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We developed a new strategy for construction of a biosensor for the neurotransmitter dopamine. The biosensor was constructed by one-step electrochemical deposition of a nanocomposite in aqueous solution at pH 7.0, consisting of molybdenum disulfide, multi-walled carbon nanotubes, and polypyrrole. A series of analytical methods was performed to investigate the surface characteristics and the improved electrocatalytic effect of the nanocomposite, including cyclic voltammetry, electrochemical impedance spectroscopy, field-emission scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The constructed biosensor showed high sensitivity (1.130 μAμM −1 cm −2 ) with a dynamic linearity range of 25–1000 nM and a detection limit of 10 nM. Additionally, the designed sensor exhibited strong anti-interference ability and satisfactory reproducibility. The practical application of the sensor was manifested for the ex vivo determination of dopamine neurotransmitters using brain tissue samples of a mouse Parkinson's disease model. [ABSTRACT FROM AUTHOR]

Highlights: [•] We designed a novel peptide sequence to inhibit GSK3beta. [•] Activation of the peptide requires the kinase activities of Akt and GSK3beta. [•] GSK3beta is inhibited by the peptide only in response to the insulin signaling. [•] We propose a novel concept to develop a drug. [ABSTRACT FROM AUTHOR]

Abstract: Wnt/β-catenin signaling controls a variety of cellular processes, including cell growth, oncogenesis, and development. Upon Wnt stimulation, the intracellular region of the coreceptor, LRP6 or 5, is phosphorylated by the membrane-recruited GSK3β and CK1. The cytoplasmic domain of LRP6/5 contains one Ser/Thr cluster and the PPPSP motifs, both of which are essential for propagation of the signal. While the phosphorylated PPPSP motifs are known to directly inhibit GSK3β, the biochemical role of the phosphorylated Ser/Thr cluster remains to be elucidated. Herein, we reveal that the Ser/Thr cluster plays an important role in the phosphorylation of the PPPSP motif. Interestingly, we observe that GSK3β activity on the PPPSP motif requires a high ATP concentration, close to that of the physiological condition. Taken together, these data suggest that the phosphorylated Ser/Thr cluster serves as a docking site for GSK3β to promote the phosphorylation of the PPPSP motif. Our results provide insight into the molecular mechanism for the initial events of the Wnt/β-catenin signaling. [Copyright &y& Elsevier]

Abstract: Vitamin C (VC) has a strong antioxidant function evident as its ability to scavenge superoxide radicals in vitro. We verified that this property actually exists in vivo by using a real-time imaging system in which Lucigenin is the chemiluminescent probe for detecting superoxide in senescence marker protein-30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice, which cannot synthesize VC in vivo. SMP30/GNL KO mice were given 1.5g/L VC [VC(+)] for 2, 4, or 8 weeks or denied VC [VC(−)]. At 4 and 8 weeks, VC levels in brains from VC(−) KO mice were <6% of that in VC(+) KO mice. Accordingly, superoxide-dependent chemiluminescence levels determined by ischemia-reperfusion at the 4- and 8 weeks test intervals were 3.0-fold and 2.1-fold higher, respectively, in VC(−) KO mice than in VC(+) KO mice. However, total superoxide dismutase activity and protein levels were not altered. Thus, VC depletion specifically increased superoxide generation in a model of the living brain. [Copyright &y& Elsevier]

Abstract: The transition from chemotherapy-responsive cancer cells to chemotherapy-resistant cancer cells is mainly accompanied by the increased expression of multi-drug resistance 1 (MDR1). We found that hepatitis-B-virus X protein (HBx) increases the transcriptional activity and protein level of MDR1 in a hepatoma cell line, H4IIE. In addition, HBx overexpression made H4IIE cells more resistant to verapamil-uptake. HBx stabilized hypoxia-inducible factor-1α (HIF-1α) and induced the nuclear translocation of C/EBPβ. Reporter gene analyses showed that HBx increased the reporter activity in the cells transfected with the reporter containing MDR1 gene promoter. Moreover, the luciferase reporter gene activity was significantly inhibited by HIF-1α siRNA but not by overexpression of C/EBP dominant negative mutant. These results imply that HBx increases the MDR1 transporter activity through the transcriptional activation of the MDR1 gene with HIF-1α activation, and suggest HIF-1α for the therapeutic target of HBV-mediated chemoresistance. [Copyright &y& Elsevier]