ALPHA-B-CRYSTALLIN IS ASSOCIATED WITH INTERMEDIATE FILAMENTS IN ASTROCYTOMA-CELLS

alpha B-crystallin, a major protein of the vertebrate lens and a membe r of the small heat shock protein family, is expressed in non-lenticul ar tissues, including the central nervous system, where it is found ma inly in glia. In Rosenthal fibers (RF), astrocytic inclusions that acc umulate in Alexander's Disease, alpha B-crystallin is found with hsp27 and skeins of intermediate filaments (IF) of the GFAP and vimentin ty pes. We have investigated the association between IF and alpha B-cryst allin in a human astrocytoma cell line, U-373MG, which expresses alpha B-crystallin. Cytoskeletal preparations contained alpha B-crystallin, and a filamentous pattern in which alpha B-crystallin co-localized wi th GFAP and vimentin by double label immunofluorescence. Immuno-electr onmicroscopy confirmed the localization to IF. GFAP isolated from bovi ne brain and re-assembled, was associated with alpha B-crystallin. Thu s, a proportion of alpha B-crystallin in astroglia is associated with IF, and this association may be critical in the formation of RF.