Publications

• Human cationic amino acid transporter hCAT-3 is preferentially expressed in peripheral tissues.

  Vekony N., Wolf S., Boissel J.-P., Gnauert K., Closs E.I.

  At least five distinct carrier proteins form the family of mammalian cationic amino acid transporters (CATs). We have cloned a cDNA containing the complete coding region of human CAT-3. hCAT-3 is glycosylated and localized to the plasma membrane. Transport studies in Xenopus laevis oocytes reveale ... >> More

  At least five distinct carrier proteins form the family of mammalian cationic amino acid transporters (CATs). We have cloned a cDNA containing the complete coding region of human CAT-3. hCAT-3 is glycosylated and localized to the plasma membrane. Transport studies in Xenopus laevis oocytes revealed that hCAT-3 is selective for cationic L-amino acids and exhibits a maximal transport activity similar to other CAT proteins. The apparent substrate affinity and sensitivity to trans-stimulation of hCAT-3 resembles most closely hCAT-2B. This is in contrast to rat and murine CAT-3 proteins that have been reported to display a very low activity and to be inhibited by neutral and anionic L-amino acids as well as D-arginine (Hosokawa, H., et al. (1997) J. Biol. Chem. 272, 8717-8722; Ito, K., and Groudine, M. (1997) J. Biol. Chem. 272, 26780-26786). Also, in adult rat and mouse, CAT-3 has been found exclusively in central neurons. Human CAT-3 expression is not restricted to the brain, in fact, by far the highest expression was found in thymus. Also in other peripheral tissues, hCAT-3 expression was equal to or higher than in most brain regions, suggesting that hCAT-3 is not a neuron-specific transporter. << Less

  Biochemistry 40:12387-12394(2001) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Transport of cationic amino acids by the mouse ecotropic retrovirus receptor.

  Kim J.W., Closs E.I., Albritton L.M., Cunningham J.M.

  Susceptibility of rodent cells to infection by ecotropic murine leukaemia viruses (MuLV) is determined by binding of the virus envelope to a membrane receptor that has multiple membrane-spanning domains. Cells infected by ecotropic MuLV synthesize envelope protein, gp70, which binds to this recept ... >> More

  Susceptibility of rodent cells to infection by ecotropic murine leukaemia viruses (MuLV) is determined by binding of the virus envelope to a membrane receptor that has multiple membrane-spanning domains. Cells infected by ecotropic MuLV synthesize envelope protein, gp70, which binds to this receptor, thereby preventing additional infections. The consequences of envelope-MuLV receptor binding for the infected host cell have not been directly determined, partly because the cellular function of the MuLV receptor protein is unknown. Here we report a coincidence in the positions of the first eight putative membrane-spanning domains found in the virus receptor and in two related proteins, the arginine and histidine permeases of Saccharomyces cerevisiae (Fig. 1), but not in any other proteins identified by computer-based sequence comparison of the GenBank data base. Xenopus oocytes injected with receptor-encoding messenger RNA show increased uptake of L-arginine, L-lysine and L-ornithine. The transport properties and the expression pattern of the virus receptor behave in ways previously attributed to y+, the principal transporter of cationic L-amino acids in mammalian cells. << Less

  Nature 352:725-728(1991) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Asymmetric dimethylarginine is transported by the mitochondrial carrier SLC25A2.

  Porcelli V., Longo A., Palmieri L., Closs E.I., Palmieri F.

  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 recomb ... >> More

  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. << Less

  Amino Acids 48:427-436(2016) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• The renal transport protein OATP4C1 mediates uptake of the uremic toxin asymmetric dimethylarginine (ADMA) and efflux of cardioprotective L-homoarginine.

  Taghikhani E., Maas R., Fromm M.F., Koenig J.

  Elevated plasma concentrations of the uremic toxin asymmetrical dimethylarginine (ADMA) and low plasma concentrations of L-homoarginine are independently associated with cardiovascular events and total mortality. Enzymes degrading ADMA [dimethylaminohydrolase 1 (DDAH1)] and synthesizing L-homoargi ... >> More

