Neurotoxic Microglial Activation via IFNγ-Induced Nrf2 Reduction Exacerbating Alzheimer's Disease.

Microglial neuroinflammation appears to be neuroprotective in the early pathological stage, yet neurotoxic, which often precedes neurodegeneration in Alzheimer's disease (AD). However, it remains unclear how the microglial activities transit to the neurotoxic state during AD progression, due to complex neuron-glia interactions. Here, the mechanism of detrimental microgliosis in AD by employing 3D human AD mini-brains, brain tissues of AD patients, and 5XFAD mice is explored. In the human and animal AD models, amyloid-beta (Aß)-overexpressing neurons and reactive astrocytes produce interferon-gamma (IFNγ) and excessive oxidative stress. IFNγ results in the downregulation of mitogen-activated protein kinase (MAPK) and the upregulation of Kelch-like ECH-associated Protein 1 (Keap1) in microglia, which inactivate nuclear factor erythroid-2-related factor 2 (Nrf2) and sensitize microglia to the oxidative stress and induces a proinflammatory microglia via nuclear factor kappa B (NFκB)-axis. The proinflammatory microglia in turn produce neurotoxic nitric oxide and proinflammatory mediators exacerbating synaptic impairment, phosphorylated-tau accumulation, and discernable neuronal loss. Interestingly, recovering Nrf2 in the microglia prevents the activation of proinflammatory microglia and significantly blocks the tauopathy in AD minibrains. Taken together, it is envisioned that IFNγ-driven Nrf2 downregulation in microglia as a key target to ameliorate AD pathology.

Protein L-isoaspartyl methyltransferase regulates p53 activity.

Protein methylation plays important roles in most, if not all, cellular processes. Lysine and arginine methyltransferases are known to regulate the function of histones and non-histone proteins through the methylation of specific sites. However, the role of the carboxyl-methyltransferase protein L-isoaspartyl methyltransferase (PIMT) in the regulation of protein functions is relatively less understood. Here we show that PIMT negatively regulates the tumour suppressor protein p53 by reducing p53 protein levels, thereby suppressing the p53-mediated transcription of target genes. In addition, PIMT depletion upregulates the proapoptotic and checkpoint activation functions of p53. Moreover, PIMT destabilizes p53 by enhancing the p53-HDM2 interaction. These PIMT effects on p53 stability and activity are attributed to the PIMT-mediated methylation of p53 at isoaspartate residues 29 and 30. Our study provides new insight into the molecular mechanisms by which PIMT suppresses the p53 activity through carboxyl methylation, and suggests a therapeutic target for cancers.

Pedobacter oryzae sp. nov., isolated from rice paddy soil.

A Gram-stain-negative, strictly aerobic bacterium, designated strain N7(T), was isolated from a rice paddy in South Korea. Cells of strain N7(T) were non-motile, non-spore-forming rods. Growth was observed at 15-35 degrees C (optimum of 25-30 degrees C) and between pH 6.0 and 8.0 (optimum of pH 6.5-7.5). The predominant isoprenoid quinone was menaquinone-7. The major cellular fatty acids of strain N7(T) were summed feature 3 (comprising C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH), iso-C(15 : 0), anteiso-C(15 : 0), C(15 : 0) and iso-C(16 : 0). The G+C content of the genomic DNA was 37.7 mol%. Comparative 16S rRNA gene sequence analyses showed that strain N7(T) formed a distinct phyletic line within the genus Pedobacter. Phylogenetic distances from strains of other Pedobacter species with validly published names were greater than 5.0 % (i.e. <95.0 % 16S rRNA gene sequence similarities). On the basis of phenotypic and molecular data, it is clear that strain N7(T) represents a novel species within the genus Pedobacter, for which the name Pedobacter oryzae sp. nov. is proposed. The type strain is N7(T) (=KACC 12821(T) =DSM 19973(T)).

Mucilaginibacter oryzae sp. nov., isolated from soil of a rice paddy.

A Gram-negative-staining, non-spore-forming bacterium devoid of flagella, designated strain B9(T), was isolated from rice paddy soil associated with the roots of Oryza sativa collected from Jinju, South Korea. Cells were straight rods, were catalase- and oxidase-positive and were able to hydrolyse pectin, xylan and laminarin. Growth of strain B9(T) was observed between 15 and 35 degrees C (optimum 25-30 degrees C) and between pH 5.0 and 8.0 (optimum pH 6.5-7.5). Strain B9(T) contained menaquinone-7 (MK-7) as a major isoprenoid quinone and summed feature 3 (C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH), iso-C(15 : 0) and C(16 : 0) as major fatty acids. The G+C content of the genomic DNA was 44.4 mol%. Comparative 16S rRNA gene sequence analysis showed that strain B9(T) belonged to the genus Mucilaginibacter, a member of the family Sphingobacteriaceae, and was most closely related to Mucilaginibacter kameinonensis SCK(T) (95.9 % sequence similarity). On the basis of chemotaxonomic data and molecular properties, strain B9(T) represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter oryzae sp. nov. is proposed. The type strain is B9(T) (=KACC 12816(T) =DSM 19975(T)).

