GO:1901847 nicotinate metabolic process

Nicotinate metabolic process (GO:1901847) encompasses the chemical reactions and pathways involving nicotinate, the ionized form of nicotinic acid (vitamin B3). Nicotinate is a key metabolite in the biosynthesis and salvage of nicotinamide adenine dinucleotide (NAD+), an essential coenzyme in redox reactions and a substrate for signaling enzymes such as sirtuins and PARPs. The term is defined in the Gene Ontology as 'The chemical reactions and pathways involving nicotinate' and is classified as a biological process. Understanding this process is fundamental for researchers in nutrition, metabolism, and drug development because nicotinate sits at the intersection of vitamin metabolism, lipid regulation, and cellular energy homeostasis. Historically, the biogenesis of water-soluble vitamins including nicotinate was elucidated in the mid-20th century, and later work revealed that nicotinate is also produced by plants and microorganisms as part of alkaloid and cofactor biosynthesis. In humans, nicotinate is obtained from diet and from the salvage of nicotinamide, and it can be converted to NAD+ via the Preiss-Handler pathway. Pharmacological doses of nicotinic acid (nicotinate) have been used for decades to treat dyslipidemia, although the mechanisms involve GPR109A receptor activation and are distinct from its vitamin role. Recent research has expanded the scope of nicotinate metabolism to include its role in plant stress responses, where nicotinate O-glucosylation affects seed germination, and in ligand recognition by alicarboxylic acid receptors. This article synthesizes authoritative QuickGO data and verified PubMed literature to provide a research-grade overview of GO:1901847, covering its definition, molecular players, disease relevance, and experimental strategies for CRISPR-based interrogation.

In our own words, GO:1901847 (nicotinate metabolic process) refers to the sum of biochemical transformations that involve nicotinate as a substrate, intermediate, or product. This includes its synthesis from tryptophan or aspartate in some organisms, its conversion to nicotinamide mononucleotide (NMN) and NAD+, its conjugation to sugars or amino acids for storage or excretion, and its interconversion with nicotinamide. The term is a biological process and is synonymous with 'nicotinate metabolism'.

Nicotinate metabolic process is critically important because it governs the availability of NAD+, a coenzyme required for hundreds of redox reactions and for signaling pathways that control metabolism, DNA repair, and cell survival. In humans, nicotinate is a vitamin (B3) and a drug (nicotinic acid) that lowers LDL cholesterol and triglycerides while raising HDL, making its metabolism a direct therapeutic target. In plants, nicotinate metabolism influences seed germination under abiotic stress, with implications for agriculture. Moreover, dysregulation of NAD+ homeostasis is implicated in aging, neurodegeneration, and cancer, so understanding how nicotinate is processed offers opportunities for intervention.

The following genes and proteins are central to nicotinate metabolic process across species, with roles in synthesis, salvage, transport, and regulation.

Nicotinate metabolic process is regulated at multiple levels. In humans, the expression of NAPRT and NMNAT is controlled by nutrient availability and stress-responsive transcription factors such as p53 and HIF-1α. NAD+ levels feedback to inhibit NAPRT and NAMPT, while circadian clock components modulate NAMPT expression. In plants, nicotinate O-glucosylation is induced by abiotic stress, likely through abscisic acid signaling. Additionally, the receptor GPR109A mediates rapid signaling in response to pharmacological nicotinate, leading to downstream effects on lipid metabolism. These regulatory layers ensure that nicotinate is directed toward NAD+ synthesis or storage as needed.

Pharmacological doses of nicotinic acid (nicotinate) have been used for decades to treat dyslipidemia by lowering LDL cholesterol and triglycerides and raising HDL cholesterol. The mechanism involves activation of GPR109A on adipocytes, which reduces lipolysis and free fatty acid flux to the liver. However, flushing and other side effects limit compliance, and recent trials have shown mixed cardiovascular outcomes. Understanding nicotinate metabolism is essential for developing better antidyslipidemic drugs.

Defects in the de novo NAD+ synthesis pathway, which converges with nicotinate metabolism, cause congenital malformations in humans and mice. Mutations in HAAO or KYNU lead to NAD deficiency and vertebral, cardiac, and renal anomalies. Supplementation with nicotinic acid can rescue these defects in animal models, highlighting the therapeutic potential of targeting nicotinate metabolism.

Many cancers upregulate NAPRT and other NAD+ biosynthetic enzymes to support rapid proliferation and DNA repair. Targeting nicotinate metabolism, such as inhibiting NAPRT or NAMPT, is a promising strategy for cancer therapy. Additionally, NAD+ depletion sensitizes cancer cells to chemotherapy and radiation.

NAD+ levels decline with age and in neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. Boosting NAD+ via nicotinate or other precursors has shown neuroprotective effects in animal models. Sirtuins, which consume NAD+, are key mediators of these effects, linking nicotinate metabolism to longevity and stress resistance.

Liquid chromatography-mass spectrometry (LC-MS) can quantify nicotinate, nicotinamide, NMN, and NAD+ in cells and tissues. Stable isotope tracing with 13C-nicotinate allows measurement of flux through the Preiss-Handler pathway and salvage routes. These methods are essential for validating CRISPR knockout effects on nicotinate metabolism.

Enzyme activities of NAPRT, NMNAT, and NADSYN1 can be measured in cell lysates using colorimetric or fluorometric assays. These assays help determine whether a genetic perturbation affects catalytic efficiency or protein stability.

RNA-seq and quantitative proteomics can reveal changes in expression of nicotinate metabolism genes upon CRISPR editing or drug treatment. Pathway enrichment analysis identifies coordinated regulation of NAD+ biosynthesis.

Fluorescent biosensors such as Peredox or NAD+ sensors allow real-time monitoring of NAD+ levels in live cells. These tools can be used with CRISPR knockouts to study dynamic changes in nicotinate metabolism.

Researchers studying nicotinate metabolic process-related genes often need to determine whether a candidate gene is causally involved in NAD+ homeostasis, lipid regulation, or stress responses. Generating precise genetic models is essential to move from correlation to causation.

GO:1901847 (nicotinate metabolic process) is a fundamental biological process that bridges vitamin metabolism, NAD+ homeostasis, and lipid regulation. Its clinical relevance spans dyslipidemia, cancer, neurodegeneration, and congenital disorders, making it a rich area for therapeutic development. Advances in CRISPR gene editing and metabolomics now allow precise interrogation of this pathway in diverse model systems. By leveraging these tools, researchers can uncover new targets and mechanisms to modulate nicotinate metabolism for human health.