Differential associations between the cytoplasmic regions of the interleukin-12 receptor subunits beta1 and beta2 and JAK kinases.
The role of the cytoplasmic regions of interleukin-12 receptors (IL-12R) beta1 and beta2 in stimulating proliferation was examined. The transmembrane and cytoplasmic regions of IL-12Rbeta1 or IL-12Rbeta2 were fused to the extracellular domain of the epidermal growth factor (EGF) receptor, yielding chimeric receptors E12R1 and E12R2, respectively. These chimeras were stably transfected into BaF3 cells, a factor-dependent murine pro-B cell line. Only E12R2 or E12R1+E12R2 transfectants were capable of EGF-dependent proliferation. EGF-dependent phosphorylation of E12R2, JAK2, Tyk2, and STAT3 was observed. JAK2 was phosphorylated in E12R1-, E12R2-, and E12R1+E12R2-expressing cells. However, direct associations were detectable only between E12R2 and JAK2. Tyk2 phosphorylation was observed only in cells expressing E12R1 or E12R1+E12R2. In parallel with this activation pattern, direct interactions only between Tyk2 and E12R1 were demonstrable. Phosphorylation of STAT3 was observed in cells expressing E12R1, E12R2, and E12R1+E12R2. The expression levels of STAT4 protein in BaF3 cells are undetectable by the methods employed here; therefore, STAT4 phosphorylation was not observed. Taken together, the data indicate that differential interactions take place between the cytoplasmic regions of the two IL-12R subunits and JAK2/Tyk2 and that the cytoplasmic region of IL-12Rbeta2 alone is capable of delivering a proliferative signal.
Zou
J
J
Department of Inflammation/Autoimmune Diseases, Hoffmann-La Roche Inc., Nutley, New Jersey 07110-1199, USA.
Presky
D H
DH
Wu
C Y
CY
Gubler
U
U
D017609:Barium Compounds / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D005459:Fluorides / Q000378:metabolism; D006801:Humans; D018664:Interleukin-12 / Q000378:metabolism*; D053616:Janus Kinase 3; D010766:Phosphorylation; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D018123:Receptors, Interleukin / Q000737:chemistry / Q000378:metabolism*; D053707:Receptors, Interleukin-12; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D017609:Barium Compounds; C508438:IL12RB1 protein, human; C508439:IL12RB2 protein, human; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D011993:Recombinant Fusion Proteins; D018664:Interleukin-12; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; C507933:JAK3 protein, human; D053616:Janus Kinase 3; C055150:barium fluoride; D005459:Fluorides