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1.
Bioconjug Chem ; 35(3): 324-332, 2024 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-38366964

RESUMO

Immunoconjugates exploit the high affinity of monoclonal antibodies for a recognized antigen to selectively deliver a cytotoxic payload, such as drugs or radioactive nuclides, at the site of disease. Despite numerous techniques have been recently developed for site-selective bioconjugations of protein structures, reaction of ε-amine group of lysine residues with electrophilic reactants, such as activated esters (NHS), is the main method reported in the literature as it maintains proteins in their native conformation. Since antibodies hold a high number of lysine residues, a heterogeneous mixture of conjugates will be generated, which can result in decreased target affinity. Here, we report an intradomain regioselective bioconjugation between the monoclonal antibody Trastuzumab and the N-hydroxysuccinimide ester of the chelator 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) by a kinetically controlled reaction adding substoichiometric quantities of the activated ester to the mAb working at slightly basic pH. Liquid chromatography-mass spectrometry (LC-MS) analyses were carried out to assess the chelator-antibody ratio (CAR) and the number of chelating moieties linked to the mAb chains. Proteolysis experiments showed four lysine residues mainly involved in bioconjugation (K188 for the light chain and K30, K293, and K417 for the heavy chain), each of which was located in a different domain. Since the displayed intradomain regioselectivity, a domain mapping MS-workflow, based on a selective domain denaturation, was developed to quantify the percentage of chelator linked to each mAb domain. The resulting immunoconjugate mixture showed an average CAR of 0.9. About a third of the heavy chains were found as monoconjugated, whereas conjugation of the chelator in the light chain was negligible. Domain mapping showed the CH3 domain bearing 13% of conjugated DOTA, followed by CH2 and VH respectively bearing 12.5 and 11% of bonded chelator. Bioconjugation was not found in the CH1 domain, whereas for the light chain, only the CL domain was conjugated (6%). Data analysis based on LC-MS quantification of different analytical levels (intact, reduced chains, and domains) provided the immunoconjugate formulation. A mixture of immunoconjugates restricted to 15 species was obtained, and the percentage of each one within the mixture was calculated. In particular, species bearing 1 DOTA with a relative abundance ranging from 4 to 20-fold, in comparison to species bearing 2DOTA, were observed. Pairing of bioconjugation under kinetic control with the developed domain mapping MS-workflow could raise the standard of chemical quality for immunoconjugates obtained with commercially available reactants.


Assuntos
Imunoconjugados , Imunoconjugados/química , Lisina/química , Fluxo de Trabalho , Anticorpos Monoclonais/química , Quelantes , Ésteres
2.
Molecules ; 27(16)2022 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-36014310

RESUMO

In the last two decades, the amyloid hypothesis, i.e., the abnormal accumulation of toxic Aß assemblies in the brain, has been considered the mainstream concept sustaining research in Alzheimer's Disease (AD). However, the course of cognitive decline and AD development better correlates with tau accumulation rather than amyloid peptide deposition. Moreover, all clinical trials of amyloid-targeting drug candidates have been unsuccessful, implicitly suggesting that the amyloid hypothesis needs significant amendments. Accumulating evidence supports the existence of a series of potentially dangerous relationships between Aß oligomeric species and tau protein in AD. However, the molecular determinants underlying pathogenic Aß/tau cross interactions are not fully understood. Here, we discuss the common features of Aß and tau molecules, with special emphasis on: (i) the critical role played by metal dyshomeostasis in promoting both Aß and tau aggregation and oxidative stress, in AD; (ii) the effects of lipid membranes on Aß and tau (co)-aggregation at the membrane interface; (iii) the potential of small peptide-based inhibitors of Aß and tau misfolding as therapeutic tools in AD. Although the molecular mechanism underlying the direct Aß/tau interaction remains largely unknown, the arguments discussed in this review may help reinforcing the current view of a synergistic Aß/tau molecular crosstalk in AD and stimulate further research to mechanism elucidation and next-generation AD therapeutics.


