Identification of amyloid precursor protein in synaptic plasma membrane

Although the etiology of Alzheimer's disease has not been elucidated yet, dysfunction and loss of synapses are believed to cause dementia. Recent studies suggest that the primary cause of the disease is closely related to the aberrant processing of the amyloid precursor protein (APP). To investigate the localization of APP at synaptic sites, we obtained synaptic plasma membrane and synaptic vesicles from rat brain. Enhanced chemiluminescence (ECL) western blot analysis using two specific polyclonal antibodies against APP revealed strong APP immunoreactivity in the synaptic plasma membrane, but not in the synaptic vesicle fraction. These data indicate that APP is localized at the synaptic plasma membrane and may play a role in physiological synaptic activity. Alternative localization or aberrant processing of APP at the synaptic site may cause impairment of synaptic function in Alzheimer's disease.