Receptors and signalling

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how do drugs exert their action

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1

how do drugs exert their action

by binding to proteins

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2

4 classes of proteins targeted by drugs

ion channels, enzymes, ion channels receptors

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3

what are ion channels

protein channels in the membrane that allow lipophobic /hydrophilic molecules through

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4

which ion channels to drugs target

involved in neurotransmission

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5

examples of drugs that target neurotransmission

sodium channel blockers

gabapentin

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6

how does gabapentin work

targets voltage gated calcium ion channels to prevent its movement and prevent AP

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7

role of receptor targeting

regulates cellular processes

enables communication between cells

enables coordination of tissue, organ and bodily responses

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8

how do drugs causes side effects despite being targeted

off target effects can occur which occurs from interactions with receptors in multiple organs

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9

what is an example of a drug and its side effects

opium has analgesic and euphoric effects but can cause constipation and respiratory diseases

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10

how does opium use lead to addiction

activation of reward pathways and changes in receptor function (tolerance)

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11

what is the cause of death in opium addicts

respiratory disease and suffer from chronic constipation

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12

how do receptors help in drug function

allows for specificity in drug function

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13

which type of receptor does not pass through the membrane

steroid

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14

what do ionotropic, metabotropic and kinase linked receptors have in common

they are found on the cell surface and have transmembrane spanning segments of 20-25 hydrophobic amino acids

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15

what is a feature and function of DNA linked receptors

regulates gene transcription

ligand must be able to cross the plasma membrane (lipophillic)

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16

what is an example of a DNA linked receptor

oestrogen receptors

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17

what is a ligand

any molecule that binds to the receptor

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18

what is a Agonist

drugs or chemical mediators that bind to a receptor producing a response

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19

examples of agonists

pilocarpine, nicotine, aCh, morphine

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20

what is an antagonist

does not a cause a downstream response or prevents/ inhibits the response of an agonist e

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21

examples of antagonists

atropine curare

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22

how long is the signal transduction of ionotropic, metabotropic, kinase-linked and nuclear receptors

mms, s, hrs, hrs

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23

what is an example of a LGIC

nicotinic ACh receptor

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24

what is an example of a metabotropic receptor

Muscarinic ACh receptor

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25

what is an example of a kinase-linked receptor

cytokine receptor

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26

what is an endogenous receptor

a compound naturally produced by the body which binds and activates the receptor

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27

what is the endogenous molecule for ionotropic receptors

small molecule chemical mediators not proteins

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28

what happens when a molecule binds to an ionotropic receptor

central aqueous pore opens

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29

how many transmembrane domains in GPCRS

7

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30

what structure do GPCRs have

alpha helical structure

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31

what is a heterotrimeric GTP binding protein

g protein

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32

when do lignad gated ion channels open

when they are bound by an agonist

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33

what does activation of an ionotropic receptor by excitatory neurotransmitters cause

membrane depolarisation and action potential firing

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34

where are nicotinic acetylcholine receptors found?

neuromuscular junction, autonomic ganglion neuron, brain neurones

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35

what is the agonist for NaChR

ACh and nicotine

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36

what is the antagonist for NaChR

tubocurarine (curare)

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37

examples of ionotropic glutamate receptors

AMPA and NMDA

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38

what are the 2 most common receptors

ligand gates and G protein coupled

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39

what are most hormones detected by

GPCRs

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40

what is the structure of GPCRs

a single protein and spans the membrane 7 times

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41

how do GPCRs work?

regulate effector proteins via heterotrimeric GTP binding protein

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42

what is the structure of a g protein

1 alpha, 1 beta, 1 gamma (heterotrimeric)

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43

how does signal transduction occur in GPCRs

via activation of g proteins

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44

how are g proteins selective

they can be made up of 30 different alpha, beta and gamma units to make different g proteins which interact with different GPCRs and effectors

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45

how many members of the GPCR family are there

800+

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46

what do GPCRs respond to

hormones, inflammatory mediators and chemokines

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47

why does GPCR signal transduction take longer than LGIC?

it is cascading and involves changing the function of different proteins

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48

where is the ligand binding site in an opioid receptor

buried within the transmembrane receptors

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49

what happens when the ligand is bound to a GPCR

it will make contact with several amino acids which influences the structure that the receptor will adapt

