| Research Abstract |
An epidermal growth factor receptor (EGFR) highly expressing human squamous cell carcinoma cell line, A431. which was cultured with a medium containing 20g/L of glucosefor adaptation of the cells to high glucose condition, showed moderate growth retardation (doubling time, 49h) as compared with that with normo-concentration of glucose (doubling time, 33h). A431 cultured with high glucose condition (HC) contained relatively elevated concentration of two forms of ubiquitin (multiubiquitin chain, MU, 100ng/mg protein and free ubiquitin, FU, 250ng/mg protein), which was almost similar to that in original A431 cells (NC). When HC was cultured at 4ﾟC, EGFR concentration determined with ELISA was 124U, which was approximately equal level to that In NC (115U). Under the conventional culture conditions at 37ﾟC, EGFR concentration in NC slightdccreased. By contrast, the receptor concentration in HC decreased extremely up to half level at 4ﾟC culture because of enhanced metabolism and down regula
… More
tion of EGFR.Immunoprecipitated EGFR in HC reacted with an antibody against advanced glycation endoproduct, but not in NC.By incubation of cells with EGF, increased levels of ubiquitinated EGFR were detectable clearly using an ELISA specific to ubiquitinated EGFR as well as a procedure of EGFR-immunoprecipitation followed by western blot by an anti-ubiquitin antibody. By western blot analysis, EGF-stimulated EGFR phosphorylation was also reduced in intensity in HC compared to in NC.These results indicated that the hyperglucose condition, such as diabetic condition, might induce the unusual down regulation of the EGFR with structural abnormality in the molecule. These results also suggested that some signal transduction pathways, namely via receptor type tyrosine phosphorylation mechanism. might be obstructed under such environment. To determine the effect on expression of EGFR-mRNA and whether presence or absence of site directed glycation of EGFR under the high glucose environment will be necessary to elucidate the diabetic status and cancer incidence. Less
|
