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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
How long do kinase receptors take to exert their effect?
A few hours
26
What else do tyrosine kinase receptors contribute to?
Receptors for cytokines so are important for the immune response
27
Type I nuclear receptors
Present in the cytosol and then move into the nucleus Only contain 1 protein
28
Type II nuclear receptors
Resident receptors that stay in the nucleus Contain 2 proteins
29
What feature must nuclear receptor agonists have?
Must be lipid soluble agonists as they have to enter the plasma membrane to exert an effect
30
What is meant by the affinity of a drug?
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
Occupation vs activation
Occupation is governed by affinity Activation is governed by efficacy
32
KD
Constant that defines the affinity of a drug for a receptor Forwards rate = K=1 [A]*[R] Reverse rate= K - 1 [AR]
33
How does the KD value show affinity of a drug?
Low KD= high affinity High KD= low affinity
34
Occupancy =
No. of receptors occupied / total no. of receptors
35
How is affinity measured at equilibrium?
Measuring occupancy using radioligand binding assays to measure binding of a ligand to a particular receptor/protein Radioactivity allows measurements to be taken
36
How are tissues selected for radioligand binding assays?
Selected to contain binding sites of interest Can be isolated membranes, slices, synaptosomes, cultured cells or solubilised/ purified receptors
37
What are radioligand binding assays incubated with?
Protease inhibitors for proteins Antioxidants if the ligand is oxidisable
38
Selection of radioligands
Must be biologically active, extremely pure chemically, labelled specifically as possible
39
How is degradation avoided doing radioligand binding assays?
Radical scavenger Storing at low temps and avoiding light
40
Specific binding =
Total bound - non specific binding Plotted on a logarithmic scale
41
Langmuir equation
Describes relationship between receptor occupancy, affinity and drug concentration
42
EC50
Effective concentration giving 50% of maximal response Measure of agonist potency
43
Partial agonists
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
Efficacy
Measure of a single agonist receptor complex's ability to generate a response
45
Chemical antagonism
Substances combine in solution so that the effects of the active drug is lost- agonist is chemically altered by the antagonism
46
Example of chemical antagonism
Inactivation of heavy metals- mercury and lead poisoning
47
Pharmacokinetic antagonism
Reduction in the amount of drug that is absorbed, metabolised or excreted by another
48
Examples of pharmacokinetic antagonism
Decrease in absorption from the GI tract and drugs that inhibit gut motility Taking warfarin (anticoagulant) Diuretics
49
Physiological antagonism
The interaction of two drugs with opposing actions in the body
50
Example of physiological antagonism
Noradrenaline raises blood pressure by acting on the heart and peripheral blood vessels Histamine lowers this by causing vasodilation
51
Competitive antagonists
Receptors that bind to a receptor to form a complex which doesn't have the ability to cause any downstream effects
52
What is the strength of competitive antagonist complexes determined by?
The balance between the forwards and backwards reactions at equilibrium
53
Non-competitive antagonism
Blocks a step in the process between receptor activation and response Doesn't compete with agonist for receptor site
54
Gi
Inhibits adenylyl cyclase
55
Gq
Activates phospholipase C which then activates IP3 Causes a Ca2+ influx
56
Dose ratio
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
What does a Schild analysis measure show?
Competitive antagonist affinity
58
pA2 =
-log10(molar conc of antagonist that gives a dose ratio of 2) -1*logKd

Pharmacology (5 decks)

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