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IFNγ binding to extracellular matrix prevents fatal systemic toxicity.

ABSTRACT: Interferon-γ (IFNγ) is an important mediator of cellular immune responses, but high systemic levels of this cytokine are associated with immunopathology. IFNγ binds to its receptor (IFNγR) and to extracellular matrix (ECM) via four positively charged C-terminal amino acids (KRKR), the ECM-binding domain (EBD). Across evolution, IFNγ is not well conserved, but the EBD is highly conserved, suggesting a critical function. Here, we show that IFNγ lacking the EBD (IFNγ^ΔKRKR) does not bind to ECM but still binds to the IFNγR and retains bioactivity. Overexpression of IFNγ^ΔKRKR in tumors reduced local ECM binding, increased systemic levels and induced sickness behavior, weight loss and toxicity. To analyze the function of the EBD during infection, we generated IFNγ^ΔKRKR mice lacking the EBD by using CRISPR-Cas9. Infection with lymphocytic choriomeningitis virus resulted in higher systemic IFNγ^ΔKRKR levels, enhanced sickness behavior, weight loss and fatal toxicity. We conclude that local retention of IFNγ is a pivotal mechanism to protect the organism from systemic toxicity during prolonged immune stimulation.

SUBMITTER: Kemna J

PROVIDER: S-EPMC9977683 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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IFNγ binding to extracellular matrix prevents fatal systemic toxicity.

Kemna Josephine J Gout Evelyne E Daniau Leon L Lao Jessica J Weißert Kristoffer K Ammann Sandra S Kühn Ralf R Richter Matthias M Molenda Christine C Sporbert Anje A Zocholl Dario D Klopfleisch Robert R Schütz Anja A Lortat-Jacob Hugues H Aichele Peter P Aichele Peter P Kammertoens Thomas T Blankenstein Thomas T

Nature immunology 20230202 3

Interferon-γ (IFNγ) is an important mediator of cellular immune responses, but high systemic levels of this cytokine are associated with immunopathology. IFNγ binds to its receptor (IFNγR) and to extracellular matrix (ECM) via four positively charged C-terminal amino acids (KRKR), the ECM-binding domain (EBD). Across evolution, IFNγ is not well conserved, but the EBD is highly conserved, suggesting a critical function. Here, we show that IFNγ lacking the EBD (IFNγ<sup>ΔKRKR</sup>) does not bind ...[more]

PMID: 36732425

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Project description:We developed a new approach that couples Southwestern blotting and mass spectrometry to discover proteins that bind extracellular DNA (eDNA) in bacterial biofilms. Using Staphylococcus aureus as a model pathogen, we identified proteins with known DNA-binding activity and uncovered a series of lipoproteins with previously unrecognized DNA-binding activity. We demonstrated that expression of these lipoproteins results in an eDNA-dependent biofilm enhancement. Additionally, we found that while deletion of lipoproteins had a minimal impact on biofilm accumulation, these lipoprotein mutations increased biofilm porosity, suggesting that lipoproteins and their associated interactions contribute to biofilm structure. For one of the lipoproteins, SaeP, we showed that the biofilm phenotype requires the lipoprotein to be anchored to the outside of the cellular membrane, and we further showed that increased SaeP expression correlates with more retention of high-molecular-weight DNA on the bacterial cell surface. SaeP is a known auxiliary protein of the SaeRS system, and we also demonstrated that the levels of SaeP correlate with nuclease production, which can further impact biofilm development. It has been reported that S. aureus biofilms are stabilized by positively charged cytoplasmic proteins that are released into the extracellular environment, where they make favorable electrostatic interactions with the negatively charged cell surface and eDNA. In this work we extend this electrostatic net model to include secreted eDNA-binding proteins and membrane-attached lipoproteins that can function as anchor points between eDNA in the biofilm matrix and the bacterial cell surface.IMPORTANCE Many bacteria are capable of forming biofilms encased in a matrix of self-produced extracellular polymeric substances (EPS) that protects them from chemotherapies and the host defenses. As a result of these inherent resistance mechanisms, bacterial biofilms are extremely difficult to eradicate and are associated with chronic wounds, orthopedic and surgical wound infections, and invasive infections, such as infective endocarditis and osteomyelitis. It is therefore important to understand the nature of the interactions between the bacterial cell surface and EPS that stabilize biofilms. Extracellular DNA (eDNA) has been recognized as an EPS constituent for many bacterial species and has been shown to be important in promoting biofilm formation. Using Staphylococcus aureus biofilms, we show that membrane-attached lipoproteins can interact with the eDNA in the biofilm matrix and promote biofilm formation, which suggests that lipoproteins are potential targets for novel therapies aimed at disrupting bacterial biofilms.

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IFNγ binding to extracellular matrix prevents fatal systemic toxicity.

Publications

IFNγ binding to extracellular matrix prevents fatal systemic toxicity.

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