Activity and protein localization of multiple glutamate transporters in gestation day 14 vs. day 20 rat placenta.
Concentrative absorption of glutamate by the developing placenta is critical for proper fetal development. The expression of GLAST1, GLT1, EAAC1, and EAAT4, known to be capable of D-aspartate-inhibitable and Na(+)-coupled glutamate transport (system X-AG), was evaluated in day 14 vs. day 20 rat chorioallantoic placenta. Steady-state mRNA levels were greater at day 20 for all transporters. Immunohistochemistry determined that the expression of GLAST1, GLT1, and EAAC1 was greater throughout the day 20 placenta and was asymmetric with respect to cellular localization. EAAT4 protein was not detected. System X-AG activity was responsible for most of the Na(+)-dependent glutamate uptake and was greater in day 20 than in day 14 apical and basal membrane subdomains of the labyrinth syncytiotrophoblast. Greater quantities of EAAC1 and GLAST1 protein were identified on day 20, and quantities were greater in basal than in apical membranes. GLT1 expression, unchanged in apical membranes, was decreased in basal membranes. These data correlate transporter mRNA and protein content with transport activity and demonstrate an increasing capacity for glutamate absorption by the developing placenta.
Matthews
J C
JC
Department of Pediatrics, University of Florida College of Medicine, Gainesville 32610, USA.
Beveridge
M J
MJ
Malandro
M S
MS
Rothstein
J D
JD
Campbell-Thompson
M
M
Verlander
J W
JW
Kilberg
M S
MS
Novak
D A
DA
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D050581:Excitatory Amino Acid Transporter 4; D005865:Gestational Age; D050491:Glutamate Plasma Membrane Transport Proteins; D005971:Glutamates / Q000378:metabolism; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D027981:Symporters
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D002352:Carrier Proteins; D018076:DNA, Complementary; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D050581:Excitatory Amino Acid Transporter 4; D050491:Glutamate Plasma Membrane Transport Proteins; D005971:Glutamates; D012333:RNA, Messenger; D017470:Receptors, Glutamate; C493398:Slc1a1 protein, rat; C493392:Slc1a3 protein, rat; C493389:Slc1a6 protein, rat; D027981:Symporters; D012964:Sodium