Related Experiment Videos
Liver poly(ADP-ribose)polymerase is resistant to cleavage by caspases
R A Jones1, V L Johnson, R H Hinton
1School of Biological Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
Biochemical and Biophysical Research Communications
|March 18, 1999
Summary
Hepatocyte poly(ADP-ribose)polymerase (PARP) is resistant to caspase cleavage during apoptosis. Therefore, PARP proteolysis is not a reliable marker for liver cell apoptosis.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Poly(ADP-ribose)polymerase (PARP) is a crucial DNA repair enzyme.
- PARP is typically cleaved by caspases during apoptosis in many cell types.
- Hepatocyte apoptosis involves complex cellular mechanisms that may differ from other cell types.
Purpose of the Study:
- To investigate why poly(ADP-ribose)polymerase (PARP) is not proteolytically cleaved in hepatocytes during apoptosis.
- To determine the resistance of liver PARP to caspase-mediated degradation.
- To assess the utility of PARP cleavage as a biomarker for hepatocyte apoptosis.
Main Methods:
- A cell-free system was utilized, combining isolated nuclei and cytosolic extracts.
- Nuclei and cytosolic extracts were derived from either hepatocytes or thymocytes.
- Incubation of liver PARP with cytosolic extracts from apoptotic cells and recombinant caspase-3 was performed.
Main Results:
- Hepatocyte PARP demonstrated resistance to proteolytic cleavage by caspases present in cytosolic extracts.
- Liver PARP was not degraded when incubated with cytosolic extracts from apoptotic thymocytes.
- Recombinant human caspase-3 failed to cleave liver PARP.
Conclusions:
- Hepatocyte PARP is resistant to caspase-mediated proteolysis during apoptosis.
- The observed resistance of liver PARP to cleavage is a key factor in its non-degradation.
- PARP proteolysis is not a suitable biomarker for detecting or monitoring hepatocyte apoptosis.