Assuntos
Doença de Alzheimer , Amiloidose , Doença de Alzheimer/metabolismo , Amiloide , Peptídeos beta-Amiloides/metabolismo , Proteínas Amiloidogênicas , Humanos , Íons , Lipídeos/uso terapêutico , Metais , Proteínas tau/metabolismo
3.
Chemistry ; 26(57): 13072-13084, 2020 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-32488947

RESUMO

Islet amyloid polypeptide (IAPP) is a hormone co-secreted with insulin and zinc from pancreatic ß-cells. To overcome the low solubility of human IAPP, we characterized zinc complexes species formed with 1) a mutated form of rat-IAPP(1-37; R18 H) able to mimic the human IAPP, 2) the r-IAPP(1-37) and the IAPP(1-8) fragment. Stoichiometry, speciation and coordination features of zinc(II) complexes were unveiled by ESI-MS, potentiometry and NMR measurements combined with DFT and free-energy simulations. Mononuclear species start to form around pH 6; Zn2+ binds both His18 and N-amino terminus in rat-IAPP(1-37; R18 H). The in silico study allows us to assess not only a structured turn compact domain in r-IAPP(1-37) and r-IAPP(1-37; R18 H) featured by a different free energy barrier for the transition from the compact to elongated conformation upon the coordination of Zn2+ , but also to bring into light a coordination shell further stabilized by noncovalent interactions.


Assuntos
Zinco/química , Amiloide , Animais , Simulação por Computador , Complexos de Coordenação , Humanos , Insulina , Polipeptídeo Amiloide das Ilhotas Pancreáticas , Ratos
4.
Int J Mol Sci ; 21(20)2020 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-33066163

RESUMO

We investigate the interaction of hemin with four fragments of prion protein (PrP) containing from one to four histidines (PrP106-114, PrP95-114, PrP84-114, PrP76-114) for its potential relevance to prion diseases and possibly traumatic brain injury. The binding properties of hemin-PrP complexes have been evaluated by UV-visible spectrophotometric titration. PrP peptides form a 1:1 adduct with hemin with affinity that increases with the number of histidines and length of the peptide; the following log K1 binding constants have been calculated: 6.48 for PrP76-114, 6.1 for PrP84-114, 4.80 for PrP95-114, whereas for PrP106-114, the interaction is too weak to allow a reliable binding constant calculation. These constants are similar to that of amyloid-ß (Aß) for hemin, and similarly to hemin-Aß, PrP peptides tend to form a six-coordinated low-spin complex. However, the concomitant aggregation of PrP induced by hemin prevents calculation of the K2 binding constant. The turbidimetry analysis of [hemin-PrP76-114] shows that, once aggregated, this complex is scarcely soluble and undergoes precipitation. Finally, a detailed study of the peroxidase-like activity of [hemin-(PrP)] shows a moderate increase of the reactivity with respect to free hemin, but considering the activity over long time, as for neurodegenerative pathologies, it might contribute to neuronal oxidative stress.


Assuntos
Hemina/química , Fragmentos de Peptídeos/química , Proteínas Priônicas/química , Sítios de Ligação , Oxirredução , Fragmentos de Peptídeos/metabolismo , Polimerização , Ligação Proteica
5.
Inorg Chem ; 56(18): 11317-11325, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-28846410

RESUMO

Copper(II) binding to prion peptides does not prevent Cu redox cycling and formation of reactive oxygen species (ROS) in the presence of reducing agents. The toxic effects of these species are exacerbated in the presence of catecholamines, indicating that dysfunction of catecholamine vesicular sequestration or recovery after synaptic release is a dangerous amplifier of Cu induced oxidative stress. Cu bound to prion peptides including the high affinity site involving histidines adjacent to the octarepeats exhibits marked catalytic activity toward dopamine and 4-methylcatechol. The resulting quinone oxidation products undergo parallel oligomerization and endogenous peptide modification yielding catechol adducts at the histidine binding ligands. These modifications add to the more common oxidation of Met and His residues produced by ROS. Derivatization of Cu-prion peptides is much faster than that undergone by Cu-ß-amyloid and Cu-α-synuclein complexes in the same conditions.


Assuntos
Cobre/química , Estresse Oxidativo , Proteínas Priônicas/química , Catálise , Catecóis/química , Cobre/farmacologia , Peróxido de Hidrogênio/química , Cinética , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Superóxido Dismutase/metabolismo
6.
Chemistry ; 22(49): 17767-17775, 2016 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-27759905

RESUMO

Many biochemical pathways involving nerve growth factor (NGF), a neurotrophin with copper(II) binding abilities, are regulated by the ubiquitin (Ub) proteasome system. However, whether NGF binds Ub and the role played by copper(II) ions in modulating their interactions have not yet been investigated. Herein NMR spectroscopy, circular dichroism, ESI-MS, and titration calorimetry are employed to characterize the interactions of NGF with Ub. NGF1-14 , which is a short model peptide encompassing the first 14 N-terminal residues of NGF, binds the copper-binding regions of Ub (KD =8.6 10-5 m). Moreover, the peptide undergoes a random coil-polyproline type II helix structural conversion upon binding to Ub. Notably, copper(II) ions inhibit NGF1-14 /Ub interactions. Further experiments performed with the full-length NGF confirmed the existence of a copper(II)-dependent association between Ub and NGF and indicated that the N-terminal domain of NGF was a valuable paradigm that recapitulated many traits of the full-length protein.


Assuntos
Cobre/química , Fator de Crescimento Neural/química , Peptídeos/química , Ubiquitina/química , Dicroísmo Circular , Humanos , Íons , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Ligação Proteica
7.
Chemistry ; 21(10): 4071-84, 2015 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-25649151

RESUMO

Prion diseases are a group of neurodegenerative diseases based on the conformational conversion of the normal form of the prion protein (PrP(C)) to the disease-related scrapie isoform (PrP(Sc)). Copper(II) coordination to PrP(C) has attracted considerable interest for almost 20 years, mainly due to the possibility that such an interaction would be an important event for the physiological function of PrP(C). In this work, we report the copper(II) coordination features of the peptide fragment Ac(PEG11)3PrP(60-114) [Ac = acetyl] as a model for the whole N-terminus of the PrP(C) metal-binding domain. We studied the complexation properties of the peptide by means of potentiometric, UV/Vis, circular dichroism and electrospray ionisation mass spectrometry techniques. The results revealed that the preferred histidyl binding sites largely depend on the pH and copper(II)/peptide ratio. Formation of macrochelate species occurs up to a 2:1 metal/peptide ratio in the physiological pH range and simultaneously involves the histidyl residues present both inside and outside the octarepeat domain. However, at increased copper(II)/peptide ratios amide-bound species form, especially within the octarepeat domain. On the contrary, at basic pH the amide-bound species predominate at any copper/peptide ratio and are formed preferably with the binding sites of His96 and His111, which is similar to the metal-binding-affinity order observed in our previous studies.


Assuntos
Histamina/química , Peptídeos/química , Príons/química , Dicroísmo Circular , Cobre/química , Espectrometria de Massas , Ligação Proteica , Raios Ultravioleta
8.
Chemistry ; 19(11): 3751-61, 2013 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-23355367

RESUMO

Characterization of the copper(II) complexes formed with the tetraoctarepeat peptide at low and high metal-to-ligand ratios and in a large pH range, would provide a breakthrough in the interpretation of biological relevance of the different metal complexes of copper(II)-tetraoctarepeat system. In the present work, the potentiometric, UV/Vis, circular dichroism (CD), and electron paramagnetic resonance (EPR) studies were carried out on copper(II) complexes with a PEG-ylated derivative of the tetraoctarepeats peptide sequence (Ac-PEG27 -(PHGGGWGQ)4 -NH2 ) and the peptide Ac-(PHGGGWGQ)2 -NH2 . Conjugation of tetraoctarepeat peptide sequence with polyethyleneglycol improved the solubility of the copper(II) complexes. The results enable a straightforward explanation of the conflicting results originated from the underestimation of all metal-ligand equilibria and the ensuing speciation. A complete and reliable speciation is therefore obtained with the released affinity and binding details of the main complexes species formed in aqueous solution. The results contribute to clarify the discrepancies of several studies in which the authors ascribe the redox activity of copper(II)-tetraoctarepeat system considering only the average effects of several coexisting species with very different stoichiometries and binding modes.


Assuntos
Cobre/química , Compostos Organometálicos/química , Príons/química , Compostos Organometálicos/síntese química , Príons/síntese química , Soluções , Espectrometria de Massas por Ionização por Electrospray , Água/química
9.
ACS Chem Neurosci ; 14(6): 1126-1136, 2023 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-36857606

RESUMO

Alzheimer's disease (AD) is the most common cause of dementia, characterized by a spectrum of symptoms associated with memory loss and cognitive decline with deleterious consequences in everyday life. The lack of specific drugs for the treatment and/or prevention of this pathology makes AD an ever-increasing economic and social emergency. Oligomeric species of amyloid-beta (Aß) are recognized as the primary cause responsible for synaptic dysfunction and neuronal degeneration, playing a crucial role in the onset of the pathology. Several studies have been focusing on the use of small molecules and peptides targeting oligomeric species to prevent Aß aggregation and toxicity. Among them, peptide fragments derived from the primary sequence of Aß have also been used to exploit any eventual recognition abilities toward the full-length Aß parent peptide. Here, we test the Aß8-20 fragment which contains the self-recognizing Lys-Leu-Val-Phe-Phe sequence and lacks Arg 5 and Asp 7 and the main part of the C-terminus, key points involved in the aggregation pathway and stabilization of the fibrillary structure of Aß. In particular, by combining chemical and biological techniques, we show that Aß8-20 does not undergo random coil to ß sheet conformational transition, does not form amyloid fibrils by itself, and is not toxic for neuronal cells. Moreover, we demonstrate that Aß8-20 mainly interacts with the 4-11 region of Aß1-42 and inhibits the formation of toxic oligomeric species and Aß fibrils. Finally, our data show that Aß8-20 protects neuron-like cells from Aß1-42 oligomer toxicity. We propose Aß8-20 as a promising drug candidate for the treatment of AD.


