Subcellular NAD pools are interconnected and buffered by mitochondrial NAD.

The coenzyme NAD is consumed by signalling enzymes, including poly-ADP-ribosyltransferases (PARPs) and sirtuins. Ageing is associated with a decrease in cellular NAD levels, but how cells cope with persistently decreased NAD concentrations is unclear. Here, we show that subcellular NAD pools are interconnected, with mitochondria acting as a rheostat to maintain NAD levels upon excessive consumption.

Regulation of and challenges in targeting NAD metabolism.

Nicotinamide adenine dinucleotide, in its oxidized (NAD) and reduced (NADH) forms, is a reduction-oxidation (redox) co-factor and substrate for signalling enzymes that have essential roles in metabolism. The recognition that NAD levels fall in response to stress and can be readily replenished through supplementation has fostered great interest in the potential benefits of increasing or restoring NAD levels in humans to prevent or delay diseases and degenerative processes. However, much about the biology of NAD and related molecules remains poorly understood.

Evolution of fungal tuberculosis necrotizing toxin (TNT) domain-containing enzymes reveals divergent adaptations to enhance NAD cleavage.

Tuberculosis necrotizing toxin (TNT) is a protein domain discovered on the outer membrane of Mycobacterium tuberculosis (Mtb), and the fungal pathogen Aspergillus fumigatus. TNT domains have pure NAD(P) hydrolytic activity, setting them apart from other NAD-cleaving domains such as ADP-ribosyl cyclase and Toll/interleukin-1 receptor homology (TIR) domains which form a wider set of products. Importantly, the Mtb TNT domain has been shown to be involved in immune evasion via depletion of the intracellular NAD pool of macrophages.

Novel Calcium-Binding Motif Stabilizes and Increases the Activity of Ecto-NADase.

Nicotinamide adenine dinucleotide (NAD) is an essential molecule in all kingdoms of life, mediating energy metabolism and cellular signaling. Recently, a new class of highly active fungal surface NADases was discovered. The enzyme from the opportunistic human pathogen was thoroughly characterized.

Dynamics of SLC25A51 reveal preference for oxidized NAD and substrate led transport.

SLC25A51 is a member of the mitochondrial carrier family (MCF) but lacks key residues that contribute to the mechanism of other nucleotide MCF transporters. Thus, how SLC25A51 transports NAD across the inner mitochondrial membrane remains unclear. To elucidate its mechanism, we use Molecular Dynamics simulations to reconstitute SLC25A51 homology models into lipid bilayers and to generate hypotheses to test.

Identification of structural determinants of nicotinamide phosphoribosyl transferase (NAMPT) activity and substrate selectivity.

NAD homeostasis in mammals requires the salvage of nicotinamide (Nam), which is cleaved from NAD by sirtuins, PARPs, and other NAD-dependent signaling enzymes. Nam phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in vitamin B3 salvage, whereby Nam reacts with phosphoribosyl pyrophosphate (PRPP) to form nicotinamide mononucleotide. NAMPT has a high affinity towards Nam, which is further enhanced by autophosphorylation of His247.

Nondestructive thermographic detection of internal defects using pixel-pattern based laser excitation and photothermal super resolution reconstruction.

In this work, we present a novel approach to photothermal super resolution based thermographic resolution of internal defects using two-dimensional pixel pattern-based active photothermal laser heating in conjunction with subsequent numerical reconstruction to achieve a high-resolution reconstruction of internal defect structures. With the proposed adoption of pixelated patterns generated using laser coupled high-power DLP projector technology the complexity for achieving true two-dimensional super resolution can be dramatically reduced taking a crucial step forward towards widespread practical viability. Furthermore, based on the latest developments in high-power DLP projectors, we present their first application for structured pulsed thermographic inspection of macroscopic metal samples.

Purine nucleoside phosphorylase controls nicotinamide riboside metabolism in mammalian cells.

Nicotinamide riboside (NR) is an effective precursor of nicotinamide adenine dinucleotide (NAD) in human and animal cells. NR supplementation can increase the level of NAD in various tissues and thereby improve physiological functions that are weakened or lost in experimental models of aging or various human pathologies. However, there are also reports questioning the efficacy of NR supplementation.

Learned Block Iterative Shrinkage Thresholding Algorithm for Photothermal Super Resolution Imaging.

Block-sparse regularization is already well known in active thermal imaging and is used for multiple-measurement-based inverse problems. The main bottleneck of this method is the choice of regularization parameters which differs for each experiment. We show the benefits of using a learned block iterative shrinkage thresholding algorithm (LBISTA) that is able to learn the choice of regularization parameters, without the need to manually select them.

Early Evolutionary Selection of NAD Biosynthesis Pathway in Bacteria.

