1,720,984 research outputs found
Homology modeling and docking analysis of the interaction between polyphenols and mammalian 20S proteasomes
No full textMolecular docking of small ligands to biologically active macromolecules has become a valuable strategy to predict the stability of complexes between potential partners and their binding modes. In this perspective, we applied this computational procedure to rationalize the reported role of polyphenols as inhibitors of the mammalian 20S proteasomes. In particular, polyphenols were shown to modulate each proteasomal activity at different extents both in the constitutive and the inducible enzyme. We performed a flexible molecular docking analysis between a set of polyphenols previously demonstrated to have the highest binding affinity and both the constitutive (from deposited PDB structures) and homology modeled active subunits of the IFN-γ inducible proteasome, to provide insight into the possible mechanism of interaction. Among the tested polyphenols, (-)-epigallocatechin-3-gallate showed the highest affinity for the proteasome subunits, both in terms of intermolecular energy and predicted equilibrium constants, in particular for β5 and β5i subunits (ETotal=-66 kcal/mol, Ki=81.3 μM and E Total=-83.9 kcal/mol, Ki=0.29 μM, respectively), known to be related to the chymotrypsin-like and BrAAP activities. Collectively, polyphenols showed a higher affinity for the inducible subunits, in agreement with previous in vitro studies. Additionally, different contributions to the interaction energy (van der Waals, electrostatic, H-bond) of proteasome-polyphenols complexes were dissected. © 2009 American Chemical Society
Sanguisorba minor extract suppresses plasmin-mediated mechanisms of cancer cell migration
No full textBackground: Sanguisorba minor, as well as several other edible herbs and vegetables, has been used extensively in traditional medicine. The observed beneficial effects can be attributed at least in part to the direct modulation of several enzymatic activities by its polyphenolic constituents. Methods: The ethanol extract of Sanguisorba minor was characterized by reversed-phase liquid chromatography, and most relevant analytes were identified by multiple stage mass spectrometry. The whole extract and the most relevant isolated constituents were tested for their ability to modulate the activity of human plasmin both toward a synthetic substrate and in human breast cancer cell culture models. Kinetic and equilibrium parameters were obtained by a concerted spectrophotometric and biosensor-based approach. Results: Quercetin-3- glucuronide was recognized as the compound mainly responsible for the in vitro plasmin inhibition by S. minor extract, with an inhibition constant in the high nanomolar range; in detail, our approach based on bioinformatic, enzymatic and binding analyses classified the inhibition as competitive. Most interestingly, cell-based assays showed that this flavonoid was effective in suppressing plasmin-induced loss of cancer cell adhesion. General significance: Our results show that the extract from Sanguisorba minor limits plasmin-mediated tumor cell motility in vitro, mostly due to quercetin-3-glucuronide. This glucuronated flavonoid is a promising template for rational designing of anticancer drugs to be used in the treatment of pathological states involving the unregulated activity of plasmin. © 2012 Elsevier B.V. All rights reserved
Interaction between wheat alpha-amylase/trypsin bi-functional inhibitor and mammalian digestive enzymes: Kinetic, equilibrium and structural characterization of binding
No full textAlpha-amylase/trypsin bi-functional inhibitors (ATIs) are non-gluten protein components of wheat and other cereals that can hypersensitise the human gastrointestinal tract, eventually causing enteropathies in predisposed individuals. These inhibitory proteins can act both directly by targeting specific pro-inflammatory receptors, and indirectly by impairing the activity of digestive enzymes, the latter event causing the accumulation of undigested peptides with potential immunogenic properties. Herein, according to a concerted approach based on in vitro and in silico methods we characterized kinetics, equilibrium parameters and modes of binding of the complexes formed between wheat ATI and two representative mammalian digestive enzymes, namely trypsin and alpha-amylase. Interestingly, we demonstrated ATI to target both enzymes with independent binding sites and with moderately high affinity
The relationship between the 20S proteasomes and prion-mediated neurodegenerations: Potential therapeutic opportunities
