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Tomasi S, Renault J, Martin B, Duhieu S, Cerec V, Le Roch M, Uriac P, Delcros JG. Targeting the Polyamine Transport System with Benzazepine- and Azepine-Polyamine Conjugates. J Med Chem 2010; 53:7647-63. [DOI: 10.1021/jm1007648] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sophie Tomasi
- Produits Naturels−Synthèses−Chimie Médicinale, Sciences Chimiques de Rennes, CNRS UMR 6226, Faculté de Pharmacie, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Jacques Renault
- Produits Naturels−Synthèses−Chimie Médicinale, Sciences Chimiques de Rennes, CNRS UMR 6226, Faculté de Pharmacie, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Bénédicte Martin
- Groupe de Recherche en Thérapeutique Anticancéreuse, Faculté de Médecine, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Stephane Duhieu
- Groupe de Recherche en Thérapeutique Anticancéreuse, Faculté de Médecine, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Virginie Cerec
- Groupe de Recherche en Thérapeutique Anticancéreuse, Faculté de Médecine, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Myriam Le Roch
- Produits Naturels−Synthèses−Chimie Médicinale, Sciences Chimiques de Rennes, CNRS UMR 6226, Faculté de Pharmacie, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Philippe Uriac
- Produits Naturels−Synthèses−Chimie Médicinale, Sciences Chimiques de Rennes, CNRS UMR 6226, Faculté de Pharmacie, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
| | - Jean-Guy Delcros
- Groupe de Recherche en Thérapeutique Anticancéreuse, Faculté de Médecine, Université Rennes 1, Université Européenne de Bretagne, Rennes Cedex, France
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Kaur N, Delcros JG, Archer J, Weagraff NZ, Martin B, Phanstiel Iv O. Designing the polyamine pharmacophore: influence of N-substituents on the transport behavior of polyamine conjugates. J Med Chem 2008; 51:2551-60. [PMID: 18363351 DOI: 10.1021/jm701341k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N-Ethylated N-arylmethyl polyamine conjugates were synthesized and evaluated for their ability to target the polyamine transporter (PAT). To understand the effect of N-ethylation upon PAT selectivity, ethyl groups were appended onto a PAT-selective N (1)-anthracenenylmethyl homospermidine derivative, 1b. Bioevaluation in L1210 murine leukemia cells and in two Chinese hamster ovary cell lines (PAT-active CHO and PAT-deficient CHO-MG) revealed a dramatic decrease in PAT targeting ability upon N (1) or N (5) ethylation of the pharmacophore 1b. Experiments using the amine oxidase inhibitor, aminoguanidine (AG, 2 mM), revealed that the N (9)-ethyl and N (9)-methyl analogues were able to retain their PAT selectivity and cytotoxicity properties in the presence or absence of AG. In contrast, the lead compound 1b (containing a terminal NH 2 group) revealed a dramatic reduction in both its PAT-targeting ability and cytotoxicity in the absence of AG. An improved balance between these three properties of PAT-targeting, cytotoxicity and metabolic stability can be attained via N-methylation at the N (9)-position.
