Internship: Squeezing cell-derived vesicles: Correlating presence/absence of cytoskeleton with GPMV mechanical properties

As an intern/Master student in the Physics of Cellular Interactions group headed by Dr. Kristina Ganzinger, you will investigate how the mechanical stability of cell-derived vesicles is affected by the presence or absence of an actin cytoskeleton. These vesicles represent a valuable experimental platform as they approximate the composition of cell membranes and can be used in cases when bottom-up reconstitution of model membranes is not feasible. Building on previous experience in the PCI group, you will explore different chemical vesiculation protocols to produce Giant Plasma Membrane Vesicles (GPMVs) and use confocal fluorescence microscopy to comprehensively test for the presence of an actin cytoskeleton in GPMVs formed by various vesiculation agents. You will then use microfluidic traps to cross-compare the deformability of GPMVs, with fully synthetic vesicles serving as a reference. Finally, this will also allow you to explore different approaches to decrease the mechanical resilience of GPMVs, which can inform strategies to create GPMV-derived supported lipid bilayers.

More about the project
Cell membranes are distinguished by their dual functionality: they are the barrier separating the interior of cells from their environment, yet they simultaneously serve as the main interface through which cells exchange matter and signals with their surroundings. GPMVs have been established as model systems to investigate properties of cellular membranes. Whereas GPMV lipid and protein content and orientation in the membrane have been investigated to some degree, the mechanical properties of these vesicles remain mostly unexplored. GPMVs could potentially be used to form a continuous native-like supported lipid bilayer (nSLB) to serve as an experimental platform for single-molecule, high-resolution studies of cell-cell interaction. However, unlike synthetic liposomes, which burst spontaneously upon contact with glass surfaces to form bilayer patches, GPMVs require additional perturbation strategies (e.g. acoustic pressure or creating an air-water interface to increase the membrane tension ), with variable success rates. This is especially interesting since GPMVs derived through certain chemical vesiculation methods are reported to be missing an underlying actin cortex that would stabilize the membrane structures. Importantly, this has not been conclusively demonstrated for all chemical vesiculation agents, and thus specific vesiculation protocols might result in vesicles that are more amenable to nSLB generation.

1. Ganzinger, K.A. et al. Angew. Chem. Int. Ed. 2020
2. Sezgin, E. et al. Membranes2020
3. Chiang, P.-C. et al. Sci Rep2017