Enhanced accumulation of phosphorylated α-synuclein in double transgenic mice expressing mutant β-amyloid precursor protein and presenilin-1

A recent report showed that the accumulation of alpha-synuclein (alpha-syn) was detected in the brains of one-third of Alzheimer's disease and Down syndrome patients. However, the relationship between amyloid-beta protein (A beta) and alpha-syn remains unclear. We analyzed the relation between the mutation of presenilin-1 (PS-1) and the pathological features of beta-amyloidosis and alpha-synucleinopathy. We generated doubly transgenic mice overexpressing mutant beta-amyloid precursor protein (PAPP; Tg2576) and mutant PS-1 (PS1L286Vtg; line 198) and analyzed 19 double Tg beta APP(+)/PS+ mice at 5-23 months (young to old), 23 age-matched single Tg beta APP(+)/PS- mice, and 11 non-Tg littermates. Immunohistochemical comparison was performed in these three groups by counting the area and the number of alpha-syn- or phosphorylated alpha-syn (p alpha-syn)-positive dystrophic neurites per plaque (ASPDN, pASPDN). The acceleration of A beta pathology was found with earlier onset and exaggerated numbers in double Tg beta APP(+)/ PS+ compared with single Tg beta APP(+)/PS- mouse brains. The accumulation of ASPDN and pASPDN was also accelerated in double Tg PAPP+/PS' compared with single Tg beta APP(+)/PS- mouse brains, especially in pASPDN. The number and area of alpha-syn and p alpha-syn, and the ratio of p alpha-syn positive neurites were significantly higher in double Tg beta APP(+)/PS+ than in single Tg beta APP(+)/PS- mouse brains in middle-aged and old groups. Additional overexpression of mutant PS-1 accelerated A beta-induced alpha-synucleinopathy and further facilitated the phosphorylation of alpha-syn, suggesting a direct association between mutant PS-1 and phosphorylation of alpha-syn. (c) 2007 Wiley-Liss, Inc.