Mitochondrial NAD+ Controls Nuclear ARTD1-Induced ADP-Ribosylation

Summary In addition to its role as an electron transporter, mitochondrial nicotinamide adenine dinucleotide (NAD+) is an important co-factor for enzymatic reactions, including ADP-ribosylation. Although mitochondria harbor the most intra-cellular NAD+, mitochondrial ADP-ribosylation remains poorly understood. Here we provide evidence for mitochondrial ADP-ribosylation, which was identified using various methodologies including immunofluorescence, western blot, and mass spectrometry. We show that mitochondrial ADP-ribosylation reversibly increases in response to respiratory chain inhibition. Conversely, H2O2-induced oxidative stress reciprocally induces nuclear and reduces mitochondrial ADP-ribosylation. Elevated mitochondrial ADP-ribosylation, in turn, dampens H2O2-triggered nuclear ADP-ribosylation and increases MMS-induced ARTD1 chromatin retention. Interestingly, co-treatment of cells with the mitochondrial uncoupler FCCP decreases PARP inhibitor efficacy. Together, our results suggest that mitochondrial ADP-ribosylation is a dynamic cellular process that impacts nuclear ADP-ribosylation and provide evidence for a NAD+-mediated mitochondrial-nuclear crosstalk.
Graphical Abstract
Highlights • Mitochondrial ADP-ribosylation was identified by different methods • Mitochondrial ADP-ribosylation reversibly increased after respiratory chain inhibition • H2O2 treatment induces nuclear and reduces mitochondrial ADP-ribosylation • Elevated mitochondrial ADP-ribosylation dampened MMS-induced ARTD1 chromatin retention
Hopp et al. detect mitochondrial ADP-ribosylation and characterize its dependency on intracellular NAD+ homeostasis. While respiratory chain inhibition increases mitochondrial ADP-ribosylation, hydrogen peroxide treatment reduces mitochondrial ADP-ribosylation and reciprocally induces nuclear ADP-ribosylation. This dynamic and reversable process is dependent on a NAD+-dependent mitochondrial-nuclear crosstalk.