Identification and characterization of a novel IκB-ε-like gene from lamprey (Lampetra japonica) with a role in immune response

Northeast Chinese lamprey (Lethenteron morii) MyD88: Identification, expression, and functional characterization

Myeloid differentiation factor 88 (MyD88) is a key adaptor of Toll-like receptors (TLR), an important pattern recognition receptor of the innate immune system. To study the origin and evolution of the vertebrate TLR signaling pathway in innate immune systems, we analyzed the biological characteristics and functions of the MyD88 gene in Northeast Chinese lamprey (Lethenteron morii) using PCR amplification, real-time PCR analysis, dual luciferase reporter gene assay, immunofluorescence assay, and other methods. Bioinformatics analysis showed that LmMyD88 has a modular structure consisting of Toll/IL-1R domain (TIR) and death domain (DD), which is typical of the MyD88 family. A phylogenetic tree showed that the homology of LmMyD88 was consistent with the phylogenetic status of lampreys. Tissue expression analysis indicated that the mRNA expression was expressed in some normal tissues of larval and adult L. morii. Real-time PCR analysis showed that the expression of LmMyD88 in tissues, such as gill and kidney, of the adult increased significantly after infection by Pseudomonas aeruginosa. Subcellular localization results showed that LmMyD88 was expressed in the nucleus, cytoplasm, and other parts. A dual luciferase reporter assay indicated that LmMyD88 activated nuclear factor kappa B downstream of the TLR signaling pathway. This study suggested that LmMyD88 might play an important role in the innate immune signal transduction process of L. morii.

Determination of the Role and Active Sites of PKC-Delta-Like from Lamprey in Innate Immunity

Protein kinase C-δ (PKC-δ) is an important protein in the immune system of higher vertebrates. Lampreys, as the most primitive vertebrates, have a uniquevariable lymphocyte receptor (VLR) immune system. PKC-δ-like is a crucial functional gene in lampreys and is highly expressed in their immune organs. In this study, lampreys were stimulated with different immunogens, and lipopolysaccharide (LPS) was found to increase the expression of PKC-δ-like. Overexpression of PKC-δ-like could also effectively activate the innate immune response. We further demonstrated that PKC-δ-like-CF, a catalytic fragment of PKC-δ-like, is responsible for activating the innate immune response, and Thr-211, which is Thr-419 of PKC-δ-like, was confirmed to be the key site affecting PKC-δ-like-CF activity. These results indicated that PKC-δ-like from lamprey may have an important role in the innate immune response.

The archaic roles of the lamprey NF-κB (lj-NF-κB) in innate immune responses

The nuclear factor-kappa B (NF-κB) is a pleiotropic transcription factor regulating the expression of genes involved in various biological processes including the immune response and inflammation. Lamprey is regarded as a key species to provide meaningful clues for understanding the evolution of immune system; nevertheless, no information about lamprey NF-κB is reported. Thus, we have characterized a NF-κB homolog in lamprey (lj-NF-κB) for the deeper understanding of the role it played in lamprey immune system. The sequence and 3D structure analyses demonstrate that lj-NF-κB contained a Rel homology domain (RHD) and seven ankyrin repeats domains (ANKs), which would exhibit functional similarities to NF-κB superfamily proteins. This hypothesis was further proved by experiments. We found that the RHD of lj-NF-κB could interact with a mammalian κB response element, translocate to the nucleus to modulate gene (IL-6, IL-1β and TNF-α) expression, and the nuclear localization signals (NLS) was essential for the nuclear translocation. Furthermore, the ANKs of lj-NF-κB are the inhibition signal for the RHD of lj-NF-κB. The present results allow us to surmise that the lj-NF-κB should play a key role in immune response of lamprey, and the function of NF-κB has been maintained during evolution.

Lamprey: a model for vertebrate evolutionary research

Lampreys belong to the superclass Cyclostomata and represent the most ancient group of vertebrates. Existing for over 360 million years, they are known as living fossils due to their many evolutionally conserved features. They are not only a keystone species for studying the origin and evolution of vertebrates, but also one of the best models for researching vertebrate embryonic development and organ differentiation. From the perspective of genetic information, the lamprey genome remains primitive compared with that of other higher vertebrates, and possesses abundant functional genes. Through scientific and technological progress, scientists have conducted in-depth studies on the nervous, endocrine, and immune systems of lampreys. Such research has significance for understanding and revealing the origin and evolution of vertebrates, and could contribute to a greater understanding of human diseases and treatments. This review presents the current progress and significance of lamprey research.