The role of neurofilament and mitochondria in the neuronal cell death

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We analyzed how neurofilament and mitochondria were altered biochemically as well as morphologically when neuronal cells were degenerated or showed apoptosis, and also how these organelles are associated with such changes of neuronal cells. We used neurons from jimpy and shiverer mutant mice, the model animals for human neurodegenerative diseases, and mice in which NF-H LacZ gene in transfected, and differentiated PC12 cells. In the jimpy mice, in which central axons were dysmyelinated, NFs in the axons were more numerous and irregular and less crossbridged than those in the wild-type control mice. NF-H and NF-M mRNAs were expressed much highly in the jimpy, and more importantly, most increased-axonal NF-H, and also probably NF-M that was not examined in this study, was nonphosphorylated. Thus, because of the absence of the myelin sheath, the disorganized NFs in jimpy axons may be brought about by such abnormal expression and Phosphorylation degree of NF proteins. Concerning the mitoch … More ondria, we found large-expanded mitochondria in NF almost-deficient thin axons of NF-H LacZ gene transfected mice and less-numerous-NF axons in old shiverer mice. Bcl-2 protein in these large-sized mitochondria in the NF-HlacZ transfected mice appeared to increase in amount, which may arrest axonal degeneration shown by impairment of the transport mechanism due to the abnormal accumulation of vesicular structures. This was also supported by the fact that there was no functional change in skeletal cells in these mice, suggesting these mitochondria as well as absence of NF proteins, especially of NF-H, resist the axonal degeneration. In the differentiated PC12 cells, which showed apoptotic change by serum deprivation, Bcl-2 in their mitochondria moved into cytoplasm and/or smooth endoplasmic reticulum, and more importantly, from inner mitochondrial membranes to the outer membranes. In conclusion, when the neuronal cells are degenerating or dying, NFs are disorganized and mitochondria lack Bcl-2 in their inner membranes. Less