Peptide Aggregation Research Articles

The Features of Beta-Amyloid Phosphorylation in Alzheimer’s Disease

Accumulation of neurotoxic aggregates of beta-amyloid peptides (Aβ) is a hallmark of Alzheimer’s disease (AD) progression. Post-translational modifications (PTMs) increase Aβ aggregation and cytotoxicity, and the content of specific Aβ proteoforms is elevated in senile plaques of AD patients. The pathophysiological mechanisms of aggregate formation and the role of Aβ proteoforms need thorough study both to understand the role played by specific processes in the initiation of neuronal degradation and to find effective preventive means of therapeutic action. The present work investigates the dynamics of accumulation of phosphorylated serine-8 proteoform Aβ (pSer8-Aβ) using the 5xFAD mouse amyloid model. Aβ samples from human cerebrospinal fluid (CSF) and brain were also investigated. Western blot studies using 1E4E11 and 4G8 antibodies showed that accumulation of pSer8-Aβ in mouse brain starts as early as at the age of 3 months and reaches a maximum by the age of 14–17 months, which is generally similar to the dynamics of accumulation of the total pool of Aβ peptides. The pSer8-Aβ level in human CSF in AD patients can reach ~ 1–10% of the total amount of Aβ. Mass spectrometric analysis showed that Aβ phosphorylation by the Ser8, Tyr10, and Ser26 residues in brain tissues, as well as phosphorylation of the APP by Thr719 residue, is possible. These findings support the assumption that pSer8-Aβ proteoforms are involved in amyloidosis in AD.

Novel Piperazine Based Compounds Target Alzheimer's Disease Relevant Amyloid β42 and Tau Derived Peptide AcPHF6, and the Lead Molecule Increases Viability in the Flies Expressing Human Tau Protein.

Alzheimer's disease (AD) is the leading form of dementia in the United States and the world. The pathophysiology of AD is complex and multifaceted. Accumulation of senile plaques and neurofibrillary tangles (NFTs) are hallmarks of AD. The aggregation of amyloid β (senile plaques) and tau tangles (NFTs) results in the death of neurons in the cortex and hippocampus, which manifests itself in cognitive decline and memory loss. Current therapies rely on conventional approaches that have only treated the underlying symptoms without disease modification. Data from clinical studies point to a complex role of amyloid β (Aβ) in a way that enhances the tau phenotype throughout the disease process. To address the co-pathogenic role of Aβ and tau, we undertook development of multitarget compounds aiming at both tau and Aβ to slow or stop disease progression and provide neuroprotection. Here, we demonstrate a dose-dependent effect of the novel test compounds that inhibit aggregation of AcPHF6 (a shorter version of tau protein) and Aβ1-42 peptides in thioflavin T fluorescent assays. The compounds were also shown to disaggregate preformed aggregates dose dependently. To further validate these findings, circular dichroism experiments were carried out to examine the nature of inhibition. Additionally, transmission electron microscopy experiments were carried out to gain insights into the morphologies of aggregates obtained from dose-dependent inhibition of AcPHF6 and Aβ1-42 as well as dissociation of preformed aggregates from these peptides. Compounds D-687 and D-688 reversed Aβ1-42 induced toxicity in SH-SH5Y cells, significantly demonstrating neuroprotective properties. Finally, in a study with Drosophila melanogaster expressing human tau protein isoform (2N4R) in all the neurons, compound D-688 significantly increased the survival of flies compared to vehicle treated controls. Future studies will further examine the neuroprotective properties of these lead compounds in various animal models.

