Study of O-glycan sialylation in C6 cultured glioma cells: regulation of a beta-galactoside alpha 2,3 sialyltransferase activity by Ca2+/calmodulin antagonists and phosphatase inhibitors.
We have demonstrated that the alpha 2,3 sialyltransferase (alpha 2,3 ST) from C6 cultured glioma cells was inhibited in vivo by W-7 and related Ca2+/Calmodulin (Ca/CaM) antagonists while protein kinase C effectors had no effect. Dephosphorylation of alpha 2,3 ST by the wide specificity alkaline phosphatase led to inactivation indicating that the enzyme is phosphorylated. The serine/threonine protein phosphatase inhibitors okadaic acid and Calyculin A led also to an inhibition of alpha 2,3 ST activity. In addition, Ca/CaM antagonists and phosphatase inhibitors led both to an inhibition of a alpha 2,3 sialoglycoprotein from C6 glioma cells as demonstrated with lectin affinity blotting. A concerted regulatory mechanism with phosphorylation/dephosphorylation of alpha 2,3 ST is then postulated.
Reboul
P
P
Laboratoire de Biochimie Générale et Médicale, INSERM-CNRS U.189 Faculté de Médecine Lyon-Sud, Oullins, France.
George
P
P
Geoffroy
J
J
Louisot
P
P
Broquet
P
P
D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002240:Carbohydrate Sequence; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005910:Glioma / Q000201:enzymology*; D006031:Glycosylation; D006706:Homeostasis; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D008387:Marine Toxins; D008969:Molecular Sequence Data; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D012799:Sialyltransferases / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase
D002147:Calmodulin; D004988:Ethers, Cyclic; D007093:Imidazoles; D008387:Marine Toxins; D010080:Oxazoles; D013449:Sulfonamides; D019319:Okadaic Acid; C031938:calmidazolium; C017967:W 7; C034700:N-(6-aminohexyl)-1-naphthalenesulfonamide; C059041:calyculin A; D012799:Sialyltransferases; D010749:Phosphoprotein Phosphatases; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase