DSpace Angular :: Browsing by Author "Barrera, Nelson P."

Browsing by Author "Barrera, Nelson P."

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Antibacterial Effect of Honey-Derived Exosomes Containing Antimicrobial Peptides Against Oral Streptococci
(2021) Leiva-Sabadini, Camila ; Alvarez, Simon ; Barrera, Nelson P.; Schuh, Christina M.A.P. ; Aguayo, Sebastian
Purpose: Recently, our group found exosome-like extracellular vesicles (EVs) in Apis mellifera honey displaying strong antibacterial effects; however, the underlying mechanism is still not understood. Thus, the aim of this investigation was to characterize the molecular and nanomechanical properties of A. mellifera honey-derived EVs in order to elucidate the mechanisms behind their antibacterial effect, as well as to determine differential antibiofilm properties against relevant oral streptococci.
ATP and adenosine trigger the interaction of plasma membrane IP₃ receptors with protein kinase A in oviductal ciliated cells
(2007) Barrera, Nelson P.; Morales, Bernardo; Villalon, Manuel
We have demonstrated that adenosine did not produce any change of intracellular free Ca2+ concentration ([Ca2+]i) in oviductal ciliated cells; however, it increased the ATP-induced Ca2+ influx through the activation of protein kinase A (PKA). Uncaging Of IP3 and cAMP triggered a larger Ca2+ influx than did IP3 alone. Furthermore, the IP3 effect was abolished by Xestospongin C, an IP3 receptor blocker. Whole-cell recordings demonstrated the presence of an ATP-induced Ca2+ current, and the addition of adenosine increased the peak of this current. This effect was not observed in the presence of H-89, a PKA inhibitor. Using excised macro-patches of plasma membrane, IP3 generated a current, which was higher in the presence of the catalytic PKA subunit and this current was blocked by Xestospongin C. We show here that activation of plasma membrane IP3 receptors directly triggers Ca2+ influx in response to ATP and that these receptors are modulated by adenosine-activated PKA. (C) 2007 Elsevier Inc. All rights reserved.
Crosstalking interactions between P2X4 and 5-HT3A receptors
(2023) Chang-Halabi, Yuan; Cordero, Jose; Sarabia, Xander; Villalobos, Daniela; Barrera, Nelson P.
Ionotropic receptors are ligand-gated ion channels triggering fast neurotransmitter responses. Among them, P2X and 5-HT3 receptors have been shown to physically interact each other and functionally inducing cross inhibitory responses. Nevertheless, despite the importance of P2X4 and 5-HT3A receptors that mediate for example neuropathic pain and psychosis respectively, complementary evidence has recently started to move forward in the understanding of this interaction. In this review, we discuss current evidence supporting the mechanism of crosstalking between both receptors, from the structural to the transduction pathway level. We expect this work may guide the design of further experiments to obtain a comprehensive view for the neuropharmacological role of these interacting receptors.This article is part of the Special Issue on "The receptor-receptor interaction as a new target for therapy".
Drug-dependent inhibition of nucleotide hydrolysis in the heterodimeric ABC multidrug transporter PatAB from Streptococcus pneumoniae
(2022) Guffick, Charlotte; Hsieh, Pei-Yu; Ali, Anam; Shi, Wilma; Howard, Julie; Chinthapalli, Dinesh K.; Kong, Alex C.; Salaa, Ihsene; Crouch, Lucy, I; Ansbro, Megan R.; Isaacson, Shoshanna C.; Singh, Himansha; Barrera, Nelson P.; Nair, Asha, V; Robinson, Carol, V; Deery, Michael J.; van Veen, Hendrik W.
The bacterial heterodimeric ATP-binding cassette (ABC) multidrug exporter PatAB has a critical role in conferring antibiotic resistance in multidrug-resistant infections by Streptococcus pneumoniae. As with other heterodimeric ABC exporters, PatAB contains two transmembrane domains that form a drug translocation pathway for efflux and two nucleotide-binding domains that bind ATP, one of which is hydrolysed during transport. The structural and functional elements in heterodimeric ABC multidrug exporters that determine interactions with drugs and couple drug binding to nucleotide hydrolysis are not fully understood. Here, we used mass spectrometry techniques to determine the subunit stoichiometry in PatAB in our lactococcal expression system and investigate locations of drug binding using the fluorescent drug-mimetic azido-ethidium. Surprisingly, our analyses of azido-ethidium-labelled PatAB peptides point to ethidium binding in the PatA nucleotide-binding domain, with the azido moiety crosslinked to residue Q521 in the H-like loop of the degenerate nucleotide-binding site. Investigation into this compound and residue's role in nucleotide hydrolysis pointed to a reduction in the activity for a Q521A mutant and ethidium-dependent inhibition in both mutant and wild type. Most transported drugs did not stimulate or inhibit nucleotide hydrolysis of PatAB in detergent solution or lipidic nanodiscs. However, further examples for ethidium-like inhibition were found with propidium, novobiocin and coumermycin A1, which all inhibit nucleotide hydrolysis by a non-competitive mechanism. These data cast light on potential mechanisms by which drugs can regulate nucleotide hydrolysis by PatAB, which might involve a novel drug binding site near the nucleotide-binding domains.
