Explain why inhibitors that prevent plasma membrane localiza

Solution

In MAPK pathway, the binding of growth hormone to the receptor in the plasma membrane causes dimerization of the receptor (conformational change) that result in autophosphorylation of tyrosine residues located on the intracellular domains of receptors. The binding of SH2-domain (src homology) to the phosphorylated tyrosine residues stimulates the exchange of GDP bound to Ras with the GTP, now the Ras is activated. Activated Ras activates Raf, Raf activates MEK kinase, MEK kinase activates MAPK, that is followed by a kinase cascade and finally gene transcription occurs in the nucleus. In many of the cancers, constituent activation of Ras is observed, which allows continuous cell division.

Thus, prevention of plasma membrane localization of Ras have been used in clinical trials for treatment of several tumors including colon cancer.