Recombinant Human IL-20 Protein

Human Interleukin 20 (IL-20) was identified by searching sequence databases for translated sequences containing a signal sequence and amphipathic helices found in helical cytokines. Human IL-20 is synthesized as a 176 amino acid (aa) precursor with a 24 aa signal sequence and a 152 aa mature segment. There are no N-linked glycosylation sites and it is doubtful that the native molecule is glycosylated. Although IL-20 is a distant member of the IL-10 family, it functions as a monomer. IL-20 shares less than 40% aa sequence identity with other IL-10 family members. Mouse and human IL-20 share 77% aa sequence identity in their mature segments. Human IL-20 is active on mouse cells. IL-20 production has been found in skin and trachea. In particular, activated keratinocytes and, possibly, monocytes are reported to express IL-20. There are two heterodimeric receptor complexes for IL-20. The first is composed of IL-20 R alpha andIL-20 R beta. The second is composed of IL-22 R and IL-20 R beta. Whereas the IL-22 R/IL-20 R beta complex is shared with IL-24/mda-7, the IL-20 R alpha /IL-20 R beta  complex is shared with both IL-19 and IL-24. Little is known about the function of IL-20. It is reported to induce the proliferation of multipotential hematopoietic progenitor cells, direct the differentiation and expansion of keratinocytes, and promote the release of proinflammatory mediators in keratinocytes and other IL-20 receptor expressing cells (1 - 6).