AL - Ligand Binding I

Question 1

Why do we care about membrane proteins? (3)

Answer 1

• Approximately 50% of drugs target membrane-based proteins (receptors).
• GPCRs make up 12%, highlighting their importance in drug development.
• Ion channels (LGICs + VGICs) together account for 16%, playing a key role in pharmacology.

Question 2

What are the proportions of different membrane proteins? (7)

Answer 2

• 52% - Others (grey)
• 12% - GPCRs (red)
• 10% - VGICs (blue)
• 9% - Protein kinases (light green)
• 6% - LGICs (yellow)
• 6% - Transporters (dark green)
• 5% - GPCR-related (orange)

Question 3

What were the most dispensed drugs in England in 2020? (Top 3 by number of items)

Answer 3

• Atorvastatin - 49,678,685
• Omeprazole - 34,376,490
• Levothyroxine sodium - 33,460,365

Question 4

What are examples of drug categories and their targets? (6)

Answer 4

• DHP Ca²⁺ channel blocker - Amlodipine
• PPI (Proton Pump Inhibitor) - Lansoprazole
• β₁ ADR antagonist - Bisoprolol fumarate
• β₂ ADR agonist - Salbutamol
• SSRI (Selective Serotonin Reuptake Inhibitor) - Sertraline hydrochloride
• μOR agonist - Co-codamol (Codeine phosphate/paracetamol)

Question 5

What were the top-selling pharmaceutical products in 2020? (Top 3 by sales in billion USD)

Answer 5

• Humira (AbbVie) - $20.4 billion (Ab - TNFα)
• Keytruda (Merck & Co.) - $14.4 billion (Ab - PD1)
• Revlimid (BMS) - $12.2 billion

Question 6

What are common categories of top-selling drugs? (3)

Answer 6

• Monoclonal Antibodies (mAbs): Humira (TNFα), Keytruda (PD1), Stelara (IL12+23)
• Targeting Endogenous Ligands: Eylea (VEGF trap)
• Cardiovascular Agents: Eliquis, Xarelto

Question 7

What is the objective of Molecular Pharmacology?

Answer 7

• Identifying endogenous and exogenous ligands to study their function and pharmacological applications.

Question 8

What are some challenges in Molecular Pharmacology?

Answer 8

• Cannot perfectly predict molecular effects in silico yet.

Question 9

What are key experimental approaches in Molecular Pharmacology? (5)

Answer 9

• Isolate, sequence, clone, and express wild-type and mutant forms.
• Functional assays: In vitro screening for pharmacological effects.
• Model systems: Cell lines for in vivo screening.
• Structural analysis: Understanding ligand-binding and function.
• In vivo studies: Investigating receptor functions, including ‘orphan’ receptors.

Question 10

What is the old-school approach to receptor-ligand studies? (6)

Answer 10

1) Ligand Selection & Receptor Source:
- Selective, high-affinity ligand → Labels receptors for study.
- Rich receptor source → Essential for purification.

2)Ligand Labelling & Imaging:
- Labelled ligand + tissue → Enables receptor imaging.
- Labelled receptor → Determines receptor properties.

3) Receptor Characterization:
- Solubilisation/purification → Isolate receptors for study.
- Reconstitution/function → Test receptor activity.

4) Downstream Analyses:
- Biochemical, biophysical, structural characterization.
- Raising antibodies for immunocytochemistry.

5) Gene Sequencing Approach:
- Partial sequence → Screen cDNA libraries → Predict receptor structure.

6) Functional Expression & Drug Screening:
- Stable transfection → Drug profiling.

Question 11

How does the modern approach to receptor-ligand studies differ? (5)

Answer 11

1) Bioinformatics: Uses computational tools to predict receptor function.

2) Gene Manipulation: CRISPR and siRNA for direct in vivo studies.

3) Gene Cloning & Expression: Recombinant receptor production.

4) Protein Characterization: Biochemical, structural analysis.

5) Screening Approaches:
- In silico modelling/screening → Predict ligand binding.

• In vitro screening → Test ligand efficacy.
• In vivo screening → Drug candidate testing.

Question 12

What are some advantages of the modern approach? (3)

Answer 12

• Faster and more efficient receptor identification.
• Integration of computational and experimental techniques.
• More targeted and cost-effective drug discovery.

Question 13

What is the rationale behind ligand binding? (3)

Answer 13

1) Drug Binding Sites in Tissues:
- High-affinity specific receptor sites → Selective, strong interaction.
- Low-affinity nonspecific binding sites → Lipophilic interactions.

2) Types of Drug Binding:
- Specific binding → High selectivity, physiological relevance.
- Nonspecific binding → Less selective, physicochemical interactions.

3) Importance of Ligand Binding Techniques:
- Distinguishes specific vs. nonspecific interactions.
- Aids in drug development and receptor-ligand characterization.

Question 14

What are typical characteristics of a receptor? (3)

Answer 14

• Monomeric (some)
• Expressed at low density
• Can be irreversible