Mch3, a novel human apoptotic cysteine protease highly related to CPP32
Fernandes-Alnemri, T.; Takahashi, A.; Armstrong, R.; Krebs, J.; Fritz, L.; Tomaselli, K.J.; Wang, L.; Yu, Z.; Croce, C.M.; Salveson, G.
Cancer Research 55(24): 6045-6052
1995
ISSN/ISBN: 0008-5472 PMID: 8521391 Document Number: 443006
Recent evidence suggests that mammalian cysteine proteases related to Caenorhabditis elegans CED-3 are key components of mammalian programmed cell death or apoptosis. We have shown recently that the CPP32 and Mch2-alpha cysteine proteases cleave the apoptotic markers poly(ADP-ribose) polymerase (PARP) and lamins, respectively. Here we report the cloning of a new Ced-3/interleukin 1-beta-converting enzyme-related gene, designated Mch3, that encodes a protein with the highest degree of homology to CPP32 compared to other family members. An alternatively spliced isoform, named Mch3-beta, was also identified. Bacterially expressed recombinant Mch3 has intrinsic autocatalytic/autoactivation activity. The specific activity of Mch3-alpha toward the peptide substrate DEVD-7-amino-4-methylcoumarin and PARP resembles that of CPP32. Like interleukin 1-beta-converting enzyme and CPP32, the active Mch3-alpha is made of two subunits derived from a precursor (proMch3-alpha). It was of interest that recombinant CPP32-p17 subunit can form an active heteromeric enzyme complex with recombinant Mch3-alpha-p12 subunit and vice versa, as determined by the ability of the heteromeric complexes to induce apoptosis in Sf9 cells. These data suggest that proMch3-alpha and proCPP32 can interact to form an active Mch3-alpha/CPP32 heteromeric complex. We also provide evidence that CPP32 can efficiently cleave proMch3-alpha, but not the opposite, suggesting that Mch3-alpha activation in vivo may depend in part on CPP32 activity. The high degree of conservation in structure and specific activity and the coexistence of Mch3-alpha and CPP32 in the same cell suggests that the PARP cleavage activity observed during apoptosis cannot solely be attributed to CPP32 but could also be an activity of Mch3-alpha.