Molecular dynamics simulations unveil the aggregation patterns and salting out of polyarginines at zwitterionic POPC bilayers in solutions of various ionic strengths

This study employs molecular dynamics (MD) simulations to investigate the adsorption and aggregation behavior of simple polyarginine cell-penetrating peptides (CPPs), specifically modeled as R9 peptides, at zwitterionic phosphocholine POPC membranes under varying ionic strengths of two peptide concentrations and two concentrations of NaCl and CaCl2. The results reveal an intriguing phenomenon of R9 aggregation at the membrane, which is dependent on the ionic strength, indicating a salting-out effect. As the peptide concentration and ionic strength increase, peptide aggregation also increases, with aggregate lifetimes and sizes showing a corresponding rise, accompanied by the total decrease of adsorbed peptides at the membrane surface. Notably, in high ionic strength environments, large R9 aggregates, such as octamers, are also observed occasionally. The salting-out, typically uncommon for short positively charged peptides, is attributed to the unique properties of arginine amino acid, specifically by its side chain containing amphiphilic guanidinium (Gdm+) ion which makes both intermolecular hydrophobic like-charge Gdm+ – Gdm+ and salt-bridge Gdm+ – C-terminus interactions, where the former are increased with the ionic strength, and the latter decreased due to electrostatic screening. The aggregation behavior of R9 peptides at membranes can also be linked to their CPP translocation properties, suggesting that aggregation may aid in translocation across cellular membranes.

Imidacloprid unique and repeated treatment produces cholinergic transmission disruption and apoptotic cell death in SN56 cells.

Imidacloprid (IMI), the most widely used worldwide neonicotinoid biocide, produces cognitive disorders after repeated and single treatment. However, little was studied about the possible mechanisms that produce this effect. Cholinergic neurotransmission regulates cognitive function. Most cholinergic neuronal bodies are present in the basal forebrain (BF), regulating memory and learning process, and their dysfunction or loss produces cognition decline. BF SN56 cholinergic wild-type or acetylcholinesterase (AChE), β-amyloid-precursor-protein (βAPP), Tau, glycogen-synthase-kinase-3-beta (GSK3β), beta-site-amyloid-precursor-protein-cleaving enzyme 1 (BACE1), and/or nuclear-factor-erythroid-2-related-factor-2 (NRF2) silenced cells were treated for 1 and 14 days with IMI (1 μM to 800 μM) with or without recombinant heat-shock-protein-70 (rHSP70), recombinant proteasome 20S (rP20S) and with or without N-acetyl-cysteine (NAC) to determine the possible mechanisms that mediate this effect. IMI treatment for 1 and 14 days altered cholinergic transmission through AChE inhibition, and triggered cell death partially through oxidative stress generation, AChE-S overexpression, HSP70 downregulation, P20S inhibition, and Aβ and Tau peptides accumulation. IMI produced oxidative stress through reactive oxygen species production and antioxidant NRF2 pathway downregulation, and induced Aβ and Tau accumulation through BACE1, GSK3β, HSP70, and P20S dysfunction. These results may assist in determining the mechanisms that produce cognitive dysfunction observed following IMI exposure and provide new therapeutic tools.

ApoE: The Non-Protagonist Actor in Neurological Diseases

Background: Apolipoprotein E (APOE = gene, ApoE = protein) is a glycoprotein involved in the biological process of lipid transportation and metabolism, contributing to lipid homeostasis. APOE has been extensively studied for its correlation with neurodegenerative diseases, in particular Alzheimer’s disease (AD), where the possession of the epsilon 4 (E4) allele is established as a risk factor for developing AD in non-familiar sporadic forms. Recently, evidence suggests a broad involvement of E4 also in other neurological conditions, where it has been shown to be a predictive marker for worse clinical outcomes in Parkinson’s disease (PD), brain trauma, and disturbances of consciousness. The mechanisms underlying these associations are complex and involve amyloid-β (Aβ) peptide accumulation and neuroinflammation, although many others have yet to be identified. Objectives: The aim of this review is to overview the current knowledge on ApoE as a non-protagonist actor in processes underlying neurodegenerative diseases and its clinical significance in AD, PD, acquired brain trauma, and Disorders of Consciousness (DoC). Ethical implications of genetic testing for APOE variants and information disclosure will also be briefly discussed.

