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Molecular identification of lipid transporters for protein glycosylation

Applicant Bütikofer Peter
Number 170923
Funding scheme Sinergia
Research institution Institut für Biochemie und Molekulare Medizin Universität Bern
Institution of higher education University of Berne - BE
Main discipline Interdisciplinary
Start/End 01.02.2017 - 31.01.2021
Approved amount 2'262'246.00
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All Disciplines (3)

Discipline
Interdisciplinary
Biochemistry
Organic Chemistry

Keywords (8)

Dolichol; Synthesis of fluorescent glycolipids; Endoplasmic reticulum; N-glycosylation; Lipid flippases; Synthesis of click-chemistry lipids; GPI anchoring; Glycolipids

Lay Summary (German)

Lead
Viele Proteine (Eiweisse) werden durch Zuckerreste verändert, damit sie ihre biologischen Funktionen ausüben können. Diese sogenannten Glykoproteine dienen als Ziele für medikamentöse Therapien, lösen die Ausschüttung von Hormonen aus und sind bei der Übertragung von Nervenimpulsen beteiligt. Das Fehlen oder ein unvollständiges Anhängen der Zuckerreste führt zu schweren Krankheiten oder zum Tod. Zudem bilden viele für den Menschen tödliche Parasiten Glykoproteine, um sich damit vor unserem Immunsystem zu schützen. Wir untersuchen, wie Zuckerreste in Zellen bereitgestellt und transportiert werden.
Lay summary

Inhalte und Ziele des Forschungsprojekts

Trotz der zentralen Bedeutung der Glykoproteine sind entscheidende Schritte in der Herstellung der Überträgermoleküle von Zuckerresten noch ungeklärt. Interessanterweise beginnt die Produktion der Zuckerreste in der Zellflüssigkeit (Zytosol), deren Anhängen an die Proteine geschieht aber in einem speziellen Zellkompartiment, dem endoplasmatischen Retikulum. Das bedeutet, dass die Überträgermoleküle durch eine Membran hindurch transportiert werden müssen, bevor die Zucker an Proteine gekoppelt werden können. Über diese Transportprozesse ist kaum etwas bekannt. Wir haben uns zum Ziel gesetzt, in diesem interdisziplinären Forschungsprojekt zum ersten Mal die an der Herstellung von Glykoproteinen beteiligten Transportsysteme von Zuckerresten auf molekularer Ebene zu identifizieren und charakterisieren.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Transportvorgänge für Zuckerreste für die Herstellung von Glykoproteinen kommen sowohl bei einzelligen Organismen wie auch beim Menschen vor. Unsere Resultate werden deshalb für viele Forschungsrichtungen und die Medizin von zentraler Bedeutung sein.

Direct link to Lay Summary Last update: 18.12.2016

Responsible applicant and co-applicants

Employees

Project partner

Collaboration

Group / person Country
Types of collaboration
Dr. Johannes Graumann, Max Planck Institute for Heart and Lung Research, Bad Nauheim Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Graduate School Meeting University of Bern Poster Elucidating the interactome of T. brucei Rft1 31.01.2019 Bern, Switzerland Bütikofer Peter; Jenni Aurelio;
36th Annual Swiss Trypanosomatid Meeting Poster Elucidating the interactome of T. brucei Rft1 09.01.2019 Leysin, Switzerland Bütikofer Peter; Jenni Aurelio;
36th Annual Swiss Trypanosomatid Meeting Poster Investigating phospholipid scramblase activity in T. brucei detergent extracts 09.01.2019 Leysin, Switzerland Bütikofer Peter; Cowton Andrew;
International Conference on Retinal Proteins Individual talk Mechanism of phospholipid scrambling by a G-protein-coupled receptor 24.09.2018 Hockley Valley Resort, Canada Menon Anant K.;
Third Biosignal Research Center International Symposium Individual talk Mechanism of phospholipid scrambling by a G-protein-coupled receptor 19.09.2018 Kobe, Japan Menon Anant K.;
Annual Meeting of the Biophysical Society of Japan Individual talk Dimerization-deficient opsin mutants: implications for disease 15.09.2018 Okayama, Japan Menon Anant K.;
Fall Meeting, Swiss Chemical Society, EPF Lausanne, Poster Synthesis of molecular probes targeting ER flippases 07.09.2018 Lausanne, Switzerland Picca Giovanni; Häner Robert;
International Congress of Cell Biology ‘The Dynamic Cell’ Individual talk Moving lipids within cells 27.01.2018 Hyderabad, India Menon Anant K.;
Society for Glycobiology Annual Meeting Individual talk Identifying lipid scramblases for dolichol-based glycolipids involved in protein N-glycosylation in the endoplasmic reticulum 05.11.2017 Portland, OR, United States of America Menon Anant K.;


Self-organised

Title Date Place
36th Annual Swiss Trypanosomatid Meeting 09.01.2019 Leysin, Switzerland

Abstract

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.
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