4What are two possible mechanisms by which signal transducti

4.What are two possible mechanisms by which signal transduction from a cytokine receptor may be stopped in the short term and in the long term?Although all activated cytokine receptor interact with SH2 domain-containing proteins,such as STATs, why specificity of the interactions will be ensured?[3marks]

Solution

The two possible mechanisms by which signal tranduction from cytokine receptor may be stopped in the short termed and in the long termed are:-

(i)To remove the ligand so that it can no longer access receptor.Ex-The tumour cells if at particular time can be stopped then it can be done by removing of ligands and thus the signal can be stopped.

(ii)The cAMP molecules activates the enzyme protein Kinase A which then phosphorelates multiple protein by attaching themselves with the phosphate groups. Later on whatever steps occur in the cascade,amplifies the initial signal and the phosphorelation reacts intervene in both short and long term responses.This cAMP is stopped by the degradation by the enzyme called Phosphodiesterase.

There are many other proteins of signaling cascade which interact with tyrosine kinase.In the SRC proto-oncogene these other proteins are identified as first proteins containing a domain of amino acid sequences that are homologous to a domain. These are known as SH2 domains whichhas approximately 100 ammino acids in length and these domains have different tyrosine phosphorylated residues based on the presence of the tyrosine phosphate aand the amino acid sequences surrounding the residue of tyrosine. This is the reason why specificity of the SH2 domain-containing proteins interactions will be ensured.