Publications by authors named "Rafael Claveria-Gimeno"

16 Publications

  • Page 1 of 1

In Vitro Antiviral Activity of Tyrosinase from Mushroom against Hepatitis C Virus.

Pharmaceuticals (Basel) 2021 Aug 3;14(8). Epub 2021 Aug 3.

Department of Biocatalysis, Institute of Catalysis (CSIC), c/Marie Curie 2, Cantoblanco Campus UAM, 28049 Madrid, Spain.

Tyrosinases from a commercial protein extract and directly isolated from white mushrooms were purified in order to obtaining the well-known tyrosinase from () of 45 kDa and a newly discovered 50 kDa tyrosinase isoform (), and tested showing high antiviral activity against the hepatitis C virus for the first time. Cell toxicity and antiviral activity of tyrosinases were determined in cultured Huh 5-2 liver tumor cells transfected with a replicon system (a plasmid that includes all non-structural hepatitis C virus proteins and replicates autonomously). was able to inhibit the replication of the hepatitis C virus without inducing toxicity in liver cells. In addition, the post-translational isoform showed higher antiviral capacity than the former (up to 10 times greater), also exhibiting 10 times higher activity than the commercial drug Ribavirin. This antiviral activity was directly proportional to the enzymatic activity of tyrosinases, as no antiviral capacity was observed in the inactive form of the enzymes. The tyrosinases approach could represent a new antiviral inhibition mechanism, through a plausible catalytic mechanism of selective hydroxylation of the key role of tyrosine residues in viral proteases.
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http://dx.doi.org/10.3390/ph14080759DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399381PMC
August 2021

Stabilization Effect of Intrinsically Disordered Regions on Multidomain Proteins: The Case of the Methyl-CpG Protein 2, MeCP2.

Biomolecules 2021 08 16;11(8). Epub 2021 Aug 16.

Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, 50018 Zaragoza, Spain.

Intrinsic disorder plays an important functional role in proteins. Disordered regions are linked to posttranslational modifications, conformational switching, extra/intracellular trafficking, and allosteric control, among other phenomena. Disorder provides proteins with enhanced plasticity, resulting in a dynamic protein conformational/functional landscape, with well-structured and disordered regions displaying reciprocal, interdependent features. Although lacking well-defined conformation, disordered regions may affect the intrinsic stability and functional properties of ordered regions. MeCP2, methyl-CpG binding protein 2, is a multifunctional transcriptional regulator associated with neuronal development and maturation. MeCP2 multidomain structure makes it a prototype for multidomain, multifunctional, intrinsically disordered proteins (IDP). The methyl-binding domain (MBD) is one of the key domains in MeCP2, responsible for DNA recognition. It has been reported previously that the two disordered domains flanking MBD, the N-terminal domain (NTD) and the intervening domain (ID), increase the intrinsic stability of MBD against thermal denaturation. In order to prove unequivocally this stabilization effect, ruling out any artifactual result from monitoring the unfolding MBD with a local fluorescence probe (the single tryptophan in MBD) or from driving the protein unfolding by temperature, we have studied the MBD stability by differential scanning calorimetry (reporting on the global unfolding process) and chemical denaturation (altering intramolecular interactions by a different mechanism compared to thermal denaturation).
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http://dx.doi.org/10.3390/biom11081216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8391517PMC
August 2021

A multi-laboratory benchmark study of isothermal titration calorimetry (ITC) using Ca and Mg binding to EDTA.

Eur Biophys J 2021 May 16;50(3-4):429-451. Epub 2021 Apr 16.

CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Porto, Portugal.

A small-scale ITC benchmarking study was performed involving 9 biophysics laboratories/facilities, to evaluate inter-laboratory and intra-laboratory basal levels of uncertainty. Our prime goal was to assess a number of important factors that can influence both the data gathered by this technique and the thermodynamic parameter values derived therefrom. In its first part, the study involved 5 laboratories and 13 different instruments, working with centrally prepared samples and the same experimental protocol. The second part involved 4 additional laboratories and 6 more instruments, where the users prepared their own samples according to provided instructions and did the experiments following the same protocol as in the first part. The study design comprised: (1) selecting a minimal set of laboratories; (2) providing very stable samples; (3) providing samples not requiring preparation or manipulation; and (4) providing a well-defined and detailed experimental protocol. Thus, we were able to assess: (i) the variability due to instrument and data analysis performed by each user on centrally prepared samples; (ii) the comparability of data retrieved when using 4 different software packages to analyze the same data, besides the data analysis carried out by the different users on their own experimental results; and (iii) the variability due to local sample preparation (second part of the study). Individual values, as well as averages and standard deviations for the binding parameters for EDTA-cation interaction, were used as metrics for comparing the equilibrium association constant (logK), enthalpy of interaction (ΔH), and the so-called "stoichiometry" (n), a concentration-correction factor.
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http://dx.doi.org/10.1007/s00249-021-01523-7DOI Listing
May 2021

Influence of the disordered domain structure of MeCP2 on its structural stability and dsDNA interaction.

Int J Biol Macromol 2021 Apr 3;175:58-66. Epub 2021 Feb 3.

Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, Zaragoza 50018, Spain; Instituto de Investigación Sanitaria Aragón (IIS Aragón), 50009 Zaragoza, Spain; Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (CIBERehd), 28029 Madrid, Spain; Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009 Zaragoza, Spain; Fundación ARAID, Gobierno de Aragón, 50018 Zaragoza, Spain. Electronic address:

Methyl-CpG binding protein 2 (MeCP2) is a transcriptional regulator and a chromatin-associated structural protein. MeCP2 deregulation results in two neurodevelopmental disorders: MeCP2 dysfunction is associated with Rett syndrome, while excess of activity is associated with MeCP2 duplication syndrome. MeCP2 is an intrinsically disordered protein (IDP) constituted by six structural domains with variable, small percentage of well-defined secondary structure. Two domains, methyl-CpG binding domain (MBD) and transcription repressor domain (TRD), are the elements responsible for dsDNA binding ability and recruitment of the gene transcription/silencing machinery, respectively. Previously we studied the influence of the completely disordered, MBD-flanking domains (N-terminal domain, NTD, and intervening domain, ID) on the structural and functional features of the MBD (Claveria-Gimeno, R. et al. Sci Rep. 2017, 7, 41,635). Here we report the biophysical study of the influence of the remaining domains (transcriptional repressor domain, TRD, and C-terminal domains, CTDα and CTDβ) on the structural stability of MBD and the dsDNA binding capabilities of MBD and ID. The influence of distant disordered domains on MBD properties makes it necessary to consider the NTD-MBD-ID variant as the minimal protein construct for studying dsDNA/chromatin binding properties, while the full-length protein should be considered for transcriptional regulation studies.
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http://dx.doi.org/10.1016/j.ijbiomac.2021.01.206DOI Listing
April 2021

Molecular Context-Dependent Effects Induced by Rett Syndrome-Associated Mutations in MeCP2.

Biomolecules 2020 11 10;10(11). Epub 2020 Nov 10.

Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, 50018 Zaragoza, Spain.

Methyl-CpG binding protein 2 (MeCP2) is a transcriptional regulator and a chromatin-binding protein involved in neuronal development and maturation. Loss-of-function mutations in MeCP2 result in Rett syndrome (RTT), a neurodevelopmental disorder that is the main cause of mental retardation in females. MeCP2 is an intrinsically disordered protein (IDP) constituted by six domains. Two domains are the main responsible elements for DNA binding (methyl-CpG binding domain, MBD) and recruitment of gene transcription/silencing machinery (transcription repressor domain, TRD). These two domains concentrate most of the RTT-associated mutations. R106W and R133C are associated with severe and mild RTT phenotype, respectively. We have performed a comprehensive characterization of the structural and functional impact of these substitutions at molecular level. Because we have previously shown that the MBD-flanking disordered domains (N-terminal domain, NTD, and intervening domain, ID) exert a considerable influence on the structural and functional features of the MBD (Claveria-Gimeno, R. et al. Sci Rep. , , 41635), here we report the biophysical study of the influence of the protein scaffold on the structural and functional effect induced by these two RTT-associated mutations. These results represent an example of how a given mutation may show different effects (sometimes opposing effects) depending on the molecular context.
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http://dx.doi.org/10.3390/biom10111533DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7696773PMC
November 2020

Janus Dendrimers to Assess the Anti-HCV Activity of Molecules in Cell-Assays.

Pharmaceutics 2020 Nov 7;12(11). Epub 2020 Nov 7.

Instituto de Nanociencia y Materiales de Aragón (INMA), University of Zaragoza-CSIC, Pedro Cerbuna 12, 50009 Zaragoza, Spain.

The use of nanocarriers has been revealed as a valid strategy to facilitate drug bioavailability, and this allows for expanding the drug libraries for the treatment of certain diseases such as viral diseases. In the case of Hepatitis C, the compounds iopanoic acid and 3,3',5-triiodothyroacetic acid (or tiratricol) were identified in a primary screening as bioactive allosteric inhibitors of viral NS3 protease, but they did not exhibit accurate activity inhibiting viral replication in cell-based assays. In this work, dendritic nanocarriers are proposed due to their unique properties as drug delivery systems to rescue the bioactivity of these two drugs. Specifically, four different amphiphilic Janus dendrimers synthesized by combining 2,2'-(hydroxymethyl)propionic acid (-MPA) and 2,2'-(glyciloxy)propionic acid (-GMPA) functionalized with either hydrophilic or lipophilic moieties at their periphery were used to entrap iopanoic acid and tiratricol. Interestingly, differences were found in the loading efficiencies depending on the dendrimer design, which also led to morphological changes of the resulting dendrimer aggregates. The most remarkable results consist of the increased water solubility of the bioactive compounds within the dendrimers and the improved antiviral activity of some of the dendrimer/drug aggregates, considerably improving antiviral activity in comparison to the free drugs. Moreover, imaging studies have been developed in order to elucidate the mechanism of cellular internalization.
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http://dx.doi.org/10.3390/pharmaceutics12111062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695217PMC
November 2020

MeCP2-E1 isoform is a dynamically expressed, weakly DNA-bound protein with different protein and DNA interactions compared to MeCP2-E2.

Epigenetics Chromatin 2019 10 10;12(1):63. Epub 2019 Oct 10.

Department of Biochemistry and Microbiology, University of Victoria, Petch Building 260, Victoria, BC, V8W 3P6, Canada.

Background: MeCP2-a chromatin-binding protein associated with Rett syndrome-has two main isoforms, MeCP2-E1 and MeCP2-E2, differing in a few N-terminal amino acid residues. Previous studies have shown brain region-specific expression of these isoforms which, in addition to their different cellular localization and differential expression during brain development, suggest that they may also have non-overlapping molecular mechanisms. However, differential functions of MeCP2-E1 and E2 remain largely unexplored.

Results: Here, we show that the N-terminal domains (NTD) of MeCP2-E1 and E2 modulate the ability of the methyl-binding domain (MBD) to interact with DNA as well as influencing the turn-over rates, binding dynamics, response to neuronal depolarization, and circadian oscillations of the two isoforms. Our proteomics data indicate that both isoforms exhibit unique interacting protein partners. Moreover, genome-wide analysis using ChIP-seq provide evidence for a shared as well as a specific regulation of different sets of genes.

Conclusions: Our study supports the idea that Rett syndrome might arise from simultaneous impairment of cellular processes involving non-overlapping functions of MECP2 isoforms. For instance, MeCP2-E1 mutations might impact stimuli-dependent chromatin regulation, while MeCP2-E2 mutations could result in aberrant ribosomal expression. Overall, our findings provide insight into the functional complexity of MeCP2 by dissecting differential aspects of its two isoforms.
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http://dx.doi.org/10.1186/s13072-019-0298-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786283PMC
October 2019

Tinkering with Binding Polynomials in Isothermal Titration Calorimetry.

Methods Mol Biol 2019 ;1964:185-213

Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, Zaragoza, Spain.

