The unexpected sphingolipid and cholesterol distribution in the plasma membrane (107.1)

Though the cellular abundances of sphingolipids and cholesterol are known to influence many biological processes, the organizations of these components within the plasma membrane are not well established. To address this issue, we have used a chemically specific and spatially well‐resolved imaging technique, high‐resolution secondary ion mass spectrometry (SIMS), to image the distributions of metabolically incorporated 15 N‐sphingolipids and 18 O‐cholesterol in the plasma membranes of intact mouse fibroblasts. Our data reveal sphingolipid domains in the plasma membrane. Contrary to current models, the cholesterol is not enriched in the sphingolipid domains, and is instead fairly evenly distributed within the plasma membrane. We have also used this approach to characterize the effects of cholesterol depletion and disruption of the cytoskeleton on the sphingolipid and cholesterol distributions in the plasma membranes of mouse fibroblasts. Our findings are inconsistent with the prevailing hypothesis that cohesive sphingolipid‐cholesterol interactions are responsible for plasma membrane organization. Instead, our research shows the cytoskeleton plays a major role in organizing the sphingolipids at the cell surface.