Membrane-bound form of ADP-ribosyl cyclase in rat cortical astrocytes in culture.
ADP-ribosyl cyclase activities in cultured rat astrocytes were examined by using TLC for separation of enzymatic products. A relatively high rate of [3H]cyclic ADP-ribose production converted from [3H]NAD+ by ADP-ribosyl cyclase (2.015+/-0.554 nmol/min/mg of protein) was detected in the crude membrane fraction of astrocytes, which contained approximately 50% of the total cyclase activity in astrocytes. The formation rate of [3H]ADP-ribose from cyclic ADP-ribose by cyclic ADP-ribose hydrolase and/or from NAD+ by NAD glycohydrolase was low and enriched in the cytosolic fraction. Although NAD+ in the extracellular medium was metabolized to cyclic ADP-ribose by incubating cultures of intact astrocytes, the presence of Triton X-100 in the medium for permeabilizing cells increased cyclic ADP-ribose production three times as much. Isoproterenol and GTP increased [3H]cyclic ADP-ribose formation in crude membrane-associated cyclase activity. This isoproterenol-induced stimulation of membrane-associated ADP-ribosyl cyclase activity was confirmed by cyclic GDP-ribose formation fluorometrically. This stimulatory action was blocked by prior treatment of cells with cholera toxin but not with pertussis toxin. These results suggest that ADP-ribosyl cyclase in astrocytes has both extracellular and intracellular actions and that signals of beta-adrenergic stimulation are transduced to membrane-bound ADP-ribosyl cyclase via G proteins within cell surface membranes of astrocytes.
Hotta
T
T
Department of Bioregulation Research, Nagoya City University Medical School, Nagoya, Japan.
Asai
K
K
Fujita
K
K
Kato
T
T
Higashida
H
H
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000378:metabolism*; D001253:Astrocytes / Q000201:enzymology*; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000201:enzymology*; D005470:Fluorometry; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008562:Membrane Glycoproteins; D009244:NAD+ Nucleosidase / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000201:enzymology
D015703:Antigens, CD; D000943:Antigens, Differentiation; D008562:Membrane Glycoproteins; D006160:Guanosine Triphosphate; D036541:ADP-ribosyl Cyclase; C498156:Cd38 protein, rat; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1; D007545:Isoproterenol