Molecular cloning and characterization of a second subunit of the interleukin 1 receptor complex.
A monoclonal antibody (mAb) was isolated that blocked the binding and bioactivity of both human and murine interleukin 1 beta (IL-1 beta) on murine IL-1 receptor-bearing cells. This mAb recognized a protein that was distinct from the Type I and Type II IL-1 receptors, suggesting that an additional protein exists that is involved in IL-1 biological responses. By expression cloning in COS-7 cells, we have isolated a cDNA from mouse 3T3-LI cells encoding this putative auxiliary molecule, which we term the IL-1 receptor accessory protein (IL-1R AcP). Sequence analysis of the cDNA predicts an open reading frame that encodes a 570-amino acid protein with a molecular mass of approximately 66 kDa. The IL-1R AcP is a member of the Ig superfamily by analysis of its putative extracellular domain and also bears limited homology throughout the protein to both Type I and Type II IL-1 receptors. Northern analysis reveals that murine IL-1R AcP mRNA is expressed in many tissues and appears to be regulated by IL-1. In mammalian cells expressing natural or recombinant Type I IL-1R and IL-1R AcP, the accessory protein forms a complex with the Type I IL-1R and either IL-1 alpha or IL-1 beta but not IL-1ra. The recombinant accessory protein also increases the binding affinity of the recombinant Type I IL-1R for IL-1 beta when the two receptor proteins are coexpressed. Therefore, the functional IL-1 receptor appears to be a complex composed of at least two subunits.
Greenfeder
S A
SA
Department of Inflammation/Autoimmune Diseases, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey 07110, USA.
Nunes
P
P
Kwee
L
L
Labow
M
M
Chizzonite
R A
RA
Ju
G
G
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D015152:Blotting, Northern; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000737:chemistry; D007375:Interleukin-1 / Q000378:metabolism; D053577:Interleukin-1 Receptor Accessory Protein; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics*; D017472:Receptors, Interleukin-1 / Q000235:genetics*
D000911:Antibodies, Monoclonal; D018076:DNA, Complementary; C507765:IL1RAP protein, human; C507767:Il1rap protein, mouse; D007375:Interleukin-1; D053577:Interleukin-1 Receptor Accessory Protein; D011506:Proteins; D017472:Receptors, Interleukin-1