The Role of Prestress and Architecture of the Cytoskeleton and Deformability of Cytoskeletal Filaments in Mechanics of Adherent Cells: a Quantitative Analysis

Hong

Animal Cells and Systems

et al. 2013

Although cancerous cells and normal cells are known to have different elasticity values, there have been inconsistent reports in terms of the actual and relative values for these two cell types depending on the experimental conditions. This paper investigated the mechanical characterization of normal hepatocytes (THLE-2) and hepatocellular carcinoma cells (HepG2) using atomic force microscopy indentation experiments and the HertzÁSneddon model, and the results were confirmed by an independent de-adhesion assay. To improve the reliability of the data, we considered the effects of tip geometry and indentation depth on the measured elasticity of the cells. This study demonstrated that THLE-2 cells had a higher elastic modulus compared with the HepG2 cells and that this difference was more significant when a conical tip was used. The inhibitor study indicated that this difference in the mechanical properties of THLE-2 and HepG2 cells was mainly attributed to differential arrangements in the cytoskeletal networks of actin filaments. An independent de-adhesion assay also confirmed that THLE-2 cells had a higher elastic modulus compared with the HepG2 cells, which resulted in a shorter time constant for cellular contractility.

Section: Cytoskeletal Analysis Under Disruptive Conditionsmentioning

confidence: 99%

Comparative study on the differential mechanical properties of human liver cancer and normal cells

Hong

Animal Cells and Systems

et al. 2013

“…There are two members of the CSK family in mammals, CSK and CHK (CSK homologous kinase), which are related to the Src family of tyrosine kinases (SFKs) (Brown and Cooper, 1996; Thomas and Brugge, 1997;Zrihan-Licht et al, 1998;Stamenovic and Coughlin, 1999). Database searches revealed that dCSK is the only CSK homolog in the Drosophila genome.…”

Section: Identification Of Loci That Function With the Lats Tumor Supmentioning

confidence: 99%

A genetic screen for modifiers of the lats tumor suppressor gene identifies C-terminal Src kinase as a regulator of cell proliferation in Drosophila

Stewart

Huang

et al. 2003

Oncogene

Disrupting mechanisms that control cell proliferation, cell size and apoptosis can cause changes in animal and tissue size and contribute to diseases such as cancer. The LATS family of serine/threonine kinases control tissue size by regulating cell proliferation and function as tumor suppressor genes in both Drosophila and mammals. In order to understand the role of lats in size regulation, we performed a genetic modifier screen in Drosophila to identify components of the lats signaling pathway. Mutations in the Drosophila homolog of C-terminal Src kinase (dcsk) were identified as dominant modifiers of both lats gain-of-function and loss-of-function phenotypes. Homozygous dcsk mutants have enlarged tissue phenotypes similar to lats and FACS and immunohistochemistry analysis of these tissues revealed that dcsk also regulates cell proliferation during development. Animals having mutations in both dcsk and lats display cell overproliferation phenotypes more severe than either mutant alone, demonstrating these genes function together in vivo to regulate cell numbers. Furthermore, homozygous dcsk phenotypes can be partially suppressed by overexpression of lats, indicating that lats is a downstream mediator of dcsk function in vivo. Finally, we show that dCSK phosphorylates LATS in vitro at a conserved C-terminal tyrosine residue, which is critical for normal LATS function in vivo. Taken together, these results demonstrate a role for dCSK in regulating cell numbers during development by inhibiting cell proliferation and suggest that lats is one of the mediators of the dcsk phenotype.

Proc. Natl. Acad. Sci. U.S.A.

“…We previously proposed an alternative microstructural model of cell mechanics that depicts the cell as a prestressed tensegrity structure (7)(8)(9). This class of structures maintains shape stability within a continuous, tensed network of structural members by incorporating other isolated support elements that resist compression (10).…”

mentioning

confidence: 99%

“…The deformability of these structures depends on the level of prestress (preexisting tension) in the structure before application of an external load. In the simplest embodiment of the cellular tensegrity model (8,9), this stabilizing prestress is generated actively by the cell's actomyosin-based contractile apparatus and passively by distension through the cell's adhesions to extracellular matrix (ECM). The model assumes that the prestress is carried primarily by tensile microfilaments and intermediate filaments.…”

mentioning

confidence: 99%

Mechanical behavior in living cells consistent with the tensegrity model

Wang

Naruse

Stamenović

et al. 2001

Self Cite

621

538

Alternative models of cell mechanics depict the living cell as a simple mechanical continuum, porous filament gel, tensed cortical membrane, or tensegrity network that maintains a stabilizing prestress through incorporation of discrete structural elements that bear compression. Real-time microscopic analysis of cells containing GFP-labeled microtubules and associated mitochondria revealed that living cells behave like discrete structures composed of an interconnected network of actin microfilaments and microtubules when mechanical stresses are applied to cell surface integrin receptors. Quantitation of cell tractional forces and cellular prestress by using traction force microscopy confirmed that microtubules bear compression and are responsible for a significant portion of the cytoskeletal prestress that determines cell shape stability under conditions in which myosin light chain phosphorylation and intracellular calcium remained unchanged. Quantitative measurements of both static and dynamic mechanical behaviors in cells also were consistent with specific a priori predictions of the tensegrity model. These findings suggest that tensegrity represents a unified model of cell mechanics that may help to explain how mechanical behaviors emerge through collective interactions among different cytoskeletal filaments and extracellular adhesions in living cells.cytoskeleton ͉ microtubules ͉ cell mechanics ͉ myosin light chain phosphorylation ͉ mechanotransduction M echanical stress-induced alterations in cell shape and structure are critical for control of many cell functions, including growth, motility, contraction, and mechanotransduction (1). These functional alterations are mediated through changes in the internal cytoskeleton (CSK), which is composed of an interconnected network of microfilaments, microtubules, and intermediate filaments that links the nucleus to surface adhesion receptors. Advances in cell biology have resulted in better understanding of the polymerization behavior and physical properties of individual CSK filaments as well as of gels composed of combinations of filaments. Yet, the material properties measured in vitro neither explain nor predict complex mechanical behaviors that are observed in living cells (2, 3). At the same time, engineers have approached the problem of how cells stabilize their shape by developing mechanical models, without considering molecular specificity. For example, the living cell is often modeled as a continuum that contains an elastic cortex that surrounds a viscous (4) or viscoelastic (5) fluid; a more complex variation includes an elastic nucleus within a viscous cytoplasm (6). These models provide reasonable empirical fits to measured elastic moduli and viscosity in cells under specific experimental conditions (4-6), but they cannot predict from mechanistic principles how these properties alter under different challenges to the cell. Continuum models also assume that the load-bearing elements are infinitesimally small relative to the size of the cell and thus, they...