No abstract

Modification by O-GlcNAc involves a growing number of eucaryotic nuclear and cytosolic proteins. Glycosylation of intracellular proteins is a dynamic process that in several cases competes with and acts as a reciprocal modification system to phosphorylation. O-Linked ␤-N-acetylglucosamine transferase (OGT) levels are highest in the brain, and neurodegenerative disorders such as Alzheimer disease have been shown to involve abnormally phosphorylated key proteins, probably as a result of hypoglycosylation. Here, we show that the neurodegenerative disease protein ataxin-10 (Atx-10) is associated with cytoplasmic OGT p110 in the brain. In PC12 cells and pancreas, this association is competed by the shorter OGT p78 splice form, which is down-regulated in brain. Overexpression of Atx-10 in PC12 cells resulted in the reconstitution of the Atx-10-OGT p110 complex and enhanced intracellular glycosylation activity. Moreover, in an in vitro enzyme assay using PC12 cell extracts, Atx-10 increased OGT activity 2-fold. These data indicate that Atx-10 might be essential for the maintenance of a critical intracellular glycosylation level and homeostasis in the brain.Since its discovery (1), the modification of intracellular proteins by a single GlcNAc moiety has emerged as a major signaling event involving a growing number of proteins (2, 3). Changes in O-GlcNAc glycosylation levels were shown to have a regulatory effect on diverse cellular processes such as proteasome activity (4), transcription (5), and enzyme function (6). The enzyme OGT 2 is encoded by a single gene, which is highly conserved among metazoans (7). Several splice forms have been described that vary in the length of the protein N terminus and subcellular localization (8). Full-length OGT is a 110-kDa polypeptide consisting of two domains. The N-terminal half contains multiple tetratricopeptide repeats (TPR) that adopt a bent superhelical fold related to the armadillo repeat motif (9). The C-terminal portion shows glycosyltransferase activity, whereas the TPR domain is responsible for substrate binding and OGT oligomerization (9 -11). Originally, the enzyme was isolated from rat liver cytosol as an apparent heterotrimer consisting of two p110 subunits and one p78 subunit (12). The p110 subunit, which exerts full catalytic activity by itself, is ubiquitously expressed, whereas the p78 splice variant that lacks most of the TPR repeats appears to be restricted to certain tissues such as liver, kidney, and muscle (13).Dysregulated OGT activity leading to hyper-or hypoglycosylation of target proteins is believed to be involved in the pathogenesis of disorders such as type II diabetes (6, 14) and Alzheimer disease (15). Protein glycosylation with GlcNAc may directly compete for serine and threonine residues with phosphorylation, thus creating a sensitive balance between positive and negative regulatory signals (16). Perturbations of this reciprocal relationship might lead to cell degeneration as in the case of hyperphosphorylated tau (17,18). It has become evident fro...

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article.

No abstract

The interaction of neurotrophins and their tyrosine kinase receptors (trks) is essential for differentiation and survival of brain cells. In Alzheimer's disease (AD), the number of neurotrophins and receptors is markedly decreased. The cause of this reduction is unclear, but the role of beta-amyloid (Abeta) seems central in understanding the mechanisms controlling neurotrophin and trk expression. In the study reported here, we exposed SHSY5Y neuroblastoma cells to Abeta or hydrogen peroxide (H(2)O(2)) and measured the expression of trk-A and p75 at the protein and molecular levels. Both Abeta and H(2)O(2) induced oxidative stress (measured by a decrease in cellular glutathione), which decreased trk-A levels and increased p75 levels, decreased messenger RNA (mRNA) levels of both receptors, and increased nerve growth factor (NGF) secretion. Pretreatment of cells with the antioxidant melatonin returned levels of protein expression, mRNA, and NGF secretion to normal. These results are significant, as they can help in the planning and implementation of AD treatment strategies involving neurotrophins.

Background: The major goal of the study was to compare the genetic programs utilized by the neuropoietic cytokine Interleukin-6 (IL-6) and the neurotrophin (NT) Nerve Growth Factor (NGF) for neuronal differentiation.

Neuronal cell death after severe traumatic brain injury (TBI) is caused by a complex interplay of pathological mechanisms including excitotoxicity, oxidative stress, mitochondrial dysfunction, extensive neuroinflammation, and ischemia-reperfusion injury. Pancreatitis-associated protein I (PAP I/reg2) was reported to be a survival factor for peripheral neurons, particularly sensory and motor neurons. In rat brains, by experimental TBI as well as by kainic acid induced brain seizure, PAP I and PAP III were found to be up-regulated in central neurons. In this study, we performed immunohistochemical staining in postmortem human brain from patients who died after severe TBI to demonstrate PAP expression on protein level in cerebellar Purkinje cells, pyramidal and granular neurons in cerebral cortex, and cortical neurons in the fore-and mid-brain. In primary cultures of rat brain cortical, hippocampal, and cerebellar neurons, we found neuroprotective effects for PAP I on H 2 O 2 -induced oxidative stress. Moreover, serum K ? -deprivation induces apoptotic cell death in 55% of cerebellar granule neurons (CGN), whereas upon treatment with PAP I only 32% of CGN are apoptotic. Using Western blot analyses, we compared protein phosphorylation in neuronal signaling pathways activated by PAP I versus Interleukin-6 (IL-6). We found a rapid activation of Akt-kinase phosphorylation by PAP I with a peak at 15 min, whereas IL-6 induces Akt-phosphorylation lasting longer than 30 min. Phosphorylation of MAP-42/44 kinases is stimulated in a comparable fashion. Both, IL-6 and PAP I increase phosphorylation of NFjB for activation of gene transcription, whereas only IL-6 recruits STAT3 phosphorylation, indicating that STAT3 is not a target of PAP I transcription activation in brain neurons. Application of the Akt-inhibitor Wortmanin reveals only a partial inhibition of PAP I-dependent protection of CGN from H 2 O 2 -induced oxidative stress. Based on our findings, we suggest that PAP I is a long lasting neurotrophic signal for central neurons. The neuroprotective effects parallel those that have been Pia März-Weiss and Dieter Kunz contributed equally in this study.Electronic supplementary material The online version of this article

No abstract