Movie 8.

Ionomycin-induces NMII-dependent cell contraction via Ca²⁺-mediated MLCK activation. U2OS cells stimulated with 3 μM ionomycin were imaged by holographic tomography (top row). Preincubation (30 min) in Ca²⁺-free medium, 50 μM blebbistatin, or 30 μM ML7 prevents ionomycin-induced cell contractility. Likewise, NMIIA KO cells are unresponsive to ionomycin stimulation.