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50

which effectors can g proteins control

ion channels, enzymes

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51

types of ligand gated ion channels

cys-loop

ionotropic glutamate

P2x

calcium release

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52

examples of cyc-loop type receptor & assembly

nAChR, GABAa 5HT3

pentameric

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53

exmales of ionotropic glutamate type receptor and assembly

NMDA

tetrameric

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54

example of P2X type receptor and assembly

P2XR

trimeric

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55

examples of calcium release type receptor and assembly

IP3R, RyR

tetrameric

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56

what are LGIC used for

fast synaptic transmission

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57

what are the endogenous agonsists for LGIC

fast classical neurotransmitters stored in vesicles

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58

what are LGIC composed of

3-5 subunits

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59

how many transmembrane domains does each LGIC subunit have

2-5

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60

when does a LGIC close

when the agonist is removed or the receptor enters a desensitised state

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61

what causes changes in the excitability of a cell

ions flowing through open LGIC

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62

what happens in the activation of ionotropic receptors for inhibitory neurotransmitters

membrane depolarisation is inhibited

action potential firing is reduced

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63

what is an example of a receptor for an inhibitory neurotransmitter

GABAaRs expressed by the brain w

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64

what is the agonist for GABAaRs

GABA, phenobarbitone

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65

what is the antagonist for GABAaRs

Picrotoxin

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66

what is phenobarbitone used for

epilepsy

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67

what is the use of picrotoxin

CNS and respiratory system stimulant

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68

what is myasthenia gravis

an autoimmune disease where the body creates antibodies to skeletal nicotinic acetylcholine receptors

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69

what are the symptoms of myasthenia gravis

increasing muscle weakness, eye drooping

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70

how many people suffer with myasthenia gravis

1 in 2000

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71

how is myasthenia gravis treated

anti-cholinesterase to prevent the breakdown of ACh, and immunosuppressants

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72

example of an anticholinesterase

neostigmine, pyridostigmine

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73

why are some GPCRs referred to as orphans

because the ligand they respond to has not been identified

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74

when does signal transduction occur

following an agonist binding to a GPCR and activation of a g protein

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75

one G protein is used by _______ receptor

more than one

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76

how do g proteins achieve signal transduction

by undergoing an enzymatic cycle

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77

which g protein subunits interact with effectors

alpha and beta

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78

what happens when the agonist is bound to the GPCR

it stabilises the helices and activates signalling

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79

what happens when the antagonist is bound to the GPCR

it interacts differently with amino acids and adopts a shape not conducive to signalling

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80

what happens after agonist binding to GPCRs

signal transduction via g proteins which control the function of effectors

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81

how many types of g proteins are there

20

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82

what are second messengers

small diffusible molecules that spread signals

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83

how do noradrenaline and adrenaline work

via g protein coupled receptors

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84

where is the binding site of the g protein

the alpha subunit

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85

what is the role of GDP

associated with the inactive GPCR

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86

how is GDP suited to bind to an inactive GPCR

has a very high affinity to beta-gamma subunits in GPCRs

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87

how is the g protein activated after agonist binding

agonist becomes very attracted to the alpha subunit and associates with it

causes a change in the structure of alpha lowering GDP affinity for GTP instead

GTP replaces GDP and g protein is activated

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88

what do g proteins need to be activated

GTP

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89

what part if the g protien is a GTPase

alpha

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90

what is a GTPase

binds and hydrolyses GTP

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91

what is the limiting factor in GPCR signalling

receptor number

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92

how is the g protein inactivated

GTPase activity is activated in alpha and GTP loses a phosphate to become GDP

conformational changes increase attraction to beta-gamma subunit and reforms heterotrimeric g protein

alpha` subunit no longer attracted to effector molecule and beta gamma no longer regulating protein

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93

Gs protein

stimulates adenyl cyclase to make cAMP

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94

Gi protein

inhibits adenyl cyclase leading to a cAMP decrease

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95

Gq

increases phospholipase C

increased IP3 and DAG

increases calcium intake

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96

what is phospholipase c

an enzyme effector modulated by g protein

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97

which subunits regulates the activity of enzymes

alpha

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98

what causes an increase in pKA activity

increased cAMP

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99

what is cAMP

a second messenger that can diffuse into the nuclease to regulate proteins

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100

what is cAMP broken down by and into

phosphodiesterase into 5AMP

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