Organic Chimeras based on Selenosugars, Steroids, and Fullerenes as Potential Inhibitors of the β-amyloid Peptide Aggregation.

The aggregation of β-amyloid peptide (Aβ) is associated with neurodegenerative diseases such as Alzheimer's disease (AD). Several therapies aimed at reducing the aggregation of this peptide have emerged as potential strategies for the treatment of AD. This paper describes the design and preparation of new hybrid molecules based on steroids, selenosugars, and [60]fullerene as potential inhibitors of Aβ oligomerization. These moieties were selected based on their antioxidant properties and possible areas of interaction with the Aβ. Cyclopropanations between C60 and malonates bearing different steroid and selenosugar moieties using the Bingel-Hirsch protocol have enabled the synthesis of functionalized molecular hybrids. The obtained derivatives were characterized by physical and spectroscopic techniques. Theoretical calculations for all the selenium compounds were performed using the density functional theory DFT/B3LYP-D3(BJ)/6-311G(2d,p) predicting the most stable conformations of the synthesized derivatives. Relevant geometrical parameters were investigated to relate the stereochemical behavior and the spectroscopic data obtained. The affinity of the compounds for Aβ-peptide was estimated by molecular docking simulation, which predicted an increase in affinity and interactions for Aβ for the hybrids containing the C60 core. In addition, parameters such as lipophilicity, polar surface area, and dipole moment were calculated to predict their potential interaction with membrane cells.

Effect of the aggregation state of amyloid-beta (25-35) on the brain oxidative stress in vivo

Aggregation pathway of amyloid-β (25-35) in water affects the oxidative stress in the brain observed after administration of aggregated peptide in animals in vivo. Our studies on peptide aggregation ex situ prior to injection suggest that from the onset of peptide incubation in aqueous media, all samples exhibit the formation of fibril-like aggregates, characterized by a significant amount of β-sheets. This induces significant oxidative stress in vivo as observed for up to 60 min of peptide aggregation time. As the aggregation advances, the fibril-like aggregates become longer and intertwined, while the amount of β-sheets does not change significantly. An injection of such large, thick, and entangled aggregates in the animal brain results in a drastic increase in oxidative stress. This may be related to the number of activated microglia that initiate a sequence of inflammatory responses in the presence of large, highly interconnected fibrils.

Dual Role of Anionic Lipids in Amyloid Aggregation.

Neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's, affect millions worldwide and share a common feature: the aggregation of intrinsically disordered proteins into toxic oligomers that interact with cell membranes. In Alzheimer's disease (AD), amyloid-beta (Aβ) peptides accumulate and bind to plasma membranes, potentially disrupting cellular function. The complex interplay between amyloidogenic peptides and lipid membranes, particularly the role of anionic lipids, is crucial in disease pathogenesis but challenging to characterize experimentally. The literature presents conflicting results on the influence of anionic lipids on peptide aggregation kinetics, highlighting a knowledge gap. To address this, we used coarse-grained molecular dynamics (CG-MD) simulations to study interactions between a model amyloidogenic peptide, amyloid-β's K16LVFFAE22 fragment (Aβ16-22), and mixed lipid bilayers. We used phosphatidylserine (PS) and phosphatidylcholine (PC) as representative anionic and zwitterionic lipids, respectively, examining the mixed bilayer compositions of 0% PS-100% PC, 10% PS-90% PC, and 30% PS-70% PC. Our simulations revealed that membranes enriched in anionic lipids enhance peptide adsorption and interaction kinetics. The aggregation dynamics was modulated by two competing factors: increased local peptide concentration near negatively charged membranes, which promoted aggregation, and peptide-lipid interactions, which slowed it down. Higher percentages of anionic lipids led to smaller and more ordered aggregates and enhanced lipid demixing, leading to the formation of PS clusters. These findings contribute to understanding membrane-mediated peptide aggregation in neurodegenerative disorders, potentially guiding new therapeutic strategies targeting the early stages of protein aggregation in various neurodegenerative diseases.

Intra-cisterna-magna bevacizumab injection (ICM-BI) reproduces pathological alterations of cerebral small vessel diseases.

General modeling strategies for sporadic cerebral small blood vessel diseases (CSVDs) include limiting blood stream in large blood vessels and inducing systemic hypertension, in which small blood vessel deficit is either a secondary or concomitant pathology. In the current study, we introduce that intra-cisterna-magna Bevacizumab injection (ICM-BI) directly causes cerebral small blood vessel injury by neutralizing VEGF-A, the indispensable growth factor for angiogenesis. ICM-BI reproduces neuro-functional impairment, tight junction loss, cerebral micro-bleeds (CMBs), amyloid peptide accumulation, neuronal injury, white matter loss, and glial cell activation, which are common manifestations of sporadic CSVDs. Compared with existing CSVD models, small blood vessel injury is more prominent in the ICM-BI brain. Moreover, no significant alteration in large blood vessels or peripheral organs after ICM-BI is recorded. We thus propose that ICM-BI is a neat, economic and applicable methodology to establish murine sporadic CSVD model.

Disruption of PHF6 Peptide Aggregation from Tau Protein: Mechanisms of Palmatine Chloride in Preventing Early PHF6 Aggregation.

The formation of neurofibrillary tangles (NFTs), composed of tau protein aggregates, is a hallmark of neurodegenerative diseases known as tauopathies, including Alzheimer's disease (AD). NFTs consist of paired helical filaments (PHFs) of tau protein with a dominant β-sheet secondary structure. Within these PHFs, the PHF6 hexapeptide (Val306-Gln-Ile-Val-Tyr-Lys311) has been commonly highlighted as a key site for tau protein nucleation. Palmatine chloride (PC) has been identified as an inhibitor of PHF6 aggregation, capable of reducing aggregation propensity at submicromolar concentrations. In pursuit of novel anti-AD drugs targeting early tau aggregation stages, we conducted an in silico study to elucidate PC's mechanism of action during PHF6 aggregation. Our observations suggest that while PHF6 can still initiate self-aggregation in the presence of PC, PC molecules subtly influence PHF6 aggregation dynamics, favoring smaller aggregates over larger complexes. The study underlined the key roles of aromatic rings in PC binding to different PHF6 aggregates by interacting through π-π stacking with the PHF6 Tyr310 side chain. The presence of aromatic rings in compounds to be able to inhibit the earlier complexation phase seems to be essential. These in silico findings lay a foundation for the design of compounds that could intervene in resolving the neurotoxicity of protein aggregates in AD.

Unraveling the Molecular Jam: How Crowding Shapes Protein Aggregation in Neurodegenerative Disorders.

Protein misfolding and aggregation are the hallmarks of neurodegenerative diseases including Huntington's disease, Parkinson's disease, Alzheimer's disease, and prion diseases. A crowded cellular environment plays a crucial role in modulating protein aggregation processes in vivo and the pathological aggregation of proteins linked to different neurodegenerative disorders. Here, we review recent studies examining the effects of various crowding agents, such as polysaccharides, polyethylene glycol, and proteins like BSA and lysozyme on the behaviors of aggregation of several amyloidogenic peptides and proteins, including amylin, huntingtin, tau, α-synuclein, prion, and amyloid-β. We also summarize how the aggregation kinetics, thermodynamic stability, and morphology of amyloid fibrils are altered significantly in the presence of crowding agents. In addition, we also discuss the molecular basis underlying the modulation of amyloidogenic aggregation, focusing on changes in the protein conformation, and the nucleation mechanism. The molecular understanding of the effects of macromolecular crowding on amyloid aggregation is essential for revealing disease pathologies and identifying possible therapeutic targets. Thus, this review offers a perspective on the complex interplay between protein aggregation and the crowded cellular environment in vivo and explains the relevance of crowding in the context of neurodegenerative disorders.

