Lecture 14: ACTIVATION AND INHIBITION OF PROTEINS (PART 2)

Question 1

What does an active receptor start?

Answer 1

A chain of events where messages are passed on through the cell via a process called signal transduction

Question 2

What is signal transduction often?

Answer 2

Multi-step pathways that provide opportunities for coordination and regulation of the cellular response

Question 3

What can relay molecules be?

Answer 3

Proteins or chemical signals called second messengers

Question 4

What can second messengers do?

Answer 4

Transmit signals from a receptor to other relay molecules because they are not attached to the membrane and are free to move in the cell

Question 5

What do GPCR’s use to start signal transduction?

Answer 5

G proteins

Question 6

What does the GPCR do?

Answer 6

Activates the G protein, which communicates with other proteins in the cell

Question 7

What are the different types of G proteins?

Answer 7

Stimulatory G protein (G alpha s) and Inhibitory G protein (G alpha i)

Question 8

What does stimulatory G protein do?

Answer 8

Activates an enzyme called adenylate cyclase

Question 9

What does adenylate cyclase do?

Answer 9

Produce cAMP (a second messenger)

Question 10

What does cAMP do?

Answer 10

Activate kinase

Question 11

What does inhibitory G protein do?

Answer 11

Decreases the activity of adenylate cyclase

Question 12

What do RTK’s use to start signal transduction?

Answer 12

Phosphorylation of adaptor proteins

Question 13

What do adaptor proteins do?

Answer 13

Communicate with other proteins in the cell

Question 14

What do the different types of adaptor proteins have?

Answer 14

Different effects

Question 15

What do phosphorylation and dephosphorylation events do?

Answer 15

Turn activity on and off or up and down as required

Question 16

What is phosphorylation?

Answer 16

A widespread mechanism for regulating protein activity where protein kinases transfer phosphates from ATP to protein (phosphorylation)

Question 17

What do protein phosphates do?

Answer 17

Rapidly remove the phosphates from proteins (dephosphorylation) to carefully control signal transduction

Question 18

What activates ligand gated ion channels?

Answer 18

An agonist ligand that binds and causes a conformational change

Question 19

What happens when a ligand gated ion channel is activated?

Answer 19

Instead of relay molecules being activated, ions directly flow through the channel into the cell to produce effects

Question 20

Whaat receptors produce fast signalling?

Answer 20

Ligand gated ion channels

Question 21

What can responses be controlled by?

Answer 21

Where receptors are expressed

Question 22

What do different cells have?

Answer 22

Different collections of receptors and relay molecules, allowing cells to detect and respond differently to different ligands

Question 23

What can the same ligand receptor pairing have?

Answer 23

Different effects in different cells because they use different combinations of relay molecules for signal transduction

Question 24

What can further help the cell coordinate signals from incoming ligands?

Answer 24

Pathway branching and cross talk

Question 25

What happens in pathway branching?

Answer 25

The first protein activated further activates two proteins which each have individual cellular responses

Question 26

What happens in cross talk?

Answer 26

Two individual receptors each activate a protein and then the activated proteins act together to activate another protein

Question 27

What are insulin, glucagon and GLP-1 examples of?

Answer 27

Endogenous peptide ligands (hormones)

Question 28

What happens with insulin in muscle and adipose cells?

Answer 28

RTK receptor activation causes phosphorylation of an adaptor protein, and further signal transduction events, leading to GLUT-4 translocation

Question 29

What is GLUT-4?

Answer 29

A glucose transporter

Question 30

What is done with GLUT-4?

Answer 30

It is transported to the cell membrane to allow glucose to enter

Question 31

What happens with insulin in liver cells?

Answer 31

RTK receptor activation causes phosphorylation of an adaptor protein and further signal transduction events, leading to glycogen synthesis

Question 32

What happens with glucagon in the liver cells?

Answer 32

Receptor activation causes stimulatory G-protein activation and further signal transduction events, leading to glycogen breakdown

Question 33

Where is GLP-1 produced?

Answer 33

In the gut

Question 34

What does GLP-1 act on?

Answer 34

Pancreatic beta cells when we eat a meal

Question 35

What does GLP-1 receptor activation cause?

Answer 35

Stimulatory G protein activation and further signal transduction events, leading to insulin secretion