O-GlcNAc protein modification in plants: Evolution and function

The role in plants of posttranslational modification of proteins with O-linked N-acetylglucosamine and the evolution and function of O-GlcNAc transferases responsible for this modification are reviewed. Phylogenetic analysis of eukaryotic O-GlcNAc transferases (OGTs) leads us to propose that plants have two distinct OGTs, SEC- and SPY-like, that originated in prokaryotes. Animals and some fungi have a SEC-like enzyme while plants have both. Green algae and some members of the Apicomplexa and amoebozoa have the SPY-like enzyme. Interestingly the progenitor of the Apicomplexa lineage likely had a photosynthetic plastid that persists in a degenerated form in some species, raising the possibility that plant SPY-like OGTs are derived from a photosynthetic endosymbiont. OGTs have multiple tetratricopeptide repeats (TPRs) that within the SEC- and SPY-like classes exhibit evidence of strong selective pressure on specific repeats, suggesting that the function of these repeats is conserved. SPY-like and SEC-like OGTs have both unique and overlapping roles in the plant. The phenotypes of sec and spy single and double mutants indicate that O-GlcNAc modification is essential and that it affects diverse plant processes including response to hormones and environmental signals, circadian rhythms, development, intercellular transport and virus infection. The mechanistic details of how O-GlcNAc modification affects these processes are largely unknown. A major impediment to understanding this is the lack of knowledge of the identities of the modified proteins.     

O-GlcNAc修饰与肿瘤发生及转移

O-连接的β-N-乙酰葡糖胺（O-GlcNAc）修饰是一种广泛存在于细胞浆和细胞核蛋白质丝/苏氨酸上的动态、可逆的翻译后修饰. 这种修饰与经典的糖基化不同而类似于磷酸化修饰,它在生命过程中发挥重要的调节作用. O-GlcNAc修饰作为潜在的营养感受器,可以调节转录、代谢等众多细胞进程,并与癌症等人类重大疾病密切相关. 本文主要综述了O-GlcNAc修饰与肿瘤形成和转移的关系,并对O-GlcNAc促进肿瘤形成与转移的潜在分子机制进行了探讨.     

Novel Adaptors of Amyloid Precursor Protein Intracellular Domain and Their Functional Implications

Amyloid precursor protein intracellular domain(AICD) is one of the potential candidates in deciphering the complexity of Alzheimer’s disease.It plays important roles in determining cell fate and neurodegeneration through its interactions with several adaptors.The presence or absence of phosphorylation at specific sites determines the choice of partners.In this study,we identified 20 novel AICDinteracting proteins by in vitro pull down experiments followed by 2D gel electrophoresis and MALDI-MS analysis.The identified proteins can be grouped into different functional classes including molecular chaperones,structural proteins,signaling and transport molecules,adaptors,motor proteins and apoptosis determinants.Interactions of nine proteins were further validated either by colocalization using confocal imaging or by co-immunoprecipitation followed by immunoblotting.The cellular functions of most of the proteins can be correlated with AD.Hence,illustration of their interactions with AICD may shed some light on the disease pathophysiology.     

Evidence for a Functional O-Linked N-Acetylglucosamine (O-GlcNAc) System in the Thermophilic Bacterium Thermobaculum terrenum

