Distinct role and functional mode of TR3 and RARalpha in mediating ATRA-induced signalling pathway in breast and gastric cancer cells.
All-trans retinoic acid (ATRA) affects cell proliferation, differentiation and apoptosis through its receptors, RARs and RXRs. Besides these, other receptors such as orphan receptor TR3, are also involved in the regulatory process of ATRA. However, how different receptors function in response to ATRA is still largely unknown. In the present study, we found that formation of TR3/RXRalpha heterodimers in the nucleus and their subsequent translocation into the cytoplasm, in association with regulation of apoptosis-related proteins Bcl-2, Bcl-xl and Bax, was critical for apoptosis induction by ATRA in breast cancer cells MCF-7. When such translocation was blocked by Leptomycin B (LMB), ATRA-induced apoptosis was consequently abolished. However, in ATRA-induced gastric cancer cells MGC80-3, RXRalpha heterodimerised with RARalpha but not with TR3, and remained in the nucleus exerting its effect on cell cycle regulation. When transfected with antisense-RARalpha, MGC80-3 cells changed from ATRA-sensitive to ATRA-resistant and most cells were arrested in the S phase, implying the importance of RARalpha in cell cycle regulation. Furthermore, we demonstrated that the effects of ATRA depend on the relative levels of TR3, RARalpha and RXRalpha expression in cancer cells. In ATRA-induced MCF-7 cells, highly expressed TR3 favours the formation of TR3/RXRalpha and promotes the TR3/RXRalpha signalling pathway causing apoptosis; while in ATRA-induced MGC80-3 cells, high expression of RARalpha favours the formation of RARalpha/RXRalpha and promotes the RXRalpha/RARalpha signalling pathway in mediating cell cycle regulation. In conclusion, these results reveal the novel mechanism that cellular expression and location of protein is associated with diverse signalling transduction pathways and the resultant physiological process.
Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, Fujian Province, China.
Xiao feng
Xf
Ye
Qiao
Q
Wu
Su
S
Liu
Xiao feng
Xf
Lin
Bing
B
Zhang
Jia fa
Jf
Wu
Jian huai
Jh
Cai
Ming qing
Mq
Zhang
Wen jin
Wj
Su
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction / Q000187:drug effects; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D014212:Tretinoin / Q000494:pharmacology*
C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin