title: Dynamics of mutated GFAP aggregates revealed by real-time imaging of an astrocyte model of Alexander disease.
abstract: Alexander disease (AxD) is a rare neurodegenerative disorder characterized by large cytoplasmic aggregates in astrocytes and myelin abnormalities and caused by dominant mutations in the gene encoding glial fibrillary acidic protein (GFAP), the main intermediate filament protein in astrocytes. We tested the effects of three mutations (R236H, R76H and L232P) associated with AxD in cells transiently expressing mutated GFAP fused to green fluorescent protein (GFP). Mutated GFAP-GFP expressed in astrocytes formed networks or aggregates similar to those found in the brains of patients with the disease. Time-lapse recordings of living astrocytes showed that aggregates of mutated GFAP-GFP may either disappear, associated with cell survival, or coalesce in a huge juxtanuclear structure associated with cell death. Immunolabeling of fixed cells suggested that this gathering of aggregates forms an aggresome-like structure. Proteasome inhibition and immunoprecipitation assays revealed mutated GFAP-GFP ubiquitination, suggesting a role of the ubiquitin-proteasome system in the disaggregation process. In astrocytes from wild-type-, GFAP-, and vimentin-deficient mice, mutated GFAP-GFP aggregated or formed a network, depending on qualitative and quantitative interactions with normal intermediate filament partners. Particularly, vimentin displayed an anti-aggregation effect on mutated GFAP. Our data indicate a dynamic and reversible aggregation of mutated GFAP, suggesting that therapeutic approaches may be possible.
authors.affiliation: INSERM UMR S 546, Paris, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Mignot
authors.forename: Cécile
authors.initials: C
authors.lastname: Delarasse
authors.forename: Séverine
authors.initials: S
authors.lastname: Escaich
authors.forename: Bruno
authors.initials: B
authors.lastname: Della Gaspera
authors.forename: Eric
authors.initials: E
authors.lastname: Noé
authors.forename: Emma
authors.initials: E
authors.lastname: Colucci-Guyon
authors.forename: Charles
authors.initials: C
authors.lastname: Babinet
authors.forename: Milos
authors.initials: M
authors.lastname: Pekny
authors.forename: Patrick
authors.initials: P
authors.lastname: Vicart
authors.forename: Odile
authors.initials: O
authors.lastname: Boespflug-Tanguy
authors.forename: André
authors.initials: A
authors.lastname: Dautigny
authors.forename: Diana
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Danielle
authors.initials: D
authors.lastname: Pham-Dinh
mesh_terms: D038261:Alexander Disease / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D017209:Apoptosis; D001253:Astrocytes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006360:Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D005904:Glial Fibrillary Acidic Protein; D006360:Heat-Shock Proteins; D025801:Ubiquitin; D049452:Green Fluorescent Proteins