ARL6IP1 mediates small-molecule-induced alleviation of Alzheimer pathology through FXR1-dependent BACE1 translation initiation

Abstract

Exploring the potential lead compounds for Alzheimer’s disease (AD) remains one of the challenging tasks. Here, we report that the plant extract conophylline (CNP) impeded amyloidogenesis by preferentially inhibiting BACE1 translation via the 5′ untranslated region (5′UTR) and rescued cognitive decline in an animal model of APP/PS1 mice. ADP-ribosylation factor–like protein 6–interacting protein 1 (ARL6IP1) was then found to mediate the effect of CNP on BACE1 translation, amyloidogenesis, glial activation, and cognitive function. Through analysis of the 5′UTR-targetd RNA-binding proteins by RNA pulldown combined with LC-MS/MS, we found that FMR1 autosomal homolog 1 (FXR1) interacted with ARL6IP1 and mediated CNP-induced reduction of BACE1 by regulating the 5′UTR activity. Without altering the protein levels of ARL6IP1 and FXR1, CNP treatment promoted ARL6IP1 interaction with FXR1 and inhibited FXR1 binding to the 5′UTR both in vitro and in vivo. Collectively, CNP exhibited a therapeutic potential for AD via ARL6IP1. Through pharmacological manipulation, we uncovered a dynamic interaction between FXR1 and the 5′UTR in translational control of BACE1, adding to the understanding of the pathophysiology of AD.

SHMT2 Mediates Small‐Molecule‐Induced Alleviation of Alzheimer Pathology Via the 5′UTR‐dependent ADAM10 Translation Initiation

“…Using luciferase‐based high‐throughput screenings, we have previously reported that some small molecules regulate amyloidogenesis, [ 16 ] which leads to the finding of kenpaullone (KEN) in the present study. We define that KEN promotes the 5′ untranslated region (5′UTR)‐dependent ADAM10 translation and alleviates amyloidogenesis in APP/PS1 mice, an animal model of AD.…”

“…Transcription inhibitor actinomycin D (ActD) or protein synthesis inhibitor cycloheximide (CHX) alone led to a reduced ADAM10 protein level, [ 26 ] whereas KEN‐induced ADAM10 enhancement was diminished in the presence of CHX but not ActD (Figure 2B ), suggesting an involvement of protein synthesis. It seemed that protein degradation machinery was not involved in this regulation, as the proteasomal inhibitor MG132 or the lysosomal inhibitor chloroquine (CQ) [ 16a ] failed to block KEN‐mediated augmentation of ADAM10 (Figure 2C ). Moreover, we excluded the possibility that CDKs/GSK‐3 played a role in ADAM10 regulation, as silencing of CDK5 or GSK‐3β alone did not change ADAM10 protein under basal condition and failed to further prevent KEN‐induced enhancement of ADAM10 protein levels (Figure 2D,E ).…”

“…It is reported that the small molecule Glycyrrhetinic acid (GA) directly binds to SHMT2 and suppresses mitochondrial energy metabolisms, [ 37 ] whereas another compound Cosmosiin enhances ADAM10 protein level via the 5′UTR‐dependent mechanism by our prior report. [ 16a ] To prove the effect of KEN on ADAM10 and the 5′UTR, we assessed ADAM10 and SHMT2 protein levels in SH‐SY5Y cells treated with KEN (0.75 µM for 36 h), in the absence or presence of SHMT2 inhibitor GA (100 µM) or Cosmosiin (Cos, 5 µM). As shown in Figure 4I , GA treatment significantly reduced the protein level of ADAM10, and further blocked KEN‐induced augmentation of ADAM10 protein.…”

“…HEK‐APP cells and SH‐SY5Y‐APP cells (HEK‐293 or SH‐SY5Y cells stably expressing full‐length human amyloid‐beta precursor protein 695) were generated as previously described. [ 16 , 26 ] Cells were maintained in the DMEM/F12 or DMEM medium (Gibco), supplemented with 10% fetal bovine serum (Biological Industries) and 1% penicillin/streptomycin (Thermo Fisher Scientific). Primary hippocampal neurons were extracted and cultured as described previously.…”

“…Soluble extracellular proteins and insoluble material extraction were isolated as described previously. [ 16b ] Cell lysates were extracted using RIPA buffer (Beyotime, Haimen, China). sAPPα was extracted according to the protocol described previously.…”