  Elevated plasma concentrations of the uremic toxin asymmetrical dimethylarginine (ADMA) and low plasma concentrations of L-homoarginine are independently associated with cardiovascular events and total mortality. Enzymes degrading ADMA [dimethylaminohydrolase 1 (DDAH1)] and synthesizing L-homoarginine [L-arginine:glycine amidinotransferase (AGAT)] are expressed in human proximal tubule cells. So far, it is not known which transport protein in the basolateral membrane of proximal tubule cells is mediating the uptake of ADMA into the cells for subsequent degradation or the export of intracellularly synthesized L-homoarginine. One study suggested that the uptake transporter OATP4C1 (gene symbol SLCO4C1) may be involved in the transport of ADMA and other uremic toxins. OATP4C1 is a member of the SLCO/SLC21 family of solute carriers, localized in the basolateral membrane of human proximal tubule cells. By using stably-transfected HEK cells overexpressing human OATP4C1, we demonstrate that ADMA and L-homoarginine are substrates of OATP4C1 with Km values of 232.1 μM and 49.9 μM, respectively. ADMA and the structurally related uremic toxin SDMA (100 μM) inhibited OATP4C1-mediated L-homoarginine uptake (P < 0.01), whereas other tested uremic toxins such as urea and p-cresyl sulfate have no effect on OATP4C1-mediated transport. Preloading experiments (300 μM for 60 min) with subsequent efflux studies revealed that OATP4C1 also facilitates efflux e.g. of L-homoarginine. Both ADMA and L-homoarginine are substrates of human OATP4C1. Because proximal tubule cells are one site of ADMA metabolism and L-homoarginine synthesis, we postulate a protective role of OATP4C1 by mediating uptake of ADMA from and export of L-homoarginine into the systemic circulation. << Less

  PLoS ONE 14:e0213747-e0213747(2019) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Evidence for an arginine exporter encoded by yggA (argO) that is regulated by the LysR-type transcriptional regulator ArgP in Escherichia coli.

  Nandineni M.R., Gowrishankar J.

  The anonymous open reading frame yggA of Escherichia coli was identified in this study as a gene that is under the transcriptional control of argP (previously called iciA), which encodes a LysR-type transcriptional regulator protein. Strains with null mutations in either yggA or argP were supersen ... >> More

  The anonymous open reading frame yggA of Escherichia coli was identified in this study as a gene that is under the transcriptional control of argP (previously called iciA), which encodes a LysR-type transcriptional regulator protein. Strains with null mutations in either yggA or argP were supersensitive to the arginine analog canavanine, and yggA-lac expression in vivo exhibited argP(+)-dependent induction by arginine. Lysine supplementation phenocopied the argP null mutation in that it virtually abolished yggA expression, even in the argP+ strain. The dipeptides arginylalanine and lysylalanine behaved much like arginine and lysine, respectively, to induce and to turn off yggA transcription. Dominant missense mutations in argP (argPd) that conferred canavanine resistance and rendered yggA-lac expression constitutive were obtained. The protein deduced to be encoded by yggA shares similarity with a basic amino acid exporter (LysE) of Corynebacterium glutamicum, and we obtained evidence for increased arginine efflux from E. coli strains with either the argPd mutation or multicopy yggA+. The null yggA mutation abolished the increased arginine efflux from the argPd strain. Our results suggest that yggA encodes an ArgP-regulated arginine exporter, and we have accordingly renamed it argO (for "arginine outward transport"). We propose that the physiological function of argO may be either to prevent the accumulation to toxic levels of canavanine (which is a plant-derived antimetabolite) or arginine or to maintain an appropriate balance between the intracellular lysine and arginine concentrations. << Less

  J. Bacteriol. 186:3539-3546(2004) [PubMed] [EuropePMC]

• Human cationic amino acid transporters hCAT-1, hCAT-2A, and hCAT-2B: three related carriers with distinct transport properties.

  Closs E.I., Graef P., Habermeier A., Cunningham J.M., Foerstermann U.

  In this study, we aimed at analyzing the human homologues of the murine cationic amino acid transporters mCAT-1, mCAT-2A, and mCAT-2B. cDNAs encoding hCAT-1 had been previously reported by two independent groups [Albritton, L.M., et al. (1993) Genomics 12, 430; Yoshimoto, T., et al. (1991) Virolog ... >> More

  In this study, we aimed at analyzing the human homologues of the murine cationic amino acid transporters mCAT-1, mCAT-2A, and mCAT-2B. cDNAs encoding hCAT-1 had been previously reported by two independent groups [Albritton, L.M., et al. (1993) Genomics 12, 430; Yoshimoto, T., et al. (1991) Virology 185, 10]. We isolated cDNAs encoding hCAT-2A and hCAT-2B from a human liver cDNA library and from cDNA derived from the human hepatoma cell line HepG2, respectively. Analyses of the deduced amino acid sequences of both carriers demonstrated 90.9% identity with the respective murine proteins. In their functional domains (42 amino acids), both hCAT-2A and hCAT-2B differ only by one residue from the respective mouse proteins. Thus, CAT-2 proteins demonstrate a higher interspecies conservation than CAT-1 proteins that are overall 86.5% identical between mouse and human and differ by seven residues in the functional domain. The high degree of sequence conservation was reflected by the functional similarity of the human carriers with their mouse homologues. When expressed in Xenopus oocytes, hCAT-1 and hCAT-2B demonstrated transport properties consistent with y+. Unlike the mouse CAT-1 and CAT-2B, whose transport properties could hardly be distinguished, the transport properties of the human CAT-1 and CAT-2B isoforms showed clear differences: hCAT-1 had a 3-fold higher substrate affinity and was more sensitive to trans-stimulation than hCAT-2B. In contrast to the y+ carriers, hCAT-2A exhibited a 10-30-fold lower substrate affinity, a greater maximal velocity, and was much less sensitive to trans-stimulation at physiological substrate concentrations. << Less

