Intermediate filaments (IFs) constitute major components of the cytoskeleton and the nuclear envelope in most cell types. Unlike other cytoskeletons such as microtubules and actin filaments, the protein components of IFs vary in a cell-, tissue-, and differentiation-dependent manner. Although IFs were thought to be relatively stable compared with actin filaments and microtubules, intensive in vitro investigations revealed that site-specific phosphorylation by several kinases, such as protein kinase A (PKA), protein kinase C (PKC), Ca2+/Calmodulin kinase II (CaMKII), cdc2 kinase, and Rho-kinase alters dynamically their structure and induces filament disruption. Glial fibrillary acidic protein (GFAP) belongs to IF proteins. GFAP is a useful marker of mature astrocytes and mutation in the GFAP gene has recently been associated with Alexander disease. Inagaki et al. reported that GFAP was phosphorylated specifically at Thr-7, Ser-13, and Ser-34 by Rho-kinase and Aurora-B and all of these sites were phosphorylated at the cleavage furrow during cytokinesis.Synonyms: Glial Fibrillary Acidic Protein