Publications by authors named "Sara Sattin"

26 Publications

  • Page 1 of 1

DC/L-SIGN recognition of spike glycoprotein promotes SARS-CoV-2 trans-infection and can be inhibited by a glycomimetic antagonist.

PLoS Pathog 2021 05 20;17(5):e1009576. Epub 2021 May 20.

Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France.

The efficient spread of SARS-CoV-2 resulted in a unique pandemic in modern history. Despite early identification of ACE2 as the receptor for viral spike protein, much remains to be understood about the molecular events behind viral dissemination. We evaluated the contribution of C-type lectin receptors (CLRS) of antigen-presenting cells, widely present in respiratory mucosa and lung tissue. DC-SIGN, L-SIGN, Langerin and MGL bind to diverse glycans of the spike using multiple interaction areas. Using pseudovirus and cells derived from monocytes or T-lymphocytes, we demonstrate that while virus capture by the CLRs examined does not allow direct cell infection, DC/L-SIGN, among these receptors, promote virus transfer to permissive ACE2+ Vero E6 cells. A glycomimetic compound designed against DC-SIGN, enable inhibition of this process. These data have been then confirmed using authentic SARS-CoV-2 virus and human respiratory cell lines. Thus, we described a mechanism potentiating viral spreading of infection.
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http://dx.doi.org/10.1371/journal.ppat.1009576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136665PMC
May 2021

Homology Model of a Catalytically Competent Bifunctional Rel Protein.

Front Mol Biosci 2021 3;8:628596. Epub 2021 Feb 3.

Department of Chemistry, Università Degli Studi di Milano, Milan, Italy.

Bacteria have developed different bet hedging strategies to survive hostile environments and stressful conditions with persistency being maybe the most elegant yet still poorly understood one. Persisters' temporary tolerance to antibiotic treatment hints at their role not only in chronic and recurrent infections but also in the insurgence of resistant strains. Therefore, hampering persisters formation might represent an innovative strategy in the quest for new effective antimicrobial compounds. Among the molecular mechanisms postulated for the persister phenotypic switch, we decided to focus our attention on the stringent response and, in particular, on the upstream triggering step that is the accumulation of guanosine tetra- and pentaphosphate, collectivity called (p)ppGpp. Intracellular levels of (p)ppGpp are regulated by a superfamily of enzymes called RSH (RelA/SpoT homologue) that are able to promote its synthesis pyrophosphate transfer from an ATP molecule to the 3' position of either GDP or GTP. These enzymes are classified based on the structural domain(s) present (only synthetase, only hydrolase, or both). Here we present our work on Rel (from ), still the only bifunctional Rel protein for which a GDP-bound "synthetase-ON" structure is available. Analysis of the synthetase site, occupied only by GDP, revealed a partially active state, where the supposed ATP binding region is not conformationally apt to accommodate it. In order to achieve a protein model that gets closer to a fully active state, we generated a chimera structure of Rel by homology modeling, starting from the crystal structure of the catalytically competent state of RelP, a smaller, single-domain, Rel protein from . Molecular dynamics simulations allowed verifying the stability of the generated chimera model. Virtual screening and ligand design studies are underway.
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http://dx.doi.org/10.3389/fmolb.2021.628596DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7983052PMC
February 2021

Behavior of glycolylated sialoglycans in the binding pockets of murine and human CD22.

iScience 2021 Jan 29;24(1):101998. Epub 2020 Dec 29.

Dipartimento di Scienze Chimiche, Complesso Universitario Monte Sant'Angelo, Università di Napoli Federico II, Via Cintia 4, 80126 Napoli, Italy.

