YR1 Lecture 1H - Receptor - Enzymes as Cellular Drug Targets 2021 PDF

Receptor and enzymes as drug targets Prof Gerald Muench MD year 1 – 2021 School of Medicine Western Sydney University LEARNING OBJECTIVES Explain why most drugs have to bind to components of the cell to exert their action 4 Protein targets for drug binding Describe the concept of receptors Different...

Receptor and enzymes as drug targets Prof Gerald Muench MD year 1 – 2021 School of Medicine Western Sydney University LEARNING OBJECTIVES Explain why most drugs have to bind to components of the cell to exert their action 4 Protein targets for drug binding Describe the concept of receptors Differentiate between agonists and antagonists and their action on receptors Describe the concept of enzymes Differentiate between competitive and noncompetitive inhibitors and their action on enzymes Blended Learning Slides, videos, and short answer questions Videos to watch before the lecture https://www.khanacademy.org/science/biol ogy/cell-signaling/mechanisms-of-cellsignaling/v/overview-of-cell-signaling And the following video’s in that chapter https://www.schrodinger.com/training/vide os/small-molecule-drugdiscovery/introduction-drugs-drug-targetsand-molecular Drug targets Ø Drugs interact with their targets by binding to binding sites Ø Specific regions within the binding site that are involved in binding interactions are called binding regions Ø Binding interactions typically involve intermolecular bonds Binding site Binding regions Drug Binding groups Intermolecular bonds Binding site Drug Drug Macromolecular target Unbound drug Macromolecular target Bound drug Most drugs are in equilibrium between being bound and unbound to their target “Lock and Key” hypotheses for ligand binding Lock and Key: Protein and ligand / substrate have complementary shapes. ‘Induced-Fit’ Hypothesis ü At least two steps …… e.g., step 1 is initial binding and step 2 is a change in structure of the receptor (and/or drug) ü Receptor / Enzyme is flexible! …… can wrap around the drug …… ü All intermediate cases do exist in nature 6 Molecular Modelling allows in silico drug design Clip: A basic introduction to drugs, drug targets, and molecular interactions – Video “Schrodinger” Four major protein targets for drugs 1. Receptors 2. Carrier molecules (Transporters) 3. Ion channels (bind or move target molecules) 4. Enzymes (convert substrates into products) Four major protein drug targets Receptors Receptors are complex macromolecules to which endogenous mediators (eg. hormones, neurotransmitters) bind and initiate changes in cellular function Most receptors are embedded in cell membranes No drug specificity for the receptors. g All receptors that exist in the organism have physiologic roles, and no receptor has been specifically ‘allocated’ for drugs ( & Many drugs can bind to family ,/subtypes;when cause different types of receptors on a cell admistering adrug don't have adverse affects you don't have a specificity to a certain drug - Receptor they may bind to multiple receptors Raffa et al. 2005. Netter’s Illustrated Pharmacology causingadvn "Cr protein coupled receptors' Ligand binding to a receptor initiates signals inside the cell intergrated tracellular domains long polypeptide plasma -Antagonist ge I within the ↑ ↑ s Intracellular domains membrane activates. / Major families of 2-coupled receptors on. receptors memb raveg or ligand e going tobinstthe is / Trans unit A hi > - (enzyme) > > - Membrane is which to the plasma I boud at the outside & place > - Catalyses ATP (secondam · energy currency ma cell ADENOSINE TRIPHOSPHATE" messenger) > CyclicAdenosea d centers - > binds - the nocleus to the cyclic AMP response element region binding of - Signal Transduction involving Gs-Proteins - Guanine - GS-Protein & stimulating Hetero Trimeric in nature - 3 subunits. / - alpha unit-Binds to GDP bette unit > - gamma mit -membrane-bound protein of 3 subunits (a, b, g) e e ntl y -as subunit has binding site for GDP Gunins diphosphate-Bond-conval ↓ weak -GDP bound non-covalently Bond quite Bond quie - > - d moderately binding ↓ be able to should itself dissociatefrom. heterotrimeric in nature ↑ & b g a - GDP 4 protein "GS protein" dissociate from itself will Signal Transduction involving Gs-Proteins Interaction of receptor with Gs-protein Ligand /DRUG BINDER > - ↓ change"change) conformational A & Receptor "came a Cell membrane Receptor g ß a G Protein in G ↑ the Ligand binding Induced fit g ß a G-protein binds Induced fit for G-protein ↳ Binding site for G-protein opens = GDP protein g ß a GDP GTP G-protein alters shape