Living cell membranes can self-sort their components by 'demixing'
Cellsāthe building blocks of our bodiesāare encapsulated by membranes. The same goes for the specialized compartments within our cells.
These membranes are extremely thin, oily films, containing proteins and fatty molecules called lipids. For decades, scientists have argued about how cell membranes organize and maintain distinct regions enriched in particular protein and lipid types. These regions are thought to influence cellular activities, such as the signaling that controls both normal cellular growth and the growth of cancerous cells.
In a paper published Dec. 5 in the Biophysical Journal, scientists at the University of Washington show for the first time that the complex distribution of molecules within a membrane of a living yeast cell arises through demixing. Also known as phase separation, demixing is a simple physical process that is similar to the action that causes droplets of oil to separate from vinegar in a salad dressing.
"Cells have a toolbox with a variety of resources to help them complete a variety of tasks," said senior author Sarah Keller, a UW professor of chemistry. "By teaming up with Alex Merz, a UW professor of biochemistry and a yeast expert, we've shown that phase separation is one of those tools to shape membranes and their functions within a living system."
More information: Scott P. Rayermann et al, Hallmarks of Reversible Separation of Living, Unperturbed Cell Membranes into Two Liquid Phases, Biophysical Journal (2017). DOI: 10.1016/j.bpj.2017.09.029
Phase separation in a synthetic membrane. Credit: Caitlin Cornell/University of Washington
A vacuole from a genetically engineered strain of yeast in which membrane proteins fluorescently glow. Keller and her team have shown that the dark-spotted regions within the membrane form through phase separation, also known as demixing. Credit: Alex Merz/University of Washington A time-lapse image of a single yeast vacuole. The white arrow indicates a region in which two membrane domains begin to coalesce. Credit: Alex Merz/University of Washington
