| Summary: | 碩士 === 國立陽明大學 === 生醫光電研究所 === 100 === EHEC (Enterohaemorrhagic E. coli) colonizes the large intestinal epithelial cells and induces attaching and effacing (A/E) lesions, which are characterized by the destruction of intestinal microvilli and the formation of polymerized actin structure (known as pedestal) beneath the bacterium. EHEC injects effector proteins into host cells and then manipulates the cellular mechanism to infect host cells. For instance, one of the injected effectors, Tir, localizes on the host cell membrane and provides a binding site for the bacterial outer membrane protein, intimin. The Tir-Intimin interaction triggers actin polymerization, which may affect cellular viscoelasticity and morphology, in addition to other biochemical and physiological properties of the cells.
To examine the effect of Tir on cellular viscoelasticity, Tir was expressed in HeLa (pEYFP-Actin) cells by transient transfection to induce polymerization, rearrangement, and accumulation of actin molecules, and the intra-cellular viscoelastic properties (i.e., the elastic modulus and the viscous modulus) were measured via video particle-tracking microrheology and compared with the corresponding values of HeLa (pEYFP-Actin) cells without Tir-transfection.
Our results reveal that the intracellular viscoelastic moduli in the regions close to bundle-like actin of Tir-tranfected HeLa cells are significantly higher than the corresponding values in the regions of less actins, and also significantly higher than those in HeLa cells without Tir transfection. On the average, the intracellular viscoelastic moduli of Tir-tranfected HeLa cells are much higher than the corresponding values in normal cells (without Tri-transfection). In summary, our results indicate that actin polymerization and actin-bundle formation induced by Tir-transfection into HeLa cells not only cause highly non-uniform intracellular viscoelasticity, but also increase the over-all average intracellular viscoelasticity compared with the cells without Tir-transfection.
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