IDENTIFICATION OF PHOSPHORYLATION SITES ON GLIAL FIBRILLARY ACIDIC PROTEIN FOR CDC2 KINASE AND CA2-CALMODULIN-DEPENDENT PROTEIN-KINASE-II()

We identified the phosphorylation sites of glial fibrillary acidic pro tein (GFAP) for cdc2 kinase and Ca2+-calmodulin (CaM)-dependent protei n kinase II. GFAP was phosphorylated to similar to 0.2 mol of phosphat e/mol of GFAP by cdc2 kinase, and this phosphorylation did not induce disassembly of the filament structure. On the other hand, GFAP was pho sphorylated to similar to 1.9 mol of phosphate/mol of GFAP by Ca2+-CaM -dependent protein kinase II, and this phosphorylation did induce disa ssembly of the filament. Sequential analysis of the purified phosphope ptides revealed that only Ser8 on GFAP was phosphorylated by cdc2 kina se, whereas Ser13, Ser17, Ser34, and Ser389 on GFAP were phosphorylate d by Ca2+-CaM-dependent protein kinase II.