ABSTRACT
Phycobilisomes (PBSs) are light-harvesting antenna complexes in cyanobacteria that adapt to diverse light environments through the use of phycobiliproteins within the PBS structures. Freshwater cyanobacteria, such as Synechococcus elongatus PCC 7942, thrive under red light because of the presence of phycocyanin (PC) and its chromophore, phycocyanobilin (PCB), in the PBS. Cyanobacteria in shorter-wavelength light environments such as green light, employ phycoerythrin paired with phycoerythrobilin (PEB) along with PC in the PBS. Synthetic biology studies have shown that PEB production can be achieved by expression of the heterologous PEB synthases 15,16-dihydrobiliverdin:ferredoxin oxidoreductase (PebA) and PEB:ferredoxin oxidoreductase (PebB), leading to PEB accumulation and cellular browning. This approach is genetically unstable, and the properties of the resulting PEB-bound PBS complexes remain uncharacterized. In this study, we engineered a novel strain of Synechococcus 7942 PEB1 with finely tuned control of PEB biosynthesis. PEB1 exhibited a reversible change in the color of the culture from green to brown and pink based on PebA and PebB induction levels. High induction led to complete PCB-to-PEB substitution, causing the disassembly of the PBS rod complex. In contrast, low induction levels of PebA and PebB resulted in the formation of a stable chimeric PBS complex with partial PCB-to-PEB substitution. This acclimation enabled efficient light harvesting in the green spectrum and energy transfer to the photosynthetic reaction center. These findings, which improve our understanding of PBS and highlight the structural importance of the bilin composition, provide a foundation for future studies on PBS adaptation in bioengineering, synthetic biology, and renewable energy.
Subject(s)
Bacterial Proteins , Phycobiliproteins , Phycobilisomes , Phycocyanin , Synechococcus , Synechococcus/metabolism , Synechococcus/genetics , Phycobilisomes/metabolism , Phycobiliproteins/metabolism , Phycobiliproteins/genetics , Bacterial Proteins/metabolism , Bacterial Proteins/genetics , Phycocyanin/metabolism , Phycocyanin/genetics , Phycobilins/metabolism , Phycoerythrin/metabolism , Phycoerythrin/chemistry , Bile Pigments/metabolism , Light , Synthetic Biology/methods , Cyanobacteria/metabolism , Cyanobacteria/geneticsABSTRACT
The close relationship between infectious diseases and iron metabolism is well known, but a more detailed understanding based on current knowledge may provide new insights into the diagnosis and treatment of infectious diseases, considering the growing threat of antibiotic-resistant bacteria. This study investigated adult patients with bloodstream infections, temporal changes, and relationships between blood levels of iron and related markers, including hepcidin and lipocalin-2 (LCN2). We included 144 samples from 48 patients (mean age 72 years, 50% male), with 30 diagnosed with sepsis. During the acute phase of infection, blood levels of hepcidin and LCN2 increased rapidly, whereas iron levels decreased, with values in 95.8% of cases below the normal range (40-188 µg/dL). Later, hepcidin and LCN2 decreased significantly during the recovery phase, and the decreased iron concentrations were restored. In the case of persistent inflammation, iron remained decreased. Acute LCN2 levels were significantly higher in patients with sepsis (p < 0.01). Hypoferremia induced by increased hepcidin would reduce iron in the environment of extracellular pathogens, and the increased LCN2 would inhibit siderophores, resulting in the prevention of the pathogen's iron acquisition in each manner during the acute phase of bloodstream infection.
Subject(s)
Communicable Diseases , Sepsis , Humans , Male , Aged , Female , Hepcidins/metabolism , Lipocalin-2/metabolism , Iron/metabolism , Siderophores/metabolismABSTRACT
It is estimated that during FY 2018, food waste of 25.31 million tons and food loss of 6 million tons occurred in Japan. Of this total amount, 3.24 million tons of waste was generated from business, including the food manufacturing, wholesale, retail, and restaurant industries, and 2.76 million tons of waste was generated from households. Thus, it is crucial to mitigate both upstream and downstream food loss. As consumption patterns greatly influence not only downstream but also upstream food loss, special emphasis must be placed on increasing consumers' awareness of this global issue, and several programs have been initiated to this end. Our research reveals that alongside awareness, enhancing consumers' skills is of vital importance to efficiently reduce downstream food loss. Additionally, business operators must invest in improving the skills of those in charge to minimize food loss in commercial setups. Educating both consumers and businesses with the requisite skills to lessen food loss is equally essential. The authors are developing impactful serious games to help impart such education. These include a vegetable supply chain game (Veggie Mart Game), where consumers are players, and a milk supply chain game (Milky-Chain Game), where businesses are players. This paper introduces the authors' current research on reduction of food loss.
Subject(s)
Food Supply , Refuse Disposal , Vegetables , Commerce , AgricultureABSTRACT
Depressive disorders are partially attributed to chronic inflammation associated with the tryptophan (Trp)-kynurenine (Kyn) pathway. Recent evidence suggests that anti-inflammatory agents may reduce the risk of depression. The present study aimed to elucidate the potential of the citrus flavonoid hesperidin, which exhibits anti-inflammatory activity, in suppressing the Trp-Kyn pathway in the brain, using a lipopolysaccharide (LPS)-induced inflammation mouse model. Dietary hesperidin was found to suppress activation of the Trp-Kyn pathway in the prefrontal cortex. In addition, it reduced systemic LPS-induced signs of illness, such as low skin temperature and enhanced leukocyte count in the blood. However, dietary supplementation with hesperidin did not improve body weight loss, food intake, water intake, or splenic increases in leukocyte numbers in the LPS model. Collectively, the results suggest that dietary hesperidin can partially regulate central and peripheral events linked to inflammation in LPS mouse models.
ABSTRACT
With the accumulation of knowledge on the relation between psychological stress and gut microbiota, there is growing interest in controlling stress and/or mood disorders via probiotic supplementation. We aimed to examine the effect of probiotic Bifidobacterium bifidum TMC3115 (TMC3115) supplementation using a sub-chronic and mild social defeat stress murine model in this study. TM3115 supplementation maintained body weight gain and alleviated a polydipsia-like symptom induced by the stress. In the analyses of fecal and cecal bacterial profiles, expansions of Proteobacteria in stressed mice and increases in Actinobacteria and Bifidobacterium in mice supplemented with TMC3115 were observed. There was no marked difference in the diversity of cecal bacteria between the tested mice. Elevated serum levels of inflammatory markers such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 were observed in the stressed mice, while TMC3115 only reduced the IL-6 level. These findings suggest that TMC3115 supplementation confers tolerance to psychosocial stress in the host through modulation of the gut microbiota and alleviation of stress-induced inflammatory responses. Furthermore, it may be expected to exert prevention and treatment of disorders related to peripheral IL-6, including depression.
Subject(s)
Bifidobacterium bifidum , Probiotics , Animals , Bifidobacterium bifidum/physiology , Dietary Supplements , Mice , Probiotics/pharmacology , Social Defeat , Stress, PsychologicalABSTRACT
AIM: Heart failure is increasing in Japan, in particular that with preserved ejection fraction (HFpEF) prevalent in older-aged patients. The purpose of this study was to investigate the pathophysiology during the early stage of left ventricular (LV) diastolic dysfunction by the quantitative proteome analysis of human myocardium. METHODS: Among 331 post-mortem autopsy patients, we selected 23 patients (aged 79 ± 9.6 years) with echocardiographic data and without major comorbidities, except hypertension. Cryopreserved autopsy tissue of the LV myocardium was subjected to proteome analysis. LV diastolic function was evaluated by echocardiographic data. Thirteen patients were classified into the impaired diastolic function (IDF) group, and 10 the normal cardiac function group. We performed comparative proteome analysis between the IDF and normal groups by isobaric tags for relative and absolute quantitation (iTRAQ) using nano-liquid chromatography-tandem mass spectrometry. RESULTS: The iTRAQ-based proteome analysis revealed 57 differentially expressed proteins in the IDF group. Molecular network analysis of differentially expressed proteins indicated that endoplasmic reticulum (ER) stress was a potentially important event. Furthermore, the expressions of proteins associated with the ER stress response, such as glucose-regulated protein 78 kDa, inositol-requiring kinase 1α and spliced X-box binding protein 1, were significantly decreased in the IDF group. CONCLUSIONS: This study suggested that reduced ER stress responses were involved during the early stage of LV diastolic dysfunction. Geriatr Gerontol Int â¢â¢; â¢â¢: â¢â¢-â¢â¢ Geriatr Gerontol Int 2021; 21: 577-583.
Subject(s)
Endoplasmic Reticulum Stress , Heart Failure , Heart/diagnostic imaging , Ventricular Dysfunction, Left/physiopathology , Ventricular Function, Left/physiology , Aged , Echocardiography , Female , Humans , Japan , Male , Myocardium , Proteome , Stroke VolumeABSTRACT
In this study, we investigated the effects of dietary supplementation of Citrus tumida hort. ex Tanaka on food intake, body and fat tissue weights, and metabolic profiles of plasma and liver in mice. Supplementation with 5% (w/w) of peels of immature C. tumida (PIC) for 4 weeks significantly suppressed body weight gain and decreased adipose tissue weight in epididymal, perirenal, and subcutaneous fats. Metabolome analyses showed that 2-hydroxyvaleric acid levels were reduced in the blood plasma of mice fed with PIC. PIC supplementation significantly elevated dipeptide (Thr-Asp, Ser-Glu, and Ala-Ala), glucuronic acid, and S-methylglutathione levels, and significantly reduced betaine aldehyde levels in the liver. In conclusion, PIC supplementation affects the metabolism of fatty acids, pectin, glutathione, and choline, showing potential beneficial effects for metabolic syndrome and obesity. PIC may be developed as a functional food and used in the treatment of these diseases.
Subject(s)
Citrus , Dietary Supplements , Eating/physiology , Fruit , Liver/metabolism , Metabolome , Plasma/metabolism , Adipose Tissue , Animals , Betaine/analogs & derivatives , Betaine/analysis , Betaine/metabolism , Glucuronic Acid/metabolism , Lipid Metabolism , Male , Metabolic Syndrome/diet therapy , Metabolomics/methods , Mice , Mice, Inbred C57BL , Obesity/diet therapy , Weight GainABSTRACT
Depressive disorders are partly caused by chronic inflammation through the kynurenine (KYN) pathway. Preventive intervention using anti-inflammatory reagents may be beneficial for alleviating the risk of depression. In this study, we focused on the Japanese local citrus plant, Citrus tumida hort. ex Tanaka (C. tumida; CT), which contains flavonoids such as hesperidin that have anti-inflammatory actions. The dietary intake of 5% immature peels of CT fruits slightly increased stress resilience in a subchronic and mild social defeat (sCSDS) model in mice. Moreover, the dietary intake of 0.1% hesperidin significantly increased stress resilience and suppressed KYN levels in the hippocampus and prefrontal cortex in these mice. In addition, KYN levels in the hippocampus and prefrontal cortex were significantly correlated with the susceptibility to stress. In conclusion, these results suggest that dietary hesperidin increases stress resilience by suppressing the augmentation of KYN signaling under sCSDS.
Subject(s)
Citrus/chemistry , Diet , Hesperidin/administration & dosage , Hippocampus/drug effects , Kynurenine/metabolism , Prefrontal Cortex/drug effects , Resilience, Psychological/drug effects , Social Behavior , Stress, Psychological/prevention & control , Animals , Behavior, Animal , Corticosterone/blood , Hesperidin/pharmacology , Hippocampus/metabolism , Interleukin-1beta/blood , Interleukin-6/blood , Kynurenine/blood , Male , Mice , Mice, Inbred C57BL , Mice, Inbred ICR , Prefrontal Cortex/metabolism , Tryptophan/bloodABSTRACT
Citrus fruits have several potential benefits for maintaining our health. In this study, we investigated the anti-obesity effects of immature Citrus tumida hort. ex Tanaka (C. tumida) peels using an acute obesity mice model. C57BL/6J male mice were divided into 2 groups; HFD-LL subjected to a high fat diet (HFD) and constant light exposure (LL), and HFDC-LL subjected to a HFD containing immature peel powder of C. tumida (5% w/w) and LL. Dietary ingestion of immature C. tumida peels significantly suppressed body weight gain following decreased epidydimal, perirenal, and subcutaneous fat weights. Blood levels of triglyceride and total cholesterol in the HFDC-LL were significantly lower than those in the HFD-LL group; however, there was no significant difference in food or calorie intake between the 2 groups. These results suggested that immature C. tumida peels have a beneficial effect on the prevention of obesity and metabolic syndrome via its biochemical activities of lipid metabolism.
