Novel 5′ Untranslated Region Directed Blockers of Iron-Regulatory Protein-1 Dependent Amyloid Precursor Protein Translation: Implications for Down Syndrome and Alzheimer's Disease
Authors: Xudong Huang
Jack T Rogers
Sanghamitra Bandyopadhyay
Amelie Balleidier
Debomoy K Lahiri
Catherine Cahill
Conan Huang
Journal: PLoS ONE (2013)
Discipline: Multidisciplinary
Keywords: iron influx; translational expression; amyloid precursor protein (APP); iron efflux; iron-regulatory protein-1 (IRP1)
Affiliations: Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA.

Abstract:  We reported that iron influx drives the translational expression of the neuronal amyloid precursor protein (APP), which has a role in iron efflux. This is via a classic release of repressor interaction of APP mRNA with iron-regulatory protein-1 (IRP1) whereas IRP2 controls the mRNAs encoding the L- and H-subunits of the iron storage protein, ferritin. Here, we identified thirteen potent APP translation blockers that acted selectively towards the uniquely configured iron-responsive element (IRE) RNA stem loop in the 5' untranslated region (UTR) of APP mRNA. These agents were 10-fold less inhibitory of 5'UTR sequences of the related prion protein (PrP) mRNA. Western blotting confirmed that the 'ninth' small molecule in the series selectively reduced neural APP production in SH-SY5Y cells at picomolar concentrations without affecting viability or the expression of α-synuclein and ferritin. APP blocker-9 (JTR-009), a benzimidazole, reduced the production of toxic Aβ in SH-SY5Y neuronal cells to a greater extent than other well tolerated APP 5'UTR-directed translation blockers, including posiphen, that were shown to limit amyloid burden in mouse models of Alzheimer's disease (AD). RNA binding assays demonstrated that JTR-009 operated by preventing IRP1 from binding to the IRE in APP mRNA, while maintaining IRP1 interaction with the H-ferritin IRE RNA stem loop. Thus, JTR-009 constitutively repressed translation driven by APP 5'UTR sequences. Calcein staining showed that JTR-009 did not indirectly change iron uptake in neuronal cells suggesting a direct interaction with the APP 5'UTR. These studies provide key data to develop small molecules that selectively reduce neural APP and Aβ production at 10-fold lower concentrations than related previously characterized translation blockers. Our data evidenced a novel therapeutic strategy of potential impact for people with trisomy of the APP gene on chromosome 21, which is a phenotype long associated with Down syndrome (DS) that can also cause familial Alzheimer's disease. 

Retracted: No

PubPeer comments:
 Reuse of the same IRP2 band in two different experiments in Figure 5. ![file] , 
 First authoru2019s comment Thank you for indicating the above issue. However, I declare that neither this experiment nor any of the immunoblots have been done by me, which the corresponding author is aware of. Moreover, presently the corresponding author is looking into the matter and would take the appropriate measure. Sanghamitra Bandyopadhyay , 
 Dear Dr. Bandyopadhyay and other co-authors, could you please provide us with an update? Although I am not the same person as Sirhookera in comment #1, I did report the same concern to the journal more than five years ago, in October 2015. It would be appreciated if you could tell us what you did to address this concern in the past years. , 
 #3 Thanks Dr Bik for the concern. However, as declared earlier, I reiterate that neither this experiment nor any of the immunoblots in question had been done by me (first author), which the corresponding author is well aware of. Nonetheless, we, the authors, had a detailed discussion on this matter, and raw data for the blots are in place to address this inadvertent error. Since reminded, I am thankful about it and would positively check with the updates on this matter. Subsequently, the corresponding author would take the necessary measures. Dr Bandyopadhyay , 
 Thanks Dr. Bik for your comment. Like the first author, I am not responsible for the experiment and data in question. But I ve alerted the corresponding author who would respond to your comment. , 
 Thanks Dr. Bik for your message. I declare that I have not performed the experiments and, consequently data in question. I discussed the matter with other coauthors and the corresponding author, who will respond to you. , 
 Many thanks Dr. Bik and colleagues for urging our attention to this matter of IRP2 blots in this PLOS ONE paper. We have contacted the PLoS-ONE journal and the corrections are being taken care of immediately. These listed corrections are for the IRP2 levels shown in response to the drug JTR-009 in the lower panels figure 5B C . These points were discussed with the first and other authors last year and the full IRP2 blots are ready for the journal. We appreciate everyones input. ,