Hungry Yeast Cells Are Microscopic Living Thermometers
Membranes are essential to our cells. Every cell in your body is encased by one. And each of those cells contains specialized chambers, or organelles, which are similarly confined by membranes.
Membranes assist cells in accomplishing tasks like breaking down food for energy, building and taking down proteins, monitoring environmental conditions, sending signals, and choosing when to split.
Biologists have long failed to comprehend specifically how membranes fulfill these different sorts of jobs. The main components of membranes– big, fat-like molecules called lipids and compact molecules like cholesterol– make terrific barriers. In all but a handful of scenarios, it is uncertain exactly how those molecules aid proteins within membranes to execute their tasks.
How can membranes do so much?
In a paper published on January 25, 2022, in the Proceedings of the National Academy of Sciences, a group at the University of Washington examined phase separation in budding yeast– the very same single-celled fungus of brewing and baking fame. They reported that living yeast cells could actively manage a process called phase separation within one of their membranes. Throughout phase separation, the membrane stays intact yet split into multiple, distinctive zones or domains that separate lipids and proteins. The brand-new findings reveal for the very first time that, in reaction to environmental conditions, yeast cells precisely manage the temperature level at which their membrane goes through phase separation. The team behind this discovery theorizes that phase separation is likely a “switch” mechanism that these cells utilize to oversee the sorts of work that membranes do and the signals they send out.
” Previous work revealed that these domains can be observed in the membranes of living yeast cells,” stated lead author Chantelle Leveille, a UW doctoral student in chemistry. “We asked: If a cell must have these domains, then if we change the cell’s environment. By maturing them at different temperature levels, would the cell ‘worry’ and devote energy to keeping phase separation in its membranes? The clear answer is yes, it does!”
The previous study has actually revealed that when sugar is plentiful, the yeast cell’s vacuole– an important organelle for storage and signaling– grows big, and its membrane seems uniform under a microscope. However, when food supplies diminish, the vacuole undergoes phase separation, with several round zones appearing in the organelle’s membrane.
Experimentation with yeast cells
In this new study, Leveille and her co-authors– UW chemistry professor Sarah Keller, UW biochemistry professor Alexey Merz and Caitlin Cornell, formerly a UW doctoral student in chemistry– sought to know whether yeast can actively regulate phase separation. Leveille grew yeast at their common laboratory temperature of 86 F with lots of food. After the food decreased, the yeast cell vacuole membranes underwent phase separation, as anticipated. When Leveille briefly raised the temperature in the yeast’s environment by approximately 25 degrees Fahrenheit, the domains vanished. After that, Leveille grew yeast at a cooler temperature– 77 F rather than the typical 86 F. She discovered that the domains vanished around 25 degrees over this new temperature level. When she grew yeast in still chillier conditions, at 68 F, phase separation once again vanished around 25 degrees more than their growth temperature.
These experiments revealed that the yeast cells always preserved phase separation in the vacuole membrane, till the temperature ascended about 25 degrees above their development temperature.
” We believe this is a clear indication that yeast cells are engineering the vacuole membrane in different environmental conditions to preserve this regular state of phase separation,” stated Leveille. She included that phase separation in the vacuole membrane likely offers a crucial function in yeast.
” This result indicates that membrane phase separation for yeast is likely a two-way door,” stated Leveille. “For instance, if the cells ever discovered food once more, they would want to go back to their initial state. Yeast does not want to get too away from the transition.”
Further research on cell membranes
Future studies can determine other membrane components that influence the vacuole membrane’s capability to phase separate, in addition to the repercussions of its phase separation. Biologists have recognized that the cell stops dividing when the domains appear in the yeast vacuole’s membrane. Because the yeast vacuole’s membrane includes two complexes of proteins that are crucial for cell division, these two events may be linked. When the complexes are much apart, cellular division stops.
” Phase separation in the vacuole happens right when the yeast cell needs to stop dividing since its food supply has actually run out,” stated Merz. “One idea is that phase separation is the mechanism that the yeast cell ‘uses’ to divide these two protein complexes and halt cell division.”
In cells from yeast to humans, protein complexes rooted in membranes influence cell behavior. If further research reveals that phase separation in the yeast vacuole manages cellular division, it would likely be the first rigorous instance of cell regulation with this once-overlooked property of membranes.
“Phase separation could be a typical, reversible mechanism to modulate several sorts of cellular properties,” claimed Keller.
Cornell is currently a postdoctoral researcher at the University of California, Berkeley. The study was funded by the National Institutes of Health and the National Science Foundation.
Read the original article on Scitech Daily.
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Reference: “Yeast cells actively tune their membranes to phase separate at temperatures that scale with growth temperatures” by Chantelle L. Leveille, Caitlin E. Cornell, Alexey J. Merz, and Sarah L. Keller, 25 January 2022, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2116007119