Subject(s)
Anti-Obesity Agents/pharmacology , Citrus , Diet/methods , Obesity/diet therapy , Plant Extracts/pharmacology , Acute Disease , Adiposity/drug effects , Animals , Cholesterol/blood , Diet, High-Fat/adverse effects , Disease Models, Animal , Male , Mice , Mice, Inbred C57BL , Obesity/blood , Obesity/etiology , Triglycerides/blood , Weight Gain/drug effectsABSTRACT
In this paper, we report the development, evaluation, and application of ultra-small low-power wireless sensor nodes for advancing animal husbandry, as well as for innovation of medical technologies. A radio frequency identification (RFID) chip with hybrid interface and neglectable power consumption was introduced to enable switching of ON/OFF and measurement mode after implantation. A wireless power transmission system with a maximum efficiency of 70% and an access distance of up to 5 cm was developed to allow the sensor node to survive for a duration of several weeks from a few minutes' remote charge. The results of field tests using laboratory mice and a cow indicated the high accuracy of the collected biological data and bio-compatibility of the package. As a result of extensive application of the above technologies, a fully solid wireless pH sensor and a surgical navigation system using artificial magnetic field and a 3D MEMS magnetic sensor are introduced in this paper, and the preliminary experimental results are presented and discussed.
Subject(s)
Prostheses and Implants , Animal Husbandry , Animals , Cattle , Mice , Radio Frequency Identification Device , Wireless TechnologyABSTRACT
Diverse commercially available feeds are used in animal studies according to the purpose of the studies. We sought to understand the relationship between feed ingredients and their effects on animal physiology and behaviors. Here, we investigated how male laboratory mice (C57BL/6J ("B6") mice) were affected by chronic feeding with two commercially available diets, a non-purified diet (MF) and a semi-purified diet (AIN-93G). In B6 mice, both diets similarly induced spontaneous activities in the home cage and the open field box, anxiety in the elevated plus maze test, and depressive-like behaviors in tail-suspension and forced-swimming tests, and with both diets, similar data were obtained on calorie intake, water intake, body weight gain, and plasma corticosterone levels. By contrast, liver weight was significantly higher in MF-fed B6 mice than in AIN-93G-fed B6 mice. Furthermore, the cecum microbiome was drastically affected by the diets, and, specifically, Allobaculum was the major genus (43.4%) in the cecum microbiota of AIN-93G-fed mice but its abundance was reduced (to 3.8%) in the case of MF-fed mice. Future studies should address whether the differences in diet purity and cecum microbiota influence brain functions and behaviors in B6 mice.
Subject(s)
Animal Feed , Behavior, Animal/physiology , Cecum/microbiology , Corticosterone/blood , Microbiota , Animals , Diet , Male , Mice , Mice, Inbred C57BL , Motor Activity/physiologyABSTRACT
Neopeltolide, an antiproliferative marine macrolide, is known to specifically inhibit complex III of the mitochondrial electron transport chain (mETC). However, details of the biological mode-of-action(s) remain largely unknown. This work demonstrates potent cytotoxic activity of synthetic neopeltolide analogue, 8,9-dehydroneopeltolide (8,9-DNP), against starved human pancreatic adenocarcinoma PANC-1 cells and human non-small cell lung adenocarcinoma A549 cells. 8,9-DNP induced rapid dissipation of the mitochondrial membrane potential and depletion of intracellular ATP level in nutrient-deprived medium. Meanwhile, in spite of mTOR inhibition under starvation conditions, impairment of cytoprotective autophagy was observed as the lipidation of LC3-I to form LC3-II and the degradation of p62 were suppressed. Consequently, cells were severely deprived of energy sources and underwent necrotic cell death. The autophagic flux inhibited by 8,9-DNP could be restored by glucose, and this eventually rescued cells from necrotic death. Thus, 8,9-DNP is a potent anti-austerity agent that impairs mitochondrial ATP synthesis and cytoprotective autophagy in starved tumor cells.
