Identification of the non-specific cytotoxic cell receptor protein 1 (NCCRP1) in regenerating axolotl limbs

Novel C-type lectin mediated non-specific cytotoxic cells killing activity through NCCRP-1 in nile tilapia (Oreochromis niloticus)

Non-specific cytotoxic cells (NCCs) are vital immune cells involved in teleost's non-specific immunity. As a receptor molecule on the NCCs' surface, the non-specific cytotoxic cell receptor protein 1 (NCCRP-1) is known to play a crucial role in mediating their activity. Nevertheless, there have been limited studies on the signal molecule that transmits signals via NCCRP-1. In this study, a yeast two-hybrid (Y2H) library of tilapia liver and head kidney was constructed and subsequently screened with the bait vector NCCRP-1 of Oreochromis niloticus (On-NCCRP-1) to obtain a C-type lectin (On-CTL) with an interacting protein sequence. Consequently, the full-length sequence of On-CTL was cloned and analyzed. The expression analysis revealed that On-CTL is highly expressed in the liver and is widely distributed in other tissues. Furthermore, On-CTL expression was significantly up-regulated in the brain, intestine, and head kidney following a challenge with Streptococcus agalactiae. A point-to-point Y2H method was also used to confirm the binding between On-NCCRP-1 and On-CTL. The recombinant On-CTL (rOn-CTL) protein was purified. In vitro experiments demonstrated that rOn-CTL can up-regulate the expression of killer effector molecules in NCCs via its interaction with On-NCCRP-1. Moreover, activation of NCCs by rOn-CTL resulted in a remarkable enhancement in their ability to eliminate fathead minnow cells, indicating that rOn-CTL effectively modulates the killing activity of NCCs through the NCC receptor molecule On-NCCRP-1. These findings significantly contribute to our comprehension of the regulatory mechanisms governing NCC activity, paving the way for future research in this field.

Expression changes of non-specific cytotoxic cell receptor (NCCRP1) and proliferation and migration of NCCs post-Nocardia seriolae infection in Northern Snakehead

Non-specific cytotoxic cells (NCCs) are essential to the cytotoxic cell-mediated immune response in teleost. The fish non-specific cytotoxic cell receptor protein 1 (NCCRP1) plays an important role as a membrane protein in the recognition of target cells and the activation of NCC. However, the roles of fish NCCs during pathogen infection require comprehensive studies. In this study, the coding sequence of northern snakehead (Channa argus) nccrp1 (Canccrp1) was cloned. Canccrp1 contains an open reading frame of 690 bp, encoding a peptide of 229 amino acids with a conserved F-box-associated domain (FBA) and proline-rich motifs (PRMs). Transcriptional expression analysis revealed that the constitutive expression of Canccrp1 was higher in the immune-related organs, such as liver, kidneys, and spleen. Moreover, mRNA and protein expression of Canccrp1 gradually increased in the spleen at 1-6 days post infection (dpi) with Nocardia seriolae, in addition to reaching peak expression in both the kidneys and liver at 2 dpi. A polyclonal antibody prepared against recombinant CaNCCRP1 effectively labeled NCCs in peripheral blood and different tissues. Then, immunofluorescence (IF) staining showed that the number of NCCs was significantly increased and showed a scattered distribution in the early stages of N. seriolae infection (2 and 4 dpi) before the forming of granulomas. At the late stages of N. seriolae infection (6 dpi), more NCCs migrated to preexisting granulomas, showing significant coaccumulation with N. seriolae. All these results clearly indicate the expression changes of CaNCCRP1, and the number and localization changes of NCCs post-N. seriolae infection, implying potential roles for fish NCCs in the antimicrobial infection process in fish.

Biological characterisation, expression and functional analysis of non-specific cytotoxic cell receptor protein 1 in Nile tilapia (Oreochromis niloticus)

Non-specific cytotoxic cell receptor protein 1 (NCCRP-1) plays a role in recognition of target cell and activation of non-specific cytotoxic cell (NCC). In this study, the full length of Nile tilapia NCCRP-1 (On-NCCRP-1) was cloned. cDNA is composed of 1045 bp with a 90 bp of 5'-Untranslated Regions (UTR), 702 bp open reading frame (ORF) and 253 bp 3'-UTR, encoding 233 amino acids (GenBank accession no: MF162296). The On-NCCRP-1 genomic sequence is 4471 bp in length and contains six exons and five introns. On-NCCRP-1 possesses some inherent conservative domains, such as proline-rich motifs, antigen recognition site, and F-box-related domain. Subcellular localisation and Western blot analysis indicated that On-NCCRP-1 is located in the cell membrane. The transcript of On-NCCRP-1 was detected in all the examined tissues of healthy Nile tilapia by using qRT-PCR, with the highest expression levels in the liver. Following Streptococcus agalactiae challenged in vivo, the On-NCCRP-1 expression was up-regulated significantly in brain, intestines, head kidney and spleen. In the in vitro analysis, the On-NCCRP-1 expression in NCCs was up-regulated significantly from 8 h to 12 h after LPS challenge, and up-regulated significantly at 12 h after challenged with polyI:C. After NCCs were challenged with inactivated S. agalactiae, the On-NCCRP-1 expression was down-regulated significantly after 24 h. NF-кB pathway was strongly activated by the over-expression of On-NCCRP-1 in HEK-293T cells. These results indicate that On-NCCRP-1, as a membrane surface receptor of NCCs, may play an important role in immune response to pathogenic infection in Nile tilapia.

Identification of NCCRP1 as an epigenetically regulated tumor suppressor and biomarker for malignant phenotypes of squamous cell carcinoma of the esophagus

The poor prognosis and increasing incidence of esophageal squamous cell carcinoma (ESCC) highlight the need for identification of novel ESCC-associated molecular events to improve the diagnosis, and treatment of this disease. Non-specific cytotoxic cell receptor protein 1 (NCCRP1) was reported to be abundantly expressed in human squamous epithelium and to be involved in cell proliferation; however, the role of NCCRP1 in ESCC remains unclear. To elucidate the oncological roles of NCCRP1 in ESCC, NCCRP1 expression, DNA methylation, and copy numbers were analyzed in ESCC cell lines. Nine ESCC cell lines demonstrated different NCCRP1 mRNA expression levels and all exhibited hypermethylation of the NCCRP1 promoter, but no copy number loss. Additionally, NCCRP1 expression was determined in 213 surgically resected esophageal tissue samples. NCCRP1 mRNA expression levels were reduced in ESCC tissues compared with corresponding non-cancerous adjacent tissues in 204 (95.8%) patients. Patients in the low NCCRP1 expression group tended to have a higher recurrence rate and a shorter overall survival time compared with those in the high NCCRP1 expression group. Additionally, multivariate analysis revealed that low NCCRP1 expression was an independent prognostic factor (hazard ratio, 1.75; 95% confidence interval, 1.08-2.87; P=0.022). The findings of the current study indicate that NCCRP1 acts as a putative tumor suppressor that is inactivated through promoter hypermethylation, and serves as a promising biomarker to predict postoperative prognosis in ESCC.

Molecular cloning of NCCRP-1 gene from orange-spotted grouper (Epinephelus coioides) and characterization of NCCRP-1(+) cells post Cryptocaryon irritans infection

Nonspecific cytotoxic cells (NCCs) are an important cytotoxic cell population in the innate teleost immune system. The receptor designated "NCC receptor protein 1" (NCCRP-1) has been reported to be involved in the recognition and activation of NCCs. In this study, the full-length cDNA of Epinephelus coioides NCCRP-1 (ecnccrp-1) was cloned. The open reading frame (ORF) of ecnccrp-1 is 699 bp, encoding a 232 amino acid protein that includes proline-rich motifs at the N-terminus and is related to the F-box associated family. Although a bioinformatics analysis showed that EcNCCRP-1 had no signal peptide or transmembrane helices, a polyclonal antibody directed against recombinant EcNCCRP-1 efficiently labeled a membrane protein in the head kidney, detected with Western blot analysis, which indicated that the protein localized to the cell surface. RT-PCR showed that the constitutive expression of ecnccrp-1 was higher in the lymphoid organs, such as the trunk kidney, spleen, head kidney, and thymus, and lower in brain, heart, fat, liver, muscle, and skin. After infection with Cryptocaryon irritans, the transcription of ecnccrp-1 was analyzed at the infected sites (skin and gills) and in the systemic immune organs (head kidney and spleen). At the infected sites, especially the skin, ecnccrp-1 expression was upregulated at 6h post infection, reaching peak expression on day 3 post the primary infection. However, the expression patterns differed in the systemic immune organs. In the spleen, ecnccrp-1 was gradually increased in the early infection period and decreased sharply on day 3 post the primary infection, whereas in the head kidney, the transcription of ecnccrp-1 was depressed during almost the whole course of infection. An immunohistochemical analysis showed that EcNCCRP-1(+) cells accumulated at the sites of infection with C. irritans. These results suggested that NCCs were involved in the process of C. irritans infection in E. coioides.

