Molecular mechanism of the initial process of neuronal aging.-perturbation in transport and polymerization-depolymerization dynamics of axonal cytoskeleton.

点击翻译按钮获取中文摘要

Studies on the regulatory mechanism of polymerization-depolymerization and transport of axonal neurofilament was carried out and the following new findings were obtained.1).Within 24 hours after intra-peritoneal injection of beta, beta'-iminodipropionitrile (IDPN), phosphorylation of NF-H subunit (apparent molecular weight 200,000) was transiently decreased in the rat sciatic motor axons. This is earlier than the first appearance of neurological symptoms caused by IDPN (about 3 days after injection), and than the disturbance of neurofilament transport within the motor axons of IDPN-treated rat (about 1-2 days after injection).2).When preparation was performed in the presence of phosphatase inhibitors, the solubility of NF-H after treatment with the buffer containing 1% Triton-100 was increased to about 20% of the total, compared to that in the absence of those inhibitors. In contrast NF-L subunit (apparent molecular weight 68,000) remained insoluble irrespective of the presence or absence of phosphatase inhibitors.When N-terminal domain of NF-H was phosphorylated by c-AMP-dependent protein kinase in vitro, it was solubilized together with NF-L subunit, suggesting depolymerization of whole neurofilament.When axonal neurofilaments were labeled and their transport was analyzed, solubility of NF-H was minimum at the peak of transport of labeled neurofilament protein, and maximum at the leading edge and the tail of the transport, suggesting the close association between transported form of neurofilament and solubility of NF-H.