Diabetes-induced alterations of central nervous system G proteins. ADP-ribosylation, immunoreactivity, and gene-expression studies in rat striatum.
Previous studies from our laboratory have suggested that diabetes-associated central nervous system abnormalities are characterized by progressive alterations of neurotransmitters and of transductional Gi/Go proteins. In this study, we have further characterized these abnormalities in the striatum of alloxan-diabetic rats by means of adenosine 5'-diphosphate (ADP)-ribosylation, and Western and Northern blotting techniques. Fourteen weeks after diabetes induction, pertussis-toxin (PTX) catalyzed ADP-ribosylation of Gi/Go proteins was markedly reduced in diabetic animals, as shown by a clear decrease of 32P-ADPribose incorporation into G protein alpha subunits. In agreement with our previous pharmacological studies that showed a reduction of Gi-mediated modulation of adenylate cyclase activity only at this stage of diabetes, no changes in PTX-mediated ADP-ribosylation were observed earlier (5-wk diabetes). Immunoblotting studies performed by using antibodies selectively raised against Gi-2, Go, and Gs proteins did not reveal any differences between control and diabetic animals at any stage of diabetes. Similarly, the mRNAs corresponding to the alpha subunits of Gi-2, Go, and Gs proteins did not show any marked changes in chronic diabetic rats with respect to control animals. It is therefore concluded that diabetes is associated with development of a time-related alteration of cerebral Gi/Go proteins and that this defect is not owing to gross changes in either content of G proteins or mRNA level, but probably reflects modifications of G protein's structure or physiological status affecting the coupling with membrane effector systems and the sensitivity to PTX.
Finco
C
C
Department of Pharmacology, Chemotherapy, and Medical Toxicology, School of Medicine, University of Milano, Italy.
Abbracchio
M P
MP
Malosio
M L
ML
Cattabeni
F
F
Di Giulio
A M
AM
Paternieri
B
B
Mantegazza
P
P
Gorio
A
A
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D003342:Corpus Striatum / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000276:immunology; D005786:Gene Expression Regulation / Q000502:physiology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats
D012333:RNA, Messenger; D000246:Adenosine Diphosphate Ribose; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases