IRSp53 senses negative membrane curvature and phase separates along membrane tubules

Coline Prévost (1, 2) , Hongxia Zhao (3) , John Manzi (1) , Emmanuel Lemichez (4) , Pekka Lappalainen (3) , Andrew Callan-Jones (2, 5) , Patricia Bassereau (1)

1 PCC - Physico-Chimie-Curie
2 UPD7 - Université Paris Diderot - Paris 7
3 BI - HiLIFE - Institute of Biotechnology [Helsinki]
4 C3M - Centre méditerranéen de médecine moléculaire
5 MSC - Matière et Systèmes Complexes

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.

Mots clés: Filopodia; Membrane curvature; Membrane proteins

Domaines: Sciences du Vivant [q-bio]; Microbiologie et Parasitologie; Bactériologie; Biologie cellulaire; Organisation et fonctions cellulaires [q-bio.SC]; Interactions cellulaires [q-bio.CB]

Coline Prévost, Hongxia Zhao, John Manzi, Emmanuel Lemichez, Pekka Lappalainen, et al.. IRSp53 senses negative membrane curvature and phase separates along membrane tubules. Nature Communications, 2015, 6 (1), pp.8529. ⟨10.1038/ncomms9529⟩. ⟨pasteur-02453826⟩