Influenza A Virus Infection Activates NLRP3 Inflammasome through Trans-Golgi Network Dispersion.

Kannu Priya Pandey,Yan Zhou

doi:10.3390/v14010088

Abstract

The NLRP3 inflammasome consists of NLRP3, ASC, and pro-caspase-1 and is an important arm of the innate immune response against influenza A virus (IAV) infection. Upon infection, the inflammasome is activated, resulting in the production of IL-1β and IL-18, which recruits other immune cells to the site of infection. It has been suggested that in the presence of stress molecules such as nigericin, the trans-Golgi network (TGN) disperses into small puncta-like structures where NLRP3 is recruited and activated. Here, we investigated whether IAV infection could lead to TGN dispersion, whether dispersed TGN (dTGN) is responsible for NLRP3 inflammasome activation, and which viral protein is involved in this process. We showed that the IAV causes dTGN formation, which serves as one of the mechanisms of NLRP3 inflammasome activation in response to IAV infection. Furthermore, we generated a series of mutant IAVs that carry mutations in the M2 protein. We demonstrated the M2 proton channel activity, specifically His37 and Trp41 are pivotal for the dispersion of TGN, NLRP3 conformational change, and IL-1β induction. The results revealed a novel mechanism behind the activation and regulation of the NLRP3 inflammasome in IAV infection.

Highlights

Inflammation is initiated when the innate immune system recognizes invading pathogens or molecules from tissue injury through pattern recognition receptors (PRRs) including nucleotide-binding domain and leucine-rich repeat-containing proteins (NLRs) [1]
We demonstrated the M2 proton channel activity, His37 and Trp41 are pivotal for the dispersion of trans-Golgi network (TGN), NLR family pyrin domain-containing protein 3 (NLRP3) conformational change, and IL-1β induction
To find out if the influenza A virus (IAV) causes TGN dispersion, we first constructed the plasmid pFlagNLRP3-GFP, which encodes porcine NLRP3 fused with Flag tag at the N-terminus and GFP at the C-terminus (Figure 1a)

Summary

Introduction

Inflammation is initiated when the innate immune system recognizes invading pathogens or molecules from tissue injury through pattern recognition receptors (PRRs) including nucleotide-binding domain and leucine-rich repeat-containing proteins (NLRs) [1]. PRRs recognize various pathogen-associated molecular patterns (PAMPs) and dangerassociated molecular patterns (DAMPs) upon the induction of pathogens or other foreign materials [2]. Among these sensors, a member of the NLRs called the NLR family pyrin domain-containing protein 3 (NLRP3) can detect various PAMPs and DAMPs and had been extensively studied [3]. It has been widely appreciated that the activation of the inflammasome occurs in two steps: priming and activation. Signal 1 or priming includes the recognition of PAMPs leading to the transcriptional upregulation of various components of the NLRP3 inflammasome, including NLRP3, pro-caspase-1, pro-IL-1β, and pro-IL-18. Signal 2 or the activation step, which can be activated by K+

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Results