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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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Angular distribution of the direction of maximum mean squared displacement (soft direction), θMSD,max, in the apical and the basal regions of HeLa cells without vs. with EHEC infection.(A) Apical region of HeLa cells without EHEC infection (data deduced from 112 particles; (B) basal region of HeLa cells without EHEC infection (data deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (data deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (data deduced from 55 particles). Statistically significant differences (obtained from Watson's U2 test for angular distributions) were found between apical and basal regions of EHEC-infected cells (**, p<0.01), and between basal regions of non-infected and EHEC-infected cells (*, p<0.05). Variance and kurtosis of the angular distributions of θMSD,max are given in Table 2.
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pone-0112137-g007: Angular distribution of the direction of maximum mean squared displacement (soft direction), θMSD,max, in the apical and the basal regions of HeLa cells without vs. with EHEC infection.(A) Apical region of HeLa cells without EHEC infection (data deduced from 112 particles; (B) basal region of HeLa cells without EHEC infection (data deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (data deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (data deduced from 55 particles). Statistically significant differences (obtained from Watson's U2 test for angular distributions) were found between apical and basal regions of EHEC-infected cells (**, p<0.01), and between basal regions of non-infected and EHEC-infected cells (*, p<0.05). Variance and kurtosis of the angular distributions of θMSD,max are given in Table 2.

Mentions: Fig. 7 and Table 2 summarize the distribution of angular directions of maximum MSD (θMSD,max) for τ = 0.1 s. In cells without EHEC infection, the overall distribution of θMSD,max was fairly uniform, yielding high angular variances and low kurtosis coefficients, especially in the apical cell region. Similarly, the apical region of EHEC-infected cells had no significant polarization in the distribution of θMSD,max. However, the basal region of the infected cells had highly polarized rheological properties (Fig. 7C) in consistence with the well-aligned orientation of their stress fibers. The angular distribution of θMSD,max had the smallest variance and highest kurtosis in this case and these differences were statistically significant (Table 2).


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)

Angular distribution of the direction of maximum mean squared displacement (soft direction), θMSD,max, in the apical and the basal regions of HeLa cells without vs. with EHEC infection.(A) Apical region of HeLa cells without EHEC infection (data deduced from 112 particles; (B) basal region of HeLa cells without EHEC infection (data deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (data deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (data deduced from 55 particles). Statistically significant differences (obtained from Watson's U2 test for angular distributions) were found between apical and basal regions of EHEC-infected cells (**, p<0.01), and between basal regions of non-infected and EHEC-infected cells (*, p<0.05). Variance and kurtosis of the angular distributions of θMSD,max are given in Table 2.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0112137-g007: Angular distribution of the direction of maximum mean squared displacement (soft direction), θMSD,max, in the apical and the basal regions of HeLa cells without vs. with EHEC infection.(A) Apical region of HeLa cells without EHEC infection (data deduced from 112 particles; (B) basal region of HeLa cells without EHEC infection (data deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (data deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (data deduced from 55 particles). Statistically significant differences (obtained from Watson's U2 test for angular distributions) were found between apical and basal regions of EHEC-infected cells (**, p<0.01), and between basal regions of non-infected and EHEC-infected cells (*, p<0.05). Variance and kurtosis of the angular distributions of θMSD,max are given in Table 2.
Mentions: Fig. 7 and Table 2 summarize the distribution of angular directions of maximum MSD (θMSD,max) for τ = 0.1 s. In cells without EHEC infection, the overall distribution of θMSD,max was fairly uniform, yielding high angular variances and low kurtosis coefficients, especially in the apical cell region. Similarly, the apical region of EHEC-infected cells had no significant polarization in the distribution of θMSD,max. However, the basal region of the infected cells had highly polarized rheological properties (Fig. 7C) in consistence with the well-aligned orientation of their stress fibers. The angular distribution of θMSD,max had the smallest variance and highest kurtosis in this case and these differences were statistically significant (Table 2).

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