Biology subjects

Roy, N. H.

Publications and source records attributed to Roy, N. H..

7 recordsLinked to original sources

bioRxiv2024

The scaffold protein CasL regulates T cell migration by restricting membrane blebbing

T cell migration into inflamed tissue is a key control point in the inflammatory response and relies on integrin interactions with their endothelial ligands. Here, we identify the signaling scaffold CasL (Hef1, NEDD9) as a central regulator of integrin-dependent migration in primary T cells. We found CasL is specifically needed for efficient migration on ICAM-1, but not VCAM-1 coated surfaces. While WT T cells migrating on ICAM-1 form an actin-rich cell front and move smoothly, T cells lacking CasL instead form numerous, aberrant membrane blebs. The abnormal blebbing observed in CasL KO T cells likely stems from diminished F-actin in the cell front coupled with increased contractile forces behind the nucleus, suggesting CasL regulates the cytoskeletal architecture in migrating T cells. Importantly, using an in vivo allogeneic hematopoietic transplant model we found that CasL promotes T cell migration into inflamed peripheral tissue, but was dispensable for trafficking to secondary lymphoid organs. Together, these results indicate CasL functions to control the balance of cytoskeletal components during integrin-dependent migration and highlight the importance of integrin signaling for proper migration into inflamed tissue.

cell biology↗

bioRxiv2024

Dengue virus structural proteins are expressed on the surface of DENV-infected cells and are a target for antibody-dependent cellular phagocytosis

Dengue virus (DENV) is an arboviral pathogen found in over 100 countries and a source of significant morbidity and mortality. While the mechanisms underpinning the pathophysiology of severe dengue are incompletely understood, it has been previously suggested that antibodies directed against the DENV envelope (E) protein can facilitate antibody dependent enhancement (ADE) of the infection, increasing the number of infected cells and the severity of infection in an exposed individual. Accordingly, there is interest in defining mechanisms for directly targeting DENV-infected cells for immunologic clearance, an approach that bypasses the risk of ADE. We have previously demonstrated that antibodies specific for DENV non-structural protein 1 (NS1) can opsonize and facilitate the phagocytic clearance of DENV infected cells. However, it is currently unclear if other DENV antigens are expressed on the surface of infected cells, and if these antigens can be targeted by antibody-dependent clearance mechanisms. In this study, we demonstrate that DENV structural proteins are expressed on the surface of DENV-infected cells, and that these antigens can be opsonized by both DENV-immune sera and monoclonal antibodies. In addition, DENV E-specific antibodies can facilitate phagocytic uptake of DENV-infected cells, resulting in the target-cell membrane localizing to endosomes of the engulfing phagocyte. Notably, no DENV genetic material was observed localizing to the engulfing phagocyte, suggesting that horizontal transfer of DENV from the infecting cell is an unlikely occurrence. In their totality, these data reinforce the concept that DENV E-reactive antibodies have a multifaceted role in DENV immunity and pathogenesis beyond neutralization and/or infection-enhancement.

immunology↗

bioRxiv2021

Mechanically active integrins direct cytotoxic secretion at the immune synapse

The secretory output of cell-cell interfaces must be tightly controlled in space and time to ensure functional efficacy. This is particularly true for the cytotoxic immune synapse (IS), the stereotyped junction formed between a cytotoxic lymphocyte and the infected or transformed target cell it aims to destroy1. Cytotoxic lymphocytes kill their targets by channeling a mixture of granzyme proteases and the pore forming protein perforin directly into the IS2, 3. The synaptic secretion of these toxic molecules constrains their deleterious effects to the target cell alone, thereby protecting innocent bystander cells in the surrounding tissue from collateral damage. Despite the importance of this process for immune specificity, the molecular and cellular mechanisms that establish secretory sites within the IS remain poorly understood. Here, we identified an essential role for integrin mechanotransduction in cytotoxic secretion using a combination of single cell biophysical measurements, ligand micropatterning, and functional assays. Upon ligand-binding, the L{beta}2 integrin LFA-1 functioned as a spatial cue, attracting lytic granules containing perforin and granzyme and inducing their fusion at closely adjacent sites within the synaptic membrane. LFA-1 molecules were subjected to pulling forces within these secretory domains, and genetic or pharmacological suppression of these forces abrogated cytotoxicity. We conclude that lymphocytes employ an integrin-dependent mechanical checkpoint to enhance both the potency and the security of their cytotoxic output.

immunology↗

bioRxiv2021

Bringing TrackMate in the era of machine-learning and deep-learning.

