L3- Drug Targets

Question 1

How do glucocorticoid receptors (GCRs) work?

Answer 1

• steroid passes through the membrane, as it’s lipid soluble
• Once inside the cell, it can interact with the GCRs
• GCRs normally bound to Heat Shock Proteins (HSP)
• Steroid causes HSP to dissociate
• Receptors then dimerize and enter nucleus

Question 2

What happens in the standard model NHR after translocation to the nucleus, in transactivation?

Answer 2

• The NHR dimer biinds to a section of DNA known as a hormone responsive element (HRE) (or GRE in GCRs)
• It is then able to recruit coactivator proteins and RNA polymerase and promote transcription

Question 3

What happend in transrepression?

Answer 3

• Transcription is promoted y a transcription factor
• GCR binding to this transcription factor inhibits transcription.
• Transrepressionn involves receptor MONOMERS (and not the receptor binding to DNA)

Question 4

WHat’s the general strucutre of GPCRs?

Answer 4

7 transmembrane domains with NH2 terminus outside the cell. G protein binding domain on the 3rd intracellular loop.

Question 5

What are the types of muscarinic acetylcholine receptors?

Answer 5

M1-M5

Question 6

What’s the process of G protein coupled signalling?

Answer 6

1. G protein has GDP bound to it
2. Agonist binds to GPCR, GDP replaced by GTP at G protein
3. The binding of GTP triggers G protein to split in 2. (alpha goes off with GTP)
4. Both parts activate target proteins/signals
5. Alpha subunit hydrolyses GTP to GDP + Pi. This terminates the signalling process

Question 7

What is one of the most important intracellular second messengers in GPCRs?

Answer 7

cyclic AMP. (cAMP)

Question 8

What are some of the ligands that are coupled to cAMP production?

Answer 8

1. Adrenaline
2. Noradrenaline
3. Glucagon
4. Dopamine

Question 9

How is cyclic AMP made?

Answer 9

It’s produced from ATP by the enzyme adenylate cyclase. (aka adenylyl cyclase)

Question 10

What is cAMP’s main effect?

Answer 10

To switch protein kinases from inactive to active conformation

Question 11

Which G protein enhances the activity of adenylate cyclase?

Answer 11

Gs (stimulatory)

Question 12

Which G protein inhibits cAMP production?

Answer 12

Gi (inhibitory)

Question 13

What is IP3?

Answer 13

Inositol tris phosphate.

(It’s the phosphosugar head group of the lipid phosphotidylinositol bis phosphate. Head group of glycerol with 2 fatty acid chains and one phosphosugar group attached)

Question 14

What is the function of phospholipase C?

Answer 14

To split PIP2 into 2 parts

1. diacyl glycerol (DAG)
2. The head group- IP3

Question 15

When PIP2 is split into 2 parts, what can these components act as?

Answer 15

Can both act as second messengers.

DAG- remains in membrane and activate protein kinase C

IP3- released into the cytoplasm and travels to the ER. There it binds to specific receptors and causes the release of calcium from the intracellular stores.

Question 16

When calcium is released from intracellular stores what does it do?

Answer 16

It can act as a messenging molecule itself, but also enhances the activity of protein kinase C

Question 17

What is PLC activated by?

Answer 17

Gq

Question 18

If proteins are regulated by calcium release or by PKC, what else does it mean they’re regulated by?

Answer 18

PLC activity- as PLC splits PIP2 into 2 parts which then release Ca and activate PKC

Question 19

What are orphan receptors?

Answer 19

Receptors for which the endogenous ligand has not yet been identified.

Question 20

How do drugs interact with lipids? 2 ways

Answer 20

1. Disrupt the bilayer structure, affecting protein strcutures
2. Drugs form a conducting pathway across the membrane and so disrupt the electrochemistry of the cell

Question 21

How do drugs interact with DNA? 2 ways

Answer 21

1. covalently modify DNA bases
2. Intercalate themselves between bases

Question 22

Whats the difference between drug interactions between lipids and DNA and receptor proteins?

Answer 22

Receptor proteins form very specific interactions with drugs

There’s a finite number of each type of protein in a cell which means there’s a limiting number of binding sites.

Question 23

What makes up the primary structure of proteins?

Answer 23

Chain of amino acids linked via amide bonds

Question 24

What are examples of secondary stuctures?

Answer 24

alpha helices and beta sheets

Question 25

What’s electrostatic bonding?

Answer 25

charge-charge interaction between groups with permanent/temporary charges. v. stong

Question 26

What’s H bonding?

Answer 26

When two electronegative atoms “share” a hydrogen

Question 27

What does hydrophobic bonding cause?

Answer 27

an increase in entropy

Question 28

What causes van der waals bonds to form?

Answer 28

temporary local dipoles that allow a general interaction between molecules

Question 29

What can drugs bond with in proteins?

Answer 29

R groups

or

Peptide backbone

Question 30

In biochem what direction do d/+ or L/- rotate light?

Answer 30

d/+ clockwise

l/- anticlockwise

Question 31

Which isomer of noradrenaline is more natural and active?

Answer 31

The R form (natural)

Question 32

What’s a pharmacophore?

Answer 32

3D arrangement of functional groiups necessary for biological activity

Question 33

How does steroeisomerism affect binding?

Answer 33

For example one enantiomer will have 3 points of attachment, its mirror image may only have 2 points so it has lower affinity