Effects of altered cyclophilin A expression on growth and differentiation of human and mouse neuronal cells.

1. Cyclophilin A (CyP-A), a soluble cytoplasmic immunophilin, is known for its involvement in T cell differentiation and proliferation. Although CyP-A has a pivotal role in the immune response, it is most highly concentrated in brain, where its functions are largely unknown. 2. We reported previously that a murine neuroblastoma (NB-P2) cell line can partially differentiate into neurons when treated with cyclosporin A (CyS-A), implicating a role for CyP-A in neuronal differentiation (Hovland et al. [1999]. Neurochem. Int. 3:229-235). 3. The role of CyP-A in regulating neuronal growth and differentiation is not well defined. To investigate this, we first tested the utility of retroviral-mediated gene transfer and expression in human embryonic brain (HEB) and NB-P2 cells. Second, we examined the effects of retroviral-mediated overexpression or antisense-mediated reduction of CyP-A in HEB and NB-P2 cells. 4. Our data show that retroviral vectors are efficient for stable gene transfer and expression in both cell lines. Moreover, neither overexpression nor reduction of CyP-A expression in NB-P2 cells altered the growth rate or induced differentiation. More importantly, the up-or down-regulation of CyP-A expression did not affect the magnitude of cAMP-induced NB-P2 differentiation. However, overexpression of CyP-A increased the growth rate of HEB cells. 5. In summary, the utility of retroviral vectors for stable gene expression in human embryonic brain and murine neuroblastoma cells was shown. Furthermore, a novel role for CyP-A in augmenting the proliferation of human embryonic brain cells was demonstrated in vitro.