ARMc8 (armadillo-repeat-containing protein 8) is a key component of the CTLH (C-terminal to lissencephaly type-1-like homology motif) complex in mammalian cells. This complex is well conserved in Saccharomyces cerevisiae and has been characterized as a FBPase (fructose-1, 6-bisphosphatase)-degrading complex. The yeast homologue of ARMc8, Gid (glucose-induced degradation) 5p, plays an essential role in the ubiquitin- and proteasome-dependent degradation of FBPase. To elucidate the function of ARMc8, we used a yeast two-hybrid system to screen a human skeletal muscle cDNA library. α-Catenin was isolated as a binding protein of ARMc8α. This association was confirmed by co-immunoprecipitation assay using MDCK (Madin–Darby canine kidney) cells in which exogenous α-catenin and ARMc8α were overexpressed. The association was also confirmed by co-immunoprecipitation assay using endogenous proteins in untransfected MDCK cells. We then used immunofluorescence microscopy of MDCK cells and C2C12 cells to investigate the intracellular distribution of ARMc8. Exogenously expressed ARMc8 was co-localized with α-catenin and β-catenin along the cell membrane, suggesting an association between α-catenin and ARMc8 in the cells. To compare the binding domain of α-catenin with ARMc8α with that of β-catenin, we performed a co-immunoprecipitation assay, again using 5′- and 3′-deletion constructs of α-catenin. The N-terminal sequence (amino acids 82–148) of α-catenin was sufficient to bind to both ARMc8α and β-catenin. Next, we investigated the proteasome-dependent degradation of α-catenin by immunoblotting using proteasome inhibitors. Co-expression of ARMc8α with α-catenin resulted in rapid degradation of the exogenous α-catenin. Furthermore, ARMc8 knockdown inhibited α-catenin degradation and prolonged the half-life of α-catenin. We conclude that ARMc8α associates with α-catenin and up-regulates its degradation.
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Research Article|
April 14 2008
Proteasome-dependent degradation of α-catenin is regulated by interaction with ARMc8α
Takeyuki Suzuki;
Takeyuki Suzuki
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Atsuhisa Ueda;
Atsuhisa Ueda
1
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
1To whom correspondence should be addressed (email aueda@med.yokohama-cu.ac.jp).
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Nobuaki Kobayashi;
Nobuaki Kobayashi
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Jun Yang;
Jun Yang
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Koji Tomaru;
Koji Tomaru
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Masaki Yamamoto;
Masaki Yamamoto
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Mitsuhiro Takeno;
Mitsuhiro Takeno
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Yoshiaki Ishigatsubo
Yoshiaki Ishigatsubo
1Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Publisher: Portland Press Ltd
Received:
September 24 2007
Revision Received:
January 15 2008
Accepted:
January 17 2008
Accepted Manuscript online:
January 17 2008
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem J (2008) 411 (3): 581–591.
Article history
Received:
September 24 2007
Revision Received:
January 15 2008
Accepted:
January 17 2008
Accepted Manuscript online:
January 17 2008
Citation
Takeyuki Suzuki, Atsuhisa Ueda, Nobuaki Kobayashi, Jun Yang, Koji Tomaru, Masaki Yamamoto, Mitsuhiro Takeno, Yoshiaki Ishigatsubo; Proteasome-dependent degradation of α-catenin is regulated by interaction with ARMc8α. Biochem J 1 May 2008; 411 (3): 581–591. doi: https://doi.org/10.1042/BJ20071312
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