Post-translational modification of proteins is a ubiquitous mechanism of signal transduction in all kingdoms of life. One such modification is addition of O-linked N-acetylglucosamine to serine or threonine residues, known as O-GlcNAcylation. This unusual type of glycosylation is thought to be restricted to nucleocytoplasmic proteins of eukaryotes and is mediated by a pair of O-GlcNAc-transferase and O-GlcNAc hydrolase enzymes operating on a large number of substrate proteins. Protein O-GlcNAcylation is responsive to glucose and flux through the hexosamine biosynthetic pathway. Thus, a close relationship is thought to exist between the level of O-GlcNAc proteins within and the general metabolic state of the cell. Although isolated apparent orthologues of these enzymes are present in bacterial genomes, their biological functions remain largely unexplored. It is possible that understanding the function of these proteins will allow development of reductionist models to uncover the principles of O-GlcNAc signaling. Here, we identify orthologues of both O-GlcNAc cycling enzymes in the genome of the thermophilic eubacterium Thermobaculum terrenum. The O-GlcNAcase and O-GlcNAc-transferase are co-expressed and, like their mammalian orthologues, localize to the cytoplasm. The O-GlcNAcase orthologue possesses activity against O-GlcNAc proteins and model substrates. We describe crystal structures of both enzymes, including an O-GlcNAcase·peptide complex, showing conservation of active sites with the human orthologues. Although in vitro activity of the O-GlcNAc-transferase could not be detected, treatment of T. terrenum with an O-GlcNAc-transferase inhibitor led to inhibition of growth. T. terrenum may be the first example of a bacterium possessing a functional O-GlcNAc system.     

Novel biphenyl bis-sulfonamides as acetyl and butyrylcholinesterase inhibitors: Synthesis,biological evaluation and molecular modeling studies

A series of new biphenyl bis-sulfonamide derivatives 2a–3p were synthesized in good to excellent yield (76–98%). The inhibitory potential of the synthesized compounds on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) was investigated. Most of the screened compounds showed modest in vitro inhibition for both AChE and BChE. Compared to the reference compound eserine (IC₅₀ 0.04 ± 0.0001 μM for AChE) and (IC₅₀ 0.85 ± 0.0001 μM for BChE), the IC₅₀ values of these compounds were ranged from 2.27 ± 0.01 to 123.11 ± 0.04 μM for AChE and 7.74 ± 0.07 to <400 μM for BuChE. Among the tested compounds, 3p was found to be the most potent against AChE (IC₅₀ 2.27 ± 0.01 μM), whereas 3g exhibited the highest inhibition for BChE (IC₅₀ 7.74 ± 0.07 μM). Structure–activity relationship (SAR) of these compounds was developed and elaborated with the help of molecular docking studies.     

Effects of Picrasma quassioides and its active constituents on Alzheimer's disease in vitro and in vivo

Alzheimer disease (AD), a prevalent neurodegenerative disorder, is one of the leading causes of dementia. However, there is no effective drug for this disease to date. Picrasma quassioides (D.Don) Benn, a Chinese traditional medicine, was used mainly for the treatment of inflammation, fever, microbial infection and dysentery. In this paper, we reported that the EtOAc extract of Picrasma quassioides stems showed potential neuroprotective activities in l-glutamate-stimulated PC12 and Aβ_25-35-stimulated SH-SY5Y cell models, as well as improved memory and cognitive abilities in AD mice induced by amyloid-β peptide. Moreover, it was revealed that the anti-AD mechanism was related to suppressing neuroinflammatory and reducing Aβ_1-42 deposition using ELISA assay kits. To clarify the active components of the EtOAc extract of Picrasma quassioides stems, a systematic phytochemistry study led to isolate and identify six β-carboline alkaloids (1–6), seven canthin-6-one alkaloids (7–13), and five quassinoids (14–18). Among them, four β-carbolines (1–3, and 6) and six canthin-6-ones (7–11, and 13) exhibited potential neuroprotective activities in vitro. Based on these date, the structure-activity relationships of alkaloids were discussed. Furthermore, molecular docking experiments showed that compounds 2 and 3 have high affinity for both of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYPKIA) and butyrylcholinesterase (BuChE).     

