Proteolysis Of Amyloid Precursor Protein Research Articles

Active Site Environment and Reactivity of Copper-Aβ in Membrane Mimetic SDS Micellar Environment.

Alzheimer's disease (AD) is characterized by the abnormal aggregation of amyloid β (Aβ) peptide in extracellular deposits generated upon proteolysis of Amyloid Precursor Protein (APP). While copper (Cu(II)) binds to Aβ in soluble oligomeric and aggregated forms, its interaction with membrane-bound Aβ remains elusive. Investigating these interactions is crucial for understanding AD pathogenesis. Here, utilizing SDS micelles as a simplified membrane mimic, we focus on elucidating the interplay between membrane-anchored Aβ and copper, given their pivotal roles in AD. We employed spectroscopic techniques including UV, CD, and EPR to characterize the active site of Cu-Aβ complexes. Our findings demonstrate that copper interacts with Aβ peptides in membrane-mimicking micellar environments similarly to aqueous buffer solutions. Cu-Aβ complexes in this medium also induce higher hydrogen peroxide (H2O2) production, potentially contributing to AD-related oxidative stress. Moreover, we observe an increased oxidation rate of neurotransmitter such as dopamine by Cu-Aβ complexes. These results enhance our understanding of Cu-Aβ interactions in AD pathology and offer insights into potential therapeutic interventions targeting this interaction.

Emerging structures and dynamic mechanisms of γ-secretase for Alzheimer's disease.

γ-Secretase, called "the proteasome of the membrane," is a membrane-embedded protease complex that cleaves 150+ peptide substrates with central roles in biology and medicine, including amyloid precursor protein and the Notch family of cell-surface receptors. Mutations in γ-secretase and amyloid precursor protein lead to early-onset familial Alzheimer's disease. γ-Secretase has thus served as a critical drug target for treating familial Alzheimer's disease and the more common late-onset Alzheimer's disease as well. However, critical gaps remain in understanding the mechanisms of processive proteolysis of substrates, the effects of familial Alzheimer's disease mutations, and allosteric modulation of substrate cleavage by γ-secretase. In this review, we focus on recent studies of structural dynamic mechanisms of γ-secretase. Different mechanisms, including the "Fit-Stay-Trim," "Sliding-Unwinding," and "Tilting-Unwinding," have been proposed for substrate proteolysis of amyloid precursor protein by γ-secretase based on all-atom molecular dynamics simulations. While an incorrect registry of the Notch1 substrate was identified in the cryo-electron microscopy structure of Notch1-bound γ-secretase, molecular dynamics simulations on a resolved model of Notch1-bound γ-secretase that was reconstructed using the amyloid precursor protein-bound γ-secretase as a template successfully captured γ-secretase activation for proper cleavages of both wildtype and mutant Notch, being consistent with biochemical experimental findings. The approach could be potentially applied to decipher the processing mechanisms of various substrates by γ-secretase. In addition, controversy over the effects of familial Alzheimer's disease mutations, particularly the issue of whether they stabilize or destabilize γ-secretase-substrate complexes, is discussed. Finally, an outlook is provided for future studies of γ-secretase, including pathways of substrate binding and product release, effects of modulators on familial Alzheimer's disease mutations of the γ-secretase-substrate complexes. Comprehensive understanding of the functional mechanisms of γ-secretase will greatly facilitate the rational design of effective drug molecules for treating familial Alzheimer's disease and perhaps Alzheimer's disease in general.

A Metalloproteinase Cocktail from the Venom of Protobothrops flavoviridis Cleaves Amyloid Beta Peptides at the α-Cleavage Site.

A disintegrin and metalloproteinase (ADAM) family proteins are a major class of membrane-anchored multidomain proteinases that are responsible for the shedding of cell surface protein ectodomains, including amyloid precursor protein (APP). Human ADAM 9, 10, and 17 proteolyze APPs and produce non-amyloid-genic p3 peptides, instead of neurotoxic amyloid-β peptides (Aβs; Aβ40 and Aβ42), which form fibrils and accumulate in the brain of patients with Alzheimer's disease (AD). The ADAM family is closely related to snake venom metalloproteinases (SVMPs), which are derived from ancestral ADAMs but act as soluble proteinases. To test the therapeutic potential of SVMPs, we purified SVMPs from Protobothrops flavoviridis venom using metal ion affinity and pooled into a cocktail. Thus, 9 out of 11 SVMPs in the P. flavoviridis genome were identified in the cocktail. SVMPs inhibited Aβ secretion when added to human cell culture medium without affecting APP proteolysis. SVMPs degraded synthetic Aβ40 and Aβ42 peptides at the same cleavage site (α-site of APP) as ADAM9, 10, and 17. SVMPs did not degrade Aβ fibrils but interfered with their formation, assessed using thioflavin-T. Thus, SVMPs have therapeutic potential for AD as an Aβ-degrading protease, and the finding adds to the discovery of bioactive peptides from venoms as novel therapeutics.

Identification of Novel Peptides as Potential Modulators of Aβ42 Amyloidogenesis: An in silico Approach.

Alzheimer's disease is a neurodegenerative disease for which no cure is available. The presence of amyloid plaques in the extracellular space of neural cells is the key feature of this fatal disease. The proteolysis of Amyloid Precursor Protein by presenilin leads to the formation of Amyloid-beta peptides (Aβ 42/40). Deposition of 42 residual Aβ peptides forms fibril's structure, disrupting neuron synaptic transmission, inducing neural cell toxicity, and ultimately leading to neuron death. Various novel peptides have been investigated via molecular docking and molecular dynamic simulation studies to investigate their effects on Aβ amyloidogenesis. The sequence-based peptides were rationally designed and investigated for their interaction with Aβ42 monomer and fibril, and their influence on the structural stability of target proteins was studied. Analyzed docking results suggest that the peptide YRIGY (P6) has the highest binding affinity with Aβ42 fibril amongst all the synthetic peptides, and the peptide DKAPFF (P12) similarly shows a better binding with the Aβ42 monomer. Moreover, simulation results also suggest that the higher the binding affinity, the better the inhibitory action. These findings indicate that both the rationally designed peptides can modulate amyloidogenesis, but peptide (P6) has better potential for the disaggregation of the fibrils. In contrast, peptide P12 stabilizes the native structure of the Aβ42 monomer more effectively and hence can serve as a potential amyloid inhibitor. Thus, these peptides can be explored as therapeutic agents against Alzheimer's disease. Experimental testing of these peptides for immunogenicity, stability in cellular conditions, toxic effects and membrane permeability can be the future research scope of this study.

A tailored tetravalent peptide displays dual functions to inhibit amyloid β production and aggregation

Inhibition of amyloid-β peptide (Aβ) accumulation in the brain is a promising approach for treatment of Alzheimer’s disease (AD). Aβ is produced by β-secretase and γ-secretase in endosomes via sequential proteolysis of amyloid precursor protein (APP). Aβ and APP have a common feature to readily cluster to form multimers. Here, using multivalent peptide library screens, we identified a tetravalent peptide, LME-tet, which binds APP and Aβ via multivalent interactions. In cells, LME-tet-bound APP in the plasma membrane is transported to endosomes, blocking Aβ production through specific inhibition of β-cleavage, but not γ-cleavage. LME-tet further suppresses Aβ aggregation by blocking formation of the β-sheet conformation. Inhibitory effects are not observed with a monomeric peptide, emphasizing the significance of multivalent interactions for mediating these activities. Critically, LME-tet efficiently reduces Aβ levels in the brain of AD model mice, suggesting it may hold promise for treatment of AD.

Analysis of Non-Amyloidogenic Mutations in APP Supports Loss of Function Hypothesis of Alzheimer's Disease.

Proteolytic processing of amyloid precursor protein (APP) plays a critical role in pathogenesis of Azheimer's disease (AD). Sequential cleavage of APP by β- and γ-secretases leads to generation of Aβ40 (non-amyloidogenic) and Aβ42 (amyloidogenic) peptides. Presenilin-1 (PS1) or presenilin-2 (PS2) act as catalytic subunits of γ-secretase. Multiple familial AD (FAD) mutations in APP, PS1, or PS2 affect APP proteolysis by γ-secretase and influence levels of generated Aβ40 and Aβ42 peptides. The predominant idea in the field is the "amyloid hypothesis" that states that the resulting increase in Aβ42:Aβ40 ratio leads to "toxic gain of function" due to the accumulation of toxic Aβ42 plaques and oligomers. An alternative hypothesis based on analysis of PS1 conditional knockout mice is that "loss of function" of γ-secretase plays an important role in AD pathogenesis. In the present paper, we propose a mechanistic hypothesis that may potentially reconcile these divergent ideas and observations. We propose that the presence of soluble Aβ peptides in endosomal lumen (and secreted to the extracellular space) is essential for synaptic and neuronal function. Based on structural modeling of Aβ peptides, we concluded that Aβ42 peptides and Aβ40 peptides containing non-amyloidogenic FAD mutations in APP have increased the energy of association with the membranes, resulting in reduced levels of soluble Aβ in endosomal compartments. Analysis of PS1-FAD mutations also revealed that all of these mutations lead to significant reduction in both total levels of Aβ produced and in the Aβ40/Aβ42 ratio, suggesting that the concentration of soluble Aβ in the endosomal compartments is reduced as a result of these mutations. We further reasoned that similar changes in Aβ production may also occur as a result of age-related accumulation of cholesterol and lipid oxidation products in postsynaptic spines. Our analysis more easily reconciled with the "loss of γ-secretase function" hypothesis than with the "toxic gain of Aβ42 function" idea. These results may also explain why inhibitors of β- and γ- secretase failed in clinical trials, as these compounds are also expected to significantly reduce soluble Aβ levels in the endosomal compartments.

Secretases in Alzheimer's disease: Novel insights into proteolysis of APP and TREM2.

Secretases are a group of proteases that are major drug targets considered for the prevention and treatment of Alzheimer's disease (AD). Secretases do not only process the AD-linked neuronal amyloid precursor protein (APP)but also the triggering receptor expressed on myeloid cells 2 (TREM2), thereby controlling microglial functions. This review highlights selectedrecent discoveries for the α-secretases a disintegrin and metalloprotease 10 (ADAM10) and a disintegrin and metalloprotease 17 (ADAM17), the β-secretase β-site APP cleaving enzyme 1 (BACE1) and γ-secretase and their link to AD. New genetic evidence strengthens the role of α-secretases in AD through cleavage of APP and TREM2. Novel proteins were linked to AD, which control α- and β-secretase activity through transcriptional and post-translational mechanisms. Finally, new opportunitiesbut also challenges are discussed for pharmacologically targeting β- and γ-secretase cleavage of APP and α-secretase cleavage of TREM2with the aim to prevent or treat AD.

Insulin gene expression and functional activity of insulin signaling pathway in Alzheimer's disease

Aim. To study the insulin (INS) gene expression, insulin and lactate levels, expression of Fe65 adapter protein, and level of oxidative DNA damage marker γH2AX in different brain areas in the experimental model of Alzheimer's disease.Materials and Methods. Male, 4-month-old C57BL/6 mice received either intrahippocampal injection of β-amyloid (C57BL/6 + Aβ 1-42) or phosphate-buffered saline (C57BL/6 + PBS). Insulin (INS) gene expression in the hippocampus and amygdala was assessed by means of reverse transcription-polymerase chain reaction. Levels of lactate and insulin in different brain areas were measured by enzyme-linked immunosorbent assay. Expression of Fe65 adapter protein and γH2AX in the hippocampus was studied by immunofluorescence staining followed by confocal microscopy.Results. We found an overexpression of the INS gene in the hippocampus and amygdala, an increase in lactate level in the hippocampus, and slightly increased insulin level in the amygdala of mice with Alzheimer's disease as compared with the control group. Neurodegeneration was accompanied by an elevated endothelial expression of Fe65 adapter protein (p= 0.04) and γH2AX in hippocampal neurons (p = 0.04).Conclusion. Alzheimer's disease neurodegeneration is accompanied by a disrupted insulin signaling and impaired glucose metabolism in the hippocampus and amygdala. This further leads to a neuronal accumulation of γH2AX and impaired amyloid precursor protein proteolysis because of insulin inability to inhibit its interaction with the Fe65 adapter protein and to prevent formation and deposition of β-amyloid.

Cardiometabolic Modification of Amyloid Beta in Alzheimer's Disease Pathology.

