Recombinant Rat IL-22 Protein

Interleukin-22 (IL-22), also known as IL-10-related T cell-derived inducible factor (IL-TIF), was initially identified as a gene induced by IL-9 in mouse T cells and mast cells. It belongs to the IL-10-related cytokine family that consists of six members (IL-10, IL-19, IL-20, IL-22, IL-24/MDA-7, and IL-26/AK155). These proteins share structural homology and some degree of amino acid sequence homology to IL-10. Receptors for these proteins are members of the class II cytokine receptor family (1). The rat IL-22 coding region corresponding to amino acids 48 - 179 was deduced from a rat genomic clone (Genbank accession numaber AC111483). The N-terminal portion was cloned from rat adipocyte first strands using degenerate forward primers based on the human and mouse IL-22 amino acid sequences in two independent PCR reactions (2). Rat IL-22 cDNA predicts a 179 amino acid (aa) residue precursor protein with a putative 33 aa signal peptide that is cleaved to generate a 147 aa mature protein, which shares approximately 92% and 79% aa sequence identity with mouse and human IL-22, respectively. IL-22 signals through a heterodimeric receptor complex composed of the IL-22R (CRF2-9) subunit and the ( chain of IL-10R (CRF2-4). In addition, IL-22 also binds to a secreted member of the class II cytokine receptor family called IL-22BP that acts as a natural IL-22 antagonist. IL-22 upregulates acute-phase reactants in the liver and hepatoma cells. In a rat hepatoma cell line, IL-22 has been shown to activate the Jak/STAT and MAPK signaling pathways (3).