A feedforward loop links Gaucher and Parkinson's diseases?

Mutations in the GBA gene that encodes glucocerebrosidase cause the lysosomal storage disorder Gaucher disease but also increase the risk for Parkinson's disease. Mazzulli et?al. (2011) uncover a possible mechanism to explain this connection: loss of glucocerebrosidase creates a positive feedback loop of reduced lysosomal function and α-synuclein accumulation, ultimately leading to neurodegeneration.     

Gaucher disease and brucella: just a mere coincidence?

Gaucher disease type I and brucellosis are chronic diseases with similar symptoms and physical signs though the former is the most common lysosomal storage disease and the latter is an infectious disease. The similarities between these diseases make differential diagnosis difficult. Immunodeficiency is a feature of Gaucher disease type I and increases the susceptibility towards infections. A Gaucher disease type I patient with brucellosis is presented with improvement after treatment of brucellosis.     

Activation of p38 Mitogen-Activated Protein Kinase in Gaucher’s Disease

Gaucher’s disease is caused by defects in acid β-glucosidase 1 (GBA1) and has been also proposed as an inflammatory disease. GBA1 cleaves glucosylceramide to form ceramide, an established bioactive lipid, and defects in GBA1 lead to aberrant accumulation in glucosylceramide and insufficient formation of ceramide. We investigated if the pro-inflammatory kinase p38 is activated in Gaucher’s disease, since ceramide has been proposed to suppress p38 activation. Three Gaucher’s disease mouse models were employed, and p38 was found to be activated in lung and liver tissues of all Gaucher’s disease mice. Most interestingly, neuronopathic Gaucher’s disease type mice, but not non-neuronopathic ones, displayed significant activation of p38 and up-regulation of p38-inducible proinflammatory cytokines in brain tissues. In addition, all type of Gaucher’s disease mice also showed increases in serum IL-6. As cellular signalling is believed to represent an in vivo inflammatory phenotype in Gaucher’s disease, activation of p38 and possibly its-associated formation of proinflammatory cytokines were assessed in fibroblasts established from neuronopathic Gaucher’s disease mice. In mouse Gaucher’s disease cells, p38 activation and IL-6 formation by TNF-α treatment were enhanced as compared to those of wild type. Furthermore, human fibroblasts from Gaucher’s disease patients also displayed increases in p38 activation and IL-6 formation as comparison to healthy counterpart. These results raise the potential that proinflammatory responses such as p38 activation and IL-6 formation are augmented in Gaucher’s disease.     

Restoration of β-GC trafficking improves the lysosome function in Gaucher disease

Lysosomes function as a primary site for catabolism and cellular signaling. These organelles digest a variety of substrates received through endocytosis, secretion and autophagy with the help of resident acid hydrolases. Lysosomal enzymes are folded in the endoplasmic reticulum (ER) and trafficked to lysosomes via Golgi and endocytic routes. The inability of hydrolase trafficking due to mutations or mutations in its receptor or cofactor leads to cargo accumulation (storage) in lysosomes, resulting in lysosome storage disorder (LSD). In Gaucher disease (GD), the lysosomes accumulate glucosylceramide because of low β-glucocerebrosidase (β-GC) activity that causes lysosome enlargement/dysfunction. We hypothesize that improving the trafficking of mutant β-GC to lysosomes may improve the lysosome function in GD. RNAi screen using high throughput based β-GC activity assay followed by reporter trafficking assay utilizing β-GC-mCherry led to the identification of nine potential phosphatases. Depletion of these phosphatases in HeLa cells enhanced the β-GC activity by increasing the folding and trafficking of Gaucher mutants to the lysosomes. Consistently, the lysosomes in primary fibroblasts from GD patients restored their β-GC activity upon the knockdown of these phosphatases. Thus, these studies provide evidence that altering phosphatome activity is an alternative therapeutic strategy to restore the lysosome function in GD.     

Gaucher disease glucocerebrosidase and α-synuclein form a bidirectional pathogenic loop in synucleinopathies

Parkinson's disease (PD), an adult neurodegenerative disorder, has been clinically linked to the lysosomal storage disorder Gaucher disease (GD), but the mechanistic connection is not known. Here, we show that functional loss of GD-linked glucocerebrosidase (GCase) in primary cultures or human iPS neurons compromises lysosomal protein degradation, causes accumulation of α-synuclein (α-syn), and results in neurotoxicity through aggregation-dependent mechanisms. Glucosylceramide (GlcCer), the GCase substrate, directly influenced amyloid formation of purified α-syn by stabilizing soluble oligomeric intermediates. We further demonstrate that α-syn inhibits the lysosomal activity of normal GCase in neurons and idiopathic PD brain, suggesting that GCase depletion contributes to the pathogenesis of sporadic synucleinopathies. These findings suggest that the bidirectional effect of α-syn and GCase forms a positive feedback loop that may lead to a self-propagating disease. Therefore, improved targeting of GCase to lysosomes may represent a specific therapeutic approach for PD and other synucleinopathies.     

