Involvement of caspase-2 in the activation of ROCK-II. (A) Rho-kinase activity in response to thrombin. Rho-kinase activity was determined by a colorimetric assay of the phosphorylation of MBS substrate. HMEC-1 cells were kept untreated or were stimulated for 4 hours with 1 IU/mL thrombin. **P < .01; ***P < .001. (B) Representative immunoblot of the effects of caspase inhibitors on the release of the 130 kDa cleaved form of ROCK-II. Immunoblots were performed after a 4-hour stimulation with thrombin. Cell lysates from unstimulated or thrombin-stimulated HMEC-1 cells were resolved on 4% to 12% PAGE and the blots were probed with an anti–ROCK-II monoclonal antibody or antitubulin as a loading control. Lane 1 is unstimulated HMEC-1; lane 2, thrombin-stimulated HMEC-1; lane 3, ZVAD-FMK; lane 4, Z-VDVAD-FMK; and lane 5, Z-DVED-FMK–treated HMEC-1.