Purified Bovine GFAP protein Cat# Prot-m-GFAP-bov

Glial Fibrillary Acidic Protein (GFAP) is a major protein of the nervous system and is localized in astrocytes, stem cells, Bergmann glia and non-myelinating Schwann cells. It may also be found in retinal Mueller cells in pathological states, and the levels of the protein generally increase in damage and disease states. GFAP assembles to form 10nm or intermediate filaments in the cytoplasm, and these filaments appear to have an important structural role in the cell.

Glial Fibrillary Acidic Protein (GFAP) was discovered by Amico Bignami and coworkers as a major fibrous protein of multiple sclerosis plaques (2). It was subsequently found to be a member of the 10nm or intermediate filament protein family, specifically the intermediate filament protein family Class III, which also includes peripherin, desmin and vimentin. The GFAP protein runs on gels at ~55 kDa protein, usually associated with lower molecule weight bands which are proteolytic fragments and alternate transcripts from the single gene. GFAP is strongly and specifically expressed in astrocytes and certain other astroglia in the central nervous system, in satellite cells in peripheral ganglia, and in non-myelinating Schwann cells in peripheral nerves. In many damage and disease states GFAP expression is heavily upregulated in astrocytes. In addition neural stem cells frequently strongly express GFAP. Antibodies to GFAP are therefore very useful as markers of astrocytic cells and neural stem cells. In addition many types of brain tumor, presumably derived from astrocytic cells, heavily express GFAP. Finally, Alexander’s disease was recently shown to be caused by point mutations in protein coding region of the GFAP gene (3). All forms of Alexander disease are characterized by the presence of Rosenthal fibers, which are GFAP containing cytoplasmic inclusions found in astrocytes. See also reference 4 for some important earlier work. The HGNC name for this protein is GFAP. There are multiple isoforms of GFAP which have slightly different molecular weights and functional properties (5).

This protein was purified using a modification of the method of Leung and Liem (1). This involves homogenization followed by pelleting of axonal material. The axonal material is then extracted with 1% Triton X-100 to remove myelin by centrifugation several times. The pellet is then dissolved in 6M urea buffer to dissolve cytoskeletal material. This material was then mixed with hydroxyapatite which was then washed with 10mM Urea plus 10mM phosphate buffer pH=7.0. The GFAP protein does not bind to hydroxyapatite under these conditions and can be further purified using ion exchange chromatography on a DEAE column.

1. Leung, C. L. and Liem, R. K. H. Isolation of intermediate filaments. Curr. Prot. Cell Biol. 3:Unit 3.23 doi: 10.1002/0471143030.cb0323s31 (2006).
2. Bignami A, Eng LF, Dahl D, Uyeda CT. Localization of the glial fibrillary acidic protein in astrocytes by immunofluorescence. Brain Res. 43:429-35 1972.
3. Brenner M. et al.. Mutations in GFAP, encoding glial fibrillary acidic protein, are associated with Alexander disease. Nat Genet 27:117-20 2001
4. Liem RKH, Yen SH, Salomon GD and Shelanski ML. Intermediate filaments in nervous tissues. J Cell Biol 79:637-745 (1978).
5. Moeton, M. et al. GFAP isoforms control intermediate filament network dynamics, cell morphology, and focal adhesions Cell Mol Life Sci 73:4101-4120 (2016).