Knockdown of kinesin isoforms influences degradation of fibronectin, collagen I, and gelatin matrix. Confocal micrographs of macrophages transfected with siRNA specific for kinesin isoforms and seeded on rhodamine-labeled matrix: fibronectin (A-G), collagen I (I-O), or gelatin (Q-W). (A,I,Q) control siRNA, (B,J,R) KIF5B siRNA, (C,K,S) KIF3A siRNA, (D,L,T), KIF3B siRNA, (E,M,U) double knockdown using KIF5B siRNA and KIF3B siRNA, (F,N,V) KIF1C siRNA, and (G,O,W) MT1-MMP siRNA. Matrix degradation is visible as dark areas by concomitant loss of the fluorescent label. Insets show respective F-actin staining by Cy5-labeled phalloidin. White bar indicates 10 μm. (H,P,X) Statistical evaluation of matrix degradation in cells treated with various siRNAs. The degree of matrix degradation was analyzed by fluorescence measurements of each time 3 × 30 cells. Complete absence of labeled matrix beneath the podosome-covered area of cells was set as 100% degradation. Cells were scored into groups according to the degree of matrix degradation (0%-25%; 26%-100%). *P < .05, **P < .01 compared with control. For specific values, see supplemental Table 1. Bars indicate mean values ± SD.