Epidermal growth factor activation of intestinal glutamine transport is mediated by mitogen-activated protein kinases.
Glutamine is an essential nutrient for gut functions, but the regulation of its uptake by intestinal mucosal cells is poorly understood. Given the pivotal role of epidermal growth factor (EGF) in regulating gut metabolism, growth, and differentiation, this in vitro study was designed to investigate the intracellular signaling pathways involved in the regulation of EGF-mediated intestinal glutamine transport in intestinal epithelia. Continuous incubation with EGF (>30 hours, 100 ng/ml) stimulated glutamine transport activity across intestinal epithelial Caco-2 cell apical membrane. Exposure to EGF for 48 hours resulted in an increase in transport activity (50%) and glutamine transport system B gene ATB(0) mRNA levels (ninefold). EGF stimulated glutamine transport activity by increasing the glutamine transporter maximal velocity (V(max)) without altering the transporter apparent affinity (K(m)). Furthermore, EGF stimulated both intracellular protein kinase C and mitogen-activated protein kinase MEK1/2 activities. The EGF-stimulated glutamine transport activity was attenuated individually by the specific protein kinase C inhibitor chelerythrine chloride and the mitogen-activated protein kinase MEK1 inhibitor PD 98059. These data suggest that EGF activates glutamine transport activity across intestinal epithelial membrane via a signaling mechanism that involves activation of protein kinase C and the mitogen-activated protein kinase MEK1/2 cascade. EGF activates glutamine transport via alterations in transporter mRNA levels and the number of functional copies of transporter units.
Wolfgang
Christopher L
CL
Department of Surgery, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Lin
ChengMao
C
Meng
QingHe
Q
Karinch
Anne M
AM
Vary
Thomas C
TC
Pan
Ming
M
D026962:Amino Acid Transport System ASC / Q000032:analysis; D001692:Biological Transport; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000502:physiology*; D005973:Glutamine / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism
D026962:Amino Acid Transport System ASC; D002352:Carrier Proteins; D015778:Minor Histocompatibility Antigens; C420506:SLC1A5 protein, human; C037853:glutamine transport proteins; D005973:Glutamine; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases