Biology subjects

Das, J.

Publications and source records attributed to Das, J..

At least 55 records · Page 3Linked to original sources

bioRxiv2024

Altered AP-1, RUNX, and EGR chromatin dynamics drive fibrotic lung disease

Pulmonary fibrosis, including systemic sclerosis-associated interstitial lung disease (SSc-ILD), involves myofibroblasts and SPP1hi macrophages as drivers of fibrosis. Single-cell RNA sequencing has delineated fibroblast and macrophages transcriptomes, but limited insight into transcriptional control of profibrotic gene programs. To address this challenge, we analyzed multiomic snATAC/snRNA-seq on explanted SSc-ILD and donor control lungs. The neural network tool ChromBPNet inferred increased TF binding at single base pair resolution to profibrotic genes, including CTHRC1 and ADAM12, in fibroblasts and SPP1 and CCL18 in macrophages. The novel algorithm HALO confirmed AP-1, RUNX, and EGR TF activity controlling profibrotic gene programs and established TF-regulatory element-gene networks. This TF action atlas provides comprehensive insights into the transcriptional regulation of fibroblasts and macrophages in healthy and fibrotic human lungs.

systems biology↗

bioRxiv2024

Relative stability of different conformations and pathways of ligand escape in LIV-binding protein: A molecular dynamics simulation study

Periplasmic binding proteins (PBPs) are a large family of receptors and transporters, present in gram-negative bacteria, which play a pivotal role in transport, chemotaxis and quorum sensing. These class of proteins have a distinct two domain architecture that undergo large conformational transitions through a hinge motion. In particular, Leucine-Isoleucine-Valine (LIV) binding protein can sense these specific side chains and undergoes a transition from a open to a closed conformation which is traditionally viewed as ligand induced conformational change. Here, atomistic molecular dynamics simulations and well-tempered metadynamics simulations are used to understand the role of ligand (namely, Isoleucine) in the conformational transition/selection of the LIV-binding protein. Furthermore, the pathway, energetics, and sequence of events during ligand escape/unbinding are unveiled from a microscopic perspective. Two distinct ligand binding pathways are identified: (i) domain separation followed by ligand escape, and (ii) ligand escape either followed by or synchronous with domain separation. The former is found to be energetically more favorable. Water is found to play an important role in the ligand unbinding process as well as providing stability to the closed conformation in the absence of the ligand, by forming bridging hydrogen bonds between two domains.

biophysics↗

bioRxiv2024

Intra-cluster receptor density (IRD) dictates TNFR1 clusters' signaling efficacy

Tumor Necrosis Factor Receptor 1 (TNFR1) signaling regulates cell fate in inflammation, immune responses, and tumorigenesis. While TNF--mediated TNFR1 pathways are well known, the role of receptor clustering remains unclear. Utilizing homo-FRET using fluorescence anisotropy, we show that intra-cluster receptor density (IRD) governs TNFR1 signaling outcomes. Soluble TNF- (sTNF-) increases IRD at cluster cores but decreases it at rims via receptor reorganization. Reducing IRD through membrane tension, zafirlukast, actin depolymerization, or cholesterol depletion suppresses sTNF- signaling, whereas increasing IRD by lowering membrane tension or exposing cells in a 3D gel-like microenvironment triggers ligand-independent activation. These findings reveal IRD as a key regulator of receptor signaling, with potential relevance across related receptor families and innovative strategies in modulating TNFR1 signaling. TeaserIntra-cluster receptor density (IRD) is critical for TNFR1 signal modulation, with higher IRD activating and lower IRD impairing the TNFR1 signaling.

biophysics↗

bioRxiv2024

Spleen Tyrosine Kinase (SYK) negatively regulates ITAM-mediated human NK cell signaling and CD19-CAR NK cell efficacy

