Biology subjects

Lopez, M. G.

Publications and source records attributed to Lopez, M. G..

8 recordsLinked to original sources

bioRxiv2025

Incorporation of ChiA into AcMNPV occlusion bodies and its implications for oral infectivity

Baculoviruses are insect-specific viruses primarily employed in biological pest control and recombinant protein expression. As biopesticides, they offer numerous advantages over chemical pesticides and hold significant potential for application in integrated pest management (IPM). However, their slower action compared to conventional synthetic strategies has limited their widespread adoption. This study aimed to investigate the impact of incorporating a viral protein, AcChiA chitinase, which disrupts the gut peritrophic membrane of susceptible insects, into AcMNPV occlusion bodies in trans. This was achieved through the development of an insect cell line that facilitates the passive incorporation of this protein. The presence of ChiA was detected in dissolved occlusion bodies (OBs) preparations from infected transgenic lines, in a method-dependent manner, with the stronger signals observed in chimeric polyhedra. It is hypothesized that ChiA in OBs will increase peritrophic membrane permeability and facilitate primary infection. In bioassays, OBs produced in ChiA-expressing lines were associated with higher larval mortality than OBs produced in Sf9, consistent with a ChiA-mediated effect. Notably, the addition of ChiA proteins from stably transformed insect cell lines improved infection rates, particularly in recombinant baculoviruses, which exhibited a significant reduction in occlusion-derived virion (ODV) occlusion. This underscores the critical role of these proteins in the oral infection process. Consequently, it was possible to incorporate the ChiA protein from stably transformed insect cell lines into wild-type and recombinant baculovirus occlusion bodies, paving the way for potential applications in IPM with AcMNPV.

bioengineering↗

bioRxiv2025

Complete genomes reveal the full extent of Mycobacterium tuberculosis complex diversity across evolutionary scales

Advances in short-read sequencing have enhanced our understanding of Mycobacterium tuberculosis complex (MTBC), but fail to capture its complete genomic diversity. We applied long-read sequencing to 216 isolates from the Valencia Region (Spain) and generated high-quality, complete genomes, revealing detailed insights into MTBC evolution across timescales. Complete genome comparisons increased the estimated evolutionary rate by 1.5-fold, resulting in a median of 312 (-1 to 792) additional SNPs per pairwise comparison. Multiple diversity hotspots were identified, mostly in the pe/ppe genes and driven by gene conversion. However, most PE/PPE epitopes were hyperconserved, with notable exceptions involving vaccine candidates. Incorporating previously undetected SNPs and indels improved resolution in transmission analyses. Furthermore, patient-specific reference mapping validates only 5-10% of within-host diversity detected by standard pipelines, indicating substantial overestimation in previous studies. These findings expand our view of MTBC diversity and have important implications for understanding host-pathogen interactions, epidemiology, and transmission dynamics.

genomics↗

bioRxiv2025

Long-term Nrf2-driven microglial repopulation mitigates microgliosis, neuronal loss and cognitive deficits in tauopathy

A prominent pathological feature of tauopathies, including Alzheimers disease, is a chronic microglial reactivity, which contributes to neuroinflammation and disease progression. Microglia, the innate immune cells of the brain, can be pharmacologically eliminated by inhibiting the colony stimulating factor 1 receptor (e.g. with PLX5622), which is essential for their survival and proliferation. Upon inhibitor withdrawal, microglia rapidly repopulate, replenishing the central nervous system niche with naive cells. In recent years, microglia repopulation strategies have gained great interest as a means to reprogram dysfunctional microglia, while avoiding the detrimental effects of prolonged immune depletion. Despite promising short-term results, the long-term efficacy and pharmacological modulation of repopulated microglial remain poorly understood. Here, we investigate whether repopulated microglia after PLX5622 treatment sustains their beneficial effects over time in an AAV-hTauP301L induced model. Additionally, we assessed whether activating the cytoprotective nuclear factor erythroid 2 p45-related factor 2 (Nrf2) during microglial repopulation enhanced and prolonged the therapeutic outcomes. While microglial repopulation alone failed to maintain its neuroprotection in the long-term, when combined with an Nrf2 inducer, it improved cognitive deficits, reverted hippocampal neuronal loss and restored microglial phenotypes and mitochondrial energetics homeostasis, in our tauopathy-induced model. These results highlight the importance of shaping the fate of self-renewed microglia and propose Nrf2-mediated microglia repopulation as a potential pharmacological strategy for the treatment of tauopathies. HIGHLIGHTSO_LINrf2 inducer ND523 boosts long-term repopulated microglia function in tauopathy. C_LIO_LIND523-mediated microglial repopulation mitigates tau-induced cognitive decline. C_LIO_LIND523-driven microglial repopulation reduces neuronal loss without altering p-tau. C_LIO_LIND523-microglial repopulation rescues microglial morphology and reduces reactivity. C_LIO_LIND523-mediated repopulation prevents mitochondrial energetics dysfunctions. C_LI

