Final answer:
Beta-amyloid peptide (1-42) aggregates to form plaques due to its misfolding from soluble alpha-helix to sticky beta-pleated sheets, which disrupts neuronal function and is a signature of Alzheimer's disease.
Step-by-step explanation:
The beta-amyloid peptide (1-42) is known to aggregate and form the core of beta-amyloid plaques, which are hallmark features of Alzheimer's disease. These peptides, arising from the enzymatic cleavage of the APP (amyloid precursor protein), can exist in soluble alpha-helix forms that, under pathological conditions, misfold into beta-pleated sheet structures. This conformational change increases the propensity of the peptides to aggregate, as the beta-pleated sheets are sticky, leading to the formation of plaques that can disrupt neuronal function. The aggregation of beta-amyloid is further implicated in disrupting glutamatergic transmission and is associated with excitotoxicity, which can damage neurons and contribute to the progressive cognitive decline seen in Alzheimer's patients.
Additionally, factors such as the impairment of glutamate transporters, the altered expression of synaptic receptors, and interactions with tau protein, all play roles in the toxic effects of amyloid-beta peptides. Prion proteins, normally binding to Ab peptides and preventing their aggregation, when aggregated themselves as PrPsc, can no longer effectively sequester Ab, contributing to the accumulation of beta-amyloid plaques.