Biophysical Society Thematic Meeting | Ascona 2026

Mechanobiology of Infection

Poster Abstracts

24-POS Board 24 MECHANO-CHEMICAL MODULATION OF FORCES IN HOMOTYPIC PHAGOSOMES FUSION Anupam Singh 1 ; Lisa Redlingshöfer 1 ; Stephan W Grill 1,3 ; Marino Zerial 1,2 ; 1 Max Planck Institute of Molecular Cell Biology and Genetics , Dresden, Germany 2 Fondazione Human Technopole, Milan, Italy 3 Technische Universität Dresden, Cluster of Excellence Physics of Life,, Dresden, Germany Introduction: Phagosomes are dynamic membrane-bound organelles playing a central role in mechanobiology of infections. They are active mechanical and biochemical organelles integrating the physical cues with antimicrobial responses. Internalized phagosomes undergo maturation through sequential fusion with endosomes and lysosomes, accompanied by changes in membrane composition, luminal pH, and enzymatic content. Importantly, pathogens have evolved strategies to manipulate phagosomal mechanics, altering membrane tension, preventing lysosomal fusion, or escaping into the cytosol. Despite the identification of necessary and sufficient components for phagosomes membrane tethering and fusion, the orchestration of the process and the mechanics of force generation to overcome the high energy barrier of membrane fusion remain elusive. Thus, cooperativity of molecular complexes consisting of small GTPases, regulators and effectors, must be investigated not only for interactions but also for their ability to generate forces that drive tethering and fusion. Objective: An experimental system is established to study mechanics and dynamics of homotypic phagosomes fusion. We dissect the role of molecular components in driving membrane tethering to fusion. Methods: Optical force spectroscopy is applied to elucidate the mechanics and dynamics of homotypic phagosomes fusion by measuring force, distance and duration of events. Phagosomes are formed by micron sized beads engulfment by mouse macrophages, and later extracted to be trapped on a dual trap optical tweezers. Further, the extent of fusion is calculated by confocal microscopy in the same setup. Results: Removal of Rab5 & its effectors lower the fusion efficiency and also the extent of lipid exchange. Force spectroscopy reveals a higher energy contribution from Rab5 & its effectors in membrane tethering to fusion. A sizable amount of energy is required to cross the protein mesh/brushes in homotypic phagosomes fusion. Conclusions: Rab5 and its effectors contribute significantly to the efficiency of fusion by affecting, both extent of fusion and energy of membrane fusion.

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