溶酶体离子通道蛋白在神经退行性疾病发生发展中的作用及机制研究

溶酶体离子通道蛋白异常引起溶酶体功能障碍是导致阿尔茨海默病(Alzheimer’s disease,AD)和帕金森病(Parkinson’s disease,PD)等神经退行性疾病的重要因素.溶酶体离子通道蛋白调节溶酶体内离子稳态、溶酶体膜电压以及溶酶体的酸度.溶酶体离子通道蛋白的结构或功能缺陷会引起溶酶体降解功能障碍,导致神经退行性疾病的发生发展.在这篇综述中,我们总结了各种离子通道蛋白调节溶酶体功能的过程及机制,以及离子通道蛋白异常参与神经退行性疾病的过程和机制.调节离子通道蛋白改善溶酶体的功能、促进异常聚集蛋白的清除,是神经退行性疾病治疗的潜在途径.     

Antagonistic molecular interactions of photosynthetic pigments with molecular disease targets: a new approach to treat AD and ALS

Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS) are progressive neurodegenerative diseases that affect the neurons in the brain and the spinal cord. Neuroinflamation and apoptosis are key players in the progressive damage of the neurons in AD and ALS. Currently, there is no drug to offer complete cure for both these diseases. Riluzole is the only available drug that can prolong the life time of the ALS patients for nearly 3 months. Molecules that offer good HIT to the molecular targets of ALS will help to treat AD and ALS patients. P53 kinase receptor (4AT3), EphA4 (3CKH) and histone deacetylase (3SFF) are the promising disease targets of AD and ALS. This paper discusses on a new approach to combat neurodegenerative diseases using photosynthetic pigments. The docking studies were performed with the Autodock Vina algorithm to predict the binding of the natural pigments such as β carotene, chlorophyll a, chlorophyll b, phycoerythrin and phycocyanin on these targets. The β carotene, phycoerythrin and phycocyanin had higher binding energies indicating the antagonistic activity to the disease targets. These pigments serve as a potential therapeutic molecule to treat neuroinflammation and apoptosis in the AD and ALS patients.     

Comprehensive analysis of the molecular docking of small molecule inhibitors to the Aβ1–40 peptide and its Osaka-mutant: insights into the molecular mechanisms of Aβ-peptide inhibition

Abstract

Alzheimer’s disease (AD) is the most common form of age-related neurodegeneration occurs because of deposition of proteins in the form of extracellular plaques containing aggregated amyloid beta (Aβ) peptide and intracellular neurofibrillary tangles composed of aggregated microtubule-binding protein tau. Amyloid aggregation process can be enhanced by several familial AD-associated mutations in Aβ peptide. In this study, we have unravelled the interactions of 40 small molecule inhibitors with the Osaka-mutant of Aβ_1–40 peptide at atomic level and characterized modes of their binding to mutant Aβ by docking approaches. We have also compared docking energies of these inhibitors with Osaka-mutant with those previously determined for the wild-type and Iowa-mutant peptides and discussed in light of the peptide conformations and non-covalent interactions. We have also discussed inhibition mechanisms of these three peptides. Our analyses revealed that these small molecules can efficiently inhibit Osaka-mutant. The binding modes of drugs with these three peptides are markedly different and so are the mechanisms of inhibition of these three peptides. Overall analysis of the data reveals that binding energy of Iowa-mutant drug complex is lowest and most stable which is followed wild-type peptide-drug complex followed by Osaka-mutant drug complex.

Communicated by Ramaswamy H. Sarma     

Exosomes and microRNAs: New potential therapeutic candidates in Alzheimer disease therapy

Exosomes are biological nanocarriers which could be involved in a variety of basic physiological events. They exert their effects via targeting their cargos (i.e., DNAs, messenger RNAs, microRNAs [miRNAs], and proteins) to host cells, which led to change behaviors of recipient cells. One of the important aspects of exosomes is the roles of them in disease conditions. Increasing evidence indicated that exosomes are one of the main players in Alzheimer’s disease (AD) pathogenesis. Hence, it seems that these nanocarriers could be used as diagnostic and therapeutic biomarkers in AD treatment. Another important player in AD pathogenesis is miRNA. MiRNAs are short noncoding RNAs which exert their effects as epigenetic regulators. These molecules involved in different stages of AD. Therefore, miRNAs could be used as prognostic, diagnostic, and therapeutic biomarkers in AD. Here, we summarized various roles of exosomes and application of them in AD pathogenesis. Moreover, we highlighted the utilization of miRNAs as a therapeutic option in AD therapy.     

