JAK2 and JAK1 constitutively associate with an interleukin-5 (IL-5) receptor alpha and betac subunit, respectively, and are activated upon IL-5 stimulation.
The human interleukin-5 receptor (hIL-5R) consists of a unique alpha subunit (hIL-5Ralpha) and a common beta subunit (betac) that activate two Janus kinases (JAK1 and JAK2) and a signal transducer and activator of transcription (STAT5). The precise stoichiometry of the hIL-5R subunits and the role of JAK kinases used in IL-5 signaling were investigated. We analyzed the interaction between hIL-5Ralpha and betac by immunoprecipitation using anti-hIL-5Ralpha and anti-betac monoclonal antibodies. The binding of JAK1 and JAK2 to each hIL-5R subunit was also evaluated in the hIL-5-responsive cell line, TF-h5Ralpha. It was observed that IL-5 stimulation induced the recruitment of betac to hIL-5Ralpha, although in the absence of IL-5 the subunits remain independent. In the absence of IL-5, JAK2 and JAK1 were associated with hIL-5Ralpha and betac, respectively. IL-5 stimulation resulted in tyrosine phosphorylation of JAK2, JAK1, betac, and STAT5. Moreover, IL-5-induced dimerization of IL-5R subunits caused JAK2 activation and betac phosphorylation even in the absence of JAK1 activation. Furthermore, tyrosine phosphorylation of JAK1 was dependent on the activation of JAK2. Detailed study of the C-terminal truncated cytoplasmic domain of hIL-5Ralpha revealed that the cytoplasmic stretch at position 346-387, containing the proline-rich region, is necessary for JAK2 binding. These observations suggest that activation of hIL-5Ralpha-associated JAK2 is indispensable for the IL-5 signaling event.
Ogata
N
N
Department of Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan. Medicine, Kumamoto, Japan.
Kouro
T
T
Yamada
A
A
Koike
M
M
Hanai
N
N
Ishikawa
T
T
Takatsu
K
K
D006801:Humans; D015848:Interleukin-5 / Q000378:metabolism*; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D018123:Receptors, Interleukin / Q000378:metabolism*; D053649:Receptors, Interleukin-5; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D015848:Interleukin-5; D011518:Proto-Oncogene Proteins; D018123:Receptors, Interleukin; D053649:Receptors, Interleukin-5; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; D053613:Janus Kinase 1; D053614:Janus Kinase 2