PKCα and HMGB1 antagonistically control hydrogen peroxide-induced poly-ADP-ribose formation

Harmful oxidation of proteins, lipids and nucleic acids is observed when reactive oxygen species (ROS) are produced excessively and/or the antioxidant capacity is reduced, causing 'oxidative stress'. Nuclear poly-ADP-ribose (PAR) formation is thought to be induced in response to oxidative DNA damage and to promote cell death under sustained oxidative stress conditions. However, what exactly triggers PAR induction in response to oxidative stress is incompletely understood. Using reverse phase protein array (RPPA) and in-depth analysis of key stress signaling components, we observed that PAR formation induced by H2O2 was mediated by the PLC/IP3R/Ca2+/PKC alpha signaling axis. Mechanistically, H2O2-induced PAR formation correlated with Ca2+-dependent DNA damage, which, however, was PKC alpha-independent. In contrast, PAR formation was completely lost upon knockdown of PKC alpha, suggesting that DNA damage alone was not sufficient for inducing PAR formation, but required a PKC alpha-dependent process. Intriguingly, the loss of PAR formation observed upon PKC alpha depletion was overcome when the chromatin structure-modifying protein HMGB1 was co-depleted with PKC alpha, suggesting that activation and nuclear translocation of PKC alpha releases the inhibitory effect of HMGB1 on PAR formation. Together, these results identify PKC alpha and HMGB1 as important co-regulators involved in H2O2-induced PAR formation, a finding that may have important relevance for oxidative stress-associated pathophysiological conditions.