Finger-like membrane protrusions are favored by heterogeneities in the actin network

Shachar Gat (1) , Camille Simon (2) , Clément Campillo (3) , Anne Bernheim-Groswasser (1) , C. Sykes (2)

1 BGU - Ben-Gurion University of the Negev
2 PCC - Laboratoire Physico-Chimie Curie [Institut Curie]
3 LAMBE - UMR 8587 - Laboratoire Analyse, Modélisation et Matériaux pour la Biologie et l'Environnement

Finger-like protrusions in cells are mostly generated by an active actin cytoskeleton pushing against the cell membrane. Conventional filopodia, localized at the leading edge of the cells, are long and thin protrusions composed of parallel actin filaments that emanate from a branched actin network. In contrast, dendritic filopodia, precursors of dendritic spines in neurons, are entirely filled in with a branched actin network. Here, we investigate in vitro how the dynamics of branched actin structures, polymerized at a membrane surface, trigger the formation of both protrusion types. Using supported bilayers and liposomes, we show that a decrease in the amount of activation sites at the membrane surface leads to the appearance of heterogeneities in the actin network coverage. Such heterogeneities promote the formation of membrane protrusions, and the size of heterogeneity patches matches the one of the protrusion base. Protrusion shape, cylindrical or conical, directly correlates with the absence or the presence of actin branches, respectively.

Domaines: Matière Molle [cond-mat.soft]; Biophysique [physics.bio-ph]

Shachar Gat, Camille Simon, Clément Campillo, Anne Bernheim-Groswasser, C. Sykes. Finger-like membrane protrusions are favored by heterogeneities in the actin network. Soft Matter, 2020, 16 (31), pp.7222-7230. ⟨10.1039/c9sm02444a⟩. ⟨hal-03014841⟩