The role of neuromedin U during inflammatory response in the common carp

In the current study, we cloned and characterized the neuromedin U (NMU) gene from the common carp Cyprinus carpio L., and identified its participation in immune responses in the teleost. Five isoforms of the preproNMU genes were generated by alternative splicing and isolated from carp. The longest form of the carp preproNMU1 (isoform 1) cDNA was composed of 803 bp, and contained an 18 bp 5′-UTR, a 212 bp 3′-UTR and a 573 bp open reading frame, which translates into a peptide comprising 190 amino acid (aa) residues. The remaining carp preproNMU isoforms were composed of 175 (preproNMU2), 158 (preproNMU3), 150 (preproNMU4) and 133 (preproNMU5) aa residues. Isoforms 1–3 contained four processing signals (KR or RR), while isoforms 4 and 5 contained only two processing signals. High homology was demonstrated among fish and other vertebral NMU at the biologically active C-terminal region (aa position 175–182). Carp preproNMU transcript variants were identified in various tissues, and the expression pattern has been shown to change depending on feeding status. Moreover, it was shown that the expression of preproNMU3 and preproNMU5 was increased following treatment with bacterial or viral mimics. Finally, we investigated the functional aspect of carp NMU using a synthetic NMU peptide. The peptide was found to increase the expression of inflammation-related cytokine genes in intestinal cells within 1 h of treatment. In addition, the activation of phagocytic cells was also stimulated by the NMU peptide. The discovery of NMU in carp allows for a further understanding of immune regulation by biologically active substances.