Pattern recognition receptors in zebrafish provide functional and evolutionary insight into innate immune signaling pathways

Abstract

Pattern recognition receptors (PRRs) and their signaling pathways have essential roles in recognizing various components of pathogens as well as damaged cells and triggering inflammatory responses that eliminate invading microorganisms and damaged cells. The zebrafish relies heavily on these primary defense mechanisms against pathogens. Here, we review the major PRR signaling pathways in the zebrafish innate immune system and compare these signaling pathways in zebrafish and humans to reveal their evolutionary relationship and better understand their innate immune defense mechanisms.

Nucleotide‐binding and oligomerization domain (NOD)‐like receptors in teleost fish: Current knowledge and future perspectives

“…The innate immune response is primarily mediated by pathogen/pattern‐recognition receptors (PRRs) that recognize the conserved pathogen‐associated molecular patterns (PAMPs) found on harmful pathogens. After PAMP recognition, host innate immune cells initiate a broad sequence of defence signalling pathways that result in the development of an inflammatory response (Akira, Uematsu, & Takeuchi, ; Caruso & Nunez, ; Geddes, Magalhaes, & Girardin, ; Li, Li, Cao, Jin, & Jin, ). PRRs comprise a series of sensors, categorized into five classes: (a) the Toll‐like receptors (TLRs), which localize to the cell surface or remain intracellular in endosomes or lysosomes; (b) the nucleotide‐binding oligomerization domain (NOD)‐like receptors (NLRs), an array of cytoplasmic receptors; (c) the retinoic acid inducible gene I (RIG‐I)‐like receptors (RLRs), a group of intracellular receptors that recognize viral pathogens; (d) the C‐type lectin (one of the most common immune lectins) receptors (CLRs) and cytosolic DNA sensors (CDSs) and (e) the cytosolic, absent in melanoma (AIM)‐like receptors (ALRs) (Kigerl, De Rivero Vaccari, Dietrich, Popovich, & Keane, ; Vajjhala, Ve, Bentham, Stacey, & Kobe, ).…”

Grass Carp Laboratory of Genetics and Physiology 2 Serves As a Negative Regulator in Retinoic Acid-Inducible Gene I- and Melanoma Differentiation-Associated Gene 5-Mediated Antiviral Signaling in Resting State and Early Stage of Grass Carp Reovirus Infection

“…Nearly all the counterparts of vertebrate PRRs and their downstream signaling components have been identified in teleost (20, 21). RLRs are evolutionarily conserved from fish to mammals (21).…”

“…Nearly all the counterparts of vertebrate PRRs and their downstream signaling components have been identified in teleost (20, 21). RLRs are evolutionarily conserved from fish to mammals (21). Generally, teleost RLRs also consist of three members: RIG-I, MDA5, and LGP2, although RIG-I is absent in some fish species (20).…”

“…Generally, teleost RLRs also consist of three members: RIG-I, MDA5, and LGP2, although RIG-I is absent in some fish species (20). So far, RLRs have been identified in many teleosts such as zebrafish ( Danio rerio ) (21–23), grass carp ( Ctenopharyngodon idella ) (24–26), rainbow trout ( Oncorhynchus mykiss ) (12), Atlantic salmon ( Salmo salar ), and Japanese flounder ( Paralichthys olivaceus ) (27). The roles of RLRs in mediating downstream signal pathways have been preliminarily studied in some fish species (28–31).…”

Studies on the effects of LPS, ß‐glucan and metabolic inhibitors on the respiratory burst and gene expression in Atlantic salmon macrophages

“…(). It may likely be other pattern recognition receptors or members of the large superfamily of scavenger receptors (Canton, Neculai, & Grinstein, ; Li, Li, Cao, Jin, & Jin, ; Seternes et al., ).…”