• Genomic and Functional Analysis of Vesicular Inhibitory Amino Acid Transporter During Mouse Embryogenesis

      Oh, Won-Jong; Institute of Molecular Medicine and Genetics (2006-01)
      The specification of particular neuronal phenotypes during embryonic development requires the appropriate activation and regulation of genes encoding the proteins required for neurotransmitter synthesis, vesicular packaging and re-uptake from the synaptic cleft. Each neurotransmitter is packaged into synaptic vesicles by its own distinct vesicular transporter. In addition, neurotransmitter packaging is well controlled by other co-factors (reviewed in Ahnert-Hilger et al., 2003). Components of GABAergic neurons GABAergic neurons are the principal inhibitory neurons in the mammalian central nervous system (CNS), where GABA is synthesized from glutamate by two glutamate decarboxylases (GAD), namely GAD65 (Gad2) and GAD67 (Gad1) (Erlander et al., 1991). GABA is then loaded into synaptic vesicles by the vesicular inhibitory amino acid transporter (VIAAT, also known as VGAT). Four GABA transporters (GAT 1-4) are responsible for the re-uptake of GABA from the synaptic cleft through the plasma membrane. Inhibitory GABAergic transmission is mediated by binding of GABA to its ionotropic receptors, GABAA and GABAC, which are ligand-gated chloride channels, and its metabotropic receptor, GABAB (Fig. 1).
    • Influence of DNA Ends on Structure and Function of the DNA-dependent Protein Kinase

      Jovanovic, Marko; Institute of Molecular Medicine and Genetics (2006-12)
      Non-homologous end joining is a major DNA double-strand break repair pathway in mammalian cells. The DNA-dependent protein kinase (DNA-PK), consisting of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and Ku heterodimer, is hypothesized to be a key regulator of the pathway. Available data suggest DNA-PKcs may exert this regulatory function by controlling access to the DNA termini and by phosphorylation of itself and other proteins. I further characterized DNA-PK-DNA interaction by studying binding of DNA-PKcs and Ku to oligonucleotides with chemically defined end structures under conditions that preclude synapsis between opposing DNA ends. Binding of DNA-PKcs to DNA varied with the end structure in a manner that suggests that partial melting of DNA ends is necessary for the formation of a stable, enzymatically active complex. Unexpectedly, these studies also revealed that ATP, as well as its nonhydrolyzable analog AMP-PNP, have an allosteric effect on the interaction of DNA-PKcs with DNA.