Fascin-induced actin protrusions are suppressed by dendritic networks in giant unilamellar vesicles

Mol Biol Cell. 2021 Aug 19;32(18):1634-1640. doi: 10.1091/mbc.E21-02-0080. Epub 2021 Jun 16.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Video-Audio Media

MeSH terms

  • Actin Cytoskeleton / chemistry
  • Actin Cytoskeleton / metabolism
  • Actin Cytoskeleton / ultrastructure*
  • Actin-Related Protein 2-3 Complex / genetics
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Animals
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Phosphatidylcholines / chemistry
  • Unilamellar Liposomes / chemistry
  • Unilamellar Liposomes / metabolism*

Substances

  • Actin-Related Protein 2-3 Complex
  • Carrier Proteins
  • Microfilament Proteins
  • Phosphatidylcholines
  • Unilamellar Liposomes
  • fascin
  • 1,2-oleoylphosphatidylcholine