Sodium channels are a critical component of electrical signaling in neurons. The availability of sodium channels determines neuronal electrical excitability. Slow inactivation (SI) regulates sodium channel availability. Our preliminary data demonstrate that the kinetics of SI is subject to modulation by sodium channel phosphorylation. Changes in the level of SI due to changes in channel phosphorylation is therefore a likely candidate by which neuronal excitability may be modulated by activation of receptors that trigger phosphorylation cascades. Events such as these accompany the cellular processes that underlie many normal neurological processes. Changes in sodium channel availability, and therefore neuronal excitability, also underlie diseases of excitability such as epilepsy. Our research, therefore, will elucidate fundamentally important mechanisms that control both physiological and pathophysiological processes in the brain through changes in electrical excitability. The long-term objective of this research is to determine the contribution of sodium channel SI to neuronal excitability.
The specific aims of this research proposal are to: (1) test the hypothesis, based on our preliminary results, that SI is modulated by activators of cyclic AMP-dependent phosphorylation via protein kinase A and by activators of diacylglycerol-dependent phosphorylation via protein kinase C, that phosphorylation-induced modulation of sodium channel SI occurs at identified consensus phosphorylation sites in the neuronal sodium channel, and that modulation varies as a function of co-expression with WTor mutant beta-1 subunit; (2) test the hypothesis that SI is modulated by CaM kinase II; (3) test the hypothesis that local anesthetics and anticonvulsants affect or mimic SI, and that this varies as a function of beta-1 subunit co-expression; test the hypothesis that pharmacological alterations of sodium channel gating are correlated with changes in gating currents and charge movement. In pursuit of these specific aims, we will record ionic and gating currents to measure the voltage dependence and rates of slow inactivation, as well as other biophysical properties, from rat brain sodium channels expressed in (1) HEK 293 cells using patch clamp and (2) Xenopus oocytes using cut-open oocyte voltage clamp.
|Groome, James R; Dice, Margaret C; Fujimoto, Esther et al. (2007) Charge immobilization of skeletal muscle Na+ channels: role of residues in the inactivation linker. Biophys J 93:1519-33|
|McCollum, Isabelle J; Vilin, Yuriy Y; Spackman, Elizabeth et al. (2003) Negatively charged residues adjacent to IFM motif in the DIII-DIV linker of hNa(V)1.4 differentially affect slow inactivation. FEBS Lett 552:163-9|
|Groome, James R; Fujimoto, Esther; Ruben, Peter C (2003) Negative charges in the DIII-DIV linker of human skeletal muscle Na+ channels regulate deactivation gating. J Physiol 548:85-96|
|Groome, James; Fujimoto, Esther; Walter, Lisa et al. (2002) Outer and central charged residues in DIVS4 of skeletal muscle sodium channels have differing roles in deactivation. Biophys J 82:1293-307|
|Groome, J R; Fujimoto, E; Ruben, P C (2000) The delay in recovery from fast inactivation in skeletal muscle sodium channels is deactivation. Cell Mol Neurobiol 20:521-7|
|Vilin, Y Y; Makita, N; George Jr, A L et al. (1999) Structural determinants of slow inactivation in human cardiac and skeletal muscle sodium channels. Biophys J 77:1384-93|
|Groome, J R; Fujimoto, E; George, A L et al. (1999) Differential effects of homologous S4 mutations in human skeletal muscle sodium channels on deactivation gating from open and inactivated states. J Physiol 516 ( Pt 3):687-98|
|Richmond, J E; Featherstone, D E; Hartmann, H A et al. (1998) Slow inactivation in human cardiac sodium channels. Biophys J 74:2945-52|
|Featherstone, D E; Fujimoto, E; Ruben, P C (1998) A defect in skeletal muscle sodium channel deactivation exacerbates hyperexcitability in human paramyotonia congenita. J Physiol 506 ( Pt 3):627-38|
|Richmond, J E; Featherstone, D E; Ruben, P C (1997) Human Na+ channel fast and slow inactivation in paramyotonia congenita mutants expressed in Xenopus laevis oocytes. J Physiol 499 ( Pt 3):589-600|
Showing the most recent 10 out of 17 publications