FIGURE 7:

Mitochondrial enlargement is accompanied by the formation of uroplakin-positive lipid droplets in Snx31-KO urothelial cells. (A, B) Staining of (A) normal and (B) Snx31-KO urothelial (whole-mount) preparations using Mito-ID Green, a mitochondria dye. Note that while most of the mitochondria in (A) normal urothelial cells are <1 µm wide, those in (B) Snx31-KO are >1 µm (panel C). (D–J) Comparison of the mitochondrial membrane potential (MMP) in whole-mount preparations of (D, E) normal and (G, H) Snx31-KO mouse urothelia that were (D, G) untreated or (E, H) treated with CCCP (a mitochondrial oxidative phosphorylation uncoupler leading to decreased MMP). Mitochondria with high and low MMP are stained in red and green, respectively. SD based on the analysis of mitochondria from 20 cells. (K–O) Paraffin sections of mouse bladder urothelia from Snx31-KO mice were double stained using antibodies to uroplakins (green) and organelle markers in various combinations, as indicated: (K) uroplakin II and AIF, a mitochondrial marker; (L) UPII and PINK1, a mitophagy marker; (M) UPIb and Perilipin 1 (PLIN1), a LD marker; (N) UPIb and Perilipin 2 (PLIN2), another lipid droplet marker; and (O) UPIb, Cox4 (another mitochondrial marker), and PLIN1. Note in O the colocalization of uroplakins with mitochondrial and LD markers (arrows) in some droplets indicating the accumulation of uroplakin-containing LDs in mitochondria. Scale bars = 10 µm in K–L, N, and O; 20 µm in A and B, and D–H; 50 µm in M.