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Phase 2a - ICS > Drugs and receptors > Flashcards

Drugs and receptors Flashcards

1
Q

Druggability

A

Describe a biological target that is known to or is predicted to bind with high affinity to a drug.

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2
Q

Receptor

A

Component of a cell that interacts with specific ligand (exogenous or endogenous) and initiates a change of biochemical events - leading to the ligands observed effects.

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3
Q

How do chemicals communicate?

A

Via receptors

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4
Q

What are the different types of chemicals used in signalling?

A

Neurotransmitters
Autocoids
Hormones

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5
Q

Give examples of 4 receptor types

A
  1. Ligand-gated ion channels
    (nicotinic ACh receptor)
  2. GPCR (Beta-adrenoreceptors)
  3. Kinase-linked receptors (GF)
  4. Cytosolic/nuclear receptors (steroid)
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6
Q

Ligand gated ion channels

A

Pore forming membrane proteins - allow ions to pass through.

As a result the cell undergoes a shift in electric charge distribution.

Influx of any cation or efflux of any anions.

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7
Q

GPCR

A

Largest and most diverse (7 transmembrane regions).

Targeted by >30% of drugs.

Ligands include: light energy, peptides, lipids, sugars and proteins.

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8
Q

G proteins

A

GTP to GDP and use energy from this.

Ligand binding activates them and downstream signalling.

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9
Q

Types of GPCR

A

Gs - AC and cAMP (B2-AR)

Gq - PLC IP3 and DAG increase intracellular calcium and activate PKC (M3R)

Gi - inhibit AC therefore decreases cAMP production

G0 - limited effect on alpha subunit.

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10
Q

Kinase-linked receptors

A

Kinases are enzymes that transfer phosphate groups between proteins= phosphorylation.

Phosphate is from ATP.
Transmembrane receptor - binding of ligand (EC) causes enzymatic activity on the IC side.

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11
Q

Nuclear receptors

A

Works by modifying gene transcription (oestrogen has two zinc fingers) binds to DNA.

Tamoxifen - ER modulator or partial agonist.

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12
Q

What can lead to pathology?

A

Imbalance in chemicals (allergy - increased histamine; Parkinson’s reduced dopamine) or receptors (myasthenia gravis - loss of ACh receptors; mastocytosis (increased c-kit receptor).

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13
Q

Why is receptor characterisation essential in a therapeutic development?

A

Identify the receptor involved in a pathophysiological response.

Develop drug that act at that receptor.

Quantify drug action at that receptor.

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14
Q

Agonist

A

Compound that binds to a receptor and activates it

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15
Q

Antagonist

A

A compound that reduces the effect of an antagonist

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16
Q

Ligand

A

Molecule that binds to another (usually larger) molecule.

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17
Q

Two state model

A

Describes how drugs activate receptors by inducing or supporting a conformational change in the receptor from off to on.

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18
Q

Potency

A

EC50 the concentration that gives half the maximal response.

19
Q

Full agonists

A

Shifting of the curve (max response from lower dose). One compound is more potent.

20
Q

Partial agonists

A

Shifts curve to the right. Lower dose is needed but it is less efficacious.

E max is the maximum response achievable.

21
Q

Intrinsic activity

A

Or efficacy refers to the ability of a drug-receptor complex to produce a maximum functional response.

22
Q

What do antagonists do?

A

Do not activate receptors - reverse the effects of agonists.

23
Q

Competitive antagonism

A

Binds to the same site.

24
Q

Non-competitive antagonism

A

Binds to allosteric, non-agonist) site on the receptor to prevent activation of the receptor.

25
Q

Selective agonism

A

Potency of a range of agonists.

26
Q

Selective antagonist

A

Competitive antagonist.

27
Q

Cholinergic Receptor subtype

A

Two caterogories of cholinergic receptors:

mAChR - muscarine + atropine

nAChR - nicotine + curare

28
Q

Histamine receptor characterisation

A

H1 -allergic conditions

H2 - gastric acid secretion

H3 -CNS disorders AD, obesity, pain and rhinitis.

H4 - Immune system and inflammatory conditions (rhinitis, pruritis, asthma) inflammatory pain.

29
Q

Factors governing drug action

A

Receptor related: affinity, efficacy

Tissue-related: receptor number, signal amplification.

30
Q

Affinity

A

Describes how well a ligand binds to the receptor.

Shown by both agonists and antagonists.

31
Q

Efficacy

A

How well a ligand activates the receptor.

32
Q

Agonists have

A

Affinity and efficacy

33
Q

Antagonists have

A

Affinity but ZERO efficacy

34
Q

Isoprenaline

A

Non-selective beta adrenoreceptor agonist, an analog of adrenaline -> relaxation of pre-contracted human bronchial rings - ASTHMA.

35
Q

Beta-adrenoceptor inactivation

A

Bromoacetyl alprenolol menthane - irreversible antagonist - won’t come off the receptor.

36
Q

Receptor reserve

A

Some agonists need to activate only a small fraction of existing receptors to produce the maximal system response - FULL agonist in a given tissue (can be large or small).

No receptor reserve for a partial agonist - even 100% occupancy no max response.

37
Q

Signal transduction

A

Activation of a receptor can elicit differing responses via the signalling cascade.

38
Q

Drug action is governed by

A

Affinity and efficacy (receptor related), receptor number and signal amplification (tissue-related).

39
Q

Allosteric regulation

A

Binds to a different site as the agonist (binds to orthosteric site).

40
Q

Inverse agonism

A

When a drug that binds to the same receptor as anagonistbut induces a pharmacological response opposite to that of theagonist.

41
Q

Tolerance

A

Slow - reduction in agonist effect over time. Continuously, repeatedly, high concentrations.

42
Q

Desensitisation

A

Rapid - uncoupled, internalised, degraded.

43
Q

Specificity versus selectivity

A

Selectivity is better term to describe activity as no compound is ever truly specific.

Isoprenaline vs Salbutamol.

Phase 2a - ICS (43 decks)

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