• Novel Cycloheximide Derivatives Targeting the Moonlighting Protein Mip Exhibit Specific Antimicrobial Activity Against Legionella pneumophila.

      Rasch, Janine; Theuerkorn, Martin; Ünal, Can; Heinsohn, Natascha; Tran, Stefan; Fischer, Gunter; Weiwad, Matthias; Steinert, Michael; Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany. (2015)
      Macrophage infectivity potentiator (Mip) and Mip-like proteins are virulence factors in a wide range of pathogens including Legionella pneumophila. These proteins belong to the FK506 binding protein (FKBP) family of peptidyl-prolyl-cis/trans-isomerases (PPIases). In L. pneumophila, the PPIase activity of Mip is required for invasion of macrophages, transmigration through an in vitro lung-epithelial barrier, and full virulence in the guinea pig infection model. Additionally, Mip is a moonlighting protein that binds to collagen IV in the extracellular matrix. Here, we describe the development and synthesis of cycloheximide derivatives with adamantyl moieties as novel FKBP ligands, and analyze their effect on the viability of L. pneumophila and other bacteria. All compounds efficiently inhibited PPIase activity of the prototypic human FKBP12 as well as Mip with IC50-values as low as 180 nM and 1.7 μM, respectively. Five of these derivatives inhibited the growth of L. pneumophila at concentrations of 30-40 μM, but exhibited no effect on other tested bacterial species indicating a specific spectrum of antibacterial activity. The derivatives carrying a 3,5-dimethyladamantan-1-[yl]acetamide substitution (MT_30.32), and a 3-ethyladamantan-1-[yl]acetamide substitution (MT_30.51) had the strongest effects in PPIase- and liquid growth assays. MT_30.32 and MT_30.51 were also inhibitory in macrophage infection studies without being cytotoxic. Accordingly, by applying a combinatorial approach, we were able to generate novel, hybrid inhibitors consisting of cycloheximide and adamantane, two known FKBP inhibitors that interact with different parts of the PPIase domain, respectively. Interestingly, despite the proven Mip-inhibitory activity, the viability of a Mip-deficient strain was affected to the same degree as its wild type. Hence, we also propose that cycloheximide derivatives with adamantyl moieties are potent PPIase inhibitors with multiple targets in L. pneumophila.
    • The phenotypes of ATG9, ATG16 and ATG9/16 knock-out mutants imply autophagy-dependent and -independent functions.

      Xiong, Qiuhong; Ünal, Can; Matthias, Jan; Steinert, Michael; Eichinger, Ludwig; Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany. (2015-04)
      Macroautophagy is a highly conserved intracellular bulk degradation system of all eukaryotic cells. It is governed by a large number of autophagy proteins (ATGs) and is crucial for many cellular processes. Here, we describe the phenotypes of Dictyostelium discoideum ATG16(-) and ATG9(-)/16(-) cells and compare them to the previously reported ATG9(-) mutant. ATG16 deficiency caused an increase in the expression of several core autophagy genes, among them atg9 and the two atg8 paralogues. The single and double ATG9 and ATG16 knock-out mutants had complex phenotypes and displayed severe and comparable defects in pinocytosis and phagocytosis. Uptake of Legionella pneumophila was reduced. In addition, ATG9(-) and ATG16(-) cells had dramatic defects in autophagy, development and proteasomal activity which were much more severe in the ATG9(-)/16(-) double mutant. Mutant cells showed an increase in poly-ubiquitinated proteins and contained large ubiquitin-positive protein aggregates which partially co-localized with ATG16-GFP in ATG9(-)/16(-) cells. The more severe autophagic, developmental and proteasomal phenotypes of ATG9(-)/16(-) cells imply that ATG9 and ATG16 probably function in parallel in autophagy and have in addition autophagy-independent functions in further cellular processes.