Structure-function analysis of the p35 subunit of mouse interleukin 12.
Mouse IL-12 acts on both mouse and human cells; human IL-12 acts only on human cells. This species specificity is determined by the p35 subunit of the IL-12 heterodimer. Since mouse and human p35 sequences are 60% identical, the determinants for the species specificity most likely residue in the nonhomologous sequences of mouse p35. To identify the regions on the p35 subunit interacting with the mouse IL-12 receptor, we constructed a series of chimeric mouse-human p35 molecules by replacing mouse sequences with the nonhomologous human counterparts. An IL-12 heterodimer containing a mouse-human p35 chimera with five residues changed in three discontinuous sites had drastically reduced (750-3000-fold) bioactivities on mouse cells. However, the competitive binding activity of the same mutant IL-12 heterodimer on mouse cells was only reduced 30-fold relative to wild-type IL-12. These findings therefore suggest that 1) the mouse p35 subunit participates in both receptor binding and signaling, 2) the mutations introduced into p35 affect signaling to a much greater extent than receptor binding, and 3) the five residues identified on p35 are required for interacting with the mouse, but not with the human IL-12 receptor and as such contribute extensively to the observed species specificity of IL-12.
Zou
J J
JJ
Department of Inflammation/Autoimmune Diseases, Hoffmann-La Roche Inc., Nutley, New Jersey 07110-1199.
Schoenhaut
D S
DS
Carvajal
D M
DM
Warrier
R R
RR
Presky
D H
DH
Gately
M K
MK
Gubler
U
U
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D002522:Chlorocebus aethiops; D006801:Humans; D018664:Interleukin-12 / Q000096:biosynthesis / Q000737:chemistry* / Q000494:pharmacology*; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D018664:Interleukin-12