FIG. 3.

Calpain activity assay. (A) Calpain activity was measured from detergent-soluble and -insoluble fractions of serum-starved SAOS-α2β1 cells after different periods of TPA (100 ng/ml) treatment. C, untreated control. (B) Calpain activity in the detergent-soluble fraction of uninfected and EV1-infected SAOS-α2β1 cells at the indicated time points p.i. (C) Calpain activity measured from EV1-infected SAOS-α2β1 cells 3 h p.i. The values are averages from four identical and separately performed experiments with detergent-soluble fractions. The error bar shows the standard error. (D) Protein levels of calpain 1 and calpain 2, detected by Western blot analysis 3 h p.i. using specific antibodies.