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Nat Commun. 2015 Oct 15;6:8529. doi: 10.1038/ncomms9529.

IRSp53 senses negative membrane curvature and phase separates along membrane tubules.

Author information

1
Institut Curie, Centre de Recherche, 75248 Paris Cedex 05, France.
2
CNRS, Physico-Chimie Curie, UMR 168, 75248 Paris Cedex 05, France.
3
Université Pierre et Marie Curie, 75252 Paris Cedex 05, France.
4
Université Paris-Diderot, 75205 Paris Cedex 05, France.
5
Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
6
INSERM, U1065, UNSA, Centre Méditerranéen de Médecine Moléculaire, C3M, 06204 Nice Cedex 3, France.
7
CNRS, Laboratoire Matière et Systèmes Complexes, UMR 7057, 75205 Paris Cedex 13, France.

Abstract

BAR domain proteins contribute to membrane deformation in diverse cellular processes. The inverted-BAR (I-BAR) protein IRSp53, for instance, is found on the inner leaflet of the tubular membrane of filopodia; however its role in the formation of these structures is incompletely understood. Here we develop an original assay in which proteins are encapsulated in giant unilamellar vesicles connected to membrane nanotubes. Our results demonstrate that I-BAR dimers sense negative membrane curvature. Experiment and theory reveal that the I-BAR displays a non-monotonic sorting with curvature, and expands the tube at high imposed tension while constricting it at low tension. Strikingly, at low protein density and tension, protein-rich domains appear along the tube. This peculiar behaviour is due to the shallow intrinsic curvature of I-BAR dimers. It allows constriction of weakly curved membranes coupled to local protein enrichment at biologically relevant conditions. This might explain how IRSp53 contributes in vivo to the initiation of filopodia.

PMID:
26469246
PMCID:
PMC4634128
DOI:
10.1038/ncomms9529
[Indexed for MEDLINE]
Free PMC Article

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