scholarly journals Sperm express a Ca2+-regulated NAADP synthase

2008 ◽  
Vol 411 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Sridhar R. Vasudevan ◽  
Antony Galione ◽  
Grant C. Churchill
Keyword(s):  
Nicotinic Acid ◽  
Sea Urchin ◽  
Second Messenger ◽  
Cell Types ◽  
Substrate Selectivity ◽  
Base Exchange ◽  
Adp Ribosyl Cyclase ◽  
Wide Range ◽  
Sea Urchin Sperm ◽  
Exchange Activity

NAADP (nicotinic acid–adenine dinucleotide phosphate), the most potent Ca2+-mobilizing second messenger, is active in a wide range of organisms and cell types. Until now, all NAADP-producing enzymes have been thought to be members of the ADP-ribosyl cyclase family. ADP-ribosyl cyclases exhibit promiscuous substrate selectivity, synthesize a variety of products and are regulated in a limited manner, which may be non-physiological. In the present paper, we report the presence of an enzyme on the surface of sea urchin sperm that exhibits bell-shaped regulation by Ca2+ over a range (EC50 of 10 nM and IC50 of 50 μM) that is physiologically relevant. Uniquely, this surface enzyme possesses complete selectivity for nucleotides with a 2′-phosphate group and exhibits only base-exchange activity without any detectable cyclase activity. Taken together, these findings indicate that this novel enzyme should be considered as the first true NAADP synthase.

scholarly journals Channelling of substrate promiscuity of the skeletal-muscle ADP-ribosyl cyclase isoform

2004 ◽  
Vol 381 (1) ◽  
pp. 147-154 ◽  
Author(s):  
Ingrid BACHER ◽  
Andreas ZIDAR ◽  
Martin KRATZEL ◽  
Martin HOHENEGGER
Keyword(s):  
Skeletal Muscle ◽  
Nicotinic Acid ◽  
Exchange Reaction ◽  
Second Messengers ◽  
Cyclization Reaction ◽  
Regulation Mechanism ◽  
Base Exchange ◽  
Adp Ribosyl Cyclase ◽  
Highly Sensitive ◽  
Cyclic Adp Ribose

The novel Ca2+-mobilizing second messengers cADPr (cyclic ADP-ribose) and NAADP (nicotinic acid–adenine dinucleotide phosphate) are both synthesized by ADP-ribosyl cyclases. Using HSR (heavy sarcoplasmic reticulum) fractions from rabbit skeletal muscle, NAADP-induced Ca2+ release was observed. In the present paper, we show in HSR membranes the formation of authentic cADPr, cGDPr (cyclic GDP-ribose) and NAADP. The cyclization reaction to form cADPr and cGDPr as well as the base-exchange reaction to form NAADP were strictly dependent on pH. Although the formation of cGDPr is optimized at pH 6, the synthesis of NAADP was most pronounced at a pH below 5. A novel regulation mechanism is provided for nicotinic acid, the co-substrate for NAADP synthesis. Nicotinic acid had virtually no influence on the cyclization reaction, but increased the affinity of NADP at an acidic pH and had the opposite effect at alkaline pH. Nicotinamide, the side product of cADPr synthesis, is an inhibitor of the cyclization reaction (IC50, 0.7±0.1 mM) and was 30-fold more potent at suppressing the base-exchange reaction. Although the synthesis of NAADP was highly sensitive to nicotinamide inhibition, this was not via a competition with the nicotinic-acid-binding site. In contrast with the ecto-ADP-ribosyl cyclase (CD38), the cyclization and base-exchange reaction of the skeletal muscle isoform was inhibited by Cu2+ and Zn2+, while other bivalent cations such as Ca2+, Mg2+ and Mn2+ had virtually no effect. These findings allow for the prediction of a novel ADP-ribosyl cyclase isoform in skeletal muscle HSR, other than CD38. Hence the enzymic prerequisite for cADPr- and NAADP-mediated Ca2+ signalling is present.

scholarly journals Unique kinetics of nicotinic acid–adenine dinucleotide phosphate (NAADP) binding enhance the sensitivity of NAADP receptors for their ligand