Computer-aided molecular design of pyrazolotriazines targeting glycogen synthase kinase 3

Numerous studies have highlighted the implications of the glycogen synthase kinase 3 (GSK-3) in several processes associated with Alzheimer’s disease (AD). Therefore, GSK-3 has become a crucial therapeutic target for the treatment of this neurodegenerative disorder. Hereby, we report the design and multistep synthesis of ethyl 4-oxo-pyrazolo[4,3-d][1–3]triazine-7-carboxylates and their biological evaluation as GSK-3 inhibitors. Molecular modelling studies allow us to develop this new scaffold optimising the chemical structure. Potential binding mode determination in the enzyme and the analysis of the key features in the catalytic site are also described. Furthermore, the ability of pyrazolotriazinones to cross the blood–brain barrier (BBB) was evaluated by passive diffusion and those who showed great GSK-3 inhibition and permeation to the central nervous system (CNS) showed neuroprotective properties against tau hyperphosphorylation in a cell-based model. These new brain permeable pyrazolotriazinones may be used for key in vivo studies and may be considered as new leads for further optimisation for the treatment of AD.     

Identification of novel acetylcholinesterase inhibitors through e-pharmacophore-based virtual screening and molecular dynamics simulations

Alzheimer’s disease (AD), a progressive neurodegenerative disorder is the most common cause of dementia among elderly people. To date, the successful therapeutic strategy to treat AD is maintaining the levels of acetylcholine via inhibiting acetylcholinesterase (AChE). The present study involves identification of newer AChE inhibitors by dual approach of e-pharmacophore and structure-based virtual screening of Asinex library. Robustness of docking protocol was validated by enrichment calculation with ROC value .71 and BEDROC value .028. Among 11 selected hits, ZINC72338524 with best MM-GBSA dG binding shows optimal range of CNS properties and ligand–AChE complex stability. Further, molecular dynamics study revealed its molecular interactions with Trp86, Phe338, and Tyr341 amino acid residues of catalytic anionic site and Tyr124, Ser125, and Trp286 amino acid residues of peripheral anionic site. Physicochemical properties and ADMET risk prediction indicates their potential in druggability and safety.     

Preparation,anticholinesterase activity and molecular docking of new lupane derivatives

A set of twenty one lupane derivatives (2–22) was prepared from the natural triterpenoid calenduladiol (1) by transformations on the hydroxyl groups at C-3 and C-16, and also on the isopropenyl moiety. The derivatives were tested for their inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and some structure–activity relationships were outlined with the aid of enzyme kinetic studies and docking modelization. The most active compound resulted to be 3,16,30-trioxolup-20(29)-ene (22), with an IC₅₀ value of 21.5 μM for butyrylcholinesterase, which revealed a selective inhibitor profile towards this enzyme.     

Synthesis,molecular docking and biological evaluation of N,N-disubstituted 2-aminothiazolines as a new class of butyrylcholinesterase and carboxylesterase inhibitors

