AgtA, the dicarboxylic amino acid transporter of Aspergillus nidulans, is concertedly down-regulated by exquisite sensitivity to nitrogen metabolite repression and ammonium-elicited endocytosis.
We identified agtA, a gene that encodes the specific dicarboxylic amino acid transporter of Aspergillus nidulans. The deletion of the gene resulted in loss of utilization of aspartate as a nitrogen source and of aspartate uptake, while not completely abolishing glutamate utilization. Kinetic constants showed that AgtA is a high-affinity dicarboxylic amino acid transporter and are in agreement with those determined for a cognate transporter activity identified previously. The gene is extremely sensitive to nitrogen metabolite repression, depends on AreA for its expression, and is seemingly independent from specific induction. We showed that the localization of AgtA in the plasma membrane necessitates the ShrA protein and that an active process elicited by ammonium results in internalization and targeting of AgtA to the vacuole, followed by degradation. Thus, nitrogen metabolite repression and ammonium-promoted vacuolar degradation act in concert to downregulate dicarboxylic amino acid transport activity.
Apostolaki
Angeliki
A
Institut de Génétique et Microbiologie, Université Paris-Sud, UMR8621, Orsay, France.
Erpapazoglou
Zoi
Z
Harispe
Laura
L
Billini
Maria
M
Kafasla
Panagiota
P
Kizis
Dimosthenis
D
Peñalva
Miguel Angel
MA
Scazzocchio
Claudio
C
Sophianopoulou
Vicky
V
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000600:Amino Acids, Dicarboxylic / Q000378:metabolism; D001233:Aspergillus nidulans / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D015536:Down-Regulation; D004705:Endocytosis; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D026905:Amino Acid Transport Systems; D000600:Amino Acids, Dicarboxylic; D005656:Fungal Proteins; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen