Interleukin-26 is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that in humans is encoded by the IL26 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

IL-26 is a 171-amino acid protein, which is similar in amino acid sequence to interleukin 10

Interleukin 10

Interleukin-10 , also known as human cytokine synthesis inhibitory factor , is an anti-inflammatory cytokine. In humans IL-10 is encoded by the IL10 gene....

. It was originally called AK155 and is composed of a signal sequence

Signal sequence

Signal sequence can refer to:*Protein targeting*Signal peptide*DNA uptake signal sequence...

, 6 helices, and 4 conserved cysteine

Cysteine

Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...

 residues. IL-26 is expressed in certain herpesvirus-transformed T cells but not in primary stimulated T cells. IL-26 signals through a receptor complex comprising two distinct proteins called IL-20 receptor 1

Interleukin 20 receptor, alpha subunit

Interleukin 20 receptor, alpha subunit is a subunit for the interleukin-20 receptor. IL20RA is its human gene.-Further reading:...

 and IL-10 receptor 2

Interleukin 10 receptor, beta subunit

Interleukin 10 receptor, beta subunit is a subunit for the interleukin-10 receptor. IL10RB is its human gene.IL10RB has also recently been designated CDW210B .-Further reading:...

. By signaling through this receptor complex, IL-26 induces rapid phosphorylation of the transcription factors STAT1

STAT1

STAT1 is a member of the Signal Transducers and Activators of Transcription family of transcription factors. STAT1 is involved in upregulating genes due to a signal by either type I, type II or type III interferons...

 and STAT3

STAT3

Signal transducer and activator of transcription 3 also known as STAT3 is a transcription factor which in humans is encoded by the STAT3 gene.- Function :The protein encoded by this gene is a member of the STAT protein family...

, which enhance IL-10 and IL-8

Interleukin 8

Interleukin-8 is a chemokine produced by macrophages and other cell types such as epithelial cells. It is also synthesized by endothelial cells, which store IL-8 in their storage vesicles, the Weibel-Palade bodies...

 secretion and as expression of the CD54

ICAM-1

ICAM-1 also known as CD54 is a protein that in humans is encoded by the ICAM1 gene. This gene encodes a cell surface glycoprotein which is typically expressed on endothelial cells and cells of the immune system...

molecule on the surface of epithelial cells.