Flavobacterium filum sp. nov., isolated from a wastewater treatment plant in Korea.

A Gram-negative bacterium, designated strain EMB34(T), was isolated from a wastewater treatment plant in Korea. Growth was observed between 10 and 40 degrees C (optimum, 25-35 degrees C) and between pH 6.0 and 9.5 (optimum, pH 7.5-8.0). The cells were non-motile rods, linked with extracellular fibrils. The predominant fatty acids of strain EMB34(T) were iso-C(15 : 0), C(15 : 0), iso-C(15 : 1) G, iso-C(16 : 0) 3-OH and iso-C(15 : 0) 3-OH and the strain contained phosphatidylethanolamine and phosphatidylinositol as the polar lipids. The G+C content of the genomic DNA was 34.2 mol% and the major quinone was menaquinone-6. Comparative 16S rRNA gene sequence analyses showed that strain EMB34(T) formed a distinct phyletic line within the genus Flavobacterium. The levels of 16S rRNA gene sequence similarity with other Flavobacterium species were less than 94.5 %. On the basis of phenotypic, chemotaxonomic and molecular data, it is clear that strain EMB34(T) represents a novel species within the genus Flavobacterium, for which the name Flavobacterium filum sp. nov. is proposed. The type strain is EMB34(T) (=KCTC 12610(T)=DSM 17961(T)).

Molecular and biochemical characterization of 3-hydroxybenzoate 6-hydroxylase from Polaromonas naphthalenivorans CJ2.

Prior research revealed that Polaromonas naphthalenivorans CJ2 carries and expresses genes encoding the gentisate metabolic pathway for naphthalene. These metabolic genes are split into two clusters, comprising nagRAaGHAbAcAdBFCQEDJI'-orf1-tnpA and nagR2-orf2I''KL (C. O. Jeon, M. Park, H. Ro, W. Park, and E. L. Madsen, Appl. Environ. Microbiol. 72:1086-1095, 2006). BLAST homology searches of sequences in GenBank indicated that the orf2 gene from the small cluster likely encoded a salicylate 5-hydroxylase, presumed to catalyze the conversion of salicylate into gentisate. Here, we report physiological and genetic evidence that orf2 does not encode salicylate 5-hydroxylase. Instead, we have found that orf2 encodes 3-hydroxybenzoate 6-hydroxylase, the enzyme which catalyzes the NADH-dependent conversion of 3-hydroxybenzoate into gentisate. Accordingly, we have renamed orf2 nagX. After expression in Escherichia coli, the NagX enzyme had an approximate molecular mass of 43 kDa, as estimated by gel filtration, and was probably a monomeric protein. The enzyme was able to convert 3-hydroxybenzoate into gentisate without salicylate 5-hydroxylase activity. Like other 3-hydroxybenzoate 6-hydroxylases, NagX utilized both NADH and NADPH as electron donors and exhibited a yellowish color, indicative of a bound flavin adenine dinucleotide. An engineered mutant of P. naphthalenivorans CJ2 defective in nagX failed to grow on 3-hydroxybenzoate but grew normally on naphthalene. These results indicate that the previously described small catabolic cluster in strain CJ2 may be multifunctional and is essential for the degradation of 3-hydroxybenzoate. Because nagX and an adjacent MarR-type regulatory gene are both closely related to homologues in Azoarcus species, this study raises questions about horizontal gene transfer events that contribute to operon evolution.

Hydrogenophaga caeni sp. nov., isolated from activated sludge.

A Gram-negative bacterium, designated strain EMB71(T), was isolated from activated sludge used for enhanced biological phosphorus removal in a sequencing batch reactor. The cells of the isolate were facultatively aerobic, motile rods with single polar flagella. Growth was observed to occur at 15-35 degrees C (optimally at 30 degrees C) and at pH 6.0-9.0 (optimally at pH 7.0-8.0). The predominant fatty acids of strain EMB71(T) were C(16 : 0) and summed feature 3 (C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH), and the polar lipids comprised a large amount of phosphatidylethanolamine and a small amount of diphosphatidylglycerol. The G+C content of the genomic DNA was 61.6 mol % and the major quinone was Q-8. Comparative 16S rRNA gene sequence analyses showed that strain EMB71(T) formed a phyletic lineage with the genus Hydrogenophaga within the family Comamonadaceae. The levels of 16S rRNA gene sequence similarity with respect to the type strains of Hydrogenophaga species ranged from 95.1 to 96.9 %. On the basis of the phenotypic, chemotaxonomic and molecular data, strain EMB71(T) represents a novel species of the genus Hydrogenophaga, for which the name Hydrogenophaga caeni sp. nov. is proposed. The type strain is EMB71(T) (=KCTC 12613(T)=DSM 17962(T)).