Quantifying the contribution of actin networks to the elastic strength of fibroblasts

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• 作者：Revathi Ananthakrishnan ; Jochen Guck ; Falk Wottawah ; Stefan Schinkinger ; Bryan Lincoln ; Maren Romeyke ; Tess Moon and Josef Kä ; s
• 刊名：Journal of Theoretical Biology
• 出版年：2006
• 期刊代码：79_00225193
• 类别：mt
• 出版时间：21 September 2006
• 卷：242
• 期：2
• 页码：502-516
• 文件大小：592 K

摘要

The structural models created to understand the cytoskeletal mechanics of cells in suspension are described here. Suspended cells can be deformed by well-defined surface stresses in an Optical Stretcher [Guck, J., Ananthakrishnan, R., Mahmood, H., Moon, T.J., Cunningham, C.C., Käs, J., 2001. The optical stretcher: a novel laser tool to micromanipulate cells. Biophys. J. 81(2), 767–784], a two-beam optical trap designed for the contact-free deformation of cells. Suspended cells have a well-defined cytoskeleton, displaying a radially symmetric actin cortical network underlying the cell membrane with no actin stress fibers, and microtubules and intermediate filaments in the interior. Based on experimental data using suspended fibroblasts, we create two structural models: a thick shell actin cortex model that describes cell deformation for a localized stress distribution on these cells and a three-layered model that considers the entire cytoskeleton when a broad stress distribution is applied.

Applying the models to data, we obtain a (actin) cortical shear moduli G of 220 Pa for normal fibroblasts and 185 Pa for malignantly transformed fibroblasts. Additionally, modeling the cortex as a transiently crosslinked isotropic actin network, we show that actin and its crosslinkers must be co-localized into a tight shell to achieve these cortical strengths. The similar moduli values and cortical actin and crosslinker densities but different deformabilities of the normal and cancerous cells suggest that a cell's structural strength is not solely determined by cytoskeletal composition but equally importantly by (actin) cytoskeletal architecture via differing cortical thicknesses. We also find that although the interior structural elements (microtubules, nucleus) contribute to the deformed cell's exact shape via their loose coupling to the cortex, it is the outer actin cortical shell (and its thickness) that mainly determines the cell's structural response.