Biology subjects

Demeersseman, L.

Publications and source records attributed to Demeersseman, L..

3 recordsLinked to original sources

bioRxiv2025

Stenocytosis: a mechanism for supramolecular attack particle transfer at the CTL lytic synapse

Supramolecular attack particles (SMAPs) are recently discovered key components of the cytotoxic T lymphocytes (CTLs) lytic arsenal exhibiting autonomous cytotoxic behavior. Yet, how these particles might serve as synaptic weapons transferred from CTL into target cells within dynamic lytic synapses remains to be elucidated. In CTL interacting with immobilized stimuli, total internal reflection fluorescence microscopy (TIRFM) and rapid live 3D cell imaging showed that granules containing SMAPs navigate through narrow cortical actin cytoskeleton depletion areas to reach plasma membrane secretion hot-spots where SMAPs are released. In CTLs interacting with cognate target cells, correlative light-electron microscopy (CLEM) and structured illumination 3D imaging showed SMAP release into the synaptic cleft and penetration into the target cell trough an equally narrow gap in the target cell cortical actin cytoskeleton mirroring that formed in the CTL cytoskeleton, and just large enough to admit the SMAP into an early endosome. Our results reveal a previously undescribed process, stenocytosis (from the ancient Greek {sigma}{tau}{varepsilon}{nu}o{varsigma}, "narrow"), which allows hundred-nanometer-scale lytic particles to exit CTLs and enter target cells while evading synaptic defenses.

immunology↗

bioRxiv2024

Highly adaptable deep-learning platform for automated detection and analysis of vesicle exocytosis

Vesicle exocytosis is a fundamental component of intercellular communication, in all organisms. It has been studied for decades, using various imaging tools. Nevertheless, exocytosis research is still limited by the lack of reliable automated analysis procedures. To address this, we developed the Intelligent Vesicle Exocytosis Analysis Platform (IVEA), a nearly universal solution for analyzing exocytosis acquired with live cell imaging. IVEA is applicable to a wide variety of experimental model systems, microscopes and reporter fluorophores. IVEA combines state-of-the-art deep-learning and computer vision regimes to enable fully automated analysis of large data. IVEA runs as a FIJI plugin and does not require prior training or human intervention. IVEA is 60 times faster than manual analysis and is able to detect rare events often missed by the human eye. Overall, IVEA represents a breakthrough in the analysis of cellular secretory mechanisms and has a transformative potential for the exocytosis imaging field.

bioengineering↗

bioRxiv2024

Pore formation at the lytic synapse triggers the canonical pyroptotic cell death pathway

Prokaryotic pore-forming toxins drive inflammasome activation and pyroptosis through K+-dependent activation of the canonical NLRP3/caspase-1/gasdermin D signaling axis. In this study, we hypothesized that perforin, a eukaryotic pore-forming protein released into the lytic synapse by antigen-specific cytotoxic T lymphocytes (CTLs) upon cognate antigen recognition, mimics the pro-pyroptotic activity of ancestral pore-forming toxins, complementing its role as a conduit for granzymes. Utilizing imaging and molecular approaches, we demonstrate that perforation of target cells upon CTL attack elicits swift K+ efflux followed by NLRP3-dependent activation of proinflammatory caspase-1 and its major substrate, the pyroptotic executioner gasdermin D (GSDMD). Acute target cell death upon CTL attack is gasdermin-dependent and demonstrates morphological and molecular features of pyroptosis, including pyroptotic body formation, cell bloating, plasma membrane rupture, and release of intracellular contents. Perforation of target cells by soluble perforin is sufficient to trigger rapid K+ efflux, caspase-1 activation, and pyroptosis. By contrast, sustained interaction with CTLs unmasks a delayed apoptotic phenotype in the remaining target cells. Interestingly, exposure of target cells to exogenous supramolecular attack particles (SMAPs) recapitulates this apoptotic phenotype, suggesting that soluble perforin and SMAPs play dichotomous roles in target cell death. Our results reveal a novel mechanism for engagement of pyroptotic machinery upon CTL attack, in which perforin itself can autonomously engage programmed cell death (PCD), highlighting the complexity and diversity of the CTL lytic arsenal.

immunology↗