Biology subjects

Otero, A.

Publications and source records attributed to Otero, A..

5 recordsLinked to original sources

bioRxiv2026

SdiA as a Repressor of Phagocytosis and Intracellular Survival in Klebsiella pneumoniae: Insights from Macrophage and Amoeba Models

1.In 2024, the World Health Organisation (WHO) classified Klebsiella pneumoniae as a maximum priority pathogen for the development of new alternatives to antibiotics. In this context, understanding the regulation of key virulence mechanisms is essential. Here, we investigated the role of the orphan quorum-sensing receptor SdiA in modulating virulence-associated processes during macrophage infection. Deletion of sdiA ({Delta}sdiA) significantly increased susceptibility to phagocytosis, as demonstrated using an amoeba predation model in which mutant strains formed larger clearance zones compared to wild-type bacteria. This phenotype was also observed in murine macrophages, where {Delta}sdiA strains exhibited increased adhesion (1.5 to 2.5-fold) and phagocytic uptake. Reduced uronic acid levels were also quantified in mutant strains, indirectly indicating a diminished capsule production, likely contributing to this enhanced phagocytosis. Despite enhanced uptake, {Delta}sdiA strains showed increased intracellular survival and replication rates within macrophages, leading to reduced host cell viability. This effect occurred despite loss of interbacterial killing capacity against E. coli, suggesting that enhanced intracellular fitness is not driven by classical antibacterial offensive mechanisms. Notably, mutant-infected macrophages displayed increased generation of reactive oxygen species (ROS), NF-{kappa}B expression, and pro-inflammatory cytokines (mCXCL10 and mTNF) production, indicating that macrophage defence mechanisms are not impaired during mutant infection. Overall, bacterial survival of {Delta}sdiA could result from overwhelming, rather than actively suppressing, host defences. Together, these findings identify SdiA as a negative regulator of phagocytosis and intracellular survival in K. pneumoniae and highlight a context-dependent role in virulence. This work provides new insights into the regulatory networks governing host-pathogen interactions and bacterial adaptation to the intracellular environment. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/725935v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1d45bfdorg.highwire.dtl.DTLVardef@e3547forg.highwire.dtl.DTLVardef@c078f9org.highwire.dtl.DTLVardef@46408a_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO Loss of sdiA strongly affects phagocytosis, as mutant strains showed increasing adhesion (1.5 to 2.5-fold) and phagocytic uptake. Diminished capsule production could be contributing to this enhanced phagocytosis, as reduced uronic acid levels were also quantified in mutant strains. Despite being internalized at higher rates, mutants exhibited enhanced intracellular survival and replication, reducing macrophage viability. This fitness advantage occurred independently of classical offensive mechanisms, as evidenced by a lost ability to kill E. coli. Notably, mutant-infected macrophages mounted a stronger immune response, marked by elevated ROS, NF-{kappa}B expression, and pro-inflammatory cytokines production (mCXCL10 and mTNF). Together, these findings suggest that strains survive by overwhelming, rather than suppressing, host immune defences. Created with Biorender (https://www.biorender.com/). C_FIG HighlightsO_LISdiA deletion in K. pneumoniae increases susceptibility to phagocytosis. C_LIO_LIThe mutant strains exhibit reduced uronic acid levels, indicative of capsule production. C_LIO_LISdiA mutants show enhanced intracellular survival and higher macrophage death. C_LIO_LIMutant infected macrophages have higher NF-{kappa}B, TNF, and CXCL10 responses. C_LIO_LISdiA-deficient strains lose predatory capacity against E. coli. C_LI

microbiology↗

bioRxiv2025

Demonstration of SLU7 as a new pan-cancer target

Cancer treatment remains challenging due to heterogeneous responses to immunotherapy across patients and tumor types. Innovative strategies are required to overcome immune evasion. We have identified the splicing factor SLU7 as essential for the survival of cancer cells from diverse origins. SLU7 knockdown induces R-loop accumulation, transcription-dependent genomic instability, DNA damage, and replication catastrophe, together with aberrant splicing and inhibition of nonsense-mediated mRNA decay (NMD) and/or DNA methylation. These alterations lead to the expression of neoantigens, interferon B1, endogenous retroviruses, and cancer-testis antigens, which would enhance tumor immunogenicity. Therefore, we propose SLU7 targeting as a dual-action therapy, combining direct tumor suppression with immune activation. Using various murine cancer models, including orthotopic liver tumors, and multiple molecular strategies--such as inducible CRISPR/Cas9, systemic delivery of chimeric siSLU7-nucleolin aptamers (APTASLU), and intratumoral injection of siSLU7-loaded nanoparticles--we show that distinct siSLU7 sequences and delivery platforms effectively inhibit tumor growth. Furthermore, SLU7 silencing synergizes with immune checkpoint inhibitors, amplifying anti-tumor responses. Our in vivo data demonstrate that SLU7 is a promising, versatile target for diverse cancers. Its multimodal mechanism offers potential to overcome tumor heterogeneity, reverse immune tolerance, and enhance immunotherapy efficacy.

cancer biology↗

bioRxiv2024

Regulatory effects on virulence and phage susceptibility revealed by sdiA mutation in Klebsiella pneumoniae