GDP binding site distorted GDP binding weakened GDP departs Signal Transduction involving Gs-Proteins Interaction of receptor with Gs-protein * change in the alpha unit dissociation heterotrimeric g ß a GTP binds & Binding site recognises GTP ß g a GAMMARTA Fragmentation and release g LEFT - LatPprotein Induced fit G-Protein alters shape alters Complex destablised & the shape complex in becomes & destabilized" About the a, b , gamma = ß unit AIRHA a DESTABILISATION complexes "I protein complex" "Generated Notes: L RIGHT unit" Process repeated for as long as ligand bound to receptor Signal amplification - several G-proteins activated by one ligand. to the next level as Subunit carries message to next The binding sites of the G-protein to the receptor were identified by Prof. Muench in his PhD thesis. D Palm 1, G > - Münch, D Malek, C Dees, M Hekman Identification of a Gs-protein coupling domain to the beta-adrenoceptor using site-specific synthetic peptides. FEBS Lett 1990 Feb 26;261(2):294-8. Signal Transduction involving Gs-Proteins GTP GDP Interaction of as with adenylate cyclase - I means GTP hydrolysed to GDP catalysed by as subunit Binding / as-subunit ATP cyclic AMP adenosine Triphosphate Active site (open) S /energycurren) * ATP of can - as Subunit recombines with b,g dimer to reform Gs protein dissociate ↓ into cyclic Signal transduction (con) elements ↳ cyclic AMP monosphosphate NO a longernota gig Active site anymore of the (closed) "Secondary messengers as Subunit changes shape Weaker binding to enzyme Departure of subunit Enzyme reverts to inactive state Signal Transduction involving Gs-Proteins Interaction of as with adenylate cyclase GDP gets Notes: into GDP hydrolysed > Several 100 ATP molecules converted before as-GTP deactivated converted to cyclic Represents another signal amplification a lot of molecules AMP Cyclic AMP becomes next messenger (secondary messenger) & To pass Cyclic AMP enters cell cytoplasm with message -. information BA 5Nitrogen NH2 NH2 N N O O O N N HO P O P O P O OH OH OH ⑳ Adenosino Ch Adenylate cyclase Adenylate cyclase N H H Triphosphate" OH N N ↑ O H Ribose OH - sugar O 3 O H H " membered sugar P "A fire Secondary O cause. downstream N O H ATP ATP O 2 to cellular response a O OH messor Cleaves my cycles a andyn Cyclic AMP Cyclic AMP OH onto Ribole on back Sugar E single phosphate molecule Signal Transduction involving Gs-Proteins Interaction of cyclic AMP with protein kinase A (PKA) Notes: I amino asic ↳ polypeptides protein Remember. a" Kinde "Protein & "c : - ~ activity Catalytic down stream causes. Protein kinase A is a serine-threonine kinase in > few body Activated by cyclic AMP Catalyses phosphorylation of serine and threonine residues on protein substrates Phosphate unit provided by ATP kinases activated " hydroxy" residue H N O ↑ C Protein Protein kinase kinase A A H - by cyclic Serine Serine "amino-acids" I Creating of O charge the within mokale. H N C H OH that reside CH3 P HO the serum residue in H O HC. O P CH3 OH HO groups Residue O chagee C rate Phosphate a negativecharge ↓ phosphate positive charge with interaction H N ↓ Threonine Threonine O OH ↑ Phosphate O Protein Protein kinase A kinase A C HC No & O O. degree. H phosphorylated a secondary alcohol. O H N t OH AMP our the vonic - the - needs or Build on protein requires doesn't read. of = phosphere & 4 groups a Negate charges E or G-Protein Coupled Receptors Ligands Ed which serotoin Monoamines e.g. dopamine, histamine, noradrenaline, acetylcholine Nucleotides Lipids Hormones -Thyroxine corticul , Glutamate Ca++ (Calciun). can bind G-Protein to coupled Receptor. G-Protein Coupled Receptors bind o adrenergiz will Receptor Types and Subtypes to * receptor ADRENALINE Reflects differences in receptors which recognise the same ligand "nomenclature" of receptors chemical compounds the ↳ A set of rules to generate systemic names nomenclature Types s Receptor - Adrenergic binds Acetylcholine Cholinergic La Dopamine Bind L decired Alpha (a) Beta (b) from the to and - birds lig receptor (serotonergic. reception. Subtypes a1, a2A, a2B, a2C b1 , b2 , b3 = TISSUES ° will Nicotinic Muscarinic to serotonin. for M1-M5 be to distributed pe differente - G-Protein Coupled Receptors Receptor Types and Subtypes RECEPTORS OF VARIABILITY TISSUES AMONG DIFFERENT This will kicks drug · etc ; If receptor ↳ Activate Note in a for the # the (B1 , , particular drug ↑ HR , Binds to ) B2) =. - you B2 & EffECTS ADVERSE Cause. activate can B3) if etc, Adrenaline - there is fight the better no specificity orfightrespouse/exercising a ↳ Adrenaline d Receptor types and