KIF5B and KIF3A are required for pericellular matrix remodeling and MT1-MMP exocytosis. (A–C) Silencing of KIF5B, KIF3A, and MT1-MMP in MDA-MB-231 cells. β-Actin was used as a loading control. (D) FITC-gelatin degradation. n, number of cells scored for each MDA-MB-231 cell population treated with the indicated siRNA. (E) Mean invasion area of MDA-MB-231 cells using the circular invasion assay. Values represent mean invasion index ± SEM from three independent experiments normalized to invasion index of siNT-treated cells set to 100. n, number of 96 wells analyzed for each cell population. (F) FITC-gelatin degradation by MCF10DICIS.com cells treated with indicated siRNAs as in D. (G) Invasion of MCF10DICIS.com cells as in E. (H) Collagenolysis by MDA-MB-231 cells treated with indicated siRNAs. Values are mean normalized degradation index ± SEM. n, number of cells analyzed for each cell population. (I) MDA-MB-231 cells expressing MT1-MMPpHluorin silenced for the indicated proteins were seeded on type I collagen fibers and imaged over a 30-min time period. Frequency of MT1-MMPpHluorin exocytic events was quantified (events/cell/minute). n, number of cells analyzed for each cell population. *, P < 0.05; ***, P < 0.001 (as compared with siNT-treated cells).