title: Protein kinase C inhibition induces DNA fragmentation in COLO 205 cells which is blocked by cysteine protease inhibition but not mediated through caspase-3.
abstract: Enhancing apoptosis to remove abnormal cells has potential in reversing cancerous processes. Caspase-3 activation generally accompanies apoptosis and its substrates include enzymes responsible for DNA fragmentation and isozymes of protein kinase C (PKC). Recent data, however, question its obligatory role in apoptosis. We have examined whether modulation of PKC activity induces apoptosis in COLO 205 cells and the role of caspase-3. Proliferation ([3H]thymidine) and apoptosis (DNA fragmentation and FACS) of COLO 205 cells were measured in response to PKC activation and inhibition. Caspase-3 activity was assayed and the effects of its inhibition with Ac-DEVD-cmk, and the effect of other protease inhibitors, on apoptosis were determined. PKC activation and inhibition both reduced DNA synthesis and induced DNA fragmentation. As PKC inhibitors induced DNA fragmentation more rapidly than PKC activators and failed to block activator effects, we conclude that it is PKC down-regulation (i.e., inhibition) after activator exposure that mediates apoptosis. Increases in caspase-3 activity occurred during apoptosis but apoptosis was not blocked by caspase inhibition. By contrast, the cysteine protease inhibitor, E-64d, blocked apoptosis. Cysteine proteases not of the caspase family may either act more closely to the apoptotic process than caspases or lie on an alternative, more active pathway.
authors.affiliation: Department of Medicine, Medical School, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Aurélia E
authors.initials: AE
authors.lastname: Lewis
authors.forename: Benjamin C Y
authors.initials: BC
authors.lastname: Wong
authors.forename: Michael J S
authors.initials: MJ
authors.lastname: Langman
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Eggo
mesh_terms: D000368:Aged; D000470:Alkaloids; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D007611:Aprotinin / Q000494:pharmacology; D053119:Benzophenanthridines; D001593:Benzyl Compounds / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D053938:DNA Fragmentation / Q000187:drug effects / Q000235:genetics*; D004151:Dipeptides / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D010436:Pepstatins / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000470:Alkaloids; D000590:Amino Acid Chloromethyl Ketones; D053119:Benzophenanthridines; D001593:Benzyl Compounds; C476029:Boc-D-FMK; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D006845:Hydrocarbons, Fluorinated; D007976:Leupeptins; D010436:Pepstatins; D010617:Phenanthridines; D011725:Pyridines; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C431843:tris(2-pyridylmethyl)amine; C071482:calpeptin; D004247:DNA; D007611:Aprotinin; C016299:chelerythrine; D011493:Protein Kinase C; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D007930:Leucine; C108192:aloxistatin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C031375:pepstatin