Interferon-γ mediating overexpression of polymeric immunoglobulin receptor in grass carp (Ctenopharyngodon idellus) liver cells

Abstract

The polymeric immunoglobulin receptor (pIgR) have a vital function in transcytosis of polymeric immunoglobulins in order to defense against invading microorganisms, however, the regulation pathway of pIgR expression in teleosts remains unclear. In this investigation, to examine if the cytokine IFN-γ affected the expression of pIgR, the recombinant proteins of IFN-γ of grass carp was first prepared, after validating that natural pIgR expressed on grass carp (Ctenopharyngodon idellus) hepatocytes (L8824), the L8824 cells were supplemented by different recombinant IFN-γ concentrations at various times, the outcomes revealed a significant dose- and time-dependent increase in pIgR expressions at the gene and secretion component (SC) proteins levels. The levels of pIgR mRNA was measured increasing at 9 h, and increasing most significant during the 9–12 h period, the growth of SC was delayed until 24 h after IFN-γ stimulation. Moreover, protein synthesis inhibitors cycloheximide (CHX) was used to study on whether IFN-γ regulated pIgR expressions through a protein synthesis dependent pathway. Upon inhibitors CHX treatment, the expression of pIgR mRNA were inhibited significantly, and CHX treatment at any time during the first 9 h period demolished the growth in pIgR mRNA that was promoted by IFN-γ, suggesting that IFN-γ is required for the stimulation of pIgR mRNA, which needs de novo protein synthesis. All these outcomes revealed that IFN-γ could upregulate pIgR gene expression, and production of SC, and this IFN-γ stimulated pIgR expression through a protein synthesis dependent pathway, which provided evidences for IFN-γ serves as a regulator for the expression of pIgR, as well as our current knowledge of the expression of pIgR in teleost fish has been improved as a result.