The innate immune system is the first line of defense against microbial and viral infections. A failure to elicit the early innate immune response leads to systemic infections. A significant number of human viruses, including Influenza, Hepatitis C, Dengue, West Nile, Respiratory Syncytial, Reovirus, and Ebola are recognized by the innate immunity receptor RIG-I. The overall goal of this proposal is to understand how RIG-I (Retinoic Acid-inducible Gene-I), a cytoplasmic receptor discriminates normal, cellular from viral RNAs to stimulate a host response. A major goal of our collaborative research studies has been to understand the thermodynamic, kinetic, and structural mechanisms by which RIG-I recognizes atypical pathogen associated molecular pattern (PAMP) feature in RNAs. Our crystal structure of RIG-I bound to blunt-ended dsRNA and an ATP analog established a new paradigm for RIG-I activation. The goal of this proposal is to rigorously test the RIG-I activation model using carefully designed biochemical, kinetic, and structural studies. Our preliminary results demonstrate that RIG-I is regulated in multiple ways and RNA binding affinity is not the only criterion for PAMP selection. With a unique collection of purified protein, RNA reagents, we will employ complementary biochemical, biophysical, structural, and cell based approaches to 1) understand the basis of PAMP versus non-PAMP recognition of RNA by RIG-I;2) characterize RIG-I ATPase activity and its role in RIG-I activation;and 3) understand the mechanism of RIG-I signaling. The outcomes are better understanding of self versus non-self recognition and RIG-I evasion mechanism, which can lead to the development of broad-spectrum antivirals, anti-inflammatory therapeutics and RNA-based gene silencing agents.

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The innate immune system acts as the first line of defense against pathogenic infection to stimulate the host's response. RIG-I is an important receptor of the innate immune system and plays a critical role in discriminating between viral and cellular RNA in the cytoplasm. In this proposal, we aim to systematically assess and refine the current paradigm for RIG-I activation

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Macromolecular Structure and Function B Study Section (MSFB)
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Sakalian, Michael
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Rutgers University
Schools of Arts and Sciences
New Brunswick
United States
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Valdivieso-Torres, Leonardo; Sarangi, Anindita; Whidby, Jillian et al. (2016) Role of Cysteines in Stabilizing the Randomized Receptor Binding Domains within Feline Leukemia Virus Envelope Proteins. J Virol 90:2971-80
Ramanathan, Anand; Devarkar, Swapnil C; Jiang, Fuguo et al. (2016) The autoinhibitory CARD2-Hel2i Interface of RIG-I governs RNA selection. Nucleic Acids Res 44:896-909
Devarkar, Swapnil C; Wang, Chen; Miller, Matthew T et al. (2016) Structural basis for m7G recognition and 2'-O-methyl discrimination in capped RNAs by the innate immune receptor RIG-I. Proc Natl Acad Sci U S A 113:596-601
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