Molecular characterization of Rhodeus uyekii tripartite motif protein 1 (TRIM1) involved in IFN-γ/LPS-induced NF-κB signaling

The extracellular matrix protein EFEMP2 is involved in the response to VHSV infection in the olive flounder Paralichthys olivaceus

The EGF-containing fibulin-like extracellular matrix protein 2 (EFEMP2) is involved in connective tissue development, elastic fiber formation, and tumor growth. In this study, we characterized the cDNA of EFEMP2 (PoEFEMP2), a member of the fibulin family of ECM proteins, in the olive flounder Paralichthys olivaceus. The coding region of PoEFEMP2 encodes a protein that contains six calcium-binding EGF-like (EGF-CA) domains and four complement Clr-like EGF-like (cEGF) domains. PoEFEMP2 shows 67.51-96.77 % similarities to orthologs in a variety of fish species. PoEFEMP2 mRNA was detected in all tissues examined; the highest levels of PoEFEMP2 mRNA expression were observed in the heart, testis, ovary and muscle. The PoEFEMP2 mRNA level increases during early development. In addition, the PoEFEMP2 mRNA level increased at 3 h post-infection (hpi) and decreased from 6 to 48 hpi in flounder Hirame natural embryo (HINAE) cells infected with viral hemorrhagic septicemia virus (VHSV). Disruption of PoEFEMP2 using the clustered regularly interspaced short palindromic repeats/CRISPR-associated-9 (CRISPR/Cas9) system resulted in a significant upregulation of VHSV G mRNA levels and immune-related genes expression in knockout cells. These findings implicate PoEFEMP2 in antiviral responses in P. olivaceus.

The Molecular and Function Characterization of Porcine MID2

Midline2 (MID2/TRIM1) is a member of the tripartite motif-containing (TRIM) family, which is involved in a wide range of cellular processes. However, fundamental studies on porcine MID2 (pMID2) are still lacking. In this study, we identified and characterized the full length MID2 gene of pig (Sus scrofa). The sequence alignment analysis results showed that pMID2 had an N-terminal RING zinc-finger domain, BBC domain, and C-terminal COS box, FN3 motif, and PRY-SPRY domain that were conserved and similar to those of other vertebrates. Furthermore, pMID2 had the highest expression levels in porcine lung and spleen. Serial deletion and site-directed mutagenesis showed that the putative nuclear factor-κB (NF-κB) binding site may be an essential transcription factor for regulating the transcription expression of pMID2. Furthermore, the immunofluorescence assay indicated that pMID2 presented in the cell membrane and cytoplasm. To further study the functions of pMID2, we identified and determined its potential ability to perceive poly (I:C) and IFN-α stimulation. Stimulation experiments showed pMID2 enhanced poly (I:C)-/IFN-α-induced JAK-STAT signaling pathway, indicating that pMID2 might participate in the immune responses. In conclusion, we systematically and comprehensively analyzed the characterizations and functions of pMID2, which provide valuable information to explore the pMID2 functions in innate immunity. Our findings not only enrich the current knowledge of MID2 in IFN signaling regulation but also offer the basis for future research of pig MID2 gene.

Characterization of TRIM16, a member of the fish-specific finTRIM family, in olive flounder Paralichthys olivaceus

Tripartite motif-containing (TRIM) proteins are conserved throughout the metazoan kingdom, and the TRIM subset finTRIM is highly diversified in fish. We isolated TRIM16 cDNA, a member of the finTRIM family, from the olive flounder Paralichthys olivaceus (PoTRIM16). PoTRIM16 contained a 1,725-bp coding sequence encoding a 574-amino acid polypeptide, which in turn contained a really interesting new gene (RING) finger domain, B-box-type zinc finger (B-BOX), nuclease SbcCD subunit C (SbcC), structural maintenance of chromosome (SMC prok B), and stonustoxin (SNTX) subunit alpha (SPRY-PRY-SNTX). Multiple alignment of related sequences revealed that PoTRIM16 showed 86.63-97.40% identity with fish orthologues, and a phylogenetic tree was constructed of vertebrates. PoTRIM16 mRNA was detected in all tissues examined; levels were highest in the eye and ovary. PoTRIM16 mRNA expression was investigated during early development. Under VHSV infection, PoTRIM16 mRNA was downregulated in the liver of P. olivaceus. This is the first study to characterize fish-specific finTRIM in P. olivaceus, which may play a role in the immune response against virus infection.