NK cells express activating receptors that signal through ITAM-bearing adapter proteins. The phosphorylation of each ITAM creates binding sites for SYK and ZAP70 protein tyrosine kinases to propagate downstream signaling including the induction of Ca2+ influx. While all immature and mature human NK cells co-express SYK and ZAP70, clonally driven memory or adaptive NK cells can methylate SYK genes and signaling is mediated exclusively using ZAP70. Here, we examined the role of SYK and ZAP70 in a clonal human NK cell line KHYG1 by CRISPR-based deletion using a combination of experiments and mechanistic computational modeling. Elimination of SYK resulted in more robust Ca++ influx after cross-linking of the CD16 and NKp30 receptors and enhanced phosphorylation of downstream proteins, whereas ZAP70 deletion diminished these responses. By contrast, ZAP70 depletion increased proliferation of the NK cells. As immature T cells express both SYK and ZAP70 but mature T cells often express only ZAP70, we transduced the human Jurkat cell line with SYK and found that expression of SYK increased proliferation but diminished TCR-induced Ca2+ flux and activation. We performed transcriptional analysis of the matched sets of variant Jurkat and KHYG1 cells and observed profound alterations caused by SYK expression. As depletion of SYK in NK cells increased their activation, primary human NK cells were transduced with a CD19-targeting CAR and were CRISPR edited to ablate SYK or ZAP70. Deletion of SYK resulted in more robust cytotoxic activity and cytokine production, providing a new therapeutic strategy of NK cell engineering for cancer immunotherapy.

immunology↗

bioRxiv2024

Role of VapBC4 toxin-antitoxin system of Sulfolobus acidocaldarius in heat stress adaptation

Toxin-antitoxin (TA) systems are important for stress adaptation in prokaryotes, including persistence, antibiotic resistance, pathogenicity, and biofilm formation. Toxins can cause cell death, reversible growth stasis, and direct inhibition of crucial cellular processes through various mechanisms, while antitoxins neutralize the effects of toxins. In bacteria, these systems have been studied in detail, whereas their function in archaea remains elusive. During heat stress, the thermoacidophilic archaeon Sulfolobus acidocaldarius exhibited an increase in the expression of several bicistronic type II vapBC TA systems, with the highest expression observed in the vapBC4 system. In the current study, we performed a comprehensive biochemical characterization of the VapBC4 TA system, establishing it as a bonafide type II toxin-antitoxin system. The VapC4 toxin is shown to have high-temperature catalyzed RNase activity specific for mRNA and rRNA, while the VapB4 antitoxin inhibits the toxic activity of VapC4 by interacting with it. VapC4 toxin expression led to heat-induced persister-like cell formation, allowing the cell to cope with the stress. Furthermore, this study explored the impact of vapBC4 deletion on biofilm formation, whereby deletion of vapC4 led to increased biofilm formation, suggesting its role in regulating biofilm formation. Thus, during heat stress, the liberated VapC4 toxin in cells could potentially signal a preference for persister cell formation over biofilm growth. Thus, our findings shed light on the diverse roles of the VapC4 toxin in inhibiting translation, inducing persister cell formation, and regulating biofilm formation in S. acidocaldarius, enhancing our understanding of TA systems in archaea. IMPORTANCEThis research enhances our knowledge of Toxin-antitoxin (TA) systems in archaea, specifically in the thermoacidophilic archaeon Sulfolobus acidocaldarius. TA systems are widespread in both bacterial and archaeal genomes, indicating their evolutionary importance. However, their exact functions in archaeal cellular physiology are still not well understood. This study sheds light on the complex roles of TA systems and their critical involvement in archaeal stress adaptation, including persistence and biofilm formation. By focusing on S. acidocaldarius, which lives in habitats with fluctuating temperatures that can reach up to 90, the study reveals the unique challenges and survival mechanisms of this organism. The detailed biochemical analysis of the VapBC4 TA system, and its crucial role during heat stress, provides insights into how extremophiles can survive in harsh conditions. The findings of this study show the various functions of the VapC4 toxin, including inhibiting translation, inducing persister-like cell formation, and regulating biofilm formation. This knowledge improves our understanding of TA systems in thermoacidophiles and has broader implications for understanding how microorganisms adapt to extreme environments.

microbiology↗

bioRxiv2024

Self-Assembled Monolayer Transporters Enable Reagentless Analysis of Small Molecule Analytes

The detection of small molecules beyond glucose remains an ongoing challenge in the field of biomolecular sensing owing to their small size, diverse structures, and lack of alternative non-enzymatic sensing methods. Here, we present a new reagentless electrochemical approach for small molecule detection that involves directed movement of electroactive analytes through a self-assembled monolayer to an electrode surface. Using this method, we demonstrate detection of several physiologically relevant small molecules as well as the capacity for the system to operate in several biological fluids. We anticipate that this mechanism will further improve our capacity for small molecule measurement and provide a new generalizable monolayer-based technique for electrochemical assessment of various electroactive analytes.

bioengineering↗

bioRxiv2024

Sliding Window INteraction Grammar (SWING): a generalized interaction language model for peptide and protein interactions

The explosion of sequence data has allowed the rapid growth of protein language models (pLMs). pLMs have now been employed in many frameworks including variant-effect and peptide-specificity prediction. Traditionally, for protein-protein or peptide-protein interactions (PPIs), corresponding sequences are either co-embedded followed by post-hoc integration or the sequences are concatenated prior to embedding. Interestingly, no method utilizes a language representation of the interaction itself. We developed an interaction LM (iLM), which uses a novel language to represent interactions between protein/peptide sequences. Sliding Window Interaction Grammar (SWING) leverages differences in amino acid properties to generate an interaction vocabulary. This vocabulary is the input into a LM followed by a supervised prediction step where the LMs representations are used as features. SWING was first applied to predicting peptide:MHC (pMHC) interactions. SWING was not only successful at generating Class I and Class II models that have comparable prediction to state-of-the-art approaches, but the unique Mixed Class model was also successful at jointly predicting both classes. Further, the SWING model trained only on Class I alleles was predictive for Class II, a complex prediction task not attempted by any existing approach. For de novo data, using only Class I or Class II data, SWING also accurately predicted Class II pMHC interactions in murine models of SLE (MRL/lpr model) and T1D (NOD model), that were validated experimentally. To further evaluate SWINGs generalizability, we tested its ability to predict the disruption of specific protein-protein interactions by missense mutations. Although modern methods like AlphaMissense and ESM1b can predict interfaces and variant effects/pathogenicity per mutation, they are unable to predict interaction-specific disruptions. SWING was successful at accurately predicting the impact of both Mendelian mutations and population variants on PPIs. This is the first generalizable approach that can accurately predict interaction-specific disruptions by missense mutations with only sequence information. Overall, SWING is a first-in-class generalizable zero-shot iLM that learns the language of PPIs.

systems biology↗

bioRxiv2024

Altered DNA methylation pattern contributes to differential epigenetic immune signaling in the upper respiratory airway of COVID-19 patients

