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Eukaryotic Cell, March 2009, p. 339-352, Vol. 8, No. 3
1535-9778/09/$08.00+0     doi:10.1128/EC.00270-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

AgtA, the Dicarboxylic Amino Acid Transporter of Aspergillus nidulans, Is Concertedly Down-Regulated by Exquisite Sensitivity to Nitrogen Metabolite Repression and Ammonium-Elicited Endocytosis ^,

Angeliki Apostolaki,^1, Zoi Erpapazoglou,^2, Laura Harispe,^1,3,¶ Maria Billini,² Panagiota Kafasla,^2,|| Dimosthenis Kizis,^2, Miguel Angel Peñalva,³ Claudio Scazzocchio,^1,4 and Vicky Sophianopoulou^2*

Institut de Génétique et Microbiologie, Université Paris-Sud, UMR8621, Orsay, France,¹ Institute of Biology, National Center for Scientific Research, Demokritos (NCSRD), Aghia Paraskevi 15310, Athens, Greece,² Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain,³ Department of Microbiology, Imperial College London, London, United Kingdom⁴

Received 10 August 2008/ Accepted 30 December 2008

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.

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* Corresponding author. Mailing address: Institute of Biology, National Center for Scientific Research, Demokritos (NCSRD), Aghia Paraskevi 15310, Athens, Greece. Phone: 302106503602. Fax: 302106511767. E-mail: vicky{at}bio.demokritos.gr

Published ahead of print on 23 January 2008.

Supplemental material for this article may be found at http://ec.asm.org/.

Present address: IMBB-FORTH, P.O. Box 1385, 71110 Heraklion, Crete, Greece.

Present address: Laboratoire Trafic Intracellulaire des Protéines dans la levure, Insitut Jacques Monod, UMR7592 CNRS-Universités Paris 6 et 7, Paris, France.

^¶ Present address: Laboratorio Tecnológico del Uruguay, Avda Italia 2601, Montevideo, Uruguay.

^|| Present address: Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.

Present address: Department of Agricultural Biotechnology, Agricultural University of Athens, Athens, Greece.

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Eukaryotic Cell, March 2009, p. 339-352, Vol. 8, No. 3
1535-9778/09/$08.00+0     doi:10.1128/EC.00270-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.