Cholesterol and metal ions in Alzheimer's disease

Cholesterol and metal ions have been suggested to be associated with the onset and progression of Alzheimer's disease (AD). Moreover, recent findings have demonstrated a potential interconnection between these two factors. For example, (a) cholesterol has been shown to be misregulated in AD-afflicted brains, and the aberrant activity of proteins (particularly, apolipoprotein E (ApoE) and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (HMGR)) has been linked to cholesterol-related AD exacerbation; (b) dyshomeostasis of metal ions associated with misfolded proteins (i.e., amyloid-?? (A??) aggregates) found in the brains of AD patients is shown to promote oxidative stress leading to the malfunction of multiple proteins, including cytochrome c oxidase (CcO), and Cu/Zn superoxide dismutase (SOD1); (c) metal ion misregulation has also been observed to disrupt the activity of proteins (e.g., HMGR, low-density lipoproteins (LDL)), required for cholesterol production and regulation. Herein, we briefly discuss the potential involvement of cholesterol and metal ions in AD neuropathogenesis in both individual and interrelated manners.close2

A small molecule that displays marked reactivity toward copper-versus zinc-amyloid-?? implicated in Alzheimer's disease

Alzheimer's disease (AD) is a complex, multifactorial, neurodegenerative disease that poses tremendous difficulties in pinpointing its precise etiology. A toolkit, which specifically targets and modulates suggested key players, may elucidate their roles in disease onset and progression. We report high-resolution insights on the activity of a small molecule (L2-NO) which exhibits reactivity toward Cu(II)-amyloid-?? (A??) over Zn(II)-A??.close3

Precision Targeting of BFL-1/A1 and an ATM Co-dependency in Human Cancer

Summary: Cancer cells overexpress a diversity of anti-apoptotic BCL-2 family proteins, such as BCL-2, MCL-1, and BFL-1/A1, to enforce cellular immortality. Thus, intensive drug development efforts have focused on targeting this class of oncogenic proteins to overcome treatment resistance. Whereas a selective BCL-2 inhibitor has been FDA approved and several small molecule inhibitors of MCL-1 have recently entered phase I clinical testing, BFL-1/A1 remains undrugged. Here, we developed a series of stapled peptide design principles to engineer a functionally selective and cell-permeable BFL-1/A1 inhibitor that is specifically cytotoxic to BFL-1/A1-dependent human cancer cells. Because cancers harbor a diversity of resistance mechanisms and typically require multi-agent treatment, we further investigated BFL-1/A1 co-dependencies by mining a genome-scale CRISPR-Cas9 screen. We identified ataxia-telangiectasia-mutated (ATM) kinase as a BFL-1/A1 co-dependency in acute myeloid leukemia (AML), which informed the validation of BFL-1/A1 and ATM inhibitor co-treatment as a synergistic approach to subverting apoptotic resistance in cancer. : Guerra et al. constructed an exquisitely selective BFL-1 inhibitor capable of covalent BFL-1 targeting and cellular penetrance without membrane disruption. Mining a genetic dependency database revealed a spectrum of BFL-1 dependency in cancer and an ATM co-dependency in AML, prompting the combination of BFL-1 and ATM inhibitors to achieve synergistic cytotoxicity. Keywords: BFL-1, A1, BCL-2 family, apoptosis, stapled peptide, covalent inhibitor, dependency, ATM, AML, cance

Importance of the Dimethylamino Functionality on a Multifunctional Framework for Regulating Metals, Amyloid-beta, and Oxidative Stress in Alzheimer's Disease

The complex and multifaceted pathology of Alzheimer's disease (AD) continues to present a formidable challenge to the establishment of long-term treatment strategies. Multifunctional compounds able to modulate the reactivities of various pathological features, such as amyloid-?? (A??) aggregation, metal ion dyshomeostasis, and oxidative stress, have emerged as a useful tactic. Recently, an incorporation approach to the rational design of multipurpose small molecules has been validated through the production of a multifunctional ligand (ML) as a potential chemical tool for AD. In order to further the development of more diverse and improved multifunctional reagents, essential pharmacophores must be identified. Herein, we report a series of aminoquinoline derivatives (AQ1-4, AQP1-4, and AQDA1-3) based on ML's framework, prepared to gain a structure-reactivity understanding of ML's multifunctionality in addition to tuning its metal binding affinity. Our structure-reactivity investigations have implicated the dimethylamino group as a key component for supplying the antiamyloidogenic characteristics of ML in both the absence and presence of metal ions. Two-dimensional NMR studies indicate that structural variations of ML could tune its interaction sites along the A?? sequence. In addition, mass spectrometric analyses suggest that the ability of our aminoquinoline derivatives to regulate metal-induced A?? aggregation may be influenced by their metal binding properties. Moreover, structural modifications to ML were also observed to noticeably change its metal binding affinities and metal-to-ligand stoichiometries that were shown to be linked to their antiamyloidogenic and antioxidant activities. Overall, our studies provide new insights into rational design strategies for multifunctional ligands directed at regulating metal ions, A??, and oxidative stress in AD and could advance the development of improved next-generation multifunctional reagents.clos

Amyloid-beta adopts a conserved, partially folded structure upon binding to zwitterionic lipid bilayers prior to amyloid formation

Aggregation at the neuronal cell membrane's lipid bilayer surface is implicated in amyloid-?? (A??) toxicity associated with Alzheimer's disease; however, structural and mechanistic insights into the process remain scarce. We have identified a conserved binding mode of A??40 on lipid bilayer surfaces with a conserved helix containing the self-recognition site (K16-E22).close

Importance of the Dimethylamino Functionality on a Multifunctional Framework for Regulating Metals, Amyloid-β, and Oxidative Stress in Alzheimer’s Disease

The complex and multifaceted pathology of Alzheimer’s disease (AD) continues to present a formidable challenge to the establishment of long-term treatment strategies. Multifunctional compounds able to modulate the reactivities of various pathological features, such as amyloid-β (Aβ) aggregation, metal ion dyshomeostasis, and oxidative stress, have emerged as a useful tactic. Recently, an incorporation approach to the rational design of multipurpose small molecules has been validated through the production of a multifunctional ligand (<b>ML</b>) as a potential chemical tool for AD. In order to further the development of more diverse and improved multifunctional reagents, essential pharmacophores must be identified. Herein, we report a series of aminoquinoline derivatives (<b>AQ1</b>–<b>4</b>, <b>AQP1</b>–<b>4</b>, and <b>AQDA1</b>–<b>3</b>) based on <b>ML</b>’s framework, prepared to gain a structure–reactivity understanding of <b>ML</b>’s multifunctionality in addition to tuning its metal binding affinity. Our structure–reactivity investigations have implicated the dimethylamino group as a key component for supplying the antiamyloidogenic characteristics of <b>ML</b> in both the absence and presence of metal ions. Two-dimensional NMR studies indicate that structural variations of <b>ML</b> could tune its interaction sites along the Aβ sequence. In addition, mass spectrometric analyses suggest that the ability of our aminoquinoline derivatives to regulate metal-induced Aβ aggregation may be influenced by their metal binding properties. Moreover, structural modifications to <b>ML</b> were also observed to noticeably change its metal binding affinities and metal-to-ligand stoichiometries that were shown to be linked to their antiamyloidogenic and antioxidant activities. Overall, our studies provide new insights into rational design strategies for multifunctional ligands directed at regulating metal ions, Aβ, and oxidative stress in AD and could advance the development of improved next-generation multifunctional reagents

A Redox-Active, Compact Molecule for Cross-Linking Amyloidogenic Peptides into Nontoxic, Off-Pathway Aggregates: In Vitro and In Vivo Efficacy and Molecular Mechanisms

