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Sim S.-E.,Seoul National University | Lee H.-R.,National Creative Research Initiative Center for Memory | Kim J.-I.,National Creative Research Initiative Center for Memory | Choi S.-L.,National Creative Research Initiative Center for Memory | And 7 more authors.
BMB Reports | Year: 2013

Phosphoinositide 3-kinases (PI3Ks) play key roles in synaptic plasticity and cognitive functions in the brain. We recently found that genetic deletion of PI3Kγ, the only known member of class IB PI3Ks, results in impaired N-methyl-D-aspartate receptor-dependent long-term depression (NMDAR-LTD) in the hippocampus. The activity of RalA, a small GTP-binding protein, increases following NMDAR-LTD inducing stimuli, and this increase in RalA activity is essential for inducing NMDAR-LTD. We found that RalA activity increased significantly in PI3Kγ knockout mice. Furthermore, NMDAR-LTDinducing stimuli did not increase RalA activity in PI3Kγ knockout mice. These results suggest that constitutively increased RalA activity occludes further increases in RalA activity during induction of LTD, causing impaired NMDARLTD. We propose that PI3Kγ regulates the activity of RalA, which is one of the molecular mechanisms inducing NMDARdependent LTD. © 2013 by the The Korean Society for Biochemistry and Molecular Biology.

Park J.W.,National Creative Research Initiative Center for Memory | Park A.-Y.,National Creative Research Initiative Center for Memory | Lee S.,National Creative Research Initiative Center for Memory | Yu N.-K.,Seoul National University | And 2 more authors.
Bioconjugate Chemistry | Year: 2010

We developed highly luminescent and cost-effective quantum dot (QD)-neutravidin (NTV) bioconjugates to detect the tyrosine kinase B (TrkB) receptors distributed in the cultured hippocampus neurons. Hippocampal neurons were incubated with biotinylated anti-TrkB antibody, followed by further incubation with QD-NTV bioconjugates. QD-NTV biomarkers on the extracellular domain of TrkB receptors were imaged by the combined atomic force microscope and confocal laser scanning microscope (AFM-CLSM) providing resolved (nanometer-scale) structural and fluorescent images. We found that TrkB receptors were distributed over the neuronal cell bodies (soma) and neurites. TrkB receptors in the somata looked more concentrated, but those in the neurites appeared punctate. Thus, our QD-based immunocytochemistry technique combined with an AFM-CLSM can be used for three-dimensional morphology of neurons on nanometer-scale structural resolution and their fluorescence images with QDs. Furthermore, this technique can be applied for real-time fluorescence imaging or long-term study of live neurons. © 2010 American Chemical Society.

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