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_BBe1 w/wo siRho transfection were treated w/wo EGF and w/wo tyrphostin AG1478 (AG1478), wortmanin, or PD98059. Total and system-specific ³H-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 B⁰/ASCT2 and B^0,+ activities. Despite the doubling of membranal ASCT2 protein with EGF treatment, total ASCT2 did not change. The increases in B⁰/ASCT2 activity and ASCT2 protein were eliminated by AG1478, PD98059, wortmanin, and siRho, while transport by B^0,+ was inhibited only by PD98059 and siRho. Thus, differential pathways are involved in EGF-induced increase in B⁰/ASCT2 glutamine transport and membranal ASCT2 compared to those involved in B^0,+ activity.