The 2',5'-oligoadenylate (2-5A) synthetase (OAS)-RNase L system is a robust interferon (IFN)-inducible antiviral pathway that contributes to the survival of higher vertebrates against both RNA and DNA viruses. Accordingly, viruses have acquired and evolved a multitude of mechanisms to antagonize OAS-RNase L. During the past 5 years, we established roles for RNase L in IFN signaling, inflammasome activation and autophagy. Yet there remains much to be learned about how RNase L suppresses viral infections, how viruses evade these enzymes, and how the host recovers from RNase L activation. In particular, our knowledge of how RNase L is regulated through its protein kinase-like domain, how RNase L mediates cell death from ADAR1 deficiency, how the RNase L inhibitor (ABCE1 aka RLI) functions, and how RNase L activates the NLRP3 inflammasome is still fragmentary. Therefore, the proposed continuation of this project will systematically investigate the major outstanding questions about this critically important host antiviral pathway. The unifying theme of this application concerns how RNase L function is regulated beyond its activation by 2-5A, in particular through its protein kinase-like (PKL) domain, to control viral infections and inflammation. Our findings lead to the hypothesis that the OAS-RNase L system is an integral part of the host immune system that must be tightly regulated to eliminate viruses while also limiting its harmful pro-inflammatory effects.
Our specific aims are: (1) To study the impact of the RNase L PKL domain on cells and viruses we will evaluate recently identified small molecule inhibitors, enhancers and their derivatives on RNase L activity, determine the ability of the small molecules to control viral infections, and investigate effects of the RNase L inhibitors on cell death caused by ADAR1 deficiency. (2) To investigate how the ATP-binding cassette member, ABCE1 (RLI), limits RNase L activity, we will determine precisely how ABCE1 interacts with RNase L to inhibit its activity, establish how the host cells ramps up RNase L activity during viral infections by caspase-mediated cleavage of ABCE1, and determine the ability of ABCE1 to counteract cellular toxicity of double stranded RNA by inhibiting RNase L. (3) To probe the mechanism of NLRP3 inflammasome activation by RNase L, we will identify and characterize RNase L-cleaved viral RNA activators of the NLRP3 inflammasome, determine effects of the small RNA cleavage products on inflammasome activation, and determine the impact of RNase L inhibitor drugs on viral mediated inflammation in vivo. Viral infections remain a serious threat to human health worldwide. Despite viral countermeasures, the OAS-RNase L system has a major impact against many types of pathogenic viruses. These studies emphasize how central and important it is to regulate RNase L in order to mediate the balance between antiviral activity and cell death. It is believed that a better understanding of the viral and host factors that regulate RNase L activity may eventually lead to novel and improved therapeutic approaches for treating established and emerging viral infections in the human population.

Public Health Relevance

The OAS-RNase L system is a frontline host defense against pathogenic viral infections that contributes to the survival of higher vertebrates. However, OAS-RNase L must be tightly regulated to eliminate viruses while also limiting its harmful pro-inflammatory effects in the host. These studies emphasize how central and important it is to regulate RNase L in order to mediate the balance between antiviral activity and cell death.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI135922-35
Application #
10005110
Study Section
Virology - B Study Section (VIRB)
Program Officer
Liu, Qian
Project Start
2017-09-25
Project End
2022-08-31
Budget Start
2020-09-01
Budget End
2021-08-31
Support Year
35
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Cleveland Clinic Lerner
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
135781701
City
Cleveland
State
OH
Country
United States
Zip Code
44195
Tang, Wei; Wallace, Tiffany A; Yi, Ming et al. (2018) IFNL4-?G Allele Is Associated with an Interferon Signature in Tumors and Survival of African-American Men with Prostate Cancer. Clin Cancer Res 24:5471-5481
Drappier, Melissa; Jha, Babal Kant; Stone, Sasha et al. (2018) A novel mechanism of RNase L inhibition: Theiler's virus L* protein prevents 2-5A from binding to RNase L. PLoS Pathog 14:e1006989