Assuntos
Doença de Alzheimer , Fármacos Neuroprotetores , Humanos , Doença de Alzheimer/metabolismo , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Peptídeos beta-Amiloides/metabolismo , Fragmentos de Peptídeos/metabolismo , Amiloide/metabolismo
10.
J Colloid Interface Sci ; 613: 814-826, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35074707

RESUMO

Recognition and capture of amyloid beta (Aß) is a challenging task for the early diagnosis of neurodegenerative disorders, such as Alzheimer's disease. Here, we report a novel KLVFF-modified nanomagnet based on magnetic nanoparticles (MNP) covered with a non-ionic amphiphilic ß-cyclodextrin (SC16OH) and decorated with KLVFF oligopeptide for the self-recognition of the homologous amino-acids sequence of Aß to collect Aß (1-42) peptide from aqueous samples. MNP@SC16OH and MNP@SC16OH/Ada-Pep nanoassemblies were fully characterized by complementary techniques both as solid powders and in aqueous dispersions. Single domain MNP@SC16OH/Ada-Pep nanomagnets of 20-40 nm were observed by TEM analysis. DLS and ζ-potential measurements revealed that MNP@SC16OH nanoassemblies owned in aqueous dispersion a hydrodynamic radius of about 150 nm, which was unaffected by Ada-Pep decoration, while the negative ζ-potential of MNP@SC16OH (-40 mV) became less negative (-30 mV) in MNP@SC16OH/Ada-Pep, confirming the exposition of positively charged KLVFF on nanomagnets surface. The ability of MNP@SC16OH/Ada-Pep to recruit Aß (1-42) in aqueous solution was evaluated by MALDI-TOF and compared with the ineffectiveness of undecorated MNP@SC16OH and VFLKF scrambled peptide-decorated nanoassemblies (MNP@SC16OH/Ada-scPep), pointing out the selectivity of KLVFF-decorated nanohybrid towards Aß (1-42). Finally, the property of nanomagnets to extract Aß in conditioned medium of cells over-producing Aß peptides was investigated as proof of concept of effectiveness of these nanomaterials as potential diagnostic tools.


Assuntos
Peptídeos beta-Amiloides , Ciclodextrinas , Oligopeptídeos , Fragmentos de Peptídeos
11.
Chem Phys Lipids ; 237: 105085, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33895131

RESUMO

Currently, Alzheimer's Disease (AD) is a complex neurodegenerative condition, with limited therapeutic options. Several factors, like Amyloid ß (Aß) aggregation, tau protein hyperphosphorylation, bio-metals dyshomeostasis and oxidative stress contribute to AD pathogenesis. These pathogenic processes might occur in the aqueous phase but also on neuronal membranes. Thus, investigating the connection between Aß and biomembranes, becomes important for unveiling the molecular mechanism underlying Aß amyloidosis as a critical event in AD pathology. In this work, the interaction of two peptides, made up with hybrid sequences from Tau protein 9-16 (EVMEDHAG) or 26-33 (QGGYTMHQ) N-terminal domain and Aß16-20 (KLVFF) hydrophobic region, with full length Aß40 or Aß42 peptides is reported. The studied "chimera" peptides Ac-EVMEDHAGKLVFF-NH2 (τ9-16-KL) and Ac-QGGYTMHQKLVFF-NH2 (τ26-33-KL) are endowed with Aß recognition and metal ion interaction capabilities provided by the tau or Aß sequences, respectively. These peptides were characterized in previous study along with their metal dependent interaction and amyloidogenesis, either in the presence or absence of metal ion and artificial membranes made up with Total Lipid Brain Extract (TLBE) components, (Sciacca et al., 2020). In the present paper, the ability of the two peptides to inhibit Aß aggregation is studied using composite experimental conditions including aqueous solution, the presence of metal ions (Cu or Zn), the presence of lipid vesicles mimicking neuronal membranes as well as the co-presence of metals and TLBE artificial membranes. We used Thioflavine-T (ThT) fluorescence or MALDI-TOF spectrometry analysis of Aß limited proteolysis to respectively monitor the Aß aggregation kinetic or validation of the Aß interacting regions. We demonstrate that τ9-16-KL and τ26-33-KL peptides differently affect Aß aggregation kinetics, with the tau sequence playing a crucial role. The results are discussed in terms of chimera's peptides hydrophobicity and electrostatic driven interactions at the aqueous/membrane interface.


