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Pharmacology > Receptors > Flashcards

Receptors Flashcards

1
Q

What are the four main classes of proteins targeted by drugs in mammalian cells?

A

Receptors, enzymes, transporters, ion channels

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2
Q

Inverse agonists

A

Effect receptor signalling but cause a decrease in signalling

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3
Q

Opiate receptors

A

G protein couple receptors that are involved in reward pathways which is what causes addiction

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4
Q

What does it mean if a drug has -mab at the end?

A

It is a monoclonal antibody

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5
Q

Channels as drug targets

A

Can either be blockers or modulators
blockers block permeation and modualtors change the probability of it opening- can be an increase or decrease

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6
Q

Enzymes as drug targets

A

Can be inhibitors which inhibit normal reaction
can be false substrates which is when an abormal metabolite is produced
can be a prodrug which means an active form of metabolite is produced

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7
Q

Transporters as drug targets

A

Can be inhibitors meaning normal transport is blocked
can be a false substrate which means an abnormal compound will accumulate

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8
Q

Receptor drug target pathway

A

recognise stimulus -> transfer it to cell -> amplification of cytoplasmic signal -> modulation of effector systems over time -> adaptation of the system throughout feedback

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9
Q

Agonists

A

Drugs that bind to a receptor that causes a response and mimic the effect of chemical mediators

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10
Q

Antagonists

A

Drugs that prevent the repsonse of an agonist, majority of clinically useful drugs

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11
Q

Ligand gated ion channels

A

Usually have a lot of transmembrane domains with a binding site attached outside the cell

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12
Q

G protein coupled receptors

A

Always have 7 transmembrane domains that anchor them in the membrane
All have complex long extracellular carboxy terminus which is where the g protein binds

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13
Q

Kinase linked receptors

A

Only one transmembrane domain and a much simpler structure
Kinase- protein that has or uses any enzymatic activity to add phosphates to something

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14
Q

Nuclear receptors

A

Not anchored to the membrane, may be found in cytosol or in the nucleus
Within structure there is a part that binds to DNA so they can regulate gene transcription by turning genes on and off

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15
Q

Receptors fastest to slowest

A

Ion channels
G protein coupled and kinase linked
nucelear

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16
Q

Cys loop type ligand gated ion channel structure

A

Pentametric

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17
Q

Ionotropic glutamate type ligand gated ion channels structure

A

Tetrametric

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18
Q

P2X type ligand gated ion channels structure

A

Trimeric

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19
Q

What are the three different GPCR subunits?

A

Ga
Gb
Gy

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20
Q

Classical signalling by GPCRs

A

Binding to receptor leads to rearrangement of the protein whihc leads to activation of the G protein

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21
Q

How does agonist binding change the movement of GPCR subunits?

A

Alpha and beta subunits stay together
Binding of agonist means alpha subunit has a higher affinity for GDP
GDP is then exchanged for GTP

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22
Q

Switching off GPCR signalling

A

GTP loses a phosphate which means it returns to GDP
When alpha subunit is associated to GDP the beta gamma subunit rejoins
Switches off signalling

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23
Q

Gs

A

Activates andenylate cyclase which then activates cAMP
Signal transduction pathway

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24
Q

What disease is often linked to tyrosin kinase receptors? why?

A

Often work as growth factor receptors as they can change gene expression
Controls growth of cells so mutations and therefore cancers are strongly linked

25
Q

How long do kinase receptors take to exert their effect?

A

A few hours

26
Q

What else do tyrosine kinase receptors contribute to?

A

Receptors for cytokines so are important for the immune response

27
Q

Type I nuclear receptors

A

Present in the cytosol and then move into the nucleus
Only contain 1 protein

28
Q

Type II nuclear receptors

A

Resident receptors that stay in the nucleus
Contain 2 proteins

29
Q

What feature must nuclear receptor agonists have?

A

Must be lipid soluble agonists as they have to enter the plasma membrane to exert an effect

30
Q

What is meant by the affinity of a drug?

A

Physical chemical property that defines how likely the receptor and drug are likely to come together
Independent of whether or not it activates anything

31
Q

Occupation vs activation

A

Occupation is governed by affinity
Activation is governed by efficacy

32
Q

KD

A

Constant that defines the affinity of a drug for a receptor
Forwards rate = K=1 [A]*[R]
Reverse rate= K - 1 [AR]

33
Q

How does the KD value show affinity of a drug?

A

Low KD= high affinity
High KD= low affinity

34
Q

Occupancy =

A

No. of receptors occupied / total no. of receptors

35
Q

How is affinity measured at equilibrium?

A

Measuring occupancy using radioligand binding assays to measure binding of a ligand to a particular receptor/protein
Radioactivity allows measurements to be taken

36
Q

How are tissues selected for radioligand binding assays?

A

Selected to contain binding sites of interest
Can be isolated membranes, slices, synaptosomes, cultured cells or solubilised/ purified receptors

37
Q

What are radioligand binding assays incubated with?

A

Protease inhibitors for proteins
Antioxidants if the ligand is oxidisable

38
Q

Selection of radioligands

A

Must be biologically active, extremely pure chemically, labelled specifically as possible

39
Q

How is degradation avoided doing radioligand binding assays?

A

Radical scavenger
Storing at low temps and avoiding light

40
Q

Specific binding =

A

Total bound - non specific binding
Plotted on a logarithmic scale

41
Q

Langmuir equation

A

Describes relationship between receptor occupancy, affinity and drug concentration

42
Q

EC50

A

Effective concentration giving 50% of maximal response
Measure of agonist potency

43
Q

Partial agonists

A

Not able to produce the same/maximal response as a full agonist
Needs to reach 100% occupancy in order to achieve full response its capable of
Acts as an antagonist when in the presence of a full agonist

44
Q

Efficacy

A

Measure of a single agonist receptor complex’s ability to generate a response

45
Q

Chemical antagonism

A

Substances combine in solution so that the effects of the active drug is lost- agonist is chemically altered by the antagonism

46
Q

Example of chemical antagonism

A

Inactivation of heavy metals- mercury and lead poisoning

47
Q

Pharmacokinetic antagonism

A

Reduction in the amount of drug that is absorbed, metabolised or excreted by another

48
Q

Examples of pharmacokinetic antagonism

A

Decrease in absorption from the GI tract and drugs that inhibit gut motility
Taking warfarin (anticoagulant)
Diuretics

49
Q

Physiological antagonism

A

The interaction of two drugs with opposing actions in the body

50
Q

Example of physiological antagonism

A

Noradrenaline raises blood pressure by acting on the heart and peripheral blood vessels
Histamine lowers this by causing vasodilation

51
Q

Competitive antagonists

A

Receptors that bind to a receptor to form a complex which doesn’t have the ability to cause any downstream effects

52
Q

What is the strength of competitive antagonist complexes determined by?

A

The balance between the forwards and backwards reactions at equilibrium

53
Q

Non-competitive antagonism

A

Blocks a step in the process between receptor activation and response
Doesn’t compete with agonist for receptor site

54
Q

Gi

A

Inhibits adenylyl cyclase

55
Q

Gq

A

Activates phospholipase C which then activates IP3
Causes a Ca2+ influx

56
Q

Dose ratio

A

How many more times an agonist is needed in the presence of an antagonist
conc of agonist in presence of antagonist / conc of agonist in absence of antagonist

57
Q

What does a Schild analysis measure show?

A

Competitive antagonist affinity

58
Q

pA2 =

A

-log10(molar conc of antagonist that gives a dose ratio of 2)
-1*logKd

Pharmacology (5 decks)

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