An IL-4 receptor region containing an insulin receptor motif is important for IL-4-mediated IRS-1 phosphorylation and cell growth

Interleukin-4 (IL-4) treatment of 32D cells overexpressing Insulin Receptor substrate 1 (IRS-1) causes prompt tyrosine phosphorylation of IRS-1. Transfection of truncation mutants of the human IL-4 (huIL-4) receptor into 32D-IRS-1 cells demonstrated that the region from amino acid 437-557 is important for IL-4 signaling. This region of the IL-4 Receptor (IL-4R) contains the motif 488PL-X4-NPXYXSXSD502 (Insulin/IL-4R [I4R]) found in the Insulin and insulin-like growth factor 1 receptors. Mutation of Y497 to F yielded receptors that caused little or no IRS-1 phosphorylation in response to huIL-4 when expressed in 32D-IRS-1 cells. Most cell lines expressing Y497F also failed to proliferate in response to huIL-4. Furthermore, a glutathione-S-transferase fusion protein containing the I4R motif-bound IRS-1, tyrosine kinase(s), and other unidentified phosphoproteins with molecular sizes of 140, 80, and 55 kd. Thus, the central tyrosine of the I4R motif has a major role in IL-4-mediated signal transduction in 32D cells.