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Michèle Reboud-Ravaux

Publications and source records attributed to Michèle Reboud-Ravaux.

11 recordsLinked to original sources
PubMed2006

Molecular tongs containing amino acid mimetic fragments: new inhibitors of wild-type and mutated HIV-1 protease dimerization.

We have designed, synthesized, and evaluated the inhibitory activity and metabolic stability of new peptidomimetic molecular tongs based on a naphthalene scaffold for inhibiting HIV-1 protease dimerization. Peptidomimetic motifs were inserted into one peptidic strand to make it resistant to proteolysis. The peptidic character of the molecular tongs can be decreased without changing the way they inhibit dimerization. Mutated HIV-1 proteases are also vulnerable to dimerization inhibitors, and the multimutated protease ANAM-11 is twice as sensitive to the inhibitor compared to wild-type protease. Thus, the metabolic stability of antidimeric molecular tongs can be increased without compromising their ability to inhibit wild-type and mutated HIV-1 proteases in vitro.

Amino Acids↗
PubMed2006

Development of lipopeptides for inhibiting 20S proteasomes.

Proteasomes are responsible for the cytoplasmic turnover of the vast majority of proteins including regulatory proteins. We have synthesized lipopeptides a new class of non-covalent inhibitors of the 20S proteasome and assayed their inhibitory capacities. Their ability to inhibit at micromolar concentrations chymotrypsin-like and post-acid activities depends on peptide length (3 or 6 amino acids), sequence (presence of a positively or negatively charged amino acid), and alkyl chain length (C6-C18). These structural features could be varied to selectively inhibit one or more of the three proteasome activities.

Amino Acid Sequence↗
PubMed2006

AZT and AZT-monophosphate prodrugs incorporating HIV-protease substrate fragment: synthesis and evaluation as specific drug delivery systems.

With the view to deliver anti-HIV nucleoside and nucleoside-monophosphate (MP) analogues specifically into HIV-infected cells, we synthesized a series of ester and phosphoramidate peptide conjugates of zidovudine (AZT) and of AZT-MP, respectively, wherein the peptide sequences derive from a HIV-protease (PR) hydrolysable substrate. Their in vitro stability with respect to hydrolysis, anti-HIV activity and cytotoxicity, and ability to inhibit the HIV-PR activity were investigated. Concerning the ester AZT-peptide conjugates, their antiviral activity level in thymidine kinase-expressing (TK+) CEM-SS and MT-4 cells was in most cases closely correlated to their hydrolysis rate: the faster the hydrolysis, the closer the anti-HIV activity to that of AZT. None of them was a HIV-PR substrate, indicating that their antiviral activity was not related to their intracellular hydrolysis by this enzyme. None of them inhibited HIV in TK-deficient (TK-) CEM cells, demonstrating that they probably act as prodrugs of AZT. Most of the phosphoramidate peptide conjugates of AZT-MP were rapidly degraded in a physiological buffer into several metabolites including AZT. Their anti-HIV activity in TK+ CEM-SS and MT-4 cells was much lower than that of AZT, indicating that only low amounts of AZT or AZT-MP were released into cells during incubation. Antiviral activities measured on TK- CEM cells for some phosphoramidates suggest that low amounts of AZT-MP could be released intracellularly. However, this AZT-MP release was not initiated by a HIV-PR hydrolysis, as no evidence for peptide cleavage was obtained by HPLC analysis of one representative compound after incubation with HIV-PR.

Amides↗
PubMed2004

New constrained "molecular tongs" designed to dissociate HIV-1 protease dimer.

New "molecular tongs" based on naphthalene and quinoline scaffolds linked to two peptidic strands were synthesized. They were designed to prevent dimerization of HIV-1 protease by targeting the antiparallel beta-sheet involving N- and C-termini of each monomer. Compared to "molecular tongs" previously described (Bouras, A.; Boggetto, N.; Benatalah, Z.; de Rosny, E.; Sicsic, S.; Reboux-Ravaud, M. J. Med. Chem. 1999, 42, 957-962), two main different structural features were introduced: positively charged quinoline as a new scaffold and two peptidic strands displaying different sequences. Seventeen new "molecular tongs" with dipeptidic or tripeptidic strands were synthesized. These molecules were assayed on HIV-1 protease using the Zhang kinetic technique. Eleven molecules behaved as pure dimerization inhibitors, mostly at the submicromolar range. Compared to a naphthalene scaffold, the quinoline one was shown in several cases to favor dimerization inhibition. The simplified hydrophobic Val-Leu-Val-OMe strand was confirmed as particularly favorable. The C-terminal analogue strand Thr-Leu-Asn-OMe was shown to be the best one for inducing dimerization inhibition (K(id) of 80 nM for compound 30). The mechanism of inhibition was ascertained using ANS binding and gel filtration. Experimental results are in agreement with the dissociation of the HIV-1 protease dimeric form in the presence of the synthesized molecular tongs.

Dimerization↗
PubMed2004

[Proteasome and proteolysis].

The maintenance of cellular homeostasis and the ability of cells to respond to their environment depend on the degradation of bulk proteins and orderly degradation of key regulatory proteins and their inhibitors. The 26S proteasome plays an essential role in these degradations. It is involved in the activation and inactivation of many cellular processes such as cell cycle progression, apoptosis and regulation of gene expression. It presents unique structural and functional properties. It degrades proteins by an unusual mechanism. Several series of proteasome inhibitors have been developed, useful to elucidate the biological roles of this multicatalytic enzyme. Velcade (bortezomid) was the first proteasome inhibitor to undergo, in may 2003, clinical trials in cancer patients.

