Abstract
Alzheimer's disease (AD) is pathologically characterized by the presence of misfolded proteins such as amyloid beta (Aβ) in senile plaques, and hyperphosphorylated tau and truncated tau in neurofibrillary tangles (NFT). The BRI2 protein inhibits Aβ aggregation via its BRICHOS domain and regulates critical proteins involved in initiating the amyloid cascade, which has been hypothesized to be central in AD pathogenesis. We recently detected the deposition of BRI2 ectodomain associated with Aβ plaques and concomitant changes in its processing enzymes in early stages of AD. Here, we aimed to investigate the effects of recombinant BRI2 ectodomain (rBRI276-266) on Aβ aggregation and on important molecular pathways involved in early stages of AD, including the unfolded protein response (UPR), phosphorylation and truncation of tau, as well as apoptosis. We found that rBRI276-266 delays Aβ fibril formation, although less efficiently than the BRI2 BRICHOS domain (BRI2 residues 113-231). In human neuroblastoma SH-SY5Y cells, rBRI276-266 slightly decreased cell viability and increased up to two-fold the Bax/Bcl-2 ratio and the subsequent activity of caspases 3 and 9, indicating activation of apoptosis. rBRI276-266 upregulated the chaperone BiP but did not modify the mRNA expression of other UPR markers (CHOP and Xbp-1). Strikingly, rBRI276-266 induced the activation of GSK3β but not the phosphorylation of tau. However, exposure to rBRI276-266 significantly induced the truncation of tau, indicating that BRI2 ectodomain can contribute to NFT formation. Since BRI2 can also regulate the metabolism of Aβ, the current data suggests that BRI2 ectodomain is a potential nexus between Aβ, tau pathology and neurodegeneration.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Adaptor Proteins, Signal Transducing
-
Alzheimer Disease / metabolism
-
Alzheimer Disease / pathology
-
Amyloid beta-Peptides / metabolism*
-
Apoptosis / drug effects
-
Caspase 3 / metabolism
-
Caspase 9 / metabolism
-
Cell Line, Tumor
-
DNA-Binding Proteins / genetics
-
DNA-Binding Proteins / metabolism
-
Endoplasmic Reticulum Chaperone BiP
-
Glycogen Synthase Kinase 3 / metabolism
-
Glycogen Synthase Kinase 3 beta
-
Heat-Shock Proteins / genetics
-
Heat-Shock Proteins / metabolism
-
Humans
-
Membrane Glycoproteins / chemistry
-
Membrane Glycoproteins / genetics
-
Membrane Glycoproteins / metabolism*
-
Neuroblastoma / metabolism
-
Neuroblastoma / pathology
-
Peptide Fragments / metabolism*
-
Protein Structure, Tertiary
-
Proto-Oncogene Proteins c-bcl-2 / metabolism
-
RNA, Messenger / metabolism
-
Recombinant Proteins / biosynthesis
-
Recombinant Proteins / chemistry
-
Recombinant Proteins / pharmacology
-
Regulatory Factor X Transcription Factors
-
Transcription Factor CHOP / genetics
-
Transcription Factor CHOP / metabolism
-
Transcription Factors / genetics
-
Transcription Factors / metabolism
-
Unfolded Protein Response
-
X-Box Binding Protein 1
-
bcl-2-Associated X Protein / metabolism
-
tau Proteins / metabolism*
Substances
-
Adaptor Proteins, Signal Transducing
-
Amyloid beta-Peptides
-
DDIT3 protein, human
-
DNA-Binding Proteins
-
Endoplasmic Reticulum Chaperone BiP
-
Heat-Shock Proteins
-
ITM2B protein, human
-
Membrane Glycoproteins
-
Peptide Fragments
-
Proto-Oncogene Proteins c-bcl-2
-
RNA, Messenger
-
Recombinant Proteins
-
Regulatory Factor X Transcription Factors
-
Transcription Factors
-
X-Box Binding Protein 1
-
XBP1 protein, human
-
amyloid beta-protein (1-42)
-
bcl-2-Associated X Protein
-
tau Proteins
-
Transcription Factor CHOP
-
GSK3B protein, human
-
Glycogen Synthase Kinase 3 beta
-
Glycogen Synthase Kinase 3
-
Caspase 3
-
Caspase 9