Biology subjects

Lai, M.

Publications and source records attributed to Lai, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Sex-dimorphic immune trajectories across the canine lifespan and early-life signatures of geroprotective interventions

Canine models are invaluable for translational geroscience, but widespread gonadectomy in companion dogs obscures natural sex-specific aging trajectories. Here, we characterize the age-associated hematologic and serum cytokine profiles of 80 intact laboratory Beagles spanning 1 to 11 years. Contrary to classical linear models of immunosenescence and inflammaging, we reveal that canine immune aging is highly dynamic and sexually dimorphic. While absolute leukocyte counts declined continuously, cytokine remodeling was sex-specific: intact males exhibited extensive age-dependent inflammatory restructuring, whereas females demonstrated restricted fluctuations. To establish baseline geroprotective signatures, we evaluated 24 young beagles following a 90-day intervention with rapamycin, canagliflozin, or dietary restriction. Rapamycin induced robust immune modulation, while canagliflozin prompted early, sex-biased weight loss and narrower cytokine responses. Together, our findings demonstrate that canine immune aging involves complex, sexually dimorphic remodeling. By utilizing an intact cohort to isolate natural dimorphic trajectories, we provide a crucial foundation for developing precision, sex-optimized geroprotectors.

physiology↗

bioRxiv2026

Peroxisome dynamics during HSV-1 life cycle in human neurons

HSV-1 is increasingly implicated in Alzheimers disease, yet the mechanisms by which it reshapes neuronal metabolism remain incompletely understood. Here, we demonstrate that HSV-1 co-opts peroxisomal biogenesis and lipid metabolic pathways to promote its replication across human neuronal models. In SH-SY5Y cells, infection triggers a marked expansion of the peroxisomal compartment and alters organelle morphology through upregulation of PGC-1 and PEX13/14/19. Pharmacological stimulation of peroxisome proliferation enhances viral production, whereas inhibition of PEX3-PEX19-dependent biogenesis almost completely suppresses infection. Lipidomic profiling reveals a selective increase in peroxisome-derived plasmalogens and sphingolipids, supporting a role for peroxisomes as a metabolic hub for viral envelopment. This remodeling is recapitulated in hiPSC-derived neurons and human brain organoids, where it is strictly dependent on productive replication and re-emerges upon viral reactivation, but not during latency. Collectively, these findings identify peroxisomes as essential replication-permissive organelles exploited by HSV-1 and suggest that recurrent virus-driven peroxisomal and ether-lipid reprogramming may contribute to neuronal vulnerability in neurodegenerative disease.

microbiology↗

bioRxiv2026

Hierarchical Assembly of Native Cytoplasmic Lattices Revealed by Cryo-EM

Oocytes depend on maternal factors for maturation and early embryogenesis. Cytoplasmic lattices (CPLs) are distinctive fibrillar structures in mammalian oocyte cytoplasm implicated in maternal factor storage and developmental competence, yet their molecular composition and architecture remain elusive. Here, we use cryo-electron microscopy to resolve the high-resolution structure of native mouse oocyte CPLs. We identify 14 intrinsic components of multiple copies that assemble into filaments in which PADI6-mediated self-assembly and two subtypes of subcortical maternal complexes (SCMCs) form the core scaffold. Unexpectedly, we discover that /{beta}-tubulin dimers and two autoinhibited ubiquitination modules (UHRF1-UBE2D3, SKP1-FBXW18) are internal components of CPLs. We also uncover multivalent interactions that organize adjacent CPL filaments into higher-order helical bundles. By integrating CPL structure with biochemical and proteomic data, we propose a hierarchical assembly mechanism of CPLs, from subcomplexes to filaments to supramolecular lattices. Our study offers mechanistic insights into how maternal proteins are spatially organized to ensure successful early embryonic development and provides a structural foundation for understanding female infertility related to CPL-associated gene mutations.

developmental biology↗

bioRxiv2026

A NAPE-LRRK2 metabolic axis controls lysosomal homeostasis in Parkinson's disease

N-acylphosphatidylethanolamines (NAPEs) are atypical glycerophospholipids that accumulate in response to cellular stress, yet their roles beyond serving as precursors of fatty-acid ethanolamines (FAEs) remain largely unexplored. Here, we identify NAPEs as endogenous regulators of leucine-rich repeat kinase 2 (LRRK2), a master controller of lysosomal homeostasis and a genetic driver of Parkinsons disease. We show that increasing NAPE synthesis or blocking their hydrolysis inhibits LRRK2 kinase activity, enhances lysosomal function, and promotes the clearance of -synuclein aggregates. Conversely, cells in which NAPE hydrolysis is enhanced display increased LRRK2 activation and lysosomal dysfunction. Importantly, in induced pluripotent stem cell-derived dopaminergic neurons carrying the LRRK2-G2019S variant, pharmacological inhibition of NAPE-PLD - the enzyme that degrades NAPEs - restores lysosomal activity and favors the clearance of preformed -synuclein fibrils. Together, our findings identify NAPEs as previously unrecognized lipid regulators of LRRK2 signaling and lysosomal function, revealing a metabolic axis with therapeutic potential in Parkinsons disease. TeaserBoosting neuronal NAPEs silences LRRK2 hyperactivity and clears -synuclein: a lipid-based strategy for Parkinsons disease.

cell biology↗

bioRxiv2026

Unconventional Small Molecule MNP-021 Protects Neuronal and Glial Function from Diabetes-Associated Glucotoxicity and Neuroinflammation

BackgroundDiabetes-associated neurodegeneration is amplified by methylglyoxal (MGO)-driven dicarbonyl stress linking hyperglycemia to neuronal insulin resistance and maladaptive neuroinflammation. We tested the neuroprotective activity of MNP-021, a non-electrophilic TRPA1 modulator, in neurons and glial cells in vitro. MethodsSH-SY5Y neurons were pretreated with MNP-021 and challenged with MGO, then profiled by high-content imaging, RNA-seq, Seahorse OCR/ECAR, glycolytic stress assays and AKT/ERK/CREB immunoblotting {+/-} insulin. In parallel, HMC3 glial cells were treated with MNP-021, exposed to LPS/TNF- or A{beta}(25-35) and tested for viability and inflammatory markers by ELISA and qRT-PCR. ResultsMGO increased nucleus-to-cytoplasm area ratio by 49% and dysregulated glucose handling, increasing 2-NBDG uptake by [~]25%, with GLUT1/GLUT4 membrane redistribution; MNP-021 normalized morphology, uptake, and transporter localization without cytotoxicity up to 10 {micro}M. RNA-seq identified 754 MGO-deregulated genes, including ISR/metabolic nodes (GCK, SESN2, PHGDH/PSAT1, PCK2); MNP-021 buffered stress-induced transcription with limited baseline effects, remodeled mitochondrial redox readouts consistent with controlled ROS signaling, while improving mitochondrial content/architecture and blunting stress-evoked compensatory glycolysis. MNP-021 restored pro-survival signaling (pAKT/pERK and nuclear pCREB), including insulin responsiveness during MGO exposure. MNP-021 reduced IL-6/TNF- release while increasing IL-10 and ARG1 ([~]1.9-fold vs LPS/TNF-) in HMC3 glial cells, shifting them toward a pro-resolving IL-10/ARG1 program with reduced A{beta}(25-35)-evoked cytokine release with GLP-1 remaining very low ([≤]10 pg/mL) and not significantly increased in this system. ConclusionsMNP-021 coordinates transcriptomic restraint, transporter-level glucose handling, mitochondrial resilience, and pro-survival/pro-resolving signaling across neuron-microglia compartments, supporting TRPA1-tuned small-molecule modulation as a candidate strategy against dicarbonyl-linked neuro-metabolic stress.

physiology↗

bioRxiv2025

A unique two-excipient heat stable tablet formulation of oral insulin: preliminary results

