Filopodia associated with matrix degradation are induced by PSTPIP1 R405C. (A-B) Representative images of podosomes and filopodia formed in the THP-1 rescue cell lines. (A) The Arp2/3 complex was stained in podosomes and filopodia using anti-ARPC2 antibody (magenta) in THP-1 rescue cells expressing GFP-tagged PSTPIP1 constructs (green). (B) VASP was labeled in podosomes and filopodia with anti-VASP antibody (magenta) in THP-1 rescue cells expressing GFP-tagged PSTPIP1 constructs (green). (C) Representative images of gelatin degradation in the THP-1 rescue lines plated on Alexa Fluor 568–conjugated gelatin-coated coverslips (magenta). F-actin was stained with CruzFluor 405 phalloidin (green), and anti-GFP antibody (gray) was used to amplify the GFP signal. Orange pixels in the Degraded Area panel were those counted as degraded. (D) Quantification of the amount of gelatin degraded by the THP-1 rescue cells as a percentage of cell area. Scale bar, 20 μm. Values are mean ± SEM from 4 independent experiments. *P < .05, as determined by one-way ANOVA with Sidak’s multiple comparisons test. NS, nonsignificant.