Biology subjects

Acharya, A.

Publications and source records attributed to Acharya, A..

At least 19 recordsLinked to original sources

bioRxiv2026

Profilin-1 Promotes Chromophobe Renal Cell Carcinoma Malignancy

Chromophobe renal cell carcinoma (ChRCC) accounts for 5% of all renal cancer cases. Despite its generally indolent behavior and low mutational burden, there is no targeted therapy for metastatic ChRCC. Profilin-1 (Pfn1), a cytoskeletal regulator of actin and tubulin dynamics, has emerged as a potential oncogenic driver in several cancers including RCC, but its role in ChRCC, remains undefined. We observed elevated Pfn1 expression in stage IV ChRCC patients, implicating Pfn1 in advanced disease progression. To investigate this, we manipulated Pfn1 expressions in two ChRCC cell lines UOK276 and RCJ41M. Pfn1 knockdown (KD) significantly reduced proliferation, invasion, and colony formation, whereas Pfn1 overexpression (OE) in UOK276 enhanced ChRCC aggressive phenotypes. Pharmacological inhibition of Pfn1 significantly suppressed proliferation and clonogenic growth in both cell lines. Additionally, Pfn1 KD increased intracellular ROS accumulation, while overexpressed reduced ROS levels, linking cytoskeletal regulation to oxidative stress control. Together, these findings position Pfn1 as a critical mediator of ChRCC progression, linking cytoskeletal remodeling to aggressive tumor behavior. This work highlights Pfn1 as a potential therapeutic target and establishes a framework for cytoskeletal-focused strategies in advanced ChRCC.

cancer biology↗

bioRxiv2026

Reversing Pathophysiology in Fragile X Syndrome Mice by Promoting PGC-1α and Mitochondrial Functions

Fragile X syndrome (FXS) is the leading cause of intellectual disabilities and autism, but a disease-modifying strategy remains unavailable. Recent studies have suggested reduced mitochondrial functions in FXS. However, the mechanisms underlying mitochondrial defects and their impact on FXS pathophysiology remain largely unclear. Here, we reveal a reduction in the mitochondrial master regulator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1) in the mouse model of FXS, the Fmr1 knockout (KO) mice. We show that this impairment is caused by the inactivity of the transcription factor cAMP-response element-binding protein (CREB) in Fmr1 KO mice. Using the small molecule ZLN005, which induces AMP-activated protein kinase (AMPK)- and CREB-dependent elevation of PGC-1 in Fmr1 KO mice, we observed significantly increased mitochondrial functions and dynamics in cultured neurons in vitro and in the hippocampus in vivo. Furthermore, ZLN005 elicited a wide range of beneficial effects in Fmr1 KO mice, including enhanced inhibitory synaptic transmission, reduced circuit hyperexcitability, improved hippocampal synaptic plasticity, reduced cortical gamma-band oscillations, and improved interhemispheric coherence. Most importantly, we observed improved cognition and reduced autism-like behaviors in ZLN005-treated Fmr1 KO mice. Together, our findings identify AMPK-CREB signaling and PGC-1 as promising and selective therapeutic targets for FXS and reveal the broad impact of restoring PGC-1 on FXS pathophysiology. One Sentence SummaryPromoting PGC-1 Reverses FXS Pathophysiology.

neuroscience↗

bioRxiv2026

Critical roles of MCM8 in meiotic recombination during mouse spermatogenesis

Meiotic DNA double-strand break (DSB) formation and repair by homologous recombination is crucial for ensuring proper chromosome segregation. In mice, the mini-chromosome maintenance family protein, MCM8, has been proposed to function in meiotic recombination and its loss leads to infertility, but the underlying mechanisms are poorly understood. Here we used cytological and genomic assays to infer the role of MCM8 during meiotic recombination in mouse spermatocytes. We show that MCM8-deficient spermatocytes exhibit increased levels of SPO11-dependent DSBs at recombination hotspots during early prophase. DSBs are resected normally and accumulate strand-exchange proteins. However, downstream recombination intermediates are barely detected and recombination intermediate-associated MutSgamma foci do not form efficiently. Consistent with a role in early recombination intermediate processing, MCM8 binds to displacement loop (D-loop) structures in vitro. We propose that MCM8 controls meiotic recombination in at least two ways. MCM8 participates in regulating meiotic DSB number. Further, MCM8 plays a role in the formation and/or stability of post-resection recombination intermediates, steps that are critical for DSB repair via recombination and for efficient synapsis of homologous chromosomes during mouse meiosis.

molecular biology↗

bioRxiv2026

Identification of Key Residues in Allosteric Signaling of Photoactivated Adenylyl Cyclase

Photoactivated adenylyl cyclases (PACs) convert ATP to cyclic AMP (cAMP) through long-range photoinduced allosteric communication between a BLUF domain and a distant adenylyl cyclase (AC) domain. Although photoactivation of the BLUF domain induces only minimal structural changes, it activates a chemical reaction about 4-5 nm away. Here, we combine molecular dynamics simulations, electronic structure calculations, network theory, and machine-learning approaches to investigate photoinduced allostery in the PAC from Beggiatoa sp. (bPAC). We observed that the photoexcitation enables electron transfer from a conserved tyrosine (Tyr7) to the flavin isoalloxazine ring, while the free energy of the electron transfer remains similar across active and inactive mutants. Therefore, photoinduced allosteric activity arises from conformational effects rather than changes in the electronic parameters. Using network theory and eigenvector centrality analysis, we identified residues relevant to allosteric pathways linking the BLUF and AC domains. Furthermore, we used machine-learning (ML) models to distinguish active and inactive conformational states without prior knowledge of functional residues. Remarkably, the ML models identified key regions known from network analysis. Together, these results provide a generalizable frame-work for understanding allosteric pathways in blue-light-sensitive proteins.

biophysics↗

bioRxiv2026

Chemical control of CSA geometry enables relaxation-optimized 19F-13C NMR probes

Fluorine NMR is a powerful tool for probing biomolecular structure and dynamics, yet the performance of 19F probes is fundamentally constrained by rapid transverse relaxation driven by chemical shift anisotropy (CSA). Despite its central role, CSA has largely been treated as an immutable nuclear property rather than a chemically addressable design parameter. Here we demonstrate that the geometry of the CSA tensor - specifically its magnitude, symmetry, and orientation relative to the internuclear dipolar interaction - constitutes a decisive and engineerable determinant of relaxation behavior in coupled 19F-13C spin systems. Guided by electronic-structure calculations and Bloch-Redfield-Wangsness relaxation theory, we establish quantitative design rules that predict when CSA-dipolar interference can be exploited to suppress transverse relaxation. Implementation of these principles in a cysteine-reactive fluoropyrimidine scaffold yields a reporter that supports simultaneous 19F and 13C TROSY optimization, validated by solid-state MAS NMR and protein-based experiments. When incorporated into the 42 kDa maltose binding protein, the probe exhibits exceptionally slow 13C transverse relaxation (R2 {approx} 2-3 s-1) corresponding to linewidths of [~]2 Hz that persist even at apparent molecular weights exceeding 200 kDa. These results recast relaxation optimization as a chemically programmable problem and provide a general framework for the rational design of next-generation NMR probes tailored to large, dynamic, and heterogeneous biomolecular systems.

biophysics↗

bioRxiv2025

STAT1-Mediated Regulation of IL-17A/CEBPB/NF-κB Axisin HIV-1 Infected Human Cerebral Organoids RevealsTherapeutic Targets for Neuroprotection

HIV-associated neurological complications remain a major concern in people living with HIV (PLWH), even under effective viral suppression with combination antiretroviral therapy (cART), underscoring unresolved mechanisms driving HIV-related neurodegeneration. To address this gap, we used HIV-1-infected human cerebral organoids (hCOs) containing microglia as a physiologically relevant three-dimensional model of the central nervous system (CNS) and validated key findings in simian immunodeficiency virus (SIV)-infected, cART-treated rhesus macaque model. Integrating single-nucleus RNA sequencing with ATAC sequencing, we identified cell-type-specific alterations in dual innate immune-driven inflammatory signaling pathways across neural and glial populations. Microglia were preferentially infected and activated, initiating IL-17A-mediated cascades involving IFN-{gamma}/STAT1, CEBPB, and NF-{kappa}B pathways, which converged with cGAS-STING and Notch-NEURL1 signaling, both associated with neuroinflammation and synaptic dysfunction. cART suppressed viral replication, reduced IL-17A-driven neuroinflammation, improved mitochondrial function, and restored synaptic gene expression. Collectively, these findings identify IL-17A, STAT1, CEBPB, and cGAS-STING as key molecular drivers of HIV-associated neuroinflammation and establish a novel mechanistic link between IL-17A signaling and microglial remodeling, providing a translational framework for the development of CNS-targeted therapies in PLWH.