Tripartite motif 52 (TRIM52) promotes proliferation, migration, and regulation of colon cancer cells associated with the NF-κB signaling pathway

BACKGROUND

With the advancement of early detection and treatment, the incidence of colon cancer (CC) has declined steadily worldwide; however, the mortality remains unacceptably high. Tripartite motif 52 (TRIM52) is a member of the family of highly conserved RBCC (a RING-finger, two B-boxes, and a predicted alpha-helical Coiled-Coil domain were linked to the N-terminal region in sequence) proteins with more than 70 isoforms, which plays an important role in tumorigenesis through different signaling pathways. How it regulates the development of CC remains unknown.

METHODS

Western blot was used to reveal that TRIM52 protein expression is up-regulated in CC cells. The Analysis of The Cancer Genome Atlas (TCGA) database was used to find the different expressions of TRIM52 between colon cancer tissues and normal colonic epithelial tissues. Cell proliferation assays, migration and invasion assays, and apoptosis were used to verify the changes in cell function after knockdown or overexpression of TRIM52 in CC cells. After that, the key proteins of the nuclear factor (NF)-κB signaling pathway were validated by western blot to explore the role of TRIM52 in the NF-κB signaling pathway. Finally, in order to explore the potential sites of TRIM52, LPS and PDTC were employed to activate and block the NF-κB signaling pathway, and the key proteins of the NF-κB signaling pathway were validated by western blot.

RESULTS

TGCA database revealed that TRIM52 expression was elevated in CC tissues and correlated with prognosis. It was verified that TRIM52 promoted the proliferation, migration, and invasion of CC cells, and inhibited cell apoptosis. Most of the tripartite motif proteins (TRIMs) have ubiquitin ligase activity related to their highly conserved RING structure. Detection of the key proteins of the NF-κB signaling pathway in CC cells revealed that TRIM52 activated the NF-κB signaling pathway.

CONCLUSIONS

We confirmed that TRIM52 promotes proliferation, migration, and invasion while inhibiting apoptosis of CC cells. The regulatory effect of TRIM52 on CC cells is related to the activation of the NF-κB signaling pathway. As TRIM52 acted as an upstream stimulator, stimulating the transfer of P65 into the nucleus to activate the NF-κB signaling pathway, it may provide a potential target for prognosis prediction and treatment of CC.

FTR67, a member of the fish-specific finTRIM family, triggers IFN pathway and against spring viremia of carp virus

Tripartite motif (TRIM) proteins have attracted particular research interest because of their multiple functions in the antiviral innate immune response. TRIM proteins perform different functions during virus infection, some play a role in inhibiting while others play a role in promoting. In this study, we described a species-specific TRIM gene named ftr67. Analysis of tissue distribution showed that ftr67 was mainly expressed in the gill and liver in five examined tissues of zebrafish. The phylogenic analysis showed that ftr67 was closest to the grass carp TRIM67. Overexpression of ftr67 resulted in a significantly decreased SVCV entry and impaired SVCV replication in FHM cells. Furthermore, overexpression of ftr67 could significantly induce the upregulation of molecular sensor RIG-I, IRF3/7, IFN and ISGs. In addition, RING domain of ftr67 was a required part essential for the antiviral effect. In summary, our results demonstrated that the important role of ftr67 in regulating SVCV infection, which offers a potential target for development of anti-SVCV therapies.

