What could be responsible for a consistent PARP cleavage at 89kD if not Caspase-3 activation? I have tested some of my plant fractions severally on selected cancer cell lines but have been observing the same results of PARP cleavage at 89kD but no activated Caspase-3 detection on my Western blot
Which antibody is being used? Is it specific for cleaved capase-3 fragment? You may try other apoptosis assays like Annexin V staining to detect apoptosis in the cells. Try to confirm first whether apoptosis is actually induced or not.
PARP cleavage may occur as an independent event which can be disassociated with apoptosis. Studies have also shown occurance of caspase-3 independent PARP cleavage that requires synthesis of other proteins (other caspases).
PARP is also cleaved by other caspases like caspase-1 and -7. Look for the link below to find details:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3022541/
Thanks all. I knew there are other cleavages of PARP which are Caspase-3-independent. But I was almost sure the 89kD cleavage was specific for Caspase-3. Now I know better, thanks to the link from Kumar. Also, I have had other experiments on the same extracts (The crude, actually), where we saw Spermine-dependent mitochondrial membrane permeability transition pore (MMPTP) opening suggestive of intrinsic apoptosis. So, I became confused when the cell death seen with the fractions do not seem to involve caspase-3. So, could there be spermine-dependent MMPTP opening without caspase activation????
@ Debanjan, we used the anti-Caspase 3 Rabbit Polyclonal Antibody, Thermo Scientific.
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