Signaling proteins

Question 1

What are the basic components of signal transduction pathways? (6)

Answer 1

1. The signal (Ligand)
2. The receptor (Receives signal)
3. Second messengers
4. Effector
5. Response (The end result)
6. Termination (The end)

Question 2

What are the different types of membrane receptors?

Answer 2

1. 7TM receptors (GPCRs)
2. Dimeric membrane receptors (Recruit Protein Kinases)
3. Dimeric protein receptors (ARE protein Kinases)

Question 3

How does G Protein-coupled signaling work? (Gs)

Answer 3

1. Ligand binds
2. Activation of G protein (Causes a conformational change in which the alpha subunit dissociates)
3. GTP Binding (To the alpha subunit) and G Protein Activation
4. Then the alpha subunit activates Adenyl cyclase (Gs) which turns ATP into cAMP
5. cAMP activates Protein Kinase A

Question 4

Summarize the mechanism of receptors that recruit and the mechanism of receptors that are protein kinases.

Answer 4

Receptors that Recruit Protein Kinases: Recruits kinases that phosphorylate other proteins in the cell causing them to take action
Receptors that are Protein Kinases: When activated act themselves as kinases that phosphorylate other proteins in the cell causing them to take action

Question 5

How does G Protein-coupled signaling work? (Gq)

Answer 5

1. Ligand binds
2. Activation of G protein (Causes a conformational change in which the alpha subunit dissociates)
3. GTP Binding (To the alpha subunit) and G Protein Activation
4. Phospholipase C is activated
5. Phospholipase turns PIP2 into both IP3 and DAG

Question 6

What do IP3 and DAG do?

Answer 6

IP3 causes a release of calcium from the endoplasmic reticulum (Calcium activates a lot)
DAG activates Protein Kinase C or PKC

Question 7

What is the helpful pneumonic device to help remember the G protein pathway?

Answer 7

(G)o to (AC) for (C)raps and (P)oker
G into AC into cAMP into PKA

Question 8

Summarize the change in PIP2 that occurs during insulin binding.

Answer 8

PIP2 is converted to PIP3 through phosphorylation by PI3K
PIP3 then activates downstream proteins like Akt, which are involved in metabolic processes, particularly those that help control blood sugar levels.

Question 9

What are the structural differences between the three different types of receptors?

Answer 9

7TM receptors: These receptors have seven alpha-helices
Dimeric Membrane Receptors that Recruit Protein Kinases Form Dimers upon activation
Dimeric Membrane Receptors that are Protein Kinases: Are Dimers