Siglecs (sialic acid binding immunoglobulin (Ig)-like lectins) constitute a group of 15 human and 9 murine cell-surface transmembrane receptors belonging to the I-type lectin family, mostly expressed on innate immune cells and characterized by broadly similar structural features. Here, the prominent inhibitory CD22 (Siglec-2), well known in maintaining tolerance and preventing autoimmune responses on B cells, is studied in its human and murine forms in complex with sialoglycans. In detail, the role of the -glycolyl neuraminic acid (Neu5Gc) moiety in the interaction with both orthologues was explored. The analysis of the binding mode was carried out by the combination of NMR spectroscopy, computational approaches, and CORCEMA-ST calculations. Our findings provide a first model of Neu5Gc recognition by h-CD22 and show a comparable molecular recognition profile by h- and m-CD22. These data open the way to innovative diagnostic and/or therapeutic methodologies to be used in the modulation of the immune responses.
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http://dx.doi.org/10.1016/j.isci.2020.101998DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7811138PMC
January 2021

When the Others Become Us: A Chemist's Perspective of the COVID-19 Outbreak in Italy.

ACS Chem Biol 2020 06 8;15(6):1279-1281. Epub 2020 May 8.

Chemistry Department, Università degli Studi di Milano, Milan 20133, Italy.

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http://dx.doi.org/10.1021/acschembio.0c00289DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7216762PMC
June 2020

Enhancing Potency and Selectivity of a DC-SIGN Glycomimetic Ligand by Fragment-Based Design: Structural Basis.

Chemistry 2019 Nov 18;25(64):14659-14668. Epub 2019 Oct 18.

Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, 38044, Grenoble, France.

Chemical modification of pseudo-dimannoside ligands guided by fragment-based design allowed for the exploitation of an ammonium-binding region in the vicinity of the mannose-binding site of DC-SIGN, leading to the synthesis of a glycomimetic antagonist (compound 16) of unprecedented affinity and selectivity against the related lectin langerin. Here, the computational design of pseudo-dimannoside derivatives as DC-SIGN ligands, their synthesis, their evaluation as DC-SIGN selective antagonists, the biophysical characterization of the DC-SIGN/16 complex, and the structural basis for the ligand activity are presented. On the way to the characterization of this ligand, an unusual bridging interaction within the crystals shed light on the plasticity and potential secondary binding sites within the DC-SIGN carbohydrate recognition domain.
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http://dx.doi.org/10.1002/chem.201903391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899773PMC
November 2019

Optimised Synthesis of the Bacterial Magic Spot (p)ppGpp Chemosensor PyDPA.

Chembiochem 2019 07 24;20(13):1717-1721. Epub 2019 May 24.

Department of Chemistry, Università degli Studi di Milano, via Golgi, 19, 20133, Milano, Italy.

Guanosine penta- or tetraphosphate (pppGpp or ppGpp, respectively) is a nucleotide signalling molecule with a marked effect on bacterial physiology during stress. Its accumulation slows down cell metabolism and replication, supposedly leading to the formation of the antibiotic-tolerant persister phenotype. A specifically tailored fluorescent chemosensor, PyDPA, allows the detection of (p)ppGpp in solution with high selectivity, relative to that of other nucleotides. Herein, an optimised synthetic approach is presented that improves the overall yield from 9 to 67 % over 7 steps. The simplicity and robustness of this approach will allow groups investigating the many facets of (p)ppGpp easy access to this probe.
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http://dx.doi.org/10.1002/cbic.201900013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6618120PMC
July 2019

Chaperones rescue the energetic landscape of mutant CFTR at single molecule and in cell.

Nat Commun 2017 08 30;8(1):398. Epub 2017 Aug 30.

Department of Physiology, McGill University, Montréal, QC, Canada, H3G 1Y6.

Molecular chaperones are pivotal in folding and degradation of the cellular proteome but their impact on the conformational dynamics of near-native membrane proteins with disease relevance remains unknown. Here we report the effect of chaperone activity on the functional conformation of the temperature-sensitive mutant cystic fibrosis channel (∆F508-CFTR) at the plasma membrane and after reconstitution into phospholipid bilayer. Thermally induced unfolding at 37 °C and concomitant functional inactivation of ∆F508-CFTR are partially suppressed by constitutive activity of Hsc70 and Hsp90 chaperone/co-chaperone at the plasma membrane and post-endoplasmic reticulum compartments in vivo, and at single-molecule level in vitro, indicated by kinetic and thermodynamic remodeling of the mutant gating energetics toward its wild-type counterpart. Thus, molecular chaperones can contribute to functional maintenance of ∆F508-CFTR by reshaping the conformational energetics of its final fold, a mechanism with implication in the regulation of metastable ABC transporters and other plasma membrane proteins activity in health and diseases.The F508 deletion (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) is the most common CF causing mutation. Here the authors show that cytosolic chaperones shift the F508del channel conformation to the native fold by kinetic and thermodynamic remodelling of the gating energetics towards that of wild-type CTFR.
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http://dx.doi.org/10.1038/s41467-017-00444-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577305PMC
August 2017

