Decreased ADP-ribosylation of the Galpha(olf) and Galpha(s) subunits by high glucose in pancreatic B-cells.
In HIT-T15 insulinoma B-cells incubated in presence of [(32)P]NAD, we identified by autoradiography and immunoblotting ADP-ribosylation (ADP-R) of the trimeric G-protein Galpha(s) and Galpha(olf) subunits (45 kDa) induced by cholera toxin in M1 (120,000g) and M2 (70,000g) subcellular fractions containing plasma membranes, insulin granules, and mitochondria. This ADP-R indicates that these two fractions contain functionally competent Galpha subunits for adenylyl cyclase activation. Prolonged exposure of HIT-T15 cells to high glucose (25 mM instead of 6 mM) specifically reduced the ADP-R in Galpha(s) and Galpha(olf) subunits in the M1 fraction only, despite the clear increase of their accumulation in this compartment. A similar alteration in the ADP-R of the M1-associated Galpha(s) and Galpha(olf) subunits was observed in pancreatic islets isolated from fasted and fed rats. These results may explain, at least in part, the undesirable effects of sustained hyperglycemia on the cAMP-dependent process of insulin secretion in diabetes.
Phan
H H
HH
Laboratoire de Signalisation et Fonctions Cellulaires, Applications au Diabète et aux Cancers Digestifs, Unité INSERM 482, IFR65, Hôpital Saint-Antoine, 184 rue du Faubourg Saint-Antoine, Paris Cédex 12, 75571, France.
Boissard
C
C
Pessah
M
M
Regnauld
K
K
Emami
S
S
Gespach
C
C
Rosselin
G
G
D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002461:Cell Line, Transformed; D002772:Cholera Toxin / Q000378:metabolism; D006224:Cricetinae; D044385:GTP-Binding Protein alpha Subunits; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D011233:Precipitin Tests; D051381:Rats; D017208:Rats, Wistar
D044385:GTP-Binding Protein alpha Subunits; C084618:olfactory G protein subunit alpha olf; D002772:Cholera Toxin; D019205:GTP-Binding Protein alpha Subunits, Gs; D020962:Heterotrimeric GTP-Binding Proteins; D020727:ADP-Ribosylation Factors; D000262:Adenylyl Cyclases; D005947:Glucose