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Drugs: From molecule to man > ELM1: Receptors 101 > Flashcards

ELM1: Receptors 101 Flashcards

1
Q

What do most drugs bind to?

A

Proteins

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2
Q

What part of the protein do drugs bind to?

A

The binding domain

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3
Q

What type of bond is formed between a drug and its target protein?

A

Reversible
Lots of different types of bond

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4
Q

What is the definition of a receptor?

A

A protein that binds a molecular message and passes the information on in a different form

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5
Q

What is a protein superfamily?

A

Broad grouping of proteins that are related in terms of structure and function

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6
Q

What is the hierarchy of protein superfamilies?

A

Superfamily
Family
Subfamily

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7
Q

What is the GPCR superfamily?

A

G protein coupled receptors
Biggest superfamily with over 800 members

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8
Q

What is the rhodopsin-like family?

A

Largest family in the GPCR superfamily
Over 600 members
19 subfamilies

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9
Q

How do superfamilies arise?

A
  1. A gene duplicates in cell division and makes two of the same gene
  2. One gene is mutated and have no effect
  3. The spare copy is mutated enough and gains a function
  4. This makes a new receptor
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10
Q

What are the evolutionary advantages of diversity?

A

Greater flexibility of organisms
Better adapt to environment

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11
Q

What is the beta1 subgroup of adrenoceptors?

A

Expressed in heart
Role in increasing heart rate and force of contraction

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12
Q

What is the beta2 subgroup of adrenoceptors?

A

Expressed in bronchial smooth muscle
Role in dilation of airways

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13
Q

What does the existence of the beta1 and beta2 subunits mean for the pharmaceutical industry?

A

The different types mean we can target each individually without affecting the other
This makes drug development easier

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14
Q

What are ligand gated ion channels?

A

Transmembrane proteins with a built in ion channel
Neurotransmitter ligand binds and opens the channel

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15
Q

What is the process of a ligand gated ion channel becoming activated?

A
  1. Agonist binds to receptor at two agonist binding sites
  2. Conformational change and channel opens so ions cross the membrane
  3. Ions dissociate from receptor which inactivates and closes
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16
Q

What are pentameric ligand gated ion channels?

A

Ligand gated
Superfamily
5 subunits in a ring around ion channel
4 transmembrane domains with N terminal extracellular domain

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17
Q

What are nicotinic acetylcholine receptors?

A

Ligand gated
Agonist is acetylcholine
Activated by nicotine
Allow sodium and calcium in to depolarise membrane

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18
Q

What is the physiological importance of nicotinic acetylcholine receptors?

A

Fast excitatory transmission between motor neurons and skeletal muscle
Fast synaptic transmission in autonomic ganglia
Modulate release of neurotransmitters in CNS

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19
Q

What is the pharmacological importance of nicotinic acetylcholine receptors?

A

In skeletal muscle are target of drugs to block neurotransmitter transmission
In brain are target of nicotine and drugs treat nicotine addiction

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20
Q

What is the structure of nicotinic acetylcholine receptors

A

16 subunits
5 classes of subunit

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21
Q

What are the 3 most important classes of nicotinic acetylcholine receptors?

A

GABAA receptors
Inotropic glutamate receptors
Brain nicotine binding site

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22
Q

What are GABAA receptors?

A

Pentameric ligand gated ion channels
Chloride channels
Hyperpolarises cell

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23
Q

What is the physiological importance of GABAA receptors?

A

Inhibitory transmitter in brain
Two classes A and B

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24
Q

What are GABAA receptors responsible for?

A

Fast synaptic transmission

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25
Q

What are GABAB receptors responsible for?

A

Slower inhibition

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26
Q

What is the pharmacological importance of GABAA receptors?

A

Target for drugs to decrease brain activity

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27
Q

What is the structure of GABAA receptors?

A

19 subunits
Mostly alpha beta and gamma

28
Q

What are inotropic glutamate receptors?

A

3 families of NMDA AMPA and Kainate
Cation channels
Agonist of glutamate and aspartate

29
Q

What is the physiological importance of inotropic glutamate receptors?

A

iGluRs do fast excitatory transmission
mGluRs do slower responses

30
Q

What is the pharmacological importance of inotropic glutamate receptors?

A

Inhibition of them is involved in anaesthesia and ketamine

31
Q

What is the structure of inotropic glutamate receptors?

A

Tetramers

32
Q

What are enzyme linked receptors?

A

Transmembrane proteins that associate with an enzyme

33
Q

What are receptor tyrosine kinases?

A

Enzyme linked receptor
Large proteins with single transmembrane domain

34
Q

What are tyrosine kinases?

A

Enzymes that phosphorylate tyrosine residues on the target protein

35
Q

How does the mechanism of receptor tyrosine kinases work?

A
  1. Agonist binds and RTK dimerises and tyrosine kinase domains activate
  2. Tyrosine kinase domains on each RTK phosphorylate tyrosine residues on partner RTK
  3. Activated receptor binds intracellular adaptor proteins and activates them by phosphorylating tyrosine residues
  4. Adaptor proteins link RTK to intracellular signalling pathways
36
Q

What is the physiological significance of receptor tyrosine kinases?

A

Bind peptide signalling molecules with roles in regulating growth and metabolism

37
Q

What is the pharmacological significance of receptor tyrosine kinases?

A

Drugs targeting them are insulin and insulin analogues

38
Q

What are nuclear receptors?

A

Superfamily 48 in humans
Bind lipophilic agonists

39
Q

What is the mechanism of nuclear receptors?

