The role of the N-methyl-d-aspartate receptor in the proliferation of adult hippocampal neural stem and precursor cells

New neurons are continuously generated from resident pools of neural stem and precursor cells(NSPCs)in the adult brain.There are multiple pathways through which adult neurogenesis is regulated,and here we review the role of the N-methyl-D-aspartate receptor(NMDAR)in regulating the proliferation of NSPCs in the adult hippocampus.Hippocampal-dependent learning tasks,enriched environments,running,and activity-dependent synaptic plasticity,all potently up-regulate hippocampal NSPC proliferation.We first consider the requirement of the NMDAR in activity-dependent synaptic plasticity,and the role the induction of synaptic plasticity has in regulating NSPCs and newborn neurons.We address how specific NMDAR agonists and antagonists modulate proliferation,both in vivo and in vitro,and then review the evidence supporting the hypothesis that NMDARs are present on NSPCs.We believe it is important to understand the mechanisms underlying the activation of adult neurogenesis,given the potential that endogenous stem cell populations have for repopulating the hippocampus with functional new neurons.In conditions such as age-related memory decline,neurodegeneration and psychiatric disease,mature neurons are lost or become defective;as such,stimulating adult neurogenesis may provide a therapeutic strategy to overcome these conditions.     

Properties of apolipoprotein E derived peptide modulate their lipid-binding capacity and influence their anti-inflammatory function

Apolipoprotein-derived peptides are promising candidates for the treatment of various inflammatory conditions. The beneficial effects of these peptides are based on multiple mechanisms; prominent among them being high-affinity binding to pro-inflammatory oxidized phospholipids (Ox-PLs) and facilitating their sequestration/metabolism/clearance in the body. This indicates that peptides which can bind exclusively to Ox-PLs without recognizing normal, non-oxidized phospholipids (non-Ox-PLs) will be more potent anti-inflammatory agent than that of the peptides that bind to both Ox-PLs and non-Ox-PLs. In order to develop such Ox-PL-specific peptides, the knowledge about the properties (molecular determinants) of peptides that govern their Ox-PL preference is a must. In this study we have synthesized eleven peptides corresponding to the conserved regions of human apolipoprotein E and compared their biochemical properties, lipid-binding specificities, and anti-inflammatory properties. Our results show that these peptides exhibit considerably different specificities towards non-Ox-PL and different species of Ox-PLs. Some of these peptides bind exclusively to the Ox-PLs and inhibit the pro-inflammatory function of Ox-PLs in human blood. Biochemical characterization revealed that the peptides possess substantially different properties. Our results suggest that physicochemical properties of peptides play an important role in their lipid-binding specificity.     

Dissecting Functions of the Conserved Oligomeric Golgi Tethering Complex Using a Cell‐Free Assay

Vesicle transport sorts proteins between compartments and is thereby responsible for generating the non‐uniform protein distribution along the eukaryotic secretory and endocytic pathways. The mechanistic details of specific vesicle targeting are not yet well characterized at the molecular level. We have developed a cell‐free assay that reconstitutes vesicle targeting utilizing the recycling of resident enzymes within the Golgi apparatus. The assay has physiological properties, and could be used to show that the two lobes of the conserved oligomeric Golgi tethering complex play antagonistic roles in trans‐Golgi vesicle targeting. Moreover, we can show that the assay is sensitive to several different congenital defects that disrupt Golgi function and therefore cause glycosylation disorders. Consequently, this assay will allow mechanistic insight into the targeting step of vesicle transport at the Golgi, and could also be useful for characterizing some novel cases of congenital glycosylation disorders.      

