Confinement Geometry Tunes Fascin-Actin Bundle Structures and Consequently the Shape of a Lipid Bilayer Vesicle

Bashirzadeh, Yashar; Wubshet, Nadab; Liu, Allen

doi:10.3389/fmolb.2020.610277

Cited by 36 publications

(46 citation statements)

References 52 publications

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“…Fascin is a short crosslinker that crosslinks actin filaments into parallel and tight bundles. Depending on the concentration of fascin and the size confinement space, fascin is known to induce membrane protrusions (Tsai and Koenderink, 2015;Bashirzadeh et al, 2020b); whereas, membrane-bound activation of Arp2/3 complex nucleates actin to form a dendritic cortex (Liu et al, 2008). Consistent with prior work (Liu et al, 2008), reconstitution of a dendritic actin cortex on the external membrane leaflet results in membrane protrusions directed towards the GUV lumen.…”

Section: Resultssupporting

confidence: 53%

“…All lipids were purchased from Avanti Polar Lipids (Alabaster, AL). We modified continuous droplet interface crossing encapsulation (cDICE) technique for robust encapsulation in GUVs of various sizes as previously reported (Bashirzadeh et al, 2020b). Briefly, a custom 3D-printed chamber is mounted on a benchtop stir plate and rotated at 1,200 rpm.…”

Section: Production Of Guvsmentioning

confidence: 99%

“…Co-encapsulation of multiple actin binding proteins in previous studies have revealed formation of emergent structures as a result of either synergy or competition between different actin binding proteins. It was shown recently that the co-encapsulation of αactinin together with fascin impairs the formation of protrusive bundled actin structures (Bashirzadeh et al, 2020b). Similarly, others have shown that membrane remodeling caused by an Arp2/3-induced actin cortex can be tuned by changing the concentration of capping protein (Dürre et al, 2018).…”

Section: Introductionmentioning

confidence: 98%

“…As an alternative experimental system, others have biochemically reconstituted actin networks on the outside surface or inside giant unilamellar vesicles (GUVs) to independently study actin networks formed by fascin and Arp2/3 complex and their respective interaction with lipid membranes. For example, when encapsulated inside a GUV, fascin was shown to form actin bundles which induced reversible membrane protrusions or formed contractile rings (Tsai and Koenderink, 2015;Bashirzadeh et al, 2020b;Litschel et al, 2021). When polymerized on the outside, reconstitution of Arp2/3-branched network led to the emergence of short filopodium-like actin protrusions into the GUV lumen in the absence of fascin (Liu et al, 2008;Simon et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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

Wubshet

Bashirzadeh

Liu

2021

MBoC

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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 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. Co-encapsulating 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. [Media: see text] [Media: see text]

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Section: Resultssupporting

confidence: 53%

Section: Production Of Guvsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Wubshet

Bashirzadeh

Liu

2021

MBoC

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“…In contrast to the results above, the crosslinker fascin formed actin bundles that were sufficiently rigid to stably deform GUVs or were sharply kinked by the membrane as expected (Supplementary Fig. S5) 32 . Fascin alone was unable to induce F-actin clustering or the formation of peripheral or central actin asters.…”

Section: α-Actinin Induces Aggregation and Guv Size-dependent Formatimentioning

confidence: 46%

Actin crosslinker competition and sorting drive emergent GUV size-dependent actin network architecture

Bashirzadeh

Redford

Lorpaiboon

et al. 2020

Preprint

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Robust spatiotemporal organization of cytoskeletal networks is crucial, enabling cellular processes such as cell migration and division. α-Actinin and fascin are two actin crosslinking proteins localized to distinct regions of eukaryotes to form actin bundles with optimized spacing for cell contractile machinery and sensory projections, respectively. In vitro reconstitution assays and coarse-grained simulations have shown that these actin bundling proteins segregate into distinct domains with a bundler size-dependent competition-based mechanism, driven by the minimization of F-actin bending energy. However, it is not known how physical confinement imposed by the cell membrane contributes to sorting of actin bundling proteins and the concomitant reorganization of actin networks in intracellular environment. Here, by encapsulating actin, α-actinin, and fascin in giant unilamellar vesicles (GUVs), we show that the size of such a spherical boundary determines equilibrated structure of actin networks among three typical structures: single rings, astral structures, and star-like structures. We show that α-actinin bundling activity and its tendency for clustering actin is central to the formation of these structures. By analyzing physical features of crosslinked actin networks, we show that spontaneous sorting and domain formation of α-actinin and fascin are intimately linked to the resulting structures. We propose that the observed boundary-imposed effect on sorting and structure formation is a general mechanism by which cells can select between different structural dynamical steady states.

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Protocells Capable of Generating a Cytoskeleton‐Like Structure from Intracellular Membrane‐Active Artificial Organelles

Wang,

Moreno,

Gao

et al. 2023

Adv Funct Materials

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The intricate nature of eukaryotic cells with intracellular compartments having differences in component concentration and viscosity in their lumen provides (membrane‐active) enzymes to trigger time‐ and concentration‐dependent processes in the intra‐/extracellular matrix. Herein, membrane‐active, enzyme‐loaded artificial organelles (AOs) are capitalized upon to develop fluidic and stable proteinaceous membrane‐based protocells. AOs in protocells induce the self‐assembly of oligopeptides into an artificial cytoskeleton that underlines their influence on the structure and functionality of protocells. A series of microscopical tools is used to validate the intracellular assembly and distribution of cytoskeleton, the changing protocells morphology, and AOs inclusion within cytoskeletal growth. Thus, the dynamics, diffusion, and viscosity of intracellular components in the presence of cytoskeleton are evaluated by fluorescence tools and enzymatic assay. Membrane‐active alkaline phosphatase in polymersomes as AOs fulfills the requirements of biomimetic eukaryotic cells to trigger intracellular environment, mobility, viscosity, diffusion, and enzymatic activity itself as well as high mechanical stability and high membrane fluidity of protocells. Thus membrane‐active AOs in protocells provide a variable reaction space in a changing intracellular environment and underline their regulatory role in the fabrication of complex protocell architectures and functions. This study contributes significantly to the effective biomimetics of cell‐like structures, shapes, and functions.

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Confinement Geometry Tunes Fascin-Actin Bundle Structures and Consequently the Shape of a Lipid Bilayer Vesicle

Cited by 36 publications

References 52 publications

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

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

Actin crosslinker competition and sorting drive emergent GUV size-dependent actin network architecture

Protocells Capable of Generating a Cytoskeleton‐Like Structure from Intracellular Membrane‐Active Artificial Organelles

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