Filopodia are actin-rich membrane protrusions essential for cell morphogenesis, motility, and cancer invasion. How cells control filopodium initiation on the plasma membrane remains elusive. We performed experiments in cellulo, in vitro, and in silico to unravel the mechanism of filopodium initiation driven by the membrane curvature sensor IRSp53 (insulin receptor substrate protein of 53 kDa). We showed that full-length IRSp53 self-assembles into clusters on membranes depending on PIP2. Using well-controlled in vitro reconstitution systems, we demonstrated that IRSp53 clusters recruit the actin polymerase VASP (vasodilator-stimulated phosphoprotein) to assemble actin filaments locally on membranes, leading to the generation of actin-filled membrane protrusions reminiscent of filopodia. By pulling membrane nanotubes from live cells, we observed that IRSp53 can only be enriched and trigger actin assembly in nanotubes at highly dynamic membrane regions. Our work supports a regulation mechanism of IRSp53 in its attributes of curvature sensation and partner recruitment to ensure a precise spatial-temporal control of filopodium initiation.
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Title
Activated I-BAR IRSp53 clustering controls the formation of VASP-actin–based membrane protrusions
Data availability statement
All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials.
Funding Information
National Institute of General Medical Sciences, R01-GM063796 Takeda Science Foundation Horizon 2020 Framework Programme, RGP0005/2016 Wesco Science Foundation Marie Curie Actions, H2020-MSCA-IF-2014 EMBO, long-term fellowship, ALTF 1527-2014 Human Frontier Science Program, RGP0005/2016 Institut Curie and the Centre National de la Recherche Scientifique Agence Nationale Pour La Recherche, ANR-20-CE13-0032 Université Paris Sciences et Lettres-QLife Institute, ANR-17-CONV-0005 Q-LIFE Agence Nationale Pour La Recherche, ANR-20-CE13-0032 Agence Nationale Pour La Recherche, ANR-18-CE13-0026-01 Agence Nationale Pour La Recherche, ANR-21-CE13-0010-03 Cancer Society Finland, 4705949 Japan Society for the Promotion of Science and Academy of Finland, FY 2015 Researcher Exchange Program Wesco Scientific Promotion Foundation Pasteur Foundation, Fellowship
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