Inhibition of GSK3β-mediated BACE1 expression reduces Alzheimer-associated phenotypes
Philip T.T. Ly, Yili Wu, Haiyan Zou, Ruitao Wang, Weihui Zhou, Ayae Kinoshita, Mingming Zhang, Yi Yang, Fang Cai, James Woodgett, Weihong Song
Philip T.T. Ly, Yili Wu, Haiyan Zou, Ruitao Wang, Weihui Zhou, Ayae Kinoshita, Mingming Zhang, Yi Yang, Fang Cai, James Woodgett, Weihong Song
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Research Article Neuroscience

Inhibition of GSK3β-mediated BACE1 expression reduces Alzheimer-associated phenotypes

Abstract

Deposition of amyloid β protein (Aβ) to form neuritic plaques in the brain is the pathological hallmark of Alzheimer’s disease (AD). Aβ is generated from sequential cleavages of the β-amyloid precursor protein (APP) by the β- and γ-secretases, and β-site APP-cleaving enzyme 1 (BACE1) is the β-secretase essential for Aβ generation. Previous studies have indicated that glycogen synthase kinase 3 (GSK3) may play a role in APP processing by modulating γ-secretase activity, thereby facilitating Aβ production. There are two highly conserved isoforms of GSK3: GSK3α and GSK3β. We now report that specific inhibition of GSK3β, but not GSK3α, reduced BACE1-mediated cleavage of APP and Aβ production by decreasing BACE1 gene transcription and expression. The regulation of BACE1 gene expression by GSK3β was dependent on NF-κB signaling. Inhibition of GSK3 signaling markedly reduced Aβ deposition and neuritic plaque formation, and rescued memory deficits in the double transgenic AD model mice. These data provide evidence for regulation of BACE1 expression and AD pathogenesis by GSK3β and that inhibition of GSK3 signaling can reduce Aβ neuropathology and alleviate memory deficits in AD model mice. Our study suggests that interventions that specifically target the β-isoform of GSK3 may be a safe and effective approach for treating AD.

Authors

Philip T.T. Ly, Yili Wu, Haiyan Zou, Ruitao Wang, Weihui Zhou, Ayae Kinoshita, Mingming Zhang, Yi Yang, Fang Cai, James Woodgett, Weihong Song

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Figure 4

GSK3β regulation of BACE1 transcription is dependent on NF-κB p65 expression.

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GSK3β regulation of BACE1 transcription is dependent on NF-κB p65 expres...
(A) pBACE1-4NF-κB plasmid contains the 4 NF-κB cis-elements from the human BACE1 promoter upstream of the firefly luciferase reporter gene. N2a cells were co-transfected with pBACE1-4NF-κB and pCMV-RLuc. Transfected cells were treated with vehicle solution (control) or 10 ng/ml TNF-α with/without 5 μM ARA for 24 hours. (B) N2a cells were co-transfected with pBACE1-4NF-κB plasmid and pMTF-p65 or a vector control. Transfected cells were then treated with a vehicle solution or 5 μM ARA for 24 hours. (C) pNF-κB-Luc was co-transfected with pMTF-p65 or a vector control and treated with a vehicle solution or 5 μM ARA for 24 hours. Renilla luciferase was used to normalize for transfection efficiency. Values are expressed as mean ± SEM. n = 4; *P < 0.05, **P < 0.01, ***P < 0.001, Student’s t test. (D) Wild-type MEFs and RelA-KO MEFs which are dysfunctional for NF-κB activity, were co-transfected with a 3.5-kb human BACE1 promoter and S9A-GSK3β or a control vector. S9A-GSK3β overexpression in MEFs. significantly increased luciferase activity (*P < 0.05, Student’s t test), whereas RelA-KO MEFs did not have any significant effect. Luciferase activity is indicative of BACE1 promoter activity. All promoter data shown represent an average of at least 4 independent experiments, with each condition performed in triplicate. (E) N2a cells were treated with 5 μM ARA for 24 hours, followed by cell fractionation. Cytosolic and nuclear fractions were subjected to SDS-PAGE. ARA treatment significantly reduced NF-κB p65 levels in the (F) nuclear fraction (n = 6; **P < 0.001, Student’s t test) and (G) cytosolic fraction. n = 6; ***P < 0.001, Student’s t test. Values are expressed as mean ± SEM.