neuroscience↗

bioRxiv2024

The mitochondrial Na+/Ca2+ exchanger NCLX is implied in the activation of hypoxia-inducible factors

Eukaryotic cells and organisms depend on oxygen for basic living functions, and they display a panoply of adaptations to situations in which oxygen availability is diminished (hypoxia). A number of these responses in animals are mediated by changes in gene expression programs directed by hypoxia-inducible factors (HIFs), whose main mechanism of stabilization and functional activation in response to decreased cytosolic oxygen concentration was elucidated two decades ago. Human acute responses to hypoxia have been known for decades, although their precise molecular mechanism for oxygen sensing is not fully understood. It is already known that a redox component, linked with reactive oxygen species (ROS) production of mitochondrial origin, is implied in these responses. We have recently described a mechanism by which the mitochondrial sodium/calcium exchanger, NCLX, participates in mitochondrial electron transport chain regulation and ROS production in response to acute hypoxia. Here we show that NCLX is also implied in the response to hypoxia mediated by the HIFs. By using a NCLX inhibitor and interference RNA we show that NCLX activity is necessary for HIF- subunits stabilization in hypoxia and for HIF-1-dependent transcriptional activity. We also show that hypoxic mitochondrial ROS production is not required for HIF-1 stabilization under all circumstances, suggesting that other mechanism(s) could be operating in the NCLX-mediated response to hypoxia that operates through HIF- stabilization. This finding provides a link between acute and medium-term responses to hypoxia, reinforcing a central role of mitochondrial cell signalling in the response to hypoxia.

biochemistry↗

bioRxiv2021

Gene Evolutionary Trajectories in M. tuberculosis Reveal Temporal Signs of Selection

Genetic differences between different Mycobacterium tuberculosis complex (MTBC) strains determine their ability to transmit within different host populations, their latency times, and their drug-resistance profiles. Said differences usually emerge through de novo mutations and are maintained or discarded by the balance of evolutionary forces. Using a dataset of ~5,000 strains representing global MTBC diversity, we determined the past and present selective forces that have shaped the current variability observed in the pathogen population. We identified regions that have evolved under changing types of selection since the time of the MTBC common ancestor. Our approach highlighted striking differences in the genome regions relevant for host-pathogen interaction and, in particular, suggested an adaptive role for the sensor protein of two-component systems. In addition, we applied our approach to successfully identify potential determinants of resistance to drugs administered as second-line tuberculosis treatments.

evolutionary biology↗

bioRxiv2020

Neuronal NOX4 knockdown alleviates pathological tau-related alterations in a humanized mouse model of tauopathy

