Icad apoptosis Activator#

However, caspases and CAD are not the only effectors causing nuclear apoptosis. Similarly, the inactivation of CAD prevents advanced chromatin condensation in different cell types 9.

Icad apoptosis Activator#

Accordingly, the inactivation of the caspase-3 gene 6, 7 and that of the caspase activator Apaf-1 8 can delay cell death and largely abolish the type of chromatin condensation observed in normal control cells treated with apoptosis inducers such as staurosporine (STS) or etoposide. It has been generally assumed that caspases as well as downstream effectors such as caspase-activated DNase (CAD) and Acinus are rate limiting for the development of nuclear apoptosis 1, 2, 3, 4, 5. One of the hallmarks of apoptosis is the degradation and concomitant compaction of chromatin. The other pathway, which is caspase-independent, involves AIF and leads to large-scale DNA fragmentation and peripheral chromatin condensation. One of these pathways involves Apaf-1 and caspases, as well as CAD, and leads to oligonucleosomal DNA fragmentation and advanced chromatin condensation. As a result, at least two redundant parallel pathways may lead to chromatin processing during apoptosis. In contrast, AIF depletion alone suffices to suppress the nuclear DNA loss contained in extracts from apoptotic Apaf-1 РІв‚¬вЂ™/РІв‚¬вЂ™ or caspase-3 РІв‚¬вЂ™/РІв‚¬вЂ™ cells. Furthermore, in a cell-free system, concomitant neutralization of AIF and CAD is required to suppress the nuclear DNA loss caused by cytoplasmic extracts from apoptotic wild-type cells. Similarly, when added to purified HeLa nuclei, AIF causes stage I chromatin condensation and large-scale DNA fragmentation, whereas CAD induces stage II chromatin condensation and oligonucleosomal DNA degradation.

Microinjection of such cells with recombinant AIF only causes peripheral chromatin condensation (stage I), whereas microinjection with activated caspase-3 or its downstream target caspase-activated DNAse (CAD) causes a more pronounced type of chromatin condensation (stage II). However, when compared with normal control cells, Apaf-1 РІв‚¬вЂ™/РІв‚¬вЂ™ or caspase-3 РІв‚¬вЂ™/РІв‚¬вЂ™ cells fail to exhibit oligonucleosomal chromatin digestion and a more advanced pattern of chromatin condensation (stage II). Apaf-1 РІв‚¬вЂ™/РІв‚¬вЂ™ or caspase-3 РІв‚¬вЂ™/РІв‚¬вЂ™ cells treated with a variety of apoptosis inducers manifest apoptosis-associated alterations including the translocation of apoptosis-inducing factor (AIF) from mitochondria to nuclei, large scale DNA fragmentation, and initial chromatin condensation (stage I).