A Dual Fluorescent-Raman Bioorthogonal Probe for Specific Biosynthetic Labeling of Gangliosides

Gangliosides are sialic acid-containing glycosphingolipids integral to the cell membrane and are particularly abundant in the nervous system. Aberrant ganglioside metabolism contributes to pathological conditions including neurodegenerative diseases, lysosomal storage disorders, and cancer. Currently, tools to visualize and detect gangliosides are very limited and non-specific. Here, we describe a dual fluorescent and Raman-active ManNAlk derivative, phenanthrene-9-Pr4ManNAlk (MM-JH-2), capable of one-step selective labeling of gangliosides in cells. This modified ManNAlk derivative produces a biologically unique Raman spectral signature, which arise from the carbon-carbon triple bond augmented by conjugation to a fluorescent phenanthrene moiety. By using this dual probe, unambiguous identification is achieved within cells. Raman maps generated using the alkyne stretching frequency indicate a distribution of MM-JH-2 overlapping with intracellular membrane lipids. Using confocal fluorescence imaging, the cellular transport of labeled gangliosides was tracked from synthesis to recycling in the acidic compartments. Notably, MM-JH-2 can differentiate between cells that differ in ganglioside biosynthetic flux, such as malignant and nonmalignant cells, as well as distinguish between B cells and T cells. Thus, MM-JH-2 is a novel next-generation metabolic chemical reporter (MCR) that is Raman-active, fluorescent, and can be broadly applied to cellular studies investigating ganglioside biosynthetic flux.