A novel peptide-based tau aggregation inhibitor as a potential therapeutic for Alzheimer's disease and other tauopathies.

As aggregation underpins Tau toxicity, aggregation inhibitor peptides may have disease-modifying potential. They are therefore currently being designed and target either the 306VQIVYK311 aggregation-promoting hotspot found in all Tau isoforms or the 275VQIINK280 aggregation-promoting hotspot found in 4R isoforms. However, for any Tau aggregation inhibitor to potentially be clinically relevant for other tauopathies, it should target both hotspots to suppress aggregation of Tau isoforms, be stable, cross the blood-brain barrier, and rescue aggregation-dependent Tau phenotypes in vivo. We developed a retro-inverso, stable D-amino peptide, RI-AG03 [Ac-rrrrrrrrGpkyk(ac)iqvGr-NH2], based on the 306VQIVYK311 hotspots which exhibit these disease-relevant attributes. Unlike other aggregation inhibitors, RI-AG03 effectively suppresses aggregation of multiple Tau species containing both hotspots in vitro and in vivo, is non-toxic, and suppresses aggregation-dependent neurodegenerative and behavioral phenotypes. RI-AG03 therefore meets many clinically relevant requirements for an anti-aggregation Tau therapeutic and should be explored further for its disease-modifying potential for Tauopathies. Our manuscript describes the development of a novel peptide inhibitor of Tau aggregation, a retro-inverso, stable D-amino peptide called RI-AG03 that displays many clinically relevant attributes. We show its efficacy in preventing Tau aggregation in both in vitro and in vivo experimental models while being non-toxic to cells. RI-AG03 also rescues a biosensor cell line that stably expresses Tau repeat domains with the P301S mutation fused to Cer/Clo and rescues aggregation-dependent phenotypes in vivo, suppressing neurodegeneration and extending lifespan. Collectively our data describe several properties and attributes of RI-AG03 that make it a promising disease-modifying candidate to explore for reducing pathogenic Tau aggregation in Tauopathies such as Alzheimer's disease. Given the real interest in reducing Tau aggregation and the potential clinical benefit of using such agents in clinical practice, RI-AG03 should be investigated further for the treatment of Tauopathies after validation in mammalian models. Tau aggregation inhibitors are the obvious first choice as Tau-based therapies as much of Tau-mediated toxicity is aggregation dependent. Indeed, there are many research efforts focusing on this therapeutic strategy with aggregation inhibitors being designed against one of the two aggregation-promoting hotspots of the Tau protein. To our knowledge, RI-AG03 is the only peptide aggregation inhibitor that inhibits aggregation of Tau by targeting both aggregation-promoting hotspot motifs simultaneously. As such, we believe that our study will have a significant impact on drug discovery efforts in this arena.

Natural Compounds as Inhibitors of Aβ Peptide and Tau Aggregation.

Neurodegenerative conditions like Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) encompass disorders characterized by the degeneration of neurons in specific circumstances. The quest for novel agents to influence these diseases, particularly AD, has unearthed various natural compounds displaying multifaceted activities and diverse pharmacological mechanisms. Given the ongoing extensive study of pathways associated with the accumulation of neurofibrillary aggregates and amyloid plaques, this paper aims to comprehensively review around 130 studies exploring natural products. These studies focus on inhibiting the formation of amyloid plaques and tau protein tangles, with the objective of potentially alleviating or delaying AD.

Anti-viral Effects of Pavetta indica Methanolic Extract and Acyclovir on Behavioral and Biochemical Parameters in Streptozotocin-induced Alzheimer's Disease in Rats.