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Affiliation(s)
- Navneet Kaur
- Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France
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Kaur N, Delcros JG, Imran J, Khaled A, Chehtane M, Tschammer N, Martin B, Phanstiel O. A Comparison of Chloroambucil- and Xylene-Containing Polyamines Leads to Improved Ligands for Accessing the Polyamine Transport System. J Med Chem 2008; 51:1393-401. [DOI: 10.1021/jm070794t] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Navneet Kaur
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Jean-Guy Delcros
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Jon Imran
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Annette Khaled
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Mounir Chehtane
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Nuska Tschammer
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Bénédicte Martin
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
| | - Otto Phanstiel
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, Florida 32816-2366, Biomolecular Science Center, University of Central Florida, 12722 Research Parkway, Orlando, Florida 32825, Groupe Cycle Cellulaire, CNRS UMR 6061 Génétique et Développement, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, Université Rennes 1, 2 Av. du Pr Leon Bernard, CS 34317, F-35043 Rennes Cédex, France, and Department of Medical Education, College of Medicine, University of Central
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Delcros JG, Tomasi S, Duhieu S, Foucault M, Martin B, Le Roch M, Eifler-Lima V, Renault J, Uriac P. Effect of Polyamine Homologation on the Transport and Biological Properties of Heterocyclic Amidines. J Med Chem 2005; 49:232-45. [PMID: 16392808 DOI: 10.1021/jm050018q] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Five sets of heterocyclic derivatives of various sizes and complexities coupled by an amidine function to putrescine, spermidine, or spermine were prepared. They were essentially tested to determine the influence of the polyamine chain on their cellular transport. To comment on affinity and on selective transport via the polyamine transport system (PTS), K(i) values for polyamine uptake were determined in L1210 cells, and the cytotoxicity and accumulation of the conjugates were determined in CHO and polyamine transport-deficient mutant CHO-MG cells, as well as in L1210 and alpha-difluoromethylornithine- (DFMO-) treated L1210 cells. Unlike spermine, putrescine and spermidine were clearly identified as selective motifs that enable cellular entry via the PTS. However, this property was clearly limited by the size of substituents: these polyamines were able to ferry a dihydroquinoline system via the PTS but did not impart any selectivity to bulkier substituents.
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Affiliation(s)
- Jean-Guy Delcros
- Groupe de Recherche en Thérapeutique Anticancéreuse, Faculté de Médecine, Université Rennes 1, 2 Avenue du Professeur Léon Bernard, 35043 Rennes Cedex, France.
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5
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Kaur N, Delcros JG, Martin B, Phanstiel O. Synthesis and Biological Evaluation of Dihydromotuporamine Derivatives in Cells Containing Active Polyamine Transporters. J Med Chem 2005; 48:3832-9. [PMID: 15916435 DOI: 10.1021/jm0491288] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dihydromotuporamine C (4) and its 4,4-triamine analogue (5) were synthesized in good yield using ring-closing metathesis (RCM) methods. Comparison of their biological activities (Ki determinations in L1210 cells and IC50 determinations in L1210, CHO, and CHO-MG cells) revealed that the motuporamine derivatives do not use the polyamine transporter (PAT) for cellular entry. Bioevaluation of a N1-(anthracen-9-ylmethyl)-N1-(ethyl)homospermidine control (7) revealed that the presence of a N1 tertiary amine center imparted a significant reduction in the PAT affinity of the polyamine conjugate and abolished its PAT-targeting selectivity.
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Affiliation(s)
- Navneet Kaur
- Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 32816-2366, USA
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Gardner RA, Delcros JG, Konate F, Breitbeil F, Martin B, Sigman M, Huang M, Phanstiel O. N1-substituent effects in the selective delivery of polyamine conjugates into cells containing active polyamine transporters. J Med Chem 2005; 47:6055-69. [PMID: 15537360 DOI: 10.1021/jm0497040] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Several N(1)-arylalkylpolyamines containing various aromatic ring systems were synthesized as their respective HCl salts. The N(1)-substituents evaluated ranged in size from N(1)-benzyl, N(1)-naphthalen-1-ylmethyl, N(1)-2-(naphthalen-1-yl)ethyl, N(1)-3-(naphthalen-1-yl)propyl, N(1)-anthracen-9-ylmethyl, N(1)-2-(anthracen-9-yl)ethyl, N(1)-3-(anthracen-9-yl)propyl, and pyren-1-ylmethyl. The polyamine architecture was also altered and ranged from diamine to triamine and tetraamine systems. Biological activities in L1210 (murine leukemia), Chinese hamster ovary (CHO), and CHO's polyamine transport-deficient mutant (CHO-MG) cell lines were investigated via IC(50) cytotoxicity determinations. K(i) values for spermidine uptake were also determined in L1210 cells. The size of the N(1)-arylalkyl substituent as well as the polyamine sequence used had direct bearing on the observed cytotoxicity profiles. N(1)-Tethers longer than ethylene showed dramatic loss of selectivity for the polyamine transporter (PAT) as shown in a CHO/CHO-MG cytotoxicity screen. In summary, there are clear limits to the size of N(1)-substituents, which can be accommodated by the polyamine transporter. A direct correlation was observed between polyamine-conjugate uptake and cytotoxicity. In this regard, a cytotoxicity model was proposed, which describes a hydrophobic pocket of set dimensions adjacent to the putative PAT polyamine-binding site.
