title: Multiple proteases are involved in thymocyte apoptosis.
abstract: To investigate the involvement of proteases in apoptosis, rat thymocytes were treated with the glucocorticoid hormone methylprednisolone or the topoisomerase II inhibitor etoposide in the presence of selective substrate inhibitors of either interleukin-1 beta-converting enzyme (ICE), (Z-Val-Ala-Asp-chloromethylketone, VADcmk) or Ca(2+)-regulated serine protease (Suc-Ala-Ala-Pro-Phe-chloromethylketone, AAPFcmk). VADcmk protected from lamin proteolysis, chromatin fragmentation, cell shrinkage, and formation of apoptotic nuclei in both methylprednisolone- and etoposide-treated thymocytes when present during the initiation of the apoptotic process. AAPFcmk prevented lamin breakdown, chromatin fragmentation, and apoptotic morphological changes in thymocytes treated with methylprednisolone, but not with etoposide. Both MPS- and etoposide-treated thymocytes exhibited enhanced ICE-like protease activity which was maximal 1 h after treatment. This increase in proteolytic activity was blocked by VADcmk, but not AAPFcmk. Our findings suggest that ICE-like protease activity is critically involved in the early phase of both methylprednisolone- and etoposide-induced apoptosis in thymocytes, whereas the Ca(2+)-regulated serine protease is an obligatory component of the proteolytic cascade in methylprednisolone-induced apoptosis.
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000502:physiology; D020170:Caspase 1; D048429:Cell Size; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D034882:Lamins; D008297:Male; D008775:Methylprednisolone / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000502:physiology*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology*; D059005:Topoisomerase II Inhibitors
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D002843:Chromatin; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D034882:Lamins; D009687:Nuclear Proteins; D009842:Oligopeptides; D015842:Serine Proteinase Inhibitors; D059005:Topoisomerase II Inhibitors; C083541:succinyl-alanylalanyl-prolyl-phenylalanine chloromethylketone; D005047:Etoposide; D004247:DNA; D012697:Serine Endopeptidases; D003546:Cysteine Endopeptidases; D020170:Caspase 1; D002118:Calcium; D008775:Methylprednisolone