title: Protective role of phosphorylation in turnover of glial fibrillary acidic protein in mice.
abstract: Glial fibrillary acidic protein (GFAP), the principal intermediate filament (IF) protein of mature astrocytes in the CNS, plays specific roles in astrocyte functions. GFAP has multiple phosphorylation sites at its N-terminal head domain. To examine the role of phosphorylation at these sites, we generated a series of substitution mutant mice in which phosphorylation sites (Ser/Thr) were replaced by Ala, in different combinations. Gfap(hm3/hm3) mice carrying substitutions at all five phosphorylation sites showed extensive decrease in both filament formation and amounts of GFAP. Gfap(hm1/hm1) and Gfap(hm2/hm2) mice, which carry substitutions at three of five sites and in different combinations, showed differential phenotypes. Although Gfap(hm3/hm3) mice retained GFAP filaments in Bergmann glia in the cerebellum, the (Gfap(hm3/hm3):Vim(-/-)) mice lacked GFAP filaments. Pulse-chase experiments of cultured astrocytes indicated that the Hm3-GFAP encoded by Gfap(hm3) was unstable particularly in the absence of vimentin, another IF protein. These results revealed the role of phosphorylation in turnover of GFAP and a synergistic role of GFAP and vimentin in the dynamics of glial filaments. The data further suggest that each of the phosphorylated sites has a distinct impact on the dynamics of GFAP.
authors.affiliation: Laboratory for Behavioral Genetics, RIKEN Brain Science Institute, Wako 351-0198, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takemura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Gomi
authors.forename: Emma
authors.initials: E
authors.lastname: Colucci-Guyon
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Itohara
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002452:Cell Count; D002478:Cells, Cultured; D018390:Gene Targeting; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics* / Q000378:metabolism*; D007150:Immunohistochemistry; D007382:Intermediate Filaments / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009900:Optic Nerve / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014746:Vimentin / Q000172:deficiency / Q000235:genetics
chemical_list: D005904:Glial Fibrillary Acidic Protein; D014746:Vimentin