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Affiliation(s)
- Richard Andrew Gardner
- Department of Chemistry, P.O. Box 162366, University of Central Florida, Orlando, FL 32816-2366, USA
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7
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Wang C, Delcros JG, Cannon L, Konate F, Carias H, Biggerstaff J, Gardner RA, Phanstiel IV O. Defining the Molecular Requirements for the Selective Delivery of Polyamine Conjugates into Cells Containing Active Polyamine Transporters. J Med Chem 2003; 46:5129-38. [PMID: 14613316 DOI: 10.1021/jm030223a] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Several N(1)-substituted polyamines containing various spacer units between nitrogen centers were synthesized as their respective HCl salts. The N(1)-substituents included benzyl, naphthalen-1-ylmethyl, anthracen-9-ylmethyl, and pyren-1-ylmethyl. The polyamine spacer units ranged from generic (4,4-triamine, 4,3-triamine, and diaminooctane) spacers to more exotic [2-(ethoxy)ethanoxy-containing diamine, hydroxylated 4,3-triamine, and cyclohexylene-containing triamine] spacers. Two control compounds were also evaluated: N-(anthracen-9-ylmethyl)-butylamine and N-(anthracen-9-ylmethyl)-butanediamine. Biological activities in L1210 (murine leukemia), alpha-difluoromethylornithine (DFMO)-treated L1210, and Chinese hamster ovary (CHO) and its polyamine transport-deficient mutant (CHO-MG) cell lines were investigated via IC(50) cytotoxicity determinations. K(i) values for spermidine uptake were also determined in L1210 cells. Of the series studied, the N(1)-benzyl-4,4-triamine system 6 had significantly higher IC(50) values (lower cytotoxicity) in the L1210, CHO, and CHO-MG cell lines. A cellular debenzylation process was observed in L1210 cells with 6 and generated "free" homospermidine. The size of the N(1)-arylmethyl substituent had direct bearing on the observed cytotoxicity in CHO-MG cells. The N(1)-naphthalenylmethyl, N(1)-anthracenylmethyl, and N(1)-pyrenylmethyl 4,4-triamines had similar toxicity (IC(50)s: approximately 0.5 microM) in CHO cells, which have an active polyamine transporter (PAT). However, this series had IC(50) values of >100 microM, 66.7 microM, and 15.5 microM, respectively, in CHO-MG cells, which are PAT-deficient. The observed lower cytotoxicity in the PAT-deficient CHO-MG cell line supported the premise that the conjugates use PAT for cellular entry. In general, moderate affinities for the polyamine transporter were observed for the N-arylmethyl 4,4-triamine series with their L1210 K(i) values all near 3 microM. In summary, the 4,4-triamine motif was shown to facilitate entry of polyamine conjugates into cells containing active polyamine transporters.
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Affiliation(s)
- Chaojie Wang
- Groupe de Recherche en Therapeutique Anticancéreuse, Faculté de Médecine, 2, Avenue du Professeur Léon Bernard, University of Rennes 1, 35043 Rennes, France
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8
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Wang C, Delcros JG, Biggerstaff J, Phanstiel O. Synthesis and biological evaluation of N1-(anthracen-9-ylmethyl)triamines as molecular recognition elements for the polyamine transporter. J Med Chem 2003; 46:2663-71. [PMID: 12801230 DOI: 10.1021/jm030028w] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An efficient modular synthesis of N(1)-substituted triamines containing different tether lengths between nitrogen centers was developed. A series of N(1)-(9-anthracenylmethyl)triamines were evaluated for biological activity in L1210 (murine leukemia), alpha-difluoromethylornithine (DFMO)-treated L1210, Chinese hamster ovary (CHO), and CHO-MG cell lines. All triamines 8 had increased potency in DFMO-treated L1210 cells. The 4,4- and 5,4-triamine systems had the highest affinity for the polyamine transporter (PAT) with L1210 K(i) values of 1.8 and 1.7 microM, respectively. This trend was also reflected in the CHO studies. Surprisingly, the respective 4,4- and 5,4-triamine systems had 150-fold and 38-fold higher cytotoxicity in CHO cells containing active polyamine transporters. Initial microscopy studies revealed the rapid formation of vesicular structures within A375 melanoma cells treated with the N(1)-(9-anthracenylmethyl)homospermidine (4,4-triamine) conjugate. In summary, the 4,4- and 5,4-triamines were identified as selective vector motifs to ferry anthracene into cells via the PAT.
