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 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 Characterization of the inositol 1,4,5-trisphosphate-induced calcium release from permeabilized endocrine cells and its inhibition by decavanadate and p-hydroxymercuribenzoate

1989 ◽  
Vol 262 (1) ◽  
pp. 83-89 ◽  
Author(s):  
K J Föhr ◽  
J Scott ◽  
G Ahnert-Hilger ◽  
M Gratzl
Keyword(s):  
Endocrine Cells ◽  
Calcium Release ◽  
Cell Types ◽  
Inhibitory Effect ◽  
Maximal Effect ◽  
Thiol Compounds ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dependent Inhibition ◽  
Pheochromocytoma Pc12 ◽  
First Time

The inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ compartment of endocrine cells was studied with alpha-toxin- and digitonin-permeabilized rat insulinoma (RINA2) and rat pheochromocytoma (PC12) cells. The Ca2+ uptake was ATP-dependent, and submicromolar concentrations of IP3 specifically released the stored Ca2+. Half-maximal Ca2+ release was observed with 0.25-0.5 mumol of IP3/l, and the amount of Ca2+ released due to IP3 could be enhanced by additional loading of the Ca2+ compartment. Consecutive additions of the same concentration of IP3 for 1-2 h always released the same amount of Ca2+ without desensitization, providing an ideal basis to further characterize the IP3-induced Ca2+ release. Here we describe for the first time a reversible inhibitory effect of decavanadate on the IP3-induced Ca2+ release. Among the vanadium species tested (decavanadate, oligovanadate and monovanadate), only decavanadate was inhibitory, with a half-maximal effect at 5 mumol/l in both cell types. The effect of decavanadate could be overcome by increasing the amount of sequestered Ca2+ or added IP3. Decavanadate did not affect the ATP-driven Ca2+ uptake but oligovanadate was inhibitory on Ca2+ uptake. p-Hydroxymercuribenzoate (pHMB) at concentrations between 10 and 30 mumol/l also inhibited the Ca2+ release due to IP3. Thiol compounds such as dithiothreitol (DTT; 1 mmol/l) added before pHMB removed all its inhibitory effect on the IP3-induced Ca2+ release, whereas the inhibition caused by decavanadate was unaffected by DTT. Thus, the decavanadate-dependent inhibition functions by a distinctly different mechanism than pHMB and could serve as a specific tool to analyse various aspects of the IP3-induced Ca2+ release within endocrine cells.

scholarly journals Ca2+ release triggered by NAADP in hepatocyte microsomes

2006 ◽  
Vol 395 (2) ◽  
pp. 233-238 ◽  
Author(s):  
Miklós Mándi ◽  
Balázs Tóth ◽  
György Timár ◽  
Judit Bak
Keyword(s):  
Nicotinic Acid ◽  
Ryanodine Receptor ◽  
Sea Urchin ◽  
Mammalian Cells ◽  
Liver Microsomes ◽  
The Other ◽  
Release Mechanism ◽  
Ip3 Receptors ◽  
Rat Hepatocyte ◽  
Inositol 1,4,5 Trisphosphate

NAADP (nicotinic acid–adenine dinucleotide phosphate) is fast emerging as a new intracellular Ca2+-mobilizing messenger. NAADP induces Ca2+ release by a mechanism that is distinct from IP3 (inositol 1,4,5-trisphosphate)- and cADPR (cADP-ribose)-induced Ca2+ release. In the present study, we demonstrated that micromolar concentrations of NAADP trigger Ca2+ release from rat hepatocyte microsomes. Cross-desensitization to IP3 and cADPR by NAADP did not occur in liver microsomes. We report that non-activating concentrations of NAADP can fully inactivate the NAADP-sensitive Ca2+-release mechanism in hepatocyte microsomes. The ability of thapsigargin to block the NAADP-sensitive Ca2+ release is not observed in sea-urchin eggs or in intact mammalian cells. In contrast with the Ca2+ release induced by IP3 and cADPR, the Ca2+ release induced by NAADP was completely independent of the free extravesicular Ca2+ concentration and pH (in the range 6.4–7.8). The NAADP-elicited Ca2+ release cannot be blocked by the inhibitors of the IP3 receptors and the ryanodine receptor. On the other hand, verapamil and diltiazem do inhibit the NAADP- (but not IP3- or cADPR-) induced Ca2+ release.

Regulation of inositol 1,4,5-trisphosphate receptors

1993 ◽  
Vol 184 (1) ◽  
pp. 161-182 ◽  
Author(s):  
I. C. Marshall ◽  
C. W. Taylor
Keyword(s):  
Splice Variants ◽  
Divalent Cations ◽  
Cell Types ◽  
Smooth Muscle Contraction ◽  
Receptor Activation ◽  
Receptor Subtypes ◽  
Inositol 1,4,5 Trisphosphate ◽  
Specific Receptors ◽  
Rapid Generation ◽  
Allosteric Regulators

Inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] is a soluble second messenger responsible for the generation of highly organized Ca2+ signals in a variety of cell types. These Ca2+ signals control many cellular responses, including cell growth, fertilization, smooth muscle contraction and secretion. Ins(1,4,5)P3 is produced at the plasma membrane following receptor activation, but rapidly diffuses into the cytosol, where it binds to specific receptors through which it mobilizes intracellular Ca2+ stores. The actions of Ins(1,4,5)P3 within cells are tightly controlled: enzymes control the rapid generation and metabolism of Ins(1,4,5)P3 following receptor activation; multiple Ins(1,4,5)P3 receptor subtypes and splice variants exist, some of which are differentially expressed between cell types and at different stages of development; and Ins(1,4,5)P3 receptors are the targets for a number of allosteric regulators, including protein kinases, ATP and divalent cations. Understanding how cells control the Ca(2+)-mobilizing activity of Ins(1,4,5)P3 will be important if we are to unravel the mechanisms that underlie the complex arrangements of Ca2+ signals.

scholarly journals Designer small molecules to target calcium signalling

2015 ◽  
Vol 43 (3) ◽  
pp. 417-425 ◽  
Author(s):  
Joanna M. Swarbrick ◽  
Andrew M. Riley ◽  
Stephen J. Mills ◽  
Barry V.L. Potter
Keyword(s):  
Nicotinic Acid ◽  
Small Molecules ◽  
Conformational Changes ◽  
Transient Receptor Potential ◽  
Therapeutic Potential ◽  
Receptor Activation ◽  
Synthetic Analogues ◽  
Binding Model ◽  
Transient Receptor Potential Melastatin ◽  
Inositol 1,4,5 Trisphosphate

Synthetic compounds open up new avenues to interrogate and manipulate intracellular Ca2+ signalling pathways. They may ultimately lead to drug-like analogues to intervene in disease. Recent advances in chemical biology tools available to probe Ca2+ signalling are described, with a particular focus on those synthetic analogues from our group that have enhanced biological understanding or represent a step towards more drug-like molecules. Adenophostin (AdA) is the most potent known agonist at the inositol 1,4,5-trisphosphate receptor (IP3R) and synthetic analogues provide a binding model for receptor activation and channel opening. 2-O-Modified inositol 1,4,5-trisphosphate (IP3) derivatives that are partial agonists at the IP3R reveal key conformational changes of the receptor upon ligand binding. Biphenyl polyphosphates illustrate that simple non-inositol surrogates can be engineered to give prototype IP3R agonists or antagonists and act as templates for protein co-crystallization. Cyclic adenosine 5′-diphosphoribose (cADPR) can be selectively modified using total synthesis, generating chemically and biologically stable tools to investigate Ca2+ release via the ryanodine receptor (RyR) and to interfere with cADPR synthesis and degradation. The first neutral analogues with a synthetic pyrophosphate bioisostere surprisingly retain the ability to release Ca2+, suggesting a new route to membrane-permeant tools. Adenosine 5′-diphosphoribose (ADPR) activates the Ca2+-, Na+- and K+-permeable transient receptor potential melastatin 2 (TRPM2) cation channel. Synthetic ADPR analogues provide the first structure-activity relationship (SAR) for this emerging messenger and the first functional antagonists. An analogue based on the nicotinic acid motif of nicotinic acid adenine dinucleotide phosphate (NAADP) antagonizes NAADP-mediated Ca2+ release in vitro and is effective in vivo against induced heart arrhythmia and autoimmune disease, illustrating the therapeutic potential of targeted small molecules.