We report a novel formulation approach for development of a thermostable oral insulin tablet. Using freeze drying to form a heat stable tablet in a single-step process, we demonstrate hydroxypropyl beta cyclodextrin (HP-{beta}-CD) encapsulated lipophilic ion-pair complex of insulin using bile salt achieves intestinal absorption and sustained glucose levels. The tablets produced using this simple approach with only two excipients offer protection from enzymatic and stomach acid degradation and facilitate insulin uptake, without any need for specialized drug manufacturing or enteric coating. Insulin in this innovative formulation is thermotolerant, capable of maintaining stability even under heat stress at 30-40{degrees}C/65-75% RH. The convenient presentation of insulin as a thermostable oral tablet presents a low-cost scalable manufacturing method that simplifies the logistics of storage, transport, and distribution in any setting, including areas where cold storage maybe limited or unavailable. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/635377v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@16b4b64org.highwire.dtl.DTLVardef@122c11forg.highwire.dtl.DTLVardef@b50c0borg.highwire.dtl.DTLVardef@29bf28_HPS_FORMAT_FIGEXP M_FIG Our unique formulation approach protects insulin from stomach and temperature induced degradation, improves intestinal permeability providing a sustained release of insulin for glycemic control. The freeze dried tablet product format is easily scalable and flexible, increasing accessibility across all populations. C_FIG

biochemistry↗

bioRxiv2024

Microenvironment T-Type calcium channels regulate neuronal and glial processes to promote glioblastoma growth

BackgroundGlioblastoma (GBM) is the most common primary malignant brain tumor. The aim of this study was to elucidate the role of microenvironment and intrinsic T-type calcium channels (Cav3) in regulating tumor growth and progression. MethodsWe grafted syngeneic GBM cells into Cav3.2 knockout mice to assess the role of microenvironment T-Type calcium channels on GBM tumor growth. We performed single-cell RNA-seq (scRNA-seq) of tumors from WT and Cav3.2 KO mice to elucidate the regulation of tumors by the microenvironment. We used neurons from WT and Cav3.2 KO mice in co-culture with GBM stem cells (GSC) to assess the effects of Cav3.2 on neuron/GSC synaptic connections and tumor cell growth. ResultsCav3.2 KO in the microenvironment led to significant reduction of GBM growth and prolongation of animal survival. scRNA-seq showed that microenvironment Cav3.2 regulates neuronal and glial biological processes. Microenvironment Cav3.2 downregulated numerous genes associated with regulating the OPC cell state in GBM tumors such as SOX10 and Olig2. Neuronal Cav3.2 promoted neuron/GSC synaptic connections and GSC growth. Treatment of GSCs with the Cav3 blocker mibefradil downregulated genes associated with neuronal processes. The Cav3 blocker drug mibefradil synergized with temozolomide (TMZ) and radiation to reduce in vivo tumor growth and prolong animal survival. ConclusionsTogether these data reveal a role for microenvironment Cav3 in promoting GBM tumor progression through regulating neuronal and glial processes particularly associated with the OPC-cell state. Targeting both intrinsic and microenvironment Cav3 with the inhibitor mibefradil significantly enhanced the anti-GBM effects of TMZ and radiation. Key PointsO_LIMicroenvironment Cav3.2 promotes GBM progression C_LIO_LIMicroenvironment Cav3.2 promotes neuronal and glial processes C_LIO_LIPharmacological targeting of intrinsic and microenvironment Cav3 synergizes with TMZ/radiation C_LI Importance of the StudyIn this study, we demonstrate for the first time that microenvironment Cav3.2 contributes to GBM progression and growth by regulating neuronal and glial processes. Our findings highlight the importance of T-type calcium channels in the microenvironment as well as the tumor and provides preclinically relevant data for the use of mibefradil to inhibit GBM growth in combination with standard of care therapies.

cancer biology↗

bioRxiv2024

A Transfection-Free Approach of Gene Editing via a gold-based nanoformulation of the Cas9 protein