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Affiliation(s)
- Chaojie Wang
- Groupe de Recherche en Therapeutique Anticancéreuse, Faculté de Médecine, 2, Avenue du Professeur Léon Bernard, 35043 Rennes, France
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9
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Wang C, Delcros JG, Biggerstaff J, Phanstiel O. Molecular requirements for targeting the polyamine transport system. Synthesis and biological evaluation of polyamine-anthracene conjugates. J Med Chem 2003; 46:2672-82. [PMID: 12801231 DOI: 10.1021/jm020598g] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of nine N(1)-(9-anthracenylmethyl)tetraamines (e.g., Ant-4,4,4-tetraamine) were synthesized and evaluated for cytotoxicity in L1210, alpha-difluoromethylornithine (DFMO)-treated L1210, Chinese hamster ovary (CHO), and CHO-MG cell lines. Surprisingly, the 3,3,4- and 3,4,3-tetraamine motifs had the same or decreased cytotoxicity in DFMO-treated L1210 cells, whereas the rest of the tetraamine systems were usually more cytotoxic and gave lower IC(50) values in this treated cell line. The most sensitive derivatives to DFMO treatment were the Ant-4,4,3- and Ant-4,4,4-tetraamine analogues, which were 7 and 5 times more cytotoxic in DFMO-treated L1210 cells, respectively. K(i) values for each of the anthracenylmethyl(Ant)-polyamine conjugates were determined in L1210 cells and revealed that these systems are high-affinity ligands for the polyamine transporter (PAT). Mixed results were observed in the CHO and CHO-MG assays. The 4,4,4- and 5,4,4-tetraamine motifs were 3 times more toxic to CHO cells with active polyamine transporters. For example, the Ant-4,4,4-tetraamine conjugate displayed IC(50) values of 11 microM in CHO cells and 33 microM in CHO-MG cells, a PAT-deficient cell line. This suggested that these derivatives used the PAT in part to access cells. However, most of the other tetraamine derivatives had similar potencies in both the CHO and CHO-MG cell lines. In terms of vector design, higher affinity for the PAT (lower K(i) values) did not translate into higher potency for the tetraamine conjugate. In contrast, the related triamine systems, which had micromolar K(i) values in L1210 cells, were more efficacious and selective. In one case, the 4,4-triamine motif imparted 150-fold higher potency in CHO cells than the CHO-MG mutant. A deconvolution microscopy study in A375 melanoma cells revealed a rapid internalization of the Ant-4,4-triamine as fluorescent vesicles, whereas the Ant-4,4,4-tetraamine remained mostly at the cell surface. These findings help define the key characteristics required for selective delivery of polyamine-drug conjugates into cell types with active polyamine transporters.
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Affiliation(s)
- Chaojie Wang
- Groupe de Recherche en Therapeutique Anticancéreuse, Faculté de Médecine, 2, Avenue du Professeur Léon Bernard, 35043 Rennes, France
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McNemar MD, Gorman JA, Buckley HR. Isolation of a gene encoding a putative polyamine transporter from Candida albicans, GPT1. Yeast 2001; 18:555-61. [PMID: 11284011 DOI: 10.1002/yea.697] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A gene encoding a transport protein from the pathogenic yeast, Candida albicans, has been isolated during a complementation experiment utilizing an ornithine decarboxylase-negative (spe1 Delta) strain of Saccharomyces cerevisiae. This gene restores gamma-aminobutyric acid (GABA) transport to a GABA transport-negative mutant of S. cerevisiae and encodes a protein which putatively allows transport of one or more of the polyamines. We have assigned the name GPT1 (GABA/polyamine transporter) to this gene.
