Immunolocalization of fascin, an actin-bundling protein and glial fibrillary acidic protein in human astrocytoma cells.

Fascin is a 55-kDa globular protein that functions to organize filamentous-actin into parallel bundles. A role for fascin in cell migration has led to its study in many tumor types. In this report, we investigate fascin in astrocytomas. We show that fascin is expressed in astrocytes and in a panel of human astrocytoma cell lines. Immunofluorescence analysis demonstrates that fascin and the intermediate filament protein, glial fibrillary acidic protein (GFAP), are both expressed in the perinuclear region and within cytoplasmic processes of astrocytes and astrocytoma cells. Amino acid residues within the NH2 terminus of GFAP can undergo phosphorylation; these modifications regulate intermediate filament disassembly and occur during cytokinesis. We show that fascin and specific phosphorylated species of GFAP colocalize within dividing cells. Finally, we demonstrate that fascin co-immunoprecipitates with GFAP and that immunocomplex formation is preferential for GFAP phosphorylated at serine residues 8 and 13. These data show that fascin and GFAP are immunolocalized regionally within cells and tumors of astrocytic origin and suggest that their binding may occur during dynamic reorganization of intermediate filaments.