( ...)A Further Step in Understanding Apoptosis,,, Direct Detection of PARP Cleavage

Detection of early apoptotic events has become quite relevant since many studies have demonstrated that abnormalities in cell death regulation cause a variety of diseases and pathological conditions accompanied either by cell accumulation (e.g., cancer) or by cell loss (e.g., Alzheimers dementia).

One of the key initiation elements of the apoptotic pathway is the activation of caspases (cysteinyl-aspartic acid proteases) followed by cleavage of the caspase substrates [1]. The 113-kDa poly(ADP-ribose) polymerase 1 (PARP-1), which is normally involved in DNA repair, DNA stability, and other cellular events, is cleaved by members of the caspase family during early apoptosis. The zincdependent eukaryotic DNA-binding protein PARP-1 specifically recognizes DNA strand breaks produced by various genotoxic agents. Detection of a 89-kDa or 24-kDa caspase cleavage fragment of PARP-1 was shown to be a hallmark of apoptosis [2]. In contrast to measuring active caspase 3, which is degraded during apoptosis via the ubiquitin/proteosome pathway, measuring PARP-1 cleavage might allow sustained signal detection even in late stages of apoptosis.

Product Description

With the anti-PARP Caspase Cleavage Product Antibody you will specifically detect only the small apoptotic PARP-1 cleavage fragment, but not the full-length protein, in samples of human, mouse, or rat origin. The fluorescein- conjugated monoclonal antibody (clone PAR-16) enables direct detection of this early apoptosis marker.

Furthermore it provides a tool for apoptotic-pathway analysis (in situ) at the stage of caspase activity. It can be easily employed in many different applications such as flow cytometry, immunocytochemistry, and immunohistochemistry (also in conjunction with an anti-fluorescein antibody). Particularly, in regard to tissue sections, the antibody is a valuable tool in acquiring additional information on the results achieved using the TUNEL method (even in dual-labeling applications).

Typical Experiment
Flow cytometric analysis of PARP cleavage and TUNEL reactivity

HeLa cells were induced to undergo apoptosis via stimulation with anti-CD95 (clone 2R2, 0.2 g/ml) and cycloheximide (10 g/ml). After 5 hours, the untreated cells (Figure 1, left panel) and CD95-stimulated cells (Figure 1, right panel) were stained for PARP cleavage using the anti-PARP Caspase Cleavage Product-Fluorescein antibody (1 g/ml), and analyzed for TUNEL staining using the In Situ Cell Death Detection Kit, TMR red.
Cells in the two right boxes of the dot-blot analysis display PARP-1 cleavage; the upper two boxes indicate TUNEL-positive cells (Figure 1, right panel). Note that PARP cleavage precedes DNA degradation and TUNEL labeling. The staining pattern of the apoptotic small PARP fragment in HeLa cells is also shown by immunofluorescence in Figure 2a. A peptide competition control experiment is included (Figure 2b).

To gain new insights into apoptotic pathways particularly in situ Roche Applied Science now offers the anti- PARP Caspase Cleavage Product-Fluorescein antibody. The antibody can serve as an early marker of apoptosis since it is directed against the caspase cleavage site of PARP-1 and specifically recognizes an epitope that is generated by caspases, but is not accessible in nonapoptotic cells.
This easy-to-use addition to the Roche caspase-signaling product line provides a number of benefits, including

• Fast, simple detection in flow cytometry and fluorescence microscopy using a fluorescein-conjugate design

• Sensitive technique for immunohistochemistry testing with tissue sections

• Dual-labeling applications, such as combination with TUNEL

• Apoptotic-pathway analysis (in situ) at the stage of caspase activation from early to later stages

• Early apoptosis detection method in tissue sections complementing TUNEL data.

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