A series of 31 N,N-disubstituted 2-amino-5-halomethyl-2-thiazolines was designed, synthesized, and evaluated for inhibitory potential against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CaE). The compounds did not inhibit AChE; the most active compounds inhibited BChE and CaE with IC₅₀ values of 0.22–2.3 μM. Pyridine-containing compounds were more selective toward BChE; compounds with the para-OMe substituent in one of the two dibenzyl fragments were more selective toward CaE. Iodinated derivatives were more effective BChE inhibitors than brominated ones, while there was no influence of halogen type on CaE inhibition. Inhibition kinetics for the 9 most active compounds indicated non-competitive inhibition of CaE and varied mechanisms (competitive, non-competitive, or mixed-type) for inhibition of BChE. Docking simulations predicted key binding interactions of compounds with BChE and CaE and revealed that the best docked positions in BChE were at the bottom of the gorge in close proximity to the catalytic residues in the active site. In contrast, the best binding positions for CaE were clustered rather far from the active site at the top of the gorge. Thus, the docking results provided insight into differences in kinetic mechanisms and inhibitor activities of the tested compounds. A cytotoxicity test using the MTT assay showed that within solubility limits (<30 μM), none of the tested compounds significantly affected viability of human fetal mesenchymal stem cells. The results indicate that a new series of N,N-disubstituted 2-aminothiazolines could serve as BChE and CaE inhibitors for potential medicinal applications.     

Brain penetrant kinase inhibitors: Learning from kinase neuroscience discovery

A recent review of kinase inhibitors in clinical trials for brain cancer noted differences in the properties of these compounds relative to the mean property parameters associated with drugs marketed for CNS-associated conditions. However, many of these kinase drugs arose from opportunistic observations of brain activity, rather than design or flow schemes focused on optimizing CNS penetration. Thus, this digest examines kinase inhibitors that have been developed specifically for neurodegenerative indications such as Alzheimer’s or Parkinson’s disease, and considers design, flow scheme, and the physicochemical properties associated with compounds that have demonstrated brain penetrance.     

Identifying dual leucine zipper kinase (DLK) inhibitors using e-pharamacophore screening and molecular docking

Alzheimer’s is a neural disorder causing gradual loss in structure and function of nerve cell. To treat such disorders, c-Jun N-terminal Kinase (JNK) Pathway inhibitors were developed by representing chemical compounds that were used to inhibit the JNK signaling pathways. DLK is the stress sensor and implicating as regulatory factor in JNK pathway. Therefore, in the present investigation, pharmacophore screening was tried to identify the chemical compounds that involving inhibition of DLK proteins. To explore the pharmacophore region and mode of binding with DLK protein, N- (I H-pyrazol-3-y l) pyridin-2-aminer inhibitors were docked with DLK. Results reveal the information on the interaction mechanism of protein and ligand with chemical characteristics required to inhibit DLK protein. Such predicted information (AAAARH) was used as query to find out potential novel lead compounds sourced from public database. As an outcome of 65 compounds were listed based on the fitness score (2≥), and were subjected to glide HTVS.SP and XP. Best performing 5 lead compounds were shortlisted for dynamic simulations. This exhibited a constant RMSD over 20?ns of timescale.     

Synthesis,biological evaluation and molecular modeling of substituted 2-aminobenzimidazoles as novel inhibitors of acetylcholinesterase and butyrylcholinesterase

A series of novel 2-aminobenzimidazole derivatives were synthesized under microwave irradiation. Their biological activities were evaluated on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A number of the 2-aminobenzimidazole derivatives showed good inhibitory activities to AChE and BuChE. Among them, compounds 9, 12 and 13 were found to be >25-fold more selective for BuChE than AChE. No evidence of cytotoxicity was observed by MTT assay in PC12 cells or HepG2 cells exposed to 100 μM of the compounds. Molecular modeling studies indicate that the benzimidazole moiety of compounds 9, 12 and 13 forms a face-to-face π–π stacking interaction in a ‘sandwich’ form with the indole ring of Trp82 (4.09 Å) in the active gorge, and compounds 12 and 13 form a hydrogen bond with His438 at the catalytic site of BuChE. In addition, compounds 12 and 13 fit well into the hydrophobic pocket formed by Ala328, Trp430 and Tyr332 of BuChE. Our data suggest the 2-aminobenzimidazole drugs as promising new selective inhibitors for AChE and BuChE, potentially useful to treat neurodegenerative diseases.