Comprehensive profiling of Aβ40 and Aβ42 fibril-interacting proteins reveals PRKCG as a drug-targetable regulator of amyloidogenesis in Alzheimer's disease.

INTRODUCTION: Proteins interacting with amyloid beta (Aβ) fibrils could be key to plaque formation in Alzheimer's disease (AD) and represent potential biomarkers and therapeutic targets. Previous proteomic studies using microdissected plaques might have captured non-specific components rather than true Aβ interactors. METHODS: Biotinylated Aβ40 or Aβ42 peptides were induced to form fibrils, with Scrambled peptides as controls, and incubated with protein extracts from AD and control prefrontal cortex tissue. Pull-down assays coupled with label-free proteomics identified fibril interactors. Dysregulation and localization were assessed by Western blot, immunofluorescence, immunocytochemistry, immunohistochemistry, and in silico analyses. RESULTS: We identified 185 Aβ40- and 874 Aβ42-associated proteins, with 78 shared. Sixteen proteins, including protein kinase C gamma type (PRKCG), displaying altered expression in AD, were validated as actual interactors and plaque components ex vivo. Remarkably, modulation of PRKCG influenced fibril formation. DISCUSSION: This study expands the Aβ plaque-associated proteome, identifies novel interactors, and highlights PRKCG as a drug-targetable regulator of AD amyloidogenesis. HIGHLIGHTS: A comprehensive proteomic profiling allowed identifying proteins interacting with Aβ40 and Aβ42 fibrils, including many novel interactors. Sixteen proteins were validated in vitro and ex vivo as bona fide Aβ plaque constituents. Dysregulated expression of key interactors was confirmed in AD brain and cell models. Modulation of PRKCG activity altered Aβ fibril formation and progression. Findings expand the Aβ-associated proteome and highlight novel targets for AD biomarker and therapeutic development.