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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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Focal adhesion in HeLa cells without vs. with EHEC infection.Representative confocal micrographs of HeLa cells (A) without- and (C) with- EHEC infection; vinculin was detected by indirect immunofluorescence. The images of focal adhesion were segmented by setting an intensity threshold via MetaMorph software to calculate the fractional area of focal adhesion, as shown in (B) for HeLa cells without-, and (D) with- EHEC infection.
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pone-0112137-g001: Focal adhesion in HeLa cells without vs. with EHEC infection.Representative confocal micrographs of HeLa cells (A) without- and (C) with- EHEC infection; vinculin was detected by indirect immunofluorescence. The images of focal adhesion were segmented by setting an intensity threshold via MetaMorph software to calculate the fractional area of focal adhesion, as shown in (B) for HeLa cells without-, and (D) with- EHEC infection.

Mentions: The effect of EHEC infection on the regulation of focal adhesions (FA) in the host cells was visualized by anti-vinculin staining. Fig. 1A shows cells without EHEC infection and Fig. 1C shows cells that had been infected for 6 hours. Analysis of the vinculin area in both cases revealed that EHEC infection induced an increase in the number of large FA (area >1 µm2), and a corresponding reduction in the number of small FA (area <0.5 µm2) (Fig. 2A). Additionally, the fraction of cell area occupied by focal adhesions (defined as the ratio of the total focal adhesion area in each cell to the total area enclosed by the boundary of each cell) increased from 0.79% to 5.14% after EHEC infection (Fig. 2B).


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)

Focal adhesion in HeLa cells without vs. with EHEC infection.Representative confocal micrographs of HeLa cells (A) without- and (C) with- EHEC infection; vinculin was detected by indirect immunofluorescence. The images of focal adhesion were segmented by setting an intensity threshold via MetaMorph software to calculate the fractional area of focal adhesion, as shown in (B) for HeLa cells without-, and (D) with- EHEC infection.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0112137-g001: Focal adhesion in HeLa cells without vs. with EHEC infection.Representative confocal micrographs of HeLa cells (A) without- and (C) with- EHEC infection; vinculin was detected by indirect immunofluorescence. The images of focal adhesion were segmented by setting an intensity threshold via MetaMorph software to calculate the fractional area of focal adhesion, as shown in (B) for HeLa cells without-, and (D) with- EHEC infection.
Mentions: The effect of EHEC infection on the regulation of focal adhesions (FA) in the host cells was visualized by anti-vinculin staining. Fig. 1A shows cells without EHEC infection and Fig. 1C shows cells that had been infected for 6 hours. Analysis of the vinculin area in both cases revealed that EHEC infection induced an increase in the number of large FA (area >1 µm2), and a corresponding reduction in the number of small FA (area <0.5 µm2) (Fig. 2A). Additionally, the fraction of cell area occupied by focal adhesions (defined as the ratio of the total focal adhesion area in each cell to the total area enclosed by the boundary of each cell) increased from 0.79% to 5.14% after EHEC infection (Fig. 2B).

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