The small RNA ReaL: a novel regulatory element embedded in the Pseudomonas aeruginosa quorum sensing networks.

Environ Microbiol 2017 10 15;19(10):4220-4237. Epub 2017 Sep 15.

Department of Biosciences, Università degli Studi di Milano, Milano, Italy.

The small RNA ReaL of the opportunistic pathogen Pseudomonas aeruginosa has been characterized. Our results indicate that ReaL contributes to P. aeruginosa virulence. In the Galleria mellonella infection model, reaL gene deletion resulted in decreased virulence, while ReaL overexpression resulted in a hyper-virulent phenotype. We also demonstrate that ReaL is embedded in the P. aeruginosa quorum sensing (QS) with the role of linking las to pqs systems. We show that ReaL is negatively regulated by the las regulator LasR and impacts positively the synthesis of the pqs quinolone signal PQS by a positive post-transcriptional effect on the pqsC gene. Perturbations of ReaL levels affect pyocyanin synthesis, biofilm formation and swarming motility, processes that are known to be influenced by PQS synthesis. In addition to being regulated by LasR, ReaL is also responding to infection relevant cues that P. aeruginosa can experience in mammalian hosts such as temperature and oxygen availability. Furthermore, ReaL shows a growth phase-dependent pattern of expression, being up-regulated in stationary phase, due to the activity of the alternative σ factor RpoS. Together, these regulations of ReaL expression are expected to contribute to the fine co-modulation of PQS synthesis and, ultimately, virulence.
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http://dx.doi.org/10.1111/1462-2920.13886DOI Listing
October 2017

Facile access to pseudo-thio-1,2-dimannoside, a new glycomimetic DC-SIGN antagonist.

Bioorg Med Chem 2017 10 22;25(19):5142-5147. Epub 2017 Mar 22.

Universita' degli Studi di Milano, Dipartimento di Chimica, via Golgi 19, 20133 Milano, Italy. Electronic address:

The synthesis and conformational analysis of pseudo-thio-1,2-dimannoside are described. This molecule mimics mannobioside (Manα(1,2)Man) and is an analog of pseudo-1,2-dimannoside, with expected increased stability to enzymatic hydrolysis. A short and efficient synthesis was developed based on an epoxide ring-opening reaction by a mannosyl thiolate, generated in situ from the corresponding thioacetate. NMR-NOESY studies supported by MM3 calculations showed that the pseudo-thio-1,2-dimannoside shares the conformational behavior of the pseudo-1,2-dimannoside and is a structural mimic of the natural disaccharide. Its affinity for DC-SIGN was measured by SPR and found to be comparable to the corresponding O-linked analog, offering good opportunities for further developments.
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http://dx.doi.org/10.1016/j.bmc.2017.03.046DOI Listing
October 2017

Design of Allosteric Stimulators of the Hsp90 ATPase as New Anticancer Leads.

Chemistry 2017 Apr 22;23(22):5188-5192. Epub 2017 Mar 22.

Istituto di Chimica del Riconoscimento Molecolare, CNR, via Mario Bianco, 9, 20131, Milan, Italy.

Allosteric compounds that stimulate Hsp90 adenosine triphosphatase (ATPase) activity were rationally designed, showing anticancer potencies in the low micromolar to nanomolar range. In parallel, the mode of action of these compounds was clarified and a quantitative model that links the dynamic ligand-protein cross-talk to observed cellular and in vitro activities was developed. The results support the potential of using dynamics-based approaches to develop original mechanism-based cancer therapeutics.
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http://dx.doi.org/10.1002/chem.201700169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5927549PMC
April 2017

Linear biocompatible glyco-polyamidoamines as dual action mode virus infection inhibitors with potential as broad-spectrum microbicides for sexually transmitted diseases.

