| Autor: |
Alexander-Floyd J; Department of Microbiology, University of Pennsylvaniagrid.25879.31 Perelman School of Medicine, Philadelphia, Pennsylvania, USA., Bass AR; Department of Microbiology, University of Pennsylvaniagrid.25879.31 Perelman School of Medicine, Philadelphia, Pennsylvania, USA., Harberts EM; Department of Microbial Pathogenesis, University of Maryland, School of Dentistry, Baltimore, Maryland, USA., Grubaugh D; Department of Pathobiology, University of Pennsylvaniagrid.25879.31 School of Veterinary Medicine, Philadelphia, Pennsylvania, USA., Buxbaum JD; Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York, USA.; Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York, USA., Brodsky IE; Department of Pathobiology, University of Pennsylvaniagrid.25879.31 School of Veterinary Medicine, Philadelphia, Pennsylvania, USA., Ernst RK; Department of Microbial Pathogenesis, University of Maryland, School of Dentistry, Baltimore, Maryland, USA., Shin S; Department of Microbiology, University of Pennsylvaniagrid.25879.31 Perelman School of Medicine, Philadelphia, Pennsylvania, USA. |
| Abstrakt: |
Detection of Gram-negative bacterial lipid A by the extracellular sensor, myeloid differentiation 2 (MD2)/Toll-like receptor 4 (TLR4), or the intracellular inflammasome sensors, CASP4 and CASP5, induces robust inflammatory responses. The chemical structure of lipid A, specifically its phosphorylation and acylation state, varies across and within bacterial species, potentially allowing pathogens to evade or suppress host immunity. Currently, it is not clear how distinct alterations in the phosphorylation or acylation state of lipid A affect both human TLR4 and CASP4/5 activation. Using a panel of engineered lipooligosaccharides (LOS) derived from Yersinia pestis with defined lipid A structures that vary in their acylation or phosphorylation state, we identified that differences in phosphorylation state did not affect TLR4 or CASP4/5 activation. However, the acylation state differentially impacted TLR4 and CASP4/5 activation. Specifically, all tetra-, penta-, and hexa-acylated LOS variants examined activated CASP4/5-dependent responses, whereas TLR4 responded to penta- and hexa-acylated LOS but did not respond to tetra-acylated LOS or penta-acylated LOS lacking the secondary acyl chain at the 3' position. As expected, lipid A alone was sufficient for TLR4 activation. In contrast, both core oligosaccharide and lipid A were required for robust CASP4/5 inflammasome activation in human macrophages, whereas core oligosaccharide was not required to activate mouse macrophages expressing CASP4. Our findings show that human TLR4 and CASP4/5 detect both shared and nonoverlapping LOS/lipid A structures, which enables the innate immune system to recognize a wider range of bacterial LOS/lipid A and would thereby be expected to constrain the ability of pathogens to evade innate immune detection. |