Aging↗
PubMed2003

Dimerization inhibitors of HIV-1 protease based on a bicyclic guanidinium subunit.

Original inhibitors of HIV-1 protease based on a chiral bicyclic guanidinium scaffold linked to short peptidic mimics of the terminal protease sequences and to a lipophilic group were designed. These inhibitors prevent dimerization of the native protease by an interfacial structure at the highly conserved antiparallel beta-strand involving both the N and C termini that substantially account for dimerization. The preorganized guanidinium spacer introduces additional electrostatic hydrogen-bonding interactions with the C-terminal Phe-99 carboxylate. Lipophilic residues linked to side chains and the guanidinium scaffold are essential for dimerization inhibition as ascertained by Zhang kinetics (4, K(id) = 290 nM; 6 or 6', K(id) = 150 nM; 8, K(id) = 400 nM) combined with a circular dichroism study on the enzyme thermal stability. Remarkably, less hydrophobic compounds result in mixed dimerization (1a and 3) or active site inhibitors (5). Removal of the guanidinium hydrophobic groups leads to less active or inactive ligands.

Binding Sites↗
PubMed2003

Thyroxine-derivatives of lipopeptides: bifunctional dimerization inhibitors of human immunodeficiency virus-1 protease.

The structure of new lipopeptides targeting the enzymic dimer interface have been rationally improved resulting in dimerization inhibitors of the human immunodeficiency virus 1 protease (K(id)=5nM for the best inhibitor). The contribution of each amino acid in inhibitory 3-mer lipopeptides was analyzed demonstrating that the C-terminal amino acid residue may preferably be replaced by thyroxine and thyronine. The negative charge of Glu is not essential. Lengthening of the peptidic chain may lead to a decrease of efficiency and a change in the mechanism (competitive inhibition instead of dimerization inhibition). The N-terminal blocking group can be replaced by 2-aminopalmitic acid. The mechanism of inhibition has been ascertained using Zhang's kinetic analysis combined with a physical method based on binding of 1-anilino-8-naphtalene sulfonate to enzyme. By targeting the hydrophobic pocket and the interface antiparallel beta-sheet found relatively free of mutations in contrary to the active site, these efficient dimerization inhibitors may provide a way of overcoming the drug resistances observed with therapeutic antiproteases that bind to the active site.

Anilino Naphthalenesulfonates↗
PubMed2002

Regulation of the 26S proteasome activities by peptides mimicking cleavage products.

The implication of the released peptides in allosteric effects during protein degradation catalyzed by the proteasome is an important question not completely resolved. We present here data showing modulation of 26S proteasome activities by peptides composed of 5 or 6 natural amino acids that mimic the products generated during protein breakdown. Several of these peptides inhibit the chymotrypsin-like activity of the Xenope 26S proteasome whereas its trypsin-like activity is enhanced. The basic peptides produced competitive inhibition of the chymotrypsin-like activity and the acidic peptides, parabolic inhibition involving two different binding sites. Our results are in agreement with a model involving hypothetical non-catalytic sites interacting with effectors to modulate the peptidase activities of the proteasome. They also suggest that allosteric effects may occur in the proteasome during protein degradation.

Animals↗
PubMed2002

Metal-organic compounds: a new approach for drug discovery. N1-(4-methyl-2-pyridyl)-2,3,6-trimethoxybenzamide copper(II) complex as an inhibitor of human immunodeficiency virus 1 protease.

The use of metal-organic complexes is a potentially fruitful approach for the development of novel enzyme inhibitors. They hold the attractive promise of forming stronger attachments with the target by combining the co-ordination ability of metals with the unique stereoelectronic properties of the ligand. We demonstrated that this approach can be successfully used to inhibit the protease of the human immunodeficiency virus (type 1). Several ligands bearing substituents designed to interact with the catalytic site of the enzyme when complexed to Cu(2+) were synthesised. The inhibition pattern of the resulting copper(II) complexes was analysed. We showed that the copper(II) complex of N1-(4-methyl-2-pyridyl)-2,3,6-trimethoxybenzamide (C1) interacts with the active site of the enzyme leading to competitive inhibition. On the other hand, N2-pyridine-amide ligands and oxazinane carboxamide ligand were found to be poor chelators of the cupric ion under the enzymatic assay conditions. In these cases, the observed inhibition was attributed to released cupric ions which react with cysteine residues on the surface of the protease. While unchelated metal cations are not likely to be useful agents, metal chelates such as C1 should be considered as promising lead compounds for the development of targeted drugs.

Benzamides↗
PubMed2002

Dimerization inhibitors of HIV-1 protease.

By targeting the highly conserved antiparallel beta-sheet formed by the interdigitation of the N- and C-terminal strands of each monomer, dimerization inhibitors of HIV-1 protease may be useful to overcome the drug resistance observed with current active-site directed antiproteases. Sequestration of the monomer by the inhibitor (or disruption of the dimer interface) prevents the correct assembly of the inactive monomers to active enzyme. Strategies for the design of drugs targeting the dimer interface are described. Various dimerization inhibitors are reported including N- and C-terminal mimetics, lipopeptides and cross-linked interface peptides.

Dimerization↗