Figure 7.

Model of IL-5R subunit regulation following IL-5 stimulation. IL-5 engagement of IL-5Rα leads to the recruitment of βc to form the high-affinity IL-5R (step 1). This protein/protein interaction (IL-5Rα/βc/IL-5) leads to the activation of intracellular signaling pathways that result in the activation of βc by both tyrosine and serine phosphorylation (step 2). Once activated, the cytoplasmic domains of βc are rapidly degraded by proteasomes to terminate agonistic signaling, resulting in the generation of β_IP/IL-5Rα/IL-5 complexes (step 3). This molecular complex is then endocytosed (step 4) and degraded in lysosomes (steps 4 and 5). In addition, IL-5 induces a reduction in IL-5Rα mRNA and protein expression, while simultaneously increasing sIL-5Rα expression (upper left corner). S-p, serine phosphorylation.