Voltage-gated sodium channels

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Voltage-gated sodium channels Xiao Yu Institute of Physiology Shandong University, School of Medicine 2012-11-10

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Voltage-gated sodium channels. Xiao Yu Institute of Physiology Shandong University, School of Medicine 2012-11-10. Sodium channel genes are latecomers to the 6TM Family. (Zakon HH, PNAS 2012). Sodium Channels - Structure. - PowerPoint PPT Presentation

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  • Voltage-gated sodium channelsXiao YuInstitute of PhysiologyShandong University, School of Medicine2012-11-10

  • Sodium channel genes are latecomers to the 6TM Family(Zakon HH, PNAS 2012)

  • Sodium Channels - StructureComposed of , -1 and -2 subunits, but the large -subunits carries most of the functional properties 4 repeated motifs, each with 6 transmembrane domainsAll linked togetherContain a voltage sensor/ligand binding domain (method of activation)The hydrophobic S4 segment (voltage sensor) is found in all voltage gated Na+ channels and is absent in ligand gated Na+ channels Selectivity filter (shell of hydration)Inactivation gate

  • Human voltage-gated sodium channels: Genes and proteins

  • Outline1. Physiological studies

    2. Pharmacological studies

    3. Biochemical studies

    4. Pathological and further studies

  • Ion channelsGates Voltage gated sodium channels (VGSC)

  • Physiological properties of VGSCs: activation, inactivation, recovery (Neuroscience: Exploring the Brain 2007)

  • Voltage-gated sodium channel: activation(Lou, et al, J Physiol 2003)

  • Hyperpolarization is necessary for depolarization-induced sodium currents in pancreatic beta cells

  • Steady-state inactivation/availability of VGSC

  • Kinetics of inactivation differs in b cells and ACCs

  • Time course of VGSC recovery: b cells are slower than ACCs

  • Summary I1. VGSC currents are voltage-gated inward currents.

    2. VGSCs perform fast activation and fast inactivation.

    3. Inactivation and recovery of VGSCs are diverse.

  • Tetrodotoxin - PufferfishSaxitoxin - Paralytic Shellfish PoisoningSoong, T.W. and B.Venkatesh.Trends Genetics, 22; 621-626 (2006)

  • Soong, T.W. and B.Venkatesh.Trends Genetics, 22; 621-626 (2006)

    TTX and STX- Molecular Mimics

  • Soong, T.W., and B. Venkatesh, Trends Genetics, 22; 621-626 (2006)VGSC and binding site for TTX

  • blocking by TTX (a) and STX (b) Scale bars, 1 nA and 1 ms. Bricelj, V.M. et al., Nature, 434; 763-767 (2005)Blocking of WT and mutant VGSCs by TTX and STX

  • TTX-resistant sodium channel (Nav1.8) No effect onthe persistent TTX-R Na current Nav1.9)Ekberg,J et al, PNAS (2006) O-conotoxin (MrVIB) selectively blocks Nav1.8 ---- TTX-resistant current in DRG

  • Summary II

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    TTXCTXTTXCTXTTXCTX

  • Sodium channels co-immunoprecipitate with RPTPbIncrease postnatallyembryogenesisConstant levelsRatcliffe CF, et al. Nature Neuroscience 2000

  • Sodium channel a subunits are tyrosine phosphorylated

  • Phosphatase-Sodium channel-Kinase

  • Functional effects of BDNF on Nav1.2 channels(Ahn, et al, JNS 2007)

  • (Src family kinases)SFKs interact with and phosphorylate Nav1.2(Ahn, et al, JNS 2007)

  • SH3 domain mediates the interaction between Nav1.2 and Fyn(Beacham et al JNS,2007)

  • Summary III1. VGSC are regulated with phosphatase and kinase

    2. Biochemical studies and physiological studies on VGSCs are put together.

  • Anosmia ---- loss of smell ()

  • Channelopathy

  • Pain and Nav1.7congenitalinsensitivity to pain erythromelalgiaPrimary erythromelalgiaPE Paroxysmal extreme pain disorder

  • More SNPsHyperPPPMC,PAM

  • Na+translationassemblytargetingkineticspermeationWhat can go wrong?Expression models cRNA or cDNA injection into Xenopus oocytes Transfection of mammalian cell cultureMethods Electrophysiology Pharmacology Immunocytochemistry Fluorescence imaging of tagged proteins

  • Take home messages1. Na channels physiological properties are diverse and crucial.2. Na channels are regulated by drugs, enzymes and single mutation of themselves.

  • Thanks!

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