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Biomedical Pharmacology > Lecture 2 - Receptors > Flashcards

Lecture 2 - Receptors Flashcards

1
Q

What is a receptor?

A

Protein in nature Cell constituents that bind agonist - high affinity/specificity Conformational change elicits a cellular response

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2
Q

What will happen if an antagonist binds to a receptor?

A

Antagonist won’t cause this conformational change

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3
Q

How many supra families of receptors are there?

A

4

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4
Q

What are the supra families of receptors?

A

Ligand gated ion channel/ionotropic G-protein coupled receptors Kinase linked receptors Nuclear receptors

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5
Q

Tim scale of ligand gated ion channels/ ionotropic receptors

A

Milliseconds

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6
Q

Time scale of G-protein couples receptors

A

Seconds

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7
Q

Time scale of kinase linked receptors

A

Minutes

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8
Q

Time scale of nuclear receptors

A

Hours

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9
Q

Examples of ligand-gated ion channels

A

Nicotinic ACH receptors

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10
Q

Examples of G protein coupled receptors/metabotropic receptors

A

Muscarinic ACH receptors

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11
Q

Example of kinase linked receptors

A

Cytokine receptors

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12
Q

Examples or nuclear receptors

A

Oestrogen receptors

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13
Q

Ligand gated ion channels/ ionotropic

A

Receptors on which fast neurotransmitters act Opening and closing of ion channel lead to hyperpolaridation or depolarisation

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14
Q

G-protein coupled receptors

A

Membrane receptors that are coupled to intracellular effector systems via a G protein Contain receptors for many hormones and slow transmitters Endogenous molecule In binding to the receptor

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15
Q

Kinase linked receptors

A

Large and heterogenous group of membrane receptors responding to protein mediators Comprise extracellular ligand-binding domain linked to intracellular domain by single transmembrane helix Protein phosphorylation and dimerisation of the receptor

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16
Q

Nuclear receptors

A

Do not always start in the nucleus but will migrate toward here where they will have impact on transcription

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17
Q

Structure of ligand gated ion channels/ionotropic receptors

A

4 transmembrane domain 3 cytoplasmic loops 16-20 membrane-spanning segment surrounding a central ion channel

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18
Q

Structure of G-protein coupled receptors

A

7 transmembrane domain Single chain of polypeptide (400-500 residues) Binding domain on outside G protein Coupling domain on the inside

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19
Q

Structure of kinase-linked receptor

A

One membrane spanning domain Binding domain on outside Catalytic domain on the inside

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20
Q

Structure of type 4 nuclear receptors

A

No cell membrane DNA binding domain (region where you find zinc fingers)

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21
Q

What is a ligand gated ion prototypical example

A

nAChR

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22
Q

Ligand gated ion channel structure

A

Pentameric structure ( 5 subunits) 2 ACH Binding sites at the junction of subunits Number of subtypes exist

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23
Q

What does ligand gated ion channel bind to?

A

2 molecules of ACH

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24
Q

Major gated Na+ channel, activation results in what?

A

Change of electrical activity of cell

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25
Q

Where are Na+ channel found?

A

NMJ Autonomic ganglia CNS

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26
Q

What was the first characterised GPCR?

A

Beta-adrenoceptor (1986)

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27
Q

What is the typical structure of GPCR?

A

Typical structure with 7 transmembrane spanning domains

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28
Q

Signal transduction

A

As there are often a number of metabolic steps involved in signal transduction, they are also referred to as metabotropic

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29
Q

How many distinct families of GPCR?

A

3

30
Q

What is family classification of GPCR based on?

A

Sequence homology

31
Q

Family A of GPCR

A

Rhodopsin

32
Q

Family B of GPCR

A

Secretin/glucagon receptor family

33
Q

Family C of GPCR

A

Metabotrpic Glutamate receptor/ calcium sensor family

34
Q

Which family is most important in terms of numbers?

