NADK Isoform 3 (F5E2T) Rabbit mAb #76851

NADK, also known as NAD kinase, is a cytoplasmic protein responsible for maintaining the pool of available NADP⁺ and NADPH within the cell (1). Using ATP as a phosphate donor, NADK catalyzes the phosphorylation of NAD⁺ to NADP⁺. This molecule is then reduced to NADPH and utilized in various metabolic and biosynthetic pathways (2). NADK has been suggested to play a role in glucose metabolism due to the effect NADPH production has on both the insulin secretion and survival of pancreatic β-cells (3). NADPH has a vital role in protecting cells from oxidative stress through its neutralizing effect on reactive oxygen species (ROS), which also accumulate during cell growth (2-4). Along with the p53 tumor suppression protein, NADK has been a suggested target in cancer therapy due to its link to NADPH production and its resulting protective role on growing and proliferating cells (2).

Cytoplasmic NADK isoform 3 is transcribed from a unique start site compared to isoforms 1 and 2, and lacks the N-terminal, Akt-dependent, activating phosphorylation sites of Ser44, Ser46, and Ser48 found in the other isoforms (5). Cells engineered to exclusively express NADK isoform 3 exhibit constitutively increased NAD kinase activity, insensitivity to AKT agonists, and increased synthesis of NADP⁺ (5). NADK isoform 3 is uniquely upregulated in metastatic nodules of a PDX model of melanoma (6). Isoform 3 expression is driven by transcription factor NRF2 in response to oxidative stress, allowing melanoma cells to survive both in vitro oxidative insult and in vivo metastatic cascade by increasing NADP⁺ synthesis (6).