Project title
Unconventional protein secretion: Functional analysis of the plasma membrane nanodomain organisation driving FGF2 membrane translocation into the extracellular space
Summary
Fibroblast growth factor 2 (FGF2) is a tumor cell survival factor that belongs to a subgroup of extracellular proteins lacking N-terminal signal peptides. Whereas this phenomenon was already recognized in the early 1990s, detailed insights into the molecular mechanisms underlying alternative pathways of protein secretion from eukaryotic cells were obtained only recently. Today, we know about a number of alternative secretory mechanisms, collectively termed unconventional protein secretion (UPS). FGF2 belongs to a subgroup of cargo proteins secreted by direct translocation across the plasma membrane. This feature has been classified as type I UPS and is shared with other unconventionally secreted proteins, such as HIV-Tat and Tau. FGF2 translocation across the membrane is initiated through sequential interactions with the Na,K-ATPase, Tec kinase, and phosphoinositide PI(4,5)P2 at the inner plasma membrane leaflet. Whereas the first two are auxiliary factors of this pathway, the interaction of FGF2 with PI(4,5)P2 triggers the core mechanism of FGF2 membrane translocation. It is based on a lipidic membrane pore that is formed by PI(4,5)P2-induced oligomerization of FGF2. Membrane-inserted FGF2 oligomers are recognized as translocation intermediates that are resolved at the outer plasma membrane leaflet by glypican-1, a heparan sulfate proteoglycan that captures and disassembles FGF2 oligomers on cell surfaces. Recent findings suggest the molecular machinery mediating FGF2 membrane translocation to be highly organized in liquid-ordered plasma membrane nanodomains. The goal of this project will be to obtain detailed insights into the nanodomain organization of this process, providing a molecular understanding of the spatial and temporal coordination of FGF2 secretion into the extracellular space.
References
Lolicato F, Saleppico R, Griffo A, Meyer A, Scollo F, Pokrandt B, Müller HM, Ewers H, Hähl H, Fleury JB, Seemann R, Hof M, Brügger B, Jacobs K, Vattulainen I, Nickel W (2022) Cholesterol promotes clustering of PI(4,5)P2 driving unconventional secretion of FGF2. J Cell Biol e202106123
Sparn C, Meyer, A, Saleppico R, and Nickel W (2022) Unconventional secretion mediated by direct protein self-translocation across the plasma membranes of mammalian cells.
Trends Biochem Sci 47:699-709
Sparn C, Dimou E, Meyer A, Saleppico R, Wegehingel S, Gerstner M, Klaus S, Ewers H, Nickel W (2022) Glypican-1 drives unconventional secretion of Fibroblast Growth Factor 2. eLife e75545
Lolicato F and Nickel W (2022) A role for liquid-ordered plasma membrane nanodomains coordinating the unconventional secretory pathway of Fibroblast Groth Factor 2.
Front Cell Dev Biol 10:864257
Dimou E, Cosentino K, Platonova E, Ros U, Sadeghi M, Kashyap P, Katsinelos T, Wegehingel S, Noé F, García-Sáez AJ, Ewers H, Nickel W (2019) Single event visualization of unconventional secretion of FGF2. J Cell Biol 218:683-699
Dimou E and Nickel W (2018) Unconventional mechanisms of eukaryotic protein secretion.
Curr Biol 28:R406-R410
Steringer JP, Lange S, Čujová S, Šachl R, Poojari C, Lolicato F, Beutel O, Müller HM, Unger S, Coskun Ü, Honigmann A, Vattulainen I, Hof M, Freund C, Nickel W (2017) Key steps in unconventional secretion of fibroblast growth factor 2 reconstituted with purified components. eLife e28985
Methods that will be used
- Super-resolution STED and MinFlux microscopy
- Single molecule TIRF microscopy
- Biochemical and biophysical reconstitution experiments
- Molecular dynamics simulations
Cooperation partners
Dr. Holger Lorenz, ZMBH Imaging Facility, Heidelberg University
Prof. Helge Ewers, FU Berlin
Prof. Ilpo Vattulainen, Helsinki University
Prof. Martin Hof, Prague
Funding SFB/TRR 186; E13/60%
Personal qualifications
We are looking for highly motivated students with a master degree in biochemistry, biophysics, chemistry or molecular biology.
Keywords
advanced super-resolution microscopy, computational biology, molecular dynamics simulations, tumor cell survival, FGF2, fibroblast growth factor 2, protein secretion, membrane trafficking, protein translocation across membranes, membrane nanodomains, liquid-ordered membrane domains
Contact:
Walter Nickel
Office
: +49 6221 54-5425
Lab
: +49 6221 54-5427
Fax
: +49 6221 54-4366
E-Mail
: walter.nickel@bzh.uni-heidelberg.de