Teleost T and NK cell immunity

The main function of the immune system is to maintain the organism's homeostasis when invaded by foreign material or organisms. Prior to successful elimination of the invader it is crucial to distinguish self from non-self. Most pathogens and altered cells can be recognized by immune cells through expressed pathogen- or danger-associated molecular patterns (PAMPS or DAMPS, respectively), through non-self (e.g. allogenic or xenogenic cells) or missing major histocompatibility (MHC) class I molecules (some virus-infected target cells), and by presenting foreign non-self peptides of intracellular (through MHC class I-e.g. virus-infected target cells) or extracellular (through MHC class II-e.g. from bacteria) origin. In order to eliminate invaders directly or by destroying their ability to replicate (e.g. virus-infected cells) specialized immune cells of the innate and adaptive responses appeared during evolution. The first line of defence is represented by the evolutionarily ancient macrophages and natural killer (NK) cells. These innate mechanisms are well developed in bony fish. Two types of NK cell homologues have been described in fish: non-specific cytotoxic cells and NK-like cells. Adaptive cell-mediated cytotoxicity (CMC) requires key molecules expressed on cytotoxic T lymphocytes (CTLs) and target cells. CTLs kill host cells harbouring intracellular pathogens by binding of their T cell receptor (TCR) and its co-receptor CD8 to a complex of MHC class I and bound peptide on the infected host cell. Alternatively, extracellular antigens are taken up by professional antigen presenting cells such as macrophages, dendritic cells and B cells to process those antigens and present the resulting peptides in association with MHC class II to CD4(+) T helper cells. During recent years, genes encoding MHC class I and II, TCR and its co-receptors CD8 and CD4 have been cloned in several fish species and antibodies have been developed to study protein expression in morphological and functional contexts. Functional assays for innate and adaptive lymphocyte responses have been developed in only a few fish species. This review summarizes and discusses recent results and developments in the field of T and NK cell responses with focus on economically important and experimental model fish species in the context of vaccination.

Characterization of non-specific cytotoxic cell receptor protein 1: a new member of the lectin-type subfamily of F-box proteins

Our previous microarray study showed that the non-specific cytotoxic cell receptor protein 1 (Nccrp1) transcript is significantly upregulated in the gastric mucosa of carbonic anhydrase IX (CA IX)-deficient (Car9^−/−) mice. In this paper, we aimed to characterize human NCCRP1 and to elucidate its relationship to CA IX. Recombinant NCCRP1 protein was expressed in Escherichia coli, and a novel polyclonal antiserum was raised against the purified full-length protein. Immunocytochemistry showed that NCCRP1 is expressed intracellularly, even though it has previously been described as a transmembrane protein. Using bioinformatic analyses, we identified orthologs of NCCRP1 in 35 vertebrate genomes, and up to five paralogs per genome. These paralogs are FBXO genes whose protein products are components of the E3 ubiquitin ligase complexes. NCCRP1 proteins have no signal peptides or transmembrane domains. NCCRP1 has mainly been studied in fish and was thought to be responsible for the cytolytic function of nonspecific cytotoxic cells (NCCs). Our analyses showed that in humans, NCCRP1 mRNA is expressed in tissues containing squamous epithelium, whereas it shows a more ubiquitous tissue expression pattern in mice. Neither human nor mouse NCCRP1 expression is specific to immune tissues. Silencing CA9 using siRNAs did not affect NCCRP1 levels, indicating that its expression is not directly regulated by CA9. Interestingly, silencing NCCRP1 caused a statistically significant decrease in the growth of HeLa cells. These studies provide ample evidence that the current name, “non-specific cytotoxic cell receptor protein 1,” is not appropriate. We therefore propose that the gene name be changed to FBXO50.