Fractional Factorial Design to Evaluate the Synthesis and Electrochemical Transfer Parameters of h-BN Coatings
(2023) Figueroa, Helen; Aristizabal, Juliet; Reinoso-Guerra, Elias; Arce, Barbara; Vargas-Straube, Maria Jose; Gentil, Dana; Ramirez, Cristian; Cordero, Jose; Barrera, Nelson P.; Parra, Carolina
In this study, we present a fractional factorial design approach for exploring the effects and interactions of key synthesis and electrochemical transfer parameters on the roughness and wettability of hexagonal boron nitride (h-BN) coatings, due to their essential role in biofilm formation. The studied parameters for the synthesis process include precursor mass, growth time, and substrate conditioning, whereas for the transfer process, applied voltage and aqueous medium concentration were studied. Through this polynomial model, we confirmed the strong influence of precursor mass and medium concentration parameters on h-BN surface roughness and its resulting antibiofilm properties.
How far are we from predicting multi-drug interactions during treatment for COVID-19 infection?
(WILEY, 2022) Lozano, Benjamin; Santibanez, Javier; Severino, Nicolas; Saldias, Cristina; Vera, Magdalena; Retamal, Jaime; Torres, Soledad; Barrera, Nelson P.
Seriously ill patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hospitalized in intensive care units (ICUs) are commonly given a combination of drugs, a process known as multi-drug treatment. After extracting data on drug-drug interactions with clinical relevance from available online platforms, we hypothesize that an overall interaction map can be generated for all drugs administered. Furthermore, by combining this approach with simulations of cellular biochemical pathways, we may be able to explain the general clinical outcome. Finally, we postulate that by applying this strategy retrospectively to a cohort of patients hospitalized in ICU, a prediction of the timing of developing acute kidney injury (AKI) could be made. Whether or not this approach can be extended to other diseases is uncertain. Still, we believe it represents a valuable pharmacological insight to help improve clinical outcomes for severely ill patients.
Mass Spectrometry-From Peripheral Proteins to Membrane Motors
(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2012) Morgner, Nina; Montenegro, Felipe; Barrera, Nelson P.; Robinson, Carol V.
That membrane protein complexes could survive in the gas phase had always seemed impossible. The lack of chargeable residues, high hydrophobicity, and poor solubility and the vast excess of detergent contributed to the view that it would not be possible to obtain mass spectra of intact membrane complexes. With the recent success in recording mass spectra of these complexes, first from recombinant sources and later from the cellular environment, many surprising properties of these gas phase membrane complexes have been revealed. The first of these was that the interactions between membrane and soluble subunits could survive in vacuum, without detergent molecules adhering to the complex. The second unexpected feature was that their hydrophobicity and, consequently, lower charge state did not preclude ionization. The final surprising finding was that these gas phase membrane complexes carry with them lipids, bound specifically in subunit interfaces. This provides us with an opportunity to distinguish annular lipids that surround the membrane complexes, from structural lipids that have a role in maintaining structure and subunit interactions. In this perspective, we track these developments and suggest explanations for the various discoveries made during this research. (c) 2012 Elsevier Ltd. All rights reserved.
Polydisperse molecular architecture of connexin 26/30 heteromeric hemichannels revealed by atomic force microscopy imaging
(2020) Naulin, Pamela A.; Lozano, Benjamin; Fuentes, Christian; Liu, Yu; Schmidt, Carla; Contreras, Jorge E.; Barrera, Nelson P.
Connexin (Cx) protein forms hemichannels and gap junctional channels, which play diverse and profound roles in human physiology and diseases. Gap junctions are arrays of intercellular channels formed by the docking of two hemichannels from adjacent cells. Each hexameric hemichannel contains the same or different Cx isoform. Although homomeric Cxs forms have been largely described functionally and structurally, the stoichiometry and arrangement of heteromeric Cx channels remain unknown. The latter, however, are widely expressed in human tissues and variation might have important implications on channel function. Investigating properties of heteromeric Cx channels is challenging considering the high number of potential subunit arrangements and stoichiometries, even when only combining two Cx isoforms. To tackle this problem, we engineered an HA tag onto Cx26 or Cx30 subunits and imaged hemichannels that were liganded by Fab-epitope antibody fragments via atomic force microscopy. For Cx26-HA/Cx30 or Cx30-HA/Cx26 heteromeric channels, the Fab-HA binding distribution was binomial with a maximum of three Fab-HA bound. Furthermore, imaged Cx26/Cx30-HA triple liganded by Fab-HA showed multiple arrangements that can be derived from the law of total probabilities. Atomic force microscopy imaging of ringlike structures of Cx26/Cx30-HA hemichannels confirmed these findings and also detected a polydisperse distribution of stoichiometries. Our results indicate a dominant subunit stoichiometry of 3Cx26:3Cx30 with the most abundant subunit arrangement of Cx26-Cx26-Cx30-Cx26-Cx30-Cx30. To our knowledge, this is the first time that the molecular architecture of heteromeric Cx channels has been revealed, thus providing the basis to explore the functional effect of these channels in biology.
