Regulation of the glutamate transporter by amino acid deprivation and associated effects on the level of EAAC1 mRNA in the renal epithelial cell line NBL-I.
The glutamate transport system of the bovine renal epithelial cell line NBL-1 was studied. The Km for Na(+)-dependent glutamate transport was found to be 13.8 +/- 2.4 microM (Vmax. 365 +/- 19.2 pmol/3 min per mg) and for Na(+)-dependent aspartate transport 4.5 +/- 1.1 microM (Vmax. 108 +/- 6.3 pmol/3 min per mg). The Km values are in close agreement with those expected for high-affinity Na(+)-dependent glutamate transport by System XAG-. Upon deprivation of amino acids, the Vmax. for Na+/aspartate co-transport rose to 203 +/- 6.0 pmol/3 min per mg (Km 3.8 +/- 0.5 microns). A probe was constructed to the high-affinity excitatory amino acid carrier (EAAC1) [Kanai and Hediger (1992) Nature (London) 360, 467-471]. The probe hybridized to a 3.5 kb transcript. On deprivation of amino acids, the level of EAAC1 mRNA decreased sharply before the measurable increase in transport levels, but was subsequently restored to control levels. A motif, which we propose is linked to amino acid deprivation, was found in the EAAC1 primary sequence.
Plakidou-Dymock
S
S
Department of Biochemistry, University of Bristol, School of Medical Sciences, U.K.
McGivan
J D
JD
D000595:Amino Acid Sequence; D027322:Amino Acid Transport System X-AG; D000596:Amino Acids / Q000008:administration & dosage*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport; D002417:Cattle; D002460:Cell Line; D004848:Epithelium / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology
D027322:Amino Acid Transport System X-AG; D000596:Amino Acids; D006023:Glycoproteins; D012333:RNA, Messenger; D001224:Aspartic Acid; D012964:Sodium