CD38-NADase is a new major contributor to Duchenne muscular dystrophic phenotype.

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration. Two important deleterious features are a Ca2+ dysregulation linked to Ca2+ influxes associated with ryanodine receptor hyperactivation, and a muscular nicotinamide adenine dinucleotide (NAD+ ) deficit. Here, we identified that deletion in mdx mice of CD38, a NAD+ glycohydrolase-producing modulators of Ca2+ signaling, led to a fully restored heart function and structure, with skeletal muscle performance improvements, associated with a reduction in inflammation and senescence markers. Muscle NAD+ levels were also fully restored, while the levels of the two main products of CD38, nicotinamide and ADP-ribose, were reduced, in heart, diaphragm, and limb. In cardiomyocytes from mdx/CD38-/- mice, the pathological spontaneous Ca2+ activity was reduced, as well as in myotubes from DMD patients treated with isatuximab (SARCLISA® ) a monoclonal anti-CD38 antibody. Finally, treatment of mdx and utrophin-dystrophin-deficient (mdx/utr-/- ) mice with CD38 inhibitors resulted in improved skeletal muscle performances. Thus, we demonstrate that CD38 actively contributes to DMD physiopathology. We propose that a selective anti-CD38 therapeutic intervention could be highly relevant to develop for DMD patients.

A multiscale analysis in CD38-/- mice unveils major prefrontal cortex dysfunctions.

Autism spectrum disorder (ASD) is characterized by early onset of behavioral and cognitive alterations. Low plasma levels of oxytocin (OT) have also been found in ASD patients; recently, a critical role for the enzyme CD38 in the regulation of OT release was demonstrated. CD38 is important in regulating several Ca2+-dependent pathways, but beyond its role in regulating OT secretion, it is not known whether a deficit in CD38 expression leads to functional modifications of the prefrontal cortex (PFC), a structure involved in social behavior. Here, we report that CD38-/- male mice show an abnormal cortex development, an excitation-inhibition balance shifted toward a higher excitation, and impaired synaptic plasticity in the PFC such as those observed in various mouse models of ASD. We also show that a lack of CD38 alters social behavior and emotional responses. Finally, examining neuromodulators known to control behavioral flexibility, we found elevated monoamine levels in the PFC of CD38-/- adult mice. Overall, our study unveiled major changes in PFC physiologic mechanisms and provides new evidence that the CD38-/- mouse could be a relevant model to study pathophysiological brain mechanisms of mental disorders such as ASD.-Martucci, L. L., Amar, M., Chaussenot, R., Benet, G., Bauer, O., de Zélicourt, A., Nosjean, A., Launay, J.-M., Callebert, J., Sebrié, C., Galione, A., Edeline, J.-M., de la Porte, S., Fossier, P., Granon, S., Vaillend, C., Cancela, J.-M., A multiscale analysis in CD38-/- mice unveils major prefrontal cortex dysfunctions.

The ecto-enzyme CD38 is a nicotinic acid adenine dinucleotide phosphate (NAADP) synthase that couples receptor activation to Ca2+ mobilization from lysosomes in pancreatic acinar cells.

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca(2+)-mobilizing intracellular messenger and is linked to a variety of stimuli and cell surface receptors. However, the enzyme responsible for endogenous NAADP synthesis in vivo is unknown, and it has been proposed that another enzyme differing from ADP-ribosyl cyclase family members may exist. The ecto-enzyme CD38, involved in many functions as diverse as cell proliferation and social behavior, represents an important alternative. In pancreatic acinar cells, the hormone cholecystokinin (CCK) stimulates NAADP production evoking Ca(2+) signals by discharging acidic Ca(2+) stores and leading to digestive enzyme secretion. From cells derived from CD38(-/-) mice, we provide the first physiological evidence that CD38 is required for endogenous NAADP generation in response to CCK stimulation. Furthermore, CD38 expression in CD38-deficient pancreatic AR42J cells remodels Ca(2+)-signaling pathways in these cells by restoring Ca(2+) mobilization from lysosomes during CCK-induced Ca(2+) signaling. In agreement with an intracellular site for messenger synthesis, we found that CD38 is expressed in endosomes. These CD38-containing vesicles, likely of endosomal origin, appear to be proximal to lysosomes but not co-localized with them. We propose that CD38 is an NAADP synthase required for coupling receptor activation to NAADP-mediated Ca(2+) release from lysosomal stores in pancreatic acinar cells.

