SARM suppresses TRIF, TRAF3, and IRF3/7 mediated antiviral signaling in large yellow croaker Larimichthys crocea
Jia Xi Zhang, Ying Li, Jun Chun Tang, Kai Qing Li, Juan Juan Shen, Chang Liu, Yong Jiang, Ziping Zhang, Yi Lei Wang, Pengfei Zou
Abstract
As a TIR domain-containing molecular, sterile α-and armadillo motif-containing protein (SARM) acts as an adaptor in Toll-like receptor (TLR) signaling, and also plays important roles in mediating apoptosis and neuronal injury. In the present study, the ortholog of SARM , named as Lc-SARM , was cloned and identified in large yellow croaker ( Larimichthys crocea ). The full-length ORF of Lc-SARM consists of 2,154 bp, encoding a protein of 717 amino acids (aa), which is comprised of an N-terminal ARM domain, two SAM domains, and a C-terminal TIR domain. Confocal microscopy revealed that Lc -SARM was mainly distributed in the cytoplasm, and the mRNA expression level of Lc-SARM was broadly distributed in all the detected organs/tissues, with the highest expression level found in the brain. The expression patterns of Lc-SARM could be induced in response to poly I:C, LPS, PGN stimulations, and Pseudomonas plecoglossicida infection. Notably, although the overexpression of Lc -SARM could significantly induce NF-κB, IRF3, IRF7, and type I IFN promoter activation, whereas the co-expression of Lc- SARM with Lc- TRIF, Lc -TRAF3, Lc -IRF3, or Lc -IRF7 significantly down-regulated the induction of NF-κB, IRF3, IRF7, or type I IFN promoter activation, and suppressed the antiviral effects as well as the downstream antiviral-related genes expression compared to the only overexpression of Lc -TRIF, Lc -TRAF3, Lc -IRF3, or Lc -IRF7. Co-immunoprecipitation (Co-IP) assays also demonstrated that Lc- SARM interacts separately with Lc -TRIF, Lc -TRAF3, Lc -IRF3, and Lc -IRF7. It is thus collectively suggested that Lc -SARM functions as a negative regulator in Lc -TRIF, Lc -TRAF3, and Lc -IRF3/7 involved antiviral signaling.