Cloning and characterization of a mouse IL-12 receptor-beta component
Chua, A.O.; Wilkinson, V.L.; Presky, D.H.; Gubler, U.
Journal of Immunology 155(9): 4286-4294
1995
ISSN/ISBN: 0022-1767 PMID: 7594587 Document Number: 439311
Using DNA cross-hybridization, we have isolated and characterized cDNA clones encoding a mouse (mo) IL-12R-beta component. Two forms of cDNA were found. The first form encodes a receptor protein that has an overall structure very similar to that of the known human (hu) IL-12R-beta with 54% amino acid identity, whereas in the second type of mouse cDNA, the equivalent of the transmembrane region has been deleted. This presumed alternative splicing event also gives rise to a frame shift that results in a receptor with an identical extracellular domain but a different C-terminal sequence. Whether this alternative C terminus is capable of signaling is not yet known. Both types of receptors when expressed in COS-7 cells are membrane associated and bind moIL-12 with an affinity of 1 nM, similar to the affinity of huIL-1 2R-beta for huIL-12. The monomeric size of both moIL-12R-beta proteins is about 100 kDa. Similar to huIL-12R-beta, moIL-12R-beta is expressed at the surface of COS-7 and Ba/F3 cells as a dimer/oligomer whose formation is independent of IL-12 binding. When expressed in Ba/F3 cells, moIL-12R-beta binds moIL-12 with two affinities of 50 and 470 pM, corresponding to the medium and high affinity IL-12 binding sites previously identified on mouse Con A lymphoblasts. Despite the higher affinity displayed by the moIL-12R-beta in Ba/F3 cells, this receptor alone is not sufficient to transduce a signal, suggesting that another subunit is probably required to generate a functional moIL-12R complex.