Bacteria use two alternative pathways to synthesize nicotinamide adenine dinucleotide (NAD) from nicotinamide (Nam). A short, two-step route proceeds through nicotinamide mononucleotide (NMN) formation, whereas the other pathway, a four-step route, includes the deamidation of Nam and the reamidation of nicotinic acid adenine dinucleotide (NAAD) to NAD. In addition to having twice as many enzymatic steps, the four-step route appears energetically unfavourable, because the amidation of NAAD includes the cleavage of ATP to AMP.

The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease.

We conducted a double-blinded phase I clinical trial to establish whether nicotinamide adenine dinucleotide (NAD) replenishment therapy, via oral intake of nicotinamide riboside (NR), is safe, augments cerebral NAD levels, and impacts cerebral metabolism in Parkinson's disease (PD). Thirty newly diagnosed, treatment-naive patients received 1,000 mg NR or placebo for 30 days. NR treatment was well tolerated and led to a significant, but variable, increase in cerebral NAD levels-measured by phosphorous magnetic resonance spectroscopy-and related metabolites in the cerebrospinal fluid.

Combined Metabolic and Chemical (CoMetChem) Labeling Using Stable Isotopes-a Strategy to Reveal Site-Specific Histone Acetylation and Deacetylation Rates by LC-MS.

Histone acetylation is an important, reversible post-translational protein modification and a hallmark of epigenetic regulation. However, little is known about the dynamics of this process, due to the lack of analytical methods that can capture site-specific acetylation and deacetylation reactions. We present a new approach that combines metabolic and chemical labeling (CoMetChem) using uniformly 13C-labeled glucose and stable isotope-labeled acetic anhydride.

The balance between NAD biosynthesis and consumption in ageing.

Nicotinamide adenine dinucleotide (NAD) is a vital coenzyme in redox reactions. NAD is also important in cellular signalling as it is consumed by PARPs, SARM1, sirtuins and CD38. Cellular NAD levels regulate several essential processes including DNA repair, immune cell function, senescence, and chromatin remodelling.

Enzymatic and Chemical Syntheses of Vacor Analogs of Nicotinamide Riboside, NMN and NAD.

It has recently been demonstrated that the rat poison vacor interferes with mammalian NAD metabolism, because it acts as a nicotinamide analog and is converted by enzymes of the NAD salvage pathway. Thereby, vacor is transformed into the NAD analog vacor adenine dinucleotide (VAD), a molecule that causes cell toxicity. Therefore, vacor may potentially be exploited to kill cancer cells.

Instability in NAD metabolism leads to impaired cardiac mitochondrial function and communication.

Poly(ADP-ribose) polymerase (PARP) enzymes initiate (mt)DNA repair mechanisms and use nicotinamide adenine dinucleotide (NAD) as energy source. Prolonged PARP activity can drain cellular NAD reserves, leading to de-regulation of important molecular processes. Here, we provide evidence of a pathophysiological mechanism that connects mtDNA damage to cardiac dysfunction via reduced NAD levels and loss of mitochondrial function and communication.

ADP-ribosyltransferases, an update on function and nomenclature.

ADP-ribosylation, a modification of proteins, nucleic acids, and metabolites, confers broad functions, including roles in stress responses elicited, for example, by DNA damage and viral infection and is involved in intra- and extracellular signaling, chromatin and transcriptional regulation, protein biosynthesis, and cell death. ADP-ribosylation is catalyzed by ADP-ribosyltransferases (ARTs), which transfer ADP-ribose from NAD onto substrates. The modification, which occurs as mono- or poly-ADP-ribosylation, is reversible due to the action of different ADP-ribosylhydrolases.

Welcome to the Family: Identification of the NAD Transporter of Animal Mitochondria as Member of the Solute Carrier Family SLC25.

Subcellular compartmentation is a fundamental property of eukaryotic cells. Communication and metabolic and regulatory interconnectivity between organelles require that solutes can be transported across their surrounding membranes. Indeed, in mammals, there are hundreds of genes encoding solute carriers (SLCs) which mediate the selective transport of molecules such as nucleotides, amino acids, and sugars across biological membranes.

Discovery of fungal surface NADases predominantly present in pathogenic species.

Nicotinamide adenine dinucleotide (NAD) is a key molecule in cellular bioenergetics and signalling. Various bacterial pathogens release NADase enzymes into the host cell that deplete the host's NAD pool, thereby causing rapid cell death. Here, we report the identification of NADases on the surface of fungi such as the pathogen Aspergillus fumigatus and the saprophyte Neurospora crassa.

Equilibrative Nucleoside Transporters Mediate the Import of Nicotinamide Riboside and Nicotinic Acid Riboside into Human Cells.

Nicotinamide riboside (NR), a new form of vitamin B3, is an effective precursor of nicotinamide adenine dinucleotide (NAD) in human and animal cells. The introduction of NR into the body effectively increases the level of intracellular NAD and thereby restores physiological functions that are weakened or lost in experimental models of aging and various pathologies. Despite the active use of NR in applied biomedicine, the mechanism of its transport into mammalian cells is currently not understood.