|Budget Amount *help
¥12,300,000 (Direct Cost: ¥12,300,000)
Fiscal Year 1998: ¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 1997: ¥7,700,000 (Direct Cost: ¥7,700,000)
In normal rat sciatic nerve, the solubility of neurofilament subunit H(NF-H) is almost constant(about 20%) irrespective of the distance from the cell body. In injured nerve, neurofilament protein distal to the injured site disappears by 1 week after injury by Wallerian degeneration of the axon. The solubility of NF-H is high in the newly regenerating axon, and the phosphorylation in its C-terminal region is low. In contrast, the analysis of neurofilament dynamics in proximal portion to the injured site by labeling with axonal transport reveals the relative decrease of NF-L amount in parallel with the increase of NF-H solubility. The closer to the cell body, the greater its change is. These results suggest that the structure and stability of neurofilament is also regulated by selective release of NF-H subunit in addition to ordinary polymerization-depolymerization change controlled by phosphorylation-dephosphorylation of its N terminal region.
Axonal micotubules are characterized by the
high proportion of cold stable subpopulation. To elucidate the molecular mechanism of their stabilization, stable microtubules within the neurites of cultured rat dorsal root ganglion cells are directly observed by video-enhanced contrast differential interference microscope, and the following results are obtained.
1. After exposing neuritic microtules by lysing plasma membrane, a small population remains polymerized for more than 30min. The proportion of these stabilized microtubules in neurites I week after plating is less than 10%.
2. Stable microtubules starts depolymerizing from both ends immediately after cutting with laser beam, suggesting that they are not stabilized along entire length.
3. When curved microtubule is transected, it springs straight, indicating that the microtubules are forced to be curved.
4. In the course of depolymerization of stable microtubule after transection, it often halts for a while at a point of attached granular structure. In .some cases halting may occur such a point without any visible structure. These stop points are considered to be the locations of microtubile stabilization, and the analysis about molecular mechanism of stabilization is now under progress. Less