The M30 antibody specifically labels apoptotic epithelial cells and does not label viable or necrotic cells (Leers et al. colocalized with active endogenous caspase-3. We propose that effector caspase-mediated cleavage of cytokeratins, resulting in disassembly of the cytoskeleton and formation of cytoplasmic inclusions, may be a characteristic feature of epithelial cell apoptosis. (Wang et Darusentan al. 1996; Li et al. 1998; Luo et al. 1998). In the presence of cytochrome for 3 min Darusentan at 4C to collect any apoptotic cells that experienced become detached from your plate. The remaining attached cells were collected by trypsinization and the detached and adherent cells were pooled, spun down, washed in ice-cold PBS, and resuspended in 5 ml ice-cold PBS. The cells were sorted on a FACS? Vantage (Becton Dickinson), and populations of cells exhibiting low or high intensity green fluorescence were collected for analysis by Western blotting. Gel Electrophoresis and Immunoblotting Equal numbers of cells were lysed in SDS-PAGE buffer and separated on Darusentan 10% (GFP, K8, and K19) or 12% (caspases, Bid, and K18) SDS-polyacrylamide gels, followed by electrophoretic transfer onto nitrocellulose (Hybond-C extra; Amersham) as previously explained (MacFarlane et al. 1997b). Equivalent protein loading per lane was verified by staining the membranes with 0.1% Ponceau S. Immunodetection was carried out using the enhanced chemiluminescence detection system (Amersham) according to the manufacturer’s instructions. Main Antibodies Antibodies to caspase-3 (from Dr. D. Nicholson, Merck Frosst, Quebec, Canada), caspases-7, -8, and -9 (provided by Dr. D. Green, Institute for Allergy and Immunology, La Jolla, CA), and Bid (from Dr. X. Wang, University or college of Texas Southwestern Medical Center, Dallas, TX) were used for Western blot analysis, as previously explained (Sun et al. 1999). The rabbit polyclonal antibody CM1, specific for the p18 subunit of triggered caspase-3 SULF1 (Srinivasan et al. 1998; provided by IDUN, La Jolla, CA), was used at a 1:2,500 dilution for fluorescence immunocytochemistry. The rabbit polyclonal antibody to GFP was from CLONTECH Laboratories, Inc., and used at a 1:2,000 dilution for immunoblotting. The mouse mAb M20, specific for K8, and A53-B/A2, specific for K19, were both used at a 1:10,000 dilution for Western blotting, at 1:250 for fluorescence immunocytochemistry and at 1:5C1:100 for ultrastructural immunocytochemistry. The 3055 rabbit polyclonal antibody, specific for K18 phosphorylated on serine 53 (Liao et al. 1995; provided by Dr. B. Omary, Stanford University or college School of Medicine, Stanford, CA), was used at 1:10,000 for immunoblotting, at 1:250 for fluorescence immunocytochemistry, and at 1:100 for ultrastructural immunocytochemistry. The CY-90 mouse mAb, specific for K18, was used at a 1:20,000 dilution for immunoblotting, 1:500 for fluorescence immunocytochemistry, and 1:200 for ultrastructural immunocytochemistry. The mouse mAb, M30 (Boehringer Mannheim), which specifically detects a caspase cleavage site in K18 at DALD397S (Leers et al. 1999), was used at 1:200 for fluorescence immunocytochemistry and at 1:100 for ultrastructural immunocytochemistry. The M30 antibody specifically labels apoptotic epithelial cells and does not label viable or necrotic cells (Leers et al. 1999). The calnexin antibody, clone calnexin-CT (Stressgen Biotechnology Corp.), was used at a dilution of 1 1:100 for fluorescence immunocytochemistry. The mAbs, clone 6-11B-1, to acetylated tubulin, clone AC15, specific for -actin and clone Vim3B4, to vimentin (Boehringer Mannheim) were also used. Immunofluorescence Microscopy Cells were cultivated on coverslips and, where indicated, MCF-7 cells were transfected as explained. Before nuclear staining, the cells were washed three times with PBS and fixed in 4% paraformaldehyde for 10 min at space temperature. Coverslips were rinsed three times with PBS and stained for 10 min with 0.5 g/.