- Identification of 8-aminoadenosine derivatives as a new class of human concentrative nucleoside transporter 2 inhibitors
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Purine-rich foods have long been suspected as a major cause of hyperuricemia. We hypothesized that inhibition of human concentrative nucleoside transporter 2 (hCNT2) would suppress increases in serum urate levels derived from dietary purines. To test this hypothesis, the development of potent hCNT2 inhibitors was required. By modifying adenosine, an hCNT2 substrate, we successfully identified 8-aminoadenosine derivatives as a new class of hCNT2 inhibitors. Compound 12 moderately inhibited hCNT2 (IC50 = 52 ± 3.8 μM), and subsequent structure-activity relationship studies led to the discovery of compound 48 (IC50 = 0.64 ± 0.19 μM). Here we describe significant findings about structural requirements of 8-aminoadenosine derivatives for exhibiting potent hCNT2 inhibitory activity.
- Tatani, Kazuya,Hiratochi, Masahiro,Nonaka, Yoshinori,Isaji, Masayuki,Shuto, Satoshi
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supporting information
p. 244 - 248
(2015/03/30)
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- The nucleoside transport proteins, NupC and NupG, from Escherichia coli: Specific structural motifs necessary for the binding of ligands
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A series of 46 natural nucleosides and analogues (mainly adenosine-based) were tested as inhibitors of [U-14C]uridine uptake by the concentrative, H+-linked nucleoside transport proteins NupC and NupG from Escherichia coli. The two evolutionarily unrelated transporters showed similar but distinct patterns of inhibition, revealing differing selectivities for the different nucleosides and their analogues. Binding of nucleosides to NupG required the presence of hydroxyl groups at each of the C-3′ and C-5′ positions of ribose, while binding to NupC required only the C-3′ hydroxyl substituent. The greater importance of the ribose moiety for binding to NupG is consistent with the evolutionary relationship between this protein and the oligosaccharide: H+ symporter (OHS) subfamily of the major facilitator superfamily (MFS) of transporters. For both proteins the natural α-configuration at C-3′ and the natural β-configuration at C-1′ was mandatory for ligand binding. N-7 in the imidazole ring of adenosine and the amino group at C-6 were found not to be important for binding and both transporters showed flexibility for substitution at C-6/N6; one or both of N-l and N-3 were important for adenosine analogue binding to NupC but significantly less so for binding to NupG. From the different effects of 8-bromoadenosine on the two transporters it appears that adenosine selectively binds to NupC in an anti- rather than a syn-conformation, whereas NupG is less prescriptive. The pattern of inhibition of NupC by differing nucleoside analogues confirmed the functional relationship of the bacterial transporter to members of the human concentrative nucleoside transporter (CNT) family and reaffirmed the use of the bacterial protein as an experimental model for these physiologically and clinically important mammalian proteins. The specificity data for NupG have been used to develop a homology model of the protein's binding site, based on the X-ray crystallographic structure of the disaccharide transporter LacY from E. coli. We have also developed an efficient general protocol for the synthesis of adenosine and three of its analogues, which is illustrated by the synthesis of [1′-13C]adenosine.
- Patching, Simon G.,Baldwin, Stephen A.,Baldwin, Alexander D.,Young, James D.,Gallagher, Maurice P.,Henderson, Peter J. F.,Herbert, Richard B.
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p. 462 - 470
(2007/10/03)
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- Adenosine analogues as inhibitors of Trypanosoma brucei phosphoglycerate kinase: Elucidation of a novel binding mode for a 2-Amino-N6-substituted adenosine
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As part of a project aimed at structure-based design of adenosine analogues as drugs against African trypanosomiasis, N6-, 2-amino-N6-, and N2-substituted adenosine analogues were synthesized and tested to establish structure - activity relationships for inhibiting Trypanosoma brucei glycosomal phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and glycerol-3-phosphate dehydrogenase (GPDH). Evaluation of X-ray structures of parasite PGK, GAPDH, and GPDH complexed with their adenosyl-bearing substrates led us to generate a series of adenosine analogues which would target all three enzymes simultaneously. There was a modest preference by PGK for N6-substituted analogues bearing the 2-amino group. The best compound in this series, 2-amino-N6-[2-(p-hydroxyphenyl)ethyl]adenosine (46b), displayed a 23-fold improvement over adenosine with an IC50 of 130 μM. 2-[[2-(p-Hydroxyphenyl)ethyl]amino]adenosine (46c) was a weak inhibitor of T. brucei PGK with an IC50 of 500 μM. To explore the potential of an additive effect that having the N6 and N2 substitutions in one molecule might provide, the best ligands from the two series were incorporated into N6,N2-disubstituted adenosine analogues to yield N6-(2-phenylethyl)-2-[(2-phenylethyl)amino]adenosine (69) as a 30 μM inhibitor of T. brucei PGK which is 100-fold more potent than the adenosine template. In contrast, these series gave no compounds that inhibited parasitic GAPDH or GPDH more than 10-20% when tested at 1.0 mM. A 3.0 A? X-ray structure of a T. brucei PGK/46b complex revealed a binding mode in which the nucleoside analogue was flipped and the ribosyl moiety adopted a syn conformation as compared with the previously determined binding mode of ADP. Molecular docking experiments using QXP and SAS program suites reproduced this 'flipped and rotated' binding mode.
- Bressi,Choe,HoughHough,Buckner,Van Voorhis,Verlinde,Hol,Gelb
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p. 4135 - 4150
(2007/10/03)
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- Selective tight binding inhibitors of trypanosomal glyceraldehyde-3- phosphate dehydrogenase via structure-based drug design
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Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the sleeping sickness parasite Trypanosoma brucei is a rational target for anti- trypanosomatid drug design because glycolysis provides virtually all of the energy for the bloodstream form of this parasite. Glycolysis is also an important source of energy for other pathogenic parasites including Trypanosoma cruzi and Leishmania mexicana. The current study is a continuation of our efforts to use the X-ray structures of T. brucei and L. mexicana GAPDHs containing bound NAD+ to design adenosine analogues that bind tightly to the enzyme pocket that accommodates the adenosyl moiety of NAD+. The goal was to improve the affinity, selectivity, and solubility of previously reported 2'-deoxy-2'-(3-methoxybenzamido)adenosine (1). It was found that introduction of hydroxyl functions on the benzamido ring increases solubility without significantly affecting enzyme inhibition. Modifications at the previously unexploited N6-position of the purine not only lead to a substantial increase in inhibitor potency but are also compatible with the 2'-benzamido moiety of the sugar. For N6-substituted adenosines, two successive rounds of modeling and screening provided a 330-fold gain in affinity versus that of adenosine. The combination of N6- and 2'- substitutions produced significantly improved inhibitors. N6-Benzyl (9a) and N6-2-methylbenzyl (9b) derivatives of 1 display IC50 values against L. mexicana GAPDH of 16 and 4 μM, respectively (3100- and 12500-fold more potent than adenosine). The adenosine analogues did not inhibit human GAPDH. These studies underscore the usefulness of structure-based drug design for generating potent and species-selective enzyme inhibitors of medicinal importance starting from a weakly binding lead compound.
- Aronov, Alex M.,Verlinde, Christophe L. M. J.,Hol, Wim G. J.,Gelb, Michael H.
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p. 4790 - 4799
(2007/10/03)
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