Exploring the role of mechanical cues in T cell function

T lymphocytes are constantly subjected to mechanical cues from their microenvironment. The past few decades have seen a significant development in scientific research concerning the crucial role of biophysical forces in governing various T lymphocyte-mediated processes. Mounting research have confirmed that T lymphocyte activation is critically dependent on its capacity to sense and respond to mechanical forces which are generated during its interaction with cellular partners and with its microenvironment. Despite extensive research on the role of mechanical forces on T lymphocyte biology, no dedicated T lymphocyte-intrinsic mechanosensory module was identified until recently. In the following thesis, I have described the role of Piezo1 mechanosensors in T lymphocyte function, particularly in the contexts of T lymphocyte activation and migration. Upon interaction with cognate antigen presenting cells (APCs), T lymphocytes experience significant mechanical force which activates Piezo1 channels. Activated Piezo1 allows influx of extracellular calcium which triggers calpain-dependent polymerisation and remodelling of the actin cytoskeletal scaffold. This event is crucial for formation and stabilisation of the T cell-APC immunological synapse, thereby facilitating optimal T lymphocyte activation. Moreover, Piezo1-mediated mechanotransduction also plays a critical role in T lymphocyte chemotactic migration. Downregulation of Piezo1 resulted in dramatically impaired motility of T lymphocytes in response to stimulus. Thus, we have identified a previously unknown pathway of Piezo1- mediated mechanoregulation of T lymphocyte function

RNA editing in host lncRNAs as potential modulator in SARS-CoV-2 variants-host immune response dynamics

Summary: Both host and viral RNA editing plays a crucial role in host’s response to infection, yet our understanding of host RNA editing remains limited. In this study of in-house generated RNA sequencing (RNA-seq) data of 211 hospitalized COVID-19 patients with PreVOC, Delta, and Omicron variants, we observed a significant differential editing frequency and patterns in long non-coding RNAs (lncRNAs), with Delta group displaying lower RNA editing compared to PreVOC/Omicron patients. Notably, multiple transcripts of UGDH-AS1 and NEAT1 exhibited high editing frequencies. Expression of ADAR1/APOBEC3A/APOBEC3G and differential abundance of repeats were possible modulators of differential editing across patient groups. We observed a shift in crucial infection-related pathways wherein the pathways were downregulated in Delta compared to PreVOC and Omicron. Our genomics-based evidence suggests that lncRNA editing influences stability, miRNA binding, and expression of both lncRNA and target genes. Overall, the study highlights the role of lncRNAs and how editing within host lncRNAs modulates the disease severity

Piezo1 mechanosensing regulates integrin-dependent chemotactic migration in human T cells

T cells are crucial for efficient antigen-specific immune responses and thus their migration within the body, to inflamed tissues from circulating blood or to secondary lymphoid organs, plays a very critical role. T cell extravasation in inflamed tissues depends on chemotactic cues and interaction between endothelial adhesion molecules and cellular integrins. A migrating T cell is expected to sense diverse external and membrane-intrinsic mechano-physical cues, but molecular mechanisms of such mechanosensing in cell migration are not established. We explored if the professional mechanosensor Piezo1 plays any role during integrin-dependent chemotaxis of human T cells. We found that deficiency of Piezo1 in human T cells interfered with integrin-dependent cellular motility on ICAM-1-coated surface. Piezo1 recruitment at the leading edge of moving T cells is dependent on and follows focal adhesion formation at the leading edge and local increase in membrane tension upon chemokine receptor activation. Piezo1 recruitment and activation, followed by calcium influx and calpain activation, in turn, are crucial for the integrin LFA1 (CD11a/CD18) recruitment at the leading edge of the chemotactic human T cells. Thus, we find that Piezo1 activation in response to local mechanical cues constitutes a membrane-intrinsic component of the ‘outside-in’ signaling in human T cells, migrating in response to chemokines, that mediates integrin recruitment to the leading edge

Data_Sheet_1_Dysregulated metal ion homeostasis underscores non-canonical function of CD8+ T cell during COVID-19.ZIP

IntroductionSeveral efforts have been made to describe the complexity of T cell heterogeneity during the COVID-19 disease; however, there remain gaps in our understanding in terms of the granularity within.MethodsFor this attempt, we performed a single-cell transcriptomic analysis of 33 individuals (4 healthy, 16 COVID-19 positive patients, and 13 COVID-19 recovered individuals).ResultsWe found CD8+ T cell-biased lymphopenia in COVID-19 patients compared to healthy and recovered individuals. We also found an optimal Th1/Th2 ratio, indicating an effective immune response during COVID-19. Expansion of activated CD4+ T and NK T was detected in the COVID-19-positive individuals. Surprisingly, we found cellular and metal ion homeostasis pathways enriched in the COVID-19-positive individuals compared to the healthy and recovered in the CD8+ T cell populations (CD8+ TCM and CD8+ TEM) as well as activated CD4+ T cells.DiscussionIn summary, the COVID-19-positive individuals exhibit a dynamic T cell mediated response. This response may have a possible association with the dysregulation of non-canonical pathways, including housekeeping functions in addition to the conventional antiviral immune response mediated by the T cell subpopulation. These findings considerably extend our insights into the heterogeneity of T cell response during and post-SARS-CoV-2 infection.</p

Circulating Interleukin-8 Dynamics Parallels Disease Course and Is Linked to Clinical Outcomes in Severe COVID-19

Severe COVID-19 frequently features a systemic deluge of cytokines. Circulating cytokines that can stratify risks are useful for more effective triage and management. Here, we ran a machine-learning algorithm on a dataset of 36 plasma cytokines in a cohort of severe COVID-19 to identify cytokine/s useful for describing the dynamic clinical state in multiple regression analysis. We performed RNA-sequencing of circulating blood cells collected at different time-points. From a Bayesian Information Criterion analysis, a combination of interleukin-8 (IL-8), Eotaxin, and Interferon-γ (IFNγ) was found to be significantly linked to blood oxygenation over seven days. Individually testing the cytokines in receiver operator characteristics analyses identified IL-8 as a strong stratifier for clinical outcomes. Circulating IL-8 dynamics paralleled disease course. We also revealed key transitions in immune transcriptome in patients stratified for circulating IL-8 at three time-points. The study identifies plasma IL-8 as a key pathogenic cytokine linking systemic hyper-inflammation to the clinical outcomes in COVID-19

Adipose recruitment and activation of plasmacytoid dendritic cells fuel metaflammation

In obese individuals the visceral adipose tissue (VAT) becomes seat of chronic low grade inflammation (metaflammation). But the mechanistic link between increased adiposity and metaflammation remains largely unclear. We report here that in obese individuals deregulation of a specific adipokine, chemerin, contributes to innate initiation of metaflammation, by recruiting circulating plasmacytoid dendritic cells (pDCs) into visceral adipose tissue via chemokine-like receptor 1 (CMKLR1). Adipose tissue-derived high mobility group B1 (HMGB1) protein, activates toll-like receptor 9 (TLR9) in the adiposerecruited pDCs by transporting extracellular DNA via receptor for advanced glycation endproducts (RAGE) and induces production of type I interferons. Type I interferons in turn help in proinflammatory polarization of adipose-resident macrophages. Interferon signature gene expression in VAT correlates with both adipose tissue and systemic insulin resistance in obese individuals, represented by ADIPO-IR and HOMA2-IR respectively, and defines two subgroups with different susceptibility to insulin resistance. Thus our study reveals a hitherto unknown pathway that drives adipose tissue inflammation and consequent insulin resistance in obesity