title: Asymmetric dimethylarginine is transported by the mitochondrial carrier SLC25A2.
abstract: Asymmetric dimethyl L-arginine (ADMA) is generated within cells and in mitochondria when proteins with dimethylated arginine residues are degraded. The aim of this study was to identify the carrier protein(s) that transport ADMA across the inner mitochondrial membrane. It was found that the recombinant, purified mitochondrial solute carrier SLC25A2 when reconstituted into liposomes efficiently transports ADMA in addition to its known substrates arginine, lysine, and ornithine and in contrast to the other known mitochondrial amino acid transporters SLC25A12, SLC25A13, SLC25A15, SLC25A18, SLC25A22, and SLC25A29. The widely expressed SLC25A2 transported ADMA across the liposomal membrane in both directions by both unidirectional transport and exchange against arginine or lysine. The SLC25A2-mediated ADMA transport followed first-order kinetics, was nearly as fast as the transport of the best SLC25A2 substrates known so far, and was highly specific as symmetric dimethylarginine (SDMA) was not transported at all. Furthermore, ADMA inhibited SLC25A2 activity with an inhibition constant of 0.38 ± 0.04 mM, whereas SDMA inhibited it poorly. We propose that a major function of SLC25A2 is to export ADMA from mitochondria missing the mitochondrial ADMA-metabolizing enzyme AGXT2. There is evidence that ADMA can also be imported into mitochondria, e.g., in kidney proximal tubulus cells, to be metabolized by AGXT2. SLC25A2 may also mediate this transport function.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Porcelli
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Longo
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Palmieri
authors.affiliation: Department of Pharmacology, University Medical Center of the Johannes Gutenberg-University, Obere Zahlbacher Strasse 67, 55101, Mainz, Germany.
authors.forename: Ellen I
authors.initials: EI
authors.lastname: Closs
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy. ferdpalmieri@gmail.com.
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Palmieri
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000637:Transaminases
chemical_list: D026923:Amino Acid Transport Systems, Basic; D002352:Carrier Proteins; C488998:SLC25A2 protein, human; C024917:symmetric dimethylarginine; C018524:N,N-dimethylarginine; D001120:Arginine; D000637:Transaminases; C019635:Alanine-glyoxylate transaminase
keywords: ADMA; Membrane transport; Mitochondria; Mitochondrial carrier; Mitochondrial transporter; SLC25A2