In human entrocytes, GLN transport and ASCT2 surface expression induced by short-term EGF are MAPK, PI3K, and Rho-dependent

Glutamine, a key nutrient for the enterocyte, is transported among other proteins by ASCT2. Epidermal growth factor (EGF) augments intestinal adaptation. We hypothesized that short-term treatment of human enterocytes with EGF enhances glutamine transport by increasing membranal ASCT2. To elucidate EGF-induced mechanisms, monolayers of C2(BBe)1 w/wo siRho transfection were treated w/wo EGF and w/wo tyrphostin AG1478 (AG1478), wortmanin, or PD98059. Total and system-specific H-3-glutamine transports were determined w/wo 5 mmol/l amino acid inhibitors. Total and membranal ASCT2 proteins were measured by Westerns. EGF doubled glutamine transport by increasing B-o/ASCT2 and B-o,B-+ activities. Despite the doubling of membranal ASCT2 protein with EGF treatment, total ASCT2 did not change. The increases in B-o/AS activity and ASCT2 protein were eliminated by AG1478, PD98059, wortmanin, and siRho, while transport by B-o,B-+ stop was inhibited only by PD98059 and siRho. Thus, differential pathways are involved in EGF-induced increase in B-o/ASCT2 glutamine transport and membranal ASCT2 compared to those involved in B-o,B-+ stop activity.