Neurotrophin-3 mediates the autocrine survival of the catecholaminergic CAD CNS neuronal cell line.

The mechanisms for neuronal survival in the CNS are not well understood, but are likely to be complex due to possible autocrine and redundant neurotrophic support. Most studies have focused on the nerve growth factor (NGF)/TrkA pathway in peripheral neurons, and little is known regarding the other neurotrophins, particularly neurotrophin-3 (NT3)/TrkC. Progress has also been hampered by the paucity of homogenous and accessible CNS neuronal experimental models. We now report that the novel catecholaminergic CNS cell line, CAD, is capable of autocrine survival mediated by NT3. The CAD cell is of CNS neuronal origin and can survive and morphologically differentiate in the absence of exogenously provided trophic factors. However, neutralizing reagents against NT3 (the neutralizing TrkC-IgG fusion protein and anti-NT3 antibodies), but not those that block the other neurotrophins, inhibited survival of differentiating CAD cells. Moreover, Trk phosphorylation was detected in CAD cells and its inhibition by K252a was correlated with K252a-induced apoptosis. Finally, endogenous NT3 was detectable in CAD cell extracts by a specific ELISA assay. Thus, CAD cells possess an autocrine survival capability mediated by NT3, and may provide a valuable model system for studying the signaling pathways that mediate the actions of this little understood neurotrophin.