Expression of porcine jejunal excitatory amino acid carrier 1 (EAAC1) and glutamate transporter associated protein 3‐18 (GTRAP3‐18) during postnatal development

Abstract

The excitatory amino acid carrier 1 (EAAC1) is expressed in both the small bowel and the central nervous system and is responsible for the homeostasis of the neurotransmitter L‐glutamate. Glutamate transporter associated protein 3‐18 (GTRAP3‐18) is an inhibitory regulator of EAAC1 by affecting its trafficking and through protein‐protein interactions. We examined jejunal EAAC1 protein and mRNA abundances and GTRAP3‐18 protein abundance during the postnatal development in pigs at the ages of d 1, 4, 6, 12, 20, 28 (1‐wk post‐weaning), and 70 (mature gut), respectively. There were linear decreases (P<0.05) in the jejunal EAAC1 and GTRAP3‐18 protein abundances in homogenate, cytosol and the apical membrane, whereas a cubic pattern was observed (P<0.05) in the jejunal EAAC1 mRNA abundance during postnatal growth. Furthermore, EAAC1 protein abundances were correlated with GTRAP 3‐18 protein abundances in homogenate (r=0.92, P<0.01), cytosol (r=0.91, P<0.01) and the apical membrane (r=0.81, P<0.01), respectively. However, the EAAC1 protein abundances in jejunal homogenate, cytosol and the apical membrane were poorly correlated (P>0.05) with jejunal EAAC1 mRNA abundance. These results suggest that there is a postnatal decrease in the jejunal EAAC1 expression likely regulated at the post‐transcriptional level. A parallel decline in GTRAP3‐18 protein abundance may further reduce EAAC1 function in the jejunum during postnatal growth. Supported by NSERC Discovery Program of Canada.