sodiumionchannel：鈉離子通道(已修改)
2025-01-24 08:36 本頁(yè)面
【正文】 Sodium Channel Structure, Function, Gating and Involvement in Disease David R. Marks, . An Overview ? Sodium Channel Structure Current theory and Types of Na+ Channels ? Sodium Channel Function Current theory of inactivation Modulation Pharmacology Activation An Overview Cont’d ? Article 2 – Na+ Channel Gating ? Article 1 Na+ Channels and Neurodegenerative Disease ? Article 3 – Na+ channel mutation and physiology Sodium Channels Structure ? Composed of α, β1 and β2 subunits, but the large αsubunits carries most of the functional properties ? 4 repeated motifs, each with 6 transmembrane domains ? All linked together ? Contain 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 Cartoon representation of the “typical” voltageactivated sodium channel Types Of Na+ Channels ? Voltage gated – Changes in membrane polarity open the channel ? Ligand gated (nicotinic acetylcholine receptor) – Ligand binding alters channel/receptor conformation and opens the pore ? Mechanically gated (stretch receptor) – Physical torsion or deformation opens the channel pore Sodium Channels Function ? Play a central role in the transmission of action potentials along a nerve ? Can be in different functional states (3) A resting state when it can respond to a depolarizing voltage changes Activated, when it allows flow of Na+ ions through the Inactivated, when subjected to a “suprathreshold” potential, the channel will not open The theory is that the inactivation gate “swings” shut, turning off the channel Please Keep In Mind ? The structure of the Na+ channel is not 100% solved, hence a “working model” is drawn based on biophysical, pharmacological, physiological and molecular assays
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