Journal Article

Aggregation of thrombin-derived C-terminal fragments as a previously undisclosed host defense mechanism

Bond, Peter J., Malmsten, Martin, Schmidtchen, Artur, Hansen, Finja C., Petrlova, Jitka, van der Plas, Mariena J. A., Huber, Roland G., Mörgelin, Matthias

2017

Overview

Effective control of endotoxins and bacteria is crucial for normal wound healing. During injury, the key enzyme thrombin is formed, leading to generation of fibrin. Here, we show that human neutrophil elastase cleaves thrombin, generating 11-kDa thrombin-derived C-terminal peptides (TCPs), which bind to and form amorphous amyloid-like aggregates with both bacterial lipopolysaccharide (LPS) and gram-negative bacteria. In silico molecular modeling using atomic resolution and coarse-grained simulations corroborates our experimental observations, altogether indicating increased aggregation through LPS-mediated intermolecular contacts between clusters of TCP molecules. Upon bacterial aggregation, recombinantly produced TCPs induce permeabilization of Escherichia coli and phagocytic uptake. TCPs of about 11 kDa are present in acute wound fluids as well as in fibrin sloughs from patients with infected wounds. We noted aggregation and colocalization of LPS with TCPs in such fibrin material, which indicates the presence of TCP-LPS aggregates under physiological conditions. Apart from identifying a function of proteolyzed thrombin and its fragments, our findings provide an interesting link between the coagulation system, innate immunity, LPS scavenging, and protein aggregation/amyloid formation.

• Publisher: National Academy of Sciences
• Subject: Agglomeration / Aggregates / aggregation / Animals / Bacteria / Bacterial corrosion / Biological Sciences / Cell Line / Clusters / Coagulation / Coarsening / Computational fluid dynamics / Computer simulation / E coli / Elastase / Endotoxins / Enzymes / Escherichia coli - immunology / Fibrin / Fluids / Fragmentation / Fragments / Gram-negative bacteria / Healing / host defense peptides / Humans / Immunity / Immunity, Innate - immunology / Immunology and Inflammation / Injuries / Innate immunity / Leukocyte Elastase - metabolism / Lipopolysaccharides / Lipopolysaccharides - immunology / Medical and Health Sciences / Medical Biotechnology / Medicin och hälsovetenskap / Medicinsk bioteknologi / Mice / Molecular modelling / Molecules / Patients / Peptide Fragments - immunology / Peptides / Phagocytes / PNAS Plus / Protein Aggregates - immunology / Protein interaction / RAW 264.7 Cells / Scavenging / Simulation / Thrombin / Thrombin - immunology / Thrombin - metabolism / Wound healing / Wounds and Injuries - immunology / Wounds and Injuries - microbiology / β-Amyloid