Biology subjects

Gurdap, C. O.

Publications and source records attributed to Gurdap, C. O..

6 recordsLinked to original sources

bioRxiv2026

Chemokine-induced cell swelling fluidises the plasma membrane to regulate CD8+ T cell migration

T cell migration is primarily viewed as a cytoskeletal process. Here, we show that chemokine-stimulated CD8+ T cell migration is modulated by a volume-driven biophysical switch at the plasma membrane (PM). We found that chemokine-induced cell swelling creates an adhesion-dependent gradient of high PM fluidity at the leading edge. External chemical fluidisation of the PM using membrane modulators enhances migration similar to chemokine-induced fluidisation without the need of cell-swelling. Together, our findings identify PM fluidity as a tuneable biophysical gatekeeper that controls T cell migration, potentially providing a novel mechanical tool for optimising adoptive cell therapies in restrictive tissue microenvironments.

biophysics↗

bioRxiv2026

Identifying Novel Targets of the Stringent Response in Plants and Cyanobacteria using chemoproteomics

Survival in dynamic environments requires photosynthetic organisms to rapidly sense and respond to stress. The stringent response, mediated by the signaling molecule guanosine-3,5-bisdiphosphate (ppGpp), is crucial for acclimation to environmental changes such as darkness and nitrogen limitation. While it has been extensively characterized in heterotrophic bacteria such as Escherichia coli, the molecular mechanisms and regulatory targets of ppGpp in photosynthetic organisms remain less understood. Here, we report large-scale chemoproteomic identification of ppGpp-binding proteins across plant chloroplasts and cyanobacteria, revealing both conserved and novel targets compared to E. coli. In plants, we found that ppGpp regulates pyrimidine metabolism by inhibiting the chloroplastic enzyme aspartate transcarbamoylase (PyrB). In cyanobacteria, we found that ppGpp activates glucose-1-phosphate adenylyltransferase (GlgC) involved in glycogen synthesis, activates citrate synthase (GltA), and induces carboxysome aggregation. These findings expand the known ppGpp regulatory network in photosynthetic organisms and provide a foundation for understanding how ppGpp coordinates adaptation to nutrient and environmental stresses.

systems biology↗

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

Prodan-based solvatochromic probes for polarity imaging of organelles

Solvatochromic probes provide microscopic, structural and functional information on their targeted cellular compartments. In this field, the challenge lies in designing probes that are both sufficiently sensitive to environment, and specific in their subcellular localization. Here, we design Prodan-based polarity probes targeting the following organelles: mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes and lipid droplets. The new probes provide robust organelle targeting, except for the mitochondrial probe, whose targeting ability is cell type dependent. Due to operating range of Prodan fluorophore in the UV-Blue region, our probes can be easily combined with other fluorescent tags in the visible range. Therefore, polarity of sub-cellular compartments can be studied together with additional fluorescent reporters. We used these probes to show the polarity of organelle membranes in healthy cells and under starvation condition where we observed organelle-specific polarity remodeling. These probes are important addition to the repertoire of smart cellular probes and will find critical use in understanding spatiotemporal regulation of cellular physiology.

biophysics↗

bioRxiv2022

Purely enzymatic incorporation of an isotope-labeled adenine into RNA for the study of conformational dynamics by NMR

Solution NMR spectroscopy is a well-established tool with unique advantages for structural studies of RNA molecules. However, for large RNA sequences, the NMR resonances often overlap severely. A reliable way to perform resonance assignment and allow further analysis despite spectral crowding is the use of site-specific isotope labeling in sample preparation. While solid-phase oligonucleotide synthesis has several advantages, RNA length and availability of isotope-labeled building blocks are persistent issues. Purely enzymatic methods pose as an alternative and have been presented in the literature. In this study, we report on a method in which we exploit the preference of T7 RNA polymerase for nucleotide monophosphates over triphosphates for the 5 position, which allows 5-labeling of RNA. Successive ligation to an unlabeled RNA strand generates a site-specifically labeled RNA. We show the successful production of such an RNA sample for NMR studies, report on experimental details and expected yields, and present the surprising finding of a previously hidden set of peaks which reveals conformational exchange in the RNA structure. This study highlights the feasibility of site-specific isotope-labeling of RNA with enzymatic methods.

biochemistry↗

bioRxiv2021

The influence of the extracellular domains on the dynamic behavior of membrane proteins

The dynamic behavior of plasma membrane proteins mediates various cellular processes such as cellular motility, communication, and signaling. It is widely accepted that the dynamics of the membrane proteins is determined either by the interactions of the transmembrane domain with the surrounding lipids or by the interactions of the intracellular domain with cytosolic components such as cortical actin. Although initiation of different cellular signaling events at the plasma membrane has been attributed to the extracellular domain (ECD) properties recently, the impact of ECDs on the dynamic behavior of membrane proteins is rather unexplored. Here, we investigate how the ECD properties influence protein dynamics in the lipid bilayer by reconstituting ECDs of different sizes or glycosylation in model membrane systems and analyzing ECD-driven protein sorting in lipid domains as well as protein mobility. Our data shows that increasing the ECD mass or glycosylation leads to a decrease in ordered domain partitioning and diffusivity. Our data reconciles different mechanisms proposed for the initiation of cellular signaling by linking the ECD size of membrane proteins with their localization and diffusion dynamics in the plasma membrane. SIGNIFICANCE STATEMENTWe studied how the size and glycosylation of the proteins influences their dynamic behavior in a lipid bilayer by reconstituting the ECDs of different sizes or glycosylation in model membrane systems and analyzing their sorting into lipid domains as well as their mobility. We observe that increasing the ECD apparent mass leads to a decrease in membrane ordered domain partitioning and diffusivity. Our data reconciles multiple mechanisms proposed for the initiation of cellular signaling by linking the ECD properties of membrane proteins with their localization and diffusion dynamics in the plasma membrane.

biophysics↗