Chemical reagents targeting and controlling amyloidogenic peptides have received much attention for helping identify their roles in the pathogenesis of protein-misfolding disorders. Herein, we report a novel strategy for redirecting amyloidogenic peptides into nontoxic, off-pathway aggregates, which utilizes redox properties of a small molecule (DMPD, N,N-dimethyl-p-phenylenediamine) to trigger covalent adduct formation with the peptide. In addition, for the first time, biochemical, biophysical, and molecular dynamics simulation studies have been performed to demonstrate a mechanistic understanding for such an interaction between a small molecule (DMPD) and amyloid-?? (A??) and its subsequent anti-amyloidogenic activity, which, upon its transformation, generates ligand-peptide adducts via primary amine-dependent intramolecular cross-linking correlated with structural compaction. Furthermore, in vivo efficacy of DMPD toward amyloid pathology and cognitive impairment was evaluated employing 5xFAD mice of Alzheimer???s disease (AD). Such a small molecule (DMPD) is indicated to noticeably reduce the overall cerebral amyloid load of soluble A?? forms and amyloid deposits as well as significantly improve cognitive defects in the AD mouse model. Overall, our in vitro and in vivo studies of DMPD toward A?? with the first molecular-level mechanistic investigations present the feasibility of developing new, innovative approaches that employ redox-active compounds without the structural complexity as next-generation chemical tools for amyloid management.close

Reduced lipid bilayer thickness regulates the aggregation and cytotoxicity of amyloid-??

The aggregation of amyloid-?? (A??) on lipid bilayers has been implicated as a mechanism by which A?? exerts its toxicity in Alzheimer&apos;s disease (AD). Lipid bilayer thinning has been observed during both oxidative stress and protein aggregation in AD, but whether these pathological modifications of the bilayer correlate with A?? misfolding is unclear. Here, we studied peptide-lipid interactions in synthetic bilayers of the short-chain lipid dilauroyl phosphatidylcholine (DLPC) as a simplified model for diseased bilayers to determine their impact on A?? aggregate, protofibril, and fibril formation. A?? aggregation and fibril formation in membranes composed of dioleoyl phosphatidylcholine (DOPC) or 1- palmitoyl-2-oleoyl phosphatidylcholine mimicking normal bilayers served as controls. Differences in aggregate formation and stability were monitored by a combination of thioflavin-T fluorescence, circular dichroism, atomic force microscopy, transmission electron microscopy, and NMR. Despite the ability of all three lipid bilayers to catalyze aggregation, DLPC accelerates aggregation at much lower concentrations and prevents the fibrillation of A?? at low micromolar concentrations. DLPC stabilized globular, membrane-associated oligomers, which could disrupt the bilayer integrity. DLPC bilayers also remodeled preformed amyloid fibrils into a pseudo-unfolded, molten globule state, which resembled on-pathway, protofibrillar aggregates. Whereas the stabilized, membrane-associated oligomers were found to be nontoxic, the remodeled species displayed toxicity similar to that of conventionally prepared aggregates. These results provide mechanistic insights into the roles that pathologically thin bilayers may play in A?? aggregation on neuronal bilayers, and pathological lipid oxidation may contribute to A?? misfolding.clos

Multifunctional quinoline-triazole derivatives as potential modulators of amyloid-?? peptide aggregation

Metal ion dyshomeostasis is hypothesized to play a role in the toxicity and aggregation of the amyloid beta (A??) peptide, contributing to Alzheimer&apos;s disease (AD) pathology. We report on the synthesis and metal complexation ability of three bidentate quinoline-triazole derivatives 3-(4-(quinolin-2-yl)-1H-1,2,3-triazol-1-yl)propan-1-ol (QOH), 4-(2-(4-(quinolin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)morpholine (QMorph), and 4-(2-(4-(quinolin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)thiomorpholine (QTMorph). We further study the utility of these ligands to modulate A?? peptide aggregation processes in the presence and absence of Cu2+ ions. Ligand-peptide interactions were first investigated using both 2-D 1H-15N band-selective optimized flip angle short transient heteronuclear multiple quantum correlation (SOFAST-HMQC) NMR spectroscopy and molecular modeling techniques, indicating interactions with glutamic acid (E3) and several residues in the hydrophobic region of A??. Native gel electrophoresis with western blotting along with transmission electron microscopy provided information on the ability of each ligand to modulate A?? aggregation. While the ligands alone did not modify A?? peptide aggregation at the 24h timepoint, signifying relatively weak ligand-peptide interactions, the ligands did modify the aggregation profile of the peptide in the presence of stoichiometric and suprastoichiometric Cu. Interestingly, the thioether derivative QTMorph exhibited the most pronounced effect on peptide aggregation in the presence of Cu. Overall, the quinoline-triazole ligand series were shown to interact with the hydrophobic region of the A?? peptide, and modulate the Cu-A?? aggregation processclos