Sci Rep 2016 09 19;6:33393. Epub 2016 Sep 19.

Dipartimento di Chimica, Università degli Studi di Milano, via C. Golgi 19, 20133 Milan, Italy.

The initial steps of viral infections are mediated by interactions between viral proteins and cellular receptors. Blocking the latter with high-affinity ligands may inhibit infection. DC-SIGN, a C-type lectin receptor expressed by immature dendritic cells and macrophages, mediates human immunodeficiency virus (HIV) infection by recognizing mannose clusters on the HIV-1 gp120 envelope glycoprotein. Mannosylated glycodendrimers act as HIV entry inhibitors thanks to their ability to block this receptor. Previously, an amphoteric, but prevailingly cationic polyamidoamine named AGMA1 proved effective as infection inhibitor for several heparan sulfate proteoglycan-dependent viruses, such as human papilloma virus HPV-16 and herpes simplex virus HSV-2. An amphoteric, but prevailingly anionic PAA named ISA23 proved inactive. It was speculated that the substitution of mannosylated units for a limited percentage of AGMA1 repeating units, while imparting anti-HIV activity, would preserve the fundamentals of its HPV-16 and HSV-2 infection inhibitory activity. In this work, four biocompatible linear PAAs carrying different amounts of mannosyl-triazolyl pendants, Man-ISA7, Man-ISA14, Man-AGMA6.5 and Man-AGMA14.5, were prepared by reaction of 2-(azidoethyl)-α-D-mannopyranoside and differently propargyl-substituted AGMA1 and ISA23. All mannosylated PAAs inhibited HIV infection. Both Man-AGMA6.5 and Man-AGMA14.5 maintained the HPV-16 and HSV-2 activity of the parent polymer, proving broad-spectrum, dual action mode virus infection inhibitors.
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http://dx.doi.org/10.1038/srep33393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027566PMC
September 2016

Molecular Dynamics Simulations Reveal the Mechanisms of Allosteric Activation of Hsp90 by Designed Ligands.

Sci Rep 2016 Apr 1;6:23830. Epub 2016 Apr 1.

Istituto di Chimica del Riconoscimento Molecolare, CNR (ICRM-CNR), via Mario Bianco, 9, 20131, Milan, Italy.

Controlling biochemical pathways through chemically designed modulators may provide novel opportunities to develop therapeutic drugs and chemical tools. The underlying challenge is to design new molecular entities able to act as allosteric chemical switches that selectively turn on/off functions by modulating the conformational dynamics of their target protein. We examine the origins of the stimulation of ATPase and closure kinetics in the molecular chaperone Hsp90 by allosteric modulators through atomistic molecular dynamics (MD) simulations and analysis of protein-ligand interactions. In particular, we focus on the cross-talk between allosteric ligands and protein conformations and its effect on the dynamic properties of the chaperone's active state. We examine the impact of different allosteric modulators on the stability, structural and internal dynamics properties of Hsp90 closed state. A critical aspect of this study is the development of a quantitative model that correlates Hsp90 activation to the presence of a certain compound, making use of information on the dynamic adaptation of protein conformations to the presence of the ligand, which allows to capture conformational states relevant in the activation process. We discuss the implications of considering the conformational dialogue between allosteric ligands and protein conformations for the design of new functional modulators.
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http://dx.doi.org/10.1038/srep23830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4817115PMC
April 2016

Glycoconjugates and Glycomimetics as Microbial Anti-Adhesives.

Trends Biotechnol 2016 06 12;34(6):483-495. Epub 2016 Feb 12.