Fish species-specific TRIM gene FTRCA1 negatively regulates interferon response through attenuating IRF7 transcription

In mammals and fish, emerging evidence highlights that TRIM family members play important roles in the interferon (IFN) antiviral immune response. Fish TRIM family has undergone an unprecedented expansion leading to generation of finTRIM subfamily, which is exclusively specific to fish. Our recent results have shown that FTRCA1 (finTRIM C. auratus 1) is likely a fish species-specific finTRIM member in crucian carp C. auratus and acts as a negative modulator to downregulate fish IFN response by autophage-lysosomal degradation of protein kinase TBK1. In the present study, we found that FTRCA1 also impedes the activation of crucian carp IFN promoter by IRF7 but not by IRF3. Mechanistically, FTRCA1 attenuates IRF7 transcription levels likely due to enhanced decay of IRF7 mRNA, leading to reduced IRF7 protein levels and subsequently reduced fish IFN expression. E3 ligase activity is required for FTRCA1 to negatively regulate IRF7-mediated IFN response, because ligase-inactive mutants and the RING-deleted mutant of FTRCA1 lose the ability to block the activation of crucian carp IFN promoter by IRF7. These results together indicate that FTRCA1 is a multifaceted modulator to target different signaling factors for shaping fish IFN response in crucian carp.

Molecular cloning and preliminary functional analysis of six RING-between-ring (RBR) genes in grass carp (Ctenopharyngodon idellus)

Ubiquitination is a post-translational modification of proteins that is widely present in eukaryotic cells. There is increasing evidence that ubiquitinated proteins play crucial roles in the immune response process. In mammals, RING-between-RING (RBR) proteins play a key role in regulating immune signaling as the important E3 ubiquitin ligases during ubiquitination. However, the function of RBR in fish is still unclear. In the present study, six RBR genes (RNF19A, RNF19B, RNF144AA, RNF144AB, RNF144B and RNF217) of grass carp (Ctenopharyngodon idellus) were cloned and characterized. Similar to mammals, all six members of RBR family contained RING, in-between-ring (IBR) and transmembrane (TM) domains. These genes were constitutively expressed in all studied tissues, but the relative expression level differed. Following grass carp reovirus(GCRV) infection, the expression of six RBR genes in liver, gill, spleen and intestine significantly altered. Additionally, their expression in Ctenopharyngodon idellus kidney (CIK) cells was significantly increased after GCRV infection. And deficiency of RNF144B in CIK with small interference RNA (siRNA) up-regulated polyinosinic:polycytidylic acid poly(I:C))-induced inflammatory cytokines production, including IFN-I, TNF-α, IL-6, and transcription factor IRF3, which demonstrated that RNF144B was a negative regulator of inflammatory cytokines. Our results suggested that the RBR might play a vital role in regulating immune signaling and laid the foundation for the further mechanism research of RBR in fishes.

FTRCA1, a Species-Specific Member of finTRIM Family, Negatively Regulates Fish IFN Response through Autophage-Lysosomal Degradation of TBK1

In mammals, tripartite motif (TRIM) proteins have emerged as pivotal players endowed with, directly, antiviral effects and, indirectly, modulatory capacity of the innate immune response. An unprecedented expansion of TRIM family has occurred in fish; however, the functional role of fish TRIM family members remains largely unknown. In this study, we identify a species-specific TRIM gene from crucian carp Carassius auratus, named FTRCA1, phylogenetically similar to the members of finTRIM, a subfamily of TRIM exclusively in teleost fish. FTRCA1 is induced by IFN and IFN stimuli as a typical IFN-stimulated gene. Overexpression of FTRCA1 negatively regulates IFN antiviral response by inhibition of IRF3 phosphorylation; consistently, knockdown of FTRCA1 results in enhanced levels of IRF3 phosphorylation and also IFN expression following poly(I:C) transfection. Whereas FTRCA1 is associated with several pivotal signaling molecules of RIG-I-like receptor pathway, its association with TBK1 results in autophage-lysosomal degradation of TBK1, thus abrogating the downstream IFN induction. Interestingly, FTRCA1 is phosphorylated by TBK1, but this phosphorylation is not required for downregulation of TBK1 protein. Transfection assays indicate that FTRCA1 is likely an E3 ligase with the requirement of RING finger domain, and deletion of N-terminal RING domain or mutation of seven conservative sites abolishes the negative regulatory function of FTRCA1. Collectively, these results illuminate a novel finTRIM-mediated innate immune modulatory pathway, thus providing insights into species-specific regulation of fish IFN response.