The emerging central role of NAD+ in cell signaling demonstrates the importance of characterizing and determining the regulatory mechanisms of the enzymes involved in NAD+ catabolism, such as ADP-ribosyl cyclases. Specifically, we are interested in mammalian CD38 and the parasitic homologue, SmNACE.
CD38 is a multifunctional enzyme that catalyzes the conversion of NAD(P)+ to three metabolites (cyclic ADP-ribose, NAADP+ and ADP-ribose), which are involved in the mobilization of cellular calcium. We combined x-ray crystallography, molecular modeling and enzymatic measurements on recombinant CD38 active site mutants to determine its catalytic mechanism. Currently, there are no selective, potent inhibitors available for mammalian CD38. One of our goals is to develop a mammalian CD38 inhibitor, which will enable the study of its roles in the molecular signaling processes.
SmNACE (Schistosoma mansoni NAD+ catabolizing enzyme) is the parasitic homolog of CD38. Schistosomiasis is a neglected tropical disease affecting ~200 million people worldwide, and 80% of the cases occur in sub-Saharan Africa. More than 200 000 people die every year. It ranks second – following malaria – in the world’s parasitic diseases in terms of prevalence, morbidity and mortality rates. Currently the therapeutic options to treat schistosomiasis are very limited: PZQ is used almost exclusively and is on the WHO’s model list of essential drugs. However the wide-spread use and reliance on one drug to treat this disease has raised fears of the selection of PZQ-resistant schistosomes. One promising novel drug target is SmNACE which is located on the outer tegument of the adult parasite, and can potentially modulate NAD+ dependent pathways of the host’s immune system.
We developed a sensitive and robust fluorometric high-throughput screening assay to identify SmNACE inhibitors. We screened a highly diverse academic chemical library of 14,300 molecules. Moreover, structural studies by molecular modeling allowed a virtual screening of 1800000 molecules. We identified 3 natural product inhibitors of SmNACE with IC(50) values in the low micromolar range : cyanidin and delphinidin, (high throughput screening hits) and taxifolin (virtual screening hit). A further 15 additional natural product inhibitors were identified while determining the structure-activity relationship. This novel class of inhibitors will be valuable as new pharmacological tools and in drug development.
The future work will be focused on the rational design of a new generation of inhibitors and the validation of SmNACE as a target for the schistosomiasis.
CD38 is a multifunctional enzyme that catalyzes the conversion of NAD(P)+ to three metabolites (cyclic ADP-ribose, NAADP+ and ADP-ribose), which are involved in the mobilization of cellular calcium. We combined x-ray crystallography, molecular modeling and enzymatic measurements on recombinant CD38 active site mutants to determine its catalytic mechanism. Currently, there are no selective, potent inhibitors available for mammalian CD38. One of our goals is to develop a mammalian CD38 inhibitor, which will enable the study of its roles in the molecular signaling processes.
SmNACE (Schistosoma mansoni NAD+ catabolizing enzyme) is the parasitic homolog of CD38. Schistosomiasis is a neglected tropical disease affecting ~200 million people worldwide, and 80% of the cases occur in sub-Saharan Africa. More than 200 000 people die every year. It ranks second – following malaria – in the world’s parasitic diseases in terms of prevalence, morbidity and mortality rates. Currently the therapeutic options to treat schistosomiasis are very limited: PZQ is used almost exclusively and is on the WHO’s model list of essential drugs. However the wide-spread use and reliance on one drug to treat this disease has raised fears of the selection of PZQ-resistant schistosomes. One promising novel drug target is SmNACE which is located on the outer tegument of the adult parasite, and can potentially modulate NAD+ dependent pathways of the host’s immune system.
We developed a sensitive and robust fluorometric high-throughput screening assay to identify SmNACE inhibitors. We screened a highly diverse academic chemical library of 14,300 molecules. Moreover, structural studies by molecular modeling allowed a virtual screening of 1800000 molecules. We identified 3 natural product inhibitors of SmNACE with IC(50) values in the low micromolar range : cyanidin and delphinidin, (high throughput screening hits) and taxifolin (virtual screening hit). A further 15 additional natural product inhibitors were identified while determining the structure-activity relationship. This novel class of inhibitors will be valuable as new pharmacological tools and in drug development.
The future work will be focused on the rational design of a new generation of inhibitors and the validation of SmNACE as a target for the schistosomiasis.
Michalis complex of ribo-F-NAD+ in the active site of bovine CD38