High-resolution crystal structure of arthropod Eiger TNF suggests a mode of receptor engagement and altered surface charge within endosomes

Molecular identification and functional analysis of a tumor necrosis factor superfamily gene from Chinese mitten crab (Eriocheir sinensis)

Tumor necrosis factor (TNF) is one of the most important cytokines involved in various biological processes in vertebrates and invertebrates. In the present study, a new member of the TNF superfamily (named EsTNFSF) was identified from the Chinese mitten crab (Eriocheir sinensis). The full-length cDNA of EsTNFSF is 2462 bp and encodes a polypeptide with 499 amino acids. The deduced EsTNFSF protein contained a transmembrane region and a conserved extracellular C-terminal TNF domain. Phylogenetic analysis indicated that EsTNFSF was closely related to other TNFSFs from crustaceans. Quantitative real-time PCR analysis showed that EsTNFSF was expressed in all the tissues examined, and the highest expression was found in the hepatopancreas. The mRNA levels of EsTNFSF in hemocytes underwent a time-dependent and variable degree of enhancement after stimulation with lipopolysaccharide, peptidoglycan, Staphylococcus aureus, and Vibrio parahaemolyticus. Functionally, EsTNFSF knockdown by siRNA suppressed the transcriptional levels of c-Jun N-terminal kinase and two antimicrobial peptides, anti-lipopolysaccharide factor and crustin. Furthermore, purified recombinant EsTNFSF protein accelerated the bacterial clearance in vivo and inhibited the growth of V. parahaemolyticus and S. aureus in vitro. The results revealed that EsTNFSF, as an inducible immune response gene, plays a crucial role in the antibacterial immune defense of E. sinensis.

Diversity-oriented synthesis of cembranoid derivatives as potential anti-inflammatory agents

Eleven novel cembranoid derivatives were designed, synthesized, and evaluated for their inflammation related activities on the basis of our isolated and previously reported anti-inflammatory marine cembranoids. In bioassay, compound 11 displayed the most promising inhibitory effects with IC₅₀ value of 1.1 μM for the TNF-α inhibitory activity. The further mechanism study of 11 on the inflammatory signaling transduction of RAW264.7 cells was also performed. This research may give an insight for the discovery of marine cembranoid derived anti-inflammatory drug leads.

Drosophila TNFRs Grindelwald and Wengen bind Eiger with different affinities and promote distinct cellular functions

The Drosophila tumour necrosis factor (TNF) ligand-receptor system consists of a unique ligand, Eiger (Egr), and two receptors, Grindelwald (Grnd) and Wengen (Wgn), and therefore provides a simple system for exploring the interplay between ligand and receptors, and the requirement for Grnd and Wgn in TNF/Egr-mediated processes. Here, we report the crystallographic structure of the extracellular domain (ECD) of Grnd in complex with Egr, a high-affinity hetero-hexameric assembly reminiscent of human TNF:TNFR complexes. We show that ectopic expression of Egr results in internalisation of Egr:Grnd complexes in vesicles, a step preceding and strictly required for Egr-induced apoptosis. We further demonstrate that Wgn binds Egr with much reduced affinity and is localised in intracellular vesicles that are distinct from those containing Egr:Grnd complexes. Altogether, our data provide insight into ligand-mediated activation of Grnd and suggest that distinct affinities of TNF ligands for their receptors promote different and non-redundant cellular functions.

The Drosophila tumour necrosis factor (TNF) system comprises a single ligand Eiger (Egr) and two receptors. The structure of Egr in complex with the extracellular domain of the receptor Grindelwald and accompanying data suggest that distinct affinities of TNF ligand for its receptors mediate non-redundant functions.

The involvement of TNF-α and TNF-β as proinflammatory cytokines in lymphocyte-mediated adaptive immunity of Nile tilapia by initiating apoptosis

Tumor necrosis factors (TNFs) are pleiotropic cytokines with important functions in homeostasis and disease pathogenesis. Recent advances have shown that TNFs are also involved in the regulation of adaptive immune responses. However, the knowledge about how TNF participates in and regulates adaptive immune response in early vertebrates is still limited. In present study, we identified two isoforms of TNF, TNF-α and TNF-β, from Nile tilapia Oreochromis niloticus (On-TNF-α and β). After analyzing the sequence characteristics, we investigated their regulatory roles in adaptive immune response of this fish species. On-TNF-α and β are evolutionarily conserved compare with their homologs from other vertebrates. Both TNFs were distributed in a wide range of tissues in O. niloticus, and with relative higher expression level in gill. After the animals were infected by Streptococcus agalactiae, mRNA levels of On-TNF-α and TNF-β in spleen lymphocytes were significantly upregulated during the primary response stage of adaptive immunity. Meanwhile, both TNF proteins in spleen lymphocytes were also dramatically elevated during the adaptive immune stage after bacterial infection. These results indicate the potential participation of On-TNF-α and TNF-β in adaptive immune response of Nile tilapia. Furthermore, On-TNF-α and β transcripts were obviously augmented, once spleen lymphocytes were activated by T cell-specific mitogen PHA. More importantly, both recombinant On-TNF-α and β could induce the apoptosis of head-kidney leukocytes of Nile tilapia. And On-TNF-β but not On-TNF-α promoted the apoptosis by activating caspase-8 in the target cells. Altogether, our study revealed that TNF-α and TNF-β participated in the lymphocyte-mediated adaptive immune response of Nile tilapia by initiating the apoptosis, and thus shed novel perspective for the regulatory mechanism of adaptive immunity in teleost.