Università degli Studi di Milano, Dipartimento di Chimica, via Golgi 19, 20133 Milano, Italy. Electronic address:

Microbial adhesion is an essential step in infection and is mediated primarily by protein-carbohydrate interactions. Antagonists of such interactions have become a promising target for anti-adhesive therapy in several infective diseases. Monovalent protein-sugar interactions are often weak, and most successful anti-adhesive materials consist of multivalent glycoconjugates. Although often very effective in hampering microbial adhesion, natural epitopes often show limited resistance to enzymatic degradation. The use of carbohydrate mimics (glycomimetics) as a replacement for natural sugars potentially allows higher metabolic stability and also higher selectivity towards the desired protein target. In this review we describe the state of the art in the design and synthesis of glycoconjugates and glycomimetics employed for the construction of anti-adhesive biomaterials.
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http://dx.doi.org/10.1016/j.tibtech.2016.01.004DOI Listing
June 2016

Scaffold Optimisation of Tetravalent Antagonists of the Mannose Binding Lectin.

Chemistry 2016 Mar 15;22(11):3686-91. Epub 2016 Jan 15.

Department of Chemistry, Universita' degli Studi di Milano, via Golgi 19, 20133, Milano, Italy.

Antagonists of mannose binding lectin (MBL) have shown a protective role against brain reperfusion damage after acute ischemic stroke. Here we describe the design and streamlined synthesis of glycomimetic MBL antagonists based on a new tetravalent dendron scaffold. The dendron was developed by optimisation of a known polyester structure previously demonstrated to be very efficient for ligand presentation to MBL. Replacement of a labile succinyl ester bond with a more robust amide functionality, use of a longer and more hydrophilic linker, fast modular synthesis and orthogonal functionalisation at the focal point are the main features of the new scaffold. The glycoconjugate constructs become stable to silica gel chromatography and to water solutions at physiological pH, while preserving water solubility and activity in an SPR assay against the murine MBL-C isoform. Higher-order constructs were easily assembled, as demonstrated by the synthesis of a 16-valent dendrimer, which leads to two orders of magnitude increase in activity over the tetravalent version against MBL-C.
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http://dx.doi.org/10.1002/chem.201504388DOI Listing
March 2016

Activation of Hsp90 Enzymatic Activity and Conformational Dynamics through Rationally Designed Allosteric Ligands.

Chemistry 2015 Sep 18;21(39):13598-608. Epub 2015 Aug 18.

Istituto di Chimica del Riconoscimento Molecolare, CNR via Mario Bianco, 9, 20131, Milan (Italy).

Hsp90 is a molecular chaperone of pivotal importance for multiple cell pathways. ATP-regulated internal dynamics are critical for its function and current pharmacological approaches block the chaperone with ATP-competitive inhibitors. Herein, a general approach to perturb Hsp90 through design of new allosteric ligands aimed at modulating its functional dynamics is proposed. Based on the characterization of a first set of 2-phenylbenzofurans showing stimulatory effects on Hsp90 ATPase and conformational dynamics, new ligands were developed that activate Hsp90 by targeting an allosteric site, located 65 Å from the active site. Specifically, analysis of protein responses to first-generation activators was exploited to guide the design of novel derivatives with improved ability to stimulate ATP hydrolysis. The molecules' effects on Hsp90 enzymatic, conformational, co-chaperone and client-binding properties were characterized through biochemical, biophysical and cellular approaches. These designed probes act as allosteric activators of the chaperone and affect the viability of cancer cell lines for which proper functioning of Hsp90 is necessary.
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http://dx.doi.org/10.1002/chem.201502211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5921052PMC
September 2015

Carbohydrates: A phenol sandwich fights diabetes.

Nat Chem Biol 2015 Sep;11(9):635-6

Department of Chemistry, Universita' degli Studi di Milano, Milano, Italy.

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http://dx.doi.org/10.1038/nchembio.1888DOI Listing
September 2015

Unique DC-SIGN clustering activity of a small glycomimetic: A lesson for ligand design.

ACS Chem Biol 2014 Jun 6;9(6):1377-85. Epub 2014 May 6.

Univ. Grenoble Alpes, Institut de Biologie Structurale (IBS) , Grenoble F-38027, France.

