| Co-Investigator(Kenkyū-buntansha) |
SPRINGER Tim ハーバード大学, 医学部, 教授
PERLMUTTER Roger University of Washington, School of Medicine, Professor, 医学部, 教授
MELCHERS Friz Basel Institute of Immunology, Director, 所長, 教授
TAKAKI Satoshi The University of Tokyo, Institute of Medical Science, Lecturer, 医科学研究所, 助手 (10242116)
KINASHI Tatsuo The University of Tokyo, Institute of Medical Science, Lecturer, 医科学研究所, 助手 (30202039)
TIMOTHY Springer Center for Blood Research, Harvard Medical School, Professor
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| Research Abstract |
The human IL-5R (hIL-5R) consists of two distinct polypeptide chains, alpha and beta which activates JAK1 and JAK2 and STAT5. We analyzed the interaction between hIL-5Ralpha and betac by immuno-precipitation using anti-hIL-5Ralpha and anti-betac mAbs. The binding of JAK1 and JAK2 to each hIL-5R subunit was also evaluated inTF-h5Ralpha. IL-5 stimulation induced the recruitment of betac to hIL-5Ralpha, although in the absence of IL-5 the subunits remained independent. JAK2 and JAK1 were associated with hIL-5Ralpha and betac, respectively. IL-S stimulation resulted in tyrosine phosphoryl-ation of JAK2, JAK1, betac, and STAT5. Moreover, IL-5-induced dimerization of IL-5R subunits caused JAK2 activation and the betac phosphorylation. Furthermore, tyrosine phosphorylation of JAK1 depended on the activation of JAK2. The cytoplasmic stretch at position 346-387, containing the proline-rich region was necessary for JAK2 binding. These observations suggest that activation of hIL-5Ralpha associated JAK2 is indispensable for IL-5 signaling event.
Bone-marrow derived mast cells adhered to fibronectin via VLA-5 (alpha5beta1) upon stimulation with steel factor (SLF) and FceRI cross-linking as well as PMA.SLF and PMA, but not FcepsilonRI cross-linking induced a diffusion of VLA-5 as well as drastic morphological changes. In contrast, only FcepsilonRI cross-linking increased affinity of VLA-5. We also showed PI 3-kinase as a critical affinity modulator by a specific inhibitor, wortmannin, and by introduction ofa constitutively active p110 subunit ofPI-3 kinase. Utilization of affinity or spatial modulation of VLA-5 caused differential effects on adhesion in the presence of physiological concentrations of soluble fibronectin. Our findings indicate that adhesion via VLA-5 are regulated physiologically by two mechanisms ; affinity modulation through PI 3-kinase and spatial modulation possibly through protein kinase C.
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