The widespread emergence of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically eroded the efficacy of current β-lactam antibiotics and created an urgent need for new treatment options. We report an S. aureus phenotypic screening strategy involving chemical suppression of the growth inhibitory consequences of depleting late-stage wall teichoic acid biosynthesis. This enabled us to identify early-stage pathway-specific inhibitors of wall teichoic acid biosynthesis predicted to be chemically synergistic with β-lactams. We demonstrated by genetic and biochemical means that each of the new chemical series discovered, herein named tarocin A and tarocin B, inhibited the first step in wall teichoic acid biosynthesis (TarO). Tarocins do not have intrinsic bioactivity but rather demonstrated potent bactericidal synergy in combination with broad-spectrum β-lactam antibiotics against diverse clinical isolates of methicillin-resistant staphylococci as well as robust efficacy in a murine infection model of MRSA. Tarocins and other inhibitors of wall teichoic acid biosynthesis may provide a rational strategy to develop Gram-positive bactericidal β-lactam combination agents active against methicillin-resistant staphylococci.

Rapid, reliable recognition and detection of bacteria from an authentic specimen have been gained increasing interests in the past decades. Various materials have been designed and prepared for implementation of bacterial recognition and treatment in the artificial systems. However, in the complicated physiological condition, the macrophages always compromise the outcomes of bacterial detection and/or treatment. In this work, we demonstrated the vancomycin-modified mesoporous silica nanoparticles (MSNs is a subset of Van) for efficiently targeting and killing gram-positive bacteria over macrophage-like cells. Owing to the specific hydrogen bonding interactions of vancomycin toward the terminal d-alanyl-d-alanine moieties of gram-positive bacteria, the MSNs is a subset of Van exhibited enhanced recognition for gram-positive bacteria due to the multivalent hydrogen binding effect. Furthermore, the fluorescent molecules (FITC) were covalently decorated inside of mesopores of MSNs for tracking and visualizing the MSNs is a subset of Van during the detection/treatment processes. Upon incubation of FITC decorated MSNs with bacteria (i.e., S. aureus and E. coli as gram-positive and gram-negative bacteria, respectively) or macrophage-like cells (Raw 264.7), the fluorescence signals in S. aureus were 2-4 times higher than that in E. coli and no detectable fluorescence signals were observed in Raw 264.7 cells under the same condition. Finally, the MSNs is a subset of Van showed unambiguous antibacterial efficacy without decrease in cell viability of macrophage-like cells. This new strategy opens a new door for specific detection and treatment of pathogenic bacteria with minimized side effects.

Notch signaling affects many developmental and cellular processes and has been implicated in congenital disorders, stroke, and numerous cancers. The Notch receptor binds its ligands Delta and Serrate and is able to discriminate between them in different contexts. However, the specific domains in Notch responsible for this selectivity are poorly defined. Through genetic screens in Drosophila, we isolated a mutation, Notchjigsaw, that affects Serrate- but not Delta-dependent signaling. Notchjigsaw carries a missense mutation in epidermal growth factor repeat-8 (EGFr-8) and is defective in Serrate binding. A homologous point mutation in mammalian Notch2 also exhibits defects in signaling of a mammalian Serrate homolog, Jagged1. Hence, an evolutionarily conserved valine in EGFr-8 is essential for ligand selectivity and provides a molecular handle to study numerous Notch-dependent signaling events.

Antibiotic drug resistance among hospital and community acquired methicillin resistant Staphylococcus aureus (MRSA) has dramatically eroded the efficacy of current therapeutics. We describe a chemical genetic strategy using antisense interference to broadly identify new drug targets that potentiate the effects of existing antibiotics against both etiological classes of MRSA infection. Further, we describe the resulting chemical genetic interaction networks and highlight the prominent and overlapping target sets that restore MRSA susceptibility to penicillin, cephalosporins, and carbapenems. Pharmacological validation of this approach is the potent synergy between a known inhibitor to a member of this genetic potentiation network (GlmS) and a broad set of β-lactam antibiotics against methicillin resistant Staphylococci. Developing drug-like leads to these targets may serve as rational and effective combination agents when paired with existing β-lactam antibiotics to restore their efficacy against MRSA.

