Question

2A. Using the figure below, label and describe how Raskets activated (define GEF and GAP in your answer) C -GTP 23. Describe two points at which the signaling of Ras can be dysregulated to allow Ras to be constitutively activated, allowing continuous signaling to downstream effectors. 5 2C. Briefly, Describe one of the following two pathways downstream of activated Ras (PI3K/PTEN or Raf/MEK/ERK), describing how that specific pathway promotes cancer by discussing each schematic P Rat MAP3K 3 PMEKUZ MAP2K PTEN O ERK1/2 МАРК APK

Answer 1

Ras in inactive form is bound to GDP , an enzyme GEF exchange the GDP with GTP and activates the Ras , then Ras with the help of G ATPase protein activates it's GTPase activity and it is back converted to Ras GDP.

2B. GEP is hyperactivated that will lead to constitutive activation of Ras or if GAP is mutated so that it become non-functional even then Ras will be constitutively activated.

aC. On Ligand binding To receptor , receptor dimerization takes place and cross phosphorylation will occur and it will recruit Grb2 an adapter protein that will further bind to SOS a GEF , that will activate RAS. Ras will further activate MAP3k followed by MAP2K then MAPK . This activated MAPK will act on targets present in cytoplasm and nucleus . Continuous activation of this pathway lead to excessive proliferation of cell that can drive a cell towards tumour.