Glial fibrillary acidic protein (GFAP) is an intermediate filament (IF) protein that is found in glial cells such as astrocytes. It is closely related to its non-epithelial family members, vimentin, desmin, and peripherin, which are all involved in the structure and function of the cell’s cytoskeleton. GFAP helps to maintain astrocyte mechanical strength, as well as the shape of cells.GFAP is expressed in the central nervous system in astrocyte cells. It is involved in many cellular functioning processes, such as cell structure and movement, cell communication, and the functioning of the blood brain barrier.

The predicted amino acid sequence indicated that GFAP shares structural similarities--particularly in the central rod domain and to a lesser degree in the carboxyl-terminal domain--with other IF proteins found in nonepithelial cell types.