Lipopolysaccharide inhibits transforming growth factor-beta1-stimulated Smad6 expression by inducing phosphorylation of the linker region of Smad3 through a TLR4–IRAK1–ERK1/2 pathway

AbstractSmad6, one of the inhibitory Smads, plays an important role in transforming growth factor-beta1 (TGF-β1)-mediated negative regulation of pro-inflammatory signaling. In this study, we found that bacterial endotoxin lipopolysaccharide (LPS) inhibits TGF-β1-induced expression of Smad6 in RAW264.7 cells. This repression was accompanied by increased Smad3 linker phosphorylation at Thr-179 and Ser-208 and was dependent on ERK1/2 activity via the TLR4–IRAK1-linked signaling cascade. The expression of a mutant Smad3, that lacks the phosphorylation sites in the linker regions, significantly reversed the inhibitory effect of LPS on TGF-β1-induced Smad6 expression and its anti-inflammatory capacity. Collectively, our findings show how LPS pro-inflammatory signal antagonizes the anti-inflammatory activity of TGF-β1

Probing the Determinants of the Molecular Recognition in Metal-Dependent Deacetylase.

Metal-dependent deacetylases catalyze a variety of essential reactions in nature However,most metallohydrolases can be activated by a number of divalent metal ions, such as Zn(II) or Fe(II). Human metal-dependent metalloenzyme, histone deacetylases 8 (HDAC 8), catalyze the deacetylation of acetylated lysine residues on histones and other protein substrates. Although it was known to be Zn(II)-metalloenzyme, there is growing evidence which indicates it is also activated by Fe(II). HDAC8 was more active with Fe(II) than Zn(II) in vitro, and exhibits Fe(II)-like activity in vivo, suggesting that many “Zn”-enzymes may utilize either Fe or Zn cofactors in vivo depending on cellular conditions. Here I measured the metal binding kinetics and thermodynamics for HDAC8 using newly developed fluorescence polarization assay. Next, the determinants governing the metal specificity of HDAC8 was explored. Alterations in second shell ligand environment significantly affect the reactivity (kcat/KM), binding affinity (koff and KD) for Zn/Fe-bound HDAC8 when compared to the wild-type. Monovalent binding, other metal binding sites in HDAC8, also had an effect on divalent metal binding by decreasing dissociation rate constant. Additionally, putative binding partner to HDAC8, poly (rC) binding protein, was investigated to determine the interaction between two proteins in vitro and in vivo. This finding revealed that two proteins bind to each other in a specific manner with μM affinity when apo-apo proteins interact. These all data suggest that HDAC8 is activated by either Zn or Fe based on various factors as a means of metal homeostasis. Finally, other deacetylase, UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC), was studied to generate novel potent inhibitor. LpxC catalyzes the committed step in Lipid A biosynthesis. Inhibitors of LpxC are targets for the development of antibacterials, since lipid A is essential for cell viability. For the development of more potent non-hydroxamate inhibitors, library of metal-binding fragments were screened against Escherichia Coli LpxC using high-throughpu mass spectrometry assay. A few potent hits (IC50 ≈ nM range) was identified. These results are important for understanding how best to inhibit the many clinically useful metalloprotein drug targets, as well as for understanding a potentially important new aspect of metal ion homeostasis and metalloprotein regulation.PHDChemical BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110349/1/byungkim_1.pd

Correlated Electronic Structures and the Phase Diagram of Hydrocarbon-based Superconductors

We have investigated correlated electronic structures and the phase diagram of electron-doped hydrocarbon molecular solids, based on the dynamical mean-field theory. We have found that the ground state of hydrocarbon-based superconductors such as electron-doped picene and coronene is a multi-band Fermi liquid, while that of non-superconducting electron-doped pentacene is a single-band Fermi liquid in the proximity of the metal-insulator transition. The size of the molecular orbital energy level splitting plays a key role in producing the superconductivity of electron-doped hydrocarbon solids. The multi-band nature of hydrocarbon solids would boost the superconductivity through the enhanced density of states at the Fermi level.X11910sciescopu