Regions of the peripheral nervous system are capable of extensive spontaneous regeneration following injury. It has recently been found that synthesis of two polyamines, putrescine and spermidine, increases following injury of the superior cervical ganglion (SCG). Furthermore, spermidine has been shown to promote outgrowth of neurites in the PC12 cell model of sympathetic neurons, suggesting a possible involvement in the regenerative process. In the work supported by this proposal, the molecular mechanisms that underlie the ability of spermidine to promote outgrowth will be investigated. Specifically, the ability of spermidine to alter the activation state of members of the Rho family of GTPases will be examined; this family of proteins is involved in cell shape changes. Since regeneration in the central nervous system (CNS) is inhibited, in part, by myelin-associated glycoprotein (MAG), the ability of spermidine to promote neurite outgrowth from PC12 cells grown on this normally inhibitory substrate will be tested. Finally, the involvement of the Rho GTPases in the spontaneous regeneration that occurs following injury of the SCG will be investigated. The nerves exiting the SCG in adult male rats will be transected, and the activation states of the Rho GTPases will subsequently be analyzed. Together, these studies are intended to elucidate the molecular pathway by which spermidine promotes neurite outgrowth in vitro (in the PC12 cells) as well as to uncover a similar function during spontaneous regeneration of the adult rat SCG in vivo.
The proposed work will provide educational opportunities for undergraduate students, allowing them to participate in an active research environment beyond the scope of typical classroom or laboratory instruction. Students will be able to address questions within the realm of neurobiology while learning techniques of cell and molecular biology. Such opportunities will further prepare students for research careers and for graduate school.
