Molecular and transcriptional insights into viperin protein from Big-belly seahorse (Hippocampus abdominalis), and its potential antiviral role.

Viperin is recognized as an antiviral protein that is stimulated by interferon, viral exposures, and other pathogenic molecules in vertebrate. In this study, a viperin homolog in the Big-belly seahorse (Hippocampus abdominalis; HaVip) was functionally characterized to determine its subcellular localization, expression pattern, and antiviral activity in vitro. The HaVip coding sequence encodes a 348 amino acid polypeptide with predicted molecular weight of 38.48 kDa. Sequence analysis revealed that HaVip comprises three main domains: the N-terminal amphipathic α-helix, a radical S-adenosyl-l-methionine (SAM) domain, and a conserved C-terminal domain. Transfected GFP-tagged HaVip protein was found to localize to the endoplasmic reticulum (ER). Overexpressed-HaVip in FHM cells was found to significantly reduce viral capsid gene expression in VHSV infection in vitro. Under normal physiological conditions, HaVip expression was ubiquitously detected in all 14 examined tissues of the seahorse, with the highest expression observed in the heart, followed by skin and blood. In vivo studies showed that HaVip was rapidly and predominantly upregulated in blood, kidney, and intestinal tissue upon poly (I:C) stimulus. LPS and Streptococus iniae challenges caused a significant increase in expression of HaVip in all the analyzed tissues. The obtained results suggest that HaVip is involved in the immune system of the seahorse, triggering antiviral and antibacterial responses, upon viral and bacterial pathogenic infections.

A comparative study of three akirin genes from big belly seahorse Hippocampus abdominalis: Molecular, transcriptional and functional characterization.

Akirins, members of the NF-κB signaling pathway, are highly conserved nuclear proteins, which regulate gene expression in many physiological processes, including immunity, myogenesis, carcinogenesis, and embryogenesis. The akirin family in teleost fish consists of two to three genes. In the present study, three akirin genes from Hippocampus abdominalis were identified from a transcriptome database and designated as HaAkirin1, HaAkirin2(1), and HaAkirin2(2). The nuclear localization of HaAkirin1 and HaAkirin2(1) was confirmed by subcellular localization analysis. In contrast, diffused localization of HaAkirin2(2) was identified in the nucleus and cytoplasm that confirmed the aberrant nature of the nuclear localization signal. Phylogenetic analysis revealed a closer relationship of HaAkirins with other known teleost akirins. All three HaAkirin transcripts were ubiquitously expressed in all examined tissues with higher expression in ovary tissue. Immune challenge with LPS, poly I:C, and Streptococcus iniae exhibited a significant increase in the expression of all three HaAkirins in kidney and liver tissues. NF-κB luciferase assays revealed that relative luciferase activity was significantly higher for all three HaAkirin genes than mock controls. These results suggest that HaAkirin genes might play a role in regulating NF-κB dependent immune gene expression and their expression could be induced by bacterial and viral pathogen recognition molecular patterns.