Au, V. B. | bioRxiv Science

bioRxiv2020

LAG3 is a Central Regulator of NK Cell Cytokine Production

Natural killer (NK) cells are innate effectors, which play a crucial role in controlling viral infections. Administration of IFN- has shown promising results as a therapeutic, controlling HIV, and chronic viral hepatitis. However the downstream mechanisms by which IFN- mediates its anti-viral effects is largely unknown. In this investigation, we evaluated the impact of IFN- on peripheral blood NK cells from healthy donors. High dimensional flow cytometry analysis of NK cell surface receptors following exposure to IFN- showed an increased expression of the check point inhibitor LAG3. Further characterization revealed that LAG3 was expressed in a subset of NK cells with high expression of activation and maturation markers. Assessment of metabolic pathways showed that LAG3+ NK cells had enhanced rates of glycolysis and glycolytic capacity, suggesting that it is a primed effector subset with enhanced glucose metabolism. Inhibition of LAG3 on NK cells using antibody in vitro resulted in a profound increase in secretion of cytokines IFN-{gamma}, TNF-, MIP-1 and MIP-1{beta}, without affecting the cytotoxic activity. Taken together, these results showed that LAG3 is a negative regulator of cytokine production by mature NK cells.

immunology↗

bioRxiv2018

DPP9 is an endogenous and direct inhibitor of the NLRP1 inflammasome that guards against human auto-inflammatory diseases

The inflammasome is a critical immune complex that activates IL-1 driven inflammation in response to pathogen- and danger-associated signals. Nod-like receptor protein-1 (NLRP1) is a widely expressed inflammasome sensor. Inherited gain-of-function mutations in NLRP1 cause a spectrum of human Mendelian diseases, including systemic autoimmunity and skin cancer susceptibility. However, its endogenous regulation and its cognate ligands are still unknown. Here we apply a proteomics screen to identify dipeptidyl dipeptidase, DPP9 as a novel interacting partner and a specific endogenous inhibitor of NLRP1 inflammasome in diverse primary cell types from human and mice. DPP9 inhibition via small molecule drugs, targeted mutations in its catalytic site and CRISPR/Cas9-mediated genetic deletion potently and specifically activate the NLRP1 inflammasome leading to pyroptosis and IL-1 processing via ASC and caspase-1. Mechanistically, DPP9 maintains NLRP1 in its monomeric, inactive state by binding to the auto-cleaving FIIND domain. NLRP1-FIIND is a self-sufficient DPP9 binding module and its disruption by a single missense mutation abrogates DPP9 binding and explains the aberrant inflammasome activation in NAIAD patients with arthritis and dyskeratosis. These findings uncover a unique peptidase enzyme-based mechanism of inflammasome regulation, and suggest that the DPP9-NLRP1 complex could be broadly involved in human inflammatory disorders.

immunology↗