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The Alexander disease-causing Glial Fibrillary Acidic Protein mutant, R416W, accumulates into Rosenthal fibers by a pathway that involves filament aggregation and the association of alphaB-crystallin and HSP27.

Perng, M. D. and Su, M. and Wen, S. F. and Li, R. and Gibbon, T. and Prescott, A. R. and Brenner, M. and Quinlan, R. A. (2006) 'The Alexander disease-causing Glial Fibrillary Acidic Protein mutant, R416W, accumulates into Rosenthal fibers by a pathway that involves filament aggregation and the association of alphaB-crystallin and HSP27.', American journal of human genetics., 79 (2). pp. 197-213.

Abstract

Here, we describe the early events in the disease pathogenesis of Alexander disease. This is a rare and usually fatal neurodegenerative disorder whose pathological hallmark is the abundance of protein aggregates in astrocytes. These aggregates, termed "Rosenthal fibers," contain the protein chaperones B-crystallin and HSP27 as well as glial fibrillary acidic protein (GFAP), an intermediate filament (IF) protein found almost exclusively in astrocytes. Heterozygous, missense GFAP mutations that usually arise spontaneously during spermatogenesis have recently been found in the majority of patients with Alexander disease. In this study, we show that one of the more frequently observed mutations, R416W, significantly perturbs in vitro filament assembly. The filamentous structures formed resemble assembly intermediates but aggregate more strongly. Consistent with the heterozygosity of the mutation, this effect is dominant over wild-type GFAP in coassembly experiments. Transient transfection studies demonstrate that R416W GFAP induces the formation of GFAP-containing cytoplasmic aggregates in a wide range of different cell types, including astrocytes. The aggregates have several important features in common with Rosenthal fibers, including the association of B-crystallin and HSP27. This association occurs simultaneously with the formation of protein aggregates containing R416W GFAP and is also specific, since HSP70 does not partition with them. Monoclonal antibodies specific for R416W GFAP reveal, for the first time for any IF-based disease, the presence of the mutant protein in the characteristic histopathological feature of the disease, namely Rosenthal fibers. Collectively, these data confirm that the effects of the R416W GFAP are dominant, changing the assembly process in a way that encourages aberrant filament-filament interactions that then lead to protein aggregation and chaperone sequestration as early events in Alexander disease.

Item Type:Article
Full text:PDF - Published Version (4351Kb)
Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1086/504411
Record Created:23 Jun 2008
Last Modified:26 Aug 2011 09:40

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