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Affiliation(s)
- M D McNemar
- Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, PA 19140, USA
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11
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Poulin R, Zhao C, Verma S, Charest-Gaudreault R, Audette M. Dependence of mammalian putrescine and spermidine transport on plasma-membrane potential: identification of an amiloride binding site on the putrescine carrier. Biochem J 1998; 330 ( Pt 3):1283-91. [PMID: 9494098 PMCID: PMC1219274 DOI: 10.1042/bj3301283] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The mechanism of mammalian polyamine transport is poorly understood. We have investigated the role of plasma-membrane potential (DeltaPsipm) in putrescine and spermidine uptake in ZR-75-1 human breast cancer cells. The rate of [3H]putrescine and [3H]spermidine uptake was inversely correlated to extracellular [K+] ([K+]o) and to DeltaPsipm, as determined by the accumulation of [3H]tetraphenylphosphonium bromide (TPP). Inward transport was unaffected by a selective decrease in mitochondrial potential (DeltaPsimit) induced by valinomycin at low [K+]o, but was reduced by approximately 60% by the rheogenic protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP), which rapidly (<=15 min) collapsed both DeltaPsipm and DeltaPsimit. Plasma-membrane depolarization by high [K+]o or CCCP did not enhance putrescine efflux in cells pre-loaded with [3H]putrescine, suggesting that decreased uptake caused by these agents did not result from a higher excretion rate. On the other hand, the electroneutral K+/H+ exchanger nigericin (10 microM) co-operatively depressed -3H-TPP, [3H]putrescine and [3H]spermidine uptake in the presence of ouabain. Suppression of putrescine uptake by nigericin+ouabain was Na+-dependent, suggesting that plasma-membrane repolarization by the electrogenic Na+ pump was required upon acidification induced by nigericin, due to the activation of the Na+/H+ antiporter. The sole addition of 5-N, N-hexamethylene amiloride, a potent inhibitor of the Na+/H+ antiporter, strongly inhibited putrescine uptake in a competitive fashion -Ki 4.0+/-0.9 (S.D.) microM-, while being a weaker antagonist of spermidine uptake. The potency of a series of amiloride analogues to inhibit putrescine uptake was clearly different from that of the Na+/H+ antiporter, and resembled that noted for Na+ co-transport proteins. These data demonstrate that putrescine and spermidine influx is mainly unidirectional and strictly depends on DeltaPsipm, but not DeltaPsimit. This report also provides first evidence for a high-affinity amiloride-binding site on the putrescine carrier, which provides new insight into the biochemical properties of this transporter.
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Affiliation(s)
- R Poulin
- Laboratory of Molecular Endocrinology, Laval University Medical Research Centre, 2705 Laurier Blvd., Ste.Foy, Quebec, Canada G1V4G2
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12
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Abstract
The uptake and release of the natural polyamines putrescine, spermidine and spermine by mammalian cells are integral parts of the systems that regulate the intracellular concentrations of these biogenic amines according to needs. Although a general feature of all tissues, polyamine uptake into intestinal mucosa cells is perhaps the most obvious polyamine transport pathway of physiological and pathophysiological importance. Mutant cell lines lacking the ability to take up polyamines from the environment are capable of releasing polyamines. This indicates that uptake and release are functions of two different transport systems. The isolation of a transporter gene from a mammalian cell line is still lacking. Overaccumulation of polyamines is controlled by release and by a feedback regulation system that involves de novo synthesis of antizyme, a well known protein that also regulates the activity of ornithine decarboxylase. Recent work has demonstrated that Ca(2+)-signalling pathways are also involved. Although there is consensus about the importance of polyamine uptake inhibitors in the treatment of neoplastic disorders, a practically useful uptake inhibitor is still missing. However, the attempts to target tumours, and to increase the selectivity of cytotoxic agents by combining them with the polyamine structure, are promising. New, less toxic and more selective anticancer drugs can be expected from this approach.
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Affiliation(s)
- N Seiler
- Groupe de Recherche en Thérapeutique Anticancéreuse, URA CNRS 1529 affiliée INSERM, Institut de Recherche Contre le Cancer, Faculté de Médecine, Université de Rennes I, France
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