Subject(s)
Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Autophagy/drug effects , Macrolides/pharmacology , Mitochondria/drug effects , Oxazoles/pharmacology , A549 Cells , Adenocarcinoma/drug therapy , Adenocarcinoma/metabolism , Adenosine Triphosphate/metabolism , Animals , Humans , Membrane Potential, Mitochondrial/drug effects , Mitochondria/physiology , Necrosis/chemically induced , Necrosis/physiopathology , Porifera/chemistry , Tumor Hypoxia/physiology , Tumor Microenvironment/drug effects , Tumor Microenvironment/physiologyABSTRACT
Serum (1â3) beta-D-glucan (BG) measurement is a useful test for systemic mycoses, and often used. On the other hand, various factors, including administration of intravenous immunoglobulins (IVIG) may cause false-positives. In the present study, we measured BG concentration of seven IVIG preparations with three lots respectively. BG levels varied with individual IVIG preparations (<3.0 - >300 pg/mL), and contamination from manufacturing processes was suspected. With serum BG concentration of clinical specimens obtained in Niigata University Medical & Dental Hospital, the difference between before and after administration of IVIG were calculated. The false-positive rate of BG due to IVIG administration was 9.8 %, and the positive predective value was reduced to 37.5%. Above all, administration of IVIG can complicate the BG test's interpretation, and caution is required.
Subject(s)
beta-Glucans/blood , gamma-Globulins/analysis , Aged , Female , Humans , Infusions, Intravenous , Male , Middle Aged , gamma-Globulins/administration & dosageABSTRACT
(+)-Neopeltolide is a marine macrolide natural product that exhibits potent antiproliferative activity against several human cancer cell lines. Previous study has established that this natural product primarily targets the complex III of the mitochondrial electron transport chain. However, the biochemical mode-of-actions of neopeltolide have not been investigated in detail. Here we report that (-)-8,9-dehydroneopeltolide (8,9-DNP), a more accessible synthetic analogue, shows potent cytotoxicity against human promyelocytic leukemia HL-60 cells preferentially under energy stress conditions. Nuclear morphology analysis, as well as DNA ladder assay, indicated that 8,9-DNP induced significant nuclear condensation/fragmentation and DNA fragmentation, and these events could be suppressed by preincubating the cells with a pan-caspase inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD). Immunoblot analysis demonstrated the release of cytochrome c from the mitochondria and the cleavage of full-length caspase-3 and poly(ADP-ribose) polymerase (PARP). These results indicated that 8,9-DNP induced caspase-dependent apoptotic programmed cell death under energy stress conditions. It was also found that 8,9-DNP induced non-apoptotic cell death in the presence/absence of zVAD under energy stress conditions. Immunoblot analysis showed the intracytosolic release of apoptosis-inducing factor (AIF), although it did not further translocate to the nucleus. It appears most likely that, in the presence of zVAD, 8,9-DNP triggered necrotic cell death as a result of severe intracellular ATP depletion.
Subject(s)
Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Leukemia, Promyelocytic, Acute/drug therapy , Macrolides/pharmacology , Oxazoles/pharmacology , Adenosine Triphosphate/metabolism , Apoptosis Inducing Factor/metabolism , Caspase 3/metabolism , Cell Death/drug effects , Cytochromes c/metabolism , DNA Fragmentation/drug effects , HL-60 Cells , Humans , Leukemia, Promyelocytic, Acute/pathology , Mitochondria/metabolism , Poly(ADP-ribose) Polymerases/metabolismABSTRACT
The aggregation of the 42-residue amyloid ß-protein (Aß42) is involved in the pathogenesis of Alzheimer disease (AD). Numerous flavonoids exhibit inhibitory activity against Aß42 aggregation, but their mechanism remains unclear in the molecular level. Here we propose the site-specific inhibitory mechanism of (+)-taxifolin, a catechol-type flavonoid, whose 3',4'-dihydroxyl groups of the B-ring plays a critical role. Addition of sodium periodate, an oxidant, strengthened suppression of Aß42 aggregation by (+)-taxifolin, whereas no inhibition was observed under anaerobic conditions, suggesting the inhibition to be associated with the oxidation to form o-quinone. Because formation of the Aß42-taxifolin adduct was suggested by mass spectrometry, Aß42 mutants substituted at Arg(5), Lys(16), and/or Lys(28) with norleucine (Nle) were prepared to identify the residues involved in the conjugate formation. (+)-Taxifolin did not suppress the aggregation of Aß42 mutants at Lys(16) and/or Lys(28) except for the mutant at Arg(5). In addition, the aggregation of Aß42 was inhibited by other catechol-type flavonoids, whereas that of K16Nle-Aß42 was not. In contrast, some non-catechol-type flavonoids suppressed the aggregation of K16Nle-Aß42 as well as Aß42. Furthermore, interaction of (+)-taxifolin with the ß-sheet region in Aß42 was not observed using solid-state NMR unlike curcumin of the non-catechol-type. These results demonstrate that catechol-type flavonoids could specifically suppress Aß42 aggregation by targeting Lys residues. Although the anti-AD activity of flavonoids has been ascribed to their antioxidative activity, the mechanism that the o-quinone reacts with Lys residues of Aß42 might be more intrinsic. The Lys residues could be targets for Alzheimer disease therapy.