Alzheimer's disease is a neurological dysfunction of the brain caused by neurodegeneration and oxidative stress. Some viruses, such as herpes viruses, HSV-1, and HSV-2, are causative agents of Alzheimer's disease and result in β-amyloid peptide and tau protein accumulation in the brain. Some antiviral drugs, such as valacyclovir, acyclovir, and foscarnet, reduce amyloid-beta and P-tau. Pavetta indica leaves are also reported for their antiviral properties. The current study aimed to find out the significance of using Pavetta indica methanolic extract and acyclovir against Alzheimer's disease induced by streptozotocin. Wistar rats received acyclovir and Pavetta indica methanolic extract orally at different dose ranges (50, 150, 450 mg/kg) and (125, 250, 500 mg/kg), respectively. The standard therapy, Rivastigmine (2 mg/kg), was given orally. Intracerebroventricular-streptozotocin produced significant alternations in behavioral assessments, including locomotor activity test, Morris water maze test, and elevated plus maze test. Moreover, intracerebroventricular-streptozotocin ameliorated the antioxidant defense activity by decreasing levels of catalase, superoxide dismutase, and reduced glutathione while enhancing the oxidative stress markers, including malondialdehyde, and total nitrite levels. Finally, the main findings showed that intracerebroventricular-streptozotocin significantly increased the inflammatory marker, tumor necrosis factor-α, and disturbed neurotransmitter mediators, including levels of acetylcholinesterase, glutamate, and γ-amino butyric acid. In a dose-dependent manner, acyclovir and Pavetta indica methanolic extract treatments abrogated the streptozotocin-induced behavioral and neurological abnormalities in rats. The potential therapeutic effects of PIME and acyclovir administration in intracerebroventricular-streptozotocin-treated rats may be attributed to its potential antiviral, antioxidant, and anti-inflammatory effects. The current study suggests that Pavetta indica methanolic extract and acyclovir are promising therapeutic targets against Alzheimer's disease.

Aggregation of the amyloid-β peptide (Aβ40) within condensates generated through liquid–liquid phase separation

The deposition of the amyloid-β (Aβ) peptide into amyloid fibrils is a hallmark of Alzheimer’s disease. Recently, it has been reported that some proteins can aggregate and form amyloids through an intermediate pathway involving a liquid-like condensed phase. These observations prompted us to investigate the phase space of Aβ. We thus explored the ability of Aβ to undergo liquid–liquid phase separation, and the subsequent liquid-to-solid transition that takes place within the resulting condensates. Through the use of microfluidic approaches, we observed that the 40-residue form of Αβ (Αβ40) can undergo liquid–liquid phase separation, and that accessing a liquid-like intermediate state enables Αβ40 to self-assemble and aggregate into amyloid fibrils through this pathway. These results prompt further studies to investigate the possible role of Αβ liquid–liquid phase separation and its subsequent aggregation in the context of Alzheimer’s disease and more generally on neurodegenerative processes.

Unlocking choline's potential in Alzheimer's disease: A narrative review exploring the neuroprotective and neurotrophic role of phosphatidylcholine and assessing its impact on memory and learning

