Question

7) IF PTEN is overexpressed in a cel Ine (overexpression increase in production of F cells undergo apoptosis or an increase in cell growth and differentiation? Explain wny 8) A mutated EGFR receptor has been found in which the intracellular domains of the receptor was shown to be deleted. What would be the effect of such deletion of EGFR receptor function and downstream cellular functions?

Answer 1

1. PTEN (phosphatase and Tensin homolog) is a tumour suppressor Gene and found to be mutated in most cancers. Its overexpression cause apoptosis by downregulating AKT/ hTERT/PI3K pathway. PTEN encodes a protein with lipid phosphatase activity which can dephosphorylation PIP3 (phosphatidyl inositol 3, 4,5 triphosphate) into PIP2 there by preventing growth factor signal transduction pathway PIP3/ AKT.

2. EGFR protein tyrosine kinase has extracellular domain, intracellular domain, transmembrane domain. Intracellular domain has juxtamembrane region(JM region), tyrosine kinase domain(TKD) and C- terminal tail. JM region causes allosteric activation of tyrosine kinase and C-terminal domain causes dimerization and interaction of receptor. If there is mutation in intracellular domain then there will be no dimerization be of rreceptor and hence tyrosine kinase activation for transmission of signal.