Mice homozygous for this "IL4Rα Y500F" mutant allele are viable and fertile. The mice express a mutant IL4Rα chain with a phenylalanine substitution at the proximal tyrosine residue (Y500F) in the cytoplasmic tail. This residue is a critical component of the insulin/interleukin-4 receptor (I4R) motif, and is required for binding by phosphotyrosine-binding domain (PTB) adaptor proteins and for initiating subsequent downstream signaling cascades in response to IL-4. Allele-specific PCR verifies the amino acid substitution. The Y500F mutation abrogates insulin receptor substrate-2 (IRS-2) phosphorylation, and impairs IL-4-induced CD4+ lymphocyte proliferation with no reported effect on Stat6 activation, IL-4-responsive gene product up-regulation, or Th cell differentiation under Th2 polarizing conditions. In vivo, the Y500F mutation is associated with increased allergen-induced IgE production, airway hyper-responsiveness (AHR), tissue eosinophilia, goblet cell metaplasia, and mucus production. These IL4Rα Y500F mutant mice may be useful in immunological studies of mitogenic signal transduction in response to IL-4, specifically antigen-specific antibody responses, allergic airway inflammation, and asthma.
