Question

Ras is a GTP-binding protein that is often mutated in cancer cells. Normal cells are stimulated to divide by receiving a signal from a growth factor through a receptor tyrosine kinase. When the receptor tyrosine kinase binds the growth factor, Ras is stimulated to bind GTP. Ras in turn activates proteins that promote cell proliferation. A common mutation in cancerous cells causes Ras to behave as though it were bound to GTP all the time. Suppose that there is a drug that can turn off the activity of the receptor tyrosine kinase by preventing its ability to dimerize. Do you think that this drug will inhibit the division of cells that have a mutated Ras protein that acts as though it were always bound to GTP? (2 points) Explain your answer (2 points)

Answer 1

Ans:- No, drug will not be able to inhibit the division of the cells. Let see why the drug is unable to inhibit the cell division even if it inhibits RTK ( receptor tyrosine kinase) dimerization.

If you see the receptor tyrosine kinase signalling, the signal binds to the RTK it leads to the dimerization of RTK and phosphorylation. This phosphorylated receptor recruits adapter protein and ras via adapter protein. Now, Ras GDP (inactive form) will be converted into Ras-GTP (active) form. This Ras GTP will activate various factors that will finally assist in cell proliferation. Now, Ras-GTP is at the downstream of the RTK. Once Ras is mutated in such a way that it is Ras GTP, then even if the signal is not transmitted from RTK. It will activate downstream regulator for cell proliferation. Thus, the drug which inhibit the dimerization of RTK won't be able to inhibit Ras as Ras mutant now is activated all the time. So, it is not a good idea use drug to block the Ras mutant activity via inhibiting RTK.

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