Assuntos
Peptídeos beta-Amiloides/química , Cobre/química , Fragmentos de Peptídeos/química , Peptídeos/química , Agregados Proteicos/fisiologia , Lipossomas Unilamelares/química , Zinco/química , Proteínas tau/química , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Humanos , Cinética , Peptídeos/metabolismo , Espectrometria de Fluorescência , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
12.
J Inorg Biochem ; 217: 111358, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33588277

RESUMO

The copper(II) complexes of a peptide fragment of the R3 domain of tau protein (tau(326-333) Ac-GNIHHKPG-NH2) and its mutants (Ac-GNGHHKPG-NH2, Ac-GNIHHKAG-NH2, Ac-GNGAHKPG-NH2 and Ac-GNGHAKPG-NH2) have been studied by potentiometric and spectroscopic (UV-Vis, CD) methods. ESR spectroscopy and mass spectrometry were also used to prove the coordination mode of the mononuclear complexes and the formation of dinuclear species, respectively. It has been demonstrated that the (326-333) fragment of tau protein is a versatile and effective ligand for copper(II) coordination. The versatility of copper(II) binding is related to the presence of two adjacent histidyl residues in the sequence, which results in the coexistence of mononuclear, bis(ligand) and dinuclear complexes at different metal to ligand ratios. The 1:1 mononuclear complexes are, however, the dominant species with all peptides and the imidazole-N and one to three deprotonated amide nitrogen atoms towards the N-terminal side of the histidyl residue have been suggested as metal binding sites. This binding mode allows the formation of coordination isomers because any of the two histidine moieties can be the primary anchoring site. It is evident from the CD spectroscopic measurements that the isomers are present in almost equal concentration. The copper(II) binding affinity of the native fragment of tau protein is comparable to that of a similar 2-histidine fragment of amyloid-ß mutant, Ac-SGAEGHHQK-NH2 but the comparison with an independent histidyl residue (H32) from the N-terminal region of the protein reveals the predominance of H32 over the histidines in the R3 domain.


Assuntos
Complexos de Coordenação/química , Cobre/metabolismo , Fragmentos de Peptídeos/metabolismo , Proteínas tau/metabolismo , Sítios de Ligação , Dicroísmo Circular , Cobre/química , Técnicas Eletroquímicas , Espectroscopia de Ressonância de Spin Eletrônica , Fragmentos de Peptídeos/química , Ligação Proteica , Domínios Proteicos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Proteínas tau/química
13.
ACS Chem Neurosci ; 12(8): 1449-1462, 2021 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-33844495

RESUMO

Alzheimer's disease (AD) is a progressive neurodegenerative condition affecting people in the elderly. Targeting aggregation of ß-amyloid peptides (Aß) is considered a promising approach for the therapeutic treatment of the disease. Peptide based inhibitors of ß-amyloid fibrillation are emerging as safe drug candidates as well as interesting compounds for early diagnosis of AD. Peptide conjugation via covalent bond with functional moieties enables the resultant hybrid system to acquire desired functions. Here we report the synthesis, the structural characterization, and the Aß42 interaction of a p-amino-calix[4]arene derivative bearing a GPGKLVFF peptide pendant at the lower rim. We demonstrate that the p-amino-calix[4]arene-GPGKLVFF conjugate alters the Aß42 aggregation pathways by preventing Aß42's conformational transition from random coil to ß-sheet with concomitant changes of the aggregation kinetic profile as evidenced by circular dichroism (CD), thioflavin T (ThT), and dynamic light scattering (DLS) measurements, respectively. High resolution mass spectrometry (HR-MS) confirmed a direct interaction of the p-amino-calix[4]arene-GPGKLVFF conjugate with Aß42 monomer which provided insight into a possible working mechanism, whereas the alteration of the Aß42's fibrillary architecture, by the calix-peptide conjugate, was further validated by atomic force microscopy (AFM) imaging. Finally, the herein proposed compound was shown to be effective against Aß42 oligomers' toxicity in differentiated neuroblastoma cells, SH-SY5Y.


