Berlin 2018 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 6: Cytoskeletal Filaments I

BP 6.6: Vortrag

Montag, 12. März 2018, 16:30–16:45, H 1058

Actin dynamics deform membrane in and out mimicking filopodia and endocytosis — •Camille Simon¹, Remy Kusters¹, Valentina Caorsi¹, Jean-François Joanny², Clément Campillo³, Julie Plastino¹, Pierre Sens¹, and Cécile Sykes¹ — ¹Institut Curie, Paris, France — ²ESPCI, Paris, France — ³Université Evry Val d'Essonne, Evry, France

The cell membrane is able to deform inward, as in endocytosis intitiation, or outward, as in filopodia formation. Interestingly, both deformations are generated by the same branched, Arp2/3-based, polymerizing actin network. How an inward or an outward deformation can result from the same network structure? What are the physical parameters that will trigger the direction of membrane deformation? To address these questions, we use a reconstituted membrane system of liposomes and purified actin. A dynamic branched actin network is generated at the liposome surface. We investigate the conditions under which the actin cytoskeleton induces inward or outward membrane deformations. We reveal that actin dynamics is the sole player of membrane deformations by photo-damaging the actin structure that relaxes membrane shape. Lowering membrane tension is key to produce filopodia-like structures. Oppositely, endocytic-like structures are robust features that only weakly depend on membrane tension. A pulse-chase two color actin experiment reveals the details of network growth during inward or outward membrane deformation. Our results, supported by theoretical models, explain how such deformations depend on a mechanical balance between the membrane and the actin network.