STRONG IMMUNOREACTIVITY OF BETA-AMYLOID PRECURSOR PROTEIN, INCLUDING THE BETA-AMYLOID PROTEIN-SEQUENCE, AT HUMAN NEUROMUSCULAR-JUNCTIONS

At the postsynaptic domain of the human neuromuscular junction (NMJ), we have demonstrated strong concentrations of the N-terminus 45 62, C-terminus 676-695 and beta-amyloid protein sequences of beta-amyloid precursor protein (beta-APP). We used well-characterized monoclonal and polyclonal antibodies for co-localization with three other postsynaptic proteins, applying double and triple fluorescence labeling. Strong immunoreactivity of all three beta-APP sequences was found at all NMJs identified by bound alpha-bungarotoxin (alpha-BT), where they co-localized with alpha-BT and with immunoreactive desmin and dystrophin, which are postsynaptic proteins of human NMJs. This appears to be the first demonstration of beta-APP sequences concentrated postsynaptically at human NMJs. Beta-APP may have a role in normal junctional biology and possibly in some diseases affecting NMJs.