IL-5 Receptor

IL-5 receptor (IL-5R) belongs to the type I cytokine receptor family and is a heterodimer consisting of two polypeptide chains, an α subunit that binds IL-5 and confers specificity to the receptor cytokine, and a β subunit that contains the signal transduction domain. Among them, the IL-5Rα chain is expressed only by eosinophils, some basophils and murine B1 cells or B-cell precursors. The β chain does not bind IL-5, is not specific for this cytokine, and is expressed on almost all leukocytes. At the same time, the β-chain of the IL-5 receptor is also utilized by the IL-3 and GM-CSF receptors, hence the term βc or common β-chain. When IL-5R binds to its ligand IL-5, it activates a series of signal transduction cascades that stimulate the induction of rapid tyrosine phosphorylation of cellular proteins, including βc, SH2/SH3-containing proteins such as Vav and Shc, Btk and Btk-related molecules, JAK1/JAK2 and STAT1/STAT5, PI3K, and activation of downstream MAP kinase signaling molecules. For example, IL-5 binding to mouse B cells and IL-5R on mouse and human eosinophils activates JAK1/2 and STAT1/5. The Ras extracellular signal-regulated kinase (ERK) pathway is also associated with IL-5 signaling to maintain cell survival, proliferation, and differentiation of eosinophils^[1][2].

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