2000 ◽  
Vol 352 (3) ◽  
pp. 725-729 ◽  
Author(s):  
Sandip PATEL ◽  
Grant C. CHURCHILL ◽  
Antony GALIONE
Keyword(s):  
Nicotinic Acid ◽  
Sea Urchin ◽  
Binding Sites ◽  
Cell Types ◽  
Unique Property ◽  
Single Class ◽  
High Affinity ◽  
Sea Urchin Egg ◽  
Low Concentrations ◽  
Kinetics Of

Nicotinic acidŐadenine dinucleotide phosphate (NAADP) is a novel and potent Ca2+-mobilizing agent in sea urchin eggs and other cell types. Little is known, however, concerning the properties of the putative intracellular NAADP receptor. In the present study we have characterized NAADP binding sites in sea urchin egg homogenates. [32P]NAADP bound to a single class of high-affinity sites that were reversibly inhibited by NaCl but insensitive to pH and Ca2+. Binding of [32P]NAADP was lost in preparations that did not mobilize Ca2+ in response to NAADP, indicating that [32P]NAADP probably binds to a receptor mediating Ca2+ mobilization. Addition of excess unlabelled NAADP, at various times after initiation of [32P]NAADP binding, did not result in displacement of bound [32P]NAADP. These data show that NAADP becomes irreversibly bound to its receptor immediately upon association. Accordingly, incubation of homogenates with low concentrations of NAADP resulted in maximal labelling of NAADP binding sites. This unique property renders NAADP receptors exquisitely sensitive to their ligand, thereby allowing detection of minute changes in NAADP levels.

scholarly journals Modulation of spontaneous transmitter release from the frog neuromuscular junction by interacting intracellular Ca2+ stores: critical role for nicotinic acid-adenine dinucleotide phosphate (NAADP)

2003 ◽  
Vol 373 (2) ◽  
pp. 313-318 ◽  
Author(s):  
Eugen BRAILOIU ◽  
Sandip PATEL ◽  
Nae J. DUN
Keyword(s):  
Neuromuscular Junction ◽  
Nicotinic Acid ◽  
Transmitter Release ◽  
Critical Role ◽  
Cell Types ◽  
Functional Coupling ◽  
Frog Neuromuscular Junction ◽  
Wide Range ◽  
Sphingosine 1 Phosphate ◽  
First Time

Nicotinic acid–adenine dinucleotide phosphate (NAADP) is a recently described potent intracellular Ca2+-mobilizing messenger active in a wide range of diverse cell types. In the present study, we have investigated the interaction of NAADP with other Ca2+-mobilizing messengers in the release of transmitter at the frog neuromuscular junction. We show, for the first time, that NAADP enhances neurosecretion in response to inositol 1,4,5-trisphosphate (IP3), cADP-ribose (cADPR) and sphingosine 1-phosphate (S1P), but not sphingosylphosphorylcholine. Thapsigargin was without effect on transmitter release in response to NAADP, but blocked the responses to subsequent application of IP3, cADPR and S1P and their potentiation by NAADP. Asynchronous neurotransmitter release may therefore involve functional coupling of endoplasmic reticulum Ca2+ stores with distinct Ca2+ stores targeted by NAADP.

scholarly journals NAADP induces pH changes in the lumen of acidic Ca2+ stores

2007 ◽  
Vol 402 (2) ◽  
pp. 301-310 ◽  
Author(s):  
Anthony J. Morgan ◽  
Antony Galione
Keyword(s):  
Nicotinic Acid ◽  
Direct Effect ◽  
Sea Urchin ◽  
Cell Types ◽  
Receptor Activation ◽  
Fluorescence Measurements ◽  
Low Concentrations ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Organelles ◽  
First Time

