title: Generation of constitutively active recombinant caspases-3 and -6 by rearrangement of their subunits.
abstract: Caspases play a major role in the transduction of the apoptotic signal and execution of apoptosis in mammalian cells. Ectopic overexpression of the short prodomain caspases-3 and -6 precursors in mammalian cells does not induce apoptosis. This is due to their inability to undergo autocatalytic processing/activation and suggests that they depend on the long prodomain caspases for activation. To investigate directly the apoptotic activity of these two caspases in vivo, we engineered constitutively active recombinant caspases-3 and -6 precursors. This was achieved by making contiguous precursor caspases-3 and -6 molecules, which have their small subunits preceding their large subunits. Unlike their wild type counterparts, these recombinant molecules were capable of autocatalytic processing in an in vitro translation reaction, suggesting that they are catalytically active. They were also capable of autoprocessing and inducing apoptosis in vivo independent of the upstream caspases. Furthermore, their autocatalytic and apoptotic activities were inhibited by the pancaspase inhibitor z-VAD-fluoromethylketone, but not by CrmA or Bcl-2, thus directly demonstrating that the targets of inhibition of apoptosis by CrmA and Bcl-2 are upstream of caspases-3 and -6. Since caspases-3 and -6 are the most downstream executioners of apoptosis, the constitutively active versions of these caspases could be used at very low concentrations in gene therapy model systems to induce apoptosis in target tissues or tumors.
authors.affiliation: Center for Apoptosis Research and the Department of Microbiology and Immunology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Srinivasula
authors.forename: M
authors.initials: M
authors.lastname: Ahmad
authors.forename: M
authors.initials: M
authors.lastname: MacFarlane
authors.forename: Z
authors.initials: Z
authors.lastname: Luo
authors.forename: Z
authors.initials: Z
authors.lastname: Huang
authors.forename: T
authors.initials: T
authors.lastname: Fernandes-Alnemri
authors.forename: E S
authors.initials: ES
authors.lastname: Alnemri
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases; D002384:Catalysis; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D034882:Lamins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D004792:Enzyme Precursors; D034882:Lamins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505514:CASP6 protein, human; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases; D003546:Cysteine Endopeptidases