General info/examples

Question 1

RTK causing Ca2+ release

Answer 1

PLC gamma activation

Question 2

Ras and cancer

Answer 2

Hyperacrtive mutant forms of RAS are locked resistant to GAP mediated GTPase stimulation and are locked permanently in the GTP-bound active state, which is why they promote the development of cancer.

Question 3

PI3K and PIP3

Answer 3

-Catalyses phosphorylation of the 3 position hydroxyl of the inositol ring to generate PIP3. PIP3 remains in the membrane until a specific phospoinositide phosphatase dephosphorylates it i.e. PTEN. Dysfunctional PTEN is associated with cancer as PIP3 promotes uncontrolled cellular growth.
-PIP3 recognises proteins with pleckstrin like domains
NOTE: PI3K activated by the BG unit of Gq proteins

Question 4

PI3K and AKT signalling

Answer 4

Insulin and insulin like growth hormones bind to specific RTKS causing PI3K to produce PIP3. PIP3 recruits Akt(AKA PKB) and phosphaoinositide dependent protein kinase (PKD1) which activated Akt. Akt phosphotylates and inhibits Tsc2 promoting the activation of RHEB (GTP) which activates the MTOR complex leading to cell growth.