subtypes are not equally distributed Eesponse of expireatthe amongst tissues during 02 HFOUND ↓ ligand ( (Bronchodilation) Adrenergic response Target selectivity leads to tissue selectivity causingmusceon Activate whole Load from one. w ; FAT , CELLS necessary Need By cells Oz & Intake , burning more Fue case e intake ↑ & exercise. > - to the ↑ Activate[Beal Hom, Smooth Heart muscle Fat cells Bronchial muscle GI-tract / smooth muscles I glands - Tissue in lunge. heart d ↑ HR , ↑ contractile force of me heart - b1 adrenergic receptors w b3 adrenergic receptors adipose tissue a1& b2 adrenergic receptors a1 a2 & b2 adrenergic receptors -. Agonists Agonists are chemicals that bind and activate receptors Two types: – Endogenous agonists (physiological compounds) advenal etc ; Adrenaline produced glands in. – Drug agonists (mimic the action of endogenous agonists) bind to the receptor have the structural ↳ Because - They then or the mutual for the binding similarity structural complexity allowing to take place. Moleuces = are going activate & chemicals to bind. receptors and that Agonists which mimics structure of Me - BINDS we & effect - I amount receptor -Activateceptor a of endogenous ligand present I the -downstream effect membang B ligand ↓ Activate get plana Cumulative - Activate * embedded in the we N P. DRUG OR LIGAND & = naturalformlocallyor en e Responses. "Are molecules Antagonists or compounds that are actually going Antagonists are compounds that bind but do NOT activate receptors à (often called blockers) * Not a downstream caling receptor would normally do effect of what the. Antagonists reduce or block the action of endogenous agonists by preventing their attachment to receptors or by displacing already attached agonists to bind to E receptors , BUTNOTACTIVATE Antagonists 2 major different mechanisms of Antagonism (the same principles apply to enzymes) Competitive antagonist: Antagonist binds to the ligand binding site Non-competitive: Antagonist binds to different site from ligand binding site (but by binding there distorts the receptor shape so that the ligand binding site is blocked) Reversible vs. irreversible: A reversible antagonist can be "bumped off" the active site (e.g by an excess of agonist) An irreversible antagonist is a type of antagonist that binds permanently to a receptor, either by forming a covalent bond to the active site, or alternatively just by binding so tightly that the rate of dissociation is effectively zero. to bind ; its going Antagonist effect without causing any to > - a receptor no ?- MEANS sodicur coming throughthepostsynapticmencarePARALYSED (neuromuscular bloc.. post synaptic Example: Tubocurarine, an antagonists for the nicotinic acetylcholine receptor # Chargh) > (acetylcholine - The nicotinic acetylcholine is located in the neuromuscular junction =. (plant) Tubocurarine Calkaloid) el hare. minic structure Ligand hastomini = the Ligand ORDER in - to FUNCTION - Pentametric unit ? O amino a Ligand binding USEFUL DRU4. > allowing for charge.receptorelectrochemical shifts gradient present EXTRACT - gap junction more to the ↓ CALSE ; Action " across post synaptic d Depolarisation. cell potentid across the skeletal muscle >Leading To) - muscle (muscular contraction) hynos & ions SINUS or to actual : order to relay GA pt - used in surgery to muscle any sudden prevent te skeletal + the in OR jerks or movements - are O. receptor room; of sodiver Alkaloid arrow poisons from South America which "RUDE nicotine receptors in bind to the (change) & change strong structural the nicotinic acetylcholine conformity of can ammonium ion - ↳ causes / coronary group ↓ - (prevention) ↳ Section - - Picaronian? SAQ Tubocurarine is an antagonists for the nicotinic acetylcholine receptor. What type of agonists is it ? Binds without causing effect any What would the physiological effect of exposure be ? A = neuromuscular blocks ; paralysed ; EFFERT > - taking place depolarisation te Sodium no Why is a good poison ? -Does it target the nicotinic or muscarinic entering - receptors. , postsynaptic due to well. -> no Paralytic Effects. Enzymes: the biological catalysts ↳ pathological docatalysts o What do they ↳ ? the speed up reaction event that takes of - PAC-MANFIGURE Recycled and no Response BIND are in the human body - & change longi capable of performing enzymes place biochemical , whe of encyme Most the site Active dateabstanee mere ↳ structural · body. human the in presented in the liver Most of the factory Clip: Enzyme function of the d Mostproduced enzymes , birchenical. human body are generated on the subtracte. dissociation - Drugs that Act on Enzymes Drugs may act on enzymes in form of competitive and noncompetitive inhibition – competitive inhibition - a drug acts as a substrate analogue to reversibly block enzyme’s active site and thus inhibit the biochemical process – non-competitive inhibition - a drug binds to a site different from the enzyme indirectly blocking its function same going t originally bird to to substrate to mat the to bird -. going Bepphemicale eden is 1 prevents rentalm the ( S ↳ site -inhibit on e the enzyme e. te ISTORTS the overall shape of the enoyme. Competitive vs non-competitive Inhibition (in most cases reversible) CLINICAL * Medical ↑ Pt-hyperlipidemie career - Bio ace ↑ thatt↓akepla of seril 3 - No synthesis of Cholesterol taking. place "blockbuster drugs" methyl convers a hydroxy/3 into ↑ , ↓ ↳ Coenzyme reaction synthesis cholestral of body -. Downstream ↳↑ plaque in effects (build-up). Arteries BO & ocardical (M1) Infarction "Sporlere"??. Reductase ↳ SYNTHESISES Cholesterol =. Thisengme,thesubstrate. enzyme itself (convert to URIC ACID) enzyme * Anticoagulation. https://image.slidesharecdn.com/enzymeinhibition-141210062641-conversion-gate01/95/ enzyme-inhibition-10-638.jpg?cb=1422431770 Irreversible inhibition (can be competitive or non-competitive) – example.. Muscle contraction * Need to Revise - Irreversible inhibition (can be competitive or non-competitive) Organic phosphates (poisons like nerve gases) are irreversible inhibitors bead bind permanent covalent of acetylcholine esterase ↳ which further car. > - ↳ prevention of any due to being in activeled binding. Irreversible inhibition occurs by covalent adduct formation to the serine in the active site Renden thebemotune bertine ↑ /. rustra covalentpat phosp on Corganicforme serine /Reside and - can res residues hydrolysis ; where taller place Irreversible inhibition This example illustrates how inhibitors of acetylcholine esterase can cause paralysis Fadue to muscles staying contracted) Muscle contraction induced by acetylcholine is switched off by degradation of acetylcholine by AChE If it is not degraded, the muscle stays contracted and can not relax – paralysis !! X. generate to & platelets (new enzymes) new Other irreversible enzyme inhibitors Permanente used in medicine the ↑↑Nomatgoieng nmone g. ( Than Rendered in effective in the lifespan of the platest > (into thromboxe A2) which an > fever inflammation , or pain) acid (AA).. 2 stays emyme a lifespan inactive of that for & aspirin actually platelet. harbous Anti-clotting articoagulat effect of ( effect. Aspirin, also known as acetylsalicylic acid (ASA), reduces blood clotting, - inflammation, fever and pain, is a irreversible inhibitor of cyclooxygenase (COX). ↑ in have the ention place cascade taking into coments a whole series of prostagladins acid Arachidonic converted to no longer Thromboxine - converts E platelets) ; Arachidonic acid (AA) & A2. Renders the Molecule in effectiv ↑. ↓ Corelent bod Then converted to Thromboxne Az (platelet actimator) ↓ logulation Ciclotting carads) actfatt a on ↑.. bonel beingred harbour hydroxyl free. - O destate reside. group the donates actate serive grog to reside https://www.ncbi.nlm.nih.gov/pubmed/14592543. MCQ: Aspirin, also known as acetylsalicylic acid (ASA), reduces blood clotting, inflammation, fever and pain, is an irreversible inhibitor of cyclooxygenase (COX). By which bond or interaction is the active site (serine) inactivated by the drug? a) b) c) d) e) Hydrogen bond Hydrophobic interaction Ionic bond Covalent bonds Van der Waals interaction Weak) Enzyme Inhibition (Summary of Mechanism) I Competitive I Non-competitive Equation and Description Cartoon Guide Substrate S E S E I Compete for Inhibitor active site S I I Different site E + S← → ES → E + P + I ↓↑ EI E + S← → ES → E + P + + I I ↓↑ ↓↑ EI + S →EIS [I] binds to free [E] only, and competes with [S]; increasing [S] overcomes Inhibition by [I]. [I] binds to free [E] or [ES] complex; Increasing [S] can not overcome [I] inhibition. Juang RH (2004) BCbasics You should know.. That drugs have to bind to drug targets (mostly proteins) to exert their action The 4 protein targets for drug binding (more in the & channels transporters encymes) pharmacodynamics lecture) Receptors The concept of receptors To differentiate between agonists and antagonists and their action on receptors The concept of enzymes ④ Example To differentiate between competitive and noncompetitive inhibitors and their action on enzymes of each And be able to give an example for each of the I concepts ion , , 3 - - -. Reversible liversible non competites.