The Actin-Bundling Protein Fascin Stabilizes Actin in Invadopodia and Potentiates Protrusive Invasion

Abstract

Fascin is an actin-bundling protein involved in filopodia assembly and cancer invasion and metastasis of multiple epithelial cancer types. Fascin forms stable actin bundles with slow dissociation kinetics in vitro and is regulated by phosphorylation of serine 39 by protein kinase C (PKC). Cancer cells use invasive finger-like protrusions termed invadopodia to invade into and degrade extracellular matrix. Invadopodia have highly dynamic actin that is assembled by both Arp2/3 complex and formins; they also contain components of membrane trafficking machinery such as dynamin and cortactin and have been compared with focal adhesions and podosomes. We show that fascin is an integral component of invadopodia and that it is important for the stability of actin in invadopodia. The phosphorylation state of fascin at S39, a PKC site, contributes to its regulation at invadopodia. We further implicate fascin in invasive migration into collagen I-Matrigel gels and particularly in cell types that use an elongated mesenchymal type of motility in 3D. We provide a potential molecular mechanism for how fascin increases the invasiveness of cancer cells, and we compare invadopodia with invasive filopod-like structures in 3D.

Targeted inhibition of fascin function blocks tumour invasion and metastatic colonization

“…4h-j). We should note that, in tumour cells, these finger-like membrane protrusions are sometimes called invadopodia 50,51 . For simplicity, here we referred them as membrane protrusions.…”

The interplay between the proteolytic, invasive, and adhesive domains of invadopodia and their roles in cancer invasion

“…[77][78][79] Additional reports indicate that actin polymerization in invadopodia of certain cancer cells (e.g., MDA-231 breast cancer cell line) can also be induced by specific Diaphanous-related formins, whose cell type specificity, and mode of action and regulation, are still unclear. 80 The actin bundle, thus formed, is further stabilized and mechanically reinforced by cortactin 5 and fascin, 73,81,82 producing a stable "invasive protrusion" that pushes against the ventral cell membrane, promoting its penetration into the ECM. 5,27,28,36,39,68,83 To get a closer look at the constituents of the invasive domain ( Fig.…”

“…107 The actin bundling capacity of fascin is attributed to the actin-binding sites at its N-and C-termini, 108,109 and the bundling activity in invadopodia is specifically attributed to a PKC phosphrylation site at serine 39. 81 Fascin is upregulated in cells localized at the invasive front of various invasive cancers. 110,111 Fascin is important for invadopodia elongation and actin filament stability, and its depletion was shown to reduce the ability of invadopodia to degrade the ECM.…”

“…110,111 Fascin is important for invadopodia elongation and actin filament stability, and its depletion was shown to reduce the ability of invadopodia to degrade the ECM. 81,83 (6) Other cytoskeletal systems, besides the actin network, namely, microtubules, and intermediate filaments, are believed to play either direct or indirect roles in invadopodia formation and function.…”

Mechanism of Actin Filament Bundling by Fascin

“…Fascin is the major actin filament (F-actin) bundling protein in protrusive cellular structures such as filopodia, dendrites, and invadopodia that play critical roles in cell motility, guidance, and invasion of the extracellular matrix (1)(2)(3). Fascin expression is up-regulated in various types of cancers, including lymphomas, glioblastomas, and carcinomas, where its overexpression correlates with increased tumor metastasis and invasiveness (4).…”