Co-chaperone CHIP associates with mutant Cu/Zn-superoxide dismutase proteins linked to familial amyotrophic lateral sclerosis and promotes their degradation by proteasomes.
Although the ubiquitin-proteasome system and the molecular chaperones are implicated to play an important role in pathogenesis of familial amyotrophic lateral sclerosis (FALS) caused by mutations in Cu/Zn-superoxide dismutase (SOD1), the mechanism underlying the causes of this fatal disease is still poorly understood. Here we found that co-chaperone CHIP (carboxyl terminus of Hsc70-interacting protein), together with molecular chaperones Hsc70/Hsp70 and Hsp90, associates with FALS-linked mutant SOD1 proteins in cultured human cells. S5a subunit of 26S proteasomes, which recognizes polyubiquitylated proteins, also interacts with mutant SOD1 proteins. Over-expression of CHIP leads to the reduction in cellular levels of mutant SOD1 as well as the suppression of cytotoxicity induced by mutant SOD1. Unusually, rather than increasing the level of poly-ubiquitylated SOD1, over-expressed CHIP alters the ubiquitylation pattern of mutant SOD1 proteins. Both down-regulation and ubiquitylation of mutant SOD1 are greatly reduced by a mutant CHIP protein lacking U-box domain. Taken together, these results suggest that co-chaperone CHIP, possibly with another E3 ligase(s), modulates the ubiquitylation of mutant SOD1 and renders them more susceptible for proteasomal degradation.
Choi
Jin-Sun
JS
Systemic Proteomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Taejon, Republic of Korea.
Cho
Sayeon
S
Park
Sung Goo
SG
Park
Byoung Chul
BC
Lee
Do Hee
DH
D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016923:Cell Death / Q000502:physiology; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006801:Humans; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D018832:Molecular Chaperones; D009097:Multienzyme Complexes; D025801:Ubiquitin; D013482:Superoxide Dismutase; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex