Nicotinic Acid Adenine Dinucleotide Phosphate (Naadp+) Is an Essential Regulator of T-Lymphocyte Ca2+-Signaling

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Abstract
Microinjection of human Jurkat T-lymphocytes with nicotinic acid adenine dinucleotide phosphate (NAADP+) dose-dependently stimulated intracellular Ca2+-signaling. At a concentration of 10 nM NAADP+ evoked repetitive and long-lasting Ca2+-oscillations of low amplitude, whereas at 50 and 100 nM, a rapid and high initial Ca2+-peak followed by trains of smaller Ca2+-oscillations was observed. Higher concentrations of NAADP+ (1 and 10 μM) gradually reduced the initial Ca2+-peak, and a complete self-inactivation of Ca2+-signals was seen at 100 μM. The effect of NAADP+ was specific as it was not observed with nicotinamide adenine dinucleotide phosphate. Both inositol 1,4,5-trisphosphate– and cyclic adenosine diphosphoribose–mediated Ca2+-signaling were efficiently inhibited by coinjection of a self-inactivating concentration of NAADP+. Most importantly, microinjection of a self-inactivating concentration of NAADP+ completely abolished subsequent stimulation of Ca2+-signaling via the T cell receptor/CD3 complex, indicating that a functional NAADP+ Ca2+-release system is essential for T-lymphocyte Ca2+-signaling.

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