Figure 2.
Subcellular cytoskeleton (CSK) tension and focal adhesion (FA) followed distinct mechanosensitive rheostasis to drive single-cell mechanical homeostasis. (a&b) Heterogeneous rheostatic paths for subcellular CSK tension (a) and FA (b). Results from REF-52 fibroblasts under 8% static equibiaxial stretch were grouped into subsets based on ground-state CSK tension values at t = 0 min (F0). Average result from each subset was plotted using the rainbow spectrum (from purple to red). Whole-cell average response (black) was included for referencing single-cell homeostasis. Data represents the mean ± s.e.m with n = 10. (c-f) Dependence of subcellular rheostasis on ground-state values of CSK tension and FA size. Changes in CSK tension (c&d) and FA size (e&f) during Phase I (t = 0 - 1 min; c&e) and phase II (t = 1 - 30 min; d&f) were color-coded in two-dimensional ground-state CSK tension - FA size diagrams obtained at t = 0 min. Red dashed lines in d and f marked average ground-state values of CSK tension and FA size as well as a transition boundary between reinforcement and relaxation for subcellular rheostasis during Phase II. (g-j) Responses of subcellular CSK tension (top) and FA (bottom) rheostasis to pharmacological inhibitors in REF-52 fibroblasts under 8% static equibiaxial stretch (g: nocodazole; h: blebbistatin; i: jasplakinolide; j: cytochalasin D). Results were grouped into subsets based on ground-state CSK tension values at t = 0 min (F0). Whole-cell average responses (black) were included to indicate changes in single-cell homeostasis. Data represents the mean ± s.e.m with n = 10. (k) Force - lifetime diagram of the catch-slip bond between α5β1 integrin and FNIII7-10, with or without treatments of antibody TS2/16 as indicated (from Ref. [23]). (l) Response of subcellular CSK tension (left) and FA (right) rheostasis to TS2/16 treatment in human mesenchymal stem cells (HUMSCs) under 8% static equibiaxial stretch. Results were grouped into subsets based on ground-state CSK tension values at t = 0 min (F0). Whole-cell average response (black) was included to indicate changes in single-cell homeostasis. Data represents the mean ± s.e.m with n = 11. In g-i and l, hollow red arrowheads indicated suppressed FA reinforcement in Phase I, and solid red arrowheads marked suppressed FA relaxation in Phase II. P-values were calculated using student’s paired sample t-test comparing data before (t = 0 min) and after (t = 1 or 30 min) stretch. N.S., statistically not significant and P > 0.05. *, P < 0.05. Statistical analysis for different FA subsets was color-coded as indicated.