Question

MAPK pathway, TLR pathway, PPAR gamma signalling

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1.Pick one pathway and determine what process(es) does this pathway regulate and which class does this pathway belong to?

2.How is a signal transmitted from cell surface to nucleus, are second messengers involved, what kind of molecular interactions are involved? (e.g. phosphorylation, dimerization etc.)

Answer 1

##### Answer and Explantion #####

MAPK(Mitogen- Activated protein kinase) pathway

1. This pathway belongs to Receptor Tyrosine Kinases (RTKs) i.e Enzyme linked surface receptor, from RAS-MAP kinase pathway, here ligand binding with the receptors induces its tyrosine kinase activity and further with the help of some second messangers it starts the cascades of reactions , RAS is a mono meric GTPAse swich protein and functions in transducing signals from many different RTK (Receptor Tyrosine Kinases) this pathway plays very crucial role in the cell cycle and differentiation-specific proteins.
2. It is activated after binding with the ligand and receptor there are two receptors are present on the cell surface as ligand binds with receptors it leads to dimerization and autophosphorylation of tyrosines residues , where a on the membrane there are some other proteins GRB-2 and SOS, which on activating due to this phosphorylation and dimerization, SOS promotes the dissociation of GDP+Ras, into GTP+Ras as this conversion occurs, SOS dissociates from Ras, and in this way the active Ras pathway lead to signaling.

In MAPK pathway this Ras activation activates various second messangers like RAF , MEK and MAP kinase with the help of Ser-Thr phosphorylation, Tyr-Thr phosphorylation and Ser-Thr phosphorylation respectively, and at last this cascade results in the changes in protein activity and ultimately changes in gene expression.

Thanks