Uncoupling of osteoblast–osteoclast regulation in a chemical murine model of Gaucher disease

Gaucher disease (GD) is caused by mutations in the GBA gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to accumulation of the glycolipid glucocerebroside in the lysosomes of cells of monocyte/macrophage system. Type I GD is the mildest form and is characterized by the absence of neuronopathic affection. Bone compromise in Gaucher disease patients is the most disabling aspect of the disease. However, pathophysiological aspects of skeletal alterations are still poorly understood.     

Are titin properties reflected in single myofibrils?

Titin is a structural protein in muscle that spans the half sarcomere from Z-band to M-line. Although there are selected studies on titin's mechanical properties from tests on isolated molecules or titin fragments, little is known about its behavior within the structural confines of a sarcomere. Here, we tested the hypothesis that titin properties might be reflected well in single myofibrils. Single myofibrils from rabbit psoas were prepared for measurement of passive stretch-shortening cycles at lengths where passive titin forces occur. Three repeat stretch-shortening cycles with magnitudes between 1.0 and 3.0μm/sarcomere were performed at a speed of 0.1μm/s·sarcomere and repeated after a ten minute rest at zero force. These tests were performed in a relaxation solution (passive) and an activation solution (active) where cross-bridge attachment was inhibited with 2,3 butanedionemonoxime. Myofibrils behaved viscoelastically producing an increased efficiency with repeat stretch-shortening cycles, but a decreased efficiency with increasing stretch magnitudes. Furthermore, we observed a first distinct inflection point in the force-elongation curve at an average sarcomere length of 3.5μm that was associated with an average force of 68±5nN/mm. This inflection point was thought to reflect the onset of Ig domain unfolding and was missing after a ten minute rest at zero force, suggesting a lack of spontaneous Ig domain refolding. These passive myofibrillar properties observed here are consistent with those observed in isolated titin molecules, suggesting that the mechanics of titin are well preserved in isolated myofibrils, and thus, can be studied readily in myofibrils, rather than in the extremely difficult and labile single titin preparations.     

Two phosphatidylinositol 4-kinases control lysosomal delivery of the Gaucher disease enzyme, β-glucocerebrosidase

Gaucher disease is a lysosomal storage disorder caused by a defect in the degradation of glucosylceramide catalyzed by the lysosomal enzyme β-glucocerebrosidase (GBA). GBA reaches lysosomes via association with its receptor, lysosomal integral membrane protein type 2 (LIMP-2). We found that distinct phosphatidylinositol 4-kinases (PI4Ks) play important roles at multiple steps in the trafficking pathway of the LIMP-2/GBA complex. Acute depletion of phosphatidylinositol 4-phosphate in the Golgi caused accumulation of LIMP-2 in this compartment, and PI4KIIIβ was found to be responsible for controlling the exit of LIMP-2 from the Golgi. In contrast, depletion of PI4KIIα blocked trafficking at a post-Golgi compartment, leading to accumulation of LIMP-2 in enlarged endosomal vesicles. PI4KIIα depletion also caused secretion of missorted GBA into the medium, which was attenuated by limiting LIMP-2/GBA exit from the Golgi by PI4KIIIβ inhibitors. These studies identified PI4KIIIβ and PI4KIIα as important regulators of lysosomal delivery of GBA, revealing a new element of control to sphingolipid homeostasis by phosphoinositides.     

Does life originate from a single molecule?

Life did not emerge in a single step. In chemical evolution, the first formation of a self-replicating molecule was probably one of the most critical bottlenecks, which was overcome only with a very low probability. If only one such event was successful, present-day life originates from a single molecule. In this case, homochirality in DNA and RNA is explained almost without further assumptions. By contrast, the enantiomer excess, produced by the deterministic mechanisms suggested so far, is smaller than the statistical standard deviation, unless the postulated initial number of molecules is very--in some mechanisms unreasonably--large. A certain chiral nonuniformity of natural monosaccharides other than (deoxy)ribose supports the idea that homochirality originates not from such small molecules but from an early RNA-like oligomer. This nonuniformity seems also hard to explain by any deterministic mechanism.     

