Biology subjects

Sjule, E.

Publications and source records attributed to Sjule, E..

4 recordsLinked to original sources

bioRxiv2026

Cell surface remodeling caused by the loss of TMEM30A in immune cells

Plasma membrane lipid asymmetry is tightly regulated and fundamental to mammalian cell physiology. TMEM30A is the {beta}-subunit of P4-ATPases, flippase enzymes that maintain strict phosphatidylserine (PS) asymmetry by pumping it from the outer to the cytosolic leaflet. Loss of TMEM30A function causes constitutive PS externalization and has been implicated in diseases such as diffuse large B-cell lymphoma and tumour immune evasion. Here, we systematically define the biophysical and molecular consequences of TMEM30A deletion in immune cells. Using a live-cell lipid reporter, membrane order probe, and surface proteome mapping, we show that TMEM30A-knockout cells display robust PS externalization accompanied by faster lateral diffusion of membrane constituents and decreased plasma membrane order. Surface proteome reorganization includes increased abundance of tetraspanins and CD47. Further, TMEM30A loss triggers glycocalyx remodeling via ADAM10-dependent shedding that removes major transmembrane mucins, including CD43 and CD162. Together, these data reveal a coordinated reorganization of lipids, glycans, and proteins upon TMEM30A loss, suggesting mechanistic links between flippase dysfunction and increased plasma membrane dynamics and potential sensitization to immune therapy. Furthermore, our study provides an integrated surfaceome framework that might shed light on the relationship between TMEM30A expression and clinical outcomes in cancer.

immunology↗

bioRxiv2025

Studying macromolecular composition in cell-cell interfaces using 3D membrane reconstitution systems

During direct communication between two cells, the plasma membranes of each cell serve as a platform for ligand-receptor interaction initiating downstream signalling cascades. In immune cell signalling, this cell-cell interface - the immune synapse - is highly spatiotemporally organized. Multiple stimulatory and co-stimulatory signals need to be integrated over time to ensure proper immune cell function. This process is still not fully understood given the vast complexity of interactions between proteins, lipids, glycocalyx and associated cortical actin cytoskeleton. To examine the impact of a single component, the use of model membrane systems has increased. Here, we developed a fully artificial system to study the interface between two vesicles and a semi-artificial one between a live cell and a vesicle to reconstitute 3D contacts. We investigated the distribution and reorganization of immune cell proteins at artificial and semi-artificial contacts. Using our vesicle-vesicle system, we show the enrichment and depletion of different proteins in the synapse. Using the cell-vesicle system we showed how different peptides with varying affinity presented by the same MHC class I affect T cell activation. We further explored the distribution of glycocalyx elements at the cell-cell contact and showed differential partitioning of different sugar moieties in the interface. While we focused on the T cell interface here, our model systems are powerful tools to study distribution and reorganization of lipids, proteins and glycocalyx components at any cell-cell contact.

biophysics↗

bioRxiv2023

Quantifying fluorescence lifetime responsiveness of environment sensitive probes for membrane fluidity measurements

The structural diversity of different lipid species within the membrane defines its biophysical properties such as membrane fluidity, phase transition, curvature, charge distribution and tension. Environment-sensitive probes, which change their spectral properties in response to their surrounding milieu, have greatly contributed to our understanding of such biophysical properties. To realize the full potential of these probes and to avoid misinterpretation of their spectral responses, a detailed investigation of their fluorescence characteristics in different environments is necessary. Here, we examined fluorescence lifetime of two newly developed membrane order probes, NR12S and NR12A, in response to alterations in their environments such as degree of lipid saturation, cholesterol content, double bond position and configuration and phospholipid headgroup. As comparison, we investigated lifetime sensitivity of the membrane tension probe Flipper in these environments. Applying fluorescence lifetime imaging microscopy (FLIM) in both model membranes and biological membranes, all probes distinguished membrane phases by lifetime, but exhibited different lifetime sensitivities to varying membrane biophysical properties (e.g. cholesterol). While the lifetime of Flipper is particularly sensitive to membrane cholesterol content, NR12S and NR12A lifetime is moderately sensitive to both cholesterol content and lipid acyl chains. Moreover, all probes exhibit longer lifetimes at longer emission wavelengths in membranes of any complexity. This emission-wavelength dependency results in varying lifetime resolution at different spectral regions, highly relevant for FLIM data acquisition. Our data provides valuable insights on how to perform FLIM with these probes and highlights both their potential and limitations.

biophysics↗

bioRxiv2023

Apoptosis-mediated ADAM10 activation removes a mucin barrier promoting T cell efferocytosis

Efferocytic clearance of apoptotic cells in general, and T cells in particular, is required for tissue and immune homeostasis. Transmembrane mucins are extended glycoproteins highly expressed in the cell glycocalyx that act as a barrier to phagocytosis. Whether and how mucins may be regulated during cell death to facilitate efferocytic corpse clearance is not understood. Here we show that normal and transformed human T cells express a subset of mucins which are rapidly and selectively removed from the cell surface during apoptosis. This process is mediated by the ADAM10 sheddase, the activity of which is associated with XKR8-catalyzed flipping of phosphatidylserine to the outer leaflet of the plasma membrane. Mucin clearance enhances uptake of apoptotic T cells by macrophages, confirming mucins as an enzymatically-modulatable barrier to efferocytosis. Together these findings reveal a novel glycocalyx regulatory pathway with implications for therapeutic intervention in the clearance of normal and transformed apoptotic T cells.

cell biology↗