Coronavirus infection and PARP expression dysregulate the NAD metabolome: An actionable component of innate immunity.
Level 5 - mechanism / opinion, no new human data
Preclinical bench and in vitro mechanistic study
PubMed 33051211 · doi:10.1074/jbc.RA120.015138
What was done
The authors investigated the effects of SARS-CoV-2 and murine hepatitis virus (MHV, a model coronavirus) infection on mono(ADP-ribosylating) (MARylating) PARP expression and NAD metabolome pathways in cell culture models. They examined the impact of PARP10 overexpression on cellular NAD levels and tested whether the activity of antiviral PARPs (PARP7, PARP10, PARP12, and PARP14) could be augmented by boosting NAD synthesis. Finally, they evaluated whether pharmacological activation of NAMPT or supplementation with NAD precursors (nicotinamide [NAM] and nicotinamide riboside [NR]) suppressed replication of a PARP-sensitive MHV strain.
What was found
SARS-CoV-2 infection upregulated MARylating PARP genes, stimulated the expression of salvage NAD synthesis enzymes (from NAM and NR), and downregulated other NAD biosynthetic pathways. Overexpression of PARP10 was sufficient to depress cellular NAD pools. Induction of PARP7, PARP10, PARP12, and PARP14 activity was limited by cellular NAD availability and was enhanced by pharmacological activation of NAD synthesis. MHV infection depleted host cell NAD+ and NADP+, and treatment with NAMPT activators, NAM, or NR substantially reduced replication of PARP-sensitive MHV. The abstract reported no numerical values or exact effect sizes.
Why it matters
These findings identify host NAD depletion as a vulnerability during coronavirus infection and delineate a biochemical mechanism by which MARylating PARPs consume NAD to execute innate antiviral defense. The work provides a mechanistic rationale for testing NAD-boosting strategies (such as NR or NAM) in preclinical and clinical coronavirus models.
Limits
The study is entirely preclinical and conducted in cell models; abstract findings include no animal efficacy models or human clinical data. Abstract text does not report sample sizes, specific cell lines, doses, statistical variance, or exact quantitative values for viral reduction or NAD depletion. Findings in the MHV model virus cannot be directly assumed to fully replicate SARS-CoV-2 dynamics in human tissues.
Cited by
- supports Coronavirus infection transcriptionally activates five distinct members of the PARP superfamily in infected tissues.