NADK

NADK is the cytosolic kinase that phosphorylates NAD+ to generate NADP+, the metabolic node that sets the cellular NADP(H) pool and thereby supplies reductive biosynthetic and antioxidant capacity (PMID:40316835, PMID:41462596). The human enzyme assembles into a tetramer whose catalytic output is governed by an N-terminal region absent in bacterial orthologs; this segment imposes autoinhibition that is read out through tetramer conformation, such that the activating R45H mutation raises activity and confers chemotherapy resistance while other mutations distort the tetramer and inactivate the enzyme (PMID:40330153). Multiple post-translational modifications converge on this N-terminal autoinhibitory switch: NUAK1 phosphorylates Ser64 (PMID:39159134), and these activating inputs are antagonized by PRMT6-mediated arginine methylation at R39/R41/R45. In cancer, oncogenic KRAS drives PKC-mediated phosphorylation of NADK to sustain NADP+/NADPH in pancreatic cells (PMID:34133937), and NADK transcription is induced both by H3.3 variant-dependent promoter regulation in metastatic breast cancer (PMID:36841051) and by YAP binding the NADK promoter downstream of NMRK2-driven disruption of the integrin-β/YAP complex (PMID:41762891). The NADPH produced sustains DHFR-dependent folate activation and nucleotide synthesis under low-folate conditions (PMID:40316835) and underwrites ferroptosis resistance through NADPH/FSP1 and NADPH/GSH axes, positioning NADK upstream of G6PD and ME1 in coupling NAD+ salvage to antioxidant defense (PMID:38700533, PMID:41462596).

1. 2021 Medium

   Established that NADK activity is not constitutive but is amplified by oncogenic signaling, linking KRAS-driven PKC phosphorylation to NADP(H) supply in tumor cells.

   Evidence Phosphorylation assays, PKC inhibition, and metabolomics in KRAS-mutant PDAC lines

   PMID:34133937

   Open questions at the time

   • PKC phosphosite(s) on NADK not mapped
   • single-lab cancer-cell context without structural mechanism
2. 2023 Medium

   Showed that NADK output is set transcriptionally as well as enzymatically, with H3.3 variant-mediated promoter regulation expanding NADP(H) pools to support metastatic adaptation.

   Evidence Histone variant ChIP, promoter analysis, overexpression/knockdown and metabolomics in breast cancer cells

   PMID:36841051

   Open questions at the time

   • Transcription factors recruiting H3.3 not identified
   • single-lab, breast-cancer specific
3. 2024 High

   Identified a defined activating phosphosite (S64) and a direct upstream kinase, explaining how NADK is tuned to limit ROS and drive drug resistance.

   Evidence Co-IP, in vitro kinase assay, S64 mutagenesis, NUAK1 blockade in vitro and in vivo in NSCLC

   PMID:39159134

   Open questions at the time

   • Structural basis of how S64 phosphorylation relieves autoinhibition not resolved
   • interplay with other modifications untested
4. 2024 Medium

   Defined arginine methylation as a negative regulatory input that antagonizes activating phosphorylation at the N-terminal autoinhibitory region.

   Evidence In vitro methylation and kinase assays, R39/R41/R45 mutagenesis, Akt phosphorylation crosstalk (preprint)

   Open questions at the time

   • Preprint not yet peer-reviewed
   • phosphorylation-independent inhibition mechanism unclear
   • in vivo relevance untested
5. 2025 High

   Resolved the human tetrameric architecture and showed the N-terminal region (lacking in bacteria) controls activity via tetramer conformation, providing a structural framework for the regulatory modifications.

   Evidence Cryo-EM of human NADK tetramer with mutant activity and chemotherapy-sensitivity assays

   PMID:40330153

   Open questions at the time

   • How phosphorylation/methylation/palmitoylation physically reshape the tetramer not directly visualized
   • no structure of modified enzyme
6. 2025 Medium

   Added a lipid-based activating modification, showing ZDHHC5 palmitoylates the N-terminal cysteines to relieve autoinhibition and sustain NADP+ synthesis.

   Evidence Cys22/23/26 mutagenesis, ZDHHC5 co-expression and KO mouse, in vitro kinase assays (preprint)

   Open questions at the time

   • Preprint not yet peer-reviewed
   • tissue/cell contexts requiring palmitoylation not defined
   • coordination with phospho/methyl inputs unknown
7. 2025 High

   Connected NADK output to a specific anabolic requirement, showing cytosolic NADPH is needed for DHFR activity and folate-dependent nucleotide synthesis under low folate.

   Evidence CRISPR NADK deletion, plasma-like medium folate titration, metabolic tracing and DHFR activity assays across cancer lines

   PMID:40316835

   Open questions at the time

   • Conditional nature limits generalization to folate-replete settings
   • other NADPH-dependent pathways not comprehensively mapped
8. 2025 Medium

   Placed NADK upstream of ferroptosis defense, demonstrating its NADPH output sustains FSP1 and GSH/GPX4 axes and bridges NAD+ salvage (NMN) to antioxidant protection.

   Evidence siRNA/thioNAM inhibition, overexpression, G6PD/ME1 intervention with NADPH/GSH/ROS/FSP1 readouts in LUAD and HT1080 cells, plus xenografts

   PMID:38700533 PMID:41462596

   Open questions at the time

   • Direct contribution of NADK-derived vs G6PD/ME1-derived NADPH not partitioned
   • cell-line restricted
9. 2026 High

   Defined a transcriptional activation circuit, showing NMRK2 frees YAP from the integrin-β/YAP complex to drive NADK promoter transcription and redox protection in cardiac ischemia-reperfusion.

   Evidence Co-IP, fractionation, ChIP-qPCR, luciferase reporter and NADK knockdown in cardiomyocytes and mouse I/R model

   PMID:41762891

   Open questions at the time

   • Mechanism by which NMRK2 disrupts the integrin-β/YAP complex not detailed
   • generality beyond cardiac I/R untested

• How the distinct N-terminal modifications (S64 phosphorylation, R39/41/45 methylation, Cys22/23/26 palmitoylation) are integrated structurally and competitively to set net tetramer activity in vivo remains unresolved.
• No structure of a modified NADK tetramer
• combinatorial regulation not reconstituted
• tissue-specific dominance of each input unknown