Proteasome inhibition induces inclusion bodies associated with intermediate filaments and fragmentation of the Golgi apparatus.
The ubiquitin-proteasome system is involved in a variety of biological processes. Inclusion bodies associated with intermediate filaments (IFs) and ubiquitin are observed in various diseases; however, the precise mechanisms of formation and the pathological significance of inclusion bodies have not been fully understood. We examined the effect of proteasome inhibitors on the structure of IF using anti-cytokeratin antibodies or transfection of green fluorescent protein-fused cytokeratin 18 in a hepatoma cell line, Huh7. Intracellular organelles were visualized by immunofluorescent and electron microscopies. Proteasome inhibitors induced IF inclusions associated with ubiquitin. Electron microscopic examination revealed inclusion bodies surrounded by filamentous structures. Autophagic vacuoles and lysosomes were frequently observed, and the organization of the Golgi apparatus was disrupted in these cells. After the removal of the proteasome inhibitors, the IF network and organization of the Golgi apparatus were restored. The IF inclusions could be induced by inhibition of the proteasome function. IF inclusions induced fragmentation of the Golgi apparatus and might inhibit the function of this important station of membrane traffic. The IF inclusions disappeared by restoring proteasome function, and autophagy and lysosomal degradation might be, at least in part, associated with the elimination of inclusion bodies.
Harada
Masaru
M
Second Department of Medicine and Research Center for Innovative Cancer Therapy, Kurume University School of Medicine, 67 Asahi-machi, Kurume 830-0011, Japan. harada@med.kurume-u.ac.jp
Kumemura
Hiroto
H
Omary
M Bishr
MB
Kawaguchi
Takumi
T
Maeyama
Noriko
N
Hanada
Shinichiro
S
Taniguchi
Eitaro
E
Koga
Hironori
H
Suganuma
Tatsuo
T
Ueno
Takato
T
Sata
Michio
M
D001343:Autophagy; D003546:Cysteine Endopeptidases; D006056:Golgi Apparatus / Q000187:drug effects* / Q000648:ultrastructure; D006801:Humans; D002479:Inclusion Bodies / Q000187:drug effects*; D007382:Intermediate Filaments / Q000187:drug effects* / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D014407:Tumor Cells, Cultured
D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex