Biology subjects

Neugebauer, U.

Publications and source records attributed to Neugebauer, U..

2 recordsLinked to original sources

bioRxiv2021

Gram-positive bacteria secrete RNA aptamers to activate human STING for IL-1β release.

Molecular mechanisms through which Gram-positive bacteria induce the canonical inflammasome are poorly understood. Here, we studied the effects of Group B streptococci (GBS) and Staphylococcus aureus (SA) on inflammasome activation in human macrophages. Dinucleotide binding small RNA aptamers released by SA and GBS were shown to trigger increased IL-1{beta} generation by inflammasomes. The stimulator of interferon genes-STING as a central mediator of innate immune responses has been identified as the key target of pathogenic RNA. Multi-lamellar lipid bodies (MLBs) produced by SA function as vehicles for the RNA aptamers. Notably, expression of RNA aptamers is controlled by an accessory gene regulator quorum sensing system of the bacteria. These findings have been translated to patients with Gram-positive sepsis showing hallmarks of MLB-RNA-mediated inflammasome activation. Together our findings may provide a new perspective for the pathogenicity of Gram-positive bacterial infection in man.

immunology↗

bioRxiv2020

Revisiting the interaction of heme with hemopexin: Recommendations for the responsible use of an emerging drug

In hemolytic disorders, erythrocyte lysis results in massive release of hemoglobin and, subsequently, toxic heme. Hemopexin is the major protective factor against heme toxicity in human blood and currently considered for therapeutic use. It has been widely accepted that hemopexin binds heme with extraordinarily high affinity in a 1:1 ratio. Here we show that hemopexin binds heme with lower affinity than previously assumed and that the interaction ratio tends to 2:1 (heme:hemopexin) or above. The heme-binding sites of hemopexin were characterized using hemopexin-derived peptide models and competitive displacement assays. In addition, in silico molecular modelling with a newly created homology model of human hemopexin allowed us to propose a recruiting mechanism by which heme consecutively binds to several histidine residues and is finally funnelled into the high-affinity binding pocket. Our findings have direct implications for the biomedical application of hemopexin and its potential administration in hemolytic disorders.

biochemistry↗