Beta-synuclein regulates Akt activity in neuronal cells. A possible mechanism for neuroprotection in Parkinson's disease

Recent studies have shown that the neurodegenerative process in disorders with Lewy body formation, such as Parkinson's disease and dementia with Lewy bodies, is associated with alpha-synuclein accumulation and that beta-synuclein might protect the central nervous system from the neurotoxic effects of alpha-synuclein. However, the mechanisms are unclear. The main objective of the present study was to investigate the potential involvement of the serine threonine kinase Akt (also known as protein kinase B) signaling pathway in the mechanisms of beta-synuclein neuroprotection. For this purpose, Akt activity and cell survival were analyzed in synuclein-transfected B103 neuroblastoma cells and primary cortical neurons. Beta-synuclein transfection resulted in increased Akt activity and conferred protection from the neurotoxic effects of rotenone. Down-regulation of Akt expression resulted in an increased susceptibility to rotenone toxicity, whereas transfection with a lentiviral vector encoding for beta-synuclein was protective. The effects of beta-synuclein on the Akt pathway appear to be by direct interaction between these molecules and were independent of upstream signaling molecules. Taken together, these results indicate that the mechanisms of beta-synuclein neuroprotection might involve direct interactions between beta-synuclein and Akt and suggest that this signaling pathway could be a potential therapeutic target for neurological conditions associated with parkinsonism and alpha-synuclein aggregation.     

Hepatic mTORC2 activates glycolysis and lipogenesis through Akt, glucokinase, and SREBP1c

Mammalian target of rapamycin complex 2 (mTORC2) phosphorylates and activates AGC kinase family members, including Akt, SGK1, and PKC, in response to insulin/IGF1. The liver is a key organ in insulin-mediated regulation of metabolism. To assess the role of hepatic mTORC2, we generated liver-specific rictor knockout (LiRiKO) mice. Fed LiRiKO mice displayed loss of Akt Ser473 phosphorylation and reduced glucokinase and SREBP1c activity in the liver, leading to constitutive gluconeogenesis, and impaired glycolysis and lipogenesis, suggesting that the mTORC2-deficient liver is unable to sense satiety. These liver-specific defects resulted in systemic hyperglycemia, hyperinsulinemia, and hypolipidemia. Expression of constitutively active Akt2 in mTORC2-deficient hepatocytes restored both glucose flux and lipogenesis, whereas glucokinase overexpression rescued glucose flux but not lipogenesis. Thus, mTORC2 regulates hepatic glucose and lipid metabolism via insulin-induced Akt signaling to control whole-body metabolic homeostasis. These findings have implications for emerging drug therapies that target mTORC2.     

Effects of the cholesterol-lowering compound methyl-beta-cyclodextrin in models of alpha-synucleinopathy

The aggregation of alpha-synuclein (alpha-syn) is believed to play a critical role in the pathogenesis of disorders such as dementia with Lewy bodies and Parkinson's disease. The function of alpha-syn remains unclear, although several lines of evidence suggest that alpha-syn is involved in synaptic vesicle trafficking, probably via lipid binding, and interactions with lipids have been shown to regulate alpha-syn aggregation. In this context, the main objective of this study was to determine whether methyl-beta-cyclodextrin (MbetaCD), a cholesterol-extracting agent, interfered with alpha-syn accumulation in models of synucleinopathy. For this purpose, we studied the effects of MbetaCD on the accumulation of alpha-syn in a transfected neuronal cell line and in transgenic mice. Immunoblot analysis showed that MbetaCD reduced the level of alpha-syn in the membrane fraction and detergent-insoluble fraction of transfected cells. In agreement with the in vitro studies, treatment of mice with MbetaCD resulted in decreased levels of alpha-syn in membrane fractions and reduced accumulation of alpha-syn in the neuronal cell body and synapses. Taken together, these results suggest that changes in cholesterol and lipid composition using cholesterol-lowering agents may be used as a tool for the treatment of synucleinopathies.     

Ligand-independent regulation of ErbB4 receptor phosphorylation by activated Ras

The ErbB family of receptor tyrosine kinases regulates cell growth, differentiation and survival. Activation of the receptors is induced by specific growth factors in an autocrine, paracrine or juxtacrine manner. The activated ErbB receptors turn on a large variety of signaling cascades, including the prominent Ras-dependent signaling pathways. The activated Ras can induce secretion of growth factors such as EGF and neuregulin, which activate their respective receptors. In the present study, we demonstrate for the first time that activated Ras can activate ErbB4 receptor in a ligand-independent manner. Expression of constitutively active H-Ras(12V), K-Ras(12V) or N-Ras(13V) in PC12-ErbB4 cells induced ErbB4-receptor phosphorylation, indicating that each of the most abundant Ras isoforms can induce receptor activation. NRG-induced phosphorylation of ErbB4 receptor was blocked by the soluble ErbB4 receptor, which had no effect on the Ras-induced receptor phosphorylation. Moreover, conditioned medium from H-Ras(12V)-transfected PC12-ErbB4 cells had no effect on receptor phosphorylation. It thus indicates that Ras induces ErbB4 phosphorylation in a ligand-independent manner. Each of the Ras effector domain mutants, H-Ras(12V)S35, H-Ras(12V)C40, and H-Ras(12V)G37, which respectively activate Raf1, PI3K, and RalGEF, induced a small but significant receptor phosphorylation. The PI3K inhibitor LY294002 and the MEK inhibitor PD98059 caused a partial inhibition of the Ras-induced ErbB4 receptor phosphorylation. Using a mutant ErbB4 receptor, which lacks kinase activity, we demonstrated that the Ras-mediated ErbB4 phosphorylation depends on the kinase activity of the receptor and facilitates ligand-independent neurite outgrowth in PC12-ErbB4 cells. These experiments demonstrate a novel mechanism controlling ErbB receptor activation. Ras induces ErbB4 receptor phosphorylation in a non-autocrine manner and this activation depends on multiple Ras effector pathways and on ErbB4 kinase activity.     

Entamoeba histolytica: identification and characterization of an N-ethylmaleimide sensitive fusion protein homologue

Entamoeba histolytica is a phagocytic cell with numerous vesicles of different sizes and shapes but without a well-defined Golgi apparatus. Despite this, genes implied in membrane trafficking have been identified in the genome of this parasite. One of these genes is homologous to the N-ethylmaleimide sensitive fusion factor (NSF), whose protein has been shown to play an important role in vesicle fusion in other eukaryotic cells. In this report, we investigated the NSF homologue gene from a pathogenic E. histolytica, characterized its protein product and two of its activities, ATPase and in vitro intra-Golgi transport. The finding of an active NSF protein in E. histolytica indicates that a simple or primordial Golgi apparatus probably exists in this microorganism, as has been proposed by others.     

The Synergistic Effect of Visible Light and Gentamycin on Pseudomona aeruginosa Microorganisms

Recently there were several publications on the bactericidal effect of visible light, most of them claiming that blue part of the spectrum (400 nm-500 nm) is responsible for killing various pathogens^1-5. The phototoxic effect of blue light was suggested to be a result of light-induced reactive oxygen species (ROS) formation by endogenous bacterial photosensitizers which mostly absorb light in the blue region^4,6,7. There are also reports of biocidal effect of red and near infra red⁸ as well as green light⁹.In the present study, we developed a method that allowed us to characterize the effect of high power green (wavelength of 532 nm) continuous (CW) and pulsed Q-switched (Q-S) light on Pseudomonas aeruginosa. Using this method we also studied the effect of green light combined with antibiotic treatment (gentamycin) on the bacteria viability. P. aeruginosa is a common noscomial opportunistic pathogen causing various diseases. The strain is fairly resistant to various antibiotics and contains many predicted AcrB/Mex-type RND multidrug efflux systems¹⁰.The method utilized free-living stationary phase Gram-negative bacteria (P. aeruginosa strain PAO1), grown in Luria Broth (LB) medium exposed to Q-switched and/or CW lasers with and without the addition of the antibiotic gentamycin. Cell viability was determined at different time points. The obtained results showed that laser treatment alone did not reduce cell viability compared to untreated control and that gentamycin treatment alone only resulted in a 0.5 log reduction in the viable count for P. aeruginosa. The combined laser and gentamycin treatment, however, resulted in a synergistic effect and the viability of P. aeruginosa was reduced by 8 log''s.The proposed method can further be implemented via the development of catheter like device capable of injecting an antibiotic solution into the infected organ while simultaneously illuminating the area with light.     

God and the Welfare State - Substitutes or Complements? An Experimental Test of the Effect of Belief in God's Control

Belief in God’s control of the world is common to many of the world’s religions, but there are conflicting predictions regarding its role in shaping attitudes toward the welfare state. While the devout are expected to support pro-social values like helping others, and thus might be supportive of the welfare state, the possibility of taking action is undermined by the belief in God’s absolute control over world affairs and in a morally perfect providence, who is responsible for the fates of individuals. As the literature provides mixed results on this question, this study examines the role of belief in God’s control on welfare attitudes using three priming experiments and two priming tasks, carried out with a design that is both cross-cultural (US vs. Israel) and cross-religious tradition (Judaism vs. Catholicism). We find evidence that, largely, belief in God’s control increases support for income redistribution among Israeli Jews (study 1), American Jews (study 2), and American Catholics (study 3). The findings suggest that the traditional and common political gap between the economic left and the religious, based on the evaluation that religious beliefs lead to conservative economic preferences, may be overstated.     

Reliability of an individually molded shank shell for measuring tibial transverse rotations during the stance phase of walking

Use of a shank shell has been shown to estimate tibial transverse rotations better than skin-mounted markers. However, the day-to-day reliability of the transverse tibial rotations using an individually molded shank shell has not been previously investigated. This study examined the between-tests and trials reliability of an individually molded shank shell for measuring peak tibial internal and external rotations, time of peak values, and tibia range of motion during 5 walking trials. The trial-to-trial reliability of tibial transverse rotations was measured in 14 healthy individuals while the test-retest reliability was measured in 10 persons on two occasions. Trial-to-trial reliability for peak transverse rotations, time of peak values, and tibia range of motion ranged from ICC (3,1) 0.59-0.95. The PCA between trials showed that 88-99 % of values were within 3 degrees of agreement. Test-retest reliability for peak rotations, tibia range of motion, and time of peak values ranged from ICC (3,1) 0.70-0.89 with SEM 1.6-2.21 degrees , 0.021 %, and 0.034 %, respectively. The PCA between tests showed that 70-100 % of values were within 3 degrees of agreement. The use of an individually molded shell and the close attachment of the shank shell to the individual's shank resulted in reliable test-retest and trial-to-trial data.     

mTORC2 Caught in a SINful Akt

The target of rapamycin (TOR), a central controller of cell growth, is found in two distinct, highly conserved multiprotein complexes. Three recent papers in Cell (Jacinto et al., 2006), Developmental Cell (shiota et al., 2006; this issue), and Current Biology (Frias et al., 2006) shed light on mTOR complex 2 (mTORC2) composition and in vivo function. An important new finding is that mTORC2 determines Akt/PKB substrate specificity rather than absolute activity.