A

Rhodopsin

35
Q

Rhodopsin receptors

A

The largest group. Receptors for most amine neurotransmitters, many neuropeptides, purines, prostaglandin our, cannabinoids

36
Q

Rhodopsin structural features

A

Short extracellular (N terminal) tail. Ligand binds to transmembrane helices (amine) or to extracellular loops (peptides)

37
Q

secretin/glucagon receptors

A

Receptors for peptide hormones, including secretin, glucagon, calcitonin

38
Q

Structural features of secretin/glucagon receptor family

A

Intermediate extracellular tail incorporating ligand-Binding domain

39
Q

Metabotropic Glutamate receptor/ calcium sensor receptors

A

Small group Metabotropic glutamate receptors, GABA b receptors and Ca2+ sensing receptors

40
Q

Structural features of metabotropic glutamate receptors

A

Long extracellular tail incorporating ligand-Binding domain

41
Q

What is the potential fourth family of GPCR?

A

Includes many receptors for pheromones but no pharmacological receptors

42
Q

G proteins are comprised of how many subunits?

A

3

43
Q

G protein coupling depends on what?

A

Whether or not an agonist binds

44
Q

In the resting state what does G protein consist of ?

A

Trimer of alpha, beta and gamma subunits

45
Q

What happens when there is association of trimer with receptors?

A

Dissociation of GDP from alpha subunit

46
Q

How is G protein activated?

A

GTP replaces GDP in cleft and causing alpha subunit to dissociate from the beta gamma dimer

47
Q

What is the active form of G protein?

A

Alpha-GTP

48
Q

What are the G protein targets?

A

Adenylate cyclase Phospholipase C Ion channels

49
Q

Adenylate cyclase second messenger

A

Increases generation of CAMP and subsequent protein kinase activation

50
Q

Phospholipase C secondary messenger

A

Increases generation of DAG and IP3 from PIP2

51
Q

Ion channels secondary messenger

A

Differentiated from ionotropic receptors by existence of G-protein linkage

52
Q

What are you GPCR susceptible to?

A

Desensitisation (or tachyphylaxis or down regulation)

53
Q

What are the types of tachyphalaxis ?

A

Homologous and Heterologous

54
Q

What is homologous tachyphylaxis ?

A

Effect receptors which the G protein is bound to only

55
Q

What is heterologous tachyphylaxis?

A

Effects other receptors not only the ones where G protein is bound

56
Q

What characterises kinase linked receptor transduction?

A

This group of receptors are characterised by the presence of an intercellular tyrosine kinase domain

57
Q

What does kinase linked receptors signal transduction usually involve?

A

Dimerisation

58
Q

What does dimerisation allow for in kinase linked receptors?

A

Autophosphorylatin

59
Q

Why are kinase linked receptors important ?

A

Important in many regulatory processes including action of growth factors and cytokines

60
Q

Nuclear receptor

A

A receptor family that allows hormone and lipid signals to regulate gene transcription

61
Q

What do nuclear receptors regulate?

A

Regulate a host of complex phenomena including development, immune function, organ homeostasis and reproduction

62
Q

Why is dimerisation of nuclear receptors important?

A

DNA binding

63
Q

What does oestrogen do to nuclear receptors?

A

Oestrogen leads to dimerisation which exposes activation factors

64
Q

Where do Nuclear receptors reside?

A

In the cytoplasm or the nucleus

65
Q

Class I Nuclear receptors

A

Tend to be hormonal receptor. Present in cytoplasm Operate as homodimers Mainly endocrine ligands High affinity

66
Q

Class I Nuclear receptors examples

A

GR, MR, ER, MR

67
Q

Hybrid class nuclear receptors

A

Mainly endocrine Operate as RXR heterodimers

68
Q

Hybrid class nuclear receptors examples

A

TR and VDR

69
Q

Class II Nuclear receptors

A

Retinoid transporters Present in the nucleus Operate as Heterodimers (except RXR) Mainly lipid ligands Low affinity

70
Q

Class II nuclear receptors examples

A

PPAR, LXR, FXR, RXR

71
Q

Examples of non receptor drug targets

A

Voltage gated channels Transporters Enzymes

Biomedical Pharmacology (19 decks)

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