Molecular Pharmacology

Question 1

What is molecular classification of receptors?

Answer 1

Identify and sequence cDNA to predict the AA sequence. Repeat for all subtypes to give comparison my molecular classification. May identify new subtypes.

Question 2

Methods to reveal receptor subtypes? Least-most

Answer 2

Protein purification and cDNA cloning
Homology cloning
(EST) expressed sequence tags
Genome data mining

Question 3

What is a G-protein-coupled receptor?

Answer 3

A seven transmembrane receptor that binds extra cellular substances and transmits signal to an intracellular molecule G protein.

Question 4

How does a G protein coupled receptor work?

Answer 4

First an extra cellular ligand binds causing a confirmations change to the trimmer alpha beta gamma subunits. The GDP bound to alpha swaps and become GTP causing active forms to be taken. Alpha+GTP and Beta+Gamma.

Question 5

What does active form Alpha+GTP cause?

Answer 5

It effects effector enzymes such as adenylyl cyclase.

Question 6

What does the beta gamma subunit effect?

Answer 6

Ion channels and kinases

Question 7

Which subunit attaches to the membrane in a GCP?

Answer 7

Gamma is attached by a fatty acid chain

Question 8

What are ligand gated ion channels?

Answer 8

Channels that allow the flow of ions into the cell in response to binding of a chemical messenger to its respective receptor.

Question 9

What do ligand gated ion channels look like?

Answer 9

They are oligomeric receptors made up of 5 subunits that associate. Can be either homo or Hetero oligomeric.

Question 10

What is ligand gated ion channels transduction mechanism?

Answer 10

Binds agonist causing a conformational change. They then select specific ions to flux through membrane.

Question 11

How is a ligand gated ion channel organised?

Answer 11

Each ion channel has 4 subunits named. M1-4 and M2 is very important.

Question 12

Why is M2 subunit so important in ligand gated ion channels?

Answer 12

It’s close to the centre of the channel and forms the gate that ions pass through.

Question 13

What subunits make a ligand gated ion channel?

Answer 13

5 subunits: 2 alpha ,sigma,gamma and beta

Question 14

Where does acetylcholine bind on ligand gated ion channels?

Answer 14

It’s bind majorly to the alpha subunits and minorly to the neighbouring non alpha subunits.

Question 15

What are the key features of M2?

Answer 15

Hydrophobic amino acids with growing larger R groups towards bottom
Hydroxylated aminos desaturate ions (remove water)
Charged amino acid complementary to the ion charge allow flow

Question 16

What happens when ligand bind the ion channel?

Answer 16

When agonist binds N-terminal domain twists levering the M2 domain to cause it to form an open confirmation

Question 17

What are tyrosine linked receptors?

Answer 17

Single transmembrane domains that dimerise leading to phosphorylation that leads to intracellular recruitment of proteins that lead to downstream signalling.

Question 18

What is the tyrosine kinase transduction mechanism?

Answer 18

Activated by Ligand binding causing a conformational change and dimerisation. The dimerisation activates intrinsic tyrosine kinases and creates a site for phosphotyrosine or SH2 binding sites

Question 19

What are steroid receptors?

Answer 19

Class of molecules that when activated act as both signal transducers and transcription factors

Question 20

What is steroid receptors transduction mechanism?

Answer 20

Steroid binds receptors causing them to diffuse into the cell and bind HSP-90 receptors dimerise and release HSP-90 then bind to DNA activating transcription

Question 21

What is pharmagenomics?

Answer 21

How genetic variation effects the way in which a drug works. Controlled to ensure efficacy and reduce side effects

Question 22

Cytochrome P450 does what?

Answer 22

It performs oxidation reaction that cause detoxifying.

Question 23

How does Cytochrome P450 cause detoxifying?

Answer 23

• increase elimination
• inactivate/reduce potency
• generate toxic intermidiate

Question 24

What genomic changes can you have for cytochrome P450?

Answer 24

Gene deletion
Single copy
Gene duplication

Question 25

How does gene deletion effect metabolism?

Answer 25

No mRNA made so no enzyme meaning no metabolism

Question 26

How does a single copy effect metabolism?

Answer 26

• unstable enzyme -decrease
• stable enzyme - normal
• altered enzyme- other metabolites

Question 27

How does duplication of Cytochrome P450 gene effect metabolism?

Answer 27

Higher enzyme levels so increased drug metabolism