Abstract: FR-PO180
HNF4α Links PGC1α to Quinolinate Phosphoribosyl Transferase (QPRT) and De Novo NAD+ Biosynthesis
Session Information
- AKI: Mechanisms - II
November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
Authors
- Clark, Amanda J., The University of Texas Southwestern Medical Center Department of Internal Medicine, Dallas, Texas, United States
- Parikh, Samir M., The University of Texas Southwestern Medical Center Department of Internal Medicine, Dallas, Texas, United States
Background
De novo NAD+ biosynthesis is suppressed in acute kidney injury (AKI), particularly the bottleneck enzyme Quinolinate Phosphoribosyl Transferase (QPRT), leading to NAD+ reduction and accumulation of upstream metabolites. We previously showed that QPRT is regulated by PPARgamma coactivator 1 alpha (PGC1a), a transcriptional co-activator that regulates many genes involved in metabolism and mitochondrial biogenesis. A transcription factor (TF) linking PGC1a and QPRT has not been identified.
Methods
The ENCODE TF Database was compared with Biogrid and the Human Reference Protein Interactome to identify TFs that interact with PGC1α and bind QPRT. Expression of PGC1α, HNF4α, and QPRT was assessed with qPCR. Compartment-specific NAD+ was measured using transfected biosensors. ATP and ChIP qPCR was measured via commercial assay.
Results
Analysis of public datasets identified HNF4α and RXRA as candidate TFs modulating QPRT via PGC1α. We focused on HNF4α as no RXRA mutations associate with kidney disease. HNF4α was suppressed in AKI proportionally to QPRT (R2=0.5, P<0.01). HNF4α overexpression increased QPRT expression (1.27 fold change [FC], p<0.01), and HNF4α mirrored both QPRT and PGC1α with increased cellular NAD+ and ATP with HNF4α overexpression (NAD+ in cytoplasm 1.08FC, p<0.001; mitochondria 1.06FC, p<0.05; nucleus 1.09FC, p<0.05) (ATP 1.08FC, p<0.001) and decreased NAD+ and ATP with siHNF4α (NAD+ in cytoplasm 0.86FC, p<0.001; mitochondria 0.89FC, p<0.05; nucleus 0.86FC, p<0.05) (ATP 0.91FC, p<0.01). ChIP qPCR showed that HNF4α binds the QPRT locus in kidney (12.7FC over IgG) proportionally with PGC1α expression (R2=0.58, p<0.05). Finally, siHNF4a co-transfected with PGC1α plasmids prevented PGC1α-induced increase in QPRT expression (PGC1α overexpression = 1.34FC increase in QPRT, p<0.001; PGC1α overexpression with siHNF4α = 1.1 FC in QPRT, p=0.19).
Conclusion
HNF4α is a known regulator of metabolic pathways in the liver and a critical component of kidney cell differentiation, but few studies have examined the role of HNF4α in adult kidney. This is relevant as recent multi-omics investigations have identified HNF4α recovery after injury as a critical feature of “recovered” tubular cells. In summary, the present results identify a transcriptional mechanism for HNF4α in regulating de novo NAD+ biosynthesis suppression in AKI.
Funding
- NIDDK Support