Seminars

2013-02-12

Imaging the lipid distribution in the plasma membrane and probing the mechanisms that control it with high-resolution SIMS

Prof. Mary L Kraft, University of Illinois - Dept. of Chemical & Biomolecular Engineering
Speaker's Website
Prof. Sarah Keller, Dept. of Chemistry

The plasma membrane is the protein-containing lipid bilayer that forms a selectively permeable barrier at the surface of every cell. In eukaryotic cells, the plasma membrane is divided into functionally specialized microdomains that contain different protein and lipid species. Though the cellular abundances of two lipid species, sphingolipids and cholesterol, influence many eukaryotic cell functions, the distributions of sphingolipids, cholesterol, and most other lipid species within the plasma membrane have not been definitively established. Methods to directly visualize lipid domains without the use of labels that might induce lipid clustering could help to resolve this issue. For this purpose, we have developed a high-resolution secondary ion mass spectrometry (SIMS) approach to map the distributions of isotope-labeled lipids in the plasma membranes of intact cells with better than 100 nm lateral resolution. With this approach, we have mapped the distributions of metabolically incorporated 15N-sphingolipids and 18O-cholesterol in the plasma membranes of fibroblast cells, and assessed co-localization between these components. By using this approach to visualize the 15N-sphingolipid and 18O-cholesterol distributions after treating cells with various drugs, we show that complex cellular mechanisms control the lipid organization in the plasma membranes of eukaryotic cells.