Scientists have long puzzled over cholesterol. It's biologically necessary; it's observably harmful - and nobody knows what it's doing where it's most abundant in cells: in the cell membrane. Now, for the first time, chemists at the University of Illinois at Chicago (UIC) have used a path-breaking optical imaging technique to pinpoint cholesterol's location and movement within the membrane. They made the surprising finding that, in addition to its many other biological roles, cholesterol is a signaling molecule that transmits messages across the cell membrane. The finding was reported online on December 26, 2016 in Nature Chemical Biology. The article is titled “Orthogonal Lipid Sensors Identify Transbilayer Asymmetry of Plasma Membrane Cholesterol.” "Cholesterol is a lipid that gets bad press because of its association with cardiovascular disease," says Wonhwa Cho, Ph.D., Professor of Chemistry at UIC, who led the research. "It's been very well studied, but not much is known about its cellular function. What is its role? Is it a bad lipid? Absolutely not - for example, the brain is about half lipid, and cholesterol is the richest lipid in the brain," he said. A cholesterol deficiency can cause several diseases, and the substance is the starting material for making the body's dozen or so steroid hormones. Dr. Cho's earlier studies showed cholesterol interacts with many regulatory molecules - mostly cellular proteins - but it was never thought to be one. "We knew it could play an important role in cell regulation - for example, in proliferation or development," he said. "We know that high-fat diets, which boost cholesterol levels, have been linked to an elevated incidence of cancer. How, is not fully understood," Dr. Cho said.
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