The emergence of SARS-CoV-2 has had a profound adverse impact on global health and continues to remain a threat worldwide. The disease spectrum of COVID-19 ranges from asymptomatic to fatal clinical outcomes especially in the elderly population and in individuals with underlying medical conditions. The impact of COVID-19 on host immune responses and immune cells at the protein and DNA levels remains largely ambiguous. In a case-control study, here we explored the impact of COVID-19 on DNA methylation patterns in the upper respiratory airway to determine how SARS-CoV-2 infection altered the immune status of individuals requiring hospitalization for COVID-19. We performed DNA methylation arrays on nasopharyngeal swabs at inclusion/hospitalization as well as 6 weeks post-inclusion. Our study reveals a distinct DNA methylation pattern in COVID-19 patients compared to healthy controls, characterized by 317 779 differentially methylated CpGs. Notably, within the transcription start sites and gene body, COVID-19 patients exhibited a higher number of genes/CpGs with elevated methylation levels. Enrichment analysis of methylated genes at transcription start sites highlighted the impact on genes associated with inflammatory responses and immune functions. Some SARS-CoV-2 -induced CpG methylations were transient, returning to normal levels by 6 weeks post-inclusion. Enriched genes of interest included IL-17A, a pivotal cytokine implicated with inflammation and healing, and NUP93, associated with antiviral innate immunity. Further, six genes in our data set, OAS1, CXCR5, APP, CCL20, CNR2, and C3AR1, were found in enrichment analysis with previous COVID-19 studies. Additionally, RNAse1 and RNAse2 emerged as key regulators, while IL-18 played a role in various biological processes in COVID-19 patients. Overall, our results demonstrates that COVID-19 has a major impact on the upper airway by modifying the methylation pattern of many genes and this could have implications for the conditioning of the airways and how the individual response to future airway infections.

microbiology↗

bioRxiv2024

Experimental type 1 diabetes metabolically rejuvenates CD8+ T cells for improved control of tumor growth through an IGF1-IGF1R axis

AbstractEpidemiological studies suggest that patients with pre-existing type 1 diabetes (T1D) have a decreased risk of developing melanoma, prostate cancer, and breast cancer, although the underlying mechanism remains to be elucidated. In translational modelling, we observed that streptozotocin (STZ) induced T1D mice exhibited restricted melanoma and carcinoma (mammary, lung and colon) growth in association with extended overall survival. Tumor-infiltrating CD8+ T cells were found to be responsible for tumor growth restriction. Tumor infiltrating CD8+ T cells but not tumor cells themselves exhibited higher glycolytic and cytotoxic activities in T1D hosts. Such improved anti-tumor T cell function was linked to selective upregulated expression of insulin-like growth factor 1, insulin-like growth factor 1 receptor, and phospho-mTOR in CD8+ T cells in the TME. T1D patient derived CD8+ T cells displayed superior activation in vitro after tumor antigen stimulation vs. non-diabetic CD8+ T cells. Activation of T1D patient derived CD8+ T cells was sensitive to targeted antagonism of IGF1R and mTOR, supporting the operational involvement of the IGF1R-mTOR signaling axis. Our results suggest that selective activation of the intrinsic IGF1R-mTOR signaling axis in CD8+ T cells represents a preferred endpoint to achieving more effective immunotherapy outcomes and improved cancer patient management. SignificanceExperimental type 1 diabetes decelerates tumor growth through metabolic activation of cytotoxic T cells dependent on an IGF1R-mTOR signaling pathway. CD8+IGF1R+IGF1+ T cells play a crucial role in T1D dependent tumor control.

cancer biology↗

bioRxiv2024

The Northern Colours: Isolation and Characterisation of 4 Pigment-Producing Bacteria from the Arctic

Due to the adverse effects of synthetic colours on human health and the environment, there is a rapid shift towards the use of colours from natural sources like plants and microorganisms. Many pigment-producing microorganisms are identified and isolated from extreme environments like glaciers, ice cores, marine surface waters, etc. In this study, we have isolated 4 distinct pigment-producing bacterial strains from an Arctic stone sample collected from the vicinity of the Indian Research Station Himadri (78{degrees}55'N 11{degrees}56'E), located at the International Arctic Research Base, Ny[A]lesund, Svalbard, Norway. Pigment production was optimised by identifying the right growth medium, temperature, pH, and incubation period. The morphological, cultural, and biochemical characteristics were identified using several experiments like Gram Staining, Catalase Test, Oxydative-Fermentative Test, etc. The objective of this study is to identify novel bacterial strains capable of producing distinct pigments for pharmaceutical and industrial applications.

microbiology↗

bioRxiv2024

Impact of IL-21 on Natural Killer cell proliferation and Function - a mathematical and functional assessment

