Figure 3.
APP interacts with TrkA and regulates TrkA cellular distribution. A, Protein samples from septum of WT, APPYG/YG, or APP−/− mice were immunoprecipitated with an α-TrkA antibody and analyzed by Western blot with an α-APP antibody. B–G, Confocal microscopy of a double immunofluorescence for TrkA (green channel) and APP (red channel) in DRGs of WT (B–D) and APPYG/YG (E–G) mice. In WT mice (B–D), TrkA and APP immunofluorescence appeared homogeneously distributed on the cellular membrane particularly enriching the proximity and the neuritic domains (B, arrows). TrkA-immunostained vesicles (C, D, arrows) were clearly visible on the cellular surface and neuritic domains. Colocalization between TrkA and APP was restricted to the proximity of and along the neuritic domain (A, B, asterisks). E–G, Note in APPYG/YG mice the intracytoplasmatic and perinuclear accumulation of TrkA and APP immunofluorescence and the decrease of immunoreactivity in neuritic structures (G, arrows). Some TrkA-positive vesicles are still present on the cellular membrane (E, F, arrows). APP and TrkA colocalization appeared to increase in the intracytoplasmic domain (E, F, asterisks) and to decrease in neuritic structures (G, asterisks). Scale bars: B, E, 5 μm; C, D, F, 2 μm; G, 3 μm.