Study of bcl-2 function in neuronal cells

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Bcl-2 is a unique oncogene that prevents apoptotic cell death. The specific aim supported by this grant was to elucidate the bcl-2 function in neuronal cells.We have shown by a microinjection procedure that bcl-2 protects rat sympathetic neurons in a primary culture from cell death induced by nerve growth factor-depletion. We have obtained a similar observation that a rat phechromocytoma cell line, PC12 was efficinetly rescued from cell death induced by serum depletion by overexpression of human bcl-2 gene. These data indicate that bcl-2 is able to exert its death-sparing activity in neuronal cells as well as lymphoid cells. We have generated the transgenic mice expressing high levels of bcl-2 in neuronal cells in which facial motor neurons did not degenerate after axotomy, providing the first evidence for in vivo function of bcl-2 in neurons and suggesting that the mice will be very useful for study of neurodegenarative disorders. To elucidate roles of bcl-2 normally expressed in neuronal cells, the mice homozygouly deleted for bcl-2 gene were generated. The mice revealed pleiotropic abnormalities although the neuronal tissues appeared normal, suggesting the presence of gene (s) compensating the bcl-2 deficiency.Although the biochemical basis of the bcl-2 fucntion remains unknown, a mechanism has been proposed and widely accepted, that involves bcl-2 activity on reactive oxygen species (ROS), we find that expression of bcl-2 prevents cell death induced by withdrawal of oxygen (anoxia), which drastically decreases the net formation of oxygen free radicals. Furthermore, neither ROS scavenger nor inhibitor of ROS scavenger affects the cell death, regardless of the expression of bcl-2. Thus, our data suggest that bcl-2 exerts an anti-cell death function by a mechanism other than through regulation of ROS activity.