Biology subjects

David, T.

Publications and source records attributed to David, T..

8 recordsLinked to original sources

bioRxiv2026

Gamma-frequency firing persistently enhances intrinsic excitability in retinal ganglion cells

Experience-dependent plasticity is usually attributed to synaptic changes, but neuronal output also depends on changes in intrinsic excitability. Whether intrinsic excitability is persistently modified at the retinal output stage is unknown. Using whole-cell recordings from retinal ganglion cells (RGCs) of juvenile rats, we found that 40-Hz firing produced sustained potentiation of intrinsic excitability in low-input-resistance A-type RGCs and rapid potentiation of intrinsic excitability in high-input-resistance B-type RGCs. In A-type bursting RGCs, long-term potentiation of intrinsic excitability (LTP-IE) required Cav1 calcium channels for its induction. LTP-IE was associated with hyperpolarization of spike threshold and reduction of spike time jitter, due to reduced Kv1 potassium-family channel function. Potentiation also increased the probability that visually-evoked synaptic events triggered action potentials. Patterned firing therefore persistently reconfigures RGC input-output transformation through the Cav1-dependent regulation of Kv1 channels, revealing intrinsic plasticity at the retinal output stage.

neuroscience↗

bioRxiv2026

Homeostatic regulation of intrinsic neuronal excitability in visual thalamic relay cells induced by brief monocular deprivation

Homeostatic plasticity of intrinsic excitability (IE) in the visual system has been essentially shown at the cortical level but whether thalamic nuclei also express homeostatic plasticity of IE is unknown. We show here that 4 days of monocular deprivation (MD) at eye opening induces a homeostatic change in IE in dorsal lateral geniculate nucleus (dLGN) neurons. Neurons recorded in the dLGN region activated by the deprived eye are more excitable than neurons recorded in the dLGN region activated by the open eye. No significant changes were observed following 7 days of MD, however. Enhanced excitability in neurons from the deprived side after 4 days of MD was associated with a reduced Kv1-dependent LTP-IE, a smaller voltage ramp, and a reduced inter-spike interval, suggesting that Kv1 channels are down-regulated in deprived dLGN neurons. Furthermore, the ankyrin G signal of the axon initial segment was larger in deprived dLGN neurons compared with open ones, indicating that Nav1 channel number also undergoes homeostatic regulation, and Kv1.1 channel signals were lower in deprived neurons compared to open ones. In addition, electrical coupling was found to be strengthened in neurons displaying enhanced IE following either brief (4 days) or long (10 days) MD. These results suggest that homeostatic and Hebbian plasticity in the dLGN share common expression mechanisms involving the regulation of Kv1 channels, Nav1 channels and electrical coupling between relay neurons.

neuroscience↗

bioRxiv2026

Bovine-derived influenza A virus (H5N1) shows efficient replication in well-differentiated human nasal epithelial cells without requiring genetic adaptation

Highly pathogenic avian influenza (H5N1) viruses of clade 2.3.4.4b have caused significant losses among bird populations worldwide and have repeatedly crossed the species barrier, infecting mammals, including humans. However, efficient human-to-human transmission has not yet been observed. Here, we demonstrate that an H5N1 virus isolated from bovine milk in Texas in 2024 (H5N1Tex/24) replicates in differentiated human nasal epithelial cells as efficiently as a 2009 pandemic H1N1 virus strain (H1N1HH4/09) at both 37 {degrees}C and 33 {degrees}C. The adaptive mutations PB2-M631L and PA-K497R do not affect H5N1Tex/24 replication at 37 {degrees}C but promote replication at 33 {degrees}C. Conversely, H5N1BE/22, a virus from the same clade isolated from a pelican in 2022 that lacks these mutations, replicates in human nasal epithelial cells at 37 {degrees}C as efficiently as H5N1Tex/24 but exhibits limited replication at 33 {degrees}C. Introducing the two mutations PB2-M631L and PA-K497R did not overcome this limitation. Furthermore, nasal epithelial cells express receptors for both human and avian influenza viruses. Accordingly, no mutations were detected in HA which are known to switch receptor preference. Finally, we demonstrate that H5N1Tex/24 remains sensitive to the antiviral effects of interferon-{lambda} (IFN-{lambda}), however, infected nasal epithelial cells secrete only small amounts of this cytokine. Overall, our results suggest that H5N1Tex/24 possesses intrinsic traits enabling efficient replication in the human upper airways.

