The alternative sigma factor, RpoS has been described as a central regulator of many stationary phase-inducible genes and a master stress-response regulator under various stress conditions. We constructed an rpoS mutant in Pseudomonas aeruginosa and investigated the role of rpoS gene in antibiotic tolerance. The survival of the rpoS mutant cells in stationary phase was approximately 70 times lower when compared with that of the parental strain at 37 degrees C for 2 h after the addition of biapenem. For imipenem, the survival was approximately 40 times lower. Heat stress promoted an increase in the survival of the parental strain to biapenem, but the same was not found to be the case for the rpoS mutant. Our results indicate that rpoS gene is involved in tolerance to antibiotics in P. aeruginosa during the stationary phase and heat stress. However, under osmotic stress, tolerance to biapenem was not dependent on the rpoS gene.

cIn Gram-negative bacteria, lipoproteins are transported to the outer membrane by the Lol system. In this process, lipoproteins are released from the inner membrane by the ABC transporter LolCDE and passed to LolA, a diffusible periplasmic molecular chaperone. Lipoproteins are then transferred to the outer membrane receptor protein, LolB, for insertion in the outer membrane. Here we describe the discovery and characterization of novel pyridineimidazole compounds that inhibit this process. Escherichia coli mutants resistant to the pyridineimidazoles show no cross-resistance to other classes of antibiotics and map to either the LolC or LolE protein of the LolCDE transporter complex. The pyridineimidazoles were shown to inhibit the LolA-dependent release of the lipoprotein Lpp from E. coli spheroplasts. These results combined with bacterial cytological profiling are consistent with LolCDE-mediated disruption of lipoprotein targeting to the outer membrane as the mode of action of these pyridineimidazoles. The pyridineimidazoles are the first reported inhibitors of the LolCDE complex, a target which has never been exploited for therapeutic intervention. These compounds open the door to further interrogation of the outer membrane lipoprotein transport pathway as a target for antimicrobial therapy.T he most distinguishing feature of Gram-negative bacteria is their cell envelope, which is comprised of both an inner and an outer membrane bilayer. The outer membrane has a unique composition of lipoproteins, ␤-barrel proteins, lipopolysaccharides, and phospholipids. Lipoproteins, membrane proteins that are covalently modified with lipids, are involved in a variety of integral cellular functions, such as the synthesis and maintenance of the cell surface and the transport of substrates (reviewed in reference 1). Lipoproteins are synthesized as precursors in the cytoplasm. Upon transit across the inner membrane by either the Sec or Tat machinery, the export signal peptide is cleaved, and attached to its amino terminus is a lipid moiety. This lipid serves as a membrane anchor for the lipoprotein. Some lipoproteins remain in the outer leaflet of the inner membrane, while others must cross the hydrophilic periplasmic space to the outer membrane. This sorting of lipoproteins to the outer membrane is achieved by the Lol system, which consists of five proteins (Fig. 1) (reviewed in reference 1). In this process, lipoproteins destined for the outer membrane are released from the inner membrane by the LolCDE complex, an inner membrane ABC transporter. LolCDE transfers the lipoproteins to LolA, a diffusible periplasmic chaperone (2, 3). LolA then transfers the lipoprotein to LolB, the outer membrane lipoprotein receptor, which incorporates these lipoproteins into the inner leaflet of the outer membrane (1, 4). This is in contrast to Grampositive bacteria, which have a single membrane bilayer; therefore, localization of lipoproteins to the cell surface requires only export through the cytoplasmic membrane and acylation (5).Infections c...

Fusion genes involving have recently been identified in precursor B-cell acute lymphoblastic leukemia, mutually exclusive of the common risk stratifying genetic abnormalities, although their true incidence and associated clinical characteristics remains unknown. We identified 16 acute lymphoblastic leukemia cases and 1 lymphoma case harboring fusions, including (n=10), (n=6) and one novel fusion. The incidence of fusions overall was 2.4% among consecutive B-cell acute lymphoblastic leukemia patients enrolled onto a single clinical trial. They frequently showed a cytoplasmic μ chain-positive pre-B immunophenotype and often expressed an aberrant CD5 antigen. Besides up- and down-regulation of and, elevated expression was also a characteristic feature of fusions-positive patients. Mutations of , recurrent in T-cell acute lymphoblastic leukemia, also showed an unexpectedly high frequency (50%) in these patients. fusion-positive patients were older (median age 9 years) with elevated WBC counts (median: 27,300/μl) at presentation, and, as a result, were mostly classified as NCI high-risk. Although they responded well to steroid treatment, fusion-positive patients showed a significantly worse outcome, with 53.3% relapse and subsequent death. Stem cell transplantation was ineffective as a salvage therapy. Interestingly, relapse was frequently associated with the presence of gene deletions. Our observations indicate that fusions comprise a distinct subgroup of precursor B-cell acute lymphoblastic leukemia with a characteristic immunophenotype and gene expression signature, associated with distinct clinical features.

SARS-CoV-2 precipitates respiratory distress by infection of airway epithelial cells and is often accompanied by acute kidney injury. We report that Kidney Injury Molecule-1/T cell immunoglobulin mucin domain 1 (KIM-1/TIM-1) is expressed in lung and kidney epithelial cells in COVID-19 patients and is a receptor for SARS-CoV-2. Human and mouse lung and kidney epithelial cells express KIM-1 and endocytose nanoparticles displaying the SARS-CoV-2 spike protein (virosomes). Uptake was inhibited both by anti-KIM-1 antibodies and by TW-37, our newly discovered inhibitor of KIM-1-mediated endocytosis. Enhanced KIM-1 expression by human kidney tubuloids increased uptake of virosomes. KIM-1 positive cells express less angiotensin-converting enzyme 2 (ACE2), the well-known receptor for SARS-CoV-2. Using microscale thermophoresis, the EC50 for KIM-1-SARS-CoV-2 spike protein, and receptor binding domain (RBD) interactions, were 19 and 10 nM respectively. Thus KIM-1 is an alternative receptor to ACE2 for SARS-CoV-2. KIM-1 targeted therapeutics may prevent and/or treat COVID-19.