Invited Paper AS+BI-MoA8
High-resolution SIMS Imaging of Subcellular Structures

Monday, October 30, 2017, 4:00 pm, Room 13

In mammalian cells, lipids and cholesterol form the selectively permeable plasma membrane that separates the cell from its surroundings, and the intracellular membranes that delineate the boundaries of organelles and transport vesicles. The distributions of cholesterol and each lipid species between these organelles is correlated with health and disease. The accumulation of cholesterol and certain lipid species within lysosomes and endosomes causes defects in intracellular trafficking that can be fatal if left untreated. The ability to image the relative abundances of cholesterol and distinct lipid species within intracellular compartments could lead to a better understanding of the biological mechanisms that regulate subcellular lipid distribution. For this purpose, we have combined metabolic stable isotope incorporation with secondary ion mass spectrometry (SIMS), which is performed on a Cameca NanoSIMS 50, to image the intracellular distributions of cholesterol and sphingolipids. By using depth profiling SIMS to image the distributions of ¹⁸O-cholesterol and ¹⁵N-sphingolipids within a portion of a Madin-Darby Canine Kidney (MDCK) cell, we determined that these two components are enriched within separate intracellular compartments. The sizes and relative positions of the ¹⁵N- and ¹⁸O- enriched intracellular features that are visible in the 3-D representations of the SIMS images suggest that the ¹⁵N-sphingolipids are located within transport vesicles, whereas the ¹⁸O-cholesterol seem to be concentrated within lipid droplets.