The World Health Organization has identified multi-drug resistant (MDR) Klebsiella pneumoniae strains as the highest priority in 2024. SdiA, a LuxR-like quorum sensing (QS) receptor that responds to N-acyl-homoserine lactones (AHLs), exerts a substantial regulatory influence on the virulence of numerous Gram-negative bacteria. The function of this receptor in the virulence of K. pneumoniae remains uncertain. Nevertheless, further investigation into the significance of this receptor is needed, as it represents an intriguing avenue with the potential to contribute to the development of novel antimicrobial strategies. The objective of the present study was to elucidate the function of SdiA in K. pneumoniae biofilm formation and virulence. To this end, a genetic knockout of sdiA was conducted, and virulence-related phenotypic studies were performed following AHL provision. The results demonstrate that SdiA deficiency increases susceptibility to phage infection and human serum resistance, and promotes biofilm maturation and cell filamentation. No effect on virulence was observed in vivo in the Galleria mellonella infection model. The addition of N-hexanoyl-L-homoserine lactone (C6-HSL) promoted SdiA-dependent biofilm maturation but also enhanced serum resistance and reduced virulence against G. mellonella in the absence of SdiA. The results of this study demonstrate that C6-HSL and SdiA exert a dual influence on virulence phenotypes, operating both independently and hierarchically. These findings provide new insights into the virulence of K. pneumoniae and its regulation by SdiA. ImportanceThis study represents a significant contribution to our understanding of the complex regulatory mechanisms that govern the virulence of multi-drug resistant Klebsiella pneumoniae through quorum sensing (QS). The study offers insights into the function of SdiA, a QS receptor, in the regulation of biofilm formation, susceptibility to phage infection, serum resistance, and cell filamentation in this bacterium. Furthermore, the findings of this study demonstrate that exogenous N-acyl-homoserine lactone (AHL) signalling influences the aforementioned virulence phenotypes in both a SdiA-dependent and independent manner, as well as in a hierarchical manner.

microbiology↗

bioRxiv2019

Plant budding speciation predominant by ecological and geographical differentiation: an ‘evolutionary snapshot’ in Iberodes (Boraginaceae)

O_LITraditional classification of speciation modes has focused on physical barriers to gene flow. While allopatry has been viewed as the most common mechanism of speciation, parapatry and sympatry, both entail speciation in the face of ongoing gene flow and thus both are far more difficult to detect and demonstrate. Iberodes (Boraginaceae, NW Europe) with a small number of recently derived species (five) and contrasting morphological traits, habitats and distribution patterns constitutes an ideal system in which to study drivers of lineage divergence and differentiation. C_LIO_LITo reconstruct the evolutionary history of the genus, we undertook an integrative study entailing: (i) phylogenomics based on restriction-site associated DNA sequencing (RAD-seq), (ii) morphometrics, and (iii) climatic niche modelling. C_LIO_LIKey results revealed a history of repeated progenitor-derivative speciation, manifesting in paraphyletic pattern within Iberodes. Climatic niche analyses, together with the morphometric data and species distributions, suggest that ecological and geographical differentiation have interacted to shape the diversity of allopatric and parapatric distributions observed in Iberodes. C_LIO_LIOur integrative study has enabled to overcome previous barriers to understanding parapatric speciation by demonstrating the recurrence of progenitor-derivative speciation in plants with gene flow and ecological differentiation, explaining observed parapatry and paraphyly. C_LI

evolutionary biology↗

bioRxiv2017

Whole-exome sequencing of plasma cell-free DNA portrays the somatic mutation landscape of refractory metastatic colorectal cancer and enables the discovery of mutated KDR/VEGFR2 receptors as modulators of anti-angiogenic therapies.

The non-invasive detection of cancer mutations is a breakthrough in oncology. Here, we applied whole-exome sequencing of matched germline and basal plasma cell-free DNA samples (WES-cfDNA) on a RAS/BRAF/PIK3CA wild-type metastatic colorectal cancer patient with primary resistance to standard treatment regimens including VEGFR inhibitors. Using WES-cfDNA, we could detect 73% (54/74) of the somatic mutations uncovered by WES-tumor including a variety of mutation types: frameshift (indels), missense, noncoding (splicing), and nonsense mutations. Additionally, WES-cfDNA discovered 14 high-confidence somatic mutations not identified by WES-tumor. Importantly, in the absence of the tumor specimen, WES-cfDNA could identify 68 of the 88 (77.3%) total mutations that could be identified by both techniques. Of tumor biology relevance, we identified the novel KDR/VEGFR2 L840F somatic mutation, which we showed was a clonal mutation event in this tumor. Comprehensive in vitro and in vivo functional assays confirmed that L840F causes strong resistance to anti-angiogenic drugs, whereas the KDR/VEGFR2 hot-spot mutant R1032Q confers sensitivity to cabozantinib. Moreover, we found a 1-3% of recurrent KDR somatic mutations across large and non-overlapping cancer sequencing projects, and the majority of these mutations were located in protein residues frequently mutated in other cancer-relevant kinases, such as EGFR, ABL1, and ALK, suggesting a functional role.\n\nIn summary, the current study highlights the capability of exomic sequencing of cfDNA from plasma of cancer patients as a powerful platform for somatic landscape analysis and discovery of resistance-associated cancer mutations. Because of its advantage to generate results highly concordant to those of tumor sequencing without the hurdle of conventional tumor biopsies, we anticipate that WES-cfDNA will become frequently used in oncology. Moreover, our study identified for the first-time KDR/VEGFR2 somatic mutations as potential genetic biomarkers of response to anti-angiogenic cancer therapies and will serve as reference for further studies on the topic.

cancer biology↗