Lysosomal storage, impaired autophagy and innate immunity in Gaucher and Parkinson's diseases: insights for drug discovery.

Impairment of autophagic-lysosomal pathways is increasingly being implicated in Parkinson's disease (PD). GBA1 mutations cause the lysosomal storage disorder Gaucher disease (GD) and are the commonest known genetic risk factor for PD. GBA1 mutations have been shown to cause autophagic-lysosomal impairment. Defective autophagic degradation of unwanted cellular constituents is associated with several pathologies, including loss of normal protein homeostasis, particularly of α-synuclein, and innate immune dysfunction. The latter is observed both peripherally and centrally in PD and GD. Here, we will discuss the mechanistic links between autophagy and immune dysregulation, and the possible role of these pathologies in communication between the gut and brain in these disorders. Recent work in a fly model of neuronopathic GD (nGD) revealed intestinal autophagic defects leading to gastrointestinal dysfunction and immune activation. Rapamycin treatment partially reversed the autophagic block and reduced immune activity, in association with increased survival and improved locomotor performance. Alterations in the gut microbiome are a critical driver of neuroinflammation, and studies have revealed that eradication of the microbiome in nGD fly and mouse models of PD ameliorate brain inflammation. Following these observations, lysosomal-autophagic pathways, innate immune signalling and microbiome dysbiosis are discussed as potential therapeutic targets in PD and GD. This article is part of a discussion meeting issue 'Understanding the endo-lysosomal network in neurodegeneration'.

Autophagic dysfunction and gut microbiota dysbiosis cause chronic immune activation in a Drosophila model of Gaucher disease.

Mutations in the GBA1 gene cause the lysosomal storage disorder Gaucher disease (GD) and are the greatest known genetic risk factors for Parkinson's disease (PD). Communication between the gut and brain and immune dysregulation are increasingly being implicated in neurodegenerative disorders such as PD. Here, we show that flies lacking the Gba1b gene, the main fly orthologue of GBA1, display widespread NF-kB signalling activation, including gut inflammation, and brain glial activation. We also demonstrate intestinal autophagic defects, gut dysfunction, and microbiome dysbiosis. Remarkably, modulating the microbiome of Gba1b knockout flies, by raising them under germ-free conditions, partially ameliorates lifespan, locomotor and immune phenotypes. Moreover, we show that modulation of the immune deficiency (IMD) pathway is detrimental to the survival of Gba1 deficient flies. We also reveal that direct stimulation of autophagy by rapamycin treatment achieves similar benefits to germ-free conditions independent of gut bacterial load. Consistent with this, we show that pharmacologically blocking autophagosomal-lysosomal fusion, mimicking the autophagy defects of Gba1 depleted cells, is sufficient to stimulate intestinal immune activation. Overall, our data elucidate a mechanism whereby an altered microbiome, coupled with defects in autophagy, drive chronic activation of NF-kB signaling in a Gba1 loss-of-function model. It also highlights that elimination of the microbiota or stimulation of autophagy to remove immune mediators, rather than prolonged immunosuppression, may represent effective therapeutic avenues for GBA1-associated disorders.

Signatures of Reaction Mechanisms Encoded in the Vibrational Population Distribution of Small-Molecule Products: Photodissociation of Symmetric-Triazine Using 266 nm Radiation.

We utilize rotationally resolved Chirped-Pulse Fourier Transform millimeter-wave spectroscopy to study photodissociation dynamics of 1,3,5-Triazine (symmetric-Triazine) to form 3 HCN molecules. The state-specific vibrational population distribution (VPD) of the photofragments contains mechanistic details of the reaction. This photodissociation is performed using 266 nm radiation transverse to a seeded supersonic jet. The vibrational cooling inefficiency in the jet preserves the VPD of the photofragments, while rotational cooling enhances the signal of low-J pure-rotational transitions. The multiplexed nature of the spectrometer enables simultaneous sampling of several "vibrational satellites" of the J = 1 ← 0 transition of HCN. Excited state populations along the HCN bend (v2) and CN stretch (v3) modes are observed, which show ≥3.2% vibrational excitation of the photofragments. Observation of an at least bimodal VPD, along the even-v states of v2, implies an asymmetric partitioning of vibrational energy among the HCN photofragments. This suggests a sequential dissociation mechanism of symmetric-Triazine initiated by 266 nm radiation.

Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila.

G4C2 repeat expansions within the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The repeats undergo repeat-associated non-ATG translation to generate toxic dipeptide repeat proteins. Here, we show that insulin/IGF signalling is reduced in fly models of C9orf72 repeat expansion using RNA sequencing of adult brain. We further demonstrate that activation of insulin/IGF signalling can mitigate multiple neurodegenerative phenotypes in flies expressing either expanded G4C2 repeats or the toxic dipeptide repeat protein poly-GR. Levels of poly-GR are reduced when components of the insulin/IGF signalling pathway are genetically activated in the diseased flies, suggesting a mechanism of rescue. Modulating insulin signalling in mammalian cells also lowers poly-GR levels. Remarkably, systemic injection of insulin improves the survival of flies expressing G4C2 repeats. Overall, our data suggest that modulation of insulin/IGF signalling could be an effective therapeutic approach against C9orf72 ALS/FTD.

Into the breach: how cells cope with wounds.

Repair of wounds to individual cells is crucial for organisms to survive daily physiological or environmental stresses, as well as pathogen assaults, which disrupt the plasma membrane. Sensing wounds, resealing membranes, closing wounds and remodelling plasma membrane/cortical cytoskeleton are four major steps that are essential to return cells to their pre-wounded states. This process relies on dynamic changes of the membrane/cytoskeleton that are indispensable for carrying out the repairs within tens of minutes. Studies from different cell wound repair models over the last two decades have revealed that the molecular mechanisms of single cell wound repair are very diverse and dependent on wound type, size, and/or species. Interestingly, different repair models have been shown to use similar proteins to achieve the same end result, albeit sometimes by distinctive mechanisms. Recent studies using cutting edge microscopy and molecular techniques are shedding new light on the molecular mechanisms during cellular wound repair. Here, we describe what is currently known about the mechanisms underlying this repair process. In addition, we discuss how the study of cellular wound repair-a powerful and inducible model-can contribute to our understanding of other fundamental biological processes such as cytokinesis, cell migration, cancer metastasis and human diseases.

Uptake of Pyrene onto Fatty Acid Coated NaCl Aerosol Particles.

Photoelectric charging experiments monitor the uptake of pyrene onto NaCl aerosol particles coated with either oleic acid or myristic acid. In both cases, thin coatings produce a small net decrease in pyrene uptake. In the larger coverage limit, the uptake of the myristic acid coated particles remains nearly constant whereas the oleic acid coated particles exhibit greater uptake rates than the bare NaCl particles. Fitting the results with a multilayer kinetic model yields uptake rate coefficients as well as parameters that describe the distribution of organic molecules on the aerosol particle surface. The model accounts for the decrease in uptake associated with thin coatings of oleic acid through a concomitant reduction in surface area. The adsorption rate constants for the myristic and oleic acid coated surfaces are 50 and 80 times faster, respectively, than for NaCl. The desorption rates for pyrene on the fatty acid surfaces are faster, as well. For myristic acid coatings, the fast desorption (over 400 times the rate of desorption from NaCl) results in slower net adsorption, whereas for oleic acid (approximately 12 times the desorption rate from NaCl), the net uptake rate increases with coverage. The results also suggest that both myristic acid and oleic acid spread incompletely on the aerosol surfaces under the conditions of these experiments. In the optimized kinetic model, the fatty acids cover approximately 50% of the surface when the nominal coating thickness is approximately 6 nm. The surface is over 90% covered with a nominal coating thickness of 20 nm, which is approximately 10% of particle diameter in these experiments. Very thin oleic acid coatings reduce the surface area of particles consistent with the preferential coverage of highly corrugated or porous regions.