DC-SIGN is a dendritic cell-specific C-type lectin receptor that recognizes highly glycosylated ligands expressed on the surface of various pathogens. This receptor plays an important role in the early stages of many viral infections, including HIV, which makes it an interesting therapeutic target. Glycomimetic compounds are good drug candidates for DC-SIGN inhibition due to their high solubility, resistance to glycosidases, and nontoxicity. We studied the structural properties of the interaction of the tetrameric DC-SIGN extracellular domain (ECD), with two glycomimetic antagonists, a pseudomannobioside (1) and a linear pseudomannotrioside (2). Though the inhibitory potency of 2, as measured by SPR competition experiments, was 1 order of magnitude higher than that of 1, crystal structures of the complexes within the DC-SIGN carbohydrate recognition domain showed the same binding mode for both compounds. Moreover, when conjugated to multivalent scaffolds, the inhibitory potencies of these compounds became uniform. Combining isothermal titration microcalorimetry, analytical ultracentrifugation, and dynamic light scattering techniques to study DC-SIGN ECD interaction with these glycomimetics revealed that 2 is able, without any multivalent presentation, to cluster DC-SIGN tetramers leading to an artificially overestimated inhibitory potency. The use of multivalent scaffolds presenting 1 or 2 in HIV trans-infection inhibition assay confirms the loss of potency of 2 upon conjugation and the equal efficacy of chemically simpler compound 1. This study documents a unique case where, among two active compounds chemically derived, the compound with the lower apparent activity is the optimal lead for further drug development.
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http://dx.doi.org/10.1021/cb500054hDOI Listing
June 2014

Synthesis of potential allosteric modulators of Hsp90 by chemical glycosylation of Eupomatenoid-6.

Carbohydr Res 2014 05 13;390:33-41. Epub 2014 Mar 13.

Università degli Studi di Milano, Dipartimento di Chimica, via Golgi 19, 20133 Milano, Italy. Electronic address:

Hsp90 (Heat shock protein-90) is a chaperone protein and an established anti-apoptotic target in cancer therapy. Most of the known small-molecule inhibitors that have shown potent antitumor activity target the Hsp90 N-terminal domain and directly inhibit its ATP-ase activity. Many of these molecules display important secondary effects. A different approach to Hsp90 inhibition consists of targeting the protein C-terminal domain (CTD) and modulating its chaperone activity through allosteric effects. Using an original computational approach, allosteric hot-spots in the CTD have been recently identified that control interdomain communication. A combination of virtual and experimental screening enabled identification of a rhamnosylated benzofuran (Eupomatenoid-2) as a lead for further development. In this paper we describe glycodiversification of Eupomatenoid-2 using chemical glycosylation of the 2-(4'-hydroxyphenyl)benzofuran aglycon (a.k.a. Eupomatenoid-6). Glycosylation of the phenol by glycosyl bromides under basic conditions afforded the desired products in the gluco-, galacto-, and fuco-series. This approach failed in the manno- and rhamno-series. However, mannosylation and rhamnosylation of Eupomatenoid-6 could be obtained under carefully controlled acidic conditions, using O-benzoxazolyl imidate (OBox) donors. The glycosides obtained are currently under investigation as modulators of Hsp90 chaperone activity.
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http://dx.doi.org/10.1016/j.carres.2014.03.006DOI Listing
May 2014

Pseudo-mannosylated DC-SIGN ligands as potential adjuvants for HIV vaccines.

Viruses 2014 Jan 27;6(2):391-403. Epub 2014 Jan 27.

Department of Pathophysiology and Transplantation, University of Milan, Via F.lli VCervi 93, 20090 Milan, Italy.

The development of new and effective adjuvants may play a fundamental role in improving HIV vaccine efficacy. New classes of vaccine adjuvants activate innate immunity receptors, notably toll like receptors (TLRs). Adjuvants targeting the C-Type lectin receptor DC-SIGN may be alternative or complementary to adjuvants based on TRL activation. Herein we evaluate the ability of the glycomimetic DC-SIGN ligand Polyman 19 (PM 19) to modulate innate immune responses. Results showed that PM 19 alone, or in combination with TLR agonists, induces the expression of cytokines, β chemokines and co-stimulatory molecules that may, in turn, modulate adaptive immunity and exert anti-viral effects. These results indicate that the suitability of this compound as a vaccine adjuvant should be further evaluated.
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http://dx.doi.org/10.3390/v6020391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3939462PMC
January 2014

Structure of a glycomimetic ligand in the carbohydrate recognition domain of C-type lectin DC-SIGN. Structural requirements for selectivity and ligand design.