In recent years, several studies have suggested that cardiometabolic disorders, such as diabetes, obesity, hypertension, and dyslipidemia, share strong connections with the onset of neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease (AD). However, establishing a definitive link between medical disorders with coincident pathophysiologies is difficult due to etiological heterogeneity and underlying comorbidities. For this reason, amyloid β (Aβ), a physiological peptide derived from the sequential proteolysis of amyloid precursor protein (APP), serves as a crucial link that bridges the gap between cardiometabolic and neurodegenerative disorders. Aβ normally regulates neuronal synaptic function and repair; however, the intracellular accumulation of Aβ within the brain has been observed to play a critical role in AD pathology. A portion of Aβ is believed to originate from the brain itself and can readily cross the blood-brain barrier, while the rest resides in peripheral tissues that express APP required for Aβ generation such as the liver, pancreas, kidney, spleen, skin, and lungs. Consequently, numerous organs contribute to the body pool of total circulating Aβ, which can accumulate in the brain and facilitate neurodegeneration. Although the accumulation of Aβ corresponds with the onset of neurodegenerative disorders, the direct function of periphery born Aβ in AD pathophysiology is currently unknown. This review will highlight the contributions of individual cardiometabolic diseases including cardiovascular disease (CVD), type 2 diabetes (T2D), obesity, and non-alcoholic fatty liver disease (NAFLD) in elevating concentrations of circulating Aβ within the brain, as well as discuss the comorbid association of Aβ with AD pathology.

A nontoxigenic form of Shiga toxin 2 suppresses the production of amyloid β by altering the intracellular transport of amyloid precursor protein through its receptor-binding B-subunit

Accumulation of amyloid-β peptide (Aβ) in neuronal cells and in the extracellular regions in the brain is a major cause of Alzheimer’s disease (AD); therefore, inhibition of Aβ accumulation offers a promising approach for therapeutic strategies against AD. Aβ is produced by sequential proteolysis of amyloid precursor protein (APP) in late/recycling endosomes after endocytosis of APP located in the plasma membrane. Aβ is then released from cells in a free form or in an exosome-bound form. Shiga toxin (Stx) is a major virulence factor of enterohemorrhagic Escherichia coli. Recently, we found that one of the Stx subtypes, Stx2a, has a unique intracellular transport route after endocytosis through its receptor-binding B-subunit. A part of Stx2a can be transported to late/recycling endosomes and then degraded in a lysosomal acidic compartment, although in general Stx is transported to the Golgi and then to the endoplasmic reticulum in a retrograde manner. In this study, we found that treatment of APP-expressing cells with a mutant Stx2a (mStx2a), lacking cytotoxic activity because of mutations in the catalytic A-subunit, stimulated the transport of APP to the acidic compartment, which led to degradation of APP and a reduction in the amount of Aβ. mStx2a-treatment also inhibited the extracellular release of Aβ. Therefore, mStx2a may provide a new strategy to inhibit the production of Aβ by modulating the intracellular transport of APP.

Hydrophilic loop 1 of Presenilin-1 and the APP GxxxG transmembrane motif regulate γ-secretase function in generating Alzheimer-causing Aβ peptides

γ-Secretase is responsible for the proteolysis of amyloid precursor protein (APP) into amyloid-beta (Aβ) peptides, which are centrally implicated in the pathogenesis of Alzheimer’s disease (AD). The biochemical mechanism of how processing by γ-secretase is regulated, especially as regards the interaction between enzyme and substrate, remains largely unknown. Here, mutagenesis reveals that the hydrophilic loop-1 (HL-1) of presenilin-1 (PS1) is critical for both γ-secretase step-wise cleavages (processivity) and its allosteric modulation by heterocyclic γ-modulatory compounds. Systematic mutagenesis of HL-1, including all of its familial AD mutations and additional engineered variants, and quantification of the resultant Aβ products show that HL-1 is necessary for proper sequential γ-secretase processivity. We identify Y106, L113, and Y115 in HL-1 as key targets for heterocyclic γ-secretase modulators (GSMs) to stimulate processing of pathogenic Aβ peptides. Further, we confirm that the GxxxG domain in the APP transmembrane region functions as a critical substrate motif for γ-secretase processivity: a G29A substitution in APP-C99 mimics the beneficial effects of GSMs. Together, these findings provide a molecular basis for the structural regulation of γ-processivity by enzyme and substrate, facilitating the rational design of new GSMs that lower AD-initiating amyloidogenic Aβ peptides.

