Visualizing sphingolipid biosynthesis in cells.

Biosynthetic pathways play a fundamental role in the building and operation of the cell by synthesizing the constituents by which the cell is constructed, and by producing signalling intermediates that play a key role in cell regulation. While a lot is known about the metabolite profile of the cells and about the biochemical pathways through which these metabolites are produced, the cellular localization of the biosynthetic machineries and the importance of this localization to the regulation of the metabolism has often been given less attention. This derives from the fact that, for several of these pathways, the enzymes involved are found colocalized in one compartment where their specific localization is unlikely to influence their function. The sphingolipid (SL) metabolic pathway is a notable exception to this as SL synthetic enzymes are laid out on a specific pattern across the secretory compartments. Such compartmentalized organization of the SL synthesis has functional implications as it makes the fine-tuned regulation of the process possible by allowing cells to regulate specific segments of the pathway in response to stimuli and for adaptation. The organization, dynamics, and regulation of the SLs and their biosynthetic machinery have been investigated using imaging-based methods. Here we provide a brief introduction to the techniques that have been or that could be employed to visualize the SL biosynthetic machinery and SLs themselves and discuss the insights provided by these studies in understanding this metabolism.