Assuntos
Doença de Alzheimer , Fragmentos de Peptídeos , Idoso , Peptídeos beta-Amiloides , Calixarenos , Humanos , Neurônios , Fenóis
14.
J Inorg Biochem ; 205: 110996, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31954342

RESUMO

Several abnormal events may concur as major risk factors for Alzheimer's disease (AD) pathogenesis. For instance, dysregulation of brain's metal homeostasis and amyloid-mediated membrane damage are established toxic mechanisms causing neuronal death. In this study, we assess the amyloidogenic propensity and membrane-damage effects, either in the presence or in absence of metal ions, of two newly synthesized bifunctional peptides. These were designed to comprise a metal chelating N-terminus region derived from Tau protein namely the Tau9-16 (EVMEDHAG) or Tau26-33 (QGGYTMHQ) sequences, merged with the C-terminal hydrophobic region analogous to the Amyloid beta (Aß) 16-20 aminoacid sequence KLVFF (KL). Comparative circular dichroism or fluorescence experiments were carried out to look at the peptide conformation, fibril formation and membrane affinity of Tau9-16KL and Tau26-33KL peptides. We found that Tau9-16KL and Tau26-33KL perturb the fibrillogenic process of Aß1-40. Furthermore Cu(II) and, to a lower extent, Zn(II) induced conformational changes Tau26-33KL both in water and in membrane-mimicking environment. By contrast, due to a different metal coordination mode we observed for Tau9-16KL an unstructured peptide conformation in all the experimental conditions. Unlike aqueous solution, a certain propensity to form amyloid structures at the lipid membrane interface clearly emerged for both the peptides. However, the two peptides exhibit a different capability to elicit membrane damage depending on the presence or absence of metal ions. Tau9-16KL and Tau26-33KL can be used as peptide-based molecular systems able to interfere with the metal dependent Aß/Tau cross-seeded generation of membrane active amyloid species.


Assuntos
Peptídeos beta-Amiloides/química , Complexos de Coordenação/química , Cobre/química , Membranas Artificiais , Zinco/química , Proteínas tau/química , Humanos
15.
Inorg Chem ; 48(9): 4239-50, 2009 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-19348438

RESUMO

Complex formation processes between the 39-mer residue peptide fragment of human prion protein, HuPrP(76-114), and copper(II) ions have been studied by potentiometric, UV-vis, circular dichroism (CD), electron paramagnetic resonance, and electrospray ionization mass spectrometry methods. This peptide consists of 39 amino acid residues and contains two histidines (His77 and His85) belonging to the octarepeat domain and two histidines (His96 and His111) outside this domain. It was found that HuPrP(76-114) is able to bind 4 equiv of metal ions and all histidyl residues are independent, except nonequivalent metal binding sites in the oligonuclear species. Imidazole nitrogen donor atoms are the primary and exclusive metal binding sites below pH 5.5 in the form of various macrochelates. The macrochelation slightly suppresses, but cannot prevent, the deprotonation and metal ion coordination of amide functions, resulting in the formation of (N(im),N(-)), (N(im),N(-),N(-)), and (N(im),N(-),N(-),N(-))-coordinated copper(II) complexes in the pH range from 5.5 to 9. CD spectroscopy results gave clear evidence for the differences in the metal binding affinity of the histidyl sites according to the following order: His111 > His96 >> His77 approximately His85. Among the oligonuclear complexes, the formation of di- and tetranuclear species seems to be favored over the trinuclear ones, at pH values beyond the physiological ones. This phenomenon was not observed in the complex formation reactions of HuPrP(84-114), a peptide fragment containing only one histidyl residue from the octarepeat. As a consequence, the data support the existence of cooperativity in the metal binding ability of this peptide probably due to the presence of two octarepeat sequences of the dimeric octarepeat domain of HuPrP(76-114) at basic pH values.


Assuntos
Cobre/metabolismo , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Príons/química , Príons/metabolismo , Sítios de Ligação , Cobre/química , Histidina/química , Histidina/metabolismo , Humanos , Potenciometria , Ligação Proteica , Conformação Proteica , Estrutura Terciária de Proteína , Prótons , Análise Espectral , Termodinâmica
16.
Chempluschem ; 84(11): 1697-1708, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31943878