J Am Chem Soc 2013 Feb 8;135(7):2518-29. Epub 2013 Feb 8.

Institut de Biologie Structurale, Université Grenoble I, 41 rue Jules Horowitz, Grenoble, F-38027, France.

In genital mucosa, different fates are described for HIV according to the subtype of dendritic cells (DCs) involved in its recognition. This notably depends on the C-type lectin receptor, langerin or DC-SIGN, involved in gp120 interaction. Langerin blocks HIV transmission by its internalization in specific organelles of Langerhans cells. On the contrary, DC-SIGN enhances HIV trans-infection of T lymphocytes. Thus, approaches aiming to inhibit DC-SIGN, without blocking langerin, represent attractive anti-HIV strategies. We previously demonstrated that dendrons bearing multiple copies of glycomimetic compounds were able to block DC-SIGN-dependent HIV infection in cervical explant models. Optimization of such ligand requires detailed characterization of its binding mode. In the present work, we determined the first high-resolution structure of a glycomimetic/DC-SIGN complex by X-ray crystallography. This glycomimetic, pseudo-1,2-mannobioside, shares shape and conformational properties with Manα1-2Man, its natural counterpart. However, it uses the binding epitope previously described for Lewis X, a ligand specific for DC-SIGN among the C-type lectin family. Thus, selectivity gain for DC-SIGN versus langerin is observed with pseudo-1,2-mannobioside as shown by surface plasmon resonance analysis. In parallel, ligand binding was also analyzed by TR-NOESY and STD NMR experiments, combined with the CORCEMA-ST protocol. These studies demonstrate that the complex, defined by X-ray crystallography, represents the unique binding mode of this ligand as opposed to the several binding orientations described for the natural ligand. This exclusive binding mode and its selective interaction properties position this glycomimetic as a good lead compound for rational improvement based on a structurally driven approach.
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http://dx.doi.org/10.1021/ja3053305DOI Listing
February 2013

Giant regular polyhedra from calixarene carboxylates and uranyl.

Nat Commun 2012 Apr 17;3:785. Epub 2012 Apr 17.

Institute of Chemical Research of Catalonia (ICIQ), Avda. Països Catalans 16, Tarragona, Spain.

Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO(2)2+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components.
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http://dx.doi.org/10.1038/ncomms1793DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337980PMC
April 2012

Pseudosaccharide functionalized dendrimers as potent inhibitors of DC-SIGN dependent Ebola pseudotyped viral infection.

Bioconjug Chem 2011 Jul 20;22(7):1354-65. Epub 2011 Jun 20.

Laboratorio de Microbiologa Molecular, Instituto de Investigación Hospital 12 de Octubre (imas12), 28041 Madrid, Spain.

The development of compounds with strong affinity for the receptor DC-SIGN is a topic of remarkable interest due to the role that this lectin plays in several pathogen infection processes and in the modulation of the immune response. DC-SIGN recognizes mannosylated and fucosylated oligosaccharides in a multivalent manner. Therefore, multivalent carbohydrate systems are required to interact in an efficient manner with this receptor and compete with the natural ligands. We have previously demonstrated that linear pseudodi- and pseudotrisaccharides are adequate ligands for DC-SIGN. In this work, we show that multivalent presentations of these glycomimetics based on polyester dendrons and dendrimers lead to very potent inhibitors (in the nanomolar range) of cell infection by Ebola pseudotyped viral particles by blocking DC-SIGN receptor. Furthermore, SPR model experiments confirm that the described multivalent glycomimetic compounds compete in a very efficient manner with polymannosylated ligands for binding to DC-SIGN.
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http://dx.doi.org/10.1021/bc2000403DOI Listing
July 2011

Design, synthesis and activity evaluation of mannose-based DC-SIGN antagonists.

Mol Divers 2011 May 14;15(2):347-60. Epub 2010 Nov 14.

Department of Biotechnology, Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia.

In this article, we describe the design, synthesis and activity evaluation of glycomimetic DC-SIGN antagonists, that use a mannose residue to anchor to the protein carbohydrate recognition domain (CRD). The molecules were designed from the structure of the known pseudo-mannobioside antagonist 1, by including additional hydrophobic groups, which were expected to engage lipophilic areas of DC-SIGN CRD. The results demonstrate that the synthesized compounds potently inhibit DC-SIGN-mediated adhesion to mannan coated plates. Additionally, in silico docking studies were performed to rationalize the results and to suggest further optimization.
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http://dx.doi.org/10.1007/s11030-010-9285-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7089406PMC
May 2011

An assay for functional dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) inhibitors of human dendritic cell adhesion.

Anal Biochem 2010 Nov 25;406(2):222-9. Epub 2010 Jul 25.

Department of Biotechnology, Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia.

We report a new dendritic cell adhesion assay, using either immature or mature dendritic cells, for identifying functional dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) inhibitors. Because immature dendritic cells are responsible for pathogen binding and invasion, this in vitro assay provides an important link between in vitro results and pathogen-based in vivo assays. Furthermore, this assay does not require laborious expression, refolding, and purification of DC-SIGN carbohydrate recognition domain or extracellular domain as receptor-based assays. The assay power evaluated with Z and Z' parameters enables screening of compound libraries and determination of IC(50) values in the first stage of DC-SIGN inhibitor development.
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http://dx.doi.org/10.1016/j.ab.2010.07.018DOI Listing
November 2010

Inhibition of DC-SIGN-mediated HIV infection by a linear trimannoside mimic in a tetravalent presentation.

ACS Chem Biol 2010 Mar;5(3):301-12

Dipartimento di Chimica Organica e Industriale and CISI, Universita degli Studi di Milano, Italy.

HIV infection is pandemic in humans and is responsible for millions of deaths every year. The discovery of new cellular targets that can be used to prevent the infection process represents a new opportunity for developing more effective antiviral drugs. In this context, dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN), a lectin expressed at the surface of immature dendritic cells and involved in the initial stages of HIV infection, is a promising therapeutic target. Herein we show the ability of a new tetravalent dendron containing four copies of a linear trimannoside mimic to inhibit the trans HIV infection process of CD4+ T lymphocytes at low micromolar range. This compound presents a high solubility in physiological media, a neglectable cytotoxicity, and a long-lasting effect and is based on carbohydrate-mimic units. Notably, the HIV antiviral activity is independent of viral tropism (X4 or R5). The formulation of this compound as a gel could allow its use as topical microbicide.
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http://dx.doi.org/10.1021/cb900216eDOI Listing
March 2010

1,2-Mannobioside mimic: synthesis, DC-SIGN interaction by NMR and docking, and antiviral activity.

ChemMedChem 2007 Jul;2(7):1030-6

Departamento de Química Bioorgánica, Instituto de Investigaciones Químicas, CSIC, Américo Vespucio 49, 41092 Sevilla, Spain.

The design and preparation of carbohydrate ligands for DC-SIGN is a topic of high interest because of the role played by this C-type lectin in immunity and infection processes. The low chemical stability of carbohydrates against enzymatic hydrolysis by glycosylases has stimulated the search for new alternatives more stable in vivo. Herein, we present a good alternative for a DC-SIGN ligand based on a mannobioside mimic with a higher enzymatic stability than the corresponding disaccharide. NMR and docking studies have been performed to study the interaction of this mimic with DC-SIGN in solution demonstrating that this pseudomannobioside is a good ligand for this lectin. In vitro studies using an infection model with Ebola pseudotyped virus demonstrates that this compound presents an antiviral activity even better than the corresponding disaccharide and could be an interesting ligand to prepare multivalent systems with higher affinities for DC-SIGN with potential biomedical applications.
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http://dx.doi.org/10.1002/cmdc.200700047DOI Listing
July 2007
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