Biology subjects

Carrion, F.

Publications and source records attributed to Carrion, F..

5 recordsLinked to original sources

bioRxiv2025

Engineering directional phosphoryl flow enables programmable signaling dynamics in bacteria

Cells must make critical decisions by integrating information from a constantly changing environment to ensure their survival. They rely on intricate signaling networks to detect external and internal cues to trigger specific responses, yet these systems are generally viewed as components wired with simpler linear connections. Bacterial phosphorelay systems offer a versatile framework for studying more complex connections and engineering new biological circuits. Here, using the well-studied Bacillus subtilis sporulation phosphorelay, we demonstrate that the directionality of information flow can be reprogrammed to generate different dynamic responses. We show that phosphoryl-transfer reversibility is an evolvable trait encoded in conserved, surface-exposed motifs of two-component system proteins. Unidirectional phosphoryl-transfer generates a short-term information storage mechanism, enabling signal integration over time and allowing phosphatases, acting at different levels, to produce different outcomes. In contrast, a bidirectional system enhanced the action of phosphatase activity early in the pathway. The ability to control phosphoryl-transfer equilibria opens exciting avenues for designing sophisticated synthetic signaling systems with enhanced decision-making capabilities.

systems biology↗

bioRxiv2025

Echinococcus granulosus antigen B acts as an LPS-scavenging lipoprotein in vitro preventing TLR4-mediated activation of dendritic cells

Echinococcus granulosus sensu lato antigen B (EgAgB) is a major parasite lipoprotein, produced by the hydatid and released at the host-parasite interface. Accumulating evidence supports that EgAgB may exert immunomodulatory effects on myeloid cells; however, the underlying molecular mechanisms remain poorly understood. We examined the impact of native EgAgB (nEgAgB) and recombinant EgAgB8/1 (rEgAgB) on lipopolysaccharide (LPS)-induced activation of bone marrow-derived dendritic cells (BMDC), to help elucidate these mechanisms. Both immunoaffinity-purified nEgAgB or rEgAgB induced modest BMDC activation, indicated by the production of IL-6, IL-12p40, and nitric oxide, but not IFN-{beta}. This activation was primarily attributed to LPS traces in EgAgB preparations since it was nearly abolished by a specific TLR4 inhibitor and in Tlr4-/- BMDC, while EgAgB binding to BMDC was TLR4-independent. Notably, both nEgAgB and rEgAgB inhibited LPS-induced cytokine and nitric oxide production, and disrupted TLR4 dimerization and endocytosis. Competitive binding assays showed that EgAgB and human high-density lipoprotein (hHDL) similarly inhibited LPS binding to macrophages and BMDC; however, EgAgB more effectively suppressed LPS-induced cytokine secretion. Contrastingly, EgAgB did not modulate BMDC responses to lipoteichoic acid, unlike hHDL. Using dynamic light scattering and an ELISA-like assay, we demonstrated a higher potential of EgAgB to bind LPS than hHDL. Additionally, docking analyses suggest the presence of a defined LPS-binding interface in EgAgB8/1 subunit. Overall, these findings reveal a novel binding property of EgAgB, which enables it to act as an extracellular LPS scavenger, interfering with TLR4-mediated LPS recognition and downstream proinflammatory responses in myeloid cells.

immunology↗

bioRxiv2024

A versatile reporter system to study cell-to-cell and cell-free bovine leukemia virus infection

Bovine leukemia virus (BLV) is a B-lymphotropic oncogenic retrovirus of the genus Deltaretrovirus that infects dairy cattle worldwide and is the causative agent of enzootic bovine leukosis. BLV demonstrates remarkably low efficiency in infecting cells via free viral particles derived from infected B cells, as virions are rarely detected in the bloodstream of infected cattle. However, transmission efficacy significantly increases upon the establishment of direct cell-to-cell interactions. Syncytium formation assays are the main tool in the study of BLV infectivity. Although this traditional method is highly robust, the complexity of visually counting syncytia poses a significant technical challenge. Using lentiviral vectors, we generated a stable reporter cell line, in which the GFP reporter gene is under the control of the full-length BLV-LTR. We have demonstrated that the BLV-Tax protein and histone deacetylases inhibitors, such as VPA and TSA, can transactivate the BLV LTR. Upon co-culturing the reporter cell line with BLV-infected cells, fluorescent syncytia can be visualized. By implementing automated scanning and image acquisition using a confocal microscope, together with the development of an analysis software, we can detect and measure single GFP cells and fluorescent multinucleated cells. In summary, our reporter cell line, combined with the development of analysis software, is a useful tool for understanding the role of cell fusion and cell-free mechanism of transmission in BLV infection.

microbiology↗

bioRxiv2021

Molecular basis of unidirectional information transmission in two-component systems: lessons from the DesK-DesR thermosensor

Cellular signaling systems transmit information over long distances using allosteric transitions and/or post-translational modifications. In two-component systems the sensor histidine kinase and response regulator are wired through phosphoryl-transfer reactions, using either a uni- or bi-directional transmission mode, allowing to build rich regulatory networks. Using the thermosensor DesK-DesR two-component system from Bacillus subtilis and combining crystal structures, QM/MM calculations and integrative kinetic modeling, we uncover that: i) longer or shorter distances between the phosphoryl-acceptor and -donor residues can shift the phosphoryl-transfer equilibrium; ii) the phosphorylation-dependent dimerization of the regulator acts as a sequestering mechanism by preventing the interaction with the histidine kinase; and iii) the kinases intrinsic conformational equilibrium makes the phosphotransferase state unlikely in the absence of histidine phosphorylation, minimizing backwards transmission. These mechanisms allow the system to control the direction of signal transmission in a very efficient way, showcasing the key role that structure-encoded allostery plays in signaling proteins to store and transmit information.

biophysics↗

bioRxiv2018

NFAT5 participates in Inducible Nitric Oxide Synthase activation by hypoxia in MEF cells.

We previously described the protective role of NFAT5 during hypoxia, in an independent way of HIF-1. Alternatively, inducible NO synthase (iNOS) is also induced by hypoxia. The aim of this study was to establish the NFAT5 target gene in mouse embryonic fibroblasts (MEF) cell stimulated by hypoxia. NFAT5, iNOS, NO level, aquaporin 1 (AQP1) and urea transporter 1 (UTA1) were induced by low oxygen levels in MEF cells. Additionally, NFAT5 and UTA1 were induced in reoxygenation (after 24hrs of hypoxia). NFAT5 transactivation domain (TAD) was induced during hypoxia and hypoxia/reoxygenation. Two MEF cells line independently produced for altered NFAT5 (Knockout and DBD-mutant) lost the iNOS and AQP1 induction by low oxygen. The iNOS induction was recovered in NFAT5-KO MEF cells, when recombinant NFAT5 protein expression was reconstituted, but not for NFAT5 DBD-mutant MEF cells, explained by its dominant negative effect. Finally, we found a negative feedback loop of iNOS effect over NFAT5 protein abundance. This work provides a relevant information about signaling pathway of NFAT5 during adaptive responses to oxygen depletion.

physiology↗