Fig. 7. ESCRTs are recruited to vacuolar compartments disrupted by silica nanocrystals.

(A and B) PMA-differentiated THP-1 monocytes were treated with or without 50 µg/ml silicon dioxide (SiO₂) nanoparticles for 3 h and stained for IST1 or VPS4A. Shown are widefield fluorescence images of representative cells from each cohort. (C) THP-1 cells treated as above were co-stained for the indicated ESCRT-III proteins along with rhodamine-conjugated phalloidin. Note that the prominent actin-rich puncta correspond to podosomes characteristic of this cell type. Shown are maximum intensity projections of representative cells. Magnified below are single planes corresponding to the boxed area, highlighting the type of compartment (outlined by yellow dotted lines) on which ESCRTs were predominantly observed in SiO₂-fed cells (see fig. S27 for a corresponding three-dimensional rendering). (D) U2OS cells producing mCherry-GAL3 (Chy-GAL3) were fed silica nanoparticles for 1.5 h and costained for the indicated ESCRT-III proteins. Shown are maximum intensity projections and magnified single-plane views of the boxed area. Yellow arrow indicates a compartment (elsewhere encircled by a dotted yellow line) intensely stained for both ESCRT-III proteins but lacking Chy-GAL3; red arrow marks a compartment (elsewhere encircled by a dotted red line) that has accumulated Chy-GAL3 along with some ESCRT. Scale bars equal 10 µm (2 µm in magnified views).