Stable Isotope-Labeled Raman Imaging Reveals Dynamic Proteome Localization to Lipid Droplets in Single Fission Yeast Cells

SummaryLipid droplets have been hypothesized to be intimately associated with intracellular proteins. However, there is little direct evidence for both spatiotemporal and functional relations between lipid droplets and proteins provided by molecular-level studies on intact cells. Here, we present in vivo time-lapse Raman imaging, coupled with stable-isotope (13C) labeling, of single living Schizosaccharomyces pombe cells. Using characteristic Raman bands of proteins and lipids, we dynamically visualized the process by which 13C-glucose in the medium was assimilated into those intracellular components. Our results show that the proteins newly synthesized from incorporated 13C-substrate are localized specifically to lipid droplets as the lipid concentration within the cell increases. We demonstrate that the present method offers a unique platform for proteome visualization without the need for tagging individual proteins with fluorescent probes.

Graphical AbstractFigure optionsDownload high-quality image (189 K)Download as PowerPoint slideHighlights
► Raman spectroscopy requires no dye probe but still enables molecular imaging
► Stable-isotope labeling distinguishes between existing and newly formed proteins
► Protein localization to lipid droplets has been revealed in fission yeast
► The colocalization phenomenon is associated with starvation