Palmitoylation-dependent activation of NADK promotes NADP+ synthesis and tumorigenesis

Abstract

NAD kinase (NADK) is the sole cytosolic enzyme that catalyzes the synthesis of nicotinamide adenine dinucleotide phosphate (NADP+) from NAD+. NADP+ is essential for anabolic reactions and redox balance. Here, we show that palmitate facilitates NADP+ synthesis by enhancing NADK palmitoylation and activity. NADK is post-translationally S-palmitoylated on three cysteine residues (Cys22, Cys23, and Cys26) within the amino-terminal domain by the protein-acyl transferase ZDHHC5, which stimulates NADK activity. Fatty acids activate NADK by enhancing its palmitoylation and relief of an autoinhibitory function inherent to its amino terminus. Furthermore, ZDHHC5-/- mice showed defect in NADK palmitoylation and NADP+ production. Clinically, elevated expression of ZDHHC5 in pancreatic cancer patients was associated with increased NADK palmitoylation and correlated with poor prognoses for patients. These data reveal that fatty-acid and ZDHHC5-mediated palmitoylation has a critical role in NADP+ synthesis and cancers.