Which peptide fragment is derived from the amyloid precursor protein and forms extracellular deposits in Alzheimer's disease?

Which peptide fragment is derived from the amyloid precursor protein and forms extracellular deposits in Alzheimer's disease?

• A. Tau protein
• B. Prion protein
• C. β-Amyloid (Aβ) peptide
• D. Alpha-synuclein

Answer: (C)

Alzheimer disease features extracellular deposits formed from a peptide produced when amyloid precursor protein (APP) is cut by secretases in the amyloidogenic pathway. Beta-secretase cleaves APP to generate a fragment that, with gamma-secretase, releases β-amyloid peptides—especially Aβ42, which is prone to misfolding and aggregation outside neurons to form plaques. This extracellular accumulation of β-amyloid is a hallmark of the disease. By contrast, tau is an intracellular protein that forms neurofibrillary tangles, prion protein misfolding underlies prion diseases, and alpha-synuclein aggregates into Lewy bodies in synucleinopathies.

Alzheimer disease features extracellular deposits formed from a peptide produced when amyloid precursor protein (APP) is cut by secretases in the amyloidogenic pathway. Beta-secretase cleaves APP to generate a fragment that, with gamma-secretase, releases β-amyloid peptides—especially Aβ42, which is prone to misfolding and aggregation outside neurons to form plaques. This extracellular accumulation of β-amyloid is a hallmark of the disease. By contrast, tau is an intracellular protein that forms neurofibrillary tangles, prion protein misfolding underlies prion diseases, and alpha-synuclein aggregates into Lewy bodies in synucleinopathies.