Material stiffness has been shown to have potent effects on bacterial attachment and biofilm formation, but the mechanism is still unknown. In this study, response to material stiffness by Escherichia coli during attachment was investigated with biofilm assays and cell tracking using the Automated Contour-base Tracking for in Vitro Environments (ACTIVE) computational algorithm. By comparing the movement of E. coli cells attached on poly(dimethylsiloxane) (PDMS) surfaces of different Young's moduli (0.1 and 2.6 MPa, prepared by controlling the degree of cross-linking) using ACTIVE, attached cells on stiff surfaces were found more motile during early stage biofilm formation than those on soft surfaces. To investigate if motility is important to bacterial response to material stiffness, we compared E. coli RP437 and its isogenic mutants of flagellar motor (motB) and synthesis of flagella (fliC) and type I fimbriae (fimA) for attachment on 0.1 and 2.6 MPa PDMS surfaces. The motB mutant exhibited defects in response to PDMS stiffness (based on cell counting and tracking with ACTIVE), which was recovered by complementing the motB gene. Unlike motB results, mutants of fliC and fimA did not show significant defects on both face-up and face-down surfaces. Collectively, these findings suggest that E. coli cells can actively respond to material stiffness during biofilm formation, and motB is involved in this response.

Voltage-gated K+ channels are localized to juxtaparanodal regions of myelinated axons. To begin to understand the role of normal compact myelin in this localization, we examined mKv1.1 and mKv1.2 expression in the dysmyelinating mouse mutants shiverer and Trembler. In neonatal wild-type and shiverer mice, the focal localization of both proteins in axon fiber tracts is similar, suggesting that cues other than mature myelin can direct initial K+ channel localization in shiverer mutants. In contrast, K+ channel localization is altered in hypomyelinated axonal fiber tracts of adult mutants, suggesting that abnormal myelination leads to channel redistribution. In shiverer adult, K+ channel expression is up-regulated in both axons and glia, as revealed by immunocytochemistry, RNase protection, and in situ hybridization studies. This up-regulation of K+ channels in hypomyelinated axon tracts may reflect a compensatory reorganization of ionic currents, allowing impulse conduction to occur in these dysmyelinating mouse mutants.

ObjectiveFollistatin-like protein 1 (FSTL1) is widely recognised as a secreted glycoprotein, but its role in modulating macrophage-related inflammation during liver fibrosis has not been documented. Herein, we aimed to characterise the roles of macrophage FSTL1 in the development of liver fibrosis.DesignExpression analysis was conducted with human liver samples obtained from 33 patients with liver fibrosis and 18 individuals without fibrosis serving as controls. Myeloid-specific FSTL1-knockout (FSTL1M-KO) mice were constructed to explore the function and mechanism of macrophage FSTL1 in 3 murine models of liver fibrosis induced by carbon tetrachloride injection, bile duct ligation or a methionine-deficient and choline-deficient diet.ResultsFSTL1 expression was significantly elevated in macrophages from fibrotic livers of both humans and mice. Myeloid-specific FSTL1 deficiency effectively attenuated the progression of liver fibrosis. In FSTL1M-KO mice, the microenvironment that developed during liver fibrosis showed relatively less inflammation, as demonstrated by attenuated infiltration of monocytes/macrophages and neutrophils and decreased expression of proinflammatory factors. FSTL1M-KO macrophages exhibited suppressed proinflammatory M1 polarisation and nuclear factor kappa B pathway activation in vivo and in vitro. Furthermore, this study showed that, through its FK domain, FSTL1 bound directly to the pyruvate kinase M2 (PKM2). Interestingly, FSTL1 promoted PKM2 phosphorylation and nuclear translocation, reduced PKM2 ubiquitination to enhance PKM2-dependent glycolysis and increased M1 polarisation. Pharmacological activation of PKM2 (DASA-58) partially countered FSTL1-mediated glycolysis and inflammation.ConclusionMacrophage FSTL1 promotes the progression of liver fibrosis by inducing M1 polarisation and inflammation based on the intracellular PKM2 reprogramming function of macrophages.

No abstract