TrackMate is an automated tracking software used to analyze bioimages and distributed as a Fiji plugin. Here we introduce a new version of TrackMate rewritten to improve performance and usability, and integrating several popular machine and deep learning algorithms to improve versatility. We illustrate how these new components can be used to efficiently track objects from brightfield and fluorescence microscopy images across a wide range of bio-imaging experiments.

bioinformatics↗

bioRxiv2020

Automated cell tracking using StarDist and TrackMate

The ability of cells to migrate is a fundamental physiological process involved in embryonic development, tissue homeostasis, immune surveillance, and wound healing. Therefore, the mechanisms governing cellular locomotion have been under intense scrutiny over the last 50 years. One of the main tools of this scrutiny is live-cell quantitative imaging, where researchers image cells over time to study their migration and quantitatively analyze their dynamics by tracking them using the recorded images. Despite the availability of computational tools, manual tracking remains widely used among researchers due to the difficulty setting up robust automated cell tracking and large-scale analysis. Here we provide a detailed analysis pipeline illustrating how the deep learning network StarDist can be combined with the popular tracking software TrackMate to perform 2D automated cell tracking and provide fully quantitative readouts. Our proposed protocol is compatible with both fluorescent and widefield images. It only requires freely available and open-source software (ZeroCostDL4Mic and Fiji), and does not require any coding knowledge from the users, making it a versatile and powerful tool for the field. We demonstrate this pipelines usability by automatically tracking cancer cells and T cells using fluorescent and brightfield images. Importantly, we provide, as supplementary information, a detailed step-by-step protocol to allow researchers to implement it with their images.

cell biology↗

bioRxiv2020

LFA-1 signals to promote actin polymerization and upstream migration in T cells

T cell entry into inflamed tissue requires firm adhesion, cell spreading, and migration along and through the endothelial wall. These events require the T cell integrins LFA-1 and VLA-4 and their endothelial ligands ICAM-1 and VCAM-1, respectively. T cells migrate against the direction of shear flow on ICAM-1 and with the direction of shear flow on VCAM-1, suggesting that these two ligands trigger distinct cellular responses. However, the contribution of specific signaling events downstream of LFA-1 and VLA-4 has not been explored. Using primary mouse T cells, we found that engagement of LFA-1, but not VLA-4, induces cell shape changes associated with rapid 2D migration. Moreover, LFA-1 ligation results in activation of the PI3K and ERK pathways, and phosphorylation of multiple kinases and adaptor proteins, while VLA-4 ligation triggers only a subset of these signaling events. Importantly, T cells lacking Crk adaptor proteins, key LFA-1 signaling intermediates, or the ubiquitin ligase cCbl, failed to migrate against the direction of shear flow on ICAM-1. These studies identify novel signaling differences downstream of LFA-1 and VLA-4 that drive T cell migratory behavior. Summary StatementInflammatory responses require leukocyte migration along the vascular wall. We show that signaling from {beta}2, but not {beta}1, integrins induces cytoskeletal changes needed for upstream migration under shear flow.

cell biology↗

bioRxiv2019

CrkL is required for donor T cell migration to GvHD Target organs

The success of cancer therapies based on allogeneic hematopoietic stem cell transplant relies on the ability to separate graft-versus-host disease (GvHD) from graft-versus-tumor (GVT) responses. Controlling donor T cell migration into peripheral tissues is a viable option to limit unwanted tissue damage, but a lack of specific targets limits progress on this front. Here, we show that the adaptor protein CrkL, but not the closely related family members CrkI or CrkII, is a crucial regulator of T cell migration. In vitro, CrkL-deficient T cells fail to polymerize actin in response to the integrin ligand ICAM-1, resulting in defective migration. Using a mouse model of GvHD/GVT, we found that while CrkL-deficient T cells can efficiently eliminate hematopoietic tumors they are unable to migrate into inflamed organs, such as the liver and small intestine, and thus do not cause GvHD. These results suggest a specific role for CrkL in trafficking to peripheral organs but not the lymphatic system. In line with this, we found that although CrkL-deficient T cells could clear hematopoietic tumors, they failed to clear the same tumor growing subcutaneously, highlighting the role of CrkL in controlling T cell migration into peripheral tissues. Our results define a unique role for CrkL in controlling T cell migration, and suggest that CrkL function could be therapeutically targeted to enhance the efficacy of immunotherapies involving allogeneic donor cells.

immunology↗