MIP-T3 associates with IL-13Ralpha1 and suppresses STAT6 activation in response to IL-13 stimulation.

To unravel the mechanism of interleukin-13 (IL-13)-specific functions, we sought to identify IL-13 receptor (IL-13R) binding molecules. A novel human IL-13Ralpha1 binding protein (IL13RBP1) has been identified using yeast tri-hybrid system, which was found to encode the same protein as MIP-T3 (microtubule interacting protein that associates with tumor necrosis factor (TNF) receptor associating factor-3 (TRAF3)). It constitutively associates with IL-13Ralpha1 and suppresses IL-4/13-induced signal transducer and activator of transcription-6 (STAT6) phosphorylation. IL-13-induced STAT6 activation was also inhibited as determined by dual luciferase assay and electrophoretic mobility shift assay (EMSA). These results suggest that MIP-T3 is a novel inhibitor of IL-13 signaling and may be a useful molecule in ameliorating various conditions in which IL-13 plays a central role.