title: Processing/activation of at least four interleukin-1beta converting enzyme-like proteases occurs during the execution phase of apoptosis in human monocytic tumor cells.
abstract: Identification of the processing/activation of multiple interleukin-1beta converting enzyme (ICE)-like proteases and their target substrates in the intact cell is critical to our understanding of the apoptotic process. In this study we demonstrate processing/activation of at least four ICE-like proteases during the execution phase of apoptosis in human monocytic tumor THP.1 cells. Apoptosis was accompanied by processing of Ich-1, CPP32, and Mch3alpha to their catalytically active subunits, and lysates from these cells displayed a proteolytic activity with kinetics, characteristic of CPP32/Mch3alpha but not of ICE. Fluorescence-activated cell sorting was used to obtain pure populations of normal and apoptotic cells. In apoptotic cells, extensive cleavage of Ich-1, CPP32, and Mch3alpha. was observed together with proteolysis of the ICE-like protease substrates, poly (ADP-ribose) polymerase (PARP), the 70-kD protein component of U1 small nuclear ribonucleoprotein (U1-70K), and lamins A/B. In contrast, no cleavage of CPP32, Mch3alpha or the substrates was observed in normal cells. In cells exposed to an apoptotic stimulus, some processing of Ich-1 was detected in morphologically normal cells, suggesting that cleavage of Ich-1 may occur early in the apoptotic process. The ICE-like protease inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone (Z-VAD.FMK), inhibited apoptosis and cleavage of Ich-1, CPP32, Mch3alpha, Mch2alpha, PARP, U1-70K, and lamins. These results suggest that Z-VAD.FMK inhibits apoptosis by inhibiting a key effector protease upstream of Ich-1, CPP32, Mch3alpha, and Mch2alpha. Together these observations demonstrate that processing/activation of Ich-1, CPP32, Mch3alpha, and Mch2alpha accompanies the execution phase of apoptosis in THP.1 cells. This is the first demonstration of the activation of at least four ICE-like proteases in apoptotic cells, providing further evidence for a requirement for the activation of multiple ICE-like proteases during apoptosis.
authors.affiliation: Centre for Mechanisms of Human Toxicity, University of Leicester, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: MacFarlane
authors.forename: K
authors.initials: K
authors.lastname: Cain
authors.forename: X M
authors.initials: XM
authors.lastname: Sun
authors.forename: E S
authors.initials: ES
authors.lastname: Alnemri
authors.forename: G M
authors.initials: GM
authors.lastname: Cohen
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D020170:Caspase 1; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D034882:Lamins; D009000:Monocytes / Q000166:cytology* / Q000201:enzymology; D009687:Nuclear Proteins / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D015853:Cysteine Proteinase Inhibitors; D034882:Lamins; D009687:Nuclear Proteins; D011498:Protein Precursors; D017412:Ribonucleoprotein, U1 Small Nuclear; C490688:SNRNP70 protein, human; D011065:Poly(ADP-ribose) Polymerases; D003546:Cysteine Endopeptidases; D020170:Caspase 1