Isothermal titration calorimetry (ITC) has become the preferred experimental technique for characterizing intermolecular interactions between biological molecules. Among the several advantages, the use of natural non-labeled molecules and the determination of the complete thermodynamic profile for the interaction in solution remain as the primary features that have promoted ITC to the forefront of experimental biophysics. The experimental design in ITC may range from studying a simple direct binary macromolecule-ligand interaction to studying the homotropic or heterotropic cooperative effect between ligands when interacting with a given macromolecule. The theory of the binding polynomial has proven to be an appropriate unifying framework for handling the complexities that can be encountered when studying macromolecule-ligand interactions, though it has been deemed troublesome. The goal of this chapter is to provide a quite simple and widely available set of training experiments aimed at mastering the formalism of the binding polynomial applied to isothermal titration calorimetry.
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http://dx.doi.org/10.1007/978-1-4939-9179-2_14DOI Listing
August 2019

Stereoselective synthesis and biological evaluation as inhibitors of hepatitis C virus RNA polymerase of GSK3082 analogues with structural diversity at the 5-position.

Eur J Med Chem 2019 Jun 12;171:401-419. Epub 2019 Mar 12.

Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Orgánica, Pedro Cerbuna 12, 50009 Zaragoza, Spain. Electronic address:

GSK3082 - a hepatitis C virus RNA polymerase inhibitor - and a series of analogues with structural diversity at the 5-position were prepared from a 2,2,4,5-tetrasubstituted pyrrolidine obtained with a well-defined stereochemistry from the 1,3-dipolar cycloaddition of the chiral imino ester derived from leucine tert-butyl ester and (R)-2,3-O-isopropylideneglyceraldehyde with methyl acrylate. The chiral 2,2-dimethyl-1,3-dioxolane moiety provided by the glyceraldehyde served as a synthetic equivalent for different substituents and functional groups and these transformations usually required mild reaction conditions and simple work-up procedures. The inhibitory activity of the resulting GSK3082 analogues was studied in vitro in a cell-based assay of the subgenomic HCV RNA replication system. Some of the analogues showed good inhibitory activity with IC50 values in the nanomolar concentration range.
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http://dx.doi.org/10.1016/j.ejmech.2019.03.019DOI Listing
June 2019

Cationic poly(ester amide) dendrimers: alluring materials for biomedical applications.

J Mater Chem B 2018 Jun 31;6(23):3956-3968. Epub 2018 May 31.

Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Spain.

Novel cationic poly(ester amide) dendrimers have been synthesized by copper(i) azide-alkyne cycloaddition (CuAAC) of a tripropargylamine core and azide-terminated dendrons, in turn prepared by iterative amide coupling of the new monomer 2,2'-bis(glycyloxymethyl)propionic acid (bis-GMPA). The alternation of ester and amide groups provided a dendritic scaffold that was totally biocompatible and degradable in aqueous media at physiological and acidic pH. The tripodal dendrimers naturally formed rounded aggregates with a drug that exhibited low water solubility, camptothecin, thus improving its cell viability and anti-Hepatitis C virus (anti-HCV) activity. The presence of numerous peripheral cationic groups enabled these dendrimers to form dendriplexes with both pDNA and siRNA and they showed effective in vitro siRNA transfection in tumoral and non-tumoral cell lines.
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http://dx.doi.org/10.1039/c8tb00639cDOI Listing
June 2018

Differential NtcA Responsiveness to 2-Oxoglutarate Underlies the Diversity of C/N Balance Regulation in .

Front Microbiol 2017 9;8:2641. Epub 2018 Jan 9.

Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CeiA3, Universidad de Córdoba, Córdoba, Spain.

Previous studies showed differences in the regulatory response to C/N balance in with respect to other cyanobacteria, but no information was available about its causes, or the ecological advantages conferred to thrive in oligotrophic environments. We addressed the changes in key enzymes (glutamine synthetase, isocitrate dehydrogenase) and the gene (the global nitrogen regulator) involved in C/N metabolism and its regulation, in three model strains: MED4, SS120, and MIT9313. We observed a remarkable level of diversity in their response to azaserine, a glutamate synthase inhibitor which increases the concentration of the key metabolite 2-oxoglutarate, used to sense the C/N balance by cyanobacteria. Besides, we studied the binding between the global nitrogen regulator (NtcA) and the promoter of the gene in the same strains, and its dependence on the 2-oxoglutarate concentration, by using isothermal titration calorimetry, surface plasmon resonance, and electrophoretic mobility shift. Our results show a reduction in the responsiveness of NtcA to 2-oxoglutarate in , especially in the MED4 and SS120 strains. This suggests a trend to streamline the regulation of C/N metabolism in late-branching strains (MED4 and SS120), in adaptation to the rather stable conditions found in the oligotrophic ocean gyres where this microorganism is most abundant.
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http://dx.doi.org/10.3389/fmicb.2017.02641DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5767323PMC
January 2018

Thermodynamics of cooperative binding of FAD to human NQO1: Implications to understanding cofactor-dependent function and stability of the flavoproteome.

Arch Biochem Biophys 2017 12 31;636:17-27. Epub 2017 Oct 31.

Department of Physical Chemistry, University of Granada, Granada, Spain. Electronic address:

The stability of human flavoproteins strongly depends on flavin levels, although the structural and energetic basis of this relationship is poorly understood. Here, we report an in-depth analysis on the thermodynamics of FAD binding to one of the most representative examples of such relationship, NAD(P)H:quinone oxidoreductase 1 (NQO1). NQO1 is a dimeric enzyme that tightly binds FAD, which triggers large structural changes upon binding. A common cancer-associated polymorphism (P187S) severely compromises FAD binding. We show that FAD binding is described well by a thermodynamic model explicitly incorporating binding cooperativity when applied to different sets of calorimetric analyses and NQO1 variants, thus providing insight on the effects in vitro and in cells of cancer-associated P187S, its suppressor mutation H80R and the role of NQO1 C-terminal domain to modulate binding cooperativity and energetics. Furthermore, we show that FAD binding to NQO1 is very sensitive to physiologically relevant environmental conditions, such as the presence of phosphate buffer and salts. Overall, our results contribute to understanding at the molecular level the link between NQO1 stability and fluctuations of FAD levels intracellularly, and supports the notion that FAD binding energetics and cooperativity are fundamentally linked with the dynamic nature of apo-NQO1 conformational ensemble.
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http://dx.doi.org/10.1016/j.abb.2017.10.020DOI Listing
December 2017

A look at ligand binding thermodynamics in drug discovery.

Expert Opin Drug Discov 2017 Apr 1;12(4):363-377. Epub 2017 Mar 1.

a Institute of Biocomputation and Physics of Complex Systems (BIFI), IQFR-CSIC-BIFI and GBsC-CSIC-BIFI Joint Units , Universidad de Zaragoza , Zaragoza , Spain.

Introduction: Drug discovery is a challenging endeavor requiring the interplay of many different research areas. Gathering information on ligand binding thermodynamics may help considerably in reducing the risk within a high uncertainty scenario, allowing early rejection of flawed compounds and pushing forward optimal candidates. In particular, the free energy, the enthalpy, and the entropy of binding provide fundamental information on the intermolecular forces driving such interaction. Areas covered: The authors review the current status and recent developments in the application of ligand binding thermodynamics in drug discovery. The thermodynamic binding profile (Gibbs energy, enthalpy, and entropy of binding) can be used for lead selection and optimization (binding enthalpy, selectivity, and adaptability). Expert opinion: Binding thermodynamics provides fundamental information on the forces driving the formation of the drug-target complex. It has been widely accepted that binding thermodynamics may be used as a decision criterion along the ligand optimization process in drug discovery and development. In particular, the binding enthalpy may be used as a guide when selecting and optimizing compounds over a set of potential candidates. However, this has been recently called into question by arguing certain difficulties and in the light of certain experimental examples.
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http://dx.doi.org/10.1080/17460441.2017.1297418DOI Listing
April 2017

The intervening domain from MeCP2 enhances the DNA affinity of the methyl binding domain and provides an independent DNA interaction site.

Sci Rep 2017 01 31;7:41635. Epub 2017 Jan 31.

Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, Zaragoza, 50018, Spain.

