RIP3 Associates with RIP1, TRIF, MAVS, and Also IRF3/7 in Host Innate Immune Signaling in Large Yellow Croaker Larimichthys crocea.

Pengfei Zou,Yilei Wang,Ying Li,Yingjia Shen,Kaiqing Li,Ziping Zhang

doi:10.3390/antibiotics10101199

Abstract

Receptor-interacting protein 3 (RIP3) has been demonstrated to be a key regulator not only in cell death pathways including apoptosis and necroptosis but also in inflammation and host immune responses. In this study, a RIP3 ortholog named Lc-RIP3 is identified in large yellow croaker (Larimichthys crocea). The open reading frame (ORF) of Lc-RIP3 is 1524 bp long and encodes a protein of 507 amino acids (aa). The deduced Lc-RIP3 protein has an N-terminal kinase domain and a C-terminal RHIM domain, and the genome organization of Lc-RIP3 is conserved in teleosts with 12 exons and 11 introns but is different from that in mammals, which comprises 10 exons and 9 introns. Confocal microscopy revealed that Lc-RIP3 is a cytosolic protein. The expression analysis at the mRNA level indicated that Lc-RIP3 is ubiquitously distributed in various tissues/organs, and could be up-regulated under poly I:C, LPS, PGN, and Pseudomonas plecoglossicida stimulation in vivo. Notably, Lc-RIP3 could induce NF-κB but not IRF3 activation. In addition, Lc-RIP3 co-expression with Lc-TRIF, Lc-MAVS, or Lc-IRF3 significantly abolishes the activation of NF-κB but enhances the induction of IRF3 activity. Moreover, NF-κB activity could be up-regulated when Lc-RIP3 is co-expressed with Lc-RIP1 or Lc-IRF7. These results collectively indicate that Lc-RIP3 acts as an important regulator in host innate immune signaling in teleosts.

Highlights

Teleosts have evolved both innate and adaptive immune systems to provide protection against pathogen invasion and tissue damage through a variety of defense responses including the induction of interferons (IFNs), inflammatory cytokines, chemokines, and the activation of cell death pathways [1,2,3]
The innate immunity has been demonstrated as the first line in the host immune defense, which is initiated by the recognition of pathogenassociated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) through a series of receptors termed pattern recognition receptors (PRRs) including toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma 2 (AIM2)-like receptors (ALRs), which activate the host immune response through an interaction with the downstream signaling molecules [4,5]
Further studies have demonstrated that Receptor-interacting protein 3 (RIP3) acts as a key regulator in necroptosis in which RIP3 could interact with RIP1 through their RIP homotypic interaction motif (RHIM) domains, leading to the phosphorylation of the downstream pseudokinase named mixed lineage kinase domain-like protein (MLKL) and triggering necroptosis [6,7,8,11]

Summary

Introduction

Teleosts have evolved both innate and adaptive immune systems to provide protection against pathogen invasion and tissue damage through a variety of defense responses including the induction of interferons (IFNs), inflammatory cytokines, chemokines, and the activation of cell death pathways [1,2,3]. The innate immunity has been demonstrated as the first line in the host immune defense, which is initiated by the recognition of pathogenassociated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) through a series of receptors termed pattern recognition receptors (PRRs) including toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma 2 (AIM2)-like receptors (ALRs), which activate the host immune response through an interaction with the downstream signaling molecules [4,5]. RIP homotypic interaction motif (RHIM) domain, and is one of the key molecules that has been demonstrated to play important roles in cell death pathways and inflammatory responses in the PRR-mediated signaling cascade [6,7,8]. RIP3 is involved in the activation of the NOD-like receptor protein 3 (NLRP3)-dependent inflammasome complex and interleukin-1β (IL-1β) inflammatory responses [7,13]

Methods

Results

Discussion

Conclusion