Se. Adunyah et al., INTERLEUKIN-13 INDUCES RAPID TYROSINE PHOSPHORYLATION AND ACTIVATION OF RAF-1 KINASE IN HUMAN MONOCYTIC PROGENITOR-CELL LINE U937, Biochemical and biophysical research communications, 206(1), 1995, pp. 103-111
IL-13 is a pleiotropic cytokine produced by Th0, Th1-like, and CD8 T c
ells in response to antigen stimulation. Its biological effects includ
e suppression of cytotoxic activity of monocytes/macrophages and suppr
ession of pro-inflamatory cytokine production. However, the mechanism
of IL-13 remains unknown. In this study we investigated the effects of
rhIL-13 on tyrosine phosphorylation in U937 monocytic progenitor cell
s by immunoblotting and immunocomplex kinase assays. We demonstrate th
at rhIL-13 stimulates dose-dependent tyrosine phosphorylation of sever
al proteins of Mr. 93, 80, 74, 49.5, 42, 30, 22 and 18 kDa within 30 s
ec. The effect of IL-13 was blocked by the tyrosine kinase inhibitor e
rbstatin. Furthermore, IL-13 induces tyrosine phosphorylation and rapi
d activation of raf-1 kinase. These findings provide the first evidenc
e that the mechanism of IL-13 involves rapid tryrosine phosphorylation
and activation of raf-1 serine/threonine kinase. (C) 1995 Academic Pr
ess, Inc.