Identification of fibrinogen Aα-chain as an amyloid precursor protein in a case of canine coronary artery amyloidosis

Spontaneous amyloid deposition occurs in the coronary arteries in older dogs, but the pathogenesis, including the precursor protein, is not known. We conducted proteome analysis using liquid chromatography-tandem mass spectrometry to identify the amyloid precursor protein in a 13-y-old male mixed-breed dog with amyloid deposition in intramural coronary arteries, and identified fibrinogen Aα-chain. This form of amyloidosis is characterized by the deposition of amyloid derived from fibrinogen Aα-chains, which has been reported previously only in humans and Japanese squirrels. Within amyloid deposits in the intramural coronary arteries of our canine case, the αC connector region was identified in abundance, whereas in humans and Japanese squirrels, the amyloid arises from the αC domain. Thus, even if amyloid is formed by the same protein, the amyloid-forming peptide and the anatomic site of deposition in our case differed from that in humans and Japanese squirrels.