Growth hormone prevents apoptosis through activation of nuclear factor-kappa B in interleukin-3-dependent Ba/F3 cell line

The pro-B Ba/F3 cell line requires interleukin-3 and serum for growth, and their removal results in cell apoptosis. Ba/F3 cells transfected with the G H receptor (GHR) cDNA become able to proliferate in response to GH. To inve stigate the role of GH in the control of apoptosis, Ba/F3 cells expressing either the wild-type rat GHR (Ba/F3 GHR) or a mutated rat GHR (Ba/F3 ILV/T) were used. We show that Ba/F3 GHR cells, but not parental Ba/F3 or Ba/F3 I LV/T cells, were able to survive in the absence of growth factor. Furthermo re, an autocrine/paracrine mode of GH action was suggested by the demonstra tion that Ba/F3 cells produce GH, and that addition of GH antagonists (B203 6 and G120K) promotes apoptosis of Ba/F3 GHR cells. Consistent with surviva l, the levels of both antiapoptotic proteins Bcl-2 and Bag-1 were maintaine d in Ba/F3 GHR cells, but not in parental Ba/F3 cells upon growth factor de privation. Constitutive activation of the transcription factor nuclear fact or-kappa B (NF-kappa B), which has been shown to promote cell survival, was sustained in Ba/F3 GHR cells, whereas no NF-kappa B activation was detecte d in parental Ba/F3 cells in the absence of growth factor. Furthermore, add ition of GH induced NF-kappa B DNA binding activity in Ba/F3 GHR cells. Ove rexpression of the mutated I kappa B alpha (A32/36) protein, known to inhib it NF-kappa B activity, resulted in death of growth factor-deprived Ba/F3 G HR cells, and addition of GH was no longer able to rescue these cells from apoptosis. Together, our results provide evidence for a new GH-mediated pat hway that initiates a survival signal through activation of the transcripti on factor NF-kappa B and sustained levels of the antiapoptotic proteins Bcl -2 and Bag-1.