No full textThe dysfunction of cellular degradation pathways of aberrant and misfolded proteins is a critical event in the onset of neurodegenerative disorders. Among these pathologies, prion diseases are a unique class of transmissible fatal disorders affecting mammals, characterized by the presence of an abnormal isoform of a membrane-bound protein, namely the prion protein. The proteasome is the main proteolytic machinery in charge of removing damaged, oxidized and misfolded proteins and numerous authors have approached the involvement of this complex in the prion protein cellular processing. Herein, we described the general features of prion disorders focusing our attention on the available data on the interplay between the infectious agent and the proteasome system, exploring its implications in prion-mediated toxicity. Finally, considering the proteasome as a potential drug target, we reviewed possible therapeutic opportunities in the treatment of such pathologies. © 2010 Springer Science+Business Media, LLC
Natural occurring polyphenols as template for drug design. Focus on serine proteases
No full textSeveral major physio-pathological processes, including cancer, inflammatory states and thrombosis, are all strongly dependent upon the fine regulation of proteolytic enzyme activities, and dramatic are the consequences of unbalanced equilibria between enzymes and their cognate inhibitors. In this perspective, the discovery of small-molecule ligands able to modulate catalytic activities has a massive therapeutic potential and is a stimulating goal. Numerous recent experimental evidences revealed that proteolytic enzymes can be opportunely targeted, reporting on small ligands capable of binding to these biological macromolecules with drug-like potencies, and primarily with comparable (or even higher) efficiency with respect to their endogenous binding partner. In particular, natural occurring polyphenols and their derivatives recently disclosed these intriguing abilities, making them promising templates for drug design and development. In this review, we compared the inhibitory capacities of a set of monomeric polyphenols toward serine proteases activity, and finally summarized the data with an emphasis on the derivation of a pharmacophore model. © 2009 John Wiley and Sons A/S
Identification of an EGCG oxidation derivative with proteasome modulatory activity
No full text(-)-epigallocatechin-3-gallate (EGCG) has been shown to possess chemopreventative properties and the ability to inhibit proteasome, a multicatalytic protease involved in the removal of oxidized and misfolded proteins and in the turnover of important checkpoint proteins. The stability of EGCG under neutral-alkaline and cellular physiological conditions was evaluated, identifying a biologically active ring-fission oxidative product. This derivative differentially affected proteasome activities with respect to EGCG in vitro, whereas, in cervical carcinoma cells, both compounds inhibited proteasome functionality to a similar extent, promoting a significant accumulation of ubiquitinated proteins and apoptotic markers. Despite of EGCG high instability, an equally active metabolite, able to modulate both proteasome functionality and apoptotic pathways, is generated. Interestingly this derivative protracts both the EGCG antioxidant and proteasome modulating efficacy, irrespective of the catechin short half-life. © 2011 Elsevier Masson SAS. All rights reserved
The fine-tuning of proteolytic pathways in Alzheimer’s disease
No full textSeveral integrated proteolytic systems contribute to the maintenance of cellular homeostasis through the continuous removal of misfolded, aggregated or oxidized proteins and damaged organelles. Among these systems, the proteasome and autophagy play the major role in protein quality control, which is a fundamental issue in non-proliferative cells such as neurons. Disturbances in the functionality of these two pathways are frequently observed in neurodegenerative diseases, like Alzheimer’s disease, and reflect the accumulation of protease-resistant, deleterious protein aggregates. In this review, we explored the sophisticated crosstalk between the ubiquitin–proteasome system and autophagy in the removal of the harmful structures that characterize Alzheimer’s disease neurons. We also dissected the role of the numerous shuttle factors and chaperones that, directly or indirectly interacting with ubiquitin and LC3, are used for cargo selection and delivery to one pathway or the other
Targeting proteasomes with naturally occurring compounds in cancer treatment
No full textAberrant cellular proliferation and compromised apoptotic pathways are hallmarks of cancer aggressiveness, and in this framework, the role of protein degradation machineries have been extensively dissected. Among proteases, the proteasome is unequivocally central in the intracellular regulation of both these processes, thus several proteasome-directed therapies have been investigated, aiming at controlling its activity and possibly restoring normal cell functions. Numerous studies reported proteasome inhibitors (both synthetic and natural occurring) to potently and selectively induce apoptosis in many types of cancer cells. In this review, we discuss recent advances in proteasomal modulation by some natural occurring polyphenols, globally providing evidence of the proteasome role as therapeutic target in cancer treatment. © 2011 Bentham Science Publishers Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
