Fascin

Fascin is a actin cross-linking protein.

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.

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.

Abnormal fascin expression or function has been implicated in breast cancer, colon cancer, esophageal squamous cell carcinoma, gallbladder cancer and prostate cancer.

Structure
Fascin is a structural protein found in mesenchyme, nervous, and retinal tissue and is used in the bundling of actin molecules.

The structure of human fascin has been determined to a resolution of 2.9 Å and reveals an arrangement of four tandem beta-trefoil domains that form a two lobed structure with pseudo 2-fold symmetry. It is stabilized by a hydrophobic core and a hydrophilic surface since it is often found inside cell cytoplasm in the formation of filopodia.