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Biological Research

versión impresa ISSN 0716-9760

Biol. Res. v.37 n.4 Santiago  2004 


Biol Res 37: 559-563, 2004 R


To be or not to be… Nicotinic acid adenine dinucleotide phosphate (NAADP): A new intracellular second messenger?


Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota, 55905 USA

Dirección para Correspondencia



Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent activator of intracellular Ca2+ release in several vertebrate and invertebrate systems. The role of the NAADP system in physiological processes is being extensively investigated at the present time. The NAADP receptor and its associated Ca2+ pool have been hypothesized to be important in several physiological processes including fertilization, T cell activation, and pancreatic secretion. However, whether NAADP is a new second messenger or a tool for the discovery of a new Ca2+ channel is still an unanswered question. Research developed over the last two years has provided some important clues to whether NAADP is or not a physiological cellular messenger. In this short review, I will discuss some of these new findings that are helping us to find an answer to the important question: Is NAADP a second messenger or not?

Key words: NAADP, Ca2+, channels, cADPR, intracellular, second messenger



The discovery of intracellular second messengers represented a major step in understanding how extracellular signals are capable of regulating cellular behavior (5). In this regard, the release of intracellular calcium ions (Ca2+) plays a fundamental role in cell signaling (5; see also Carafoli, this issue, reference 7). Release of Ca2+ from intracellular stores, such as the endoplasmic and sarcoplasmic reticulum, is a key component in several intracellular signaling pathways (5).

Recently, we and others have found that the nucleotide nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent activator of intracellular Ca2+ release (10, 24). This nucleotide activates an intracellular Ca2+ release mechanism that differs in many ways from that modulated by both IP3 and cADPR (9-10, 12, 14-16, 18, 20-25). In contrast to IP3 and cADPR, the research on NAADP is only in its infancy, and further experimentation is needed to determine the precise role of this Ca2+-releasing pathway in cell signaling. In this review, I discuss several aspects of NAADP research and analyze some of the recent data that indicates that NAAADP may be an intracellular second messenger.


NAADP has a molecular mass only 1 Da larger than b_NADP (Fig. 1) (10, 12, 24). The difference between the molecule of NAADP and NADP is the change of an NH2 of the amide in NADP to OH of the carboxyl group in NAADP (10, 12, 24). With this substitution NADP is transformed into one of the most potent activators of intracellular Ca2+ release known to mankind (10, 12, 24) (Fig. 1).


Figure 1. Base-exchange reaction: The nicotinamide group of nicotinamide adenine dinucleotide phosphate (NADP+) is exchanged for nicotinic acid, resulting in nicotinic acid adenine dinucleotide phosphate (NAADP).

The structural requirements of the NAADP-induced Ca2+ release system appear to be very stringent, because several structural analogs of NAADP have no effect on intracellular Ca2+ release (5, 12). Of particular interest, the phosphate in position 2' is crucial for the biological activity of NAADP, because NAAD has no Ca2+-mobilizing property (5, 12). However, changing the position of the third phosphate from 2' to 3' has no effect on the Ca2+-releasing properties of the molecule (5, 12). In fact, whether the third phosphate is in position 2' or 3' or whether it is cyclic on positions 2' and 3' does not change the Ca2+-mobilizing properties of this nucleotide (5, 12).


The mechanism of Ca2+ release elicited by NAADP was initially characterized in sea urchin eggs (5-12). In initial studies, the most striking feature of NAADP was its ability to induce Ca2+ release even after IP3 and ryanodine channels had been desensitized previously (10, 24). This behavior suggests that another Ca2+ release mechanism, possibly a new Ca2+ channel, is involved in NAADP-mediated Ca2+ release. Several lines of evidence support this notion, including: 1) antagonists of ryanodine and IP3 channels were ineffective in blocking NAADP-mediated Ca2+ release (10); 2) known modulators of ryanodine and IP3 channels—such as Ca2+, Mg2+, caffeine, ryanodine, ruthenium red, and procaine—as well as pH did not influence NAADP-mediated Ca2+ release (10, 12); and 3) L-type Ca2+ channel antagonists could inhibit NAADP-induced Ca2+ release but not IP3-induced Ca2+ release or CICR (21-22). Together, these findings revealed a distinct pharmacological behavior of the NAADP Ca2+ release system of sea urchin eggs, further strengthening the hypothesis that NAADP is an activator of a novel Ca2+ release system.

In recent years, we and others have observed that several cells from vertebrates and invertebrates are responsive to NAADP (2-4, 8-10, 12, 14-16, 18, 20-25, 28-32). Furthermore, NAADP has been implicated in several physiological processes, including among other processes, fertilization, pancreatic secretion and T-lymphocyte activation (8, 19, 31, 4).

The molecular identity of the NAADP receptor is still obscure. Nevertheless, specific binding of radioactive NAADP has been described in sea urchin eggs (29) and in rat brain with autoradiographic techniques (30). A single and saturable binding site was more thoroughly characterized in sea urchin egg (23, 29). Ca2+ and pH did not affect NAADP binding, which probably explains why Ca2+ and pH do not influence NAADP-induced Ca2+ release in sea urchin eggs. More importantly, NAADP binding seemed to be irreversible (23, 29), suggesting an explanation for the molecular basis of the inactivation phenomenon observed with subthreshold concentrations of NAADP. Ongoing work from several laboratories will surely very soon provide us with the anxiously anticipated structure of the NAADP receptor.


This is one of the most important questions that we face at this time on this new field of research. Synthesis of NAADP has been previously described in several tissues including brain, liver, spleen, heart, and kidney glomeruli. Synthesis of NAADP can be catalyzed in vitro by a NAD(P)ase, analogous to the lymphocyte antigen CD38 (1, 11, 13, 26), in a reaction called the base-exchange reaction (Fig.1). The enzyme catalyzes the exchange of nicotinamide for nicotinic acid on the molecule of NADP+, generating NAADP (Fig.1, 1, 11, 13, 26). Whether NAADP can be generated via the base-exchange reaction in vivo is still an open question. Under the present experimental conditions used for synthesis of NAADP, the concentrations of substrate needed, namely nicotinic acid, are several times higher than would be expected to be present in intact cells (1, 11, 13, 26). Furthermore, the optimal pH for this reaction is out of the physiological range (1, 11, 13, 26). However, compartmentalization of nicotinic acid and NADP into an acid environment could theoretically provide a possible milieu for the synthesis of NAADP in vivo. Another theoretical problem is the fact that in mammalian cells, the base-exchange reaction seems to be catalyzed by CD38, which is an ectoenzyme. This feature, therefore, raises the question of how substrates would be available to the CD38 catalytic site and, once NAADP is generated, how it would be made available in the cytosol to induce Ca2+ release.

Despite the limitations discussed, the base-exchange reaction is the only pathway currently described for the synthesis of NAADP in biological systems (1, 11, 13, 26). However, as discussed above, whether the base-exchange reaction occurs under physiological conditions is still an open question. Using CD38 knockout mice, we determined that CD38 is the major enzyme responsible for the base-exchange reaction in mouse tissue (11). In our experiments, however, we performed in vitro synthesis of NAADP, and we did not measure intracellular levels of NAADP. Recent work from our laboratory using a method designed to detect in vivo levels of NAADP indicates that CD38 may not be the enzyme responsible for the synthesis of NAADP in vivo. Furthermore, our recent data also indicate that the base-exchange reaction may not be the physiological pathway for the synthesis of NAADP.


In a recent review we have proposed that several requirements had to be fulfilled before NAADP could be considered an intracellular messenger (12). These include:

1) NAADP levels must be determined in cells.
2) The physiological pathways for the synthesis of NAADP must be defined.
3) The concentration of intracellular NAADP must be regulated by external or internal stimuli.
4) A correlation between stimulated intracellular NAADP levels and Ca2+ release must be established.

