Fascin

Fascin is an actin cross-linking protein.

Species and tissue distribution

It is a 54-58 kilodalton monomeric actin filament bundling protein originally isolated from sea urchin egg but also found in Drosophila and vertebrates, including humans. Fascin (from the Latin for bundle) is spaced at 11 nanometre intervals along the filament. The bundles in cross section are seen to be hexagonally packed, and the longitudinal spacing is compatible with a model where fascin cross-links at alternating 4 and 5 actins. It is calcium insensitive and monomeric. Three forms of fascin are found in vertebrates: Fascin1, widely found in the nervous system and elsewhere; fascin2 found in the retinal photoreceptor cells; fascin3, which is only found in the testes.

Function

Fascin binds beta-catenin, and colocalizes with it at the leading edges and borders of epithelial and endothelial cells. The role of Fascin in regulating cytoskeletal structures for the maintenance of cell adhesion, coordinating motility and invasion through interactions with signalling pathways is an active area of research especially from the cancer biology perspective. Fascin localizes to actin-rich protrusions at the cell surface called filopodia. Recent study shows that fascin also localizes to invadopodia, membrane protrusions formed at the adherent cell surface that facilitate extracellular matrix (ECM) invasion, this provide a potential molecular mechanism for how fascin increases the invasiveness of cancer cells since fascin expression is upregulated in a spectrum of cancers.