Interleukin-4-dependent proliferation dissociates p44erk-1, p42erk-2, and p21ras activation from cell growth

The activation of erk/mitogen-activated protein kinases and p21ras is strongly associated with progression through the cell cycle. Cell growth induced by the cytokine interleukin-4 (IL-4) effectively dissociates the activation of p44erk-1 and p42erk-2 mitogen-activated protein kinases and p21ras from cell proliferation. In two cell lines of T lymphocyte and myeloid origin that were dependent upon IL-4 for continuous growth, IL-4 failed to detectably activate or induce tyrosine phosphorylation of p44erk-1 and p42erk-2. The activation of p21ras was also not detectably affected by IL-4 treatment of these cells. Treatment of the same cells with other growth factors (colony-stimulating factor-1 and Steel factor) or phorbol esters induced the tyrosine phosphorylation and activation of p44erk-1 and p42erk-2 and stimulated p21ras activity. The presence of IL-4 neither diminished nor enhanced the activation of p44erk-1 and p42erk-2 by colony-stimulating factor-1, Steel factor, or 12-O-tetradecanoylphorbol-13-acetate. Furthermore, IL-4 also failed to activate p44erk-1, p42erk-2, and p21ras in normal T lymphocytes and mast cells derived from spleen and bone marrow, respectively. Significantly, these findings demonstrate that IL-4-induced cell growth may be dissociated from the activation of p44erk-1, p42erk-2, and p21ras, suggesting that their activation may not be an absolute requirement for growth factor-stimulated mitogenesis.