Structure-function relationship of complex sphingolipids in yeast

Complex sphingolipids are major components of eukaryotic membranes and play critical roles in many physiologically important events. In mammals, complex glycosphingolipids can carry hundreds of sugar chains as polar head groups, and this structural diversity and complexity is thought to be closely related to their multiple biological functions. In the budding yeast Saccharomyces cerevisiae, the complex sphingolipids have five types of ceramide differing in hydroxylation status, and three types of polar head group containing inositol phosphate and mannose, and thus S. cerevisiae complex sphingolipids can be classified into 15 subtypes in total. Due to the limited molecular classes, the structural diversity of sphingolipids in S. cerevisiae is relatively simple as compared with that in mammalian cells. In S. cerevisiae, depletion of all complex sphingolipids causes a strong growth defect. In contrast, addition of hydroxyl groups to the ceramide moiety in complex sphingolipids and extension of the polar head group are non-essential for growth. However, recent studies indicated that these structural modifications of complex sphingolipids are important for many cellular functions. This review focuses on the physiological importance of each detailed structure and the structural diversity of complex sphingolipids in S. cerevisiae and the other yeasts.