Alteration in synaptic nanoscale organization dictates amyloidogenic processing in Alzheimer's disease.

SummaryDespite intuitive insights into differential proteolysis of amyloid precursor protein (APP), the stochasticity behind local product formation through amyloidogenic pathway at individual synapses remain unclear. Here, we show that the major components of amyloidogenic machinery namely, APP and secretases are discretely organized into nanodomains of high local concentration compared to their immediate environment in functional zones of the synapse. Additionally, with the aid of multiple models of Alzheimer's disease (AD), we confirm that this discrete nanoscale chemical map of amyloidogenic machinery is altered at excitatory synapses. Furthermore, we provide realistic models of amyloidogenic processing in unitary vesicles originating from the endocytic zone of excitatory synapses. Thus, we show how an alteration in the stochasticity of synaptic nanoscale organization contributes to the dynamic range of C-terminal fragments β (CTFβ) production, defining the heterogeneity of amyloidogenic processing at individual synapses, leading to long-term synaptic deficits as seen in AD.

Matrix Metalloproteinase 14 Mediates APP Proteolysis and Lysosomal Alterations Induced by Oxidative Stress in Human Neuronal Cells.

The alteration of amyloid precursor protein (APP) proteolysis is a hallmark of Alzheimer's disease (AD). Recent studies have described noncanonical pathways of APP processing that seem partly executed by lysosomal enzymes. Our laboratory's in vitro human SK-N-MC model has shown that oxidative stress (OS) alters the lysosomal degradation pathway and the processing/metabolism of APP. The present study identifies the lysosomal protein matrix metalloproteinase 14 (MMP14) as a protease involved in the APP noncanonical processing. Previous expression analyses of the above cells showed MMP14 to be overexpressed under OS. In the present work, its role in changes in OS-induced APP proteolysis and lysosomal load was examined. The results show that MMP14 mediates the accumulation of an ≈85 kDa N-terminal APP fragment and increases the lysosome load induced by OS. These results were validated in neurons and neural progenitor cells generated from the induced pluripotent stem cells of patients with sporadic AD, reinforcing the idea that MMP14 may offer a therapeutic target in this disease.

A peptide fraction of Olive Flounder (Paralichthys olivaceus) Skin Hydrolysate Inhibits Amyloid-β Generation in SH-SY5Y Cells via Suppression of BACE1 Expression

The prevalence of degenerative neuro-diseases such as Alzheimer’s disease has increased with an increase in the life expectancy especially as seen in developed countries. According to the Amyloid Hypothesis, β-secretase leads to the onset of Alzheimer's disease though the generation of amyloid-β by proteolysis of amyloid precursor protein. Amyloid-β aggregates to form oligomers that build up to form plaques. Olive flounder (Paralichthys olivaceus) is high in protein content, with a higher protein content in skin (27.65%) compared to muscle (19.65%) according to proximate analysis results. Enzyme hydrolysates were prepared from skin and muscle using several enzymes. The neutrase skin hydrolysate showed the highest β-secretase inhibitory activity IC50 0.61 mg/mL. Purification steps were performed using ion exchange chromatography on QMA and CM-cellulose columns and SPE C18 column to produce an active fraction QMA-F1 with an IC50 value of 32.80 µg/mL. QMA-F1 was non-cytotoxic to SH-SY5Y cells, reduced BACE1 overexpression and attenuated amyloidogenesis. This suggests that the active β-secretase inhibitory peptides from olive flounder skin hydrolysates can be utilized as an ingredient in development of new pharmaceutical and nutraceutical therapeutic agents for Alzheimer’s Disease.

Phosphatidylinositol-4-phosphate 5-kinase type 1α attenuates Aβ production by promoting non-amyloidogenic processing of amyloid precursor protein.

