Autocrine TGF-beta signaling is required for the GDNF/CNTF-induced neuronal differentiation of adrenal chromaffin tsAM5D cells expressing temperature-sensitive SV40 T-antigen.

We recently established adrenal medullary cell line tsAM5D, which was immortalized by use of a temperature-sensitive mutant of the oncogene simian virus 40 large T-antigen. In the present study, when co-treated with glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF), tsAM5D cells proliferated at the permissive temperature (33 degrees C) for the T-antigen expression and differentiated into neuron-like cells at the nonpermissive temperature (39 degrees C). Interestingly, in GDNF/CNTF-treated cultures, the addition of pan-specific transforming growth factor (TGF)-beta-neutralizing antibody did not affect the cell proliferation at 33 degrees C, but significantly reduced the survival of neuronally differentiated cells at 39 degrees C. Using real-time RT-PCR for analysis of GDNF/CNTF-treated cells, we found that the expression of mRNAs for TGF-beta1, TGF-beta2, and TGF-beta3 was up-regulated by the temperature shift. These results suggest that autocrine TGF-beta signaling is necessary for the survival of GDNF/CNTF-differentiated tsAM5D cells upon the temperature shift.