PNAS: Studies reveal the effects of cholesterol on cell membranes

more than a decade, scientists have accepted that cholesterol, a key component of cell membranes, does not uniformly affect different types of membranes. But a new study led by Rana Ashkar, an assistant professor of physics at Virginia Tech, found that cholesterol actually fits biophysical principles.The findings, recently published in the journal PNAS, have far-reaching implications for the design of drug delivery methods and many other biological applications that require specific assumptions about the role of cholesterol in cells."It's well known that cholesterol promotes closer molecular build-up in cell membranes," Ashkar said. In this work, we have shown that, according to the laws of physics, cholesterol does cause membrane hardening at the nanoscale level. These findings affect our understanding of the biological function of cholesterol and its role in health and disease. Thecell membrane is a thin layer of fat molecules that define cell boundaries and regulate a variety of biological functions, including virus transmission and cell division. In order to achieve this function, the membrane structure should be able to bend and allow the shape to change. This tendency to bend depends on the degree to which molecular structural units accumulate. Ashkar adds that tighter packaging results in harder membranes that cannot be easily bent.Bacon, eggs, cheese and many other comfort foods contain a lot of cholesterol. Although too much cholesterol can damage the body, the amount of cholesterol regulated in the cell membrane is absolutely necessary for the normal functioning of the cell. Abnormal cholesterol levels are usually associated with various disease conditions.In addition to cholesterol, our cell membranes are mainly made up of lipids, a small fat molecule that automatically assembles into a double structure when present in water - nearly 60% of the body is made up of water. Lipids and cholesterol together form a barrier that limits our cells and regulates their nutrient exchange.At the molecular level, cholesterol has a smooth and rigid structure. When it interacts with our cell membrane, it gets stuck between the lipids itself, resulting in a higher density of the membrane. Depending on the structure-attribute relationship, this naturally causes the membrane to harden.For more than a decade, physicists and biologists have argued that cholesterol has little effect on the hardness of membranes formed by smooth unsaturated lipids. "This goes against our understanding of the role of cholesterol in cell membranes," Ashkar said. "This also contradicts the standard structure-characteristic relationship in self-assembled materials."Ideally, the cell membrane should maintain a semi-rigid structure: hard enough to maintain its form, but flexible enough to allow dynamic movement of signal proteins and functional domains. Misconceptions about how cholesterol enhances cell membranes affect our understanding of membrane function.The initial data didn't make much sense, but as she delved into it, Ashkar found a clear case of how soft materials "obviously" exhibit different properties based on the parameters of the observation method. She found that important signal events occurred over a shorter period of time, and that added cholesterol caused membrane hardening. (Bio Valley Bioon.com)