Can you please explain with lots of details ? The Epidermal Growth Factor Recept
ID: 226423 • Letter: C
Question
Can you please explain with lots of details ? The Epidermal Growth Factor Receptor (EGFR) is a receptor tyrosine kinase that regulates cell growth. For each of the scenarios below, explain which steps of RTK signaling would act normally and which would change. Describe what effects you would expect to observe in each cell. a. An inhibitor binds to the EGFR ligand binding site but does not induce dimerization. b. The tyrosine residues on EGFR are replaced with glycine residues. c. EGFR is mutated so that pairs dimerize all the time, even when ligand is absent.Explanation / Answer
Condition A.
To activate RTK signalling ligand has to bind to the receptor. Upon ligand binding receptor will dimerize and cross-phosphorylate tyrosine of the receptor. Tyrosine upon phosphorylation generate binding sites for proteins which have Src homology 2 (SH2) domain- and phosphotyrosine binding (PTB) domain proteins
If the inhibitor binds to the receptor then the ligand binding site will be occupied by it. As a result of it, the receptor will be unable to dimerize and RTK won't be able to change the transcription of various genes.
B. If we mutate all the tyrosine into glycine then in that case even if ligand binds to the receptor it won't be able to activate the RTK activity as all the tyrosine are mutated into glycine. As there is no phosphotyrosine which acts as docking site for proteins having SH2 domain and PTB domain leads to inhibition of genes which are activated by RTK
C. As we have seen that dimerization of receptor is required for the phosphorylation of the tyrosine. So if receptor are in dimerize form then it will constitutively phosphorylate tyrosine residue and all the genes that are regulated by RTK signalling will be in complete ON state