Stomatin-like protein 2 of turbot Scopthalmus maximus: Gene cloning, expression profiling and immunoregulatory properties

A review of soluble factors and receptors involved in fish skin immunity: The tip of the iceberg

The immune system of fish possesses soluble factors, receptors, pathways and cells very similar to those of the other vertebrates' immune system. Throughout evolutionary history, the exocrine secretions of organisms have accumulated a large reservoir of soluble factors that serve to protect organisms from microbial pathogens that could disrupt mucosal barrier homeostasis. In parallel, a diverse set of recognition molecules have been discovered that alert the organism to the presence of pathogens. The known functions of both the soluble factors and receptors mentioned above encompass critical aspects of host defense, such as pathogen binding and neutralization, opsonization, or modulation of inflammation if present. The molecules and receptors cooperate and are able to initiate the most appropriate immune response in an attempt to eliminate pathogens before host infection can begin. Furthermore, these recognition molecules, working in coordination with soluble defence factors, collaboratively erect a robust and perfectly coordinated defence system with complementary specificity, activity and tissue distribution. This intricate network constitutes an immensely effective defence mechanism for fish. In this context, the present review focuses on some of the main soluble factors and recognition molecules studied in the last decade in the skin mucosa of teleost fish. However, knowledge of these molecules is still very limited in all teleosts. Therefore, further studies are suggested throughout the review that would help to better understand the functions in which the proteins studied are involved.

Expression and clinical significance of SLP-2 in ovarian tumors

The expression and clinical significance of stomatin-like protein 2 (SLP-2) in ovarian tumors were investigated. A total of 280 cases of ovarian tissue specimens preserved from inpatients after surgical treatments in the Department of Oncology of Yidu Central Hospital of Weifang from April 2013 to May 2016 were collected, including 130 cases of malignant ovarian tumor tissue specimens (malignant tumor group), 75 cases of benign ovarian tumor tissue specimens (benign tumor group) and 75 cases of normal ovarian tissue specimens from bilateral ovariectomy for unilateral ovarian lesions (control group). Immunohistochemistry was used to detect the expression of SLP-2 protein in the three groups. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was utilized to detect the relative expression of SLP-2 mRNA in the three groups, and the relationship between SLP-2 and clinicopathological parameters of the ovarian cancer patients was analyzed. The patients with ovarian cancer were divided into the SLP-2 high-expression group and the SLP-2 low-expression group according to the median of SLP-2 relative expression. The survival of patients was analyzed using the Kaplan-Meier and Cox regression model. The results of immunohistochemistry showed that the positive expression rate of SLP-2 protein in the malignant tumor group was significantly higher than that in the benign tumor and control groups (P<0.001). The results of RT-qPCR showed that compared with the control group, the relative expression of SLP-2 mRNA in the ovarian tissues in the benign tumor group and the malignant tumor group was increased (P<0.001). The relative expression of SLP-2 mRNA in the malignant tumor group was higher than that in the benign tumor group (P<0.001). The relative expression of SLP-2 mRNA correlated with clinical stage, pathological differentiation and lymph node metastasis of the patients with ovarian cancer (P<0.05). The 5-year overall survival (OS) in the SLP-2 mRNA high expression group was significantly lower than that in the SLP-2 mRNA low expression group at 5 years (P<0.05). SLP-2 mRNA was an independent prognostic factor influencing OS of the patients (P<0.05). SLP-2 may be involved in the occurrence and development of ovarian cancer and related to the clinical stage, pathological differentiation and lymph node metastasis of the patients with ovarian cancer, which may also play a role in promoting the invasion and metastasis processes of ovarian cancer. Therefore, SLP-2 is expected to be an effective biomarker for targeted treatment and prognosis of ovarian tumor.

Silence of Stomatin-Like Protein 2 Represses Migration and Invasion Ability of Human Liver Cancer Cells via Inhibiting the Nuclear Factor Kappa B (NF-κB) Pathway