Enzyme enhancement activity of N-octyl-β-valienamine on β-glucosidase mutants associated with Gaucher disease

Gaucher disease (GD), caused by a defect of β-glucosidase (β-Glu), is the most common form of sphingolipidosis. We have previously shown that a carbohydrate mimic N-octyl-β-valienamine (NOV), an inhibitor of β-Glu, could increase the protein level and enzyme activity of F213I mutant β-Glu in cultured GD fibroblasts, suggesting that NOV acted as a pharmacological chaperone to accelerate transport and maturation of this mutant enzyme. In the current study, NOV effects were evaluated in GD fibroblasts with various β-Glu mutations and in COS cells transiently expressing recombinant mutant proteins. In addition to F213I, NOV was effective on N188S, G202R and N370S mutant forms of β-Glu, whereas it was ineffective on G193W, D409H and L444P mutants. When expressed in COS cells, the mutant proteins as well as the wild-type protein were localized predominantly in the endoplasmic reticulum and were sensitive to Endo-H treatment. NOV did not alter this localization or Endo-H sensitivity, suggesting that it acted in the endoplasmic reticulum. Profiling of N-alkyl-β-valienamines with various lengths of the acyl chain showed that N-dodecyl-β-valienamine was as effective as NOV. These results suggest a potential therapeutic value of NOV and related compounds for GD with a broad range of β-Glu mutations.     

A single origin of the central nervous system?

As Denes et al. (2007) reveal in this issue, the expression profile and roles of genes that pattern the nervous system in embryos of chordates and annelids are surprisingly similar. This extraordinary conservation suggests that the patterning mechanism has been inherited largely unchanged from the bilaterian common ancestor and that the central nervous system, although dorsal in fish and ventral in worms, is an ancient characteristic of animals.     

Cutting the forest to see a single tree?

The development of single-molecule tools has significantly impacted the way we think about biochemical processes. Watching a single protein in action allows us to observe kinetic details and rare subpopulations that are hidden in ensemble-averaging techniques. I will discuss here the pros and cons of the single-molecule approach in studying ligand binding in macromolecular systems and how these techniques can be applied to characterize the behavior of large multicomponent biochemical systems.     

Is there a single biochemical adaptation to anhydrobiosis?

Even though water is required for the maintenance of biologicalintegrity, numerous organisms are capable of surviving lossof virtually all their cellular water and existing in a stateknown as anhydrobiosis. Over the past three decades we and othershave established that disaccharides such as trehalose and sucroseare almost certainly involved in stabilizing the dry cells.We discuss here some of the evidence behind the mechanism ofthis stabilization. Until the past few years this mechanismhas been sufficiently appealing that a consensus has been developingthat acquisition of these sugars in the cytoplasm may be bothnecessary and sufficient for anhydrobiosis. We show here thatthere are other routes to achieve the effects conferred by thesugars and that other adaptations are almost certainly required,at least in environmental conditions that are less than optimal.Under optimal storage conditions, the presence of the sugarsalone may be sufficient to stabilize even mammalian cells inthe dry state, findings that are already finding use in humanclinical medicine.     

Triclosan-bacteria interactions: single or multiple target sites?

AIMS: To investigate the inhibitory and lethal effects of triclosan against several micro-organisms at different stages of their phase of population growth. METHODS AND RESULTS: Triclosan minimum inhibitory concentrations against several test organisms were determined in broth and agar using standard protocols. The bisphenol effect on bacterial population growth kinetics was studied using the Bioscreen C microbial growth analyser. Finally, the efficacy of triclosan on phases of bacterial growth was determined using a standard suspension test. The duration of the lag phase for all micro-organisms tested was increased by bisphenol in a concentration-dependent manner. The population growth kinetics of the micro-organisms was also altered after biocide exposure. At higher concentrations, triclosan was bactericidal regardless of their phase of population growth, although population in stationary phase and particularly, washed suspensions, were more resilient to the lethality of triclosan. This lethal activity was concentration and contact time dependent, and in some instances, bactericidal activity of bisphenol was observed within 15 s. CONCLUSIONS: Low concentrations of triclosan affected the growth of several bacteria, while higher concentrations were bactericidal regardless of the bacterial phase of population growth. SIGNIFICANCE AND IMPACT OF THE STUDY: Here, we presented clear evidence that the interaction of triclosan with the bacterial cell is complex and its lethality cannot be explained solely by the inhibition of metabolic pathways such as the enoyl acyl-reductase. However, the inhibition of such pathways cannot be ruled out as part of the lethal mechanism of the bisphenol at a low bactericidal concentration.     

Influence of a single γ-irradiation on rat microflora

Changes in leukocyte counts and in the gut microflora of laboratory rats irradiated with a single whole-body dose of γ rays (5.0 Gy) were determined. The number of leukocytes was lower especially 1 and 2 weeks after irradiation. A significant decrease in lymphocytes was observed 1 week and in monocytes 1 and 2 weeks after irradiation. In parallel with these changes, an increase in common microflora was observed; some microorganisms, which normally are not present in duodenum, liver and mouth cavity, were detected in these organs.