neuroscience↗

bioRxiv2025

EXTRACTION, ISOLATION, PURIFICATION AND OPTIMIZATION OF AMYLASE AND PROTEASE ENZYMES ISOLATED FROM Bacillus species

BackgroundAmylase and protease are two of the most demanded and widely used commercial enzymes. Amylases have many industrial uses: starch conversion (food/bakery industry), sizing agent (textile industry and paper industry), degradation of starchy residue from clothes (detergent industry), conversion of starch to fermentable sugar (fuel industry) etc. Their main source is of microbial origin. About two-third of the industrial enzymes (amylase, protease, cellulose, penicillinase, chitinase, nucleases, esterase, lipase etc.) are produced by Bacillus spp. Among bacteria, Bacillus species are specific producers of extracellular enzymes. ObjectiveThe present work comprised the identification of amylase and protease producing Bacillus spp and exposure of the producers to various parameters for the maximum yield of the enzyme. MethodsTo isolate and identify the amylase and protease producing strain, soil samples were collected from different vegetation from the altitude at 4367.35 feet above sea level. The isolates were screened and various biochemical tests and morphological observations were done to identify the isolates. The enzymes were produced by the submerged state fermentation (SmF) from the isolates and purified by dialysis. Effects of temperature, pH, and different carbon and nitrogen sources of the medium using SmF were optimized. ResultsAmong 95 isolates, 36 were identified. Among the identified isolates, Bacillus subtilis and Bacillus thuringiensis were optimized for the amylase and protease production respectively. The maximum amylase production was found at 42C temperature, in fructose as a carbon sugar, peptone as a nitrogen source and at pH 7. Similarly, the maximum protease production was found at 42C temperature, in sucrose as a carbon sugar, ammonium sulphate as a nitrogen source. The producers inhabited the soil of leguminous plant. ConclusionIn the present study, a natural polymer gelatin is used with the nutrient agar medium to help in cell immobilization for maximum production of alkaline protease by strains of Bacillus. More sophisticated process of purification might yield more enzyme compared to the dialysis in our process that yield 42U/ml/min and 52U/ml/min respectively.

microbiology↗

bioRxiv2025

Plagl1 and Lrrc58 control mammalian body size by triggering target-directed microRNA degradation of miR-322 and miR-503

Precise control of microRNA (miRNA) expression is critical during development. An important mechanism of miRNA regulation is target-directed microRNA degradation (TDMD), a pathway in which the binding of miRNAs to specialized trigger RNAs induces ubiquitylation and decay of associated Argonaute (AGO) proteins by the ZSWIM8 ubiquitin ligase. Concomitant release of miRNAs results in their rapid turnover. ZSWIM8-deficient mice exhibit reduced body size, cardiopulmonary and neurodevelopmental defects, and perinatal lethality. Despite widespread dysregulation of miRNAs in these animals, the vast majority of presumptive trigger RNAs that induce decay of ZSWIM8-regulated miRNAs remain undefined. Here, using AGO crosslinking and sequencing of hybrids (AGO-CLASH), a high-throughput method for identifying miRNA binding sites, we report the identification of Plagl1 as a TDMD trigger for miR-322-5p, and Lrrc58 and Malat1 as TDMD triggers for miR-503-5p in mouse embryonic fibroblasts (MEFs). In mice, deletion of the miR-322-5p and miR-503-5p trigger sites in the Plagl1 and Lrrc58 3' UTRs, respectively, abrogated TDMD of these miRNAs and resulted in miR-322/503-dependent embryonic growth restriction, recapitulating a key feature of the Zswim8--/-- phenotype. Thus, Plagl1 and Lrrc58 act as triggers for degradation of miR-322-5p and miR-503-5p, revealing a noncoding function for these mRNAs as regulators of mammalian body size.

molecular biology↗

bioRxiv2025

Structure-Guided Discovery and Characterization of Novel FLT3 Inhibitors for Acute Myeloid Leukemia Treatment

