G Protein-Coupled Receptors PDF

Foundations of Pharmacology PHAR2210 G Protein-Coupled Receptors A/Prof Lynette Fernandes These lecture slides and associated unit materials are the intellectual property of A/Prof Lynette Fernandes and should not be shared without her permission. Sha...

Foundations of Pharmacology PHAR2210 G Protein-Coupled Receptors A/Prof Lynette Fernandes These lecture slides and associated unit materials are the intellectual property of A/Prof Lynette Fernandes and should not be shared without her permission. Sharing course materials without permission breaches UWA’s student conduct regulations and may constitute a breach of the Copyright Act 1968.  Learning outcomes Describe the structure of G protein-coupled receptors Describe the role of G protein-coupled receptors in physiological processes Describe the adenylate cyclase and phospholipase C signal transduction pathways Explain the mechanisms by which G protein-coupled receptors cause a change in cell function Predict the effect of G protein-coupled receptor stimulation  Resources Rang and Dale’s Pharmacology, 10th edition 2024, London Elsevier. How drugs act: Molecular aspects. Pharmacology Education Project https://www.pharmacologyeducation.org/pharmacology/pharmacodynamics Selected figures on the LMS from Goodman and Gilman’s The Pharmacological Basis of Therapeutics 13th edition 2017 McGraw-Hill Education. Pharmacodynamics: Molecular Mechanisms of Drug Action. Chapter 3 G protein signalling video https://www.youtube.com/watch?v=FD3oksR-bhk  Receptor superfamilies Ion channel receptors (ionotropic) depolarisation or hyperpolarisation of cell membrane G protein-coupled receptors (metabotropic) change in membrane excitability generation of second messengers protein phosphorylation Enzyme-linked receptors protein phosphorylation, gene transcription, protein synthesis Nuclear (DNA-linked, intracellular) receptors gene transcription, protein synthesis  Receptor superfamilies Receptors have been broadly sub-divided into four major types or superfamilies Superfamilies are distinguished based on how they transduce the signal NOT on which chemical signals stimulate them NOT on the nature of the change in cellular function Receptors within a superfamily use similar transduction processes and have similar general structures  G protein-coupled receptors Largest superfamily of receptors largest single class of targets for therapeutic drugs neurotransmitters, hormones, opioids, amines, peptides, proteins, light-sensitive compounds, odours Interact with heterotrimeric G proteins GTP- and GDP-binding proteins Activate signal transduction pathways adenylate cyclase phospholipase C phosphodiesterase ion channels  G protein-coupled receptors Orphan and other 7TM receptors 5-Hydroxytryptamine receptors Leukotriene receptors Lysophospholipid (LPA) receptors Acetylcholine receptors (muscarinic) Lysophospholipid (S1P) receptors Adenosine receptors Melanin-concentrating hormone receptors Adhesion Class GPCRs Melanocortin receptors Adrenoceptors Melatonin receptors Angiotensin receptors Metabotropic glutamate receptors Apelin receptor Motilin receptor Bile acid receptor Neuromedin U receptors Bombesin receptors IUPHAR/BPS database of GPCRs Neuropeptide FF/neuropeptide AF receptors Bradykinin receptors Calcitonin receptors http://www.guidetopharmacology.org/GRA Neuropeptide S receptor Neuropeptide W/neuropeptide B receptors Calcium-sensing receptor C/ReceptorFamiliesForward?type=GPCR Neuropeptide Y receptors Cannabinoid receptors Neurotensin receptors Chemerin receptors Opioid receptors Chemokine receptors Orexin receptors Cholecystokinin receptors Oxoglutarate receptor Class Frizzled GPCRs P2Y receptors Complement peptide receptors Parathyroid hormone receptors Corticotropin-releasing factor receptors Platelet-activating factor receptor Dopamine receptors Prokineticin receptors Endothelin receptors Prolactin-releasing peptide receptor G protein-coupled estrogen receptor Prostanoid receptors Formylpeptide receptors Proteinase-activated receptors Free fatty acid receptors QRFP receptor GABAB receptors Relaxin family peptide receptors Galanin receptors Somatostatin receptors Ghrelin receptor Succinate receptor Glucagon receptor family Tachykinin receptors Glycoprotein hormone receptors Thyrotropin-releasing hormone receptors Gonadotrophin-releasing hormone receptors Trace amine receptor GPR18, GPR55 and GPR119 Urotensin receptor Histamine receptors Vasopressin and oxytocin receptors Hydroxycarboxylic acid receptors VIP and PACAP receptors Kisspeptin receptor G protein-coupled receptor drug Principles of Pharmacology. D.E. Golan. Lippincott Williams & Wilkins. 