Amyloid β-peptide is normally produced in the brain from the amyloid precursor protein (APP). The amyloid cascade hypothesis of Alzheimer disease says that abnormal accumulation in the brain of amyloid β-peptide (Aβ) causes disruption of synaptic neurotransmission and, eventually, the death of neurons and Alzheimer disease (see the image below).
During the past 20 years there has been a large amount of research into the normal physiological role of APP and the idea that Aβ can disrupt synaptic neurotransmission.
In a previous blog post I mentioned that the WNT signaling pathway has been implicated in memory storage. There is evidence that the enzyme glycogen synthase kinase 3β (GSK-3β) is involved in memory deficits seen in Alzheimer disease.
A recently published article provides evidence that Aβ42 binds to the synaptic vesicle protein synaptophysin. Aβ42 disrupts the complex that is normally formed between synaptophysin and VAMP2 altering the way that neurons handle their synaptic vesicles.
If Aβ42 is involved in synaptic transmission by modulating several pre- and postsynaptic mechanisms then such research can identify potential targets for pharmacological intervention against age-associated memory loss.
In a previous blog post I mentioned the synaptic vesicle protein synaptogyrin-3. Synaptophysins and synaptogyrins are members of the tetraspan
vesicle membrane protein family and constitute major secretory vessicle proteins that bind to many other vessicle-associated proteins.