Figure 3.

hAPP and Drp1KO combine to overload mitochondria with calcium. Primary hippocampal neurons from Drp1^lox/lox mice were cotransfected with Cre (to delete Drp1; Drp1KO), mutant hAPP, and/or control vector (control), as well as CEPIA3mt to visualize mitochondrial calcium (mitoCa²⁺) and mApple, and were subjected to a sequence of four individual electrical stimuli (30 Hz for 3s, blue horizontal lines) to evoke calcium entry. A, example trace of a control neuron that recovers baseline mitoCa²⁺ levels following each stimulus. B and C, Example traces of hAPP-Drp1KO neurons successfully (B) and unsuccessfully (C) recovering mitoCa²⁺ levels after evoked influx. D, average mitoCa²⁺ levels for control (black), Drp1KO (gray), hAPP (purple), and hAPP-Drp1KO (red) neurons. E, average amplitude for each mitoCa²⁺ peak in (D). The combination of hAPP and Drp1KO, but neither of the perturbations alone, increased mitoCa²⁺ loading during electrically evoked calcium entry compared to control. n = 15–18 coverslips/group (1 cell/coverslip), compilation of six independent experiments. Data show mean ± SEM; ∗∗p < 0.01 by two-way repeated measures ANOVA and Holm–Sidak post hoc test. F, graph shows the fraction of neurons from (D) that successfully recovered baseline mitoCa²⁺ levels following each of the four stimuli. The combination of hAPP and Drp1KO decreases the fraction of functional neurons; ∗p < 0.05 by log-rank test.