How cell membranes organize and maintain distinct regions enriched in a particular protein type has been a source of argument among scientists for decades. According to a paper published yesterday in the Biophysical Journal, complex distribution of molecules within the membrane of yeast cells arises through demixing, also known as phase separation.
The researchers came up with the concept after looking at images of a genetically engineered strain of yeast with fluorescently glowing membrane proteins. The lit up vacuoles in the proteins looked like miniature green balls with domains that look like dark polka dots. The domains resembled membrane regions that arise from phase separation previously observed in two non-living systems—simple artificial membranes created in the lab and membranes shed from cells under severe stress.
Through in vivo and cell free imaging, the team was able to observe other hallmarks of phase separation within the cell. These observations include the fact that the domains merge quickly, like the mixing of fats in separated oil and that phase separation depends on temperature, temperature increase above 90 caused the domains to disappear.
This research opens the door for further questions, such as how cells regulate this phase separation, and follow up studies to confirm this is applicable to other cell types.
"There is incredible potential here to unlock how different types of cells form and maintain unique structures—and how different structures are formed even within the same cell," said senior author Sarah Keller, a University of Washington professor of chemistry.
Image: 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. Image source: Alex Merz/University of Washington.