TY - JOUR
T1 - Bag-1 p50 isoform interacts with the vitamin D receptor and its cellular overexpression inhibits the vitamin D pathway
AU - Witcher, Michael
AU - Yang, Xiaolong
AU - Pater, Alan
AU - Tang, Shou Ching
N1 - Funding Information:
(OS)VDREtkCAT VDRE expression plasmid was a generous gift from S. Christakos and pCMX-hVDR plasmid containing human VDR cDNA was a generous gift from R. Evans. The investigation was supported by grants from the Medical Research Council of Canada, the National Cancer Institute of Canada with funds from the Canadian Cancer Society, and the Newfoundland Cancer Treatment and Research Foundation.
PY - 2001/4/15
Y1 - 2001/4/15
N2 - Human BAG-1 is an anti-apoptotic protein with four protein isoforms (BAG-1 p50, p46, p33, and p29). BAG-1 p46 was originally isolated in a screen for proteins binding to the glucocorticoid receptor; it binds and modulates the action of several members of the nuclear steroid hormone receptor superfamily. The vitamin D receptor (VDR) is another member of this superfamily, and the vitamin D pathway is important for prevention and therapy of osteoporosis, renal failure, cancer, and psoriasis. Therefore, we investigated the effect of the recently isolated BAG-1 p50 on the vitamin D pathway. By use of Far Western blot analysis and glutathione S-transferase BAG-1 p50 binding assays, BAG-1 p50 was demonstrated to interact with the VDR, and the BAG-1 p50 N-terminus was required. In U87 cells that were stably transfected with BAG-1 p50, binding of the VDR to its response element in electrophoretic mobility shift assays was blocked, enhancement of transcriptional activation was inhibited, cell growth rate was enhanced, cell growth inhibition induced by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was blocked, and 1,25(OH)2D3-mediated VDR induction was inhibited. These results suggest that BAG-1 p50 is a novel regulator of the vitamin D signaling pathway, and its overexpression may lead to cellular resistance to 1,25(OH)2D3 therapy.
AB - Human BAG-1 is an anti-apoptotic protein with four protein isoforms (BAG-1 p50, p46, p33, and p29). BAG-1 p46 was originally isolated in a screen for proteins binding to the glucocorticoid receptor; it binds and modulates the action of several members of the nuclear steroid hormone receptor superfamily. The vitamin D receptor (VDR) is another member of this superfamily, and the vitamin D pathway is important for prevention and therapy of osteoporosis, renal failure, cancer, and psoriasis. Therefore, we investigated the effect of the recently isolated BAG-1 p50 on the vitamin D pathway. By use of Far Western blot analysis and glutathione S-transferase BAG-1 p50 binding assays, BAG-1 p50 was demonstrated to interact with the VDR, and the BAG-1 p50 N-terminus was required. In U87 cells that were stably transfected with BAG-1 p50, binding of the VDR to its response element in electrophoretic mobility shift assays was blocked, enhancement of transcriptional activation was inhibited, cell growth rate was enhanced, cell growth inhibition induced by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was blocked, and 1,25(OH)2D3-mediated VDR induction was inhibited. These results suggest that BAG-1 p50 is a novel regulator of the vitamin D signaling pathway, and its overexpression may lead to cellular resistance to 1,25(OH)2D3 therapy.
KW - BAG-1 p50 isoform
KW - Binding
KW - Cell growth
KW - U87 glioblastoma cells
KW - Vitamin D
KW - Vitamin D receptor
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U2 - 10.1006/excr.2001.5176
DO - 10.1006/excr.2001.5176
M3 - Article
C2 - 11281654
AN - SCOPUS:0035870119
SN - 0014-4827
VL - 265
SP - 167
EP - 173
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 1
ER -