Skip to main content
. Author manuscript; available in PMC: 2016 Jun 15.
Published in final edited form as: Curr Biol. 2015 May 28;25(12):1573–1582. doi: 10.1016/j.cub.2015.04.038

Figure 2. Cofilin promotes the binding of tropomyosin to motile actin networks generated by the Arp2/3 complex and capping protein.

Figure 2

(A) Actin networks generated from ActA-coated polystyrene microspheres by the Arp2/3 complex and capping protein exclude tropomyosin in the absence of cofilin. Cofilin renders dendritic actin networks competent to bind tropomyosin. Left: Alexa488-actin. Middle: 1μM Cy3- Tm1A. Right: merge of actin and Tm1A fluorescence. Each row has the indicated concentration of added cofilin. Scale bar: 10μm. (B) Tropomyosin decreases the depolymerizing activity of cofilin. First Column: Motile actin networks generated by the Arp2/3 complex in the presence of capping protein and cofilin (arrow points to severing event). Second-Fourth Columns: Addition of 1μM Tm1A. Second Column: Alexa488-actin. Third Column: Cy3-Tm1A. Fourth Column: Merge. Scale bar: 10μm. (C) Polarized light microscopy of dendritic actin networks show that filaments align only when both cofilin and tropomyosin are present. In each pair of images: the left is Alexa488-actin and Cy3-labeled Tm1A, if present; the right is optical birefringence of the same comet tail. Left pair: 4μM cofilin, 0μM Tm1A. Middle pair: 4μM cofilin, 1μM Tm1A. Right pair: 0μM cofilin, 1μM Tm1A. Line scans of the birefringence (converted to retardance) are displayed below each birefringence image. Scale bar: 10μm. (See also Figure S2).