RESUMO

Copper(II) complexes of the N-terminal peptide fragments of tau protein have been studied by potentiometric and various spectroscopic techniques (UV-vis, CD, ESR and ESI-MS). The octapeptide Tau(9-16) (Ac-EVMEDHAG-NH2 ) contains the H14 residue of the native protein, while Tau(26-33) (Ac-QGGYTMHQ-NH2 ) and its mutants Tau(Q26K-Q33K) (Ac-KGGYTMHK-NH2 ) and Tau(Q26K-Y29A-Q33K) (Ac-KGGATMHK-NH2 ) include the H32 residue. To compare the binding ability of H14 and H32 in a single molecule the decapeptide Ac-EDHAGTMHQD-NH2 (Tau(12-16)(30-34)) has also been synthesized and studied. The histidyl residue is the primary metal binding site for metal ions in all the peptide models studied. In the case of Tau(9-16) the side chain carboxylate functions enhance the stability of the M-Nim coordinated complexes compared to Tau(26-33) (logK(Cu-Nim )=5.04 and 3.78, respectively). Deprotonation and metal ion coordination of amide groups occur around the physiological pH range for copper(II). The formation of the imidazole- and amide-coordinated species changes the metal ion preference and the complexes formed with the peptides containing the H32 residue predominate over those of H14 at physiological pH values (90 %-10 %) and in alkaline samples (96 %-4 %).


Assuntos
Complexos de Coordenação/química , Cobre/química , Fragmentos de Peptídeos/química , Proteínas tau/química , Sequência de Aminoácidos , Sítios de Ligação , Espectrometria de Massas , Potenciometria
17.
Curr Med Chem ; 25(4): 525-539, 2018 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-28521682

RESUMO

BACKGROUND: There is mounting urgency to find new drugs for the treatment of neurodegenerative disorders. A large number of reviews have exhaustively described either the molecular or clinical aspects of neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's (PD). Conversely, reports outlining how known drugs in use for other diseases can also be effective as therapeutic agents in neurodegenerative diseases are less reported. This review focuses on the current uses of some copper(II) chelating molecules as potential drug candidates in neurodegeneration. METHODS: Starting from the well-known harmful relationships existing between the dyshomeostasis and mis-management of metals and AD onset, we surveyed the experimental work reported in the literature, which deals with the repositioning of metal-chelating drugs in the field of neurodegenerative diseases. The reviewed papers were retrieved from common literature and their selection was limited to those describing the biomolecular aspects associated with neuroprotection. In particular, we emphasized the copper(II) coordination abilities of the selected drugs. RESULTS: Copper, together with zinc and iron, are known to play a key role in regulating neuronal functions. Changes in copper homeostasis are crucial for several neurodegenerative disorders. The studies included in this review may provide an overview on the current strategies aimed at repurposing copper (II) chelating drugs for the treatment of neurodegenerative disorders. Starting from the exemplary case of clioquinol repurposing, we discuss the challenge and the opportunities that repurposing of other metal-chelating drugs may provide (e.g. PBT-2, metformin and cyclodipeptides) in the treatment of neurodegenerative disease. CONCLUSIONS: In order to improve the success rate of drug repositioning, comprehensive studies on the molecular mechanism and therapeutic efficacy are still required. The present review upholds that drug repurposing makes significant advantages over drug discovery since repositioned drugs had already passed the safety and toxicity tests. Promising drug candidates in neurodegenerative diseases may be represented by copper chelating classes of drugs, provided that sufficient details on their mechanism of action are available to encourage further investigations and clinical trials.


Assuntos
Quelantes/farmacologia , Cobre/química , Doenças Neurodegenerativas/tratamento farmacológico , Fármacos do Sistema Nervoso Central/química , Fármacos do Sistema Nervoso Central/farmacologia , Quelantes/química , Reposicionamento de Medicamentos , Humanos
18.
Eur J Med Chem ; 138: 115-127, 2017 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-28651154

RESUMO

The gold(III)-dithiocarbamate complex AuL12 (dibromo [ethyl-N-(dithiocarboxy-kS,kS')-N-methylglycinate] gold(III)), is endowed with promising in vitro/in vivo antitumor activity and toxicological profile. Here, we report our recent strategies to improve its water solubility and stability under physiological conditions along with our efforts for unravelling its tangled mechanism of action. We used three types of α-cyclodextrins (CDs), namely ß-CD, Me-ß-CD and HP-ß-CD to prepare aqueous solutions of AuL12. The ability of these natural oligosaccharide carriers to enhance water solubility of hydrophobic compounds, allowed drug stability of AuL12 to be investigated. Moreover, pharmacokinetic experiments were first carried out for a gold(III) coordination compound, after i.v. injection of the nanoformulation AuL12/HP-ß-CD to female mice. The gold content in the blood samples was detected at scheduled times by AAS (atomic absorption spectrometry) analysis, highlighting a fast biodistribution with a tß1/2 of few minutes and a slow escretion (tα1/2 of 14.3 h). The in vitro cytotoxic activity of AuL12 was compared with the AuL12/HP-ß-CD mixture against a panel of three human tumor cell lines (i.e., HeLa, KB and MCF7). Concerning the mechanism of action, we previously reported the proteasome-inhibitory activity of some our gold(III)-based compounds. In this work, we moved from the proteasome target to upstream of the important ubiquitin-proteasome pathway, testing the effects of AuL12 on the polyubiquitination reactions involving the Ub-activating (E1) and -conjugating (E2) enzymes.


