Neuromelanin inhibits enzymatic activity of 26S proteasome in human dopaminergic SH-SY5Y cells.
Recently, impairment of the ubiquitin-proteasome system is suggested to be responsible for the neuronal death in ageing and Parkinson's disease. The specific degeneration of dopamine neurons containing neuromelanin (NM) suggests that NM itself may be involved in the cellular dysfunction and death, even though the direct link has never been reported. We examined the effects of NM isolated from the human substantia nigra on the proteasome activity in human dopaminergic SH-SY5Y cells. NM reduced the activities of 26S proteasome, as shown in situ using a green fluorescent protein homologue targeted to 26S proteasome and also in vitro using ubiquitinated lysozyme as a substrate. However, NM did not affect 20S proteasome activity in vitro. NM reduced the amount of PA700 regulatory subunit of 26S proteasome, but did not affect that of alpha- and beta-subunits of 20S proteasome. These results suggest that NM may inhibit the ubiquitin-26S proteasome system, and determine the selective vulnerability of dopamine neurons in ageing and related disorders.
Shamoto-Nagai
M
M
Section of Biochemistry, Department of Mechanism of Ageing, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan.
Maruyama
W
W
Akao
Y
Y
Osawa
T
T
Tribl
F
F
Gerlach
M
M
Zucca
F A
FA
Zecca
L
L
Riederer
P
P
Naoi
M
M
D000328:Adult; D000375:Aging / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D002918:Chymotrypsin / Q000378:metabolism; D004298:Dopamine / Q000502:physiology*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008543:Melanins / Q000494:pharmacology*; D008858:Microscopy, Phase-Contrast; D009113:Muramidase / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000378:metabolism; D010300:Parkinson Disease / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D013050:Spectrometry, Fluorescence; D025801:Ubiquitin / Q000502:physiology
D008543:Melanins; D061988:Proteasome Inhibitors; D025801:Ubiquitin; C014121:neuromelanin; D049452:Green Fluorescent Proteins; D009113:Muramidase; D002918:Chymotrypsin; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D009955:Ornithine Decarboxylase; D004298:Dopamine