Background and aimsGrowing evidence suggests nutritional intervention may influence the development and progression of Alzheimer‘s Disease (AD). Choline, an essential dietary nutrient plays a critical role in neurological development and brain function, however, its effects on AD in humans is unclear. The research aims to investigate mechanistic links between dietary choline intake and cognitive functioning, focusing on the role of phosphatidylcholine (PC) in neuroplasticity and its interaction with amyloid beta (Aβ) peptides in neuron membranes. Additionally, human evidence on potential benefits of PC interventions on AD, cognition and proposed mechanisms are evaluated. MethodsA reproducible systematic literature search was performed using a three-tranche strategy, consisting of a review, mechanism and intervention search. Using PubMed as the main database, 1254 titles and abstracts were screened, 149 papers were read in full and 65 peer-reviewed papers were accepted, critically appraised and analysed in a narrative review. ResultsPredominantly preclinical evidence demonstrated that PC enhances neuroplasticity, a key biological substrate for cognition, by activating intracellular neuronal signalling pathways or through neuron membrane function.Molecular dynamic simulation methods provided mechanistic understanding of the interconnection between neuronal PC content and the potential behaviour and trajectory of Aβ peptide aggregation. The results indicate that the neuronal membrane composition of PC is critical to inhibiting Aβ aggregation and neuronal damage, protecting the neuron from Aβ toxicity. This might provide a foundation for optimising cellular PC which may prove beneficial in the treatment or prevention of neurodegenerative disease.Altered PC metabolism in AD was evidenced in observational studies; however, whether this relationship represents a cause or consequence of AD remains to be determined. Human intervention studies did not produce conclusive evidence supporting its effectiveness in enhancing cognitive function. This lack of consistency primarily stems from methodological constraints within the conducted studies. Human observational research provided the most compelling evidence linking a higher dietary PC intake to reduced risk of dementia and significant improvements in cognitive testing. ConclusionDespite the lack of randomised control trials (RCTs) assessing the efficacy of lecithin/PC to improve cognition in AD patients, there exists promising evidence supporting its neuroprotective and neurotrophic role.This review establishes an evidence-based framework through chains of mechanistic evidence, that may provide potential strategies for enhanced neuroprotection and reduced neurodegeneration caused by AD. Considering the escalating global burden of AD and the current shortcomings in effective treatments, this review together with the limitations and gaps identified in the existing research present valuable insights that emphasise the urgency of more comprehensive research into the relationship between PC and AD.

Inhibition of Aβ16-22 Aggregation by [TEA]+[Ms]- Follows Weakening of the Hydrophobic Core and Sequestration of Peptides in Ionic Liquid Nanodomains.

We developed a coarse-grained model for the protic ionic liquid, triethylammonium mesylate ([TEA]+[Ms]-), to characterize its inhibitory effects on amyloid aggregation using the K16LVFFAE22 fragment of the amyloid-β (Aβ16-22) as a model amyloidogenic peptide. In agreement with previous experiments, coarse-grained molecular dynamics simulations showed that increasing concentrations of [TEA]+[Ms]- in aqueous media led to increasingly small Aβ16-22 aggregates with low beta-sheet contents. The cause of [TEA]+[Ms]-'s inhibition of peptide aggregation was found to be a result of two interrelated effects. At a local scale, the enrichment of interactions between [TEA]+ cations and hydrophobic phenylalanine side chains weakened the hydrophobic cores of amyloid aggregates, resulting in poorly ordered structures. At a global level, peptides tended to localize at the interfaces of IL-rich nanostructures with water. At high IL concentrations, when the IL-water interface was large or fragmented, Aβ16-22 peptides were dispersed in the simulation cell, sometimes sequestered at unaggregated monomeric states. Together, these phenomena underlie [TEA]+[Ms]-'s inhibition of amyloid aggregation. This work addresses the critical lack of knowledge on the mechanisms of protein-ionic liquid interactions and may have broader implications for industrial applications.

Structure-Activity Relationship of Fluorinated Benzenesulfonamides as Inhibitors of Amyloid-β Aggregation.

Amyloid-beta aggregation is considered one of the factors influencing the onset of the Alzheimer's disease. Early prevention of such aggregation should alleviate disease condition by applying small molecule compounds that shift the aggregation equilibrium toward the soluble form of the peptide or slow down the process. We have discovered that fluorinated benzenesulfonamides of particular structure slowed the amyloid-beta peptide aggregation process by more than three-fold. We synthesized a series of ortho-para and meta-para double-substituted fluorinated benzenesulfonamides that inhibited the aggregation process to a variable extent yielding a detailed picture of the structure-activity relationship. Analysis of compound chemical structure effect on aggregation in artificial cerebrospinal fluid showed the necessity to arrange the benzenesulfonamide, hydrophobic substituent, and benzoic acid in a particular way. The amyloid beta peptide aggregate fibril structures varied in cross-sectional height depending on the applied inhibitor indicating the formation of a complex with the compound. Application of selected inhibitors increased the survivability of cells affected by the amyloid beta peptide. Such compounds may be developed as drugs against Alzheimer's disease.