Src Regulates Sequence‐Dependent Beta‐2 Adrenergic Receptor Recycling via Cortactin Phosphorylation

The recycling of internalized signaling receptors, which has direct functional consequences, is subject to multiple sequence and biochemical requirements. Why signaling receptors recycle via a specialized pathway, unlike many other proteins that recycle by bulk, is a fundamental unanswered question. Here, we show that these specialized pathways allow selective control of signaling receptor recycling by heterologous signaling. Using assays to visualize receptor recycling in living cells, we show that the recycling of the beta‐2 adrenergic receptor (B2AR), a prototypic signaling receptor, is regulated by Src family kinases. The target of Src is cortactin, an essential factor for B2AR sorting into specialized recycling microdomains on the endosome. Phosphorylation of a single cortactin residue, Y466, regulates the rate of fission of B2AR recycling vesicles from these microdomains and, therefore, the rate of delivery of B2AR to the cell surface. Together, our results indicate that actin‐stabilized microdomains that mediate signaling receptor recycling can serve as a functional point of convergence for crosstalk between signaling pathways.      

Interaction of a Blumeria graminis f. sp. hordei effector candidate with a barley ARF‐GAP suggests that host vesicle trafficking is a fungal pathogenicity target

Filamentous phytopathogens, such as fungi and oomycetes, secrete effector proteins to establish successful interactions with their plant hosts. In contrast with oomycetes, little is known about effector functions in true fungi. We used a bioinformatics pipeline to identify Blumeria effector candidates (BECs) from the obligate biotrophic barley powdery mildew pathogen, Blumeria graminis f. sp. hordei (Bgh). BEC1–BEC5 are expressed at different time points during barley infection. BEC1, BEC2 and BEC4 have orthologues in the Arabidopsis thaliana‐infecting powdery mildew fungus Golovinomyces orontii. Arabidopsis lines stably expressing the G. orontii BEC2 orthologue, GoEC2, are more susceptible to infection with the non‐adapted fungus Erysiphe pisi, suggesting that GoEC2 contributes to powdery mildew virulence. For BEC3 and BEC4, we identified thiopurine methyltransferase, a ubiquitin‐conjugating enzyme, and an ADP ribosylation factor‐GTPase‐activating protein (ARF‐GAP) as potential host targets. Arabidopsis knockout lines of the respective HvARF‐GAP orthologue (AtAGD5) allowed higher entry levels of E. pisi, but exhibited elevated resistance to the oomycete Hyaloperonospora arabidopsidis. We hypothesize that ARF‐GAP proteins are conserved targets of powdery and downy mildew effectors, and we speculate that BEC4 might interfere with defence‐associated host vesicle trafficking.     

Revealing interaction between sulfobutylether‐β‐cyclodextrin and reserpine by chemiluminescence and site‐directed molecular docking

The host–guest interaction between sulfobutylether‐β‐cyclodextrin (SBE‐β‐CD) and reserpine (RSP) is described using flow injection‐chemiluminescence (FI‐CL) and site‐directed molecular docking methods. It was found that RSP could inhibit the CL intensity produced by a luminol/SBE‐β‐CD system. The decrease in CL intensity was logarithmic over an RSP concentration range of 0.03 to 700.0 nM, giving a regression equation of ?I = 107.1lgC_RES + 186.1 with a detection limit of 10 pM (3σ). The CL assay was successfully applied in the determination of RSP in injection, saliva and urine samples with recoveries in the range 93.5–106.1%. Using the proposed CL model, the binding constant (K_CD‐R) and the stoichiometric ratio of SBE‐β‐CD/RSP were calculated to be 7.4 × 10⁶ M^‐1 and 1 : 1, respectively. Using molecular docking, it was confirmed that luminol binds to the small cavity of SBE‐β‐CD with a nonpolar interaction, while RSP targeted the larger cavity of SBE‐β‐CD and formed a 1 : 1 complex with hydrogen bonds. The proposed new CL method has the potential to become a powerful tool for revealing the host–guest interaction between CDs and drugs, as well as monitoring drugs with high sensitivity. Copyright © 2013 John Wiley & Sons, Ltd.     

