Related Experiment Videos
Involvement of NAD-poly(ADP-ribose) metabolism in p53 regulation and its consequences
C M Whitacre1, H Hashimoto, M L Tsai
1Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4937, USA.
Abstract:
We have used two different approaches to study the consequences of NAD/poly(ADP-ribose) deficiency on p53 expression and its activity in V79-derived cell lines. In the first approach, we have used two cell lines that are deficient in poly(ADP-ribose) (pADPR) synthesis because of deficiency in the enzyme poly(ADP-ribose) polymerase (PARP). In a second approach, we have used a cell line that is deficient in NAD/pADPR metabolism due to unavailability of NAD, the substrate for PARP. These NAD/PARP-deficient cell lines exhibit a significant reduction in both baseline p53 expression and its activity compared to their parental V79 cells. Furthermore, etoposide, a topoisomerase II inhibitor that was shown to cause an increase in p53 expression and subsequent apoptosis in V79 cells, failed to produce any significant increase in p53 expression or apoptotic DNA fragmentation in NAD/PARP-deficient cell lines. Thus, our studies suggest that NAD/pADPR synthesis may be involved in the regulation of p53 and its dependent pathways.
Insights
NAD/poly(ADP-ribose) deficiency reduces p53 expression and activity. Impaired NAD/PARP metabolism prevents etoposide-induced apoptosis, suggesting NAD/pADPR synthesis regulates p53 pathways.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- p53 is a crucial tumor suppressor protein involved in cell cycle arrest and apoptosis.
- Poly(ADP-ribose) polymerase (PARP) utilizes NAD+ to synthesize poly(ADP-ribose) (pADPR) chains, playing roles in DNA repair and cell signaling.
- NAD+ is a vital coenzyme essential for cellular metabolism and redox homeostasis.
Purpose of the Study:
- To investigate the impact of NAD/poly(ADP-ribose) metabolism deficiency on p53 expression and activity.
- To determine if NAD/PARP deficiency affects the cellular response to DNA-damaging agents like etoposide.
Main Methods:
- Utilized V79-derived cell lines with deficiencies in poly(ADP-ribose) polymerase (PARP) or NAD+ availability.
- Assessed baseline p53 expression and activity in normal versus deficient cell lines.
- Administered etoposide, a topoisomerase II inhibitor, to evaluate its effect on p53 induction and apoptosis.
Main Results:
- NAD/PARP-deficient cell lines showed significantly reduced baseline p53 expression and activity compared to parental V79 cells.
- Etoposide failed to induce significant p53 expression or apoptotic DNA fragmentation in the NAD/PARP-deficient cell lines.
- These findings indicate a critical role for NAD/pADPR synthesis in p53-mediated cellular responses.
Conclusions:
- NAD/pADPR synthesis is implicated in the regulation of p53 expression and its downstream pathways.
- Disruptions in NAD metabolism can impair the DNA damage response, affecting p53-dependent apoptosis.
- This study highlights the interconnectedness of NAD metabolism and the p53 signaling network.