Subject(s)
Amyloid beta-Peptides/chemistry , Amyloid/chemistry , Catechols/chemistry , Lysine/chemistry , Peptide Fragments/chemistry , Quercetin/analogs & derivatives , Alzheimer Disease/drug therapy , Alzheimer Disease/metabolism , Amyloid/antagonists & inhibitors , Amyloid/metabolism , Amyloid beta-Peptides/antagonists & inhibitors , Amyloid beta-Peptides/metabolism , Catechols/metabolism , Humans , Lysine/metabolism , Norleucine/chemistry , Norleucine/metabolism , Peptide Fragments/antagonists & inhibitors , Peptide Fragments/metabolism , Quercetin/chemistry , Quercetin/metabolismABSTRACT
The 42-mer amyloid ß-protein (Aß42) oligomers cause neurotoxicity and cognitive impairment in Alzheimer's disease (AD). We previously identified the toxic conformer of Aß42 with a turn at positions 22-23 ("toxic" turn) to form oligomers and to induce toxicity in rat primary neurons, along with the non-toxic conformer with a turn at positions 25-26. G25P-Aß42 and E22V-Aß42 are non-toxic mutants that disfavor the "toxic" turn. Here we hypothesize that these non-toxic mutants of Aß42 could suppress Aß42-induced neurotoxicity, and examined their effects on the neurotoxicity, aggregation, and levels of the toxic conformer, which was evaluated by dot blotting using a monoclonal antibody (11A1) against the toxic conformer. G25P-Aß42 and E22V-Aß42 suppressed the neurotoxicity and aggregation of Aß42 as well as the formation of the toxic conformer. The neurotoxicity induced by Aß42 was also significantly reduced by the treatment of 11A1, but not of Aß-sequence specific antibodies (6E10 and 4G8). Since recent studies indicate that Aß oligomers contain parallel ß-sheet, the present results suggest that the non-toxic mutants of Aß42 without the "toxic" turn could prevent the propagation process of the toxic conformer of Aß42 resulting in suppression of the formation of the toxic oligomers. This could be a promising strategy for AD therapeutics.
Subject(s)
Amyloid beta-Peptides/chemistry , Amyloid beta-Peptides/toxicity , Neurons/drug effects , Neurons/pathology , Peptide Fragments/chemistry , Peptide Fragments/toxicity , Alzheimer Disease/drug therapy , Alzheimer Disease/pathology , Animals , Apoptosis/drug effects , Cell Survival/drug effects , Humans , Isomerism , Rats , Rats, WistarABSTRACT
Silymarin, the seed extract of Silybium marianum, has preventive effects against Alzheimer's disease-like pathogenesis in vivo. We isolated (+)-taxifolin (4) from silymarin as an inhibitor of aggregation of the 42-residue amyloid ß-protein. Structure-activity relationship studies revealed the 3',4'-dihydroxyl groups to be critical to the anti-aggregative ability, whereas the 7-hydroxyl group and the stereochemistry at positions 2 and 3 were not important.
Subject(s)
Amyloid beta-Peptides/chemistry , Peptide Fragments/chemistry , Protein Multimerization/drug effects , Quercetin/analogs & derivatives , Silymarin/chemistry , Protein Structure, Secondary , Quercetin/chemistry , Quercetin/isolation & purification , Quercetin/pharmacology , Structure-Activity RelationshipABSTRACT
The 42-mer amyloid ß-protein (Aß42) aggregates to form soluble oligomers that cause memory loss and synaptotoxicity in Alzheimer's disease (AD). Oxidative stress is closely related to the pathogenesis of AD. We previously identified the toxic conformer of Aß42 with a turn at positions 22 and 23 ("toxic turn") by solid-state NMR and demonstrated that a monoclonal antibody (11A1) against the toxic turn in Aß42 mainly detected the oligomer in the brains of AD patients. Our recent study suggested that oxidative stress is a key factor of the oligomerization and cognitive impairment induced by Aß overproduction in vivo. However, the involvement of the toxic conformer in Aß42-induced oxidative damage remains unclear. To investigate this mechanism, we examined the levels of intracellular reactive oxygen species (ROS) and neurotoxicity in rat primary neurons using E22P-Aß42, a mutant that induces a turn at positions 22 and 23, and E22V-Aß42, a turn-preventing mutant. E22P-Aß42, but not E22V-Aß42, induced greater ROS production than Wt-Aß42 in addition to potent neurotoxicity. Interestingly, the formation of the toxic conformer in both E22P-Aß42 and Wt-Aß42 probed by the 11A1 antibody preceded Aß42-induced neurotoxicity. Trolox (a radical scavenger) and Congo red (an aggregation inhibitor) significantly prevented the neurotoxicity and intracellular ROS induced by E22P-Aß42 and Wt-Aß42, respectively. These results suggest that Aß42-mediated toxicity is caused by the turn that favors toxic oligomers, which increase generation of ROS.
Subject(s)
Amyloid beta-Peptides/chemistry , Neurons/drug effects , Oxidative Stress/drug effects , Peptide Fragments/chemistry , Alzheimer Disease/metabolism , Amyloid beta-Peptides/genetics , Amyloid beta-Peptides/toxicity , Animals , Antioxidants/chemistry , Antioxidants/pharmacology , Blotting, Western , Cell Survival/drug effects , Cells, Cultured , Chromans/pharmacology , Congo Red , Female , Free Radical Scavengers/pharmacology , Mutation/genetics , Neurotoxins/chemistry , Neurotoxins/toxicity , Peptide Fragments/genetics , Peptide Fragments/toxicity , Pregnancy , Protein Conformation , Rats , Rats, Wistar , Reactive Oxygen Species/metabolism , Tetrazolium Salts , Thiazoles , Vitamin E/analogs & derivatives , Vitamin E/chemistry , Vitamin E/pharmacologyABSTRACT
Abl is a nonreceptor tyrosine kinase and plays an essential role in the modeling and remodeling of F-actin by transducing extracellular signals. Abl and its paralog, Arg, are unique among the tyrosine kinase family in that they contain an unusual extended C-terminal half consisting of multiple functional domains. This structural characteristic may underlie the role of Abl as a mediator of upstream signals to downstream signaling machineries involved in actin dynamics. Indeed, a group of SH3-containing accessory proteins, or adaptor proteins, have been identified that bind to a proline-rich domain of the C-terminal portion of Abl and modulate its kinase activity, substrate recognition, and intracellular localization. Moreover, the existence of signaling cascade and biological outcomes unique to each adaptor protein has been demonstrated. In this paper, we summarize functional roles and mechanisms of adaptor proteins in Abl-regulated actin dynamics, mainly focusing on a family of adaptor proteins, Abi. The mechanism of Abl's activation and downstream signaling mediated by Abi is described in comparison with those by another adaptor protein, Crk.
ABSTRACT
Osteoclasts are multinucleated giant cells that reside in osseous tissues and resorb bone. Signaling mediated by receptor activator of nuclear factor (NF)-κB (RANK) and its ligand leads to the nuclear factor of activated T cells 2/c1 (NFAT2 or NFATc1) expression, a critical step in the formation of functional osteoclasts. In addition, adaptor proteins harboring immunoreceptor tyrosine-based activation motifs, such as DNAX-activating protein of 12 kDa (DAP12), play essential roles. In this study, we identified the gene encoding the lectin Siglec-15 as NFAT2-inducible, and we found that the protein product links RANK ligand-RANK-NFAT2 and DAP12 signaling in mouse osteoclasts. Both the recognition of sialylated glycans by the Siglec-15 V-set domain and the association with DAP12 through its Lys-272 are essential for its function. When Siglec-15 expression was knocked down, fewer multinucleated cells developed, and those that did were morphologically contracted with disordered actin-ring structures. These changes were accompanied by significantly reduced bone resorption. Siglec-15 formed complexes with Syk through DAP12 in response to vitronectin. Furthermore, chimeric molecules consisting of the extracellular and transmembrane regions of Siglec-15 with a K272A mutation and the cytoplasmic region of DAP12 significantly restored bone resorption in cells with knocked down Siglec-15 expression. Together, these results suggested that the Siglec-15-DAP12-Syk-signaling cascade plays a critical role in functional osteoclast formation.