BACKGROUND Liver cancer is the third leading cause of tumor-related deaths worldwide. Stomatin-like protein 2 (STOML2) is obviously upregulated in various tumors. In this study, we explored the potential roles and mechanisms of si-STOML2 in the migration and invasion of human hepatoma LM3 cells. MATERIAL AND METHODS The expression levels of STOML2 in tissues and cells were separately analyzed with quantitative real-time PCR (qRT-PCR) and Western blotting. The viability, migration, and invasion of cells were assessed by cell counting kit-8 (CCK-8), wound healing, and transwell analysis, respectively. The mRNA and protein levels of various factors were separately measured using qRT-PCR and Western blotting. Correlation analysis between the expression of STOML2 and the clinicopathological features of liver cancer patients was evaluated using the chi-square test. RESULTS Surprisingly, our results showed that STOML2 was upregulated in liver cancer tissue and cells, and this upregulation was linked to tumor size, histologic grade, and metastasis, but was not associated with sex, age, or TNM stage. The knockdown of STOML2 significantly repressed the viability, migration, and invasion of LM3 cells. We also observed that silencing STOML2 markedly downregulated the expression levels of matrix metalloproteinase-2 (MMP-2), MMP-9, metastatic tumor antigen 1 (MTA1), and nuclear factor kappa B (NF-κB), and upregulated levels of E-cadherin, tissue inhibitor of metalloproteinases 2 (TIMP2), and the inhibitor of kappa B (IκB). CONCLUSIONS STOML2 has a vital role in the progression of liver cancer. STOML2 silencing in LM3 cells obviously repressed the abilities of migration and invasion via suppressing the NF-κB pathway.

Characterization and expression profiling of NOD-like receptor C3 (NLRC3) in mucosal tissues of turbot (Scophthalmus maximus L.) following bacterial challenge

The mucosal surfaces are important for teleost as they are directly and continuously exposed to pathogen-rich aquatic environments. Scrutinization and recognition of the attached pathogens is the first crucial step of mucosal immunity initiation. Nucleotide oligomerization domain (NOD)-like receptors (NLRs) are a large group of intracellular pathogen recognition receptors (PRRs) which play key roles in pathogen recognition and subsequent immune signaling pathways activation. In this study, we identified two NLRC3 genes (NLRC3a and NLRC3b), a subfamily of NLRs from turbot, and profiled their expression patterns in mucosal tissues following bacterial challenge. NLRC3a transcript contains an open reading frame (ORF) of 3405 bp that encodes a putative peptide of 1134 amino acids. While NLRC3b has an ORF of 3114 bp encoding 1037 amino acids. A caspase recruitment domain (CARD) at N-terminus characterized turbot NLRC3a, while NLRC3b seems to be unique to teleost, containing a fish specific NACHT associated (FISNA) domain and an extra B30.2 (PRY/SPRY) domain at C-terminus. In addition, NLRC3a and NLRC3b were detected in all the examined tissues, with the highest expression levels in kidney and blood, respectively. After bacteria challenge, expression levels of turbot NLRC3 genes were strongly induced in intestine rather than in skin and gill, while NLRC3a had relatively higher expression level than that of NLRC3b. Taken together, NLRC3 genes found in this study were the first NLR members identified in turbot. The different expression signatures of NLRC3a and NLRC3b in mucosal tissues following two bacterial infections indicated they probably have important roles in early response to bacterial infection in the first line of host defense system.

Identification and expression analysis of toll-like receptor genes (TLR8 and TLR9) in mucosal tissues of turbot (Scophthalmus maximus L.) following bacterial challenge

Mucosal immune system is one of the most important components in the innate immunity and constitutes the front line of host defense against infection, especially for teleost, which are living in the pathogen-rich aquatic environment. The pathogen recognition receptors (PRRs), which can recognize the conserved pathogen-associated molecular patterns (PAMPs) of bacteria, are considered as one of the most important component for pathogen recognition and immune signaling pathways activation in mucosal immunity. In this regard, we sought to identify TLR8 and TLR9 in turbot (Scophthalmus maximus), as well as their mucosal expression patterns following different bacterial infection in mucosal tissues for the first time. The full-length TLR8 transcript consists of an open reading frame (ORF) of 3108 bp encoding the putative peptide of 1035 amino acids. While the TLR9 was 6730 bp long, containing a 3168 bp ORF that encodes 1055 amino acids. The phylogenetic analysis revealed both TLR8 and TLR9 showed the closest relationship to large yellow croaker. Moreover, both TLR8 and TLR9 could be detected in all examined healthy turbot tissues, with the lowest expression level in liver and a relatively moderate expression pattern in healthy mucosal tissues. Distinct expression patterns of TLR8 and TLR9 were comparatively observed in the mucosal tissues (intestine, gill and skin) following Vibrio anguillarum and Streptococcus iniae infection, suggesting their different roles for mucosal immunity. Further functional studies are needed to better characterize TLR8 and TLR9 and their family members, to better understand the ligand specificity and to identify their roles in different mucosal tissues in protecting fish from the pathogenically hostile environment.

Characterization and expression analysis of a peptidoglycan recognition protein gene, SmPGRP2 in mucosal tissues of turbot (Scophthalmus maximus L.) following bacterial challenge

Peptidoglycan recognition receptor proteins (PGRPs), a group of pattern recognition receptors (PRRs), can recognize peptidoglycan (PGN) of the bacteria cell wall and play an important role in host immune defense against pathogen infection. They are highly structurally conserved through evolution, but with different function in innate immunity between invertebrates and vertebrates. In teleost fish, several PGRPs have been characterized recently. They have both amidase activity and bactericidal activity and are involved in indirectly killing bacteria and regulating multiple signaling pathways. However, the knowledge of PGRPs in mucosal immunity of teleost fish is still limited. In this study, we identified a PGRPs gene (SmPGRP2) of turbot and investigated its expression patterns in mucosal tissues after challenge with Gram-positive bacteria Streptococcus iniae and Gram-negative bacteria Vibrio anguillarum. Phylogenetic analysis showed the strongest relationship of turbot PGRP to halibut, which was consistent with their phylogenetic relationships. In addition, SmPGRP2 was ubiquitously expressed in turbot tissues, and constitutive expression levels were higher in classical immune tissues (including liver, spleen, and head-kidney) than mucosal tissues (intestine, gill and skin). After bacterial challenge, the expression of SmPGRP2 was induced and showed a general trend of up-regulation in mucosal tissues, except in intestine following V. anguillarum infection. These different expression patterns varied depending on both pathogen and tissue type, suggesting its distinct roles in the host immune response to bacterial pathogen.

Identification and expression analysis of TLR2 in mucosal tissues of turbot (Scophthalmus maximus L.) following bacterial challenge

The pathogen recognition receptors (PRRs), which can recognize the conserved pathogen-associated molecular patterns (PAMPs) of the bacteria, play key roles in the mucosal surfaces for pathogen recognition and activation of immune signaling pathways. However, our understanding of the PRRs and their activities in mucosal surfaces in the critical early time points during pathogen infection is still limited. Towards to this end, here, we sought to identify the Toll-like receptor 2 (TLR2) in turbot as well as its expression profiles in mucosal barriers following bacterial infection in the early time points. The full-length TLR2 transcript consists of open reading frame (ORF) of 2451 bp encoding the putative peptide of 816 amino acids. The phylogenetic analysis revealed the turbot TLR2 showed the closest relationship to Paralichthys olivaceus. The TLR2 mRNA expression could be detected in all examined tissues, with the most abundant expression level in liver, and the lowest expression level in skin. In addition, TLR2 showed different expression patterns following Vibrio anguillarum and Streptococcus iniae infection, but was up-regulated following both challenge, especially post S. iniae challenge. Characterization of TLR2 will probably contribute to understanding of a number of infectious diseases and broaden the knowledge of interactions between host and pathogen, which will eventually help in the development of novel intervention strategies for farming turbot.

The mucosal expression signatures of g-type lysozyme in turbot (Scophthalmus maximus) following bacterial challenge

The mucosal surfaces constitute the first line of host defense against infection, and also serve as the dynamic interfaces that simultaneously mediate a diverse array of critical physiological processes, while in constantly contact with a wide range of pathogens. The lysozymes are considered as key components for innate immune response to pathogen infection with their strong antibacterial activities. But their activities in mucosal immune responses were always overlooked, especially for g-type lysozymes, whose expression patterns in mucosal tissues following bacterial challenge are still limited. Towards to this end, here, we characterized the g-type lysozymes, Lyg1 and Lyg2 in turbot, and determined their expression patterns in mucosal barriers following different bacterial infection. The phylogenetic analysis revealed the turbot g-type lysozyme genes showed the closest relationship to Cynoglossus semilaevis. The two lysozyme genes showed different expression patterns following challenge. Lyg2 was significantly up-regulated in mucosal tissues following Vibrio anguillarum and Streptococcus iniae challenge, while Lyg1 showed a general trend of down-regulation. The significant mucosal expression signatures of g-type lysozyme genes indicated their key roles to prevent pathogen attachment and entry in the first line of host defense system. Further functional studies should be carried out to better characterize the availability of utilization of g-type lysozyme to increase the disease resistance in the mucosal surfaces and facilitate the disease resistant breeding selection.