SCAMP5 Links Endoplasmic Reticulum Stress to the Accumulation of Expanded Polyglutamine Protein Aggregates via Endocytosis Inhibition

Accumulation of expanded polyglutamine proteins is considered to be a major pathogenic biomarker of Huntington disease. We isolated SCAMP5 as a novel regulator of cellular accumulation of expanded polyglutamine track protein using cell-based aggregation assays. Ectopic expression of SCAMP5 augments the formation of ubiquitin-positive and detergent-resistant aggregates of mutant huntingtin (mtHTT). Expression of SCAMP5 is markedly increased in the striatum of Huntington disease patients and is induced in cultured striatal neurons by endoplasmic reticulum (ER) stress or by mtHTT. The increase of SCAMP5 impairs endocytosis, which in turn enhances mtHTT aggregation. On the contrary, down-regulation of SCAMP5 alleviates ER stress-induced mtHTT aggregation and endocytosis inhibition. Moreover, stereotactic injection into the striatum and intraperitoneal injection of tunicamycin significantly increase mtHTT aggregation in the striatum of R6/2 mice and in the cortex of N171-82Q mice, respectively. Taken together, these results suggest that exposure to ER stress increases SCAMP5 in the striatum, which positively regulates mtHTT aggregation via the endocytosis pathway.The expansion of CAG repeats (usually beyond a critical threshold of ∼37 glutamine repeats) encoding polyglutamine (polyQ)³ causes, to date, nine late-onset progressive neurodegenerative disorders (1, 2). Expanded polyQ-containing huntingtin is the main aggregate component in the affected neurons (3). Also, molecular chaperones, such as Hsp70, Hsp40/HDJ1 (dHDJ1), and chaperonin TRiC, perturb the aggregation of polyQ track protein and reduce polyQ track cytotoxicity in yeast and cell lines (4–6) and in Drosophila and mouse models (4, 7). Thus, it seems that HD pathology is closely correlated with the accumulation of insoluble aggregates of mutant huntingtin (mtHTT) containing expanded polyQ (2, 3, 8, 9).Endoplasmic reticulum (ER) stress is crucial in many biological responses and is generated by various signals, such as unfolded protein response, aberrant calcium regulation, oxidative stress, and inflammation (10, 11). ER stress response is generally considered an adaptive reaction of cells to environmental stress, serving as a survival signal (10). On the other hand, increasing evidence also strengthens the importance of ER stress in human diseases. A malfunction or excess of ER stress response caused by aging, genetic mutations, and environmental insults is implicated in human diseases, such as Alzheimer disease, Parkinson disease, diabetes mellitus, and inflammation (12–16). mtHTT also induces ER stress at the early stage of HD, and pathogenic ER stress from an aging or stressful environment is severe at the late stage of HD (17–19). However, the molecular event linking the aggregation of polyQ track protein to ER stress response is unknown.The ubiquitin/proteasome pathway, a major protein degradation system, is altered or impaired in the cell culture model of HD (20–22). On the contrary, autophagy employing lysosomal degradation has been recently considered as a major clearance pathway of insoluble aggregates of polyQ track protein. Thus, inhibition of autophagy has been suggested to modulate the aggregate formation of mtHTT and to affect the toxicity of polyglutamine expansions in fly and mouse models of HD (23–25). However, a key molecule controlling the aggregation and clearance of polyQ track proteins needs to be identified.To further our understanding of the regulation of polyQ track protein aggregation, we screened human full-length cDNAs and isolated SCAMP5 (secretory carrier membrane protein 5) as a modulator of polyQ track protein aggregation. SCAMP5 is up-regulated by mtHTT and ER stress and functions to inhibit endocytosis to increase mtHTT aggregation.     

Antioxidative role of selenoprotein W in oxidant-induced mouse embryonic neuronal cell death

It has been reported that selenoprotein W (SelW) mRNA is highly expressed in the developing central nerve system of rats, and its expression is maintained until the early postnatal stage. We here found that SelW protein significantly increased in mouse brains of postnatal day 8 and 20 relative to embryonic day 15. This was accompanied by increased expression of SOD1 and SOD2. When the expression of SelW in primary cultured cells derived from embryonic cerebral cortex was knocked down with small interfering RNAs (siRNAs), SelW siRNA-transfected neuronal cells were more sensitive to the oxidative stress induced by treatment of H₂O₂ than control cells. TUNEL assays revealed that H₂O₂-induced apoptotic cell death occurred at a higher frequency in the siRNA-transfected cells than in the control cells. Taken together, our findings suggest that SelW plays an important role in protection of neurons from oxidative stress during neuronal development.     

Oncostatin M induces dendritic cell maturation and Th1 polarization

Oncostatin M (OSM) is a pleiotropic cytokine and a member of the gp130/IL-6 cytokine family that has been found to be involved in both pro- and anti-inflammatory responses in cell-mediated immunity. Maturation of dendritic cells (DCs) is crucial for initiation of primary immune responses and is regulated by several stimuli. In this study, the role of OSM in the phenotypic and functional maturation of DCs was evaluated in vitro. Stimulation with OSM upregulated the expression of CD80, CD86, MHC class I and MHC class II and reduced the endocytic capacity of immature DCs. Moreover, OSM induced the allogeneic immunostimulatory capacity of DCs by stimulating the production of the Th1-promoting cytokine IL-12. OSM also increased the production of IFN-γ by T cells in mixed-lymphocyte reactions, which would be expected to contribute to the Th1 polarization of the immune response. The expression of surface markers and cytokine production in DCs was mediated by both the MAPK and NF-κB pathways. Taken together, these results indicate that OSM may play a role in innate immunity and in acquired immunity by enhancing DCs maturation and promoting Th1 immune responses.     

Synthesis and PGE2 production inhibition of 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione derivatives

3,4-Diphenyl-substituted 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione derivatives were synthesized and evaluated for the inhibitory activities on LPS-induced PGE₂ production in RAW 264.7 macrophage cells. Both 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione rings as main scaffolds were easily obtained using one of three synthetic methods. Among the compounds investigated, 1H-3-(4-sulfamoylphenyl)-4-phenyl-pyrrole-2,5-dione (6l) showed a strong inhibitory activity (IC₅₀ = 0.61 μM) of PGE₂ production.     

Enhanced cell permeability of kojic acid–phenylalanine amide with metal complex

Kojic acid–phenylalanine amide (KA–F–NH₂), which showed an excellent tyrosinase inhibitory activity, did not inhibit melanogenesis in melanocyte due to its low cell permeability. To enhance its cell permeability by increasing lipophilicity, we prepared metal coordination compounds of KA–F–NH₂ and characterized them by FT-IR and ICP analysis. The metal complex of KA–F–NH₂ inhibited mushroom tyrosinase activity as much as KA–F–NH₂ and reduced melanin contents in melanocyte efficiently.     

Propofol protects the autophagic cell death induced by the ischemia/reperfusion injury in rats

Autophagy has been implicated in cardiac cell death during ischemia/reperfusion (I/R). In this study we investigated how propofol, an antioxidant widely used for anesthesia, affects the autophagic cell death induced by the myocardial I/R injury. The infarction size in the myocardium was dramatically reduced in rats treated with propofol during I/R compared with untreated rats. A large number of autophagic vacuoles were observed in the cardiomyocytes of I/R-injured rats but rarely in I/R-injured rats treated with propofol. While LC3-II formation, an autophagy marker, was up-regulated in the I/R-injured myocardium, it was significantly down-regulated in the myocardial tissues of I/R-injured and propofol-treated rats. Moreover, propofol inhibited the I/R-induced expression of Beclin-1, and it accelerated phosphorylation of mTOR during I/R and Beclin-1/Bcl-2 interaction in cells, which indicates that it facilitates the inhibitory pathway of autophagy. These data suggest that propofol protects the autophagic cell death induced by the myocardial I/R injury.