NAADP (nicotinic acid–adenine dinucleotide phosphate)-induced Ca2+ release has been proposed to occur selectively from acidic stores in several cell types, including sea urchin eggs. Using fluorescence measurements, we have investigated whether NAADP-induced Ca2+ release alters the pHL (luminal pH) within these acidic stores in egg homogenates and observed their prompt, concentration-dependent alkalinization by NAADP (but not β-NAD+ or NADP). Like Ca2+ release, the pHL change was desensitized by low concentrations of NAADP suggesting it was secondary to NAADP receptor activation. Moreover, this was a direct effect of NAADP upon the acidic stores and not secondary to increases in cytosolic Ca2+ as it was not mimicked by IP3 (inositol 1,4,5-trisphosphate), cADPR (cyclic adenine diphosphoribose), ionomycin, thapsigargin or by direct addition of Ca2+, and was not blocked by EGTA. The results of the present study further support acidic stores as targets for NAADP and for the first time reveal an adjunct role for NAADP in regulating the pHL of intracellular organelles.

scholarly journals BST1 regulates nicotinamide riboside metabolism via its glycohydrolase and base-exchange activities

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Keisuke Yaku ◽  
Sailesh Palikhe ◽  
Hironori Izumi ◽  
Tomoyuki Yoshida ◽  
Keisuke Hikosaka ◽  
...  
Keyword(s):  
Nicotinic Acid ◽  
Bone Marrow Stromal Cell ◽  
Late Phase ◽  
Salvage Pathway ◽  
Base Exchange ◽  
Nicotinamide Riboside ◽  
Beneficial Effects ◽  
Orally Bioavailable ◽  
Exchange Activity

AbstractNicotinamide riboside (NR) is one of the orally bioavailable NAD+ precursors and has been demonstrated to exhibit beneficial effects against aging and aging-associated diseases. However, the metabolic pathway of NR in vivo is not yet fully understood. Here, we demonstrate that orally administered NR increases NAD+ level via two different pathways. In the early phase, NR was directly absorbed and contributed to NAD+ generation through the NR salvage pathway, while in the late phase, NR was hydrolyzed to nicotinamide (NAM) by bone marrow stromal cell antigen 1 (BST1), and was further metabolized by the gut microbiota to nicotinic acid, contributing to generate NAD+ through the Preiss–Handler pathway. Furthermore, we report BST1 has a base-exchange activity against both NR and nicotinic acid riboside (NAR) to generate NAR and NR, respectively, connecting amidated and deamidated pathways. Thus, we conclude that BST1 plays a dual role as glycohydrolase and base-exchange enzyme during oral NR supplementation.

Recruitment of NAADP-sensitive acidic Ca2+ stores by glutamate

2009 ◽  
Vol 422 (3) ◽  
pp. 503-512 ◽  
Author(s):  
Vinita Pandey ◽  
Chia-Chen Chuang ◽  
Alexander M. Lewis ◽  
Parvinder K. Aley ◽  
Eugen Brailoiu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nicotinic Acid ◽  
Hippocampal Neurons ◽  
Second Messenger ◽  
Cell Types ◽  
The Brain ◽  
Acidic Compartments

NAADP (nicotinic acid–adenine dinucleotide phosphate) is an unusual second messenger thought to mobilize acidic Ca2+ stores, such as lysosomes or lysosome-like organelles, that are functionally coupled to the ER (endoplasmic reticulum). Although NAADP-sensitive Ca2+ stores have been described in neurons, the physiological cues that recruit them are not known. Here we show that in both hippocampal neurons and glia, extracellular application of glutamate, in the absence of external Ca2+, evoked cytosolic Ca2+ signals that were inhibited by preventing organelle acidification or following osmotic bursting of lysosomes. The sensitivity of both cell types to glutamate correlated well with lysosomal Ca2+ content. However, interfering with acidic compartments was largely without effect on the Ca2+ content of the ER or Ca2+ signals in response to ATP. Glutamate but not ATP elevated cellular NAADP levels. Our results provide evidence for the agonist-specific recruitment of NAADP-sensitive Ca2+ stores by glutamate. This links the actions of NAADP to a major neurotransmitter in the brain.

scholarly journals PROGRAMMED AXON DEATH EXECUTOR SARM1 IS A MULTI-FUNCTIONAL NAD(P)ASE WITH PROMINENT BASE EXCHANGE ACTIVITY, ALL REGULATED BY PHYSIOLOGICAL LEVELS OF NMN, NAD, NADP AND OTHER METABOLITES