microbiology↗

bioRxiv2025

Bemnifosbuvir and remdesivir inhibit tick-borne encephalitis virus infection in complementary in vitro and ex vivo disease models

The geographical distribution and incidence of tick-borne encephalitis (TBE) have steeply increased over the past decades, raising to represent a major health concern in Asia and Europe. Symptoms of TBE, caused by infections with tick-borne encephalitis virus (TBEV), range from mild, flu-like symptoms to severe neurological disease, often accompanied by long-term sequelae persisting for several years following pathogen encounter. While effective vaccines against TBEV are available, no antiviral drugs are currently approved and therapeutic options for patients suffering from TBE are limited to supportive measures. Compounds able to disrupt viral nucleic acid synthesis bear the potential of effectively limiting viral replication and spread. Seeking to fill the therapeutic gap, we evaluated the efficacy of a panel of approved and investigational antiviral compounds in containing TBEV infection. Combining several cell lines, human neural organoids and organotypic rat brain slice cultures, we found that the nucleoside analogs remdesivir and bemnifosbuvir efficiently limit viral replication. Through infectious virus quantification, immunofluorescence analysis and flow cytometry, we report significant, dose-dependent reduction of viral loads across all models used, with inhibition observed at low doses for both drugs. Notably, while we observed bemnifosbuvir to be well tolerated, we report important cytotoxicity of remdesivir when applied to human neural organoids. Our findings identify bemnifosbuvir and remdesivir as novel treatment strategies for TBE, providing an accessible and timely response to a clinical challenge of pressing concern.

microbiology↗

bioRxiv2023

Mpox virus spreads from cell-to-cell and leads to neuronal injury in human cerebral organoids

In 2022-23, the world experienced the largest recorded monkeypox virus (MPXV) outbreak outside of endemic regions. Remarkably, cases of neurological manifestations were reported, some of which fatal. MPXV DNA and MPXV-specific antibodies were detected in the cerebrospinal fluid of encephalitis-affected patients, suggesting neuroinvasive potential of MPXV. We explored the susceptibility of neural tissue to MPXV infection using human neural organoids (hNOs) exposed to a primary isolate belonging to clade IIb lineage. The virus efficiently replicates in hNOs as indicated by the exponential increase of infectious viral loads and the elevated frequency of MPXV-positive cells over time. Electron microscopy imaging revealed the presence of viral particles as well as perinuclear viral factories. We observed susceptibility of several cell types to the virus, including neural progenitor cells and neurons. Furthermore, we detected the presence of viral antigen in neurites and in foci of grouped cells distributed throughout the tissue. In line with this, we documented significantly more cell-associated than released infectious virus, suggesting viral spread by cell-to-cell contact. Using an mNeonGreen-expressing recombinant MPXV, we confirmed cell-associated virus transmission through live-cell imaging. While hNOs displayed no evident outer morphological changes upon infection, we detected the formation of beads in neurites, a phenomenon commonly associated with neurodegenerative disorders. Live-cell imaging further confirmed the recurrent formation of neuritic beads in neurons in the days following MPXV infection, with bead formation preceding neurite-initiated cell death. Notably, treatment of MPXV infected hNOs with the antiviral drug tecovirimat resulted in a significant reduction of infectious viral loads by several orders of magnitude. Taken together, our findings suggest viral manipulation of axonal transport driving neuronal degeneration and identify a mechanism potentially contributing to MPXV-mediated neuropathology that may have therapeutic implications.

microbiology↗

bioRxiv2023

Multiscale Model for Ion Transport in Cellular Media and Applications in Smooth Muscle Cells

