Cell membranes play a crucial role in maintaining the integrity and functionality of cells. Scientists from the University of Geneva (UNIGE), in collaboration with the Institut de biologie structurale de Grenoble (IBS) and the University of Fribourg (UNIFR), have used cryo-electron microscopy to observe how lipids and proteins at the plasma membrane interact and react to mechanical stress. This work shows that, depending on conditions, small membrane regions can stabilize various lipids to trigger specific cellular responses.

 

The scientists used baker's yeast (Saccharomyces cerevisiae), a model organism used in many research laboratories because it is very easy to grow and genetically manipulate. What's more, most of its fundamental cellular processes mirror those of higher organisms. This study focused on a specific membrane microdomain scaffolded by a protein coat known as eisosomes. These structures are believed to be capable of sequestering or releasing proteins and lipids to help the cells resist and/or signal damage to the membrane, using processes that were previously unknown. Using cryo-electron microscopy, the scientists observed that the lipid organisation of these microdomains is altered in response to mechanical stimuli. ''We discovered that when the eisosome protein lattice is stretched, the complex arrangement of lipids in the microdomains is altered. This reorganisation of the lipids likely enables the release of sequestered signalling molecules to trigger stress adaptation mechanisms.

 

This work opens many new avenues for studying the primordial role of membrane compartmentalisation -- i.e. the movement of proteins and lipids within membranes to form sub-compartments known as microdomains. This mechanism enables cells to perform specialised biochemical functions, in particular the activation of cellular communication pathways in response to the various stresses to which they may be exposed.