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Ion channel receptors

Manifestation of Novel Social Challenges of the European Union in the Teaching Material of Medical Biotechnology Master’s P rogrammes at the University of Pécs and at the University of Debrecen Identification number : TÁMOP-4.1.2-08/1/A-2009-0011.

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Ion channel receptors

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  1. Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat theUniversity of Pécs and at the University of Debrecen Identificationnumber: TÁMOP-4.1.2-08/1/A-2009-0011

  2. Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat theUniversity of Pécs and at the University of Debrecen Identification number: TÁMOP-4.1.2-08/1/A-2009-0011 Tímea Berki and Ferenc Boldizsár Signaltransduction Ion channelreceptors

  3. Ion channel receptors • 1Cys-loop receptors:pentameric structure, 4 transmembrane (TM) regions/subunit • Acetylcholin (Ach) Nicotinic R – Na+ channel • GABAA, GABAC, Glycine – Cl- channels (inhibitory role in CNS) • 2Glutamate-activated cationic channels: (excitatory role in CNS),tetramericstucture, 3 TM regions/subunit • eg. iGlu • 3ATP-gated channels: 3 homologous subunits, 2 TM regions/subunit • eg. P2X purinoreceptor

  4. Cys-loopion-channelreceptors Pore C C N N N N N C C C TM 1 TM 2 TM 3 TM 4 b a Receptor type GABAA GABAC Glycine g p2 p1 a b Subunitdiversity a1-4, b a1-6, b1-3, g1-3, d,e,k, and q p1-3

  5. Vertebrate anionicCys-loop receptors

  6. Vertebrate cationicCys-loop receptors

  7. Ionotropic glutamate receptors

  8. Nicotinic Ach receptor • Pore formed from 5 subunits: 2a, b, g, d • Opening: the 2a units are distorted • Desensitization: in the open conformation the b, g, d subunits become phosphorylated by Protein kinase A and C Top Front

  9. Common neurotransmitters

  10. Synapsebetweentwoneurons - neurotransmission Presynaptic neuron (axonterminal) Synapticvesicles NT transporter Voltage-gatedsodiumchannel + Neurotransmittermolecule Ligand-gated ion channel (directexcitationorinhibition) Postsynaptic neuron GPCR (modulatory) +

  11. Neurotransmission Neurotransmitter Ions Plasma membrane Cytoplasm g a Ion channel b Neurotransmitter Receptor Plasma membrane Cytoplasm Effector protein Intracellular messengers a GTP GTP G-protein is activated G-protein subunits or intracellular messengers modulate ion channels

  12. Neurotransmitters Acetylcholine m/i Acetylcholine(motor neurons) Indolamines m/i Serotonin(memory, emotion) Monoamines Dopamine (motivation, addiction) m Catecholamines m Norepinephrine/Noradrenaline(sympathetic NS) m Epinephrine Glutamate(most prominentin CNS, excitatory) m/i m/i GABA (30%-40% of CNS synapses, inhibitory) AminoAcids i Aspartate Glycine(can be excit. orinhib. dependingon Cl-conc.) * i m Adenosine m Guanosine Purines i/m ATP Others Endorphins Opioids Enkephalins Dynorphins Neuropeptides Substance P Non-opioids m Neuropeptide Y Others NO Solublegases CO

  13. Nicotinicmuscle Nicotinic Junctional [(a1)2bed] Acetylcholinereceptors Phenyltrimethyl-ammonium Nicotinic Embyonic [(a1)2bgd] Elapid a-toxins, d-Tubocurarine Nicotinic Neuronal a2 (a-toxin insensitive) Nicotinic Nicotinic Neuronal b2 Nicotine Stage 1 Stage 2 Stage 3 Nicotinic Neuronal a3 (a-toxin insensitive) d-Tubocurarine Nicotinic Neuronal b3 Nicotinic Neuronal a4 (a-toxin insensitive) Nicotinicneuronal (a+b) Nicotinic Neuronal b4 Dimethylphenyl-piperazinuim, Cystine Nicotinic Neuronal a5 (a-toxin insensitive) Trimethaphan Neuronal bungarotoxin Nicotinic Neuronal b5 Nicotinic Neuronal a5 (non-functional without a subunits) Nicotinic Neuronal a6 (a-toxin insensitive) Cholinergic Nicotinic Neuronal a7 (a-toxin sensitive) Acetylcholine Nicotinic Neuronal a8 (a-toxin sensitive) Nicotinic Neuronal a9 Muscarinic m1-M1 Pirenzepine Muscarinic Muscarinic m2-M2 Methoctramine Muscarine, Pilocarpine Oxotremorine Muscarinic m4-M4 Himbacine Atropine Propyllbenzilylcholine mustard Quinuclidinyl benzilate Muscarinic m3-M3 Hexahydro-siladifenidol Muscarinic m5-M5

  14. Acetylcholin-esterase (AchE): • Quick removal of Ach from the synaptic space • Ach→ choline+acetyl • Reversible inhibitors:therapeutic use (myasthenia, glaucoma, Alzheimer’s) • Irreversible inhibitors: chemical weapons and pesticideseg. organophosphates Ach AchE

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