A Cytosolic Sensor, PmDDX41, Binds Double Stranded-DNA and Triggers the Activation of an Innate Antiviral Response in the Shrimp Penaeus monodon via the STING-Dependent Signaling Pathway.

Suthinee Soponpong,Taro Kawai,Anchalee Tassanakajon,Piti Amparyup

doi:10.3389/fimmu.2019.02069

Abstract

Helicase DDX41 is a cytosolic sensor capable of detecting double-stranded DNA in mammals. However, the function of DDX41 remains poorly understood in invertebrates. In a previous study, we identified the first DDX41 sensor in the black tiger shrimp Penaeus monodon (PmDDX41) and showed that it played a role in anti-viral response. In the present study, we demonstrated that PmDDX41 was localized in the cytoplasm of shrimp hemocytes. However, PmDDX41 was localized in both the cytoplasm and nucleus of hemocytes in the presence of white spot syndrome virus (WSSV) infection or when stimulated by the nucleic acid mimics, poly(dA:dT) and poly(I:C). Similar results were observed when PmDDX41 was transfected into human embryonic kidney 293T (HEK293T) cells. Immunoprecipitation further demonstrated that PmDDX41 bound to biotin-labeled poly(dA:dT) but not poly(I:C). The overexpression of shrimp PmDDX41 and mouse stimulator of interferon gene (MmSTING) in HEK293T cells synergistically promoted IFN-β and NF-κB promoter activity via the DEADc domain. Co-immunoprecipitation (Co-IP) also confirmed that there was an interaction between PmDDX41 and STING after stimulation with poly(dA:dT) but not poly(I:C). Our study is the first to demonstrate that PmDDX41 acts as a cytosolic DNA sensor that interacts with STING via its DEADc domain to trigger the IFN-β and NF-κB signaling pathways, thus activating antiviral innate immune responses.

Highlights

The recognition of pattern recognition receptors (PRRs)-mediated pathogen-associated molecule patterns (PAMPs) is the first line of a host’s innate immune response to pathogenic infection [1]
We found that PmDDX41 and the DEADc domain could bind only to MmSTING after poly(dA:dT) stimulation but not after high molecular weight (HMW) poly(I:C) stimulation (Figure 8)
PmDDX41 was the first DNA sensor molecule to be identified in the shrimp P. monodon and contains three conserved domains; it shares high similarity with the vertebrates DEAD (Asp-Glu-Ala-Asp) box polypeptide 41 (DDX41) [17], supporting the fact that DDX41 family members have been highly conserved during the evolution of vertebrates and invertebrates with regards to innate immunity

Summary

Introduction

The recognition of pattern recognition receptors (PRRs)-mediated pathogen-associated molecule patterns (PAMPs) is the first line of a host’s innate immune response to pathogenic infection [1]. Nucleic acid recognitions have been found such as toll-like receptors (TLRs), retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) and the group of cytosolic DNA sensor molecules, including DEAD (Asp-Glu-Ala-Asp) box polypeptide 41 (DDX41) and cyclic GMP-AMP synthase (cGAS). Of these receptors, DDX41 is a newly cytosolic DNA molecule which plays a role in a variety of innate immune response and is associated with several vertebrate diseases, including acute myeloid leukemia and myelodysplastic syndrome [4]. A recent study isolated a DDX41 homolog from the orange spotted grouper Epinephelus coioides (EcDDX41) and showed that this homolog regulated mitochondrial antiviral-signaling protein (MAVS) and TBK1-induced IFN immune response [10]

Methods

Results

Conclusion