Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.62 (caspase-9)
 7,507 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously we showed that teratogen-induced cell death in mouse embryos is apoptotic in nature, i.e., involves the release of cytochrome c from mitochondria and the subsequent activation of caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), and internucleosomal DNA fragmentation. Herein we show that hyperthermia, 4-hydroperoxycyclophosphamide, and staurosporine also activate caspase-9, the apical caspase in the mitochondrial apoptotic pathway. Activation of procaspase-9 is associated with the cleavage of this proenzyme and the generation of two forms of the large subunit, primarily a 39-kDa subunit (p39) but also a lesser amount of a 37-kDa subunit (p37). We also present data that support the idea that the teratogen-induced formation of the p37 subunit in vivo occurs by the cytochrome c-mediated processing of procaspase-9, whereas the p39 subunit is formed by an amplification loop involving caspase-3. We also previously showed that the release of cytochrome c, activation of caspase-3, cleavage of PARP, and DNA fragmentation are blocked in cells of the developing heart, which are resistant to teratogen-induced cell death. We now show that this block in the mitochondrial apoptotic pathway in heart cells extends to the activation of procaspase-9. Thus, our cumulative data indicate that hyperthermia, 4-hydroperoxycyclophosphamide, and staurosporine induce cell death in Day 9 mouse embryos by activating the mitochondrial apoptotic pathway. In addition, our data suggest that cells of the Day 9 mouse embryo that are resistant to teratogen-induced cell death possess multiple mechanisms for inhibiting the mitochondrial apoptotic pathway after a teratogenic exposure.
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PMID:Teratogen-induced activation of caspase-9 and the mitochondrial apoptotic pathway in early postimplantation mouse embryos. 1205 98

The apoptosome is a multiprotein complex comprising Apaf-1, cytochrome c, and caspase-9 that functions to activate caspase-3 downstream of mitochondria in response to apoptotic signals. Binding of cytochrome c and dATP to Apaf-1 in the cytosol leads to the assembly of a heptameric complex in which each Apaf-1 subunit is bound noncovalently to a procaspase-9 subunit via their respective CARD domains. Assembly of the apoptosome results in the proteolytic cleavage of procaspase-9 at the cleavage site PEPD(315) to yield the large (p35) and small (p12) caspase-9 subunits. In addition to the PEPD site, caspase-9 contains a caspase-3 cleavage site (DQLD(330)), which when cleaved, produces a smaller p10 subunit in which the NH(2)-terminal 15 amino acids of p12, including the XIAP BIR3 binding motif, are removed. Using purified proteins in a reconstituted reaction in vitro, we have assessed the relative impact of Asp(315) and Asp(330) cleavage on caspase-9 activity within the apoptosome. In addition, we characterized the effect of caspase-3 feedback cleavage of caspase-9 on the rate of caspase-3 activation, and the potential ramifications of Asp(330) cleavage on XIAP-mediated inhibition of the apoptosome. We have found that cleavage of procaspase-9 at Asp(330) to generate p35, p10 or p37, p10 forms resulted in a significant increase (up to 8-fold) in apoptosome activity compared with p35/p12. The significance of this increase was demonstrated by the near complete loss of apoptosome-mediated caspase-3 activity when a point mutant (D330A) of procaspase-9 was substituted for wild-type procaspase-9 in the apoptosome. In addition, cleavage at Asp(330) exposed a novel p10 NH(2)-terminal peptide motif (AISS) that retained the ability to mediate XIAP inhibition of caspase-9. Thus, whereas feedback cleavage of caspase-9 by caspase-3 significantly increases the activity of the apoptosome, it does little to attenuate its sensitivity to inhibition by XIAP.
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PMID:Regulation of the Apaf-1/caspase-9 apoptosome by caspase-3 and XIAP. 1250 11

Apoptosis protease-activating factor-1 (Apaf-1), which plays a central role in the formation of the apoptosome, is absent or poorly expressed (because of a transcriptional silencing by methylation) in a substantial percentage of metastatic melanomas and melanoma cell lines, which are unable to activate caspase-9 and execute the mitochondrial pathway of apoptosis. We studied cisplatin-induced apoptosis of the Apaf-1-positive human metastatic Me665/2/21 melanoma cells. Our results indicate that caspase-7 is already processed in still-adhering cells and such activation, contrary to the common view, precedes caspase-3 processing. As expected by the cytochrome c release into the cytosol, caspase-9 is processed to active forms (p37 and p35), along with a yet-unidentified p28. Interestingly, we also demonstrate a remarkable loss of Apaf-1 protein, along with the appearance of a related immunoreactive fragment of approximate, equals 26 kDa; such proteolytic degradation proves to be a caspase-3/-7-mediated event. Our data also indicate that the inhibition afforded by ac-DEVD-CHO on several components (i.e., caspase-3/-7 and caspase-9 activities), and Apaf-1 proteolytic degradation, does not significantly abrogate either the apoptotic morphology or the cleavage of canonical targets, such as poly(ADP-ribose) polymerase (PARP) and lamin B. These results suggest that caspase-3 and caspase-7 are dispensable for the execution of apoptosis and, in our cellular model, the point of no return could be out of the mitochondrial cascade.
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PMID:Cisplatin-induced apoptosis in melanoma cells: role of caspase-3 and caspase-7 in Apaf-1 proteolytic cleavage and in execution of the degradative phases. 1503 20