Ion transport in biological tissues is crucial in the study of many biological and pathological problems. Some multi-cellular structures, like the smooth muscles on vessel walls, can be treated as periodic bi-domain structures consisting of the intracellular space (ICS) and extracellular space (ECS) with semipermeable membranes in between. In this work, we first use a multi-scale asymptotic method to derive a macroscopic homogenized bidomain model from the microscopic electro-neutral (EN) model with different diffusion coefficients and nonlinear interface conditions. Then, the obtained homogenized model is applied to study ion transportation and micro-circulation in multi-celluar tissues under the impact of agonists, an internal calcium source, and extracellular potassium. Our model serves as a useful bridge between existing ordinary differential equation models and partial differential models that take into consideration spatial variation. On the one hand, numerical results show that ECS variables are almost invariant in the first two scenarios and confirm the validity of existing single-domain models, which treat variables in the ECS as constants. On the other hand, only the bidomain model is applicable to consider the effect of local extracellular potassium. Finally, the membrane potential of syncytia formed by connected cells is found to play an important role in the propagation of oscillation from the stimulus region to the non-stimulus region. Author summarySmooth muscle cells (SMCs) play a vital role in neurovascular coupling, which is the mechanism by which changes in neural activity are linked to alterations in blood flow. Dysfunctional SMCs can have significant implications for human health. The activation of SMCs is primarily regulated by the intracellular concentration of calcium ions (Ca2+). A multi-scale model for ion transport in multicellular tissue with varying connectivity has been proposed to investigate SMC activation under different stimuli. The simulation results confirm the critical role of gap junctions in wave propagation and vasoconstriction in the vessel wall. The blockage of gap junctions prevents the spread of the wave. Furthermore, the propagation of membrane potential is the primary cause of wave propagation.

cell biology↗

bioRxiv2022

Comprehensive profiling of antibody responses to the human anellome using programmable phage display

Viruses belonging to the diverse Anelloviridae family represent a major constituent of the commensal human virome. Aside from their widespread prevalence and persistence in humans and their absence of detectable pathologic associations, little is known about the immunobiology of the human anellome. In this study, we employed the Phage ImmunoPrecipitation Sequencing (PhlP-Seq) assay for comprehensive analyses of antibody binding to 56 amino acid long anellovirus peptides. We designed and constructed a large and diverse "AnelloScan" T7 phage library comprising more than 32,000 non-redundant peptides representing the ORF1, ORF2, ORF3 and TTV-derived apoptosis-inducing protein (TAIP) sequences of more than 800 human anelloviruses (spanning three genera). We used this library to profile the antibody reactivities of serum samples from 156 subjects. The vast majority of anellovirus peptides were not reactive in any of the subjects tested (n=~28,000; ~85% of the library). Antibody reactive peptides were largely restricted to the C-terminal region of the putative capsid protein, ORF1. To characterize antibody responses to newly acquired anellovirus infections, we screened a longitudinal cohort of matched blood-transfusion donors and recipients. Most transmitted anelloviruses did not elicit detectable antibody reactivity in the recipient (29 out of a total of 40 transmitted anelloviruses) and the remainder demonstrated delayed reactivity (~100-150 days after transfusion). This study represents the first large-scale epitope-level serological survey of the antibody response to the human anellome. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/486145v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@132dfforg.highwire.dtl.DTLVardef@130c47dorg.highwire.dtl.DTLVardef@b3fc97org.highwire.dtl.DTLVardef@8c49f9_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

Cathepsin D exacerbates SPARC-driven aggressiveness by limited proteolysis in triple-negative breast cancer

Extracellular matrix (ECM) remodeling by proteases results in the release of protein fragments that promote tumor progression and metastasis. The protease cathepsin D (cath-D), a marker of poor prognosis in triple-negative breast cancer (TNBC), is aberrantly secreted in the tumor microenvironment. Using degradomic analyses by TAILS, we discovered that the matricellular protein SPARC is a substrate of extracellular cath-D. In vitro, cath-D induced limited proteolysis of SPARC C-terminal extracellular Ca2+ binding domain at acidic pH, leading to the production of SPARC fragments (34-, 27-, 16-, 9-, and 6-kDa). Similarly, cath-D secreted by TNBC cells cleaved fibroblast- and cancer cell-derived SPARC at the tumor pericellular acidic pH. SPARC cleavage also occurred in TNBC tumors. Among these fragments, only the 9-kDa SPARC fragment inhibited TNBC cell adhesion and spreading on fibronectin, and stimulated their migration, endothelial transmigration, and invasion. Our study establishes a novel crosstalk between proteases and matricellular proteins in the tumor microenvironment through limited proteolysis of SPARC, revealing a novel targetable 9-kDa bioactive SPARC fragment for new TNBC treatments.

cancer biology↗