Regulation of nuclear Ca2+ signaling by translocation of the Ca2+ messenger synthesizing enzyme ADP-ribosyl cyclase during neuronal depolarization.

In neurons, voltage-gated Ca(2+) channels and nuclear Ca(2+) signaling play important roles, such as in the regulation of gene expression. However, the link between electrical activity and biochemical cascade activation involved in the generation of the nuclear Ca(2+) signaling is poorly understood. Here we show that depolarization of Aplysia neurons induces the translocation of ADP-ribosyl cyclase, a Ca(2+) messenger synthesizing enzyme, from the cytosol into the nucleus. The translocation is dependent on Ca(2+) influx mainly through the voltage-dependent L-type Ca(2+) channels. We report also that specific nucleoplasmic Ca(2+) signals can be induced by three different calcium messengers, cyclic ADP-ribose, nicotinic acid adenine dinucleotide phosphate (NAADP), both produced by the ADP-ribosyl cyclase, and inositol 1,4,5-trisphosphate (IP(3)). Moreover, our pharmacological data show that NAADP acts on its own receptor, which cooperates with the IP(3) and the ryanodine receptors to generate nucleoplasmic Ca(2+) oscillations. We propose a new model where voltage-dependent L-type Ca(2+) channel-induced nuclear translocation of the cytosolic cyclase is a crucial step in the fine tuning of nuclear Ca(2+) signals in neurons.

Generation of specific Ca(2+) signals from Ca(2+) stores and endocytosis by differential coupling to messengers.

It remains unclear how different intracellular stores could interact and be recruited by Ca(2+)-releasing messengers to generate agonist-specific Ca(2+) signatures. In addition, refilling of acidic stores such as lysosomes and secretory granules occurs through endocytosis, but this has never been investigated with regard to specific Ca(2+) signatures. In pancreatic acinar cells, acetylcholine (ACh), cholecystokinin (CCK), and the messengers cyclic ADP-ribose (cADPR), nicotinic acid adenine dinucleotide phosphate (NAADP), and inositol 1,4,5-trisphosphate (IP(3)) evoke repetitive local Ca(2+) spikes in the apical pole. Our work reveals that local Ca(2+) spikes evoked by different agonists all require interaction of acid Ca(2+) stores and the endoplasmic reticulum (ER), but in different proportions. CCK and ACh recruit Ca(2+) from lysosomes and from zymogen granules through different mechanisms; CCK uses NAADP and cADPR, respectively, and ACh uses Ca(2+) and IP(3), respectively. Here, we provide pharmacological evidence demonstrating that endocytosis is crucial for the generation of repetitive local Ca(2+) spikes evoked by the agonists and by NAADP and IP(3). We find that cADPR-evoked repetitive local Ca(2+) spikes are particularly dependent on the ER. We propose that multiple Ca(2+)-releasing messengers determine specific agonist-elicited Ca(2+) signatures by controlling the balance among different acidic Ca(2+) stores, endocytosis, and the ER.

Role of NAADP and cADPR in the induction and maintenance of agonist-evoked Ca2+ spiking in mouse pancreatic acinar cells.

Nicotinic acid adenine dinucleotide phosphate (NAADP) and cyclic adenosine diphosphate ribose (cADPR) were first demonstrated to mobilize Ca2+ in sea urchin eggs. In the absence of direct measurements of these messengers, pharmacological studies alone have implicated these molecules as intracellular second messengers for specific cell surface receptor agonists. We now report that in mouse pancreatic acinar cells, cholecystokinin, but not acetylcholine, evokes rapid and transient increases in NAADP levels in a concentration-dependent manner. In contrast, both cholecystokinin and acetylcholine-mediated production of cADPR followed a very different time course. The rapid and transient production of NAADP evoked by cholecystokinin precedes the onset of the Ca2+ signal and is consistent with a role for NAADP in the initiation of the Ca2+ response. Continued agonist-evoked Ca2+ spiking is maintained by prolonged elevations of cADPR levels through sensitization of Ca2+ -induced Ca2+ -release channels. This study represents the first direct comparison of NAADP and cADPR measurements, and the profound differences observed in their time courses provide evidence in support of distinct roles of these Ca2+ -mobilizing messengers in shaping specific Ca2+ signals during agonist stimulation.