a LA, while a LA would stabilize slow-inactivated states.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The voltage dependent N-type Ca2+ channel (NCC) receptor was identified to have therapeutic potential for the treatment of neuropathic pain and stroke disease. The Ca2+ ion transport through the transmembrane influx is mainly dependent on the closing, opening, or intermediate state gating mechanism of NCC. Harnessing this dynamic gating mechanism at the structural level is an important and challenging physiological phenomenon. The three dimensional (3D) structure of this membrane receptor is not yet experimentally determined to understand its mechanism of action. Based on these observations, we have developed for the first time the structure of the closed state of the NCC receptor at the pore forming domains which mainly involve three transmembrane helices (TMhs) S5, P and S6. Hot-spot binding site residues of this receptor model were identified by molecular docking technique using amlodipine, cilnidipine and nifedipine compounds known to be potent Ca2+ channel antagonists. Further, the Ca2+ ion permeability and the hydrophobic gating mechanism provided better structural and functional insights on the NCC receptor. These results are in consonance with other Ca2+ channel receptors and would provide guidance for further biochemical investigations.
    Molecular Informatics. 09/2012; 31(9).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Antidepressants have many targets in the central nervous system. A growing body of data demonstrates the influence of antidepressants on glutamatergic neurotransmission. In the present work, we studied the inhibition of native Ca2+-permeable and Ca2+-impermeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in rat brain neurons by fluoxetine. The Ca2+-impermeable AMPA receptors in CA1 hippocampal pyramidal neurons were weakly affected. The IC50 value for the inhibition of Ca2+-permeable AMPA receptors in giant striatal interneurons was 43 ± 7 μm. The inhibition of Ca2+-permeable AMPA receptors was voltage dependent, suggesting deep binding in the pore. However, the use dependence of fluoxetine action differed markedly from that of classical AMPA receptor open-channel blockers. Moreover, fluoxetine did not compete with other channel blockers. In contrast to fluoxetine, its membrane-impermeant quaternary analog demonstrated all of the features of channel inhibition typical for open-channel blockers. It is suggested that fluoxetine reaches the binding site through a hydrophobic access pathway. Such a mechanism of block is described for ligands of sodium and calcium channels, but was never found in AMPA receptors. Molecular modeling suggests binding of fluoxetine in the subunit interface; analogous binding was proposed for local anesthetics in closed sodium channels and for benzothiazepines in calcium channels.
    European Journal of Neuroscience 12/2014; · 3.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The duration of anesthesia (related to protein binding of a drug) and the onset time (determined by the pKa) are important characteristics in assessment of local anesthetic agents. They are known to be affected by a number of factors. Early studies of antiarrhythmic diterpenoid alkaloids from plants Aconitum and Delphinium suggested that they possess local anesthetic activity due to their ability to suppress sodium currents of excited membranes. In this study we utilized toxicity, duration, and onset of action as endpoints to construct Quantitative Structure–Activity Relationship (QSAR) models for the series of 34 diterpenoid alkaloids characterized by local anesthetic activity using genetic algorithm-based multiple linear regression analysis/partial least squares and simplified molecular input line entry system (SMILES)-based optimal descriptors approach. The developed QSAR models correctly reflected factors that determine three endpoints 28 of interest. Toxicity correlates with descriptors describing partition and reactivity of compounds. The duration of anesthesia was encoded by the parameters defining the ability of 30 a compound to bind at the receptor site. The size and number of H-bond acceptor atoms were found to not favor the speed of onset, while topographic electronic descriptor demonstrated strong positive effect on it. SMILES-based optimal descriptors approach resulted in overall improvement of models. This approach was shown to be more sensitive to structural peculiarities of molecules than regression methods. The results clearly indicate that obtained QSARs are able to provide distinct rationales for compounds optimization with respect to particular endpoint.
    Journal of Environmental Science and Health Part C 07/2014; 32:1-26. · 2.50 Impact Factor


Available from