Spatial Organization of Biological Fuctions | BPS Thematic Meeting

Spatial Organization of Biological Functions Meeting

Poster Abstracts

16-POS Board 16 DECODING BIOMOLECULAR CONDENSATE–MEMBRANE INTERACTIONS: THE ROLE OF IONIC STRENGTH AND CHARGE SCREENING Geetanjali Sahu 1 ; Karthika S Nair 1,2 ; Dr. Harsha Bajaj 1,2 ; 1 CSIR NIIST, BBD, Trivandrum, India 2 AcSIR , Ghaziabad, India Biomolecular condensates formed via liquid–liquid phase separation are increasingly recognized for their roles in organizing intracellular biochemistry. Their dysregulation is linked to diseases such as neurodegeneration, cancer, and viral infections, where aberrant phase behavior can disrupt cellular homeostasis. While much is known about condensate formation in the cytoplasm and nucleus, their interactions with cellular membranes remain less explored. In this study, we use biomimetic systems to dissect how condensates interact with membranes under controlled, cell-like conditions. Using Giant Unilamellar Vesicles (GUVs) with defined lipid compositions, we assemble ATP and poly-L-lysine condensates inside vesicles and control the selective exchange of small molecules. This setup allows us to probe condensate–membrane interactions with precise spatiotemporal resolution. We focus on the role of ionic strength, a key physiological parameter in modulating electrostatic interactions between condensates and membranes. By varying salt concentrations, we observe distinct membrane responses: at low salt concentrations, strong electrostatic interactions lead to wrinkled membrane morphologies and reduced lipid mobility (as measured by FRAP and imaging), while at high salt concentrations, charge screening weakens these interactions, resulting in membrane budding or minimal deformation. Interestingly, we observe that condensate size is modulated through interactions with the lipid membrane, which are themselves governed by the ionic environment— highlighting a coupled regulation of condensate growth and membrane association by electrostatic forces. These findings demonstrate that ionic strength finely tunes the electrostatic landscape at condensate membrane interfaces, dictating the nature and extent of membrane remodeling. Our work provides a mechanistic framework to understand how biophysical parameters, such as ionic conditions, govern condensate membrane dynamics and condensate size, offering insight into how physical forces contribute to the spatial organization of biochemical processes within cells.

45