It is a heterodimer of the interleukin 5 receptor alpha subunit and CSF2RB.
[1][2] The IL-5 receptor (IL-5R) belongs to the type I cytokine receptor family and is a heterodimer composed of two polypeptide chains, one α subunit, which binds IL-5 and confers upon the receptor cytokine specificity, and one β subunit, which contains the signal transduction domains.
[3] Like many other cytokine receptors, alternative splicing of the α-chain gene results in expression of either a membrane bound or soluble form of the bα-chain.
[4] In either case, the α-chain exclusively binds IL-5 and the intra-cellular portion of IL-5Rα is associated with Janus kinase (JAK) 2, a protein tyrosine-kinase essential in IL-5 signal transduction.
Unlike the α-chain, the β-chain does not bind IL-5, is not specific to this cytokine, and is expressed on practically all leukocytes.