Figure 4.

Pressure-induced microtubule depolymerization. (A) Sequential fluorescence images of same microtubule recorded at 2-min intervals. A pressure of 150 MPa was applied to a polarity-marked microtubule in the presence of 10 μM paclitaxel and 100 μM AMP-PNP. Scale bar, 5 μm. (B) Time courses of length changes from plus and minus ends of same microtubules. Pressure of 125 MPa (solid circles) or 150 MPa (open circles) was applied from t = 0 min. Plots at plus and minus ends were fitted by straight lines of 0.34 and 0.32 μm min⁻¹ at 125 MPa, respectively. Similarly, plots at plus and minus ends were fitted by straight lines of 1.0 and 1.1 μm min⁻¹ at 150 MPa, respectively. (C) Pressure dependence of shortening rates at plus (open squares) and minus (solid circles) ends (mean ± SD, n = 26–45). Shortening rates were fitted by Eq. (1), with α_shortening = 1.9 × 10⁻³μm min⁻¹ and ΔV^‡_shortening = −170 ų. (D) Pressure dependence of breakage rate of microtubules (mean ± SD, observed severing events; n = 3–8, total = 39). Breakage rates were fitted by Eq. (1), with α_breakage = 5.3 × 10⁻⁶μm⁻¹ min⁻¹ and ΔV^‡_breakage = −170 ų. (Inset) Sequential images of same microtubule at 125 MPa, recorded at 3-min intervals. Scale bar, 5 μm.