Asunto(s)
Anticuerpos Antivirales/inmunología , Anticuerpos Antivirales/uso terapéutico , Betacoronavirus/inmunología , Infecciones por Coronavirus/tratamiento farmacológico , Infecciones por Coronavirus/economía , Costos de los Medicamentos , Pandemias/economía , Neumonía Viral/tratamiento farmacológico , Neumonía Viral/economía , Administración por Inhalación , Animales , Anticuerpos Antivirales/administración & dosificación , Anticuerpos Antivirales/economía , Betacoronavirus/genética , COVID-19 , Camélidos del Nuevo Mundo/inmunología , Infecciones por Coronavirus/inmunología , Infecciones por Coronavirus/prevención & control , Fiebre Hemorrágica Ebola/tratamiento farmacológico , Fiebre Hemorrágica Ebola/inmunología , Fiebre Hemorrágica Ebola/prevención & control , Humanos , Evasión Inmune/genética , Pandemias/prevención & control , Neumonía Viral/inmunología , Neumonía Viral/prevención & control , SARS-CoV-2 , Anticuerpos de Dominio Único/administración & dosificación , Anticuerpos de Dominio Único/economía , Anticuerpos de Dominio Único/inmunología , Anticuerpos de Dominio Único/uso terapéutico , Glicoproteína de la Espiga del Coronavirus/inmunología , Estados Unidos , United States Food and Drug Administration/legislación & jurisprudencia , Tratamiento Farmacológico de COVID-19RESUMEN
Nicotinic acid adenosine dinucleotide phosphate (NAADP) is a Ca2+-mobilizing second messenger that regulates a wide range of biological activities. However, the mechanism of its biogenesis remains controversial. CD38 is the only enzyme known to catalyze NAADP synthesis from NADP and nicotinic acid. CD38-mediated catalysis requires an acidic pH, suggesting that NAADP may be produced in acidic endolysosomes, but this hypothesis is untested. In this study, using human cell lines, we specifically directed CD38 to the endolysosomal system and assessed cellular NAADP production. First, we found that nanobodies targeting various epitopes on the C-terminal domain of CD38 could bind to cell surface-localized CD38 and induce its endocytosis. We also found that CD38 internalization occurred via a clathrin-dependent pathway, delivered CD38 to the endolysosome, and elevated intracellular NAADP levels. We also created a CD38 variant for lysosome-specific expression, which not only withstood the degradative environment in the lysosome, but was also much more active than WT CD38 in elevating cellular NAADP levels. Supplementing CD38-expressing cells with nicotinic acid substantially increased cellular NAADP levels. These results demonstrate that endolysosomal CD38 can produce NAADP in human cells. They further suggest that CD38's compartmentalization to the lysosome may allow for its regulation via substrate access, rather than enzyme activation, thereby providing a reliable mechanism for regulating cellular NAADP production.