Membrane Curvature Sensing by Amphipathic Helices Is Modulated by the Surrounding Protein Backbone

PLoS One. 2015 Sep 14;10(9):e0137965. doi: 10.1371/journal.pone.0137965. eCollection 2015.

Abstract

Membrane curvature is involved in numerous biological pathways like vesicle trafficking, endocytosis or nuclear pore complex assembly. In addition to its topological role, membrane curvature is sensed by specific proteins, enabling the coordination of biological processes in space and time. Amongst membrane curvature sensors are the ALPS (Amphipathic Lipid Packing Sensors). ALPS motifs are short peptides with peculiar amphipathic properties. They are found in proteins targeted to distinct curved membranes, mostly in the early secretory pathway. For instance, the ALPS motif of the golgin GMAP210 binds trafficking vesicles, while the ALPS motif of Nup133 targets nuclear pores. It is not clear if, besides curvature sensitivity, ALPS motifs also provide target specificity, or if other domains in the surrounding protein backbone are involved. To elucidate this aspect, we studied the subcellular localization of ALPS motifs outside their natural protein context. The ALPS motifs of GMAP210 or Nup133 were grafted on artificial fluorescent probes. Importantly, ALPS motifs are held in different positions and these contrasting architectures were mimicked by the fluorescent probes. The resulting chimeras recapitulated the original proteins localization, indicating that ALPS motifs are sufficient to specifically localize proteins. Modulating the electrostatic or hydrophobic content of Nup133 ALPS motif modified its avidity for cellular membranes but did not change its organelle targeting properties. In contrast, the structure of the backbone surrounding the helix strongly influenced targeting. In particular, introducing an artificial coiled-coil between ALPS and the fluorescent protein increased membrane curvature sensitivity. This coiled-coil domain also provided membrane curvature sensitivity to the amphipathic helix of Sar1. The degree of curvature sensitivity within the coiled-coil context remains correlated to the natural curvature sensitivity of the helices. This suggests that the chemistry of ALPS motifs is a key parameter for membrane curvature sensitivity, which can be further modulated by the surrounding protein backbone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Cell Line
  • Cell Membrane / genetics
  • Cell Membrane / metabolism*
  • Cytoskeletal Proteins
  • Humans
  • Minor Histocompatibility Antigens
  • Monomeric GTP-Binding Proteins / genetics
  • Monomeric GTP-Binding Proteins / metabolism*
  • Nuclear Pore Complex Proteins / genetics
  • Nuclear Pore Complex Proteins / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*

Substances

  • Cytoskeletal Proteins
  • Minor Histocompatibility Antigens
  • NUP133 protein, human
  • Nuclear Pore Complex Proteins
  • Nuclear Proteins
  • TRIP11 protein, human
  • SAR1A protein, human
  • Monomeric GTP-Binding Proteins

Grants and funding

CMD is supported by the Centre National de la Recherche Scientifique and by a Marie Curie grant (IRG 277018) from the 7th Framework Programme for Research. BA is supported by an advanced grant from the European Research Council (ERC 268888). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.