Browsing by Author "Bandyopadhyay, Sanghamitra"

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    The alpha-synuclein 5'untranslated region targeted translation blockers: anti-alpha synuclein efficacy of cardiac glycosides and Posiphen
    (Springer Nature, 2011-03) Rogers, Jack T.; Mikkilineni, Sohan; Castelvetri, Ippolita Cantuti; Smith, Deborah H.; Huang, Xudong; Bandyopadhyay, Sanghamitra; Cahill, Catherine M.; Maccecchini, Maria L.; Lahiri, Debomoy K.; Greig, Nigel H.; Psychiatry, School of Medicine
    Increased brain α-synuclein (SNCA) protein expression resulting from gene duplication and triplication can cause a familial form of Parkinson's disease (PD). Dopaminergic neurons exhibit elevated iron levels that can accelerate toxic SNCA fibril formation. Examinations of human post mortem brain have shown that while mRNA levels for SNCA in PD have been shown to be either unchanged or decreased with respect to healthy controls, higher levels of insoluble protein occurs during PD progression. We show evidence that SNCA can be regulated via the 5'untranslated region (5'UTR) of its transcript, which we modeled to fold into a unique RNA stem loop with a CAGUGN apical loop similar to that encoded in the canonical iron-responsive element (IRE) of L- and H-ferritin mRNAs. The SNCA IRE-like stem loop spans the two exons that encode its 5'UTR, whereas, by contrast, the H-ferritin 5'UTR is encoded by a single first exon. We screened a library of 720 natural products (NPs) for their capacity to inhibit SNCA 5'UTR driven luciferase expression. This screen identified several classes of NPs, including the plant cardiac glycosides, mycophenolic acid (an immunosuppressant and Fe chelator), and, additionally, posiphen was identified to repress SNCA 5'UTR conferred translation. Western blotting confirmed that Posiphen and the cardiac glycoside, strophanthidine, selectively blocked SNCA expression (~1 μM IC(50)) in neural cells. For Posiphen this inhibition was accelerated in the presence of iron, thus providing a known APP-directed lead with potential for use as a SNCA blocker for PD therapy. These are candidate drugs with the potential to limit toxic SNCA expression in the brains of PD patients and animal models in vivo.
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    Novel 5' Untranslated Region Directed Blockers of Iron- Regulatory Protein-1 Dependent Amyloid Precursor Protein Translation: Implications for Down Syndrome and Alzheimer’s Disease
    (Public Library of Science, 2013-07-31) Bandyopadhyay, Sanghamitra; Cahill, Catherine; Balleidier, Amelie; Huang, Conan; Lahiri, Debomoy K.; Huang, Xudong; Rogers, Jack T.; Psychiatry, School of Medicine
    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.
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    Novel drug targets based on metallobiology of Alzheimer's disease
    (Taylor & Francis, 2010-11) Bandyopadhyay, Sanghamitra; Huang, Xudong; Lahiri, Debomoy K.; Rogers, Jack T.; Psychiatry, School of Medicine
    IMPORTANCE OF THE FIELD: Increased localization of Zn, Fe, Cu and Al within the senile plaques (SP) exacerbates amyloid beta (Aβ)-mediated oxidative damage, and acts as catalyst for Aβ aggregation in Alzheimer's disease (AD). Thus, disruption of aberrant metal-peptide interactions via chelation therapy holds considerable promise as a rational therapeutic strategy against Alzheimer's amyloid pathogenesis. AREAS COVERED IN THIS REVIEW: The complexities of metal-induced genesis of SP are reviewed. The recent advances in the molecular mechanism of action of metal chelating agents are discussed with critical assessment of their potential to become drugs. WHAT THE READER WILL GAIN: Taking into consideration the interaction of metals with the metal-responsive elements on the Alzheimer's amyloid precursor protein (APP), readers will gain understanding of several points to bear in mind when developing a screening campaign for AD-therapeutics. TAKE HOME MESSAGE: A functional iron-responsive element (IRE) RNA stem loop in the 5' untranslated region (UTR) of the APP transcript regulates neural APP translation. Desferrioxamine, clioquinol, tetrathiolmolybdate, dimercaptopropanol, VK-28, and natural antioxidants, such as curcumin and ginko biloba need critical evaluation as AD therapeutics. There is a necessity for novel screens (related to metallobiology) to identify therapeutics effective in AD.