We then concluded our review describing that at that time none of these requirements had been demonstrated for NAADP (12). Very recent data, however, has indicated that NAADP may be a second messenger. In 2003 an NAADP-like molecule present in both invertebrate and mammalian cells was described for the first time (19, 27). Furthermore, it was also found that the intracellular levels of the NAADP-like molecule were modulated by extracellular stimulus (19, 27), indicating that NAADP is present in cells and that its synthesis or mobilization is regulated. These data strongly indicate that NAADP is indeed a second messenger. However, several other questions are still unanswered. In fact, as discussed above, the pathway for the synthesis of NAADP has not been elucidated. Whether intracellular generated NAADP can regulate cellular functions has not been demonstrated either, and finally, the structure of the NAADP receptor has not been reported. However, several laboratories are working as "we speak" on these important questions, and I believe that the missing pieces of the NAADP puzzle are very close to clarification. Certainly, the future holds new and exciting discoveries in this field.


We acknowledge the excellent secretarial assistance provided by Lea Dacy, and for the excellent technical assistance of Mr. Michael Thompson. The Mayo Foundation and the Federation for Anesthesia Research (FAER) supported my research.


1 AARHUS R, GRAEFF RM, DICKEY DM, WALSETH TF, LEE HC (1995) ADP-ribosyl cyclase and CD38 catalyze the synthesis of a calcium-mobilizing metabolite from NADP. J Biol Chem 270: 30327-30333

2 BAK, J, BILLINGTON RA, TIMAR G, DUTTON AC, GENAZZANI AA (2001) NAADP receptors are present and functional in the heart. Curr Biol 11: 987-990

3 BAK J, WHITE P, TIMAR G, MISSIAEN L, GENAZZANI AA, GALIONE A (1999) Nicotinic acid adenine dinucleotide phosphate triggers Ca2+ release from brain microsomes. Curr Biol 9: 751-754

4 BERG I, POTTER BVL, MAYR GW, GUSE A (2000) Nicotinic acid adenine dinucleotide phosphate (NAADP+) is an essential regulator of T-lymphocyte Ca2+-signaling. J Cell Biol 150: 581-588

5 BERRIDGE MJ, LIPP P, BOOTMAN MD (2000) The versatility and universality of calcium signalling. Nat Rev Mol Cell Biol 1: 11-21 6 BILLINGTON RA, GENAZZANI AA (2000) Characterization of NAADP+ binding in sea urchin eggs. Biochem Biophys Res Commun 276: 112-116

7 CARAFOLI E (2004) Calcium signaling: An historical account. Biol Res 37: in this issue

8 CANCELA JM, CHURCHILL GC, GALIONE A (1999) Coordination of agonist-induced Ca2+-signalling patterns by NAADP in pancreatic acinar cells. Nature 398: 74-76

9 CHINI EN, BEERS KW, CHINI CC, DOUSA TP (1995) Specific modulation of cyclic-ADP ribose-induced Ca2+ release by polyamines. Am J Physiol Cell Physiol 269: C1042-C1047

10 CHINI EN, BEERS KW, DOUSA TP (1995) Nicotinate adenine dinucleotide phosphate (NAADP) triggers a specific calcium release system in sea urchin eggs. J Biol Chem 270: 3216-3223

11 CHINI, EN, CHINI CS, KATO I, TAKASAWA S, OKAMOTO H (2002) CD38 is the major enzyme responsible for the synthesis of NAADP in mammalian tissues. Biochem J 362: 125-130

12 CHINI EN, DE TOLEDO FG (2002) Nicotinic acid adenine dinucleotide phosphate: A new intracellular second messenger? Am J Physiol 282: C1191-C1198

13 CHINI EN, DOUSA TP (1995) Enzymatic synthesis and degradation of nicotinate adenine dinucleotide phosphate (NAADP), a Ca2+-releasing agonist, in rat tissues. Biochem Biophys Res Commun 205: 167-174

14 CHINI EN, DOUSA TP (1996) Nicotinate-adenine dinucleotide phosphate-induced Ca2+-release does not behave as a Ca2+-induced Ca2+-release system. Biochem J 316: 709-711

