Helical buckling of actin inside filopodia generates traction

Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell–cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.

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Development of macrociliary cells in Beroe. I. Actin bundles and centriole migration

Journal of Cell Science ◽

10.1242/jcs.89.1.67 ◽

1988 ◽

Vol 89 (1) ◽

pp. 67-80

Author(s):

S. Tamm ◽

S.L. Tamm

Keyword(s):

Cell Membrane ◽

Basal Body ◽

Actin Filaments ◽

Close Association ◽

Directed Assembly ◽

Double Layers ◽

Basal Bodies ◽

Apical Surface ◽

Actin Bundle ◽

Microfilament Bundle

Differentiation of macrociliary cells on regenerating lips of the ctenophore Beroe was studied by transmission electron microscopy. In this study of early development, we found that basal bodies for macrocilia arise by an acentriolar pathway near the nucleus and Golgi apparatus, in close association with plaques of dense fibrogranular bodies. Procentrioles are often aligned side-by-side in double layers with the cartwheel ends facing outward toward the surrounding plaques of dense granules. Newly formed basal bodies then disband from groups and develop a long striated rootlet at one end. At the same time, an array of microfilaments arises in the basal cytoplasm. The microfilaments are arranged in parallel strands oriented toward the cell surface. The basal body-rootlet units are transported to the apical surface in close association with the assembling actin filament bundle. Microfilaments run parallel to and alongside the striated rootlets, to which they often appear attached. Basal body-rootlet units migrate at the heads of trails of microfilaments, as if they are pushed upwards by elongation of their attached actin filaments. Near the apical surface the actin bundle curves and runs below the cell membrane. Newly arrived basal body-rootlets tilt upwards out of the microfilament bundle to contact the cell membrane and initiate ciliogenesis. The basal bodies tilt parallel to the flat sides of the rootlets, and away from the direction in which the basal feet point. The actin bundle continues to enlarge during ciliogenesis. These results suggest that basal body migration may be driven by the directed assembly of attached actin filaments.

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Lysosomal Exocytosis, Exosome Release and Secretory Autophagy: The Autophagic- and Endo-Lysosomal Systems Go Extracellular

International Journal of Molecular Sciences ◽

10.3390/ijms21072576 ◽

2020 ◽

Vol 21 (7) ◽

pp. 2576 ◽

Cited By ~ 15

Author(s):

Sandra Buratta ◽

Brunella Tancini ◽

Krizia Sagini ◽

Federica Delo ◽

Elisabetta Chiaradia ◽

...

Keyword(s):

Plasma Membrane ◽

Molecular Mechanisms ◽

Current Knowledge ◽

Cell Communication ◽

Lysosomal Storage ◽

Cellular Processes ◽

Age Related ◽

Extracellular Release ◽

A Cell ◽

Endosomal System

Beyond the consolidated role in degrading and recycling cellular waste, the autophagic- and endo-lysosomal systems play a crucial role in extracellular release pathways. Lysosomal exocytosis is a process leading to the secretion of lysosomal content upon lysosome fusion with plasma membrane and is an important mechanism of cellular clearance, necessary to maintain cell fitness. Exosomes are a class of extracellular vesicles originating from the inward budding of the membrane of late endosomes, which may not fuse with lysosomes but be released extracellularly upon exocytosis. In addition to garbage disposal tools, they are now considered a cell-to-cell communication mechanism. Autophagy is a cellular process leading to sequestration of cytosolic cargoes for their degradation within lysosomes. However, the autophagic machinery is also involved in unconventional protein secretion and autophagy-dependent secretion, which are fundamental mechanisms for toxic protein disposal, immune signalling and pathogen surveillance. These cellular processes underline the crosstalk between the autophagic and the endosomal system and indicate an intersection between degradative and secretory functions. Further, they suggest that the molecular mechanisms underlying fusion, either with lysosomes or plasma membrane, are key determinants to maintain cell homeostasis upon stressing stimuli. When they fail, the accumulation of undigested substrates leads to pathological consequences, as indicated by the involvement of autophagic and lysosomal alteration in human diseases, namely lysosomal storage disorders, age-related neurodegenerative diseases and cancer. In this paper, we reviewed the current knowledge on the functional role of extracellular release pathways involving lysosomes and the autophagic- and endo-lysosomal systems, evaluating their implication in health and disease.

