Studies of the Lamin Proteinase Reveal Multiple Parallel Biochemical Pathways During Apoptotic Execution

• Published in: Proceedings of the National Academy of Sciences - PNAS 1995-09, Vol.92 (20), p.9042-9046
• Main Authors: Lazebnik, Yuri A., Takahashi, Atsushi, Moir, Robert D., Goldman, Robert D., Poirier, Guy G., Kaufmann, Scott H., Earnshaw, William C.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antibodies; Apoptosis; Apoptosis - physiology; Cell free system; Cell Line; Cell nucleus; Cell Nucleus - metabolism; Cells; Cellular biology; Chromatin; Cultured cells; Endopeptidases - metabolism; Enzymes; HeLa Cells; Humans; Ice; Kinetics; Lamins; Lung Neoplasms; Molecular Sequence Data; Nuclear Proteins - biosynthesis; Nuclear Proteins - isolation & purification; Nuclear Proteins - metabolism; Poly(ADP-ribose) Polymerases - metabolism; Protease Inhibitors - pharmacology; Proteins; Recombinant Proteins - biosynthesis; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Structure-Activity Relationship; Substrate Specificity; Tumor Cells, Cultured
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.92.20.9042

Although specific proteinases play a critical role in the active phase of apoptosis, their substrates are largely unknown. We previously identified poly(ADP-ribose) polymerase (PARP) as an apoptosis-associated substrate for proteinase(s) related to interleukin 1β-converting enzyme (ICE). Now we have used a cell-free system to characterize proteinase(s) that cleave the nuclear lamins during apoptosis. Lamin cleavage during apoptosis requires the action of a second ICE-like enzyme, which exhibits kinetics of cleavage and a profile of sensitivity to specific inhibitors that is distinct from the PARP proteinase. Thus, multiple ICE-like enzymes are required for apoptotic events in these cell-free extracts. Inhibition of the lamin proteinase with tosyllysine "chloromethyl ketone" blocks nuclear apoptosis prior to the packaging of condensed chromatin into apoptotic bodies. Under these conditions, the nuclear DNA is fully cleaved to a nucleosomal ladder. Our studies reveal that the lamin proteinase and the fragmentation nuclease function in independent parallel pathways during the final stages of apoptotic execution. Neither pathway alone is sufficient for completion of nuclear apoptosis. Instead, the various activities cooperate to drive the disassembly of the nucleus.