Abstract
Transforming growth factor-β1 (TGF-β1) has been proven to function primarily in mammalian immunobiological activity, but information regarding the immune role of TGF-β1 in teleosts is limited. In the present study, we describe the cDNA cloning and characterization of the TGF-β1 molecule in the topmouth culter. TGF-β1 is highly expressed in immune-related tissues of the culter, including the thymus, head kidney, and spleen. The recombinant culter TGF-β1 (cTGF-β1) was successfully expressed and purified in vitro, and the effects of cTGF-β1 on the mRNA expression of pro-inflammatory cytokines, such as TNF-α and IL-1β, in the absence or presence of LPS was determined in culter peripheral blood leukocytes. cTGF-β1 was found to have bipolar properties in inflammatory reactions. Additionally, to assess the immune role of teleost TGF-β1 in vivo, the expression of TGF-β1 in the culter thymus and spleen tissues induced by poly I:C were also examined. The expression of TGF-β1 was obviously up-regulated, as shown in the cell lines. However, the peak time of cTGF-β1 expression in the cell lines occurred significantly earlier than in the organic tissues under the same inducer, suggesting that the response of the teleost TGF-β1 molecule to exogenous infection depends on a more complicated signalling pathway in vivo than in vitro.
Highlights
Culter alburnus, or the topmouth culter, is widely distributed throughout large rivers, reservoirs and lakes in China
An alignment analysis showed that some structural domains that are conserved in mammals and other fish species was present in the cTGF-β1 molecule, including a characteristic RGD integrin-binding site and a RRKR cut site in the precursor region, nine cysteine residues allowing for the formation of inter-chain and intra-chain disulfide bonds, the C-terminal cysteine knot in the mature peptide, and the conserved proline and glycine residues in the mature peptide, which are the distinguishing hallmarks of the TGF superfamily (Fig. 1)
All of these results indicated that the teleost TGF-β1 molecule may be functionally similar to that of higher vertebrates
Summary
The topmouth culter (hereafter referred to as ‘culter’), is widely distributed throughout large rivers, reservoirs and lakes in China. We report for the first time the cloning of TGF-β1 from culter (cTGF-β1), followed by the expression and purification of the TGF-β1 protein in vitro.
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