Regulation of Interleukin-5 Receptor Signaling

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DESCRIPTION (provided by applicant): Dr. Martinez-Moczygemba is a postdoctoral fellow whose research interest is to identify the molecular events mediating interleukin-5 (IL-5)-induced signal termination. Understanding these mechanisms should provide novel targets for the modulation of IL-5-mediated inflammatory responses such as allergic inflammation and asthma. The Research Scholar Development Award (K22) will aid Dr. Martinez-Moczygemba to accomplish her research goals as well as to attain a tenure-track assistant professor appointment. IL-5 specifically promotes the differentiation and survival of eosinophils and is critical to the pathobiology of eosinophilic inflammation in allergic disorders and asthma. IL-5 initiates its cellular effects by binding to a heterodimeric IL-5 receptor leading to the activation of the JAK!STAT, Ras/MAPK, and the PI3 kinase signaling pathways. The goal of this proposal is to delineate the molecular events that initiate, mediate, and modulate termination of IL-5 signal transduction. Aim I. Elucidate the molecular events that initiate proteasome termination of IL-5-induced signal transduction. We will determine if tyrosine or serine phosphorylation of betac is required for its proteasomal degradation by using specific inhibitors of these kinases, as well as making site-directed mutants of these beta-c phosphorylation sites. We will also determine if beta-c ubiquitination is necessary for its proteasomal degradation. Aim 2. Investigate the molecular mechanisms that mediate endocytosis and lysosomal degradation of the full length and truncated IL-5R following IL-5 stimulation. Potential endocytic consensus sequences in the cytoplasmic domains of beta-c and IL-5R-alpha will be evaluated for their role in ligand-induced endocytosis of the full-length receptors by targeted deletions and by site-directed mutagenesis. Aim 3. Determine if other shared cytokine signaling receptor chains are proteasomally-regulated. Other shared signaling receptor chains such as gamma- c / IL-4R-alpha will be analyzed for their susceptibility to degradation by proteasomes following ligand stimulation. Aim 4. Demonstrate the physiologic consequence of cytokine-induced heterotypic desensitization of beta-c receptors in vivo. GM-CSF and IL-3 over-expressing transgenic mice will be evaluated for their ability to develop eosinophilia following treatment with high doses of IL-5. In addition, eosinophils from IL-5 transgenic mice will be isolated and analyzed for their ability to be further stimulated by GM-CSF or IL-3 in vitro.