Cortactin regulates cofilin and N-WASp activities to control the stages of invadopodium assembly and maturation

Abstract

Invadopodia are matrix-degrading membrane protrusions in invasive carcinoma cells. The mechanisms regulating invadopodium assembly and maturation are not understood. We have dissected the stages of invadopodium assembly and maturation and show that invadopodia use cortactin phosphorylation as a master switch during these processes. In particular, cortactin phosphorylation was found to regulate cofilin and Arp2/3 complex–dependent actin polymerization. Cortactin directly binds cofilin and inhibits its severing activity. Cortactin phosphorylation is required to release this inhibition so cofilin can sever actin filaments to create barbed ends at invadopodia to support Arp2/3-dependent actin polymerization. After barbed end formation, cortactin is dephosphorylated, which blocks cofilin severing activity thereby stabilizing invadopodia. These findings identify novel mechanisms for actin polymerization in the invadopodia of metastatic carcinoma cells and define four distinct stages of invadopodium assembly and maturation consisting of invadopodium precursor formation, actin polymerization, stabilization, and matrix degradation.

Abl2/Abl-related Gene Stabilizes Actin Filaments, Stimulates Actin Branching by Actin-related Protein 2/3 Complex, and Promotes Actin Filament Severing by Cofilin

“…3E). Cortactin binding to cofilin inhibits cofilin severing of actin filaments (12,13). We observe a similar effect, but with significantly higher concentrations of cofilin than cortactin suggesting an alternative mechanism, possibly mediated through structural changes to the actin filament.…”

“…One important Arg substrate is cortactin, an actin-binding protein that stimulates the Arp2/3 complex to nucleate actin filament branches (9 -11). Cortactin also stabilizes actin filament branches (9) and inhibits actin filament severing by cofilin (12,13).…”

The guanine nucleotide exchange factor Arhgef5 plays crucial roles in Src-induced podosome formation

“…1B). Because it is known that phosphorylation of cortactin Y421 is important for invadopodium precursor formation (Oser et al, 2009), the lower affinity of Fyn-MER for cortactin might partly explain its lower efficacy in podosome formation. We also found that the intracellular localization of Src and Fyn was appreciably different.…”

“…Stress fibers are disrupted in cells with podosomes and invadopodia, whereas FAs associate and assemble with stress fibers (Carragher and Frame, 2004;Gimona and Buccione, 2006;Schoenwaelder and Burridge, 1999). Furthermore, podosomes and invadopodia specifically contain cortactin, N-WASP and Tks5 (also known as Fish), all of which can serve as substrates for Src family kinases (Mizutani et al, 2002;Oser et al, 2009;Seals et al, 2005;Suetsugu et al, 2002). Cortactin and N-WASP are required for actin remodeling during invadopodium formation (Luxenburg et al, 2006b;Mizutani et al, 2002;Yamaguchi et al, 2005).…”

Trailblazing LIM kinases take the lead in collective tumor cell invasion

“…These effects were associated with an inability to form protrusive matrix-degrading invadapodia structures, which previous research has shown to be dependent on F-actin stabilization. [19][20][21] Not only did LIMK inhibition result in an overall decrease in F-actin staining intensity, but fluorescence recovery after photobleaching (FRAP) experiments revealed that F-actin stability was significantly reduced. As a result, we concluded that at least one way that LIMK inhibition impaired the ability of cells to lead collective invasion was through reduced F-actin stability, which directly impacted upon the ability of cells to degrade matrix.…”