D-Serine, synthesized endogenously in the brain, is an important modulator of glutamatergic neurotransmission. Since colonic bacteria produce D-serine, we asked the question whether there are transport mechanisms in the colon that might make this exogenously produced D-serine available to the host. Here we identify for the first time an amino acid transporter in the intestine for high-affinity active transport of D-serine. This transporter, called ATB0,+, is a Na+- and Cl−-coupled transporter for L-enantiomers of neutral and cationic amino acids. Here we demonstrate that ATB0,+ is also capable of mediating the Na+- and Cl−-coupled transport of D-serine. The affinity of ATB0,+ for L-serine and D-serine is similar, the Kt value for the two enantiomers being ∼150 μM. In addition to D-serine, ATB0,+ transports D-alanine, D-methionine, D-leucine, and D-tryptophan. However, several other neutral and cationic amino acids that are transportable substrates for ATB0,+ as L-enantiomers are not transported when presented as D-enantiomers. ATB0,+ is expressed in the intestinal tract, interestingly not in the proximal intestine but in the distal intestine. Expression is most predominant in the colon where the transporter is localized to the luminal membrane of colonocytes, making this transporter uniquely suitable for absorption of bacteria-derived D-serine.
|Original language||English (US)|
|Number of pages||5|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Jan 1 2002|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology