Background and Purpose: Increasing evidence suggests that human cholestasis is closely associated with the accumulation and activation of hepatic macrophages.Research indicates that activation of PPARγ exerts liver protective effects in cholestatic liver disease (CLD), particularly by ameliorating inflammation and fibrosis, thus limiting disease progression. However, existing PPARγ agonists, such as troglitazone and rosiglitazone, have significant side effects that prevent their clinical application in the treatment of CLD. In this study, we found that tectorigenin alleviates intrahepatic cholestasis in mice by activating PPARγ.Experimental Approach: Wild-type mice were intragastrically administered α-naphthylisothiocyanate (ANIT) or fed a diet containing 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to simultaneously establish an experimental model of intrahepatic cholestasis and tectorigenin intervention, followed by determination of intrahepatic cholestasis and the mechanisms involved. In addition, PPARγ-deficient mice were administered ANIT and/or tectorigenin to determine whether tectorigenin exerts its liver protective effect by activating PPARγ.

HCoV-229E spike (S) protein mediates virion attachment to cells and subsequent fusion of the viral and cellular membranes. This protein is composed of an N-terminal receptor-binding domain (S1) and a C-terminal trans-membrane fusion domain (S2). S2 contains a highly conserved heptad repeat 1 and 2 (HR1 and HR2). In this study, the HRs sequences were designed and connected with a flexible linker. The recombinant fusion core protein was crystallized and its structure was solved at a resolution of 2.45 Å. Then we characterized the binding of HR1s and HR2s via both sequence alignment and structural analysis. The overall structures, especially the residues in some positions of HR2 are highly conserved. Fourteen hydrophobic and three polar residues from each HR1 peptide are packed in layers at the coiled-coil interface. These core amino acids can be grouped into seven heptad repeats. Analysis of hydrophobic and hydrophilic interactions between HR2 helix and HR1 helices, shows that the HR1 and HR2 polypeptides are highly complementary in both shape and chemical properties. Furthermore, the available knowledge concerning HCoV-229E fusion core may make it possible to design small molecule or polypeptide drugs targeting membrane fusion, a crucial step of HCoV-229E infection.

Energy generation, synthesis of biomass and detoxification of synthetic compounds are driven by electron transfer in all living organisms. Soluble quinone oxidoreductases (QORs) catalyze transfer of electrons from NADPH to substrates. The open reading frame Rv1454c of Mycobacterium tuberculosis (Mtb) encodes a NADPH-dependent QOR that is known to catalyze one-electron reduction of quinones to produce semiquinones. Here, we report the crystal structures of the apo-enzyme of MtbQOR and its binary complex with NADPH determined at 1.80 and 1.85A resolutions, respectively. The enzyme is bi-modular. Domain I binds the substrate, while domain II folds into a typical Rossmann fold for tethering NADPH. Binding of NADPH induces conformational changes. Among the known structures of QORs, MtbQOR exhibits the largest conformational change. Movement of Phe41 to stack against Ala244 results in partial closure of the active site. Comparison of the structure with homologs suggests a conserved topology. However, differences are observed in the region around the site of hydride transfer, highlighting differences in substrate specificities amongst the homologs. Unliganded as well as NADPH-bound MtbQOR crystallized as a dimer. Dimerization is mediated by homotypic intermolecular interactions involving main chain Ca as well as side-chain atoms of residues. The results of analytical ultracentrifugation analysis revealed that MtbQOR exists as a dimer in solution. Enzymatic assays indicate that MtbQOR prefers 9,10-phenanthrenequinone over 1,4-benzoquinone as a substrate. The ability to reduce quinones probably assists Mtb in detoxification of a range of harmful chemicals encountered in the host during invasion. DatabaseThe coordinates and structure factors for apo-and NADPH-bound MtbQOR have been deposited in the Protein Data Bank under accession codes 4RVS and 4RVU, respectively.

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