Caveolae are bulb-shaped invaginations of the plasma membrane (PM) that undergo scission and fusion at the cell surface and are enriched in specific lipids. However, the influence of lipid composition on caveolae surface stability is not well described or understood. Accordingly, we inserted specific lipids into the cell PM via membrane fusion and studied their acute effects on caveolae dynamics. We demonstrate that sphingomyelin stabilizes caveolae to the cell surface, whereas cholesterol and glycosphingolipids drive caveolae scission from the PM. Although all three lipids accumulated specifically in caveolae, cholesterol and sphingomyelin were actively sequestered, whereas glycosphingolipids diffused freely. The ATPase EHD2 restricts lipid diffusion and counteracts lipid-induced scission. We propose that specific lipid accumulation in caveolae generates an intrinsically unstable domain prone to scission if not restrained by EHD2 at the caveolae neck. This work provides a mechanistic link between caveolae and their ability to sense the PM lipid composition.

Laser-mediated dissection methods have been used for many years to micro-irradiate biological samples, but recent technological progress has rendered this technique more precise, powerful, and easy to use. Today pulsed lasers can be operated with diffraction limited, sub-micrometer precision to ablate intracellular structures. Here, we discuss laser nanosurgery setups and the instrumentation in our laboratory. We describe how to use this technique to ablate cytoskeletal elements in living cells. We also show how this technique can be used in multicellular organisms, to micropuncture and/or ablate cells of interest and finally how to monitor a successful laser nanosurgery.

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19Caveolae, bulb-shaped invaginations of the plasma membrane (PM), show distinct behaviors 20 of scission and fusion at the cell surface. Although it is known that caveolae are enriched in 21 cholesterol and sphingolipids, exactly how lipid composition influences caveolae surface 22 stability has not yet been elucidated. Accordingly, we inserted specific lipids into the PM of 23 cells via membrane fusion and studied acute effects on caveolae dynamics. We demonstrate 24 that cholesterol and glycosphingolipids specifically accumulate in caveolae, which decreases 25 their neck diameter and drives their scission from the cell surface. The lipid-induced scission 26 was counteracted by the ATPase EHD2. We propose that lipid accumulation in caveolae 27 generates an intrinsically unstable domain prone to scission if not balanced by the restraining 28 force of EHD2 at the neck. Our work advances the understanding of how lipids contribute to 29 caveolae dynamics, providing a mechanistic link between caveolae and their ability to sense 30 the PM lipid composition. 31 SUMMARY 32 Caveolae serve as mechanoprotectors and membrane buffers but their specific role in sensing 33 plasma membrane lipid composition remains unclear. Hubert et al. show that cholesterol and 34 glycosphingolipids accumulate in caveolae and drive subsequent scission from the cell 35 surface. These results provide new insight into how lipids contribute to budding and scission 36 of membrane domains in cells.37