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The effect of enterohemorrhagic E. coli infection on the cell mechanics of host cells.

Chen YQ, Su PT, Chen YH, Wei MT, Huang CH, Osterday K, del Álamo JC, Syu WJ, Chiou A - PLoS ONE (2014)

Bottom Line: When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells.Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned.These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China.

ABSTRACT
Enterohaemorrhagic E. coli (EHEC) is a type of human pathogenic bacteria. The main virulence characteristics of EHEC include the formation of attaching and effacing lesions (A/E lesions) and the production of one or more Shiga-like toxins, which may induce human uremic complications. When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells. To examine the effect of EHEC infection on cell mechanics, we carried out a series of experiments to examine HeLa cells with and without EHEC infection to quantify the changes in (1) focal adhesion area, visualized by anti-vinculin staining; (2) the distribution and orientation of stress fibers; and (3) the intracellular viscoelasticity, via directional video particle tracking microrheology. Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned. The cytoskeletal reorganization induced by EHEC infection mediated a dramatic increase in the cytoplasmic elastic shear modulus of the infected cells, and a transition in the viscoelastic behavior of the cells from viscous-like to elastic-like. These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.

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The principal value of the mean squared displacement (PMSD) as a function of the time lag (τ).In each diagram, the upper curve represents the result for the soft axis, and the lower curve for the stiff axis. (A) Apical region (deduced from 112 particles) of HeLa cells without EHEC infection; (B) basal region of HeLa cells without EHEC infection (deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (deduced from 55 particles). The straight lines represent the power law dependence; the symbols represent the mean value of the experimental results. The vertical bars around each point represent the corresponding standard deviation.
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pone-0112137-g006: The principal value of the mean squared displacement (PMSD) as a function of the time lag (τ).In each diagram, the upper curve represents the result for the soft axis, and the lower curve for the stiff axis. (A) Apical region (deduced from 112 particles) of HeLa cells without EHEC infection; (B) basal region of HeLa cells without EHEC infection (deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (deduced from 55 particles). The straight lines represent the power law dependence; the symbols represent the mean value of the experimental results. The vertical bars around each point represent the corresponding standard deviation.

Mentions: To demonstrate that EHEC infection of HeLa cells led to stress-fiber alignment, we compiled angular distributions of stress fibers for 15 cells with and without infection (Fig. 5D and Fig. 5H, respectively). Statistical analysis of stress-fiber orientation revealed that the variance of the angular distribution decreased and its kurtosis increased with EHEC infection (see Table 1). These differences were found to be statistically significant (p<0.001, Watson's U2 test). Because the variance and kurtosis of a distribution respectively quantify its spread and peakedness, this analysis confirms that the orientation of the F-actin cytoskeleton became tightly aligned along a common direction after EHEC infection. These observed directional changes in the cell cytoskeleton suggest that EHEC infection may induce anisotropy in intracellular rheology, meaning that the viscoelastic properties of the infected cells could be different when measured along different directions. This led to a subsequent study, via DVPTM, of the viscoelastic properties of HeLa cells with vs. without EHEC infection.


The effect of enterohemorrhagic E. coli infection on the cell mechanics of host cells.

Chen YQ, Su PT, Chen YH, Wei MT, Huang CH, Osterday K, del Álamo JC, Syu WJ, Chiou A - PLoS ONE (2014)

The principal value of the mean squared displacement (PMSD) as a function of the time lag (τ).In each diagram, the upper curve represents the result for the soft axis, and the lower curve for the stiff axis. (A) Apical region (deduced from 112 particles) of HeLa cells without EHEC infection; (B) basal region of HeLa cells without EHEC infection (deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (deduced from 55 particles). The straight lines represent the power law dependence; the symbols represent the mean value of the experimental results. The vertical bars around each point represent the corresponding standard deviation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219835&req=5

pone-0112137-g006: The principal value of the mean squared displacement (PMSD) as a function of the time lag (τ).In each diagram, the upper curve represents the result for the soft axis, and the lower curve for the stiff axis. (A) Apical region (deduced from 112 particles) of HeLa cells without EHEC infection; (B) basal region of HeLa cells without EHEC infection (deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (deduced from 55 particles). The straight lines represent the power law dependence; the symbols represent the mean value of the experimental results. The vertical bars around each point represent the corresponding standard deviation.
Mentions: To demonstrate that EHEC infection of HeLa cells led to stress-fiber alignment, we compiled angular distributions of stress fibers for 15 cells with and without infection (Fig. 5D and Fig. 5H, respectively). Statistical analysis of stress-fiber orientation revealed that the variance of the angular distribution decreased and its kurtosis increased with EHEC infection (see Table 1). These differences were found to be statistically significant (p<0.001, Watson's U2 test). Because the variance and kurtosis of a distribution respectively quantify its spread and peakedness, this analysis confirms that the orientation of the F-actin cytoskeleton became tightly aligned along a common direction after EHEC infection. These observed directional changes in the cell cytoskeleton suggest that EHEC infection may induce anisotropy in intracellular rheology, meaning that the viscoelastic properties of the infected cells could be different when measured along different directions. This led to a subsequent study, via DVPTM, of the viscoelastic properties of HeLa cells with vs. without EHEC infection.

Bottom Line: When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells.Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned.These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China.

ABSTRACT
Enterohaemorrhagic E. coli (EHEC) is a type of human pathogenic bacteria. The main virulence characteristics of EHEC include the formation of attaching and effacing lesions (A/E lesions) and the production of one or more Shiga-like toxins, which may induce human uremic complications. When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells. To examine the effect of EHEC infection on cell mechanics, we carried out a series of experiments to examine HeLa cells with and without EHEC infection to quantify the changes in (1) focal adhesion area, visualized by anti-vinculin staining; (2) the distribution and orientation of stress fibers; and (3) the intracellular viscoelasticity, via directional video particle tracking microrheology. Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned. The cytoskeletal reorganization induced by EHEC infection mediated a dramatic increase in the cytoplasmic elastic shear modulus of the infected cells, and a transition in the viscoelastic behavior of the cells from viscous-like to elastic-like. These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.

Show MeSH
Related in: MedlinePlus