PMC

APP expression modulates mitochondrial fission/fusion proteins. Representative immunoblot (A) and quantification analysis (B) revealed that DLP1 and OPA1 were reduced, whereas Fis1 was increased significantly in APPwt and APPswe M17 cells (*, P < 0.05).

APP causes abnormal mitochondrial dynamics in M17 cells. (A) Representative immunoblot of APP. Tubulin is used as an internal loading control. (B) Representative pictures of stable M17 lines with different mitochondrial distribution patterns are shown. Green, tubulin; red, mito-DsRed2; blue, DAPi. Mitochondrial distribution (C) and morphology (D) are analyzed. At least 1,000 cells were measured for each cell line. (Scale bars, 10 μm.) *, P < 0.05, Student t test.

APP expression affects mitochondrial fusion. M17 cells were transfected with mito-Dendra2 to label mitochondria. Before photo-conversion (Pre), Dendra2 emits green fluorescence. At time 0, laser activation is applied to ROI (square box) to allow full photo-conversion, from green to red, of all of the mitochondria within the ROI. Thereafter, mitochondrial behavior in the entire cell was monitored for 60 min. Active mitochondria fission (filled arrowhead) and fusion (open arrowhead) of individual mitochondrion could be observed in the representative control cell. (Scale bars, 20 μm.)

APP causes abnormal mitochondrial dynamics in differentiated rat E18 primary hippocampal neurons. Neurons (DIV7) were co-transfected with mito-AcGFP and DsRed-tagged APP or APPswe in the absence or presence of 20 nM BACE inhibitor IV. Three days after transfection, neurons were fixed and evaluated. (A) Representative pictures of positively transfected neurons with different mitochondrial morphology and distribution pattern were shown. Red, DsRed-APP; green, mito-AcGFP. (Scale bar, 100 μm.) (B) Higher magnification pictures of the boxed area in A. (Scale bar, 20 μm.) (C and D) Mitochondria (length and coverage) in a segment of neuronal process at least 200 μm in length beginning from the cell body of neurons were analyzed. At least 20 cells were analyzed each time in three independent experiments.