Alzheimer's disease (AD) is characterized by a chronic decline in cognitive function and is pathologically typified by cerebral deposition of amyloid-β peptide (Aβ). The production of Aβ is mediated by sequential proteolysis of amyloid precursor protein (APP) by β- and γ-secretases, and has been implicated as the essential determinant of AD pathology. Previous studies have demonstrated that the level of phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] in the membrane may potentially modulate Aβ production. Given that PI(4,5)P2 is produced by type 1 phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks), we sought to determine whether the level of PIP5K type Iα (PIP5K1A) can affect production of Aβ by modulating the lipid composition of the membrane. Using a HEK-derived cell line that constitutively expresses yellow fluorescent protein-tagged APP (APP-YFP), we demonstrated that overexpression of PIP5K1A results in significant enhancement of non-amyloidogenic APP processing and a concomitant suppression of the amyloidogenic pathway, leading to a marked decrease in secreted Aβ. Consistently, cells overexpressing PIP5K1A exhibited a significant redistribution of APP-YFP from endosomal compartments to the cell surface. Our findings suggest that PIP5K1A may play a critical role in governing Aβ production by modulating membrane distribution of APP, and as such, the pathway may be a valuable therapeutic target for AD.

Exploring the Role of PSEN Mutations in the Pathogenesis of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common cause of dementia. Mutations of presenilin (PSEN) genes that encode presenilin proteins have been found as the vital causal factors for early-onset familial AD (FAD). AD pathological features such as memory loss, synaptic dysfunction, and formation of plaques have been successfully mimicked in the transgenic mouse models that coexpress FAD-related presenilin and amyloid precursor protein (APP) variants. γ-Secretase (GS) is an enzyme that plays roles in catalyzing intramembranous APP proteolysis to release pathogenic amyloid beta (Aβ). It has been found that presenilins can play a role as the GS's catalytic subunit. FAD-related mutations in presenilins can modify the site of GS cleavage in a way that can elevate the production of longer and highly fibrillogenic Aβ. Presenilins can interact with β-catenin to generate presenilin complexes. Aforesaid interactions have also been studied to observe the mutational and physiological activities in the catenin signal transduction pathway. Along with APP, GS can catalyze intramembrane proteolysis of various substrates that play a vital role in synaptic function. PSEN mutations can cause FAD with autosomal dominant inheritance and early onset of the disease. In this article, we have reviewed the current progress in the analysis of PSENs and the correlation of PSEN mutations and AD pathogenesis.

Mechanisms of γ-Secretase Activation and Substrate Processing.

Amyloid β-peptide, the principal component of characteristic cerebral plaques of Alzheimer’s disease (AD), is produced through intramembrane proteolysis of the amyloid precursor protein (APP) by γ-secretase. Despite the importance in the pathogenesis of AD, the mechanisms of intramembrane proteolysis and substrate processing by γ-secretase remain poorly understood. Here, complementary all-atom simulations using a robust Gaussian accelerated molecular dynamics (GaMD) method and biochemical experiments were combined to investigate substrate processing of wildtype and mutant APP by γ-secretase. The GaMD simulations captured spontaneous activation of γ-secretase, with hydrogen bonded catalytic aspartates and water poised for proteolysis of APP at the ε cleavage site. Furthermore, GaMD simulations revealed that familial AD mutations I45F and T48P enhanced the initial ε cleavage between residues Leu49–Val50, while M51F mutation shifted the ε cleavage site to the amide bond between Thr48–Leu49. Detailed analysis of the GaMD simulations allowed us to identify distinct low-energy conformational states of γ-secretase, different secondary structures of the wildtype and mutant APP substrate, and important active-site subpockets for catalytic function of the enzyme. The simulation findings were highly consistent with experimental analyses of APP proteolytic products using mass spectrometry and Western blotting. Taken together, the GaMD simulations and biochemical experiments have enabled us to elucidate the mechanisms of γ-secretase activation and substrate processing, which should facilitate rational computer-aided drug design targeting this functionally important enzyme.

Amyloid β induces interneuron-specific changes in the hippocampus of APPNL-F mice.