2021 ◽  
Author(s):  
Carlo Angeletti ◽  
Adolfo Amici ◽  
Jonathan Gilley ◽  
Andrea Loreto ◽  
Antonio G Trapanotto ◽  
...  
Keyword(s):  
Axon Degeneration ◽  
Allosteric Site ◽  
Base Exchange ◽  
Nad Glycohydrolase ◽  
Neutral Ph ◽  
Adp Ribosyl Cyclase ◽  
Nad Synthesis ◽  
Regulatory Effects ◽  
Essential Enzyme ◽  
Exchange Activity

SARM1 is an NAD glycohydrolase and TLR adapter with an essential, prodegenerative role in programmed axon death (Wallerian degeneration). It has low basal NADase activity that becomes strongly activated by NAD precursor NMN. Very high levels of NAD oppose this activation, competing for the same allosteric site on SARM1′s regulatory ARM domain. Injury or diseases that deplete axons of NMNAT2, an essential enzyme converting NMN to NAD, cause SARM1 activation. The resulting NAD degradation by SARM1, combined with loss of NAD synthesis by NMNAT2, causes rapid depletion of axonal NAD. This NAD loss is widely assumed to mediate axon death and is consequently a key focus for therapeutic strategies for axonopathies. However, like other NAD(P) glycohydrolases, SARM1 has additional enzyme activities whose contributions, consequences and regulation need to be fully understood. Here, we compare the multiple actions and regulation of recombinant human SARM1 with those of two other NAD(P) glycohydrolases, human CD38 and Aplysia californica ADP ribosyl cyclase. We find that SARM1 has the highest transglycosidation (base exchange) activity of these enzymes at neutral pH and with some bases this dominates NAD(P) hydrolysis and cyclisation. Moreover, like its NADase and NADPase reactions, SARM1-mediated base exchange at neutral pH is activated by increases in the NMN:NAD ratio, which we show for the first time can act in the presence of physiological levels of both metabolites. We establish that SARM1 base exchange is the most likely physiological source of calcium mobilizing agent NaADP, and potentially of other NAD(P) analogues, which could contribute to axon and cell death. We also identify regulatory effects of free pyridine bases, of NADP and of nicotinic acid riboside (NaR) on SARM1 that represent further therapeutic opportunities. These data will help to pinpoint which of the multiple functions of SARM1 is responsible for axon degeneration and how it can be optimally targeted to block axon degeneration in disease.

scholarly journals Modulation of NAADP (nicotinic acid–adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations

2003 ◽  
Vol 375 (3) ◽  
pp. 805-812 ◽  
Author(s):  
George D. DICKINSON ◽  
Sandip PATEL
Keyword(s):  
Nicotinic Acid ◽  
Sea Urchin ◽  
Cell Types ◽  
Target Protein ◽  
Inhibitory Effects ◽  
Sea Urchin Eggs ◽  
Sea Urchin Egg ◽  
Multiple Conformations ◽  
Partial Dissociation ◽  
Low K

NAADP (nicotinic acid–adenine dinucleotide phosphate) mediates Ca2+ release from intracellular Ca2+ stores in a wide variety of cell types. In sea urchin eggs, subthreshold concentrations of NAADP can cause full inactivation of NAADP-induced Ca2+ release, an effect that may be related to the ability of the target protein to bind its ligand in an essentially irreversible manner. In the present study, we found that K+ ions inhibit dissociation of NAADP from sea urchin egg homogenates. In low K+-containing media, an addition of excess unlabelled NAADP effectively displaced bound radioligand whereas dilution of radioligand initiated only partial dissociation. The inhibitory effects of K+ on dissociation of NAADP were concentration dependent, reversible and persisted after detergent solubilization. Lowering [K+] of the medium decreased the sensitivity of NAADP receptors for their ligand in stimulating Ca2+ release, but it did not affect inactivation of NAADP-induced Ca2+ release by subthreshold concentrations of NAADP. Our results are consistent with the observation of multiple conformations of the NAADP receptor that are readily revealed in low K+-containing media.

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