Extracellular NAD(+) induces calcium signaling and apoptosis in human osteoblastic cells.
ADP-ribosyl cyclase/CD38 is a bifunctional enzyme that catalyzes at its ectocellular domain the synthesis from NAD(+) (cyclase) and the hydrolysis (hydrolase) of the calcium-mobilizing second messenger cyclic ADP ribose (cADPR). Furthermore, CD38 mediates cADPR influx inside a number of cells, thereby inducing Ca(2+) mobilization. Intracellularly, cADPR releases Ca(2+) from ryanodine-sensitive pools, thus activating several Ca(2+)-dependent functions. Among these, the inhibition of osteoclastic-mediated bone resorption has been demonstrated. We found that HOBIT human osteoblastic cells display ADP-ribosyl cyclase activity and we examined the effects of CD38 stimulation on osteoblasts function. Extracellular NAD(+) induced elevation of cytosolic calcium due to both Ca(2+) influx from the extracellular medium and Ca(2+) release from ryanodine-sensitive intracellular stores. Culturing these cells in the presence of NAD(+) caused a complete growth arrest with a time-dependent decrease of cell number and the appearance of apoptotic nuclei. The first changes could be observed after 24 h of treatment and became fully evident after 72-96 h. We propose a role of extracellular NAD(+) in bone homeostatic control.
Romanello
M
M
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, G. Gaslini Institute, via Licio Giorgieri 1, Trieste, I-34127, Italy.
Padoan
M
M
Franco
L
L
Veronesi
V
V
Moro
L
L
D'Andrea
P
P
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000378:metabolism; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000378:metabolism; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D036563:Cyclic ADP-Ribose; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006801:Humans; D008562:Membrane Glycoproteins; D018715:Microscopy, Video; D009243:NAD / Q000378:metabolism* / Q000494:pharmacology; D009244:NAD+ Nucleosidase / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D013268:Stimulation, Chemical; D019284:Thapsigargin / Q000494:pharmacology
D015703:Antigens, CD; D000943:Antigens, Differentiation; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D008562:Membrane Glycoproteins; D009243:NAD; C049925:fura-2-am; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D000246:Adenosine Diphosphate Ribose; D019284:Thapsigargin; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1; D002118:Calcium; D016257:Fura-2