TY - JOUR
T1 - Proteasome-mediated degradation of the vitamin D receptor (VDR) and a putative role for SUG1 interaction with the AF-2 domain of VDR
AU - Masuyama, Hisashi
AU - MacDonald, Paul N.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1998/12/1
Y1 - 1998/12/1
N2 - The AF-2 helix of nuclear receptors is essential for ligand-activated transcription, and it may function to couple the receptor to transcriptional coactivator proteins. This domain also contacts components of the proteasome machinery, suggesting that nuclear receptors may be targets for proteasome- mediated proteolysis. In the present study, we demonstrate that mSUG1 (P45), a component of the 265 proteasome, interacts in a 1,25-(OH)2D3-dependent manner with the AF-2 domain of the vitamin D receptor (VDR). Furthermore, treatment of ROS 17/2.8 osteosarcoma cells with the proteasome inhibitors MG132 or β-lactone increased steady-state levels of the VDR protein. In the presence cycloheximide (10 μg/ml), the liganded VDR protein was degraded with a half-life of approximately 8 h, and this rate of degradation was completely blocked by 0.05 mM MG132. The role of SUG1-VDR interaction in this process was investigated in transient expression studies. Overexpression of wild-type mSUG1 in ROS17/2.8 cells generated a novel proteolytic VDR fragment of approximately 50 kDa, and its production was blocked by proteasome inhibitors or by a nonhydrolyzable ATP analog. Parallel studies with SUG1 (K196H), a mutant that does not interact with the VDR, did not produce the 50 kDa VDR fragment. Functionally, expression of SUG1 in a VDR-responsive reporter gene assay resulted in a profound inhibition of 1,25-(OH)2D3- activated transcription, while expression of SUG1(K196H) had no significant effect in this system. These data show that the AF-2 domain of VDR interacts with SUG1 in a 1,25-(OH)2D3-dependent fashion and that this interaction may target VDR to proteasome-mediated degradation as a means to down-regulate the 1,25-(OH)2D3-activated transcriptional response.
AB - The AF-2 helix of nuclear receptors is essential for ligand-activated transcription, and it may function to couple the receptor to transcriptional coactivator proteins. This domain also contacts components of the proteasome machinery, suggesting that nuclear receptors may be targets for proteasome- mediated proteolysis. In the present study, we demonstrate that mSUG1 (P45), a component of the 265 proteasome, interacts in a 1,25-(OH)2D3-dependent manner with the AF-2 domain of the vitamin D receptor (VDR). Furthermore, treatment of ROS 17/2.8 osteosarcoma cells with the proteasome inhibitors MG132 or β-lactone increased steady-state levels of the VDR protein. In the presence cycloheximide (10 μg/ml), the liganded VDR protein was degraded with a half-life of approximately 8 h, and this rate of degradation was completely blocked by 0.05 mM MG132. The role of SUG1-VDR interaction in this process was investigated in transient expression studies. Overexpression of wild-type mSUG1 in ROS17/2.8 cells generated a novel proteolytic VDR fragment of approximately 50 kDa, and its production was blocked by proteasome inhibitors or by a nonhydrolyzable ATP analog. Parallel studies with SUG1 (K196H), a mutant that does not interact with the VDR, did not produce the 50 kDa VDR fragment. Functionally, expression of SUG1 in a VDR-responsive reporter gene assay resulted in a profound inhibition of 1,25-(OH)2D3- activated transcription, while expression of SUG1(K196H) had no significant effect in this system. These data show that the AF-2 domain of VDR interacts with SUG1 in a 1,25-(OH)2D3-dependent fashion and that this interaction may target VDR to proteasome-mediated degradation as a means to down-regulate the 1,25-(OH)2D3-activated transcriptional response.
KW - 1,25-(OH)D
KW - AF-2 domain
KW - Proteasome
KW - SUG 1
KW - VDR
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U2 - 10.1002/(SICI)1097-4644(19981201)71:3<429::AID-JCB11>3.0.CO;2-P
DO - 10.1002/(SICI)1097-4644(19981201)71:3<429::AID-JCB11>3.0.CO;2-P
M3 - Article
C2 - 9831079
AN - SCOPUS:0032404015
VL - 71
SP - 429
EP - 440
JO - Journal of supramolecular structure and cellular biochemistry
JF - Journal of supramolecular structure and cellular biochemistry
SN - 0730-2312
IS - 3
ER -