In recent years, the CRISPR/Cas9 technology has emerged as a highly efficient tool for cell gene editing. However, the delivery of the CRISPR/Cas9 system into cells remains a significant challenge, drastically limiting in vivo gene therapy applications. In this study, we present a transfection/transduction-free tool for intracellular delivery of the Cas9:gRNA ribonucleoprotein. The Cas9 enzyme is conjugated to a 12 nm gold nanoparticle through affinity binding between the 6x His-tag of the protein and the NTA-Ni{superscript 2}LJ groups on the nanoparticles. This link chemistry allows a fine control of the density of the enzymes decorating the particle surface, the orientation of the bonding and the stability of the interaction. Importantly, the surface chemistry of this nanoformulation has been precisely engineered to modulate the cellular internalization and localization. Thanks to this approach of precision chemistry, this nanoformulation demonstrated the ability to spontaneously enter human melanoma cells as monodispersed particles that localize in cell cytoplasm, endosomes, and nucleus. It also shows effective gene editing efficiency similarly to conventional transfection tools. This gold-based formulation of Cas9 represents a ready-to-use biotech editing tool, and a promising solution for direct in vivo gene editing applications.

molecular biology↗

bioRxiv2024

N-acylethanolamine acid amidase inhibition reduces SARS-CoV-2 infection in Human Precision cut-lung slices and downregulates NF-kappaB signalling.

Like other positive-sense RNA viruses, SARS-CoV-2 manipulates host lipid metabolism to facilitate its replication by enhancing lipogenesis and lipid droplet formation. In doing so, SARS-CoV-2 infection perturbs bioactive lipid levels associated with the inflammatory response. One of these, Palmitoylethanolamide (PEA) is suppressed during SARS-CoV-2 infection since it activates the Peroxisome Proliferator-Activated Receptor- (PPAR-), a transcription factor that suppresses the nuclear factor-B (NF-{kappa}B), which is mandatory to sustain SARS-CoV-2 replication. PEA levels are regulated by N-acylethanolamine acid amidase (NAAA), a lysosomal enzyme responsible for catalysing the breakdown of PEA. We hypothesized that NAAA inhibition might interfere with SARS-CoV-2 replication since it will lead PEA to accumulate, activating PPAR- and, consequently, suppressing NF-{kappa}B. Our results reveal that genetic or chemical ablation of NAAA significantly suppresses SARS-CoV-2 replication by three log10 in human-derived precision-cut lung slices. Therefore, we investigated whether inhibiting NAAA could influence NF-{kappa}B activation through the activation of PPAR-. We observed PPAR- increased expression in NAAA-/-cells, while PPAR- expression remained low in infected parental cells. As expected, the elevated PPAR- expression correlated with a parallel reduction in NF-{kappa}B activation when NAAA is ablated. These findings underscore NAAA as an essential host factor for SARS-CoV-2 replication and propose a potential mechanism of action rooted in the attenuation of NF-{kappa}B activation during viral replication. Author summaryOver the past three years, COVID-19 has claimed nearly 7 million lives worldwide, prompting extensive efforts to find effective treatments. While RNA-based vaccines have been developed rapidly, they alone have not completely halted the spread of the virus, making the search for antiviral therapies crucial. One promising approach targets the anti-inflammatory lipid PEA, which has shown some success in COVID-19 clinical trials. PEA is quickly degraded by the enzyme NAAA. Researchers have found that inhibiting NAAA can enhance and prolong PEA anti-inflammatory effects. NAAA inhibitors have already shown effectiveness in reducing chronic pain and lung inflammation in animal models and have also been effective against Zika virus replication. Our research focused on testing the NAAA inhibitor ARN726 against SARS-CoV-2. In human lung cells and lung tissue samples, ARN726 significantly reduced SARS-CoV-2 replication and inflammation. We discovered that this inhibition suppresses the NF-{kappa}B pathway, which the virus uses to fuel its replication and sustain Cytokine storm. Overall, our findings suggest that NAAA inhibitors like ARN726 could be repurposed to combat COVID-19 and potentially other coronaviruses, offering a novel and effective antiviral strategy.

microbiology↗

bioRxiv2024

Diversity and ecological potentials of viral assemblages from the seamount sediments of the Northwest Pacific Ocean

