C-terminal Hsp-interacting protein slows androgen receptor synthesis and reduces its rate of degradation

CP Cardozo, C Michaud, MC Ost, AE Fliss… - Archives of biochemistry …, 2003 - Elsevier
CP Cardozo, C Michaud, MC Ost, AE Fliss, E Yang, C Patterson, SJ Hall, AJ Caplan
Archives of biochemistry and biophysics, 2003Elsevier
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 …
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.
Elsevier