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by cognitive decline and amyloid-beta (Aβ) depositions generated by the proteolysis of amyloid precursor protein (APP) in the brain. In APPNL-F mice, APP gene was humanized and contains two familial AD mutations, and APP–unlike other mouse models of AD–is driven by the endogenous mouse APP promoter. Similar to people without apparent cognitive dysfunction but with heavy Aβ plaque load, we found no significant decline in the working memory of adult APPNL-F mice, but these mice showed decline in the expression of normal anxiety. Using immunohistochemistry and 3D block-face scanning electron microscopy, we found no changes in GABAA receptor positivity and size of somatic and dendritic synapses of hippocampal interneurons. We did not find alterations in the level of expression of perineuronal nets around parvalbumin (PV) interneurons or in the density of PV- or somatostatin-positive hippocampal interneurons. However, in contrast to other investigated cell types, PV interneuron axons were occasionally mildly dystrophic around Aβ plaques, and the synapses of PV-positive axon initial segment (AIS)-targeting interneurons were significantly enlarged. Our results suggest that PV interneurons are highly resistant to amyloidosis in APPNL-F mice and amyloid-induced increase in hippocampal pyramidal cell excitability may be compensated by PV-positive AIS-targeting cells. Mechanisms that make PV neurons more resilient could therefore be exploited in the treatment of AD for mitigating Aβ-related inflammatory effects on neurons.

Screening of potential inhibitors against flotillin-1 as therapeutics for Alzheimer's disease

Background: Alzheimer's disease (AD) is one of the most common neurological disorders occurring in older people. So far, no specific drug is available for the disease, and only palliative medicines are available for the patients. Accumulation of amyloid beta (Aβ) peptides is considered to play a crucial role in the generation of the disease. Aβ peptide is generated by the proteolysis of amyloid precursor protein by two distinct proteases β and γ-secretase. Flotillin-1 (FLOT1) directly binds to the cytoplasmic tail of β-secretase and affects the sorting and recycling of the enzyme. Increased expression of FLOT1 has been correlated with the progression of AD, while FLOT1 knockdown causes a reduction in Aβ production. Thus, FLOT1 is an attractive therapeutic target for the suppression of beta-secretase 1 (BACE-1 ). Objective: This study aims to screen the potential inhibitors against FLOT1 as therapeutics for AD. Materials and Methodology: In this work, protein–protein interactions, tertiary structure prediction, molecular docking, and molecular dynamics (MD) simulation were performed. Results: Tertiary structure prediction of FLOT1 and screening inhibitors against it helped in finding key molecules with potential therapeutic properties. Protein–protein interaction study of FLOT1 deciphered the interactors playing key role in AD. Pharmacokinetic parameters were quantified for each potential inhibitor. The results of MD simulation analysis revealed that the ZINC67911837 had better inhibitory activities with FLOT1. Conclusion: The analysis suggests that the ZINC67911837 compound could be a novel potential inhibitor of FLOT1 to modulate BACE-1 activity and used as a therapeutic agent for the treatment of AD. This study facilitates the initiation of the natural drug discovery process for the treatment of AD patients.

IL-1R-/- alleviates cognitive deficits through microglial M2 polarization in AD mice

The neuroinflammatory response is considered a crucial event in the pathology of Alzheimer’s disease (AD). Neurotoxic amyloid β (Aβ) oligomers activate neuronal glial cells, leading to the elevated generation of a large variety of inflammatory factors. Therefore, the regulation of interleukin-1 receptor (IL-1R) activity is believed to be a potential target for AD therapy. However, previous evidence of the role of IL-1R in AD-related neuroinflammation is ambiguous. To reveal the exact role of IL-1R in AD and related inflammatory reactions, we generated IL-1R−/− AD mice. Based on the Morris water maze results, 4-month-old IL-1R−/− AD mice showed better learning and memory ability than that of AD mice. However, IL-1R−/− had little influence on amyloid precursor protein proteolysis, while IL-1R−/− increased ADAM17 expression level. Surprisingly, IL-1R−/− even enhanced glial activation. IL-1R−/− indeed attenuated inflammatory cytokine secretion, especially that of cytokins associated with M1 polarization, while it led to increased levels of some cytokins associated with M2 polarization. Finally, we found that IL-1R−/− reduced the phagocytic ability of microglia. Taken together, these results suggest that IL-1R deficiency may alleviate cognitive deficits in AD mice in a manner that is partially dependent on ADAM17 regulation and microglia M2 repolarization.