title: Ganglioside-modulated protein phosphorylation. Partial purification and characterization of a ganglioside-stimulated protein kinase in brain.
abstract: Gangliosides have profound modulatory effects on protein phosphorylation in brain. A protein kinase activated directly by gangliosides has been partially purified from the particulate fractions of guinea pig brain through extraction with nonionic detergent, ion-exchange chromatography, hydrophobic chromatography, and gel filtration. This novel ganglioside-stimulated protein kinase is distinct from cAMP-dependent, Ca2+/calmodulin-dependent, and Ca2+/phospholipid-dependent protein kinases. The partially purified kinase preparation could undergo ganglioside-stimulated autophosphorylation of a major phosphoprotein with Mr corresponding to 68,000. It also could phosphorylate exogenous substrates such as the synthetic peptide Leu-Arg-Arg-Ala Ser-Leu-Gly. The requirement of gangliosides for the activation of kinase activity is dose-dependent and specific. Among the various gangliosides tested, GT1b and GD1a were found to be the most potent activators, whereas GD1b and GM1 were slightly less effective. The activation process is rapid and does not require the presence of Ca2+, suggesting that the stimulatory effect of gangliosides is not mediated through limited proteolysis or Ca2+-glycolipid complexes. Although the exact physiological significance of the ganglioside-stimulated protein kinase is not known at present, it is possible that certain functions related to gangliosides in the nervous system are mediated through the activation of this novel enzyme.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D000242:Cyclic AMP / Q000378:metabolism; D005732:Gangliosides / Q000494:pharmacology*; D007527:Isoenzymes / Q000302:isolation & purification*; D008970:Molecular Weight; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000302:isolation & purification*; D011506:Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D005732:Gangliosides; D007527:Isoenzymes; D011506:Proteins; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C