15 CHINI EN, DOUSA TP (1996) Palmitoyl-CoA potentiates the Ca2+ release elicited by cyclic ADP-ribose. Am J Physiol Cell Physiol 270: C530-C537

16 CHINI EN, LIANG MY, DOUSA TP (1998) Differential effect of pH upon cyclic-ADP-ribose and nicotinate-adenine dinucleotide phosphate-induced Ca2+ release systems. Biochem J 335: 499-504

17 CHINI EN, THOMPSON MA, DOUSA TP (1996) Enzymatic synthesis of NAADP by ADP-ribosyl cyclases. (Abstract) FASEB J 10: A143

18 CHENG JF, YUSUFI ANK, THOMPSON MA, CHINI EN, GRANDE JP (2001) Nicotinic acid adenine dinucleotide phosphate: A new Ca2+ releasing agent in kidney. J Am Soc Nephrol 12: 54-60

19 CHURCHILL GC, ONEILL JS, MASGRAU R, PATEL S, THOMAS JM, GENAZZANI AA, GALIONE A (2003) Sperm deliver a new second messenger: NAADP. Curr Biol 13: 125-128

20 GALIONE A, PATEL S, CHURCHILL GC (2000) NAADP-induced calcium release in sea urchin eggs. Biol Cell 92: 197-204

21 GENAZZANI AA, GALIONE A (1997) A Ca2+ release mechanism gated by the novel pyridine nucleotide, NAADP. Trends Pharmacol Sci 18: 108-110

22 GENAZZANI AA, GALIONE A (1996) Nicotinic acid-adenine dinucleotide phosphate mobilizes Ca2+ from a thapsigargin-insensitive pool. Biochem J 315: 721-725

23 GENAZZANI AA, MEZNA M, DICKEY DM, MICHELANGELI F, WALSETH TF, GALIONE A (1997) Pharmacological properties of the Ca2+-release mechanism sensitive to NAADP in the sea urchin egg. Br J Pharmacol 121: 1489-14953

24 LEE HC, AARHUS R (1995) A derivative of NADP mobilizes calcium stores insensitive to inositol trisphosphate and cyclic ADP-ribose. J Biol Chem 270: 2152-2157

25 LEE, HC (1997) Mechanisms of calcium signaling by cyclic ADP-ribose and NAADP. Physiol Rev 77: 1133-1164

27 MASGRAU R, CHURCHILL GC, MORGAN AJ, ASHCROFT SJ, GALIONE A (2003) NAADP: A new second messenger for glucose-induced Ca(2+) responses in clonal pancreatic beta cells. Curr Biol 13: 247-251

28 PATEL S, CHURCHILL GC, GALIONE A (2001) Coordination of Ca2+ signaling by NAADP. Trends Biochem Sci 26: 482-489

29 PATEL S, CHURCHILL GC, GALIONE A (2000) Unique kinetics of nicotinic acid-adenine dinucleotide phosphate (NAADP) binding enhance the sensitivity of NAADP receptors for their ligand. Biochem J 352: 725-729 30 PATEL S, CHURCHILL GC, SHARP T, GALIONE A (2000) Widespread distribution of binding sites for the novel Ca2+-mobilizing messenger, nicotinic acid adenine dinucleotide phosphate, in the brain. J Biol Chem 275: 36495-36497

31 PÉREZ-TERZIC CM, CHINI EN, SHEN SS, DOUSA TP, CLAPHAM DE (1995) Ca2+ release triggered by nicotinate adenine dinucleotide phosphate in intact sea urchin eggs. Biochem J 312: 955-959

32 YUSUFI, ANK, CHENG JF, THOMPSON MA, CHINI EN, GRANDE JP (2001) Nicotinic acid-adenine dinucleotide phosphate (NAADP) elicits specific microsomal Ca2+ release from mammalian cells. Biochem J 353: 531-536


Corresponding author: E. N. Chini, Dept. of Anesthesiology Mayo Clinic and Foundation 200 First St., Rochester, MN, 55905 USA. Phone: (1-507) 255-0992, Fax: (1-507) 284-8566, E-mail:

Received: January 16, 2004. Accepted: March 8, 2004.


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