Royal Jelly Derived Extracellular Vesicles Modulate Microglial Nanomechanics and Inflammatory Responses
(2025) Zavala, Gabriela; Berríos, Pablo; Sandoval, Felipe; Bravo, Graciela; Barrera, Nelson P.; Alarcón Moyano, Jéssica; Díaz Calderón, Paulo; Aguayo, Sebastián; Schuh, Christina
BACKGROUND Microglia, the braińs resident immune cells, undergo profound mechanical and functional changes upon activation contributing to neuroinflammation, a pathological signature of many neurological diseases. Thus, new anti-inflammatory treatment options are needed that tackle these mechanobiological alterations in microglia, which remain strongly understudied. In this context, extracellular vesicles (EVs) are crucial mediators of intercellular and interkingdom communication, yet their influence on the mechanobiological properties of recipient cells remains largely unknown. Honeybee-derived Royal Jelly EVs (RJEVs) have demonstrated remarkable anti-inflammatory properties, but their impact on microglial cellular nanomechanics and uptake mechanisms remains unclear. RESULTS In this study, we used a multi-disciplinary approach to analyze the resulting biological and nanomechanical changes following the activation of human microglia and the potential effect of RJEV treatment on these mechanobiological parameters. We observed that LPS treatment was associated with decreased cellular Young’s modulus, increased membrane fluidity, and enhanced motility of microglia, indicating a more migratory and pro-inflammatory phenotype. Additionally, LPS exposure altered cellular EV uptake mechanisms by shifting preference from an equilibrium of four mechanisms to the predominance of macropinocytosis and clathrin-dependent endocytosis. Remarkably, RJEV treatment counteracted these mechanobiological changes by, in turn, increasing microglial stiffness, reducing motility, and decreasing secretion of pro-inflammatory cytokines. CONCLUSION This is the first study to demonstrate that microglial activation state dictates EV uptake mechanisms and to establish a direct link between inflammation, cellular and membrane mechanics, and EV-mediated modulation. Our findings highlight RJEVs as promising candidates for regulating neuroinflammation by targeting microglial mechanobiology as well as opening new strategies for EV-based therapeutics
Structural characterization of the saxitoxin-targeting APTSTX1 aptamer using optical tweezers and molecular dynamics simulations
(2019) Casanova-Morales, Nathalie; Figueroa, Nataniel L.; Alfaro, Karol; Montenegro, Felipe; Barrera, Nelson P.; Maze, J. R.; Wilson, Christian A. M.; Conejeros, Pablo
Optical tweezers have enabled the exploration of picoNewton forces and dynamics in single-molecule systems such as DNA and molecular motors. In this work, we used optical tweezers to study the folding/unfolding dynamics of the APTSTX1-aptamer, a single-stranded DNA molecule with high affinity for saxitoxin (STX), a lethal neurotoxin. By measuring the transition force during (un)folding processes, we were able to characterize and distinguish the conformational changes of this aptamer in the presence of magnesium ions and toxin. This work was supported by molecular dynamics (MD) simulations to propose an unfolding mechanism of the aptamer-Mg+2 complex. Our results are a step towards the development of new aptamer-based STX sensors that are potentially cheaper and more sensitive than current alternatives.
The Adsorption of P2X2 Receptors Interacting with IgG Antibodies Revealed by Combined AFM Imaging and Mechanical Simulation
(2024) Santander, Eduardo A.; Bravo, Graciela; Chang-Halabi, Yuan; Olguin-Orellana, Gabriel J.; Naulin, Pamela A.; Barrera, Mario J.; Montenegro, Felipe A.; Barrera, Nelson P.
The adsorption of proteins onto surfaces significantly impacts biomaterials, medical devices, and biological processes. This study aims to provide insights into the irreversible adsorption process of multiprotein complexes, particularly focusing on the interaction between anti-His6 IgG antibodies and the His6-tagged P2X2 receptor. Traditional approaches to understanding protein adsorption have centered around kinetic and thermodynamic models, often examining individual proteins and surface coverage, typically through Molecular Dynamics (MD) simulations. In this research, we introduce a computational approach employing Autodesk Maya 3D software for the investigation of multiprotein complexes' adsorption behavior. Utilizing Atomic Force Microscopy (AFM) imaging and Maya 3D-based mechanical simulations, our study yields real-time structural and kinetic observations. Our combined experimental and computational findings reveal that the P2X2 receptor-IgG antibody complex likely undergoes absorption in an 'extended' configuration. Whereas the P2X2 receptor is less adsorbed once is complexed to the IgG antibody compared to its individual state, the opposite is observed for the antibody. This insight enhances our understanding of the role of protein-protein interactions in the process of protein adsorption.

Browsing by Author "Barrera, Nelson P."

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