Misfolded protein in the amygdala is a neuropathologic feature of Alzheimer disease and many other neurodegenerative disorders. We examined extracts from human amygdala (snap-frozen at autopsy) to investigate whether novel and as yet uncharacterized misfolded proteins would be detectable. Polypeptides from the detergentinsoluble, urea-soluble protein fractions of amygdala were interrogated using liquid chromatography-electrospray ionization-tandem mass spectrometry. Among the detergent-insoluble proteins identified in amygdala of demented subjects but not controls were Tau, TDP-43, Aβ, α-synuclein, and ApoE. Additional detergent-insoluble proteins from demented subjects in the high-molecular weight portion of SDS gels included NNT, TNIK, PRKDC (DNA-PK, or DNA-PKcs), ferritin light chain (FTL), AIFM1, SYT11, STX1B, EAA1, COL25A1, M4K4, CLH1, SQSTM, SYNJ1, C3, and C4. In follow-up immunohistochemical experiments, NNT, TNIK, PRKDC, AIFM1, and FTL were observed in inclusion body-like structures in cognitively impaired subjects' amygdalae. Doublelabel immunofluorescence revealed that FTL and phospho-PRKDC immunoreactivity colocalized partially with TDP-43 and/or Tau inclusion bodies. Western blots showed high-molecular weight "smears", particularly for NNT and PRKDC. A preliminary genetic association study indicated that rare NNT, TNIK, and PRKDC gene variants had nominally significant association with Alzheimer-type dementia risk. In summary, novel detergent-insoluble proteins, with evidence of proteinaceous deposits, were found in amygdalae of elderly, cognitively impaired subjects.
CITATION STYLE
Gal, J., Chen, J., Katsumata, Y., Fardo, D. W., Wang, W. X., Artiushin, S., … Nelson, P. T. (2018). Detergent insoluble proteins and inclusion body-like structures immunoreactive for PRKDC/DNA-PK/DNA-PKcs, FTL, NNT, and AIFM1 in the amygdala of cognitively impaired elderly persons. Journal of Neuropathology and Experimental Neurology, 77(1), 21–39. https://doi.org/10.1093/jnen/nlx097
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