Assuntos
Antineoplásicos/farmacologia , Ciclodextrinas/química , Ouro/farmacologia , Complexo de Endopeptidases do Proteassoma/metabolismo , Tiocarbamatos/farmacologia , Ubiquitina/antagonistas & inibidores , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Feminino , Ouro/química , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Estrutura Molecular , Solubilidade , Relação Estrutura-Atividade , Tiocarbamatos/química , Distribuição Tecidual , Células Tumorais Cultivadas , Ubiquitina/metabolismo , Água/química
19.
J Inorg Biochem ; 100(8): 1399-409, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16730799

RESUMO

Histidine-containing peptide fragments of prion protein are efficient ligands to bind various transition metal ions and they have high selectivity in metal binding. The metal ion affinity follows the order: Pd(II)>>Cu(II)>>Ni(II)Zn(II)>Cd(II) approximately Co(II)>Mn(II). The high selectivity of metal binding is connected to the involvement of both imidazole and amide nitrogen atoms in metal binding for Pd(II), Cu(II) and Ni(II), while only the monodentate N(im)-coordination is possible with the other metal ions. The stoichiometry and binding mode of palladium(II) complexes show great variety depending on the metal ion to ligand ratio, pH and especially the presence of coordinating donor atoms in the side chains of peptide fragments. It is also clear from our data that the peptide fragments containing histidine outside the octarepeat (His96, His111 and His187) are more efficient ligands than the monomer peptide fragments of the octarepeat domain.


Assuntos
Histidina/química , Compostos Organometálicos/química , Peptídeos/química , Elementos de Transição/química , Animais , Galinhas , Humanos , Compostos Organometálicos/metabolismo , Peptídeos/metabolismo , Príons/química , Príons/metabolismo , Elementos de Transição/metabolismo
20.
World J Gastroenterol ; 20(28): 9374-83, 2014 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-25071332

RESUMO

Pancreatic cancer (PC) is the fourth cause of cancer death in Western countries, the only chance for long term survival is an R0 surgical resection that is feasible in about 10%-20% of all cases. Five years cumulative survival is less than 5% and rises to 25% for radically resected patients. About 40% has locally advanced in PC either borderline resectable (BRPC) or unresectable locally advanced (LAPC). Since LAPC and BRPC have been recognized as a particular form of PC neoadjuvant therapy (NT) has increasingly became a valid treatment option. The aim of NT is to reach local control of disease but, also, it is recognized to convert about 40% of LAPC patients to R0 resectability, thus providing a significant improvement of prognosis for responding patients. Once R0 resection is achieved, survival is comparable to that of early stage PCs treated by upfront surgery. Thus it is crucial to look for a proper patient selection. Neoadjuvant strategies are multiples and include neoadjuvant chemotherapy (nCT), and the association of nCT with radiotherapy (nCRT) given as either a combination of a radio sensitizing drug as gemcitabine or capecitabine or and concomitant irradiation or as upfront nCT followed by nRT associated to a radio sensitizing drug. This latter seem to be most promising as it may select patients who do not go on disease progression during initial treatment and seem to have a better prognosis. The clinical relevance of nCRT may be enhanced by the application of higher active protocols as FOLFIRINOX.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Terapia Neoadjuvante/métodos , Pancreatectomia , Neoplasias Pancreáticas/terapia , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Quimiorradioterapia Adjuvante , Quimioterapia Adjuvante , Humanos , Terapia Neoadjuvante/efeitos adversos , Terapia Neoadjuvante/mortalidade , Estadiamento de Neoplasias , Pancreatectomia/efeitos adversos , Pancreatectomia/mortalidade , Neoplasias Pancreáticas/mortalidade , Neoplasias Pancreáticas/patologia , Seleção de Pacientes , Radioterapia Adjuvante , Fatores de Risco , Fatores de Tempo , Resultado do Tratamento
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