Ectocellular in vitro and in vivo metabolism of cADP-ribose in cerebellum.
CD38, a type II transmembrane glycoprotein predominantly expressed in blood cells, is a bifunctional ectoenzyme directly involved in the metabolism of cADP-ribose (cADPR). This is a potent Ca2+ mobilizer in several types of cells. The relationship between the ectocellular site of cADPR production and its intracellular calcium-related functions is poorly understood. Cultured rat cerebellar granule cells showed both enzymic activities of CD38, ADP-ribosyl cyclase and cADPR hydrolase, at a ratio of 16 to 1 respectively, and were immunostained by the anti-(human CD38) monoclonal antibody IB4. In these cells externally added cADPR and beta-NAD+ (the precursor of cADPR), but not alpha-NAD+ or ADP-ribose, enhanced the peak of the depolarization-induced rise in intracellular Ca2+ concentration. This effect was inhibited by 1 microM ryanodine, suggesting a potentiation of calcium-induced calcium release by cADPR. CD38 ectoenzyme activities, ADP-ribosyl cyclase and cADPR hydrolase, were also demonstrated in vivo by microdialysis of adult rat cerebellum, where IB4 bound to granule neurons selectively. Trace amounts (11.5 +/- 3.8 nM) of NAD+ were detected by microdialysis sampling and sensitive assays in the basal interstitial fluid of the cerebellum. These results provide a link between ectocellular cADPR turnover and intracellular calcium mobilization in cerebellum.
De Flora
A
A
Istituto di Chimica Biologica, Università di Genova, Italy.
Guida
L
L
Franco
L
L
Zocchi
E
E
Pestarino
M
M
Usai
C
C
Marchetti
C
C
Fedele
E
E
Fontana
G
G
Raiteri
M
M
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D036563:Cyclic ADP-Ribose; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins; D008564:Membrane Potentials / Q000187:drug effects; D017551:Microdialysis; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D009244:NAD+ Nucleosidase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D015703:Antigens, CD; D000943:Antigens, Differentiation; D008562:Membrane Glycoproteins; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D009699:N-Glycosyl Hydrolases; D036541:ADP-ribosyl Cyclase; C498156:Cd38 protein, rat; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1; D002118:Calcium