Viruses are the most abundant life forms in the sea, influencing the community structure and metabolism of host cells as well as biogeochemical cycles. However, the diversity and ecological roles of viruses within seamount ecosystems, natural microbiota havens characterized by high biodiversity, remain unknown. Here, the first seamount viral genome (SMVG) dataset, based on a metagenomic analysis of twelve seamount sediment samples collected from the seamount regions of the Northwest Pacific Ocean, is established. A total of 78,069 viral operational taxonomic units (vOTUs) were found, spanning 18 viral classes and 63 viral families. The detection of sixteen viral auxiliary metabolic genes (vAMGs) suggests that viruses may participate in both the complex metabolic dynamics associated with sediment microbial communities and also biogeochemical cycles, including carbon, sulfur, metal, heme, and cobalamin cycling. vAMGs involved in the metabolism of heme, cobalamin and metals, in particular, are more often detected in seamount sediments than in trenches, cool seeps, and hydrothermal vents. This investigation of the viral communities in these seamount sediments provides new insights into the high diversity and ecological potential of the viruses and establishes a foundation for the future study of benthic viruses from deep-sea seamounts.

ecology↗

bioRxiv2023

Semantic composition in experimental and naturalistic paradigms

Naturalistic paradigms using movies or audiobooks have become increasingly popular in cognitive neuroscience, but connecting them to findings from controlled experiments remains rare. Here, we aim to bridge this gap in the context of semantic composition in language processing, which is typically examined using a "minimal" two-word paradigm. Using magnetoencephalography (MEG), we investigated whether the neural signatures of semantic composition observed in an auditory two-word paradigm can extend to naturalistic story listening, and vice versa. Our results demonstrate consistent differentiation between phrases and single nouns in the left anterior and middle temporal lobe, regardless of the context. Notably, this distinction emerged later during naturalistic listening. Yet this latency difference disappeared when accounting for various factors in the naturalistic data, such as prosody, word rate, word frequency, surprisal, and emotional content. These findings suggest the presence of a unified compositional process underlying both isolated and connected speech comprehension.

neuroscience↗

bioRxiv2023

Mecp2 Fine-tunes Quiescence Exit by Targeting Nuclear Receptors

Quiescence (G0) maintenance and exit are crucial for tissue homeostasis and regeneration in mammals. Here, we show that methyl-CpG binding protein 2 (Mecp2) expression is cell cycle-dependent and negatively regulates quiescence exit in cultured cells and in an injury-induced liver regeneration mouse model. Specifically, acute reduction of Mecp2 is required for efficient quiescence exit, as deletion of Mecp2 accelerates, while overexpression of Mecp2 delays quiescence exit, and forced expression of Mecp2 after Mecp2 conditional knockout rescues cell cycle reentry. The E3 ligase Nedd4 mediates the ubiquitination and degradation of Mecp2, and thus facilitates quiescence exit. Genome-wide study uncovered the dual role of Mecp2 in preventing quiescence exit by transcriptionally activating metabolic genes while repressing proliferation-associated genes. Particularly, disruption of two nuclear receptors (NRs), Rara or Nr1h3, accelerates quiescence exit, mimicking the Mecp2 depletion phenotype. Our studies unravel a previously unrecognized role for Mecp2 as an essential regulator of quiescence exit and tissue regeneration.

cell biology↗

bioRxiv2022

openNAU: An open-source platform for normalizing, analyzing, and visualizing untargeted metabolomics data

MotivationAs an important part of metabolomics analysis, untargeted metabolomics has become a powerful tool in the study of tumor mechanisms and the discovery of metabolic markers with high-throughput spectrometric data which also brings great challenges to data analysis from the extraction of raw data to the identification of differential metabolites. To date, a large number of analytical tools and processes have been developed and constructed to serve untargeted metabolomics research. The different selection of analytical tools and parameter settings lead to varied results of untargeted metabolomics data. Our goal is to establish an easily operated platform and obtain a repeatable analysis result. ResultsWe used the R language basic environment to construct the preprocessing system of the original data and the LAMP (Linux + Apache + MySQL + PHP) architecture to build a cloud mass spectrum data analysis system. An open-source analysis software for untargeted metabolomics data (openNAU) was constructed. It includes the extraction of raw mass data and quality control for the identification of differential metabolic ion peaks. A reference metabolomics database based on public databases was also constructed. Finally, a complete analysis system platform for untargeted metabolomics was established. This platform provides a complete template interface for the addition and updating of the analysis process, so we can finish complex analyses of untargeted metabolomics with simple human-computer interactions. Availability and ImplementationThe source code can be downloaded from https://github.com/zjuRong/openNAU. Contactsunqingrong@zju.edu.cn

