APP and early-onset autosomal dominant Alzheimer disease: Brain tissue from patients with Alzheimer's disease has shown an increase of phosphorylation of Tyr-682, located on the conserved Y682ENPTY motif, and Thr-668 residues, both in the intracellular domain (AID) of amyloid β precursor protein (APP), although the role of these two residues is not yet known.