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 Differential regulation of nicotinic acid–adenine dinucleotide phosphate and cADP-ribose production by cAMP and cGMP

1998 ◽  
Vol 331 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Heather L. WILSON ◽  
Antony GALIONE
Keyword(s):  
Nicotinic Acid ◽  
Sea Urchin ◽  
Calcium Release ◽  
Second Messengers ◽  
Differential Regulation ◽  
Sea Urchin Egg ◽  
Inositol 1,4,5 Trisphosphate ◽  
Extracellular Stimuli ◽  
Camp And Cgmp ◽  
Temperature Optima

The sea urchin egg has been used as a system to study calcium-release mechanisms induced by inositol 1,4,5-trisphosphate (IP3), cADP-ribose (cADPR), and more recently, nicotinic acid–adenine dinucleotide phosphate (NAADP). In order that cADPR and NAADP may be established as endogenous messengers for calcium release, the existence of intracellular enzymes capable of metabolizing these molecules must be demonstrated. In addition, intracellular levels of cADPR and NAADP should be under the control of extracellular stimuli. It has been shown that cGMP stimulates the synthesis of cADPR in the sea urchin egg. The present study shows that the sea urchin egg is capable of synthesizing and degrading NAADP. cADPR and NAADP synthetic activities appear to be separate, with different cellular localizations, pH and temperature optima. We suggest that in the sea urchin egg, cADPR and NAADP production may be differentially regulated by receptor-coupled second messengers, with cADPR production being regulated by cGMP and NAADP production modulated by cAMP.

scholarly journals The lifetime of inositol 1,4,5-trisphosphate in single cells.

1995 ◽  
Vol 105 (1) ◽  
pp. 149-171 ◽  
Author(s):  
S S Wang ◽  
A A Alousi ◽  
S H Thompson
Keyword(s):  
Single Cells ◽  
Neuroblastoma Cells ◽  
Threshold Level ◽  
Cell Types ◽  
Time Frame ◽  
Receptor Activation ◽  
Eukaryotic Cell ◽  
Muscarinic Agonist ◽  
Ip3 Receptors ◽  
Inositol 1,4,5 Trisphosphate

In many eukaryotic cell types, receptor activation leads to the formation of inositol 1,4,5-trisphosphate (IP3) which causes calcium ions (Ca) to be released from internal stores. Ca release was observed in response to the muscarinic agonist carbachol by fura-2 imaging of N1E-115 neuroblastoma cells. Ca release followed receptor activation after a latency of 0.4 to 20 s. Latency was not caused by Ca feedback on IP3 receptors, but rather by IP3 accumulation to a threshold for release. The dependence of latency on carbachol dose was fitted to a model in which IP3 synthesis and degradation compete, resulting in gradual accumulation to a threshold level at which Ca release becomes regenerative. This analysis gave degradation rate constants of IP3 in single cells ranging from 0 to 0.284 s-1 (0.058 +/- 0.067 s-1 SD, 53 cells) and a mean IP3 lifetime of 9.2 +/- 2.2 s. IP3 degradation was also measured directly with biochemical methods. This gave a half life of 9 +/- 2 s. The rate of IP3 degradation sets the time frame over which IP3 accumulations are integrated as input signals. IP3 levels are also filtered over time, and on average, large-amplitude oscillations in IP3 in these cells cannot occur with period < 10 s.

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 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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