Model Identifies Genetic Predisposition of Alzheimer's Disease as Key Decider in Cell Susceptibility to Stress.

Accumulation of unfolded/misfolded proteins in neuronal cells perturbs endoplasmic reticulum homeostasis, triggering a stress cascade called unfolded protein response (UPR), markers of which are upregulated in Alzheimer's disease (AD) brain specimens. We measured the UPR dynamic response in three human neuroblastoma cell lines overexpressing the wild-type and two familial AD (FAD)-associated mutant forms of amyloid precursor protein (APP), the Swedish and Swedish-Indiana mutations, using gene expression analysis. The results reveal a differential response to subsequent environmental stress depending on the genetic background, with cells overexpressing the Swedish variant of APP exhibiting the highest global response. We further developed a dynamic mathematical model of the UPR that describes the activation of the three branches of this stress response in response to unfolded protein accumulation. Model-based analysis of the experimental data suggests that the mutant cell lines experienced a higher protein load and subsequent magnitude of transcriptional activation compared to the cells overexpressing wild-type APP, pointing to higher susceptibility of mutation-carrying cells to stress. The model was then used to understand the effect of therapeutic agents salubrinal, lithium, and valproate on signalling through different UPR branches. This study proposes a novel integrated platform to support the development of therapeutics for AD.

Concepts and Instruments for Patient-Reported Outcome Assessment in Celiac Disease: Literature Review and Experts' Perspectives.

BACKGROUND: In diseases where there is a large subjective component, such as celiac disease (CD), patient reported-outcomes (PRO) endpoints are highly relevant. However, there is a gap in knowledge about which PRO endpoints and instruments should be used for clinical trials for treatment of celiac disease. OBJECTIVES: To identify patient-centered symptom, impact, and health-related quality of life (HRQoL) concepts in CD and relevant PRO instruments, and to gather expert input on concepts and instruments to inform selection of PRO endpoints for use in clinical trials of new CD treatments. METHODS: A targeted literature review was conducted to identify symptom, impact, and HRQoL concepts, including those captured in PROs further reviewed against U.S. Food and Drug Administration standards for development and validation as endpoints. US and European clinicians, payers, and a patient advocate (n = 21) were interviewed to assess the identified concepts' relative importance in measuring treatment benefit and to gauge the value of potential PROs as endpoints for market access/reimbursement. RESULTS: Thirty-four published studies were identified: 27 elucidated patient-centered concepts and 7 detailed the development or validation of PRO instruments. The Celiac Disease Symptom Diary and Celiac Disease Patient Reported Outcome instrument were deemed most appropriate for use as endpoints; however, each had limitations related to conceptual coverage, evidence for measurement properties, and feasibility for use in clinical trials. Experts reported gastrointestinal symptoms as most important to treat, with extra-intestinal symptoms burdensome from the patient perspective as well. Payers emphasized measuring both frequency and severity of symptoms and targeting patients nonresponsive to the gluten-free diet for treatment. CONCLUSIONS: With emerging treatment options for CD, further work is needed to operationalize PRO symptom endpoints that are meaningful to patients, valued by payers, and acceptable to regulators in demonstrating efficacy.

Exploring the conformational changes of the Munc18-1/syntaxin 1a complex.

Neurotransmitters are released from synaptic vesicles, the membrane of which fuses with the plasma membrane upon calcium influx. This membrane fusion reaction is driven by the formation of a tight complex comprising the plasma membrane N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins syntaxin-1a and SNAP-25 with the vesicle SNARE protein synaptobrevin. The neuronal protein Munc18-1 forms a stable complex with syntaxin-1a. Biochemically, syntaxin-1a cannot escape the tight grip of Munc18-1, so formation of the SNARE complex is inhibited. However, Munc18-1 is essential for the release of neurotransmitters in vivo. It has therefore been assumed that Munc18-1 makes the bound syntaxin-1a available for SNARE complex formation. Exactly how this occurs is still unclear, but it is assumed that structural rearrangements occur. Here, we used a series of mutations to specifically weaken the complex at different positions in order to induce these rearrangements biochemically. Our approach was guided through sequence and structural analysis and supported by molecular dynamics simulations. Subsequently, we created a homology model showing the complex in an altered conformation. This conformation presumably represents a more open arrangement of syntaxin-1a that permits the formation of a SNARE complex to be initiated while still bound to Munc18-1. In the future, research should investigate how this central reaction for neuronal communication is controlled by other proteins.

Population variability of rhesus macaque (Macaca mulatta) NAT1 gene for arylamine N-acetyltransferase 1: Functional effects and comparison with human.

Human NAT1 gene for N-acetyltransferase 1 modulates xenobiotic metabolism of arylamine drugs and mutagens. Beyond pharmacogenetics, NAT1 is also relevant to breast cancer. The population history of human NAT1 suggests evolution through purifying selection, but it is unclear whether this pattern is evident in other primate lineages where population studies are scarce. We report NAT1 polymorphism in 25 rhesus macaques (Macaca mulatta) and describe the haplotypic and functional characteristics of 12 variants. Seven non-synonymous single nucleotide variations (SNVs) were identified and experimentally demonstrated to compromise enzyme function, mainly through destabilization of NAT1 protein and consequent activity loss. One non-synonymous SNV (c.560G > A, p.Arg187Gln) has also been characterized for human NAT1 with similar effects. Population haplotypic and functional variability of rhesus NAT1 was considerably higher than previously reported for its human orthologue, suggesting different environmental pressures in the two lineages. Known functional elements downstream of human NAT1 were also differentiated in rhesus macaque and other primates. Xenobiotic metabolizing enzymes play roles beyond mere protection from exogenous chemicals. Therefore, any link to disease, particularly carcinogenesis, may be via modulation of xenobiotic mutagenicity or more subtle interference with cell physiology. Comparative analyses add the evolutionary dimension to such investigations, assessing functional conservation/diversification among primates.

The role of ER stress-induced apoptosis in neurodegeneration.

Post-mortem analyses of human brain tissue samples from patients suffering from neurodegenerative disorders have demonstrated dysfunction of the endoplasmic reticulum (ER). A common characteristic of the aforementioned disorders is the intracellular accumulation and aggregation of proteins due to genetic mutations or exogenous factors, leading to the activation of a stress mechanism known as the unfolded protein response (UPR). This mechanism aims to restore cellular homeostasis, however, if prolonged, can trigger pro-apoptotic signals, which are thought to contribute to neuronal cell death. The authors present evidence to support the role of ER stress-induced apoptosis in Alzheimer's, Parkinson's and Huntington's diseases, and further examine the interplay between ER dyshomeostasis and mitochondrial dysfunction, and the function of reactive oxygen species (ROS) and calcium ions (Ca(2+)) in the intricate relationship between the two organelles. Possible treatments for neurodegenerative diseases that are based on combating ER stress are finally presented.