  Biochemistry 36:6462-6468(1997) [PubMed] [EuropePMC]

• The human gene SLC25A29, of solute carrier family 25, encodes a mitochondrial transporter of basic amino acids.

  Porcelli V., Fiermonte G., Longo A., Palmieri F.

  The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport carboxylates, amino acids, nucleotides, and cofactors across the inner mitochondrial membrane, thereby connecting cytosolic and matr ... >> More

  The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport carboxylates, amino acids, nucleotides, and cofactors across the inner mitochondrial membrane, thereby connecting cytosolic and matrix functions. In this work, a member of this family, SLC25A29, previously reported to be a mitochondrial carnitine/acylcarnitine- or ornithine-like carrier, has been thoroughly characterized biochemically. The SLC25A29 gene was overexpressed in Escherichia coli, and the gene product was purified and reconstituted in phospholipid vesicles. Its transport properties and kinetic parameters demonstrate that SLC25A29 transports arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine. Carnitine and acylcarnitines were not transported by SLC25A29. This carrier catalyzed substantial uniport besides a counter-exchange transport, exhibited a high transport affinity for arginine and lysine, and was saturable and inhibited by mercurial compounds and other inhibitors of mitochondrial carriers to various degrees. The main physiological role of SLC25A29 is to import basic amino acids into mitochondria for mitochondrial protein synthesis and amino acid degradation. << Less

  J. Biol. Chem. 289:13374-13384(2014) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Control of cationic amino acid transport and retroviral receptor functions in a membrane protein family.

  Kavanaugh M.P., Wang H., Zhang Z., Zhang W., Wu Y.N., Dechant E., North R.A., Kabat D.

  A partial cDNA sequence indicated that the T lymphocyte early-activation gene (Tea) encodes a protein related to the dual-function ecotropic retrovirus receptor/cationic amino acid transporter (ecoR/CAT1), and RNA blots suggested highest Tea expression in T lymphocytes and liver (MacLeod, C.L., Fi ... >> More

  A partial cDNA sequence indicated that the T lymphocyte early-activation gene (Tea) encodes a protein related to the dual-function ecotropic retrovirus receptor/cationic amino acid transporter (ecoR/CAT1), and RNA blots suggested highest Tea expression in T lymphocytes and liver (MacLeod, C.L., Finley, K., Kakuda, D. Kozad, C.A., and Wilkinson, M.F. (1990) Mol. Cell. Biol. 7, 3663-3674). The sequence of full-length Tea cDNA from liver (3683 bases) predicts a 657-amino-acid protein (CAT2 alpha) with 12-14 transmembrane domains. A long (515 base) region with six initiation codons and termination codons precedes the translation start codon. The liver Tea cDNA is identical to Tea cDNA from T lymphocytes (encoding CAT2 beta) with the exception of an apparent alternatively spliced sequence encoding a hydrophilic loop of 43 amino acids. The liver-specific sequence contains unique consensus sites for phosphorylation by cyclic AMP-dependent protein kinase and by protein kinase C. Injection of Xenopus oocytes with CAT2 alpha or CAT2 beta messenger RNA resulted in expression of Na(+)-independent cationic amino acid transport that was detected by current measurements under voltage-clamp. Although the amino acid sequences of the isoforms differ in only 21 of 43 residues with the majority of substitutions being conservative, the apparent affinity of CAT2 beta for arginine uptake was 70-fold higher than the CAT2 alpha isoform (Km 38 microM versus 2.7 mM). Neither isoform functioned as a receptor for ecotropic or amphotropic murine retroviruses. However, CAT1-CAT2 chimeric proteins that contain the first three putative extracellular loops of ecoR/CAT1 functioned as ecotropic receptors despite a diminished capacity to bind the viral envelope glycoprotein. The chimeric proteins also functioned as basic amino acid transporters with substrate affinities corresponding to the CAT2 isoform constituting the carboxyl-terminal portion. These results demonstrate that domains of these transporters can function in chimeric combinations to control viral receptor and transport functions. << Less

  J. Biol. Chem. 269:15445-15450(1994) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.