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LOCOMOTION OF A TWO DIMENSIONAL KERATOCYTE MODEL

Journal of Biological System ◽

10.1142/s0218339001000396 ◽

2001 ◽

Vol 09 (03) ◽

pp. 201-219 ◽

Cited By ~ 7

Author(s):

R. SAMBETH ◽

A. BAUMGAERTNER

Keyword(s):

Cell Membrane ◽

Actin Filaments ◽

Structural Organization ◽

Constant Flow ◽

Nonequilibrium Distribution ◽

Cell Velocity ◽

Model Cell ◽

A Cell ◽

Asymmetric Polymerization ◽

Rectification Process

The polymerization-induced propulsion of a model cell consisting of a cell membrane enclosing mobile actin molecules and polymerizing actin filaments is studied using Monte Carlo methods. It is shown that asymmetric polymerization alone induces a rectified motion of the cell. The structural organization of the locomoting cell exhibits an anisotropic shape induced by the anisotropic distribution of actin within the cell. This nonequilibrium distribution is maintained by a constant flow of actin molecules from the rear to the front of the cell. The efficiency of the rectification process, and hence the cell velocity, depends cooperatively on the density of actin molecules. The maximum of the cell velocity is determined by the optimal interplay between the number of filaments and the fluctuation of the cell membrane.

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Membrane-mediated interactions induce spontaneous filament bundling

10.1101/336545 ◽

2018 ◽

Cited By ~ 1

Author(s):

Afshin Vahid ◽

George Dadunashvili ◽

Timon Idema

Keyword(s):

Actin Filaments ◽

Living Cells ◽

Natural Consequence ◽

Microtubule Network ◽

Parallel Structures ◽

Pulling Forces ◽

Membrane Protrusions ◽

A Cell ◽

Cytoskeletal Elements ◽

Pushing And Pulling

AbstractThe plasma membrane and cytoskeleton of living cells are closely coupled dynamical systems. Internal cytoskeletal elements such as actin filaments and microtubules continually exert forces on the membrane, resulting in the formation of membrane protrusions. In this paper we investigate the interplay between the shape of a cell distorted by pushing and pulling forces generated by microtubules and the resulting rearrangement of the microtubule network. From analytical calculations, we find that two microtubules that deform the vesicle can both attract or repel each other, depending on their angular separations and the direction of the imposed forces. We also show how the existence of attractive interactions between multiple microtubules can be deduced analytically, and further explore general interactions through Monte Carlo simulations. Our results suggest that the commonly reported parallel structures of microtubules in both biological and artificial systems can be a natural consequence of membrane mediated interactions.

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Faculty Opinions recommendation of A cell-cell communication signal integrates quorum sensing and stress response.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.717995806.793476388 ◽

2013 ◽

Author(s):

Fergal O'Gara

Keyword(s):

Stress Response ◽

Quorum Sensing ◽

Cell Communication ◽

Communication Signal ◽

A Cell ◽

Cell Cell

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Integrated genomic analysis reveals regulatory pathways and dynamic landscapes of the tRNA transcriptome

Scientific Reports ◽

10.1038/s41598-021-83469-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zefang Sun ◽

Jia Tan ◽

Minqiong Zhao ◽

Qiyao Peng ◽

Mingqing Zhou ◽

...

Keyword(s):

Expression Profiles ◽

Genomic Analysis ◽

Rna Seq ◽

Regulatory Pathways ◽

Cellular Processes ◽

Dynamic Landscapes ◽

Rna Fragments ◽

A Cell ◽

Considerable Impact ◽

New Algorithms

AbstracttRNAs and tRNA-derived RNA fragments (tRFs) play various roles in many cellular processes outside of protein synthesis. However, comprehensive investigations of tRNA/tRF regulation are rare. In this study, we used new algorithms to extensively analyze the publicly available data from 1332 ChIP-Seq and 42 small-RNA-Seq experiments in human cell lines and tissues to investigate the transcriptional and posttranscriptional regulatory mechanisms of tRNAs. We found that histone acetylation, cAMP, and pluripotency pathways play important roles in the regulation of the tRNA gene transcription in a cell-specific manner. Analysis of RNA-Seq data identified 950 high-confidence tRFs, and the results suggested that tRNA pools are dramatically distinct across the samples in terms of expression profiles and tRF composition. The mismatch analysis identified new potential modification sites and specific modification patterns in tRNA families. The results also show that RNA library preparation technologies have a considerable impact on tRNA profiling and need to be optimized in the future.

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Modulation of Cell–Cell Interactions in Drosophila Oocyte Development

Cells ◽

10.3390/cells9020274 ◽

2020 ◽

Vol 9 (2) ◽

pp. 274

Author(s):

Matthew Antel ◽

Mayu Inaba

Keyword(s):

Cell Communication ◽

Cell Interaction ◽

Oocyte Development ◽

Suitable Model ◽

Physiological Regulation ◽

Temporal Regulation ◽

Cellular Processes ◽

Cellular Machinery ◽

Drosophila Ovary ◽

Cell Cell

The Drosophila ovary offers a suitable model system to study the mechanisms that orchestrate diverse cellular processes. Oogenesis starts from asymmetric stem cell division, proper differentiation and the production of fully patterned oocytes equipped with all the maternal information required for embryogenesis. Spatial and temporal regulation of cell-cell interaction is particularly important to fulfill accurate biological outcomes at each step of oocyte development. Progress has been made in understanding diverse cell physiological regulation of signaling. Here we review the roles of specialized cellular machinery in cell-cell communication in different stages of oogenesis.

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