Natural killer (NK) cells are currently in use as immunotherapeutic agents for cancer. Many different cytokines are used to generate NK cells including IL-2, IL-12, IL-15 and IL-18 in solution and membrane bound IL-21. These cytokines drive NK cell activation through the integration of STAT and NF-{kappa}B pathways, which overlap and synergize, making it challenging to predict optimal cytokine combinations. We integrated functional assays for NK cells cultured in a variety of cytokine combinations with feature selection and mechanistic regression models. Our regression model successfully predicts NK cell proliferation for different cytokine combinations and indicates synergy between STAT3 and NF-{kappa}B transcription factors. Use of IL-21 in solution in the priming, but not post-priming phase of NK cell culture resulted in optimal NK cell proliferation, without compromising cytotoxicity or IFN-{gamma} secretion against hepatocellular carcinoma cell lines. Our work provides a mathematical framework for interrogating NK cell activation for cancer immunotherapy.

immunology↗

bioRxiv2023

Does novelty influence foraging decision of a scavenger?

Acquiring knowledge about the environment is crucial for survival. Animals, often driven by their explorative tendencies, gather valuable information regarding food resources, shelter, mating partners, etc. While neophilia, or the preference for novel environmental stimuli or objects, can promote exploratory behaviour, neophobia, or avoidance of novel environmental stimuli, can constrain such behaviour. Neophobia can reduce predation risk, yet decreased exploratory behaviour resulting from it may limit the ability to discover potentially highly rewarding resources. Dogs (Canis familiaris) living in semi-urban and urban environments as free-ranging populations are, although subject to various selection forces, typically have negligible predation pressure. These dogs are scavengers in human-dominated environments; thus, selection against object-neophobia can provide benefits when searching for novel food resources. Although pet and captive pack-living dogs are known to exhibit neophilia when provided with novel objects, little is known about free-ranging dogs behavioural responses to novel objects, particularly in foraging contexts. Using an object choice experiment, we tested 274 free-ranging dogs from two age classes, adult and juvenile, to investigate their object-neophobia in a scavenging context. We employed a betweensubject study design, providing dogs with a familiar and a potentially novel object, both baited with equal but (partially)hidden food rewards. Adult and juvenile dogs significantly inspected the novel object first compared to the familiar one, even when we reduced the visual obscurity of the familiar object, i.e., when the hidden food reward was partially visible. Furthermore, novel objects with varying strengths of olfactory cues (baited vs. false-baited) were inspected comparably by adults and juveniles. No significant differences were found in the latencies to inspect the objects. These results indicate that free-ranging dogs, evidently from an early ontogenic phase, do not show object-neophobia, as demonstrated by their preference for novel over familiar food sources. We conclude that little to no constraint of neophobia on exploratory behaviour, yet selection for object-neophilia in semi-urban and urban-dwelling animals can guide foraging decision-making processes, providing adaptive benefits.

animal behavior and cognition↗

bioRxiv2023

Spatial organization and stochastic fluctuations of immune cells impact clinical responsiveness to immune checkpoint inhibitors in patients with melanoma

