Receptors for the Four‐Helical Cytokines

AbstractCytokines belong to a family of proteins that coordinate the activity of the immune system and many other body functions. Most cytokines belong to a protein family exhibiting a four‐helical topology. Receptors for these cytokines belong to the immunoglobulin superfamily and are all type I transmembrane proteins. Within the cell, cytokines typically signal via the JAK–STAT‐signalling pathway and also via the Ras‐MAP‐kinase‐, Akt‐, PI3‐kinase and YAP pathways. Many cytokines form families, which are defined by common receptor subunits shared by the cytokine family members, thereby reducing the number of receptor complexes. Furthermore, this set‐up results in similar modes of signalling for the members of one cytokine family. Some cytokines with a four‐helical topology have been recognised as important therapeutic targets for the treatment of autoimmune diseases.Key ConceptsCytokines are small proteins of 100–200 amino acids, which belong to several different protein families.Most, but not all, cytokines belong to the four‐helical class of cytokines.Many cytokines can be grouped into families, which are defined by the usage of common receptor subunits and therefore share many signalling pathways.Cytokine receptors also occur as soluble proteins, which can act as agonists and antagonists.Cytokines and cytokine receptors are therapeutic targets for the treatment of autoimmune diseases.