BACE2 degrades Aß at intracellular sites. A, CHO cells expressing GFP-BACE2 (green, left), but not those expressing GFP alone (green, right), exhibit marked reductions in intracellular Aß (red). For these experiments, cells were loaded for 6 h with 400 nM fluorescently labeled Aß40, washed, then incubated at 37°C for 1 h prior to imaging by conventional fluorescence microscopy. B,C, BACE2 overexpression significantly lowers intracellular Aß. B, Quantification of intracellular pools of fluorescently labeled Aß40 in CHO cells 0 and 2 hours after loading. C, Relative levels of intracellular (unmodified) Aß40 in CHO cells 0 and 2 hours after loading, as quantified by ELISA. Data are mean ± SEM of 3 replicates, normalized to vector-only controls. *P <0.05 by Tukey’s multiple comparisons test.