Dolichol; Synthesis of fluorescent glycolipids; Endoplasmic reticulum; N-glycosylation; Lipid flippases; Synthesis of click-chemistry lipids; GPI anchoring; Glycolipids
Verchère Alice, Cowton Andrew, Jenni Aurelio, Rauch Monika, Häner Robert, Graumann Johannes, Bütikofer Peter, Menon Anant K. (2021), Complexity of the eukaryotic dolichol-linked oligosaccharide scramblase suggested by activity correlation profiling mass spectrometry, in Scientific Reports
, 11(1), 1411-1411.
Jenni Aurelio, Knüsel Sebastian, Nagar Rupa, Benninger Mattias, Häner Robert, Ferguson Michael A.J., Roditi Isabel, Menon Anant K., Bütikofer Peter (2021), Elimination of GPI2 suppresses glycosylphosphatidylinositol GlcNAc transferase activity and alters GPI glycan modification in Trypanosoma brucei, in Journal of Biological Chemistry
, 297(2), 100977-100977.
Picca Giovanni, Probst Markus, Langenegger Simon M, Khorev Oleg, Bütikofer Peter, Menon Anant K, Häner Robert (2020), Nonenzymatic synthesis of anomerically pure, mannosyl-based molecular probes for scramblase identification studies, in Beilstein Journal of Organic Chemistry
, 16, 1732-1739.
Most proteins that enter the secretory pathway become glycoproteins, i.e. they are modified by sugars such as N-glycans and glycosylphosphatidylinositol (GPI) anchors. For example, G protein-coupled signaling receptors, adhesion molecules, cell surface enzymes, infectious agents such as prion protein, and pituitary hormones such as thyrotropin are all modified by sugars. Remarkably, half the mass of the HIV envelope glycoprotein gp120 is due to N-glycans that affect its immunogenicity as well as its ability to enter cells. The absence of N-glycans and GPI anchors is lethal, and glycosylation patterns are altered in devastating diseases such as cancer. Defects in glycosylation underlie more than 100 human genetic disorders, many of which are classified as Congenital Disorders of Glycosylation, a family of severe inherited diseases with neurological and other symptoms. Additionally, GPI-anchored proteins are critical for the viability of parasitic protozoa and fungi and constitute a valid therapeutic target for protozoal and fungal diseases.Despite the importance of glycosylation, major gaps remain in our understanding of how sugars are built into complex structures and appended to proteins. For example, assembly of the canonical oligosaccharide donor for N-glycosylation requires flipping of three glycolipids from the cytoplasmic to the luminal side of the endoplasmic reticulum (ER). Likewise, GPI anchoring of proteins requires flipping of a glycosylated phospholipid across the ER. As polar lipids do not flip-flop spontaneously across membranes at an appreciable rate, fast flipping requires proteins that facilitate lipid movement. There is compelling evidence that such proteins (flippases) exist, but remarkably their molecular identity is not known and consequently their mechanism is not understood. The identification of the ER glycolipid flippases is a major challenge for the field and their mechanism is an outstanding fundamental question in cell and structural biology.Our overall goal is to identify ER flippases that are central to the N-glycosylation and GPI biosynthetic pathways. With the identity of the proteins in hand we will eventually be able to address how they work. To accomplish our goal we have assembled an interdisciplinary Sinergia team. We have developed new methods, using organic chemistry and quantitative proteomics that exceed the state-of-the-art. By identifying new molecules we expect to generate a paradigm shift in how lipid transport processes are understood and further analyzed, and to fill in a long-standing gap in knowledge about basic glycosylation pathways. As the core glycosylation pathways are conserved in eukaryotes, we will use African trypanosomes and yeast for our studies, exploiting their genetic and biochemical advantages. All three Sinergia teams will work in close collaboration.