Cell-Based Screen Identifies Human Interferon-Stimulated Regulators of Listeria monocytogenes Infection.

Sofya S Perelman,Neal M Alto,Alyssa Jimenez,Marcel Mettlen,Jennifer L Eitson,Didi Chen,Michael E Abrams,John W Schoggins

doi:10.1371/journal.ppat.1006102

Sofya S Perelman, Neal M Alto + Show 6 more

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https://doi.org/10.1371/journal.ppat.1006102

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Abstract

The type I interferon (IFN) activated transcriptional response is a critical antiviral defense mechanism, yet its role in bacterial pathogenesis remains less well characterized. Using an intracellular pathogen Listeria monocytogenes (Lm) as a model bacterial pathogen, we sought to identify the roles of individual interferon-stimulated genes (ISGs) in context of bacterial infection. Previously, IFN has been implicated in both restricting and promoting Lm growth and immune stimulatory functions in vivo. Here we adapted a gain-of-function flow cytometry based approach to screen a library of more than 350 human ISGs for inhibitors and enhancers of Lm infection. We identify 6 genes, including UNC93B1, MYD88, AQP9, and TRIM14 that potently inhibit Lm infection. These inhibitors act through both transcription-mediated (MYD88) and non-transcriptional mechanisms (TRIM14). Further, we identify and characterize the human high affinity immunoglobulin receptor FcγRIa as an enhancer of Lm internalization. Our results reveal that FcγRIa promotes Lm uptake in the absence of known host Lm internalization receptors (E-cadherin and c-Met) as well as bacterial surface internalins (InlA and InlB). Additionally, FcγRIa-mediated uptake occurs independently of Lm opsonization or canonical FcγRIa signaling. Finally, we established the contribution of FcγRIa to Lm infection in phagocytic cells, thus potentially linking the IFN response to a novel bacterial uptake pathway. Together, these studies provide an experimental and conceptual basis for deciphering the role of IFN in bacterial defense and virulence at single-gene resolution.

Highlights

Mammalian cells encode numerous pattern recognition receptors (PRRs) that sense invading pathogens and initiate innate immune responses through cytokine and chemokine production [1]
We chose to clarify these aspects of IFN biology by using Listeria monocytogenes as a model pathogen as its cellular life cycle has been described in detail and it exhibits a complex relationship with the mammalian IFN response system [5]
10% of host cells were infected by Green Fluorescent Protein (GFP)-Listeria monocytogenes (Lm) at this time point

Summary

Introduction

Mammalian cells encode numerous pattern recognition receptors (PRRs) that sense invading pathogens and initiate innate immune responses through cytokine and chemokine production [1]. The type I interferon (IFN) family of cytokines serves as a first line of defense and is essential for controlling virus replication and pathogenesis. The IFN-induced antiviral response results from the transcription of hundreds of interferon-stimulated genes (ISGs), many of which inhibit different steps of the viral life cycle [2, 3]. We chose to clarify these aspects of IFN biology by using Listeria monocytogenes ( referred to as Lm) as a model pathogen as its cellular life cycle has been described in detail and it exhibits a complex relationship with the mammalian IFN response system [5]. Recent studies show that Lm stimulates the type I IFN response by secreting cyclic diadenosine monophosphate (c-di-AMP) that activates the Stimulator of Interferon Genes (STING). Activation of STING results in IRF3 phosphorylation and transcription of IFN genes [8, 9]. STING-deficient mice fail to produce IFNβ in response to Lm infection [10]

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