Methyl-CpG binding protein 2 (MeCP2) preferentially interacts with methylated DNA and it is involved in epigenetic regulation and chromatin remodelling. Mutations in MeCP2 are linked to Rett syndrome, the leading cause of intellectual retardation in girls and causing mental, motor and growth impairment. Unstructured regions in MeCP2 provide the plasticity for establishing interactions with multiple binding partners. We present a biophysical characterization of the methyl binding domain (MBD) from MeCP2 reporting the contribution of flanking domains to its structural stability and dsDNA interaction. The flanking disordered intervening domain (ID) increased the structural stability of MBD, modified its dsDNA binding profile from an entropically-driven moderate-affinity binding to an overwhelmingly enthalpically-driven high-affinity binding. Additionally, ID provided an additional site for simultaneously and autonomously binding an independent dsDNA molecule, which is a key feature linked to the chromatin remodelling and looping activity of MeCP2, as well as its ability to interact with nucleosomes replacing histone H1. The dsDNA interaction is characterized by an unusually large heat capacity linked to a cluster of water molecules trapped within the binding interface. The dynamics of disordered regions together with extrinsic factors are key determinants of MeCP2 global structural properties and functional capabilities.
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http://dx.doi.org/10.1038/srep41635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5282554PMC
January 2017

Shell Cross-Linked Polymeric Micelles as Camptothecin Nanocarriers for Anti-HCV Therapy.

Macromol Biosci 2015 Oct 5;15(10):1381-91. Epub 2015 Jun 5.

Departamento de Química Orgánica, Instituto de Ciencia de Materiales de Aragón (ICMA) - Universidad de Zaragoza-CSIC, 50009, Zaragoza, Spain.

A suitable carrier for camptothecin to act as therapy against the hepatitis C virus is presented. The carrier relies on an amphiphilic hybrid dendritic-linear-dendritic block copolymer, derived from pluronic F127 and bis-MPA dendrons, that forms micelles in aqueous solution. The dendrons admit the incorporation of multiple photoreactive groups that allow the clean and effective preparation of covalently cross-linked polymeric micelles (CLPM), susceptible of loading hydrophilic and lipophilic molecules. Cell-uptake experiments using a newly designed fluorophore, derived from rhodamine B, demonstrate that the carrier favors the accumulation of its cargo within the cell. Furthermore, loaded with camptothecin, it is efficient in fighting against the hepatitis C virus while shows lower cytotoxicity than the free drug.
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http://dx.doi.org/10.1002/mabi.201500094DOI Listing
October 2015

Rescuing compound bioactivity in a secondary cell-based screening by using γ-cyclodextrin as a molecular carrier.

Int J Nanomedicine 2015 19;10:2249-59. Epub 2015 Mar 19.

Instituto Aragonés de Ciencias de la Salud (IACS), Zaragoza, Spain ; IIS Aragón, Zaragoza, Spain ; Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Unit IQFR-CSIC-BIFI, Universidad de Zaragoza, Zaragoza, Spain ; Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain.

In vitro primary screening for identifying bioactive compounds (inhibitors, activators or pharmacological chaperones) against a protein target results in the discovery of lead compounds that must be tested in cell-based efficacy secondary screenings. Very often lead compounds do not succeed because of an apparent low potency in cell assays, despite an excellent performance in primary screening. Primary and secondary screenings differ significantly according to the conditions and challenges the compounds must overcome in order to interact with their intended target. Cellular internalization and intracellular metabolism are some of the difficulties the compounds must confront and different strategies can be envisaged for minimizing that problem. Using a novel screening procedure we have identified 15 compounds inhibiting the hepatitis C NS3 protease in an allosteric fashion. After characterizing biophysically the interaction with the target, some of the compounds were not able to inhibit viral replication in cell assays. In order to overcome this obstacle and potentially improve cellular internalization three of these compounds were complexed with γ-cyclodextrin. Two of them showed a five- and 16-fold activity increase, compared to their activity when delivered as free compounds in solution (while γ-cyclodextrin did not show antiviral activity by itself). The most remarkable result came from a third compound that showed no antiviral activity in cell assays when delivered free in solution, but its γ-cyclodextrin complex exhibited a 50% effective concentration of 5 μM. Thus, the antiviral activity of these compounds can be significantly improved, even completely rescued, using γ-cyclodextrin as carrier molecule.
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http://dx.doi.org/10.2147/IJN.S79480DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4371900PMC
October 2016
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