Human testicular orphan receptor 4 enhances thyroid hormone receptor signaling.
The thyroid hormone receptor (TR) and human testicular orphan receptor 4 (TR4) belong to the nuclear hormone receptor superfamily. They are ligand-dependent transcription factors. TR and TR4 bind to a similar thyroid response element (TRE), known as a direct repeat with four nucleotide spacing (DR4). This study examined the possible interaction or cross-talking between those two receptors. We hypothesized that protein-protein interaction between TR4 and TR may promote TR-mediated transcriptional activity. Glutathione S-transferase pull-down and immunoprecipitation assays showed direct interaction between TR and TR4. Electrophoretic mobility-shift assay demonstrated that TR and TR4 could co-occupy the same TRE. The interaction between TR4 and TR may enhance regulation of genes targeted by TR, such as furin, fibrinogen, cdk2 and p21 expression. We found that TR4 function is similar with TR as TR4 alone could regulate expression of some TR target genes, and could increase cell migration or inhibit cell proliferation. Importantly, the TR-dependent inhibition of cell proliferation and stimulation of cell migration are more enhanced in the HepG2-TR cells stably over-expressing TR4. Overall, TR4 not only has modulation abilities similar to TR but also can cross-talk with TR and promote the TR signaling pathway.
Department of Biochemistry, School of Medicine, Chang-Gung University, Taoyuan, Taiwan, Republic of China.
Ya-Hui
YH
Huang
Chen-Hsin
CH
Liao
Ruey-Nan
RN
Chen
Chia-Jung
CJ
Liao
Kwang-Huei
KH
Lin
D000818:Animals; D002460:Cell Line; D002465:Cell Movement; D049109:Cell Proliferation; D024202:Electrophoretic Mobility Shift Assay; D045683:Furin / Q000235:genetics; D000882:Haplorhini; D006801:Humans; D047468:Immunoprecipitation; D008024:Ligands; D008297:Male; D057125:Nuclear Receptor Subfamily 2, Group C, Member 2 / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020239:Receptor Cross-Talk; D020218:Response Elements; D015398:Signal Transduction / Q000235:genetics; D037021:Thyroid Hormone Receptors alpha / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015533:Transcriptional Activation; D014162:Transfection; D014284:Triiodothyronine / Q000378:metabolism
D008024:Ligands; D057125:Nuclear Receptor Subfamily 2, Group C, Member 2; D037021:Thyroid Hormone Receptors alpha; D014284:Triiodothyronine; D045683:Furin