A
  1. Agonist crosses membrane and binds receptor
  2. Chaperones dissociate
  3. Receptor forms dimer and enters nucleus through pore
  4. Receptor dimer binds to hormone response element
  5. Receptor impacts transcription rate of target gene
40
Q

What is the physiological significance of nuclear receptors?

A

Regulating body’s basic functions

41
Q

What are some examples of steroid hormone receptors?

A

Glucocorticoid receptors
Mineral corticoid receptors
Thyroid hormone receptors

42
Q

What are glucocorticoid receptors?

A

Steroid hormone receptor
Regulate glucose metabolism and inflammation and immune system
Agonist is cortisol

43
Q

What are mineralcorticoid receptors?

A

Steroid hormone receptors
Regulate salt and water balance and blood pressure
Agonist is aldosterone

44
Q

What are thyroid hormone receptors?

A

Regulate metabolism and development and heart rate

45
Q

What is the pharmacological significance of glucocorticoid receptors?

A

Glucocorticoid steroids used for antiinflammatory

46
Q

What is the pharmacological significance of mineralcorticoid receptors?

A

Target for cardiovascular conditions

47
Q

What is the pharmacological significance of thyroid hormone recepotrs?

A

Treated with synthetic thyroid hormone

48
Q

What is the general structure of steroid hormone receptors?

A

DNA binding domain linked to ligand binding domain by hinge region Ligand binding domain binds to agonist

49
Q

What is the role of G protein coupled receptors?

A

To link an extracellular signal to intracellular signalling pathways

50
Q

What is the structure of G proteins?

A

Trimeric membrane associated proteins
Alpha beta and gamma subunits with lipid tails after translation
Bound to a GDP molecule

51
Q

What is the mechanism of GPCRs?

A
  1. Agnoist binds to GPCR
  2. Receptor is activated and interact with G protein
  3. Alpha subunit swaps GDP for GTP and G protein is activated
  4. G protein diffuses through membrane and activates more G proteins
  5. Alpha subunit dissociates and interacts with target protein to change activity and generate second messenger
52
Q

How is the signalling of a GPCR terminated?

A
  1. Agonist dissociates and terminates signal randomly
  2. Agonist reuptaken into surrounding cells to stop rebinding
  3. Alpha subunit hydrolyses GTP into GDP and P to shut down system and rejoins beta and gamma
53
Q

How are GPCRs arranged across the membrane?

A

Snake back and fourth across membrane 7 times

54
Q

What is the role of cAMP?

A

Second messenger
Produced from ATP
Concentrations depend on adenylyl cyclase and phosphodiesterase

55
Q

What is protein kinase A?

A

Activation changes the function of cAMP
Phosphorylates serine and threonine in target proteins
Found in cytoplasm
Inactive tetramer made of 2 catalytic and 2 regulatory subunits

56
Q

How do the subunits of protein kinase A link to cAMP?

A

Regulatory subunits bind 2 molecules of cAMP
Catalytic subunits are released and become active

57
Q

What is the role of Gs?

A

A G protein Stimulates adenylyl cyclase to increase cAMP concentration

58
Q

What is the mechanism of Gs G protein?

A
  1. Agonist binds to GPCR and activates it
  2. GPCR interacts with G protein and GDP replaced with GTP to activate it
  3. Alpha subunit dissociates and binds to adenylyl cyclase which stimulates it
  4. cAMP increases
  5. Alpha subunit hydrolyses GTP to GDP and P and reassociates
  6. Adenylyl cyclase no longer stimulated cAMP goes to normal
59
Q

What is the role of Gi/o?

A

Decrease activity of adenylyl cyclase to decrease cAMP concentration

60
Q

What is the mechanism of G protein Gi/o

A
  1. Agonist binds to GPCR and activates it
  2. GPCR interacts with G protein and GDP replaced with GTP to activate it
  3. Alpha subunit dissociates and binds to adenylyl cyclase which inhibits it
  4. cAMP decreases
  5. Alpha subunit hydrolyses GTP to GDP and P and reassociates
  6. Adenylyl cyclase no longer inhibited cAMP goes to normal
61
Q

What is the difference between the G proteins of Gq Gi/o and Gs

A

Gq is different as it couples to intracellular pathway using IP3 and DAG

62
Q

Where does DAG act?

A

Remains in membrane and modulates membrane proteins

63
Q

Where does IP3 act?

A

Released in cytoplasm and modulates proteins in endoplasmic reticulum

64
Q

How is DAG and IP3 made?

A
  1. Membrane protein PIP2
  2. PLC cleaves head off PIP2 and makes diaglycerol and inositol trisphosphate
65
Q

How does Gq activate phospholipase C to produce DAG and IP3?

A
  1. Agonist binds to and activates GPCR
  2. GPCR interacts with G protein and GDP is replaced by GTP which activates it
  3. Alpha subunit dissociates and binds to PLC
  4. PLC stimulated and cleaves PIP2
  5. DAG increases in membrane IP3 increases in cytoplasm
  6. Termination as normal
66
Q

What is the effect of IP3?

A
  1. IP3 binds to IP3 receptor on ER
  2. Allows calcium to enter cytoplasm
  3. Opens ryanodine receptor and causes calcium induced calcium release
67
Q

What is protein kinase C?

A

Cytosolic protein that becomes associated with membrane when it binds to calcium
Phosphorylates proteins on serine and threonine residues
Requires binding of DAG and calcium to activate

Drugs: From molecule to man (21 decks)

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