Oxidative lipid modification of nicastrin enhances amyloidogenic γ‐secretase activity in Alzheimer’s disease

Abstract

Summary The cause of elevated level of amyloid β-peptide (Aβ42) in common late-onset sporadic (AD) has not been established. Here we show that the membrane lipid peroxidation product 4-hydroxynonenal (HNE) is associated with amyloid and neurodegenerative pathologies in AD, and that it enhances γ-secretase activity and Aβ42 production in neurons. The γ-secretase substrate receptor, nicastrin was found to be modified by HNE in cultured neurons and in brain specimens from AD patients, in which HNE-nicastrin levels were found to be correlated with increased γ-secretase activity and Aβ plaque burden. Furthermore, HNE modification of nicastrin enhanced its binding to the γ-secretase substrate, amyloid precursor protein (APP) C99. In addition, the stimulation of γ-secretase activity and Aβ42 production by HNE were blocked by an HNE-scavenging histidine analog in a 3xTgAD mouse model of AD. These findings suggest a specific molecular mechanism by which oxidative stress increases Aβ42 production in AD, and identify HNE as a novel therapeutic target upstream of the γ-secretase cleavage of APP.

OCIAD2 activates γ-secretase to enhance amyloid β production by interacting with nicastrin

“…In Sh-SY5Y neuroblastoma cells, OCIaD2 expression increased upon treatment with h 2 O 2 . Not only are reactive oxygen species (ROS) strongly associated with aD but they also stimulate γ-secretase activity [1,27,45]. thus, an increase in OCIaD2 levels may underlie an ROS-induced increase of aβ production through γ-secretase activation.…”

“…Genome-wide functional screening using cDNa By modifying pC99-GVP and UaS-Luciferase assay [27], we generated C99-tetOn and tRe-GFP fusion constructs to regulate its activity with doxycyclin. heK293t cells were co-transfected with pC99-tetOn, ptRe-GFP, pDsRed monomer, and either pCtrl or each cDNa for 24 h and then incubated with conditioned media containing 100 ng/ ml doxycycline (Sigma-aldrich) for another 24 h. Once C99-rtta is cleaved by γ-secretase, the cleavage product aICD-rtta is transported into the nucleus and induces GFP expression through tRe in the presence of doxycyclin.…”

“…Compared to control, the putative positive cDNa clones which significantly increased green fluorescence under fluorescence microscope (Olympus) were isolated. after the primary screening, the secondary screening was conducted using pC99-GVP and pUaS-luciferase reporter assay [27]. after confirming the stimulatory effect on the reporter activity, the putative positive cDNa clones were tested for its stimulatory effect on aβ generation using sandwich eLISa kit.…”

“…[27,28]. heK293t, heLa, ChO-7Pa2 cells, and stable cells were cultured in Dulbecco's Modified eagle Medium (DMeM) (hyClone, Sh30243.01) supplemented with 10 % fetal bovine serum (hyClone, Sh30919.03), and 50 μg/ml Gentamicin (GIBCO, 15750-060) at 37 °C under 5 % CO 2 (v/v) condition.…”

“…[27]. heK293t cells were cotransfected with pC99-GVP, pUaS-Luciferase, pβ-galactosidase, and experimental control genes with or…”