Grouper TRAF3 inhibits nodavirus infection by regulating the STING-mediated antiviral signaling pathway.

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are major signal transducers for the TNF and interleukin-1/Toll-like receptor superfamilies that transduce signals from various immune receptors. To investigate the interaction of TRAF3 and other proteins in signaling pathways and to identify its antiviral function in teleosts, we cloned and characterized a TRAF3 homolog from orange-spotted grouper (Epinephelus coioides) (EcTRAF3). The open reading frame of EcTRAF3 consists of 1767 base pairs encoding a 588 amino acid protein, and the predicted molecular mass is 66.71 kDa EcTRAF3 shares 99.83% identity with TRAF3 of Epinephelus lanceolatus. Expression analysis revealed that EcTRAF3 was broadly distributed in examined tissues and was up-regulated under polyinosinic-polycytidylic acid and red-spotted grouper nervous necrosis virus (RGNNV) stimulation in vivo. EcTRAF3 was identified as a cytosolic protein based on fluorescence microscopy analysis. Overexpression of EcTRAF3 inhibited RGNNV replication in grouper spleen cells, and it interacted with the coat protein of RGNNV. Overexpression of EcTRAF3 also induced the activation of interferon ß (IFN-ß), IFN-stimulated response element (ISRE), and nuclear factor-κB (NF-κB). EcTRAF3 co-transfected with Stimulator of Interferon Genes (STING) of grouper (EcSTING) induced a significantly higher level of IFN-ß promoter activity. Moreover, EcTRAF3 interacted with EcSTING, implying that EcTRAF3 may function as an enhancer in EcSTING-mediated signaling. Taken together, our results suggest that EcTRAF3 negatively regulates the RGNNV-induced cellular antiviral response and plays an important role in the immune response system of fish.

Applications of upconversion nanoparticles in cellular optogenetics.

Upconversion-mediated optogenetics is an emerging powerful technique to remotely control and manipulate the deep-tissue protein functions and signaling pathway activation. This technique uses lanthanide upconversion nanoparticles (UCNPs) as light transducers and through near-infrared light to indirectly activate the traditional optogenetic proteins. With the merits of high spatiotemporal resolution and minimal invasiveness, this technique enables cell-type specific manipulation of cellular activities in deep tissues as well as in living animals. In this review, we introduce the latest development of optogenetic modules and UCNPs, with emphasis on the integration of UCNPs with cellular optogenetics and their biomedical applications on the control of neural/brain activity, cancer therapy and cardiac optogenetics in vivo. Furthermore, we analyze the current developed strategies to optimize and advance the upconversion-mediated optogenetics and discuss the remaining challenges of its further applications in biomedical study and clinical translational research. STATEMENT OF SIGNIFICANCE: Optogenetics harnesses photoactivatable proteins to optically stimulate and control intracellular activities. UCNPs-mediated NIR-activatable optogenetics uses lanthanide upconversion nanoparticles (UCNPs) as light transducers and utilizes near-infrared (NIR) light to indirectly activate the traditional optogenetic proteins. The integration of UCNPs with cellular optogenetics has showed great promise in biomedical applications in regulating neural/brain activity, cancer therapy and cardiac optogenetics in vivo. The evolution and optimization of functional UCNPs and the discovery and engineering of novel optogenetic modules would both contribute to the advance of such unique hybrid technology, which may lead to discoveries in biomedical research and provide new treatments for human diseases.

Grouper TRAF5 exerts negative regulation on antiviral immune response against iridovirus.

Tumor necrosis factor receptor-associated factor 5 (TRAF5) is an intracellular protein that binds to the cytoplasmic portion of tumor necrosis factor receptors and mediates the activation of downstream nuclear factor-kappa B (NF-κB), interferon regulatory factor 3, and mitogen activated protein kinase signaling pathways. Compared with other TRAF proteins, TRAF5 is largely unknown in teleosts. In the present study, a TRAF5 homologue (HgTRAF5) from the hybrid grouper (Epinephelus fuscoguttatus♂ × Epinephelus lanceolatus♀) was cloned and characterized. The open reading frame of HgTRAF5 consists of 1743 nucleotides encoding a 581 amino acid protein with a predicted molecular mass of 64.90 kDa. Similar to its mammalian counterpart, HgTRAF5 contains an N-terminal RING finger domain, a zinc finger domain, and a C-terminal TRAF domain, including a coiled-coil domain and a MATH domain. HgTRAF5 shares 99.83% identity with giant grouper (Epinephelus lanceolatus) TRAF5. Quantitative real-time PCR analysis indicated that HgTRAF5 mRNA was broadly expressed in all examined tissues. The expression of HgTRAF5 increased after Singapore grouper iridovirus (SGIV) infection in grouper spleen (GS) cells. Intracellular localization analysis demonstrated that the full-length HgTRAF5 protein mainly distributed in the cytoplasm. HgTRAF5 overexpression also promoted SGIV replication during viral infection in vitro. HgTRAF5 significantly promoted the activities of interferon-ß, interferon-sensitive response element, and NF-κB. Taken together, these results are important for a better understanding of the function of TRAF5 in fish and reveal its involvement in the host response to immune challenge by SGIV.