title: Diabetic neuropathy: inhibitory G protein dysfunction involves PKC-dependent phosphorylation of Goalpha.
abstract: We examined the hypothesis that decreased inhibitory G protein function in diabetic neuropathy is associated with increased protein kinase C (PKC)-dependent phosphorylation of the Goalpha subunit. Streptozotocin-induced diabetic rats were studied between 4 and 8 weeks after onset of diabetes and compared with aged-matched healthy animals as controls. Opioid-mediated inhibition of forskolin-stimulated cyclic AMP was significantly less in dorsal root ganglia (DRGs) from diabetic rats compared with controls. Activation of PKC in DRGs from control rats was associated with a significant decrease in opioid-mediated inhibition of forskolin-stimulated cyclic AMP that was similar to the decrease in inhibition observed in DRGs from diabetic rats. Both basal and PKC-mediated labeling of Goalpha with 32Pi was significantly less in DRGs from diabetic rats, supporting increased endogenous PKC-dependent phosphorylation of Goalpha. Probing of immunoprecipitated Goalpha with an anti-phospho-serine/threonine specific antibody revealed a significant increase in baseline phosphorylation in diabetic DRGs. Activation of PKC produced a significant increase in phosphorylation in control DRGs but no significant increase in Goalpha in diabetic DRGs. Phosphorylation of PKC-alpha was increased, PKC-betaII was unchanged and PKC-delta decreased in diabetic DRGs. These results suggest that diminished inhibitory G protein function observed in DRGs neurons from diabetic rats involves an isoform-specific PKC-dependent pathway.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Shangguan
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hall
authors.forename: Richard R
authors.initials: RR
authors.lastname: Neubig
authors.forename: John W
authors.initials: JW
authors.lastname: Wiley
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D003929:Diabetic Neuropathies / Q000378:metabolism*; D004195:Disease Models, Animal; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009294:Narcotics / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007527:Isoenzymes; D009294:Narcotics; D021122:Protein Subunits; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins