Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 429-440 |
| Number of pages | 12 |
| Journal | Journal of Cellular Biochemistry |
| Volume | 71 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Dec 1 1998 |
| Externally published | Yes |
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Keywords
- 1,25-(OH)D
- AF-2 domain
- Proteasome
- SUG 1
- VDR
ASJC Scopus subject areas
- Biochemistry
- Cell Biology
Cite this
Proteasome-mediated degradation of the vitamin D receptor (VDR) and a putative role for SUG1 interaction with the AF-2 domain of VDR. / Masuyama, Hisashi; MacDonald, Paul N.
In: Journal of Cellular Biochemistry, Vol. 71, No. 3, 01.12.1998, p. 429-440.Research output: Contribution to journal › Article
}
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.
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
UR - http://www.scopus.com/inward/record.url?scp=0032404015&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032404015&partnerID=8YFLogxK
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 Cellular Biochemistry
JF - Journal of Cellular Biochemistry
SN - 0730-2312
IS - 3
ER -