| Modification Notes |
Interleukin 5 (IL-5) is a soluble T cell-derived factor, also known as T cell-replacing factor (TRF), that induces B cell and eosinophil growth and differentiation. IL-5 exerts its biological activity through the IL-5 receptor (IL-5R), which is composed of two chains: an å chain that binds IL-5 with low affinity and a ∫ chain that does not bind IL-5, but together with the IL-5 å chain, constitutes the high affinity IL-5 receptor. The cytoplasmic domain of both the å and ∫ chains is essential for signal transduction. Specifically, the membrane-proximal proline-rich sequence of the cytoplasmic domain of the IL-5R receptor å subunit, IL-5Rå, is critical for the IL-5 induced proliferative response, expression of nuclear proto-oncogenes and tyrosine phosphorylation of cellular proteins, such as JAK1 and JAK2. Alternative splicing of the IL-5Rå gene produces several isoforms, including a membrane-anchored isoform and a soluble isoform. The soluble isoform competes with IL-5 for binding to IL-5R and inhibits IL-5-mediated receptor activation and inflammatory mediator production, and, therefore, may be useful in treating asthma. |
