1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics
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Key steps in unconventional secretion of fibroblast growth factor 2 reconstituted with purified components

  1. Julia P Steringer
  2. Sascha Lange
  3. Sabína Čujová
  4. Radek Šachl
  5. Chetan Poojari
  6. Fabio Lolicato
  7. Oliver Beutel
  8. Hans-Michael Müller
  9. Sebastian Unger
  10. Ünal Coskun
  11. Alf Honigmann
  12. Ilpo Vattulainen
  13. Martin Hof
  14. Christian Freund
  15. Walter Nickel  Is a corresponding author
  1. Heidelberg University, Germany
  2. Freie Universität Berlin, Germany
  3. Academy of Sciences of the Czech Republic, Czech Republic
  4. University of Helsinki, Finland
  5. Max Planck Institute of Molecular Cell Biology and Genetics, Germany
  6. Paul Langerhans Institute Dresden, Germany
Research Article
  • Cited 24
  • Views 2,675
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Cite this article as: eLife 2017;6:e28985 doi: 10.7554/eLife.28985

Abstract

FGF2 is secreted from cells by an unconventional secretory pathway. This process is mediated by direct translocation across the plasma membrane. Here, we define the minimal molecular machinery required for FGF2 membrane translocation in a fully reconstituted inside-out vesicle system. FGF2 membrane translocation is thermodynamically driven by PI(4,5)P2-induced membrane insertion of FGF2 oligomers. The latter serve as dynamic translocation intermediates of FGF2 with a subunit number in the range of 8-12 FGF2 molecules. Vectorial translocation of FGF2 across the membrane is governed by sequential and mutually exclusive interactions with PI(4,5)P2 and heparan sulfates on opposing sides of the membrane. Based on atomistic molecular dynamics simulations, we propose a mechanism that drives PI(4,5)P2 dependent oligomerization of FGF2. Our combined findings establish a novel type of self-sustained protein translocation across membranes revealing the molecular basis of the unconventional secretory pathway of FGF2.

Article and author information

Author details

  1. Julia P Steringer

    Heidelberg University Biochemistry Center, Heidelberg University, Heidelberg, Germany
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9418-2762
  2. Sascha Lange

    Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
    Competing interests
    The authors declare that no competing interests exist.
  3. Sabína Čujová

    J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
    Competing interests
    The authors declare that no competing interests exist.
  4. Radek Šachl

    J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
    Competing interests
    The authors declare that no competing interests exist.
  5. Chetan Poojari

    Department of Physics, University of Helsinki, Helsinki, Finland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6575-221X
  6. Fabio Lolicato

    Department of Physics, University of Helsinki, Helsinki, Finland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7537-0549
  7. Oliver Beutel

    Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
    Competing interests
    The authors declare that no competing interests exist.
  8. Hans-Michael Müller

    Heidelberg University Biochemistry Center, Heidelberg University, Heidelberg, Germany
    Competing interests
    The authors declare that no competing interests exist.
  9. Sebastian Unger

    Heidelberg University Biochemistry Center, Heidelberg University, Heidelberg, Germany
    Competing interests
    The authors declare that no competing interests exist.
  10. Ünal Coskun

    Paul Langerhans Institute Dresden, Dresden, Germany
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4375-3144
  11. Alf Honigmann

    Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
    Competing interests
    The authors declare that no competing interests exist.
  12. Ilpo Vattulainen

    Department of Physics, University of Helsinki, Helsinki, Finland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7408-3214
  13. Martin Hof

    J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
    Competing interests
    The authors declare that no competing interests exist.
  14. Christian Freund

    Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
    Competing interests
    The authors declare that no competing interests exist.
  15. Walter Nickel

    Heidelberg University Biochemistry Center, Heidelberg University, Heidelberg, Germany
    For correspondence
    walter.nickel@bzh.uni-heidelberg.de
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6496-8286

Funding

Deutsche Forschungsgemeinschaft (SFB 854)

  • Christian Freund

Deutsche Forschungsgemeinschaft (SFB 958)

  • Christian Freund

Czech Science Foundation (14-03141)

  • Sabína Čujová
  • Radek Šachl
  • Martin Hof

European Research Council (Advanced Grant 290974 CROWDED-PRO-LIPIDS)

  • Chetan Poojari
  • Fabio Lolicato
  • Ilpo Vattulainen

Academy of Finland (Center of Excellence projects 307415)

  • Chetan Poojari
  • Fabio Lolicato
  • Ilpo Vattulainen

Sigrid Juselius Foundation

  • Chetan Poojari
  • Fabio Lolicato
  • Ilpo Vattulainen

Deutsche Forschungsgemeinschaft (SFB/TRR 83)

  • Christian Freund
  • Walter Nickel

Deutsche Forschungsgemeinschaft (SFB/TRR 186)

  • Walter Nickel

Deutsche Forschungsgemeinschaft (DFG Ni 423/6-1)

  • Walter Nickel

Academy of Finland (Center of Excellence projects 272130)

  • Chetan Poojari
  • Fabio Lolicato
  • Ilpo Vattulainen

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Christopher G Burd, Yale School of Medicine, United States

Publication history

  1. Received: May 25, 2017
  2. Accepted: July 14, 2017
  3. Accepted Manuscript published: July 19, 2017 (version 1)
  4. Accepted Manuscript updated: July 27, 2017 (version 2)
  5. Version of Record published: September 15, 2017 (version 3)
  6. Version of Record updated: October 5, 2017 (version 4)

Copyright

© 2017, Steringer et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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