Endosome and Lysosome Membrane Properties Functionally Link to γ-Secretase in Live/Intact Cells

Our unique multiplexed imaging assays employing FRET biosensors have previously detected that gamma-secretase processes APP C99 primarily in late endosomes and lysosomes in live/intact neurons. Moreover we have shown that A beta peptides are enriched in the same subcellular loci. Given that gamma-secretase is integrated into the membrane bilayer and functionally links to lipid membrane properties in vitro, it is presumable that gamma-secretase function correlates with endosome and lysosome membrane properties in live/intact cells. In the present study, we show using unique live-cell imaging and biochemical assays that the endo-lysosomal membrane in primary neurons is more disordered and, as a result, more permeable than in CHO cells. Interestingly, gamma-secretase processivity is decreased in primary neurons, resulting in the predominant production of long A beta 42 instead of short A beta 38. In contrast, CHO cells favor A beta 38 over the A beta 42 generation. Our findings are consistent with the previous in vitro studies, demonstrating the functional interaction between lipid membrane properties and gamma-secretase and provide further evidence that gamma-secretase acts in late endosomes and lysosomes in live/intact cells.

Automated summary

Our previous studies using FRET biosensors have shown that gamma-secretase primarily processes APP C99 in late endosomes and lysosomes in live neurons. In this study, we demonstrate that the endo-lysosomal membrane in primary neurons is more disordered and permeable compared to CHO cells. We also find that gamma-secretase has decreased processivity in primary neurons, resulting in the production of longer A beta 42 peptides. These findings support the functional interaction between lipid membrane properties and gamma-secretase in live cells.