FLT3 (FMS-like tyrosine kinase 3), a receptor tyrosine kinase, is frequently mutated in acute myeloid leukemia (AML), a hematologic malignancy marked by aggressive proliferation, poor prognosis, and high relapse rates. Although FDA-approved FLT3 inhibitors exist, their clinical efficacy is often undermined by resistance and off-target effects, underscoring the critical necessity for more effective and selective agents. Here, we employed a structure-based computational approach combining pharmacophore screening via Pharmit and the MolPort compound library to identify novel FLT3 inhibitors. Pharmacophore modeling, virtual screening, and docking identified two promising leads, MolPort-002-705-878 and MolPort-007-550-904, with binding affinities of -11.33 and -10.66 kcal/mol, correspondingly. These compounds were further characterized through molecular dynamics (MD) simulations, incorporating Principal Component Analysis (PCA), free energy landscape (FEL) analysis, density functional theory (DFT) calculations, and ADMET profiling. MD results supported the integrity of the FLT3-lead complexes; DFT revealed favorable reactivity, and ADMET predictions indicated drug-likeness with low toxicity, pending experimental confirmation. This integrated in silico pipeline highlights the potential of these molecules as next-generation FLT3 inhibitors and offers a scalable strategy for targeted AML therapeutics.

biochemistry↗

bioRxiv2024

FIGNL1 inhibits homologous recombination in BRCA2 deficient cells by dissociating RAD51 filaments

Homologous recombination (HR) deficiency upon BRCA2 loss arises from defects in the formation of RAD51 nucleoprotein filaments. Here, we demonstrate that loss of the anti-recombinase FIGNL1 retains RAD51 loading at DNA double-stranded breaks (DSBs) in BRCA2-deficient cells, leading to genome stability, HR proficiency, and viability of BRCA2-deficient mouse embryonic stem cells. Mechanistically, we directly show that strand invasion and subsequent HR defects upon BRCA2 loss primarily arises from the unrestricted removal of RAD51 from DSB sites by FIGNL1, rather than from defective RAD51 loading. Furthermore, we identify that the MMS22L-TONSL complex interacts with FIGNL1 and is critical for HR in BRCA2/FIGNL1 double-deficient cells. These findings identify a pathway for tightly regulating RAD51 activity to promote efficient HR, offering insights into mechanisms of chemoresistance in BRCA2-deficient tumors.

genetics↗

bioRxiv2024

TISSUE-SPECIFIC METABOLOMIC REPROGRAMMING DETERMINES THE DISEASE PATHOPHYSIOLOGY OF SARS-COV-2 VARIANTS IN HAMSTER MODEL

Despite significant effort, a clear understanding of host tissue-specific responses and their implications for immunopathogenicity against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant infection has remained poorly defined. To shed light on the interaction between organs and specific SARS-CoV-2 variants, we sought to characterize the complex relationship among acute multisystem manifestations, dysbiosis of the gut microbiota, and the resulting implications for SARS-CoV-2 variant-specific immunopathogenesis in the Golden Syrian Hamster (GSH) model using multi-omics approaches. Our investigation revealed increased viremia in diverse tissues of delta-infected GSH compared to the omicron variant. Multi-omics analyses uncovered distinctive metabolic responses between the delta and omicron variants, with the former demonstrating dysregulation in synaptic transmission proteins associated with neurocognitive disorders. Additionally, delta-infected GSH exhibited an altered fecal microbiota composition, marked by increased inflammation-associated taxa and reduced commensal bacteria compared to the omicron variant. These findings underscore the SARS-CoV-2-mediated tissue insult, characterized by modified host metabolites, neurological protein dysregulation, and gut dysbiosis, highlighting the compromised gut-lung-brain axis during acute infection. TeaserIn hamsters at acute infection, SARS-CoV-2 variant-specific metabolic responses and gut dysbiosis dysregulate synaptic transmission proteins.

systems biology↗

bioRxiv2023

Exponentially decreasing exposure of antigen generates anti-inflammatory T-cell responses