High-dimensional, spatial single-cell technologies such as CyTOF imaging mass cytometry (IMC) provide detailed information regarding locations of a large variety of cancer and immune cells in microscopic scales in tumor microarray (TMA) slides obtained from patients prior to immune checkpoint inhibitor (ICI) therapy. An important question is how the initial spatial organization of these cells in the tumor microenvironment (TME) change with time, regulate tumor growth and eventually outcomes as patients undergo ICI therapy. Utilizing IMC data of melanomas of patients who later underwent ICI therapy, we develop a spatially resolved interacting cell systems model that is calibrated against patient response data to address the above question. We find that the tumor fate in these patients is determined by the spatial organization of activated CD8+ T cells, macrophages, and melanoma cells and the interplay between these cells that regulate exhaustion of CD8+ T cells. We find that fencing of tumor cell boundaries by exhausted CD8+T cells is dynamically generated from the initial conditions that can play a pro-tumor role. Furthermore, we find that specific spatial features such as co-clustering of activated CD8+ T cells and macrophages in the pre-treatment samples determine the fate of the tumor progression, despite stochastic fluctuations and changes over the treatment course. Our framework enables determination of mechanisms of interplay between a key subset of tumor and immune cells in the TME that regulate clinical response to ICIs. SignificanceRecent advances in single cell technologies allows for spatial imaging a wide variety of cancer and immune cells in tissue samples obtained from solid tumors. This detailed snapshot data of microscale organization of tumor and immune cells could provide valuable insights into underlying biology and clinical responsiveness to cancer immunotherapy. By combining published data from imaging mass-cytometry and patient response against ICI drugs with data analysis rooted in statistical physics and statistical inference theory, we developed and studied the dynamics of mechanistic spatially resolved models: we show that tumor growth during ICI treatment is regulated by non-intuitive interplay between CD8+ T cells and tumor associated macrophages, formation of a pro-tumor fencing of exhausted CD8+ T cells around melanoma cells, specific features of spatial organization of these cells prior to treatment, and stochastic fluctuations in the dynamics. The mechanisms unveiled in our studies are general and can pertain to the response of other solid tumors to ICI therapy.

immunology↗

bioRxiv2023

From the Wild to the City: How Domestication and Urbanization Reshape Animal Gut Microbiome

This review explores the profound effects of domestication and urbanization on the gut microbiota of animals. It delves into the complex interplay between these two processes and their transformative impact on the microorganisms residing in the gastrointestinal tracts of a wide range of species. Domestication, the centuries-old practice of taming and breeding animals for human use, has led to significant shifts in the gut microbiomes of domesticated animals. This shift is a result of altered diets, living conditions, and reduced exposure to natural environments. The paper examines the consequences of these changes on animal health, behavior, and their adaptation to domestic life. Conversely, urbanization, characterized by the rapid expansion of cities and human habitats, has driven wild animals to adapt to urban environments. This review investigates how the urban landscape, pollution, and dietary changes reshape the gut microbiomes of urban wildlife. It explores the potential implications of these alterations on the animals resilience to urban stressors and disease. Drawing parallels between domestication and urbanization, the paper reveals intriguing similarities and differences in gut microbiome transformations across various species. It also assesses the broader implications of these shifts on ecological dynamics, zoonotic disease transmission, and the potential for microbial interactions between domesticated animals, urban wildlife, and humans. Ultimately, this review consolidates current knowledge on the topic, shedding light on the shared mechanisms and unique adaptations that drive microbial changes in animals undergoing domestication and those adapting to urban environments. It concludes with a discussion of the implications for animal conservation, animal-human interactions, and the One Health perspective, emphasizing the importance of understanding these intricate icrobial relationships in our ever-changing world. By enhancing our comprehension of these complex dynamics, this paper contributes to the growing body of knowledge that informs our coexistence with the animals we share our lives and cities with, highlighting the critical role of gut microbiota in these processes.

ecology↗

bioRxiv2023

Clonal stochasticity in early NK cell response to mouse cytomegalovirus is generated by mature subsets of varying proliferative ability

Natural killer (NK) cells are classically defined as innate immune cells, but experiments show that mouse cytomegalovirus (MCMV) infection in C57BL/6 mice can cause NK cells to undergo antigen-specific proliferation and memory formation, similar to adaptive CD8+ T cells. One shared behavior between CD8+ T cells and NK cells is clonal expansion, where a single stimulated cell proliferates rapidly to form a diverse population of cells. For example, clones derived from single cells are most abundant during expansion when they are primarily CD27- for NK cells and CD62L- for T cells, phenotypes derived from precursor CD27+ and CD62L+ cells, respectively. Here we determined the mechanistic rules involving proliferation, cell death, and differentiation of endogenous and adoptively transferred NK cells in the expansion phase of the response to MCMV infection. We found that the interplay between cell proliferation and cell death of mature CD27- NK cells and a highly proliferative CD27-Ly6C- mature subtype and intrinsic stochastic fluctuations in these processes play key roles in regulating the heterogeneity and population of the NK cell subtypes. Furthermore, we estimate rates for maturation of endogenous NK cells in homeostasis and in MCMV infection and found that only NK cell growth rates, and not differentiation rates, are appreciably increased by MCMV. Taken together, these results quantify the differences between the kinetics of NK cell antigen-specific expansion from that of CD8+ T cells and unique mechanisms that give rise to the observed heterogeneity in NK cell clones generated from single NK cells in the expansion phase.

immunology↗

bioRxiv2023

Temporal dynamics and genomic programming of plasma cell fates

Affinity-matured plasma cells (PCs) of varying lifespans are generated through a germinal center (GC) response. The developmental dynamics and genomic programs of antigen-specific PC precursors remain to be elucidated. Using a model antigen, we demonstrate biphasic generation of PC precursors, with those generating long-lived bone marrow PCs preferentially produced in the late phase of GC response. Clonal tracing using scRNA-seq+BCR-seq in spleen and bone marrow compartments, coupled with adoptive transfer experiments, reveal a novel PC transition state that gives rise to functionally competent PC precursors. The latter undergo clonal expansion, dependent on inducible expression of TIGIT. We propose a model for the proliferation and programming of precursors of long-lived PCs, based on extended antigen encounters followed by reduced antigen availability.

immunology↗

bioRxiv2023

An inimitable proprotein convertase subtilisin kexin-9 (PCSK9) cleavage site VFAQ on Spike protein along with furin cleavage site makes SARS-CoV-2 unique

A novel coronavirus (2019-nCoV) or Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) that affects humans has been discovered in Wuhan, China, in 2019. Its genome has been sequenced, and the genetic data was quickly made public. We discovered a novel proprotein convertase subtilisin kexin-9 (PCSK9) cleavage site in the Spike protein of the 2019-nCoV. The recent research also demonstrates that the previously found proprotein convertase 3 (PC3) or furin cleavage site, which was assumed to be unique, is already present in animal corona viruses. In this article, we suggest that the combination of the both proprotein convertase PC3 cleavage site and the PCSK9 site renders SARS-CoV-2 unique in terms of the pathogenicity, potential functional effects, and implications for the development of antiviral drugs.

evolutionary biology↗

bioRxiv2023

Connexin 43 mediated collective cell migration is independent of Golgi orientation

Cell migration is vital for multiple physiological functions and is involved in the metastatic dissemination of tumour cells in various cancers. For effective directional migration, cells often reorient their secretory traffic towards the leading edge by reorienting the Golgi apparatus. However, conflicting results on the positioning of the Golgi relative to the migrating cell raise questions about its regulation. Herein, we address the role of gap junction protein Connexin 43, which connects cells allowing the direct exchange of molecules and also controls the distribution of microtubules. We utilized HeLa WT (wild-type cells lacking Connexin 43) and HeLa 43 cells (stably expressing Connexin 43). We found that functional Connexin 43 channels affected Golgi morphology and reduced the ability of reorientation of Golgi (towards the leading edge) during cell migration. Although Connexin 43 also reduced migration velocity, the front displayed enhanced coherence in movement, implying an augmented collective nature of migration compared to HeLa WT cells lacking the cell-cell connectivity evidenced in HeLa 43. The increase in vimentin and basal actin in HeLa 43 shows that Connexin 43 expression alters the cytoskeleton. Non-invasive measurement of basal membrane height fluctuations revealed that HeLa 43 had a lower membrane tension and a more uniform intra- and inter-cellular distribution than HeLa WT, similar to their coherence in migration. We, therefore, propose that the reduced Golgi reorientation in HeLa 43 might be linked to lesser dependence on directed secretory trafficking, which is believed to be required to buffer the increasing tension caused by migration.

biophysics↗