title: CrmA/SPI-2 inhibition of an endogenous ICE-related protease responsible for lamin A cleavage and apoptotic nuclear fragmentation.
abstract: CrmA, a poxvirus gene product with a serpin-like structure, blocks a variety of apoptotic death events in cultured cells. Based on the ability of CrmA to inhibit the interleukin-1beta converting enzyme in vitro, it has been speculated that interleukin-1beta converting enzyme-related proteases (caspases) essential for apoptosis are the cellular targets of CrmA. Here we found that rabbitpox virus CrmA/SPI-2 inhibits the cleavage of lamin A mediated by a caspase in our cell-free system of apoptosis. In the presence of CrmA/SPI-2, nuclear apoptosis in vitro was blocked at an intermediate stage after collapse of the chromatin against the nuclear periphery and before nuclear shrinkage and disintegration into apoptotic body-like fragments. Using N-(acetyltyrosinylvalinyl-Nepsilon-biotinyllysyl) aspartic acid [(2,6-dimethylbenzoyl)oxy] methyl ketone, which derivatizes the active forms of caspases, we could show that one of five caspases active in the extracts is inhibited both by CrmA/SPI-2 and by a peptide spanning the lamin A apoptotic cleavage site. These results reveal that CrmA/SPI-2 can inhibit a caspase responsible both for lamin A cleavage and for the nuclear disintegration characteristic of apoptosis.
authors.affiliation: Institute of Cell and Molecular Biology, University of Edinburgh, Michael Swann Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JR, Scotland, United Kingdom. bill.earnshaw@ed.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Takahashi
authors.forename: P Y
authors.initials: PY
authors.lastname: Musy
authors.forename: L M
authors.initials: LM
authors.lastname: Martins
authors.forename: G G
authors.initials: GG
authors.lastname: Poirier
authors.forename: R W
authors.initials: RW
authors.lastname: Moyer
authors.forename: W C
authors.initials: WC
authors.lastname: Earnshaw
mesh_terms: D000818:Animals; D017209:Apoptosis; D020170:Caspase 1; D002474:Cell-Free System; D002645:Chickens; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects*; D010450:Endopeptidases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011212:Poxviridae / Q000201:enzymology; D015843:Serpins / Q000494:pharmacology*; D014764:Viral Proteins / Q000494:pharmacology
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins; D015843:Serpins; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor; D011065:Poly(ADP-ribose) Polymerases; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D020170:Caspase 1; C095820:lamin proteinase