Abstract
Oligopeptide transporter 1 (Pept1) is located on the brush border membrane of the intestinal epithelium and plays an important role in dipeptide and tripeptide absorption from protein digestion. In this study, we cloned and characterized the cDNA sequence of Janus kinase 2 (JAK2) from Ctenopharyngodon idella. The expression patterns of JAK2 in various tissues and developmental stages were characterized by quantitative real-time PCR (qRT-PCR). The mRNA expression levels of JAK2 and Pept1 regulated by leptin in the intestine were also analyzed in vitro and in vivo. The cDNA sequence of JAK2 is 3378 bp in length, and the mRNA of JAK2 was broadly expressed in all tissues and embryonic stages of C. idella analyzed. In addition, we found that leptin regulated expression of JAK2 and Pept1 in the intestine; Pept1 expression was down-regulated by the JAK2 inhibitor AG490 in vivo and in vitro. Furthermore, luciferase experiments showed that overexpression of the JAK2 gene significantly upregulated the activity of the Pept1 5′ regulatory sequence in C. idella. In conclusion, these results may help in elucidating the regulatory effect of the leptin-mediated JAK2 pathway on intestinal Pept1 expression in C. idella and the molecular mechanism of peptide transport by the intestinal transporter Pept1 in fishes.
Highlights
Oligopeptide transporter 1 is an oligopeptide transporter located in the brush border membrane sac of enteric epithelial cells and plays a key role in the absorption of intestinal peptides (Pan et al, 1997; Chen et al, 2002)
The results of phylogenetic analysis showed that C. idella Janus kinase 2 (JAK2) is subordinate to the branch of fish, which is consistent with traditional taxonomy (Figure 1)
Studies have shown that the JAK2 amino acid sequence of close species has high similarity (Leu et al, 2000)
Summary
Oligopeptide transporter 1 is an oligopeptide transporter located in the brush border membrane sac of enteric epithelial cells and plays a key role in the absorption of intestinal peptides (Pan et al, 1997; Chen et al, 2002). Recent studies have demonstrated that coexpression of Janus kinase 2 (JAK2) markedly increases electronic transfer of the dipeptide glycine-glycine in Xenopus oocytes expressing either Pept or Pept; JAK2 may increase Pept activity by inserting a carrier protein into the membrane of cells, revealing that JAK2 is an influential regulator of peptide transporters (Pept and Pept2) (Hosseinzadeh et al, 2013). JAK2 mediates the leptin signaling pathway through substrate phosphorylation as well as in the form of a signaling complex as a scaffolding/adaptor protein (Jiang et al, 2008). A previous study showed that the leptin receptor activates JAK2 kinase in hematopoietic cell lines (White, 1996). The leptin receptor mediates intracellular signals via a connected JAK2 tyrosine kinase (Dunn et al, 2005)
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