EAAT1 is involved in transport of L-glutamate during differentiation of the Caco-2 cell line.
Little is known concerning the expression of amino acid transporters during intestinal epithelial cell differentiation. The transport mechanism of L-glutamate and its regulation during the differentiation process were investigated using the human intestinal Caco-2 cell line. Kinetic studies demonstrated the presence of a single, high-affinity, D-aspartate-sensitive L-glutamate transport system in both confluent and fully differentiated Caco-2 cells. This transport was clearly Na(+) dependent, with a Hill coefficient of 2. 9 +/- 0.3, suggesting a 3 Na(+)-to-1 glutamate stoichiometry and corresponding to the well-characterized X(A,G)(-) system. The excitatory amino acid transporter (EAAT)1 transcript was consistently expressed in the Caco-2 cell line, whereas the epithelial and neuronal EAAT3 transporter was barely detected. In contrast with systems B(0) and y(+), which have previously been reported to be downregulated when Caco-2 cells stop proliferating, L-glutamate transport capacity was found to increase steadily between day 8 and day 17. This increase was correlated with the level of EAAT1 mRNA, which might reflect an increase in EAAT1 gene transcription and/or stabilization of the EAAT1 transcript.
Institut National de la Recherche Agronomique, Laboratoire de Nutrition Humaine et Physiologie Intestinale, Institut National Agronomique Paris-Grignon, France.
A
A
Mordrelle
E
E
Jullian
C
C
Costa
E
E
Cormet-Boyaka
R
R
Benamouzig
D
D
Tomé
J F
JF
Huneau
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D027322:Amino Acid Transport System X-AG; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D017931:DNA Primers; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D015870:Gene Expression / Q000502:physiology; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D027981:Symporters
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D002352:Carrier Proteins; D017931:DNA Primers; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; D012333:RNA, Messenger; C493400:SLC1A1 protein, human; C493394:SLC1A3 protein, human; D027981:Symporters; D018698:Glutamic Acid