14-3-3 zeta interacts with the alpha-chain at human interleukin 9 receptor

Interleukin 9 (IL-9) exerts its pleiotropic effects through the IL-9 recept or (IL-9R) complex, which consists of the IL-9R alpha-chain, which determin es the cytokine specificity, and the IL-2 receptor gamma-chain. In the pres ent study we used a modified yeast two-hybrid system to isolate cDNA specie s encoding proteins that interacted with the intracellular domain of the hu man IL-9R alpha-chain (hIL-9R alpha). We have identified 14-3-3 zeta as an hIL-9R alpha-interacting protein. We also mapped residues 518-522 (Arg-Ser( 519)-Trp-Thr(521)-Phe) in hIL-9R alpha and helix I of 14-3-3 zeta as being important for interaction. Moreover, peptide competition experiments sugges ted that interaction between hIL-9R alpha and 14-3-3 zeta requires the phos phorylation of Ser(519) or Thr(521). This is the first demonstration that 1 4-3-3 can interact with a non-tyrosine kinase receptor. The interaction bet ween 14-3-3 and IL-9R alpha but not IL-4R alpha also suggests a potential r ole for 14-3-3 in determining cytokine specificity.