Biology subjects

DasSarma, J.

Publications and source records attributed to DasSarma, J..

4 recordsLinked to original sources

bioRxiv2026

CX3CR1+ microglia/macrophages, activated T cells, and IFN-γ-driven stimulation confer age-dependent protective immunity in young-adult mice following β-coronavirus infection.

Age-dependent variation in the immune response is a critical determinant of host susceptibility, disease severity, and long-term sequelae in coronavirus infections, a principle strikingly demonstrated by the COVID-19 pandemic caused by SARS-CoV-2. Although primarily pneumotropic, coronaviruses carry significant neurotropic potential, driving neurological complications whose severity is profoundly determined by host age. Elderly individuals and often children suffer disproportionately severe disease, whereas young adults relatively mount protective responses; yet the cellular and molecular determinants of this age-dependent neuroprotection remain poorly characterized. Using juvenile and young-adult C57BL/6 mice intracranially inoculated with {beta}-coronavirus MHV-RSA59, a murine equivalent of human coronaviruses, we examined immune dynamics at days 5 (innate-acute), 7 (innate-to-adaptive transition), and 30 (chronic) post-infection. Young-adult mice exhibited only occasional demyelination, in stark contrast to the extensive demyelination observed across all spinal cord levels in juveniles. This differential outcome was attributable to enhanced age-dependent immune maturation, characterized by efficient T cell-microglia/macrophage crosstalk enabling effective viral control by day 7 post-infection. Young adults displayed greater glial activation, heightened cytokine release, CX3CR1+ microglia activation, and augmented CNS trafficking of CX3CR1+ and MHC II+ monocytes/macrophages, IFN-{gamma}+ CD4+/CD8+ T cells, and CXCR3+ effector T cells relative to juveniles. Reduced naive T cell frequencies and elevated effector/central memory T cell populations in cervical lymph nodes further indicate a robust adaptive memory response conferring long-term protection. Additionally, greater regulatory T cell accumulation in young adults facilitates timely suppression of excessive neuroinflammation as viral burden subsides. Together, these findings define the age-dependent immune landscape that underpins neuroprotection in {beta}-coronavirus infection.

immunology↗

bioRxiv2024

TGFb-ANGPT2-Tie2 axis in cancer-associated fibroblasts reprograms oral cancer cells to embryonic-like cell state with predictive significance of poor prognosis

Myofibroblastic cancer-associated fibroblasts (CAFs) in tumor stroma is identified as poor-prognostic indicator in oral cancer; however, biological mechanisms are largely unexplored. Here, we discovered the role of autocrine or exogenous transforming growth factor beta (TGF{beta}) in inducing Tunica Interna Endothelial cell kinase 2 (Tie2) -signaling through histone deacetylase-mediated downregulation of Tie2-antagonist, Angiopoietin-2 in CAFs, responsible for induction and maintenance of myofibroblastic differentiation. To understand the influence of CAF-specific Tie2-signaling on cancer cell properties, we performed CAF-Cancer cell co-culture and its single-cell RNA sequencing (scRNA-Seq). Distinct clustering of CAFs suggested their transcriptional heterogeneity, driven by TGF{beta}-Tie2 activation. Interestingly, CAF-specific Tie2-signaling was responsible to reprogram cancer cells, producing embryonic-like cell state with increased stemness and EMT signatures. Importantly, both the Tie2-specific gene expression signature as well as reprogrammed cancer cell specific gene expression modules were validated respectively in fibroblasts clusters and malignant cell clusters in two independent earlier reported scRNAseq studies of HNSCC tumors. Highlighting the translatability of our study, the gene expression signature derived from reprogrammed cancer cells showed significant association with poor prognosis in HNSCC patient of TCGA cohort. Pharmacological inhibition of Tie2-signaling in CAFs, significantly abrogated the tumor initiating ability of co-cultured oral cancer cell lines. Overall, combining our molecular and computational analysis, we may propose Tie2 as a novel factor responsible for CAF mediated cancer cell plasticity, associated with aggressive nature of oral cancer. TeaserTie2-signaling is activated in myofibroblasts which impacts the behaviour of malignant cells by inducing cancer cell plasticity to acquire stemness.

cancer 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↗

bioRxiv2020

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in murine coronavirus-induced neuroinflammation

Mouse hepatitis virus (MHV) belongs to the same beta-coronavirus family as SARS-CoV-2, MERS-CoV, and SARS-CoV. Studies have shown the requirement of host cellular proteases for priming the surface spike protein during viral entry and transmission in coronaviruses. The metzincin family of metal-dependent endopeptidases called matrix metalloproteinases (MMPs) is involved in virus encephalitis, enhanced blood-brain barrier permeability, or cell-to-cell fusion upon viral infection. Here we show the role of MMPs as mediators of virus-induced host neuroinflammatory response in the MHV model. Infection of mice with wild-type MHV-A59 or its isogenic recombinant strains, RSA59 or RSMHV2 significantly upregulated MMP-3, MMP-8, and MMP-14 transcript levels. Functional network assessment with Ingenuity Pathway Analysis revealed a direct involvement of these MMPs in disrupting junctional assembly between endothelial cells via interaction with junctional adhesion molecules and thereby facilitating transmigration of peripheral lymphocytes. Our findings also suggest mRNA upregulation of Park7, which is involved in NADPH oxidase-dependent ROS production, following RSA59 infection. RSA59 infection resulted in elevated mRNA levels of RelA, a subunit of NF-{kappa}B. Infection with MHV-A59 is known to generate ROS, and oxidative stress can activate NF-{kappa}B. Thus, our findings indicate the existence of a possible nexus between ROS, NF-{kappa}B, and MMPs in RSA59-induced neuroinflammation. We also assessed the expression of endogenously produced regulators of MMP activities. Elevated mRNA and protein levels of tissue inhibitors of metalloproteinases 1 (TIMP-1) in MHV-A59 infection are suggestive of a TIMP-1 mediated host antiviral response. ImportanceThe newly emergent coronavirus has brought the world to a near standstill. In the past, studies have focused on the function of host proteases in virus attachment and entry. Our research indicates the involvement of a group of metal-dependent host proteases in inflammation associated with coronavirus infection. Inflammation is the first response of the host to virus infection. While it helps in restricting the spread and clearance of viral particles, uncontrolled inflammation results in several inflammatory consequences. Therefore, it becomes vital to limit unchecked host immune response. The inhibition of specific metalloproteases represents a potential new therapeutic approach in coronavirus infection and disease outcome.

microbiology↗