Role of proteasomes in the formation of neurofilamentous inclusions in spinal motor neurons of aluminum-treated rabbits.
We examined the role of the 20S proteasome in pathologic changes, including abnormal aggregation of phosphorylated neurofilaments, of spinal motor nerve cells from aluminum-treated rabbits. Immunohistochemistry for the 20S proteasome revealed that many lumbar spinal motor neurons without intracytoplasmic neurofilamentous inclusions or with small inclusions were more intensely stained in aluminum-treated rabbits than in controls, whereas the immunoreactivity was greatly decreased in some enlarged neurons containing large neurofilamentous inclusions. Proteasome activity in whole spinal cord extracts was significantly increased in aluminum-treated rabbits compared with controls. Furthermore, Western blot analysis indicated that the 20S proteasome degraded non-phosphorylated high molecular weight neurofilament (neurofilament-H) protein in vitro. These results suggest that aluminum does not inhibit 20S proteasome activity, and the 20S proteasome degrades neurofilament-H protein. We propose that abnormal aggregation of phosphorylated neurofilaments is induced directly by aluminum, and is not induced by the proteasome inhibition in the aluminum-treated rabbits. Proteasome activation might be involved in intracellular proteolysis, especially in the earlier stages of motor neuron degeneration in aluminum-treated rabbits.
Kimura
Noriyuki
N
Department of Neurology and Neuromuscular Disorders, Oita University, Faculty of Medicine, Oita, Japan. noriyuki@med.oita-u.ac.jp
Kumamoto
Toshihide
T
Ueyama
Hidetsugu
H
Horinouchi
Hideo
H
Ohama
Eisaku
E
D000535:Aluminum / Q000633:toxicity*; D000818:Animals; D015153:Blotting, Western; D007150:Immunohistochemistry; D002479:Inclusion Bodies / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D016900:Neurofilament Proteins / Q000187:drug effects / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D016900:Neurofilament Proteins; D000535:Aluminum; D046988:Proteasome Endopeptidase Complex