title: DNA-dependent protein kinase is one of a subset of autoantigens specifically cleaved early during apoptosis.
abstract: Proteolytic cleavage of key substrates appears to be an important biochemical mechanism underlying the apoptotic process, and the centrality of interleukin 1 beta-converting enzyme (ICE)-like proteases as mediators of apoptosis has been suggested. The identification of the relevant substrates of the ICE protease family during apoptosis therefore constitutes a major challenge. Using human autoantibodies, we demonstrate here that a subset of autoantigens is specifically cleaved early during apoptosis. One of these cleaved molecules is identified as the catalytic subunit of the DNA-dependent protein kinase. The time courses of all proteolytic cleavages are identical and coincide with the onset of morphologic apoptosis. Furthermore, all cleavages share the same inhibition characteristics, which implicate an ICE-like activity(ies). We propose that cleavage of these autoantigens targets these molecules for an autoimmune response by revealing immunocryptic fragments in a proimmune apoptotic setting. Study of the immunogenicity of these fragments may yield insights into the autoimmune targeting of molecules. Moreover, the autoantibodies described will be valuable tools for the elucidation of mechanistically important proteolytic steps along the apoptotic pathway.
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D001324:Autoantigens / Q000378:metabolism*; D020170:Caspase 1; D002467:Cell Nucleus / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D006367:HeLa Cells / Q000528:radiation effects; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins; D010455:Peptides / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D001324:Autoantigens; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010455:Peptides; D011065:Poly(ADP-ribose) Polymerases; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D003546:Cysteine Endopeptidases; D020170:Caspase 1