C-terminal Hsp-interacting protein slows androgen receptor synthesis and reduces its rate of degradation.
The androgen receptor (AR) is a member of the nuclear receptor superfamily that requires the action of molecular chaperones for folding and hormone binding. C-terminal Hsp-interacting protein (Chip) is a cochaperone that interacts with Hsp70 and Hsp90 molecular chaperones via a tetratricopeptide domain and inhibits chaperone-dependent protein folding in vitro. Chip also stimulates protein degradation by acting as an E3 ubiquitin ligase via a modified ring finger domain called a U box. We analyzed whether Chip affected AR levels using a transient transfection strategy. Chip overexpression led to a large decrease in AR steady state levels and increased levels of AR ubiquitinylation. However, Chip effects were not fully reversed by proteasome inhibitors, suggesting that mechanisms alternative to or in addition to proteasome-mediated degradation were involved. This hypothesis was supported by the finding that Chip overexpression reduced the rate of AR degradation, consistent with an effect on AR folding, perhaps leading to aggregation. The possibility that Chip affected AR folding was further supported by the finding that the effects of exogenous Chip were reproduced by a mutant lacking the U box. These results are discussed in terms of the role played by molecular chaperones in AR biogenesis.
Cardozo
Christopher P
CP
Department of Medicine, Mount Sinai School of Medicine, Box 1232, One Gustave L. Levy Place, New York, NY 10029, USA. chris.cardozo@mssm.edu
Michaud
Charlene
C
Ost
Michael C
MC
Fliss
Albert E
AE
Yang
Emy
E
Patterson
Cam
C
Hall
Simon J
SJ
Caplan
Avrom J
AJ
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016227:Benzoquinones; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000378:metabolism / Q000494:pharmacology; D015870:Gene Expression; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic; D007976:Leupeptins / Q000494:pharmacology; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D008297:Male; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011809:Quinones / Q000494:pharmacology; D011944:Receptors, Androgen / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D016227:Benzoquinones; D015853:Cysteine Proteinase Inhibitors; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D007976:Leupeptins; D018832:Molecular Chaperones; D009097:Multienzyme Complexes; D011809:Quinones; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D025801:Ubiquitin; D013196:Dihydrotestosterone; C067713:lactacystin; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008025:Ligases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine; C001277:geldanamycin