Effect of epidermal growth factor on leucine aminopeptidase in human colon (CACO-2) cells

To investigate the role of epidermal growth factor (EGF) in human milk on protein digestion in intestinal cells, the effects of EGF on leucine aminopeptidase (LAP) activity and on LAP protein were examined in human colon adenocarcinoma (Caco-2) cells. The Caco-2 cells were grown in MEM supplemented with 20% fetal bovine serum, 50 U/ml penicillin and 50 μg/ml streptomycin. Upon 80% confluency, the cells were switched to serum-free MEM for 24 h. The cells were then incubated with EGF at 0, 5 (close to human milk concentration), 50 or 250 nM for 24 h. The total cellular protein content was significantly higher in the 5 nM EGF treatment group (1.76 ± 0.67 ng/cell) than others, although the cell numbers were similar among the groups. The LAP activity was slightly lower in the EGF treatment groups (78% - 86% of control). The LAP protein (MW 53 kDa) separated by 10% SDS-PAGE and detected by western blotting in the EGF treatment groups was also slightly lower (86% - 93% of control). In summary, EGF treatment increased protein content, but slightly decreased LAP activity and protein on the cell membranes of Caco-2 cells.