DNA-induced 2′3′-cGAMP enhances haplotype-specific human STING cleavage by dengue protease

Chan-I Su,Yu-Ting Kao,Chao-Chen Chang,Yao Chang,Tzong-Shiann Ho,H Sunny Sun,Yi-Ling Lin,Michael M C Lai,Yu-Huei Liu,Chia-Yi Yu

doi:10.1073/pnas.1922243117

Abstract

The cytosolic DNA sensor cGMP-AMP synthase (cGAS) synthesizes the noncanonical cyclic dinucleotide 2'3'-cGAMP to activate the adaptor protein stimulator of IFN genes (STING), thus awakening host immunity in response to DNA pathogen infection. However, dengue virus (DENV), an RNA virus without a DNA stage in its life cycle, also manipulates cGAS-STING-mediated innate immunity by proteolytic degradation of STING. Here, we found that the sensitivity of STING to DENV protease varied with different human STING haplotypes. Exogenous DNA further enhanced DENV protease's ability to interact and cleave protease-sensitive STING. DNA-enhanced STING cleavage was reduced in cGAS-knockdown cells and triggered by the cGAS product 2'3'-cGAMP. The source of DNA may not be endogenous mitochondrial DNA but rather exogenous reactivated viral DNA. Cells producing 2'3'-cGAMP by overexpressing cGAS or with DNA virus reactivation enhanced STING cleavage in neighboring cells harboring DENV protease. DENV infection reduced host innate immunity in cells with the protease-sensitive STING haplotype, whose homozygote genotype frequency was found significantly reduced in Taiwanese people with dengue fever. Therefore, the human STING genetic background and DNA pathogen coinfection may be the missing links contributing to DENV pathogenesis.

Highlights

Complex and, contributes to stimulator of IFN genes (STING) cleavage [11]
We cloned each of the three STINGs with the HARQ [7] backbone (SI Appendix, Fig. S1) and cotransfected them with Dengue virus (DENV) protease NS2B3 to test its sensitivity to DENV protease
While the STINGs were cleaved with different efficiency, the DENV protease-mediated cleavage of mitofusin 2 (MFN2) [19] is not altered (SI Appendix, Fig. S2), suggesting the haplotype of STING, rather than the protease activity of NS2B3, affects the STING cleavage here

Summary

Introduction

Complex and, contributes to STING cleavage [11]. The sole DENV protease NS2B3 explicitly cleaves human STING but not its murine ortholog, which suggests different DENV restriction factors among different species [6, 7]. The failure of DENV protease in cleaving nonhuman primate STINGs derived from presumed DENV natural reservoirs [8] indicates the DENVinduced STING cleavage might be the factor contributing to species-specific pathogenesis of DENV infection. DENV protease cleaves human stimulator of IFN genes (STING) [6,7,8] to subvert innate immunity, whether the human STING variants affect this cleavage event or contribute to DENV pathogenesis remains to be uncovered. Dengue virus (DENV) antagonizes the DNA sensing cGAS-STING pathway to subvert innate immunity, but how DENV proteasemediated human STING cleavage contributes to DENV pathogenesis remains obscure. The cleavage of a DENV protease-sensitive STING can be further enhanced by coculture with neighboring cells producing 2′3′-cGAMP, either by DNA transfection of cGAS or by reactivating Epstein–Barr virus from latent infection. The genetic background of host STING and bystander coinfection of pathogens triggering 2′3′cGAMP production may be the missing link between STING cleavage and DENV pathogenesis

Methods

Results

Conclusion