William J. Ray

Oxysterol-binding protein-1 (OSBP1) modulates processing and trafficking of the amyloid precursor protein

BackgroundEvidence from biochemical, epidemiological and genetic findings indicates that cholesterol levels are linked to amyloid-β (Aβ) production and Alzheimers disease (AD). Oxysterols, which are cholesterol-derived ligands of the liver X receptors (LXRs) and oxysterol binding proteins, strongly regulate the processing of amyloid precursor protein (APP). Although LXRs have been studied extensively, little is known about the biology of oxysterol binding proteins. Oxysterol-binding protein 1 (OSBP1) is a member of a family of sterol-binding proteins with roles in lipid metabolism, regulation of secretory vesicle generation and signal transduction, and it is thought that these proteins may act as sterol sensors to control a variety of sterol-dependent cellular processes.ResultsWe investigated whether OSBP1 was involved in regulating APP processing and found that overexpression of OSBP1 downregulated the amyloidogenic processing of APP, while OSBP1 knockdown had the opposite effect. In addition, we found that OSBP1 altered the trafficking of APP-Notch2 dimers by causing their accumulation in the Golgi, an effect that could be reversed by treating cells with OSBP1 ligand, 25-hydroxycholesterol.ConclusionThese results suggest that OSBP1 could play a role in linking cholesterol metabolism with intracellular APP trafficking and Aβ production, and more importantly indicate that OSBP1 could provide an alternative target for Aβ-directed therapeutic.

Genome-Wide Microarray Analysis of the Differential Neuroprotective Effects of Antioxidants in Neuroblastoma Cells Overexpressing the Familial Parkinson’s Disease α-Synuclein A53T Mutation

In Parkinson’s disease substantia nigra neurons degenerate likely due to oxidative damage interacting with genetic risk factors. Here, SH-SY5Y cells expressing wild-type or A53T α-synuclein had increased sensitivity to methyl-4-phenylpyridinium iodide (MPP+), which induces mitochondrial dysfunction, and 6-hydroxydopamine (6-OHDA), which causes oxidative stress. Edaravone protected only against MPP+, and EGCG ((−)-epigallocatechin-3-O-gallate) protected only against 6-OHDA. Thus genomic responses to MPP+ and 6-OHDA in the presence of these antioxidants were analyzed using microarrays. Pathway analysis indicated that MPP+ activated p53 (Pxa0<xa00.001) while 6-OHDA induced the Nrf2 antioxidative stress response (Pxa0<xa00.0001). EGCG was more effective at blocking 6-OHDA-mediated genomic responses, while edaravone was more effective against MPP+. We identified 32 genes that responded to both toxins except in the presence of an effective anti-oxidant; eight are transcription factors and potentially constitute a stress-response transcriptional network. These data provide insights into the mechanisms of neurotoxicity and identifies genes that might mediate antioxidant efficacy.

Pathway-Based Analysis of Genome-Wide siRNA Screens Reveals the Regulatory Landscape of App Processing

The progressive aggregation of Amyloid-β (Aβ) in the brain is a major trait of Alzheimers Disease (AD). Aβ is produced as a result of proteolytic processing of the β-amyloid precursor protein (APP). Processing of APP is mediated by multiple enzymes, resulting in the production of distinct peptide products: the non-amyloidogenic peptide sAPPα and the amyloidogenic peptides sAPPβ, Aβ40, and Aβ42. Using a pathway-based approach, we analyzed a large-scale siRNA screen that measured the production of different APP proteolytic products. Our analysis identified many of the biological processes/pathways that are known to regulate APP processing and have been implicated in AD pathogenesis, as well as revealing novel regulatory mechanisms. Furthermore, we also demonstrate that some of these processes differentially regulate APP processing, with some mechanisms favouring production of certain peptide species over others. For example, synaptic transmission having a bias towards regulating Aβ40 production over Aβ42 as well as processes involved in insulin and pancreatic biology having a bias for sAPPβ production over sAPPα. In addition, some of the pathways identified as regulators of APP processing contain genes (CLU, BIN1, CR1, PICALM, TREM2, SORL1, MEF2C, DSG2, EPH1A) recently implicated with AD through genome wide association studies (GWAS) and associated meta-analysis. In addition, we provide supporting evidence and a deeper mechanistic understanding of the role of diabetes in AD. The identification of these processes/pathways, their differential impact on APP processing, and their relationships to each other, provide a comprehensive systems biology view of the “regulatory landscape” of APP.

Adenosine analogue inhibitors of S-adenosylhomocysteine hydrolase.

Elevated plasma homocysteine (Hcy) levels are an independent risk factor for the onset and progression of Alzheimers disease. Reduction of Hcy to normal levels therefore presents a new approach for disease modification. Hcy is produced by the cytosolic enzyme S-adenosylhomocysteine hydrolase (AHCY), which converts S-adenosylhomocysteine (SAH) to Hcy and adenosine. Herein we describe the design and characterization of novel, substrate-based S-adenosylhomocysteine hydrolase inhibitors with low nanomolar potency in vitro and robust activity in vivo.

MK-7622: A First-in-Class M1 Positive Allosteric Modulator Development Candidate

Identification of ligands that selectively activate the M1 muscarinic signaling pathway has been sought for decades to treat a range of neurological and cognitive disorders. Herein, we describe the optimization efforts focused on addressing key physicochemical and safety properties, ultimately leading to the clinical candidate MK-7622, a highly selective positive allosteric modulator of the M1 muscarinic receptor that has entered Phase II studies in patients with Alzheimers disease.

P1-016: Dietary induction of hyperhomocystemia and the impact on Alzheimer's disease-relevant markers

primary antibodies against S-100 (Sigma) followed by secondary GAM (Sigma) and then revealed by ABC-DAB solutions. The mounted slices were analyzed under light microscope with the Norten-Eclipse program, using threshold gray levels for intraand extra cellular contents. Results: S100 interestingly is distributed in CNS, specially around the ventricles, choroids plexus, near the pyramidal cells of the Cerebral Cortex and near the Cerebellar Purkinje Cells. The analysed results showed that S100 has a bimodal expression that peaks at 5.00 h for female and 21 h for males, and a lower peak was observed respectively at 13,00 h and 17, 00 h. These results are supported by previous preliminaries scintillation counting studies with S100 in normal and knockout mice and by some previous research in S-100 blood serum. Conclusions: These results showing gender time and age variations in S-100 should be considered in clinical therapeutics strategies aimed at regulating neuroplasticity.