In Alzheimer disease, amyloid plaques are composed predominantly of which peptide fragment, and from which parent protein is it derived?

• A Tau protein; derived from microtubule-associated protein
• B Prion protein (PrPsc); derived from normal cellular PrPc
• C Abeta (A-beta) peptide; derived from amyloid precursor protein (APP) by beta- and gamma-secretase cleavage ✓
• D Alpha-synuclein; derived from SNCA gene product

Explanation

Amyloid plaques in Alzheimer disease consist primarily of Abeta 40 and Abeta 42 peptides generated by sequential cleavage of the transmembrane amyloid precursor protein (APP) by beta-secretase (BACE1) and then gamma-secretase (presenilin 1/2). Abeta 42 is more amyloidogenic and deposits first. Tau forms neurofibrillary tangles (not plaques). Alpha-synuclein is the Lewy body protein of Parkinson disease. PrPsc is the prion protein of CJD.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.