Autophosphorylation activation and inhibition by curcumin of the epidermal growth factor receptor reconstituted in liposomes.

ABSTRACT

The epidermal growth factor receptor (EGFR) is a 170-kDa transmembrane protein with intrinsic protein kinase activity. It is involved in the regulation of essential cellular processes such as proliferation, differentiation, survival, and migration. An increase in EGFR activity has been correlated to malignant evolution of the cells. We have used proteoliposomes as a platform to study the mechanism of activation and inhibition of EGFR. We have been able to reconstitute functional EGFR in liposomes through detergent removal by Bio-Beads and have measured the receptor dimerization and its autophosphorylation resulting from its inherent tyrosine kinase activity. In particular, we have studied the activation of autophosphorylation by the natural ligand epidermal growth factor and its inhibition by curcumin, a polyphenol from Curcuma longa. This artificial membrane model provides a convenient tool to both qualitatively and quantitatively elucidate the mechanism of activation and inhibition of EGFR. It allows studying the isolated receptor under well-defined conditions, which enables one to use a number of biochemical and physico-chemical techniques that are difficult to put into practice with living cells. We believe that this platform can be used as a systematic screening tool for membrane receptor modulators, which are potential drug candidates.