IL-4-dependent proliferation of BA/F3 cells expressing a growth-negative mutant of the human IL-4 receptor is restored by enforced expression of Bcl-2

We have studied the regulation of growth and apoptosis in murine BA/F3 cells stably expressing cytoplasmic deletion mutants of the human interleukin-4 receptor (hIL-4R). Previously, we showed that BA/F3 cell transfectants expressing a cytoplasmic deletion mutant of the hIL-4R that lacks the region between Thr(462) and Ala(580), referred to as Delta R3, fails to proliferate in the presence of hIL-4. Here we report that supertransfection of Delta RS-expressing cells with a constitutively active murine bcl-2 gene results in prolonged survival of the Delta R3/bcl-2 double transfectants in the absence of cytokines. More importantly, however, the constitutive expression of Bcl-2 restored their capacity to grow permanently with hIL-4. This may provide an explanation for the discrepancy with previous reports showing growth mediation by hIL-4R truncated at position 367.