The yeast two hybrid system in a screen for proteins interacting with axolotl (Ambystoma mexicanum) Msx1 during early limb regeneration

Urodele amphibians are exceptional in their ability to regenerate complex body structures such as limbs. Limb regeneration depends on a process called dedifferentiation. Under an inductive wound epidermis terminally differentiated cells transform to pluripotent progenitor cells that coordinately proliferate and eventually redifferentiate to form the new appendage. Recent studies have developed molecular models integrating a set of genes that might have important functions in the control of regenerative cellular plasticity. Among them is Msx1, which induced dedifferentiation in mammalian myotubes in vitro. Herein, we screened for interaction partners of axolotl Msx1 using a yeast two hybrid system. A two hybrid cDNA library of 5-day-old wound epidermis and underlying tissue containing more than 2×10⁶ cDNAs was constructed and used in the screen. 34 resulting cDNA clones were isolated and sequenced. We then compared sequences of the isolated clones to annotated EST contigs of the Salamander EST database (BLASTn) to identify presumptive orthologs. We subsequently searched all no-hit clone sequences against non redundant NCBI sequence databases using BLASTx. It is the first time, that the yeast two hybrid system was adapted to the axolotl animal model and successfully used in a screen for proteins interacting with Msx1 in the context of amphibian limb regeneration.

Pathological features of olfactory neuroblastoma in an axolotl (Ambystoma mexicanum)

A one-year-old, female Mexican axolotl (Ambystoma mexicanum) had a rough-surfaced, polypoid, pink tumor mass of approximately 10 mm in diameter in the oral cavity. Histologically, the tumor extended from the ethmoturbinate region and into the oral cavity and had replaced some of the maxillary bone tissue. The tumor mass was composed of a lobular architecture of small round-shaped tumor cells with occasional Flexner-Wintersteiner-like rosette formation. There were no metastatic lesions in the other organs. Immunohistochemically, the tumor cells were partly positive for several neural markers (class III beta-tubulin, S-100 protein, and doublecortin) and intensely positive for an epithelial marker (cytokeratin AE1/AE3). These results suggest that the present tumor originated from neuroectodermal tissue. Considering the location and histological and immunohistochemical features of the tumor, a diagnosis of olfactory neuroblastoma was made.

Resection of a large intra-abdominal tumor in the Mexican axolotl: a case report

OBJECTIVE

This case report describes the surgical removal of an intra-abdominal tumor from a Mexican axolotl (Ambystoma mexicanum). The animal was admitted with left abdominal swelling that had increased over 4 months.

METHODS

Surgical removal was performed under general anesthesia with MS222 under an operating microscope. Exploratory laparotomy was performed through 2.5 dorsocranial skin incision in the left flank, followed by subcutaneous dissection.

RESULTS

The tumor involved the spleen, was adjacent to the descending colon, and supplied by vessels from the spleen, stomach, and colon. The mass was removed by clamping and transecting the spleen and the peritoneum was closed with a continuous suture pattern, while abdominal muscles and skin were closed in layers. After a total duration time of anesthesia of 90 minutes the animal was kept in prophylactic antibiotic baths. Tissue sections revealed characteristics of both lymphangiosarcoma and lymphosarcoma with an appearance typical for a malignant tumor.

CONCLUSIONS

Abdominal surgery was performed in an axolotl and the surgical wound healed without complication.

The gene structure and expression of the non-specific cytotoxic cell receptor protein (NCCRP-1) in Atlantic cod (Gadus morhua L.)

The non-specific cell receptor protein (NCCRP-1) serves an important function in target cell recognition and activation of non-specific cytotoxic cells in teleosts. Atlantic cod NCCRP-1 was identified in a suppression-subtractive cDNA library and NCCRP-1 from Atlantic salmon, rainbow trout, Japanese medaka and fathead minnow was found deposited in the GenBank as EST sequences. The predicted amino acid sequences of these receptors contain the characteristic functional domains representing NCCRP-1, and phylogenetic analyses support the identification of five NCCRP-1 orthologues. Cod NCCRP-1 is shorter and has a different intron/exon organization from the common carp and channel catfish counterparts, but shows high extent of conservation in NCCRP-1 signature motives. Quantitative real-time PCR analyses showed that the gene expression of cod NCCRP-1 was higher in the lymphoid organs, head kidney (90-fold) and spleen (30-fold), compared to the organ with lowest expression. NCCRP-1 gene expression was not induced by in vitro treatment of head kidney cells with polyinosinic polycytidylic acid (poly I:C) or lipopolysaccharide (LPS), or by in vivo injections with poly I:C or formalin killed Vibrio anguillarum. These results show that the cod NCCRP-1 gene is differentially expressed in organs, and that gene expression is not induced by the tested treatments.