Question

1. Compare and contrast the regulation of Ras with trimeric G proteins.
2. Outline one mechanism used by activated mTOR to increase global translation in the cell.
3. Explain how phospholipase C hydrolysis of PIP₂ leads to activation of Protein Kinase C.

Answer 1

In eukaroytes, there are broadly two type of cell singnaling pathways one is GPCR and another one is TK

1) GPCR- G protein coupled receptor is 7 transmembrane protein which bind to singnal molecule like epinephrine aaya N terminus located toward extracellular side which after binding activates C terminus toward cytoplasmic site which is attached to Galpha protein which get activated by exchanging with GDP to GTP and activated form of Galpha dissociate from Gbeta and G gamma trimeric protein and start cascade pathways of cell signalling.

Gaplha- protein activates phospholipase C (PLC) which convert Phosphotidylinositol into diacyl glycerol(DAG) and phosphptidyl inositol triphosphophate (PIP3). PIP3 cause release of Ca2+ from endoplasmic reticulum and DAD along with Ca2+ activates Protein kinase C.

2) TK receptor (tyrosin kinase) is single pass transmembrane associated with dimer when get activated with growth factor and it's c terminus get activated and have kinase kind of property which phosphorylate Sos protein which activates Grb2 protein and finally Grb2 activates GEF protein which phosphorylate Ras to convert from inactive to active which start cascade signal pathway downstram. One of cascade pathway of Ras invlude mTOR pathways which act as regulation in translation of different prptein.

Hope it's clear..thanks