Nav: Home

Researchers refute fifty-year old doctrine on cell membrane regulation

February 06, 2020

The boundary between life and non-life is a remarkably narrow one. A central hallmark of life is the cellular membrane - a protective barrier of only a few nanometers thickness (one nanometre is a millionth of a millimetre) that is composed of proteins and two fluid layers of water-insoluble lipids. The function and integrity of this lipid bilayer is essential for the survival of the cell. If the cell membrane (or plasma membrane as it is also known) is compromised, the cell will die.

'But this boundary is more than just a semi-permeable, passive barrier' explains Robert Ernst, Professor of Molecular Biology at Saarland University, whose research focuses on improving our understanding of these ultra-thin, flexible barriers around our cells. 'Cell membranes are astonishing materials with bizarre properties that are difficult to imagine. They are extremely soft, yet they can cope with pressures that are hundreds of times greater than atmospheric pressure. At the same time, they have liquid-like properties and the ability to self-repair. This unique material protects the our cells from physical and chemical stress, facilitates communication between cells, mediates uptake of nutrients, and it wards off invading pathogens,' says Ernst.

For a system that has to perform such a variety of functions, it is critical to have fine-tuned properties to warrant full functionality. 'The cell membrane is a self-regulated system that is able to optimize its composition to each environmental condition.' To illustrate this adaptability, Robert Ernst chooses the image of a reindeer with its hooves in the Arctic permafrost, while its head has a stable temperature of 37 degrees Celsius. 'The cell membranes close to the hoove are composed of an entirely different set of lipids than the membranes in the brain.' says Ernst.

For about the last fifty years, scientists have assumed that the fluid character of the membrane is crucial for this adaptivity. By sensing membrane fluidity, a cell would 'know' what to do to survive in the cold. When the membrane becomes more viscous or even freezes as the temperature falls, the cell reacts by producing a different set of lipids that does not freeze as easily. A perfectly logical and credible explanation, which found its way as the theory of 'homeoviscous adaptation' into the textbooks of biochemistry.

'Unfortunately, this is not what's happening,' says Robert Ernst.

Through a collaborative scientific study involving lead author Stephanie Ballweg, Robert Ernst's research team at the Saarland University and colleagues from Great Britain, Germany and the USA, the researchers have been able to refute the central assumption underlying the hypothesis of 'homeoviscous adaptation'. 'We have isolated the membrane sensor Mga2 from baker's yeast and investigated how it responds to membrane fluidity,' explains Ernst. 'According to the prevailing hypothesis, this sensor would trigger a response whenever the membrane viscosity increases. But that is not what we observe.' It turns out that the fluidity is irrelevant, but that the packing density of lipid atoms in a special region of the membrane determines whether or not the sensor is activated. 'This makes it possible for the sensor to distinguish between saturated and unsaturated fatty acids in the membrane lipids,' says Ernst, describing the findings that have swept away a fifty-year-old theory.

And why didn't someone come up with this idea earlier? 'Up until recently, the disciplines interested in membranes have worked somewhat in isolation with relatively little exchange,' says Ernst. 'In order to conduct this research project, it was crucial to bring together experts in physics, materials science, biochemistry, and genetics.' Only by the synergy released by this interdisciplinary team it was possible to test the validity of the prevailing model. Based on these findings, bioscientists around the world can revisit the important question how membrane regulate the function of membrane proteins and how the lipid composition affects the communication between cells from a new perspective.
-end-
Article:

Stephanie Ballweg, Erdinc Sezgin, Milka Doktorova, Roberto Covino, John Reinhard, Dorith Wunnicke, Inga Hänelt, Ilya Levental, Gerhard Hummer & Robert Ernst: Regulation of lipid saturation without sensing membrane fluidity. Nature Communications, https://doi.org/10.1038/s41467-020-14528-1.

Saarland University

Related Proteins Articles:

Finding a handle to bag the right proteins
A method that lights up tags attached to selected proteins can help to purify the proteins from a mixed protein pool.
Designing vaccines from artificial proteins
EPFL scientists have developed a new computational approach to create artificial proteins, which showed promising results in vivo as functional vaccines.
New method to monitor Alzheimer's proteins
IBS-CINAP research team has reported a new method to identify the aggregation state of amyloid beta (Aβ) proteins in solution.
Composing new proteins with artificial intelligence
Scientists have long studied how to improve proteins or design new ones.
Hero proteins are here to save other proteins
Researchers at the University of Tokyo have discovered a new group of proteins, remarkable for their unusual shape and abilities to protect against protein clumps associated with neurodegenerative diseases in lab experiments.
Designer proteins
David Baker, Professor of Biochemistry at the University of Washington to speak at the AAAS 2020 session, 'Synthetic Biology: Digital Design of Living Systems.' Prof.
Gone fishin' -- for proteins
Casting lines into human cells to snag proteins, a team of Montreal researchers has solved a 20-year-old mystery of cell biology.
Coupled proteins
Researchers from Heidelberg University and Sendai University in Japan used new biotechnological methods to study how human cells react to and further process external signals.
Understanding the power of honey through its proteins
Honey is a culinary staple that can be found in kitchens around the world.
How proteins become embedded in a cell membrane
Many proteins with important biological functions are embedded in a biomembrane in the cells of humans and other living organisms.
More Proteins News and Proteins Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.