Rheumatoid Arthritis (RA) is a chronic debilitating disease characterized by auto-immune reaction towards self-antigen such as collagen type II. In this study, we investigated the impact of exponentially decreasing levels of antigen exposure on pro-inflammatory T cell responses in the collagen-induced arthritis (CIA) mouse model. Using a controlled delivery experimental approach, we manipulated the collagen type II (CII) antigen concentration presented to the immune system. We observed that exponentially decreasing levels of antigen generated reduced pro-inflammatory T cell responses in secondary lymphoid organs in mice suffering from RA. Specifically, untreated mice exhibited robust pro-inflammatory T cell activation and increased paw inflammation, whereas, mice exposed to exponentially decreasing concentrations of CII demonstrated significantly reduced pro-inflammatory T cell responses, exhibited lower levels of paw inflammation, and decreased arthritis scores in right rear paw. The data also demonstrate that the decreasing antigen levels promoted the induction of regulatory T cells (Tregs), which play a crucial role in maintaining immune tolerance and suppressing excessive inflammatory responses. Our findings highlight the importance of antigen concentration in modulating pro-inflammatory T cell responses in the CIA model. These results provide valuable insights into the potential therapeutic strategies that target antigen presentation to regulate immune responses and mitigate inflammation in rheumatoid arthritis and other autoimmune diseases. Further investigations are warranted to elucidate the specific mechanisms underlying the antigen concentration-dependent modulation of T cell responses and to explore the translational potential of this approach for the development of novel therapeutic interventions in autoimmune disorders.

immunology↗

bioRxiv2023

Target-directed microRNA degradation regulates developmental microRNA expression and embryonic growth in mammals

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutive or conditional deletion of Zswim8, which encodes an essential TDMD factor. Loss of Zswim8 resulted in developmental defects in heart and lung, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD and greatly expanded the known catalog of miRNAs regulated by this pathway. These experiments also uncovered novel features of TDMD-regulated miRNAs, including their enrichment in co-transcribed clusters and examples in which TDMD underlies arm switching, a phenomenon wherein the dominant strand of a miRNA precursor changes in different tissues or conditions. Importantly, deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8 null embryos, directly implicating the TDMD pathway as a regulator of mammalian body size. These data illuminate the broad landscape and developmental role of TDMD in mammals.

molecular biology↗

bioRxiv2023

Mechanism of DNA unwinding by hexameric MCM8-9 in complex with HROB

The human MCM8-9 helicase functions in concert with HROB in the context of homologous recombination, but its precise function is unknown. To gain insights into how HROB regulates MCM8-9, we first used molecular modeling and biochemistry to define their interaction interface. We show that HROB makes important contacts with both MCM8 and MCM9 subunits, which directly promotes its DNA-dependent ATPase and helicase activities. MCM8-9-HROB preferentially binds and unwinds branched DNA structures, and single-molecule experiments reveal a low DNA unwinding processivity. MCM8-9 unwinds DNA as a hexameric complex that assembles from dimers on DNA in the presence of ATP, which is prerequisite for its helicase function. The hexamer formation thus involves two repeating protein-protein interfaces forming between the alternating MCM8 and MCM9 subunits. One of these interfaces is rather stable and forms an obligate heterodimer, while the other interface is labile and mediates the assembly of the hexamer on DNA, independently of HROB. The ATPase site composed of the subunits forming the labile interface disproportionally contributes to DNA unwinding. HROB does not affect the MCM8-9 ring formation, but promotes DNA unwinding downstream by possibly coordinating ATP hydrolysis with structural transitions accompanying translocation of MCM8-9 on DNA.

biochemistry↗

bioRxiv2022

Morphine Suppresses Peripheral Responses and Transforms Brain Myeloid Gene Expression to Favor Neuropathogenesis in SIV Infection

The twin pandemics of opioid abuse and HIV infection can have devastating effects on physiological systems, including on the brain. Our previous work found that morphine increased the viral reservoir in the brains of treated SIV-infected macaques. In this study, we investigated the interaction of morphine and SIV to identify novel host-specific targets using a multimodal approach. We probed systemic parameters and performed single-cell examination of the targets for infection in the brain, microglia and macrophages. Morphine treatment created an immunosuppressive environment, blunting initial responses to infection, which persisted during antiretroviral treatment. Antiretroviral drug concentrations and penetration into the cerebrospinal fluid and brain were unchanged by morphine treatment. Interestingly, the transcriptional signature of both microglia and brain macrophages was transformed to one of a neurodegenerative phenotype. Notably, the expression of osteopontin, a pleiotropic cytokine, was significantly elevated in microglia. This was especially notable in the white matter, which is also dually affected by HIV and opioids. Increased osteopontin expression was linked to numerous HIV neuropathogenic mechanisms, including those that can maintain a viral reservoir. The opioid morphine is detrimental to SIV/HIV infection, especially in the brain.

neuroscience↗

bioRxiv2022

Prevalence Of Multi Drug Resistant Bacteria On Environmental And Medical Device Surfaces Of Korea Nepal Friendship Hospital