The Impact of the Angiotensin-Converting Enzyme Inhibitor Lisinopril on Metabolic Rate in Drosophila melanogaster.

Evidence suggests that angiotensin-converting enzyme inhibitors (ACEIs) may increase metabolic rate by promoting thermogenesis, potentially through enhanced fat oxidation and improved insulin. More research is, however, needed to understand this intricate process. In this study, we used 22 lines from the Drosophila Genetic Reference Panel to assess the metabolic rate of virgin female and male flies that were either fed a standard medium or received lisinopril for one week or five weeks. We demonstrated that lisinopril affects the whole-body metabolic rate in Drosophila melanogaster in a genotype-dependent manner. However, the effects of genotypes are highly context-dependent, being influenced by sex and age. Our findings also suggest that lisinopril may increase the Drosophila metabolic rate via the accumulation of a bradykinin-like peptide, which, in turn, enhances cold tolerance by upregulating Ucp4b and Ucp4c genes. Finally, we showed that knocking down Ance, the ortholog of mammalian ACE in Malpighian/renal tubules and the nervous system, leads to opposite changes in metabolic rate, and that the effect of lisinopril depends on Ance in these systems, but in a sex- and age-specific manner. In conclusion, our results regarding D. melanogaster support existing evidence of a connection between ACEI drugs and metabolic rate while offering new insights into this relationship.

Determinants of maturation of the Staphylococcus aureus autoinducing peptide.

The accessory gene regulatory (Agr) system is required for virulence factor gene expression and pathogenesis of Staphylococcus aureus. The Agr system is activated in response to the accumulation of a cyclic autoinducing peptide (AIP), which is matured and secreted by the bacterium. The precursor of AIP, AgrD, consists of the AIP flanked by an N-terminal [Formula: see text]-helical Leader and a charged C-terminal tail. AgrD is matured to AIP by the action of two proteases, AgrB and MroQ. AgrB cleaves the C-terminal tail and promotes the formation of a thiolactone ring, whereas MroQ cleaves the N-terminal Leader in a manner that depends on the four-amino acid linker immediately following a conserved IG helix breaker motif. However, the attributes of AgrD that dictate the sequence of events in peptide maturation are not fully defined. Here, we used engineered AgrD peptide intermediates to ascertain the sufficiency of MroQ for N-terminal peptide cleavage, peptide export, and generation of mature AIP. We found that MroQ promotes the removal of the N-terminal Leader peptide from both linear and cyclic peptide intermediates, while peptide cyclization remained essential for signaling. The expression of the Leader peptide in isolation was sufficient for MroQ-dependent cleavage proximal to the four-amino-acid linker. In addition, active site mutations within AgrB destabilized full-length AgrD and thiolactone-containing intermediates and prevented the release of the Leader peptide. Altogether, our data support a tandem peptide maturation event involving both MroQ and AgrB that appears to couple protease activity and export of bioactive AIP.IMPORTANCEThe accessory gene regulatory (Agr) system is important for S. aureus pathogenesis. Activation of the Agr system requires recognition of a cyclic peptide pheromone, which must be fully matured to exert its biological activity. The complete events in cyclic peptide maturation and export from the bacterial cell remain to be fully defined. We and others recently discovered that the membrane peptidase MroQ is required for pheromone maturation. This study builds off the identification of MroQ and considers the attributes of the pheromone pro-peptide that are required for MroQ-mediated processing as well as uncovers features important for peptide stability and export. Overall, the findings in this study have implications for understanding bacterial pheromone maturation and virulence.