Alexander disease causing mutations in the C-terminal domain of GFAP are deleterious both to assembly and network formation with the potential to both activate caspase 3 and decrease cell viability.

[alexander disease]

Alexander disease is a primary genetic disorder of astrocyte caused by dominant mutations in the astrocyte-specific intermediate filament glial fibrillary acidic protein (GFAP ). While most of the disease-causing mutations described to date have been found in the conserved Î±-helical rod domain , some mutations are found in the C-terminal non-Î±-helical tail domain . Here , we compare five different mutations (N 386 I , S 39 3 I , S 398 F , S 398 Y and D 417 M 14 X ) located in the C-terminal domain of GFAP on filament assembly properties in vitro and in transiently transfected cultured cells . All the mutations disrupted in vitro filament assembly . The mutations also affected the solubility and promoted filament aggregation of GFAP in transiently transfected MCF 7 , SW 13 and U 343 MG cells . This correlated with the activation of the p 38 stress-activated protein kinase and an increased association with the small heat shock protein (sHSP ) chaperone , Î±B-crystallin . Of the mutants studied , D 417 M 14 X GFAP caused the most significant effects both upon filament assembly in vitro and in transiently transfected cells . This mutant also caused extensive filament aggregation coinciding with the sequestration of Î±B-crystallin and HSP 27 as well as inhibition of the proteosome and activation of p 38 kinase . Associated with these changes were an activation of caspase 3 and a significant decrease in astrocyte viability . We conclude that some mutations in the C-terminus of GFAP correlate with caspase 3 cleavage and the loss of cell viability , suggesting that these could be contributory factors in the development of Alexander disease .