Figure 5.

Bioenergetic deficiency coupled with impaired mitochondrial turnover in AD neurons. (a-b) Representative images (a) and quantitative analysis (b) showing that OXPHOS stimulation failed to elevate energy metabolism in cultured cortical neurons derived from mutant HsAPP Tg mouse brains. Note no increase in cellular ATP levels in mutant HsAPP neurons following glutamine incubation. The YFP:CFP emission ratios in the soma and the axon of mutant HsAPP neurons grown in media with and without glutamine were normalized to those in the neurons from WT littermate controls, respectively. (c-d) Defective mitochondrial turnover in AD neurons upon stimulating OXPHOS activity. Note increased levels of LC3-II and LAMP1 along with TOMM20, VDAC1, and SOD2 in mutant HsAPP neurons treated with glutamine as compared to those of control mutant HsAPP neurons in the absence of glutamine. Data were quantified from four independent experiments. (e-f) Augmentation of Δψ_m depolarization in AD neurons under glutamine oxidation. Note that the mean intensity of TMRE fluorescence was decreased in the soma of mutant HsAPP neurons in the presence of glutamine relative to that of control neurons under the glycolytic condition. (g-h) OXPHOS stimulation exacerbated the accumulation of oxidized mitochondria in AD neurons. Mean fluorescence intensity ratios evoked by the two excitation wavelengths (405 nm or 488 nm) at individual mitochondria in the soma and the axons of AD neurons incubated with glutamine were quantified and normalized to those of control AD neurons grown in media without glutamine, respectively (g). Data were quantified from a total number of neurons (n) indicated on the top of bars (b, f, and g) from at least four independent repeats. Scale bars: 10 μm. Error bars: SEM. Student’s t test: *p < 0.05; **p < 0.01; ***p < 0.001