Intracellular Signalling

Question 1

• Give some examples of second messengers

Answer 1

cAMP, IP3 and Ca2+

Question 2

• What are receptor tyrosine kinases?

Answer 2

Receptors with the enzyme tyrosine kinase linked

Question 3

• What are the two key signalling pathways activated by RTK?

Answer 3

The MAP kinase (MAPK) and the PI3 kinase (PI3K) pathways – both involve Ras (a G protein)

Question 4

• What is the function of these pathways?

Answer 4

MAPK regulates cell growth, PI3K regulates cell growth and survival

Question 5

• What is the mitogen activated protein kinase pathway?

Answer 5

The first kinase is a MAP kinase kinase kinase (MAPKKK) called Raf
The former phosphorylates a MAP kinase kinase (MAPKK) called Mek
The former phosphorylates a MAP kinase (MAPK) called Erk
The former phosphorylates target proteins (transcription factors)

Question 6

• What are the main hormone stimulators of cell growth?

Answer 6

Insulin and members of the IGF family – activate PI3K which activates the kinase Akt (or protein kinase B)

Question 7

• What are the key actions of Akt?

Answer 7

Akt phosphorylates another kinase – mTOR (cell proliferation) & phosphorylates factors of the Bcl-2 family (inhibition of apoptosis)

Question 8

• What does insulin promote through activation of the MAPK pathway?

Answer 8

Cell growth

Question 9

• What does insulin promote through activation of the PI3K pathway?

Answer 9

Inhibits gluconeogenesis and glycogenolysis
Induces translocation of the glucose transporter to the membrane
Stimulates amino acid uptake and protein synthesis
Stimulates lipid synthesis and inhibits lipid metabolism

Question 10

• List some examples of receptors

Answer 10

Protein G coupled receptors (stimulatory, inhibitory, ras)
Tyrosine kinase receptor
(Serine/threonine kinase receptors are another type: cytokines)

Question 11

• List some examples of signal transduction enzymes

Answer 11

Adenylate cyclase
Phospholypase C
Tyrosine kinase