Cell mechanics and the cytoskeleton
TL;DR: An important insight emerging from this work is that long-lived cytoskeletal structures may act as epigenetic determinants of cell shape, function and fate.
Abstract: The ability of a eukaryotic cell to resist deformation, to transport intracellular cargo and to change shape during movement depends on the cytoskeleton, an interconnected network of filamentous polymers and regulatory proteins. Recent work has demonstrated that both internal and external physical forces can act through the cytoskeleton to affect local mechanical properties and cellular behaviour. Attention is now focused on how cytoskeletal networks generate, transmit and respond to mechanical signals over both short and long timescales. An important insight emerging from this work is that long-lived cytoskeletal structures may act as epigenetic determinants of cell shape, function and fate.
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TL;DR: The specific features of supramolecular polymers that can lead to applications in a variety of fields are reviewed, including: materials—in which processability and self-healing properties are of interest; biomedicine— in which the concerns are dynamic functionality and biodegradability; and hierarchical assembly and electronic systems—with an interest in unidirectionality of charge flow.
Abstract: Supramolecular polymers can be random and entangled coils with the mechanical properties of plastics and elastomers, but with great capacity for processability, recycling, and self-healing due to their reversible monomer-to-polymer transitions. At the other extreme, supramolecular polymers can be formed by self-assembly among designed subunits to yield shape-persistent and highly ordered filaments. The use of strong and directional interactions among molecular subunits can achieve not only rich dynamic behavior but also high degrees of internal order that are not known in ordinary polymers. They can resemble, for example, the ordered and dynamic one-dimensional supramolecular assemblies of the cell cytoskeleton and possess useful biological and electronic functions.
2,777 citations
TL;DR: The ability to form the amyloid state is more general than previously imagined, and its study can provide unique insights into the nature of the functional forms of peptides and proteins, as well as understanding the means by which protein homeostasis can be maintained and protein metastasis avoided.
Abstract: The phenomenon of protein aggregation and amyloid formation has become the subject of rapidly increasing research activities across a wide range of scientific disciplines. Such activities have been stimulated by the association of amyloid deposition with a range of debilitating medical disorders, from Alzheimer's disease to type II diabetes, many of which are major threats to human health and welfare in the modern world. It has become clear, however, that the ability to form the amyloid state is more general than previously imagined, and that its study can provide unique insights into the nature of the functional forms of peptides and proteins, as well as understanding the means by which protein homeostasis can be maintained and protein metastasis avoided.
1,758 citations
TL;DR: This review focuses on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators.
Abstract: In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping ...
1,395 citations
TL;DR: The feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro is described and this knowledge is integrated into the current understanding of cellular actin organizations and its physiological roles.
Abstract: Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or "dashpots" (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.
1,128 citations
Cites background from "Cell mechanics and the cytoskeleton..."
...studies concerning the mechanical properties and force generation of branched networks, no clear consensus has emerged relating the detailed actin structure to how good the actin network is at moving an object (3, 4, 20, 87, 195, 257, 338)....
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...Crosslinked networks are involved in controlling cell shape and mechanical integrity (64, 87, 98, 156, 254, 331)....
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...There are still mysteries to be solved in the relationship between actin dynamics and force production (6, 87, 208)....
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...So a detailed understanding of the actin architecture is necessary to understand the relationship between actin organization and mechanical response (87, 178, 299)....
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TL;DR: The spacing between polypeptide chains along the fibril axis is constant to a good approximation even for very different polypeptic sequences, a generic property arising from the common inter-side chain hydrogen bonding constraints.
Abstract: Nature Reviews Molecular Cell Biology 15, 384–396 (2014) In the legend of figure 2 of the above article (page 388), the sentence “The spacing between polypeptide chains along the fibril axis is constant to a good approximation even for very different polypeptide sequences, a generic property arisingfrom the common inter-side chain hydrogen bonding constraints (orange line in part b).
739 citations
References
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TL;DR: Naive mesenchymal stem cells are shown here to specify lineage and commit to phenotypes with extreme sensitivity to tissue-level elasticity, consistent with the elasticity-insensitive commitment of differentiated cell types.
12,204 citations
TL;DR: An understanding of how tissue cells—including fibroblasts, myocytes, neurons, and other cell types—sense matrix stiffness is just emerging with quantitative studies of cells adhering to gels with which elasticity can be tuned to approximate that of tissues.
Abstract: Normal tissue cells are generally not viable when suspended in a fluid and are therefore said to be anchorage dependent. Such cells must adhere to a solid, but a solid can be as rigid as glass or softer than a baby's skin. The behavior of some cells on soft materials is characteristic of important phenotypes; for example, cell growth on soft agar gels is used to identify cancer cells. However, an understanding of how tissue cells-including fibroblasts, myocytes, neurons, and other cell types-sense matrix stiffness is just emerging with quantitative studies of cells adhering to gels (or to other cells) with which elasticity can be tuned to approximate that of tissues. Key roles in molecular pathways are played by adhesion complexes and the actinmyosin cytoskeleton, whose contractile forces are transmitted through transcellular structures. The feedback of local matrix stiffness on cell state likely has important implications for development, differentiation, disease, and regeneration.
5,889 citations
"Cell mechanics and the cytoskeleton..." refers background in this paper
...More recent studies have shown that the tension generated by a contracting cytoskeleton can be used to sense the mechanical properties of the extracellular matrix, which in turn have been shown to affect cytoskeletal organization and cell behaviou...
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TL;DR: Highly dynamic mitotic-spindle microtubules are among the most successful targets for anticancer therapy, and it is now known that at lower concentrations, microtubule-targeted drugs can suppress micro Tubule dynamics without changingmicrotubule mass; this action leads to mitotic block and apoptosis.
Abstract: Highly dynamic mitotic-spindle microtubules are among the most successful targets for anticancer therapy. Microtubule-targeted drugs, including paclitaxel and Vinca alkaloids, were previously considered to work primarily by increasing or decreasing the cellular microtubule mass. Although these effects might have a role in their chemotherapeutic actions, we now know that at lower concentrations, microtubule-targeted drugs can suppress microtubule dynamics without changing microtubule mass; this action leads to mitotic block and apoptosis. In addition to the expanding array of chemically diverse antimitotic agents, some microtubule-targeted drugs can act as vascular-targeting agents, rapidly depolymerizing microtubules of newly formed vasculature to shut down the blood supply to tumours.
4,007 citations
"Cell mechanics and the cytoskeleton..." refers background in this paper
...The ability of the mitotic spindle to find and align chromosomes depends, in part, on the complex assembly dynamics of individual microtubule...
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TL;DR: A core set of proteins including actin, Arp2/3 complex, profilin, capping protein, and ADF/cofilin can reconstitute the process in vitro, and mathematical models of the constituent reactions predict the rate of motion.
3,793 citations
TL;DR: It is found that tumors are rigid because they have a stiff stroma and elevated Rho-dependent cytoskeletal tension that drives focal adhesions, disrupts adherens junctions, perturbs tissue polarity, enhances growth, and hinders lumen formation.
3,553 citations
"Cell mechanics and the cytoskeleton..." refers background in this paper
...In epithelial cell layers, altered stiffness of the supporting tissue disrupts morphogenesis and drives the epithelial cells towards a malignant phenotyp...
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