Cofilactin filaments regulate filopodial structure and dynamics in neuronal growth cones

Hylton, Ryan; Heebner, Jessica; Grillo, Michael A.; Swulius, Matthew T.

doi:10.1038/s41467-022-30116-x

Cited by 39 publications

(27 citation statements)

References 73 publications

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“…2D projection images were lowpass-filtered using mtffilter in IMOD. Segmentations were generated in Dragonfly (Object Research Systems, 2022; www.theobjects.com/dragonfly ) as described previously 107 . In brief, isonet-filtered tomograms were further processed by histogram equalization and an unsharp filter, and a 5-class U-Net (with 2.5D input of 5 slices) was trained on 5–6 tomogram slices to recognize background voxels, filaments, membranes, cell surface structures and ribosomes.…”

Section: Methodsmentioning

confidence: 99%

Actin cytoskeleton and complex cell architecture in an Asgard archaeon

Rodrigues-Oliveira

Wollweber

Ponce‐Toledo

et al. 2022

Nature

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Asgard archaea are considered to be the closest known relatives of eukaryotes. Their genomes contain hundreds of eukaryotic signature proteins (ESPs), which inspired hypotheses on the evolution of the eukaryotic cell1–3. A role of ESPs in the formation of an elaborate cytoskeleton and complex cellular structures has been postulated4–6, but never visualized. Here we describe a highly enriched culture of ‘Candidatus Lokiarchaeum ossiferum’, a member of the Asgard phylum, which thrives anaerobically at 20 °C on organic carbon sources. It divides every 7–14 days, reaches cell densities of up to 5 × 107 cells per ml and has a significantly larger genome compared with the single previously cultivated Asgard strain7. ESPs represent 5% of its protein-coding genes, including four actin homologues. We imaged the enrichment culture using cryo-electron tomography, identifying ‘Ca. L. ossiferum’ cells on the basis of characteristic expansion segments of their ribosomes. Cells exhibited coccoid cell bodies and a network of branched protrusions with frequent constrictions. The cell envelope consists of a single membrane and complex surface structures. A long-range cytoskeleton extends throughout the cell bodies, protrusions and constrictions. The twisted double-stranded architecture of the filaments is consistent with F-actin. Immunostaining indicates that the filaments comprise Lokiactin—one of the most highly conserved ESPs in Asgard archaea. We propose that a complex actin-based cytoskeleton predated the emergence of the first eukaryotes and was a crucial feature in the evolution of the Asgard phylum by scaffolding elaborate cellular structures.

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Section: Methodsmentioning

confidence: 99%

Actin cytoskeleton and complex cell architecture in an Asgard archaeon

Rodrigues-Oliveira

Wollweber

Ponce‐Toledo

et al. 2022

Nature

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“…It is activated both by cellular stresses, such as energy depletion (Nishida et al, 1987;Meberg et al, 1998;Minamide et al, 2000), and by signaling pathways, particularly those found at the leading edge of the cell (Arber et al, 1998;Meberg et al, 1998;Yang et al, 1998;Chan et al, 2000;Zebda et al, 2000;Endo et al, 2003). Indeed, filaments resembling cofilactin have been observed in the cytoplasm of neuronal growth cones in two recent cryoET studies (Atherton et al, 2022;Hylton et al, 2022). It remains to be seen whether cofilactin can also accumulate in the microtubule lumen during cell migration.…”

Section: Luminal Filaments Have Altered Morphology In Cofilin Knock-d...mentioning

confidence: 99%

CryoET shows cofilactin filaments inside the microtubule lumen

Rogers

Carter

2023

Preprint

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Cytoplasmic microtubules are tubular polymers that can harbor small proteins or filaments inside their lumen. The identity of these objects and what causes their accumulation has not been conclusively established. Here, we used cryogenic electron tomography (cryoET) of Drosophila S2 cell protrusions and found filaments inside the microtubule lumen, which resemble those reported recently in human HAP1 cells. The frequency of these filaments increased upon inhibition of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) with the small-molecule drug thapsigargin. Subtomogram averaging showed that the luminal filaments adopt a helical structure reminiscent of cofilin-bound actin (cofilactin). Consistent with this, cofilin was activated in cells under the same conditions that increased luminal filament occurrence. Furthermore, RNAi knock-down of cofilin reduced the frequency of luminal filaments with cofilactin morphology. These results suggest that cofilin activation stimulates its accumulation on actin filaments inside the microtubule lumen.

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“…Nat Commun. 13(1):2439. doi: 10.1038/s41467-022-30116-x 59 . ( C ) in vitro polymerized F-actin co-incubated with no protein, Drosophila Septins, human Septins, or Fascin.…”

Section: Introductionmentioning

confidence: 99%

“…However, saturated cofilactin filaments are no longer severed cofilin-dependently and are more flexible 50 , 52 , 58 . While examining actin bundles within filopodia at neuronal growth cones using cryo-electron tomography, Hylton and colleagues recently showed that cofilactin filaments associate with curvature of the actin bundles, thereby regulating filopodia structure and dynamics 59 . Interestingly, this cofilactin filament conformational change results in an exclusion of the Fascin actin-crosslinking protein from cofilactin bundles, leading to less organized actin filament bundling, the bending of filopodial protrusions, and a disruption of filopodial structure and functions ( Figure 2B ) 59 .…”

Section: Introductionmentioning

confidence: 99%

Bending actin filaments: twists of fate

Nakamura¹,

Hui²,

Parkhurst³

2023

Fac Rev

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In many cellular contexts, intracellular actomyosin networks must generate directional forces to carry out cellular tasks such as migration and endocytosis, which play important roles during normal developmental processes. A number of different actin binding proteins have been identified that form linear or branched actin, and that regulate these filaments through activities such as bundling, crosslinking, and depolymerization to create a wide variety of functional actin assemblies. The helical nature of actin filaments allows them to better accommodate tensile stresses by untwisting, as well as to bend to great curvatures without breaking. Interestingly, this latter property, the bending of actin filaments, is emerging as an exciting new feature for determining dynamic actin configurations and functions. Indeed, recent studies using in vitro assays have found that proteins including IQGAP, Cofilin, Septins, Anillin, α-Actinin, Fascin, and Myosins—alone or in combination—can influence the bending or curvature of actin filaments. This bending increases the number and types of dynamic assemblies that can be generated, as well as the spectrum of their functions. Intriguingly, in some cases, actin bending creates directionality within a cell, resulting in a chiral cell shape. This actin-dependent cell chirality is highly conserved in vertebrates and invertebrates and is essential for cell migration and breaking L-R symmetry of tissues/organs. Here, we review how different types of actin binding protein can bend actin filaments, induce curved filament geometries, and how they impact on cellular functions.

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Cofilactin filaments regulate filopodial structure and dynamics in neuronal growth cones

Cited by 39 publications

References 73 publications

Actin cytoskeleton and complex cell architecture in an Asgard archaeon

Actin cytoskeleton and complex cell architecture in an Asgard archaeon

CryoET shows cofilactin filaments inside the microtubule lumen

Bending actin filaments: twists of fate

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