To test this hypothesis, we analysed the APPpT668 level using WB (Fig. 5A–C) and the APP–TrkA interaction using IP (Fig. 5D,E) in brain samples from control subjects without neurological diseases (CTR; n = 3), patients with AD (AD; n = 3) and subjects affected by other neurological diseases (OND; n = 3). Here, APP is linked to Alzheimer disease.