The microbial monitoring of environmental and medical-devices surface is used to evaluate efficacy of routine cleaning and disinfection practises and to detect the presence of specific Nosocomial Pathogens. The prevalence of Multidrug Resistance organisms in hospital premises projects serious problems in transmitting to susceptible hosts which is difficult to treat. A cross sectional descriptive research was conducted from December 2016 to June 2017 at the pathology laboratory of Korea Nepal Friendship Hospital (KNFH). A total 140 samples were considered, encompassing the medical devices of the hospital (100), housekeeping surfaces (15) and air (25). Susceptibility test for bacterial isolates was done by disk diffusion assay. Of the total 140 samples taken and analysed, 100% showed growth positivity. In most of the swabs taken, Coagulase Negative Staphylococci was dominant, followed by Staphylococcus aureus, Streptococcus spp. Micrococcus spp., E coli, Pseudomonas spp., Bacillus spp., Acinetobacter spp., Klebsiella spp., Fungi, and least Proteus spp. The dry surfaces were dominantly contaminated by gram positive bacteria whereas moistened surfaces like wash basin were contaminated by gram negative as well as gram positive bacteria. Total 277 strains were exposed to various class of antibiotics, among the gram positive environmental isolates, Coagulase Negative Staphylococci 16 (34.78%) had highest MDR prevalence followed by Staphylococcus aureus 8 (29.62%), Streptococcus spp. 4 (12.90%), Micrococcus spp. 4 (9.30%) and no MDR was shown by any Bacillus spp isolates. Whereas, in case of gram negative, Klebsiella spp. 6 (35.29%) had highest MDR prevalence followed by Acinetobacter spp. 6 (31.57%), E. coli 8 (27.58%), Pseudomonas spp. 4 (18.18%), and lastly Proteus spp. with no MDR at all. The thick dirt covering the cotton swabs and heavy microbial load on them has displayed not only disinfecting practice but also cleaning practice is missing. Heavy contamination shows possible NIs breakout, its important to have routine microbial assessment with standard protocol and find ways to decrease its load.

microbiology↗

bioRxiv2021

Tension-driven multi-scale self-organisation in human iPSC-derived muscle fibers

Human muscle is a hierarchically organised tissue with its contractile cells called myofibers packed into large myofiber bundles. Each myofiber contains periodic myofibrils built by hundreds of contractile sarcomeres that generate large mechanical forces. To better understand the mechanisms that coordinate human muscle morphogenesis from tissue to molecular scales, we adopted a simple in vitro system using induced pluripotent stem cell-derived human myogenic precursors. When grown on an unrestricted two-dimensional substrate, developing myofibers spontaneously align and self-organise into higher-order myofiber bundles, which grow and consolidate to stable sizes. Following a transcriptional boost of sarcomeric components, myofibrils assemble into chains of periodic sarcomeres that emerge across the entire myofiber. By directly probing tension we found that tension build-up precedes sarcomere assembly and increases within each assembling myofibril. Furthermore, we found that myofiber ends stably attach to other myofibers using integrin-based attachments and thus myofiber bundling coincides with stable myofiber bundle attachment in vitro. A failure in stable myofiber attachment results in a collapse of the myofibrils. Overall, our results strongly suggest that mechanical tension across sarcomeric components as well as between differentiating myofibers is key to coordinate the multi-scale self-organisation of muscle morphogenesis.

developmental biology↗

bioRxiv2021

SARS-CoV-2 spike opening dynamics and energetics reveal the individual roles of glycans and their collective impact

The trimeric spike (S) glycoprotein, which protrudes from the SARS-CoV-2 viral envelope, binds to human ACE2, initiated by at least one protomers receptor binding domain (RBD) switching from a "down" (closed) to an "up" (open) state. Here, we used large-scale molecular dynamics simulations and two-dimensional replica exchange umbrella sampling calculations with more than a thousand windows and an aggregate total of 160 {micro}s of simulation to investigate this transition with and without glycans. We find that the glycosylated spike has a higher barrier to opening and also energetically favors the down state over the up state. Analysis of the S-protein opening pathway reveals that glycans at N165 and N122 interfere with hydrogen bonds between the RBD and the N-terminal domain in the up state, while glycans at N165 and N343 can stabilize both the down and up states. Finally we estimate how epitope exposure for several known antibodies changes along the opening path. We find that the BD-368-2 antibodys epitope is continuously exposed, explaining its high efficacy.

biophysics↗