2005  G protein-coupled receptors membrane Rang and Dale’s Pharmacology, 2024 location of receptor: membrane 7 transmembrane domains effector: enzyme or channel respond to: hormones, slow neurotransmitters time scale of action: seconds, fast examples: adrenoceptors, muscarinic acetylcholine receptors Salbutamol, a b2-adrenoceptor agonist relieves bronchospasm in asthma  Some physiological roles of GPCRs System Agonist Receptor/Effector autonomic nervous system acetylcholine muscarinic acetylcholine receptors activate phospholipase C autonomic nervous system noradrenaline, b-adrenoceptors activate adenylate cyclase; adrenaline a1-adrenoceptors activate phospholipase C; a2-adrenoceptors inhibit adenylate cyclase vision light (photo bleaches rhodopsin (pigment) rhodopsin) smell odour molecules odorant receptors activate adenylate cyclase behaviour and mood serotonin, dopamine, various GABA, glutamate  Structure of GPCR metabotropic receptors 7 transmembrane domain receptors heptahelical receptors N ligand binding sites heterotrimeric G protein C Gas – activates adenylate cyclase (e.g., b2-adrenoceptor) Gai – inhibits adenylate cyclase (e.g., a2-adrenoceptor) Gaq – activates phospholipase C (e.g., muscarinic receptor)  b2-Adrenoceptor 1 1. extracellular N-terminus 3 2. 7 transmembrane a-helices 2 3. 3 extracellular & 3 intracellular loops 3 4. intracellular C-terminal tail 4  Protein kinases and phosphatases Protein phosphatases: Protein kinases: dephosphorylate proteins phosphorylate proteins cause inactivation cause activation  G proteins Comprise 3 subunits (a,b,g) the a-subunit binds GTP and has GTPase activity 3 main classes of Ga protein Gas activates adenylate cyclase Gai inhibits adenylate cyclase Gaq activates phospholipase C G proteins link GPCRs to effector proteins that generate intracellular second messengers (Gas) adenylate cyclase generates cAMP (Gaq) phospholipase C generates inositol 1,4,5-trisphosphate & diacylglycerol Adenylate cyclase signal transduction pathway ligand (agonist) 1 receptor 1 2 G protein 4 3 3 2 effector 4 5 active 2nd messenger 5 protein kinase 6 6 response Human Anatomy and Physiology. Marieb. 2004 Adenylate cyclase signal transduction pathway Agonist Receptor Extracellular Plasma membrane Intracellular g a b GDP Adenylate cyclase G Protein Agonist activation conformational change Affinity of receptor for G protein increases  Activation of G protein Extracellular Plasma membrane Intracellular g a b GDP GTP Receptor binds to heterotrimeric G protein Binding conformational change in Ga GTP binds to Ga Ga catalyses exchange of GDP for GTP  Activation of adenylate cyclase Extracellular Plasma membrane Intracellular g a b cAMP GTP ATP Ga dissociates from Gbg Ga binds to adenylate cyclase Adenylate cyclase cyclisation of ATP to cAMP  Inactivation of G protein Extracellular Plasma membrane Intracellular g a b GTP GDP cAMP cAMP cAMP GTP hydrolysed to GDP cAMP Ga dissociates from adenylate cyclase Ga binds to Gbg  Return to resting state Extracellular Plasma membrane Intracellular g a b GDP Receptor dissociates from G protein G protein inactivated Agonist no longer binds to receptor Receptor returns to resting state  b2-Adrenoceptor signalling cascade adrenaline 1 b2-adrenoceptor 1 2 G protein (Gas) 4 3 3 2 adenylate cyclase 4 5 cAMP 5 cAMP-dependent 6 protein kinase A 6 relaxation Human Anatomy and Physiology. Marieb. 2004  Phospholipase C signal transduction pathway agonist Diacylglycerol 1 1 receptor 2 G protein Gaq 3 4 5 3 2 Phosphatidylinositol 4,5-bisphosphate phospholipase C Inositol 1,4,5-trisphosphate 5 4 IP3 DAG 5 Ca2+ 5 PKC response Human Anatomy and Physiology. Marieb. 2004  Muscarinic acetylcholine receptor signalling cascade acetylcholine Diacylglycerol 1 muscarinic 1 acetylcholine receptor 2 3 4 5 G protein (Gaq) 2 Phosphatidylinositol 4,5-bisphosphate 3 Inositol 1,4,5-trisphosphate 5 phospholipase C 4 IP3 DAG 5 Ca2+ 5 PKC Human Anatomy and Physiology. Marieb. 2004 contraction