THE IL1 RECEPTOR ACCESSORY PROTEIN IS RESPONSIBLE FOR THE RECRUITMENTOF THE INTERLEUKIN-1 RECEPTOR-ASSOCIATED KINASE TO THE IL1 IL1 RECEPTOR-I COMPLEX/

Following interleukin-1 (IL1) stimulation, an IL1 receptor associated kinase (IRAK) is rapidly recruited to the receptor complex. However, i t is not understood if IRAK is able to interact directly with the intr acellular portion of the IL1-RI or if its recruitment is mediated by a different molecule, Using the yeast two-hybrid system, we have analys ed possible protein-protein interactions between IRAK, IL1-RI and IL1- RAcP. We found that IRAK is able to interact with the equivalent cytop lasmic region of the IL1-RAcP but is unable to interact with the cytop lasmic region of the IL1-RI. Immunoprecipitation of the IL1-RAcP follo wed by Western blot analysis using anti-IRAK antibodies revealed that IRAK co-precipitated with the IL1-RAcP. We propose that, in non-stimul ated cells, IRAK is bound to the IL1-RAcP and therefore, following IL1 stimulation, both molecules are recruited simultaneously to the IL1-R I complex. (C) 1997 Federation of European Biochemical Societies.