Genetic and environmental factors, such as metals, interact to determine neurological traits. We reasoned that interactomes of molecules handling metals in neurons should include novel metal homeostasis pathways. We focused on copper and its transporter ATP7A because ATP7A null mutations cause neurodegeneration. We performed ATP7A immunoaffinity chromatography and identified 541 proteins co-isolating with ATP7A. The ATP7A interactome concentrated gene products implicated in neurodegeneration and neurodevelopmental disorders, including subunits of the Golgi-localized conserved oligomeric Golgi (COG) complex. COG null cells possess altered content and subcellular localization of ATP7A and CTR1 (SLC31A1), the transporter required for copper uptake, as well as decreased total cellular copper, and impaired copper-dependent metabolic responses. Changes in the expression of ATP7A and COG subunits in Drosophila neurons altered synapse development in larvae and copper-induced mortality of adult flies. We conclude that the ATP7A interactome encompasses a novel COG-dependent mechanism to specify neuronal development and survival.DOI: http://dx.doi.org/10.7554/eLife.24722.001

No abstract

Environmental factors and susceptible genomes interact to determine the risk of neurodevelopmental disorders. Although few genes and environmental factors have been linked, the intervening cellular and molecular mechanisms connecting a disorder susceptibility gene with environmental factors remain mostly unexplored. Here we focus on the schizophrenia susceptibility gene DTNBP1 and its product dysbindin, a subunit of the BLOC-1 complex, and describe a neuronal pathway modulating copper metabolism via ATP7A. Mutations in ATP7A result in Menkes disease, a disorder of copper metabolism. Dysbindin/BLOC-1 and ATP7A genetically and biochemically interact. Furthermore, disruption of this pathway causes alteration in the transcriptional profile of copper-regulatory and dependent factors in the hippocampus of dysbindin/BLOC-1-null mice. Dysbindin/BLOC-1 loss-of-function alleles do not affect cell and tissue copper content, yet they alter the susceptibility to toxic copper challenges in both mammalian cells and Drosophila. Our results demonstrate that perturbations downstream of the schizophrenia susceptibility gene DTNBP1 confer susceptibility to copper, a metal that in excess is a neurotoxin and whose depletion constitutes a micronutrient deficiency.

Oxidative stress remains one of the most well studied, albeit somewhat contentious, causes of aging-related changes in humans. Consequently, a large number of putative antioxidant compounds are freely available in myriad formulations that are often not tested for their efficacy or regulated for quality control. Following the development of a Drosophila model of oxidative-stress dependent aging (p38 MAP Kinase (p38K) mutants) in our laboratory, we attempted to test the protective effect of some of these commonly available formulations against oxidative stress, stress induced motor defects and reduced life span in the p38K model. As environmental exposure to oxidizing toxins has been linked to a variety of human diseases, we also tested the efficacy of these supplements on chemically-induced models of oxidative stress (Paraquat and Hydrogen Peroxide exposure). Our results suggest that when added as a dietary supplement, some of these over-the-counter compounds, notably containing Açai extracts, confer significant protection for both the p38K-dependent genetic model as well as the toxin-induced model. These products were also remarkably effective at dampening stress-induced expression of the detoxifying enzyme GSTD1 and eliminating Paraquat induced circadian rhythm deficits. Overall, our results suggest potential benefits of dietary supplementation with some of these compounds, especially under conditions of elevated oxidative stress. These findings should be assessed in the context of other studies that seek to identify active principles in these extracts, determine their effective dosage for human consumption and evaluate the safety of long-term prophylactic applications.

The large repertoire of circadian rhythms in diverse organisms depends on oscillating central clock genes, input pathways for entrainment, and output pathways for controlling rhythmic behaviors. Stress-activated p38 MAP Kinases (p38K), although sparsely investigated in this context, show circadian rhythmicity in mammalian brains and are considered part of the circadian output machinery in Neurospora. We find that Drosophila p38Kb is expressed in clock neurons, and mutants in p38Kb either are arrhythmic or have a longer free-running periodicity, especially as they age. Paradoxically, similar phenotypes are observed through either transgenic inhibition or activation of p38Kb in clock neurons, suggesting a requirement for optimal p38Kb function for normal free-running circadian rhythms. We also find that p38Kb genetically interacts with multiple downstream targets to regulate circadian locomotor rhythms. More specifically, p38Kb interacts with the period gene to regulate period length and the strength of rhythmicity. In addition, we show that p38Kb suppresses the arrhythmic behavior associated with inhibition of a second p38Kb target, the transcription factor Mef2. Finally, we find that manipulating p38K signaling in free-running conditions alters the expression of another downstream target, MNK/Lk6, which has been shown to cycle with the clock and to play a role in regulating circadian rhythms. These data suggest that p38Kb may affect circadian locomotor rhythms through the regulation of multiple downstream pathways.