Anti-tubercular activity and molecular docking studies of indolizine derivatives targeting mycobacterial InhA enzyme

A series of 1,2,3-trisubstituted indolizines (2a–2f, 3a–3d, and 4a–4c) were screened for in vitro whole-cell anti-tubercular activity against the susceptible H37Rv and multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB) strains. Compounds 2b–2d, 3a–3d, and 4a–4c were active against the H37Rv-MTB strain with minimum inhibitory concentration (MIC) ranging from 4 to 32 µg/mL, whereas the indolizines 4a–4c, with ethyl ester group at the 4-position of the benzoyl ring also exhibited anti-MDR-MTB activity (MIC = 16–64 µg/mL). In silico docking study revealed the enoyl-acyl carrier protein reductase (InhA) and anthranilate phosphoribosyltransferase as potential molecular targets for the indolizines. The X-ray diffraction analysis of the compound 4b was also carried out. Further, a safety study (in silico and in vitro) demonstrated no toxicity for these compounds. Thus, the indolizines warrant further development and may represent a novel promising class of InhA inhibitors and multi-targeting agents to combat drug-sensitive and drug-resistant MTB strains.     

Apolipoprotein E in Synaptic Plasticity and Alzheimer’s Disease: Potential Cellular and Molecular Mechanisms

Alzheimer’s disease (AD) is clinically characterized with progressive memory loss and cognitive decline. Synaptic dysfunction is an early pathological feature that occurs prior to neurodegeneration and memory dysfunction. Mounting evidence suggests that aggregation of amyloid-β (Aβ) and hyperphosphorylated tau leads to synaptic deficits and neurodegeneration, thereby to memory loss. Among the established genetic risk factors for AD, the ɛ4 allele of apolipoprotein E (APOE) is the strongest genetic risk factor. We and others previously demonstrated that apoE regulates Aβ aggregation and clearance in an isoform-dependent manner. While the effect of apoE on Aβ may explain how apoE isoforms differentially affect AD pathogenesis, there are also other underexplored pathogenic mechanisms. They include differential effects of apoE on cerebral energy metabolism, neuroinflammation, neurovascular function, neurogenesis, and synaptic plasticity. ApoE is a major carrier of cholesterols that are required for neuronal activity and injury repair in the brain. Although there are a few conflicting findings and the underlying mechanism is still unclear, several lines of studies demonstrated that apoE4 leads to synaptic deficits and impairment in long-term potentiation, memory and cognition. In this review, we summarize current understanding of apoE function in the brain, with a particular emphasis on its role in synaptic plasticity and the underlying cellular and molecular mechanisms, involving low-density lipoprotein receptor-related protein 1 (LRP1), syndecan, and LRP8/ApoER2.     

In vitro and in vivo ACE inhibitory of pistachio hydrolysates and in silico mechanism of identified peptide binding with ACE

The ACE inhibitory activity of pistachio (Pistacia vera L.) kernel's hydrolysates by gastrointestinal enzymes was studied. Results indicated that hydrolysate successively hydrolyzed by pepsin and trypsin, Pe–Tr–H, presented in vitro ACE inhibitory activity as IC₅₀ 0.87 ± 0.04 mg/ml. The Pe–Tr–H can in vivo decrease around 22 mmHg in systolic blood pressure (SBP) and 16 mmHg in the diastolic blood pressure (DBP) at 4 h after the oral administration, however the pistachio kernel powder can slightly lower SBP and DBP. The Pe–Tr–H with the highest activity was then separated by ultrafiltration membrane of 3 kDa, size exclusion chromatography on Sephadex G-15 and G-10 columns and reversed phase high-performance liquid chromatography (RP-HPLC) consecutively. A novel ACE inhibitory peptide, ACKEP, with the IC₅₀ value of 126 μM, was identified by MALDI–TOF/TOF system. ACKEP has the same C-terminal residue as Lisinopril and Enalapril, which plays a key role in binding with ACE. The binding mechanism was explored at a molecular basis by docking experiments, which revealed that seven residues from ACE active site (His383, His387, Glu384, Arg522, Asp358, Ala356 and Asn70) and two atoms of ACKEP (O5, H60) greatly contributed to the combinative stabilization.