bioinformatics↗

bioRxiv2022

N-acylethanolamine acid amide hydrolase is a novel target for drugs against SARS-CoV-2 and Zika virus

Several compounds have been tested against SARS-CoV-2; at present, COVID-19 treatments decrease the deleterious inflammatory response and acute lung injury. However, the best therapeutic response would be expected by combining anti-inflammatory properties, while concomitantly blocking viral replication. These combined effects should drastically reduce both infection rate and severe complications induced by novel SARS-CoV-2 variants. Therefore, we explored the antiviral potency of a class of anti-inflammatory compounds that inhibit the N-Acylethanolamine acid amidase (NAAA). This enzyme catalyzes the hydrolysis of palmitoylethanolamide (PEA), a bioactive lipid that mediates anti-inflammatory and analgesic activity through the activation of peroxisome proliferator receptor- (PPAR-). Similarly, this pathway is likely to be a significant target to impede viral replication since PPAR- activation leads to dismantling of lipid droplets, where viral replication of Flaviviruses and Coronaviruses occurs. Here, we show that either genetic or pharmacological inhibition of the NAAA enzyme leads to five-fold reduction in the replication of both SARS-CoV-2 and ZIKV in various cell lines. Once NAAA enzyme is blocked, both ZIKV and SARS CoV-2 replication decrease, which parallels a sudden five-fold decrease in virion release. These effects induced by NAAA inhibition occurs concomitantly with stimulation of autophagy during infection. Remarkably, parallel antiviral and anti-inflammatory effects of NAAA antagonism were confirmed in ex-vivo experiments, within SARS-CoV-2 infected human PBMC cells, in which both viral genomes and TNF- production drop by ~60%. It is known that macrophages contribute to viral spread, excessive inflammation and macrophage activation syndrome that NAAA inhibitors might prevent, reducing the macrophage-induced acute respiratory distress syndrome and subsequent death of COVID-19 patients.

microbiology↗

bioRxiv2021

Metabolic and transcriptomic profiles of glioblastoma invasion revealed by comparisons between patients and corresponding orthotopic xenografts in mice

The invasive behavior of glioblastoma, the most aggressive primary brain tumor, is considered highly relevant for tumor recurrence. However, the invasion zone is difficult to visualize by Magnetic Resonance Imaging (MRI) and is protected by the blood brain barrier, posing a particular challenge for treatment. We report biological features of invasive growth accompanying tumor progression and invasion based on associated metabolic and transcriptomic changes observed in patient derived orthotopic xenografts (PDOX) in the mouse and the corresponding patients tumors. The evolution of metabolic changes, followed in vivo longitudinally by 1H-Magnetic Resonance Spectroscopy (MRS) at ultra-high field, reflected growth and the invasive properties of the human glioblastoma transplanted into the brains of mice (PDOX). Comparison of MRS derived metabolite signatures, reflecting temporal changes of tumor development and invasion in PDOX, revealed high similarity to spatial metabolite signatures of combined multi-voxel MRS analyses sampled across different areas of the patients tumors. Pathway analyses of the transcriptome associated with the metabolite profiles of the PDOX, identified molecular signatures of invasion, comprising extracellular matrix degradation and reorganization, growth factor binding, and vascular remodeling. Specific analysis of expression signatures from the invaded mouse brain, revealed extent of invasion dependent induction of immune response, recapitulating respective signatures observed in glioblastoma. Integrating metabolic profiles and gene expression of highly invasive PDOX provided insights into progression and invasion associated mechanisms of extracellular matrix remodeling that is essential for cell-cell communication and regulation of cellular processes. Structural changes and biochemical properties of the extracellular matrix are of importance for the biological behavior of tumors and may be druggable. Ultra-high field MRS reveals to be suitable for in vivo monitoring of progression in the non-enhancing infiltration zone of glioblastoma.

