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Advances in aquatic animal RIG-I-like receptors
Bo Liang1,2,3, Jianguo Su1,2,3
1Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan 430070, China.
Abstract:
Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) sense microbial-associated molecular patterns (MAMPs) to activate the innate immune responses. RLRs in aquatic animals include RIG-I, MDA5, LGP2, mollusc RIG-I-like and MDA5-like proteins, which exhibit structural and functional diversity. RLRs data from 30 species of aquatic animals were collected for analysis. Not all species contain all the RLR members. RIG-I is absent in the orders of Perciformes, Cichliformes and Pleuronectiformes, and LGP2-like protein is absent in the class of Bivalvia. Due to the differences in species and variants, the homologous proteins have different responses to pathogens. LGP2 works as an immune homeostasis regulator to balance the immune response. The phylogenetic analysis demonstrates RIG-I and mollusc RIG-I-like present in the same evolutionary branch and appear in the early stage. RIG-I is an ancient PRR in innate antiviral immunity. The prototype of antiviral immune system has emerged in aquatic mollusc. Aquatic animal RLRs were analyzed and summarized in terms of structures, functions, and evolutions, which provide the basic information for future researches in RLRs. Base on the diversity of species and RLRs, more and in-depth studies in aquatic animal RLRs should be done.
Insights
Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are crucial for innate immunity in aquatic animals. Their diversity and evolutionary history reveal ancient antiviral defense mechanisms, particularly in mollusks.
Area of Science:
- Immunology
- Evolutionary Biology
- Aquatic Biology
Background:
- Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are key sensors of microbial-associated molecular patterns (MAMPs), initiating innate immune responses.
- Aquatic animal RLRs, including RIG-I, MDA5, LGP2, and mollusc-specific variants, display significant structural and functional diversity.
Purpose of the Study:
- To analyze the structures, functions, and evolutionary patterns of RLRs across 30 aquatic animal species.
- To understand the presence and absence of specific RLR members in different aquatic taxa.
- To investigate the evolutionary origins of innate antiviral immunity in aquatic organisms.
Main Methods:
- Data collection and analysis of RLRs from 30 aquatic animal species.
- Comparative analysis of RLR protein structures and functions.
- Phylogenetic analysis to determine evolutionary relationships and origins.
Main Results:
- Not all aquatic species possess the complete set of RLRs; RIG-I is absent in certain fish orders, and LGP2-like proteins are missing in Bivalvia.
- Homologous RLR proteins exhibit varied responses to pathogens due to species-specific differences.
- LGP2 acts as a crucial regulator of immune homeostasis.
- Phylogenetic analysis indicates RIG-I and mollusc RIG-I-like proteins share an early evolutionary branch, suggesting ancient origins of antiviral immunity in mollusks.
Conclusions:
- Aquatic animal RLRs are diverse, with varying presence across species and distinct evolutionary trajectories.
- RIG-I represents an ancient pattern recognition receptor (PRR) fundamental to innate antiviral immunity.
- The foundational elements of antiviral immune systems likely emerged early in aquatic mollusks.
- Further in-depth research on aquatic animal RLRs is warranted due to observed diversity and evolutionary insights.
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