CDNA ISOLATION OF ALZHEIMER'S AMYLOID PRECURSOR PROTEIN FROM CHOLINERGIC NERVE TERMINALS OF THE ELECTRIC ORGAN OF THE ELECTRIC RAY

Alzheimer9s amyloid precursor protein (APP) is a transmembrane protein containing three phosphorylation sites in its cytoplasmic domain. In the present study, we isolated cDNA of APP from electric ray electric lobe ( el APP). This APP ( el APP699) consists of 699 amino acids, contains the β-amyloid domain and has 80.7% similarity with the human APP695 isoform. The cytoplasmic domain, including three phosphorylation sites, was completely conserved. In the nerve terminals of the cholinergic neuron from the electric ray electric organ, we found el APP699 existed exclusively in the mature form. We found the phosphorylated form of mature el APP699 in the nerve terminal as well as in cell body. Immature el APP699 was not subject to phosphorylation. Our findings indicate that, in neurons, the phosphorylation of APP occurs after maturation.