cancer biology↗

bioRxiv2021

Inhibition of aryl hydrocarbon receptor signaling promotes the terminal differentiation of human erythrocytes

The aryl hydrocarbon receptor (AHR) plays an important role during mammalian embryo development. Inhibition of AHR signaling promotes the development of hematopoietic stem/progenitor cells. AHR also regulates the functional maturation of blood cells, such as T cells and megakaryocytes. However, little is known about the role of AHR modulation during the development of erythroid cells. In this study, we used the AHR antagonist StemRegenin 1 (SR1) and the AHR agonist 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) during different stages of human erythropoiesis to elucidate the function of AHR. We found that antagonizing AHR signaling improved the production of human embryonic stem cell (hESC)-derived erythrocytes and enhanced erythroid terminal differentiation. RNA-sequencing showed that SR1 treatment of proerythroblasts upregulated the expression of erythrocyte differentiation-related genes and downregulated actin organization-associated genes. We found that SR1 promoted F-actin remodeling in terminally differentiated erythrocytes, favoring the maturation of the cytoskeleton and enucleation. We demonstrated that the effects of AHR inhibition on erythroid maturation resulted from an increase in F-actin remodeling. Our findings help uncover the mechanism for AHR-mediated human erythroid cell differentiation. We also provide a new approach toward the large-scale production of functionally mature hPSC-derived erythrocytes for use in translational applications.

cell biology↗

bioRxiv2021

A spatial multi-scale fluorescence microscopy toolbox discloses entry checkpoints of SARS-CoV-2 variants in VeroE6 cells

We exploited a multi-scale microscopy imaging toolbox to address some major issues related to SARS-CoV-2 interactions with host cells. Our approach harnesses both conventional and super-resolution fluorescence microscopy and easily matches the spatial scale of single-virus/cell checkpoints. We deployed this toolbox to characterize subtle issues related to the entry phase of SARS-CoV-2 variants in Vero E6 cells. Our results suggest that in these cells the variant of concern B.1.1.7, (aka Alpha variant), became the predominant circulating variant in several countries by a clear transmission advantage. In fact, in these cells B.1.1.7 outcompetes its ancestor B.1.177 in terms of a much faster kinetics of entry. Given the cell-entry scenario dominated by the endosomal "late pathway", the faster internalization of B.1.1.7 could be directly related to the N501Y mutation in the S protein, which is known to strengthen the binding of Spike receptor binding domain with ACE2. Remarkably, we also directly observed the main role of clathrin as mediator of late-entry endocytosis, reconciling it with the membrane localization of the ACE2 receptor previously attributed to caveolin-enriched rafts. Overall, we believe that our fluorescence microscopy-based approach represents a fertile strategy to investigate the molecular features of SARS-CoV-2 interactions with cells.

biophysics↗

bioRxiv2021

Native structure of the RhopH complex, a key determinant of malaria parasite nutrient acquisition

The RhopH complex is implicated in malaria parasites ability to invade and create new permeability pathways in host erythrocytes, but its mechanisms remain poorly understood. Here we enrich the endogenous RhopH complex in a native soluble form, comprising RhopH2, CLAG3.1 and RhopH3, directly from parasite cell lysates and determine its atomic structure using cryo electron microscopy, mass spectrometry, and the cryoID program. This first direct observation of an exported P. falciparum transmembrane protein--in a soluble, trafficking state and with atomic details of buried putative membrane-insertion helices--offers insights into assembly and trafficking of RhopH and other parasite-derived complexes to the erythrocyte membrane. Our study demonstrates the potential endogenous structural proteomics approach holds for elucidating the molecular mechanisms of hard-to-isolate complexes in their native, functional forms.

biophysics↗