Sensitivity to MPTP is not increased in Parkinson's disease-associated mutant alpha-synuclein transgenic mice

Environmental and genetic factors that contribute to the pathogenesis of Parkinson's disease are discussed. Mutations in the alpha-synuclein (alphaSYN ) gene are associated with rare cases of autosomal-dominant Parkinson's disease. We have analysed the dopaminergic system in transgenic mouse lines that expressed mutant [A30P]alphaSYN under the control of a neurone-specific Thy-1 or a tyrosine hydroxylase (TH) promoter. The latter mice showed somal and neuritic accumulation of transgenic [A30P]alphaSYN in TH-positive neurones in the substantia nigra. However, there was no difference in the number of TH-positive neurones in the substantia nigra and the concentrations of catecholamines in the striatum between these transgenic mice and non-transgenic littermates. To investigate whether forced expression of [A30P]alphaSYN increased the sensitivity to putative environmental factors we subjected transgenic mice to a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) regimen. The MPTP-induced decrease in the number of TH-positive neurones in the substantia nigra and the concentrations of catecholamines in the striatum did not differ in any of the [A30P]alphaSYN transgenic mouse lines compared with wild-type controls. These results suggest that mutations and forced expression of alphaSYN are not likely to increase the susceptibility to environmental toxins in vivo.     

ERK8, a new member of the mitogen-activated protein kinase family

The ERKs are a subfamily of the MAPKs that have been implicated in cell growth and differentiation. By using the rat ERK7 cDNA to screen a human multiple tissue cDNA library, we identified a new member of the ERK family, ERK8, that shares 69% amino acid sequence identity with ERK7. Northern analysis demonstrates that ERK8 is present in a number of tissues with maximal expression in the lung and kidney. Fluorescence in situ hybridization localized the ERK8 gene to chromosome 8, band q24.3. Expression of ERK8 in COS cells and bacteria indicates that, in contrast to constitutively active ERK7, ERK8 has minimal basal kinase activity and a unique substrate profile. ERK8, which contains two SH3-binding motifs in its C-terminal region, associates with the c-Src SH3 domain in vitro and co-immunoprecipitates with c-Src in vivo. Co-transfection with either v-Src or a constitutively active c-Src increases ERK8 activation indicating that ERK8 can be activated downstream of c-Src. ERK8 is also activated following serum stimulation, and the extent of this activation is reduced by pretreatment with the specific Src family inhibitor PP2. The ERK8 activation by serum or Src was not affected by the MEK inhibitor U0126 indicating that activation of ERK8 does not require MEK1, MEK2, or MEK5. Although most closely related to ERK7, the relatively low sequence identity, minimal basal activity, and different substrate profile identify ERK8 as a distinct member of the MAPK family that is activated by an Src-dependent signaling pathway.     

Prognostic value of flow cytometrically determined DNA-ploidy, intracellular pH and esterase activity of non-small cell lung carcinomas.

30 surgical specimens of patients with non-small cell lung carcinomas (NSCLC) were investigated. Significant increases of intracellular pH values in epithelial and inflammatory cells, in the percentage of dead epithelial and inflammatory cells and in the cell volume of vital inflammatory cells in cancerous lung tissue were encountered. Furthermore, decreases of the esterase activity of vital epithelial cells and of the percentage of free cell nuclei were observed. The DNA aneuploidy in 36.6% of the tumours was frequently associated with non-squamous cell carcinomas and stage II, III, IV tumours. Patients with DNA aneuploid tumours had a significantly shorter survival rate than those with DNA euploid tumours. Within the different tumour stages a similar tendency was observed which was, however, only significant in stage III tumour patients. Stage III tumours constitute therefore a heterogeneous entity with a worse prognosis for DNA aneuploid tumour patients. The intracellular pH values and esterase activity as well as the cell volume, the percentage of free cell nuclei and dead inflammatory or epithelial cells contained no significant prognostic information.     

Regenerative potential of human muscle stem cells in chronic inflammation

Introduction

Chronic inflammation is a profound systemic modification of the cellular microenvironment which could affect survival, repair and maintenance of muscle stem cells. The aim of this study was to define the role of chronic inflammation on the regenerative potential of satellite cells in human muscle.

Methods

As a model for chronic inflammation, 11 patients suffering from rheumatoid arthritis (RA) were included together with 16 patients with osteoarthritis (OA) as controls. The mean age of both groups was 64 years, with more females in the RA group compared to the OA group. During elective knee replacement surgery, a muscle biopsy was taken from the distal musculus vastus medialis. Cell populations from four RA and eight OA patients were used for extensive phenotyping because these cell populations showed no spontaneous differentiation and myogenic purity greater than 75% after explantation.

Results

After mononuclear cell explantation, myogenic purity, viability, proliferation index, number of colonies, myogenic colonies, growth speed, maximum number of population doublings and fusion index were not different between RA and OA patients. Furthermore, the expression of proteins involved in replicative and stress-induced premature senescence and apoptosis, including p16, p21, p53, hTERT and cleaved caspase-3, was not different between RA and OA patients. Mean telomere length was shorter in the RA group compared to the OA group.

Conclusions

In the present study we found evidence that chronic inflammation in RA does not affect the in vitro regenerative potential of human satellite cells. Identification of mechanisms influencing muscle regeneration by modulation of its microenvironment may, therefore, be more appropriate.     

Monoclonal antibodies selective for α‐synuclein oligomers/protofibrils recognize brain pathology in Lewy body disorders and α‐synuclein transgenic mice with the disease‐causing A30P mutation

Inclusions of intraneuronal alpha‐synuclein (α‐synuclein) can be detected in brains of patients with Parkinson's disease and dementia with Lewy bodies. The aggregation of α‐synuclein is a central feature of the disease pathogenesis. Among the different α‐synuclein species, large oligomers/protofibrils have particular neurotoxic properties and should therefore be suitable as both therapeutic and diagnostic targets. Two monoclonal antibodies, mAb38F and mAb38E2, with high affinity and strong selectivity for large α‐synuclein oligomers were generated. These antibodies, which do not bind amyloid‐beta or tau, recognize Lewy body pathology in brains from patients with Parkinson's disease and dementia with Lewy bodies and detect pathology earlier in α‐synuclein transgenic mice than linear epitope antibodies. An oligomer‐selective sandwich ELISA, based on mAb38F, was set up to analyze brain extracts of the transgenic mice. The overall levels of α‐synuclein oligomers/protofibrils were found to increase with age in these mice, although the levels displayed a large interindividual variation. Upon subcellular fractionation, higher levels of α‐synuclein oligomers/protofibrils could be detected in the endoplasmic reticulum around the age when behavioral disturbances develop. In summary, our novel oligomer‐selective α‐synuclein antibodies recognize relevant pathology and should be important tools to further explore the pathogenic mechanisms in Lewy body disorders. Moreover, they could be potential candidates both for immunotherapy and as reagents in an assay to assess a potential disease biomarker.     

Development of Methods for Cross-Sectional HIV Incidence Estimation in a Large,Community Randomized Trial

Background

Accurate methods of HIV incidence determination are critically needed to monitor the epidemic and determine the population level impact of prevention trials. One such trial, Project Accept, a Phase III, community-randomized trial, evaluated the impact of enhanced, community-based voluntary counseling and testing on population-level HIV incidence. The primary endpoint of the trial was based on a single, cross-sectional, post-intervention HIV incidence assessment.

Methods and Findings

Test performance of HIV incidence determination was evaluated for 403 multi-assay algorithms [MAAs] that included the BED capture immunoassay [BED-CEIA] alone, an avidity assay alone, and combinations of these assays at different cutoff values with and without CD4 and viral load testing on samples from seven African cohorts (5,325 samples from 3,436 individuals with known duration of HIV infection [1 month to >10 years]). The mean window period (average time individuals appear positive for a given algorithm) and performance in estimating an incidence estimate (in terms of bias and variance) of these MAAs were evaluated in three simulated epidemic scenarios (stable, emerging and waning). The power of different test methods to detect a 35% reduction in incidence in the matched communities of Project Accept was also assessed. A MAA was identified that included BED-CEIA, the avidity assay, CD4 cell count, and viral load that had a window period of 259 days, accurately estimated HIV incidence in all three epidemic settings and provided sufficient power to detect an intervention effect in Project Accept.

Conclusions

In a Southern African setting, HIV incidence estimates and intervention effects can be accurately estimated from cross-sectional surveys using a MAA. The improved accuracy in cross-sectional incidence testing that a MAA provides is a powerful tool for HIV surveillance and program evaluation.     

WNK2 kinase is a novel regulator of essential neuronal cation-chloride cotransporters

NKCC1 and KCC2, related cation-chloride cotransporters (CCC), regulate cell volume and γ-aminobutyric acid (GABA)-ergic neurotranmission by modulating the intracellular concentration of chloride [Cl(-)]. These CCCs are oppositely regulated by serine-threonine phosphorylation, which activates NKCC1 but inhibits KCC2. The kinase(s) that performs this function in the nervous system are not known with certainty. WNK1 and WNK4, members of the WNK (with no lysine [K]) kinase family, either directly or via the downstream SPAK/OSR1 Ste20-type kinases, regulate the furosemide-sensitive NKCC2 and the thiazide-sensitive NCC, kidney-specific CCCs. What role the novel WNK2 kinase plays in this regulatory cascade, if any, is unknown. Here, we show that WNK2, unlike other WNKs, is not expressed in kidney; rather, it is a neuron-enriched kinase primarily expressed in neocortical pyramidal cells, thalamic relay cells, and cerebellar granule and Purkinje cells in both the developing and adult brain. Bumetanide-sensitive and Cl(-)-dependent (86)Rb(+) uptake assays in Xenopus laevis oocytes revealed that WNK2 promotes Cl(-) accumulation by reciprocally activating NKCC1 and inhibiting KCC2 in a kinase-dependent manner, effectively bypassing normal tonicity requirements for cotransporter regulation. TiO(2) enrichment and tandem mass spectrometry studies demonstrate WNK2 forms a protein complex in the mammalian brain with SPAK, a known phosphoregulator of NKCC1. In this complex, SPAK is phosphorylated at Ser-383, a consensus WNK recognition site. These findings suggest a role for WNK2 in the regulation of CCCs in the mammalian brain, with implications for both cell volume regulation and/or GABAergic signaling.     

UBE2E Ubiquitin-conjugating Enzymes and Ubiquitin Isopeptidase Y Regulate TDP-43 Protein Ubiquitination

Trans-activation element DNA-binding protein of 43 kDa (TDP-43) characterizes insoluble protein aggregates in distinct subtypes of frontotemporal lobar degeneration and amyotrophic lateral sclerosis. TDP-43 mediates many RNA processing steps within distinct protein complexes. Here we identify novel TDP-43 protein interactors found in a yeast two-hybrid screen using an adult human brain cDNA library. We confirmed the TDP-43 interaction of seven hits by co-immunoprecipitation and assessed their co-localization in HEK293E cells. As pathological TDP-43 is ubiquitinated, we focused on the ubiquitin-conjugating enzyme UBE2E3 and the ubiquitin isopeptidase Y (UBPY). When cells were treated with proteasome inhibitor, ubiquitinated and insoluble TDP-43 species accumulated. All three UBE2E family members could enhance the ubiquitination of TDP-43, whereas catalytically inactive UBE2E3^C145S was much less efficient. Conversely, silencing of UBE2E3 reduced TDP-43 ubiquitination. We examined 15 of the 48 known disease-associated TDP-43 mutants and found that one was excessively ubiquitinated. This strong TDP-43^K263E ubiquitination was further enhanced by proteasomal inhibition as well as UBE2E3 expression. Conversely, UBE2E3 silencing and expression of UBPY reduced TDP-43^K263E ubiquitination. Moreover, wild-type but not active site mutant UBPY reduced ubiquitination of TDP-43 C-terminal fragments and of a nuclear import-impaired mutant. In Drosophila melanogaster, UBPY silencing enhanced neurodegenerative TDP-43 phenotypes and the accumulation of insoluble high molecular weight TDP-43 and ubiquitin species. Thus, UBE2E3 and UBPY participate in the regulation of TDP-43 ubiquitination, solubility, and neurodegeneration.