Fascin-induced actin protrusions are suppressed by dendritic networks in giant unilamellar vesicles |
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| Authors: | Nadab H Wubshet Yashar Bashirzadeh Allen P Liu |
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| Institution: | University of Pennsylvania;aDepartment of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109;bDepartment of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109;cCellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109;dDepartment of Biophysics, University of Michigan, Ann Arbor, MI, 48109 |
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| Abstract: | The interactions between actin networks and cell membrane are immensely important for eukaryotic cell functions including cell shape changes, motility, polarity establishment, and adhesion. Actin-binding proteins are known to compete and cooperate using a finite amount of actin monomers to form distinct actin networks. How actin-bundling protein fascin and actin-branching protein Arp2/3 complex compete to remodel membranes is not entirely clear. To investigate fascin- and Arp2/3-mediated actin network remodeling, we applied a reconstitution approach encapsulating bundled and dendritic actin networks inside giant unilamellar vesicles (GUVs). Independently reconstituted, membrane-bound Arp2/3 nucleation forms an actin cortex in GUVs, whereas fascin mediates formation of actin bundles that protrude out of GUVs. Coencapsulating both fascin and Arp2/3 complex leads to polarized dendritic aggregates and significantly reduces membrane protrusions, irrespective of whether the dendritic network is membrane bound or not. However, reducing Arp2/3 complex while increasing fascin restores membrane protrusion. Such changes in network assembly and the subsequent interplay with membrane can be attributed to competition between fascin and Arp2/3 complex to utilize a finite pool of actin. |
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