The Na+-dependent neutral amino acid (AA) exchanger ASCT2 (ATB0) plays an important role in the apical exchange of large neutral AAs such as glutamine (Gln) and leucine (Leu) and is essential to maintaining gut mucosal growth. The objectives of this study were to investigate expression of the ASCT2/ATB0 (SLC1A5) gene and the key mechanistic (mammalian) target of rapamycin (mTOR) signaling components in epithelia along the jejunal crypt– villus axis in young pigs fed a liquidmilk replacer. Reverse transcription polymerase chain reaction (RT-PCR) analyses showed that the ASCT2/ATB0 (SLC1A5) gene mRNA abundance was higher (P < 0.05) in the crypt than in the upper villus and the middle villus cells. There were no differences (P > 0.05) in the ASCT2/ATB0 protein abundances in the cell homogenate, the intracellular fraction, and the apical membrane among the upper villus, middle villus, and crypt cells. Abundance of phosphorylated mTOR (p-mTOR) protein was higher (P < 0.05) in the middle villus than in the upper villus cells. Phosphorylated p70 S6 kinase protein (p-S6K1) abundance was higher (P < 0.05) in the crypt than in the upper villus cells. Thus, the ASCT2/ATB0 (SLC1A5) gene mRNA and protein ATB0 and the key mTOR-signaling components, p-mTOR and p-S6K1, were expressed in the epithelia along the entire jejunal crypt–villus axis in the young pigs fed a liquid milk replacer.
Bibliographical noteFunding Information:
We are grateful to Dr. Nelly E. Avissar from the University of Rochester Medical Center in providing the goat antirabbit ASCT2/ATB0 AA exchanger antibody for this research. This project was funded from the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Program and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) ? the University of Guelph Partnership Program (to M.Z. Fan).
- Mechanistic (mammalian) target of rapamycin signaling
- Small intestinal crypt–villus axis
- System ASC sodium-dependent neutral AA exchanger 2
- Young pigs