A membrane-proximal region of the interleukin-2 receptor gamma c chain sufficient for Jak kinase activation and induction of proliferation in T cells.
The interleukin-2 (IL-2) receptor (IL-2R) consists of three distinct subunits (alpha, beta, and gamma c) and regulates proliferation of T lymphocytes. Intracellular signalling results from ligand-mediated heterodimerization of the cytoplasmic domains of the beta and gamma c chains. To identify the residues of gamma c critical to this process, mutations were introduced into the cytoplasmic domain, and the effects on signalling were analyzed in the IL-2-dependent T-cell line CTLL2 and T-helper clone D10, using chimeric IL-2R chains that bind and are activated by granulocyte-macrophage colony-stimulating factor. Whereas previous studies of fibroblasts and transformed T cells have suggested that signalling by gamma c requires both membrane-proximal and C-terminal subdomains, our results for IL-2-dependent T cells demonstrate that the membrane-proximal 52 amino acids are sufficient to mediate a normal proliferative response, including induction of the proto-oncogenes c-myc and c-fos. Although gamma c is phosphorylated on tyrosine upon receptor activation and could potentially interact with downstream molecules containing SH2 domains, cytoplasmic tyrosine residues were dispensable for mitogenic signalling. However, deletion of a membrane-proximal region conserved among other cytokine receptors (cytoplasmic residues 5 to 37) or an adjacent region unique to gamma c (residues 40 to 52) abrogated functional interaction of the receptor chain with the tyrosine kinase Jak3. This correlated with a loss of all signalling events analyzed, including phosphorylation of the IL-2R beta-associated kinase Jak1, expression of c-myc and c-fos, and induction of the proliferative response. Thus, it appears in T cells that Jak3 is a critical mediator of mitogenic signaling by the gamma c chain.
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
B H
BH
Nelson
J D
JD
Lord
P D
PD
Greenberg
D000595:Amino Acid Sequence; D000818:Animals; D004789:Enzyme Activation; D016762:Genes, fos; D016259:Genes, myc; D006801:Humans; D053613:Janus Kinase 1; D053616:Janus Kinase 3; D008024:Ligands; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*
D008024:Ligands; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507933:JAK3 protein, human; C507905:Jak1 protein, mouse; C507935:Jak3 protein, mouse; D053613:Janus Kinase 1; D053616:Janus Kinase 3