Approximately 44 million people worldwide live with Alzheimers disease (AD) or a related form of dementia. Aggregates of the microtubule-associated protein tau are a common marker of these neurodegenerative diseases collectively termed as tauopathies. However, all therapeutic attempts based on tau have failed, suggesting that tau may only indicate a higher-level causal mechanism. For example, increasing levels of reactive oxygen species (ROS) may trigger protein aggregation or modulate protein degradation. Here we show that type 4 NADPH oxidase (NOX), the most abundant isoform of the only dedicated reactive oxygen producing enzyme family, is upregulated in dementia and AD patients and in a humanized mouse model of tauopathy. Both global knockout and neuronal knockdown of the Nox4 gene in mice, diminished the accumulation of pathological tau and positively modified established tauopathy by a mechanism that implicates modulation of the autophagy-lysosomal pathway (ALP). Moreover, neuronal-targeted NOX4 knockdown was sufficient to reduce neurotoxicity and prevented cognitive decline, suggesting a direct and causal role for neuronal NOX4. Thus, NOX4 is a previously unrecognized causal, mechanism-based target in tauopathies and blood-brain barrier permeable specific NOX4 inhibitors could have therapeutic potential even in established disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/338954v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1dac496org.highwire.dtl.DTLVardef@1a07dd5org.highwire.dtl.DTLVardef@1a5653aorg.highwire.dtl.DTLVardef@198f3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2018

Mitochondrial Na+ import controls oxidative phosphorylation and hypoxic redox signalling

All metazoans depend on O2 delivery and consumption by the mitochondrial oxidative phosphorylation (OXPHOS) system to produce energy. A decrease in O2 availability (hypoxia) leads to profound metabolic rewiring. In addition, OXPHOS uses O2 to produce reactive oxygen species (ROS) that can drive cell adaptations through redox signalling, but also trigger cell damage1-4, and both phenomena occur in hypoxia4-8. However, the precise mechanism by which acute hypoxia triggers mitochondrial ROS production is still unknown. Ca2+ is one of the best known examples of an ion acting as a second messenger9, yet the role ascribed to Na+ is to serve as a mere mediator of membrane potential and collaborating in ion transport10. Here we show that Na+ acts as a second messenger regulating OXPHOS function and ROS production by modulating fluidity of the inner mitochondrial membrane (IMM). We found that a conformational shift in mitochondrial complex I during acute hypoxia11 drives the acidification of the matrix and solubilization of calcium phosphate precipitates. The concomitant increase in matrix free-Ca2+ activates the mitochondrial Na+/Ca2+ exchanger (NCLX), which imports Na+ into the matrix. Na+ interacts with phospholipids reducing IMM fluidity and mobility of free ubiquinone between complex II and complex III, but not inside supercomplexes. As a consequence, superoxide is produced at complex III, generating a redox signal. Inhibition of mitochondrial Na+ import through NCLX is sufficient to block this pathway, preventing adaptation to hypoxia. These results reveal that Na+ import into the mitochondrial matrix controls OXPHOS function and redox signalling through an unexpected interaction with phospholipids, with profound consequences in cellular metabolism.

biochemistry↗

bioRxiv2018

Calcium-dependent reactive oxygen formation and blood-brain barrier breakdown by NOX5 limits post-reperfusion outcome in stroke

Ischemic stroke is a predominant cause of disability worldwide, with thrombolytic or mechanical removal of the occlusion being the only therapeutic options. Reperfusion bears the risk of an acute deleterious calcium-dependent breakdown of the blood-brain-barrier. Its mechanism, however, is unknown. Here we identify type 5 NADPH oxidase (NOX5), a calcium-activated, reactive oxygen species (ROS)-forming enzyme as missing link. Using a humanised knock-in mouse model and in vitro in organotypic cultures, we find re-oxygenation or calcium overload to increase brain ROS levels in a NOX5-dependent manner. In vivo, post-ischemic ROS formation, infarct volume and functional outcomes were worsened in NOX5 knock-in mice. Of clinical and therapeutic relevance, in a human blood-barrier model pharmacological NOX inhibition also prevented acute re-oxygenation induced leakage. Our data therefore identify NOX5 as sufficient to induce acute post-reperfusion calcium-dependent blood-brain-barrier breakdown. We suggest urgent clinical validation by conducting protective post-stroke re-canalisation in the presence of a NOX inhibitor.

neuroscience↗