Signal transduction of receptor-mediated antiproliferative action of melatonin on human prostate epithelial cells involves dual activation of Gα(s) and Gα(q) proteins.
Melatonin has been shown to inhibit the proliferation of malignant and transformed human prostate epithelial cells by transcriptional up-regulation of p27(Kip1) expression via MTNR1A receptor-mediated activation of protein kinase A (PKA) and protein kinase C (PKC) in parallel. Given that melatonin MTNR1A receptor is a G protein-coupled receptor, this study was conducted to identify the specific G proteins that mediate the antiproliferative action of melatonin on human prostate epithelial cells. In 22Rv1 and RWPE-1 cells, knockdown of either Gα(s) or Gα(q) , but not Gα(i2) expression by RNA interference, abrogated the effects of melatonin on p27(Kip1) and cell proliferation. Conversely, cellular overexpression of activated mutants of Gα(s) and Gα(q) in 22Rv1 and RWPE-1 cells mimicked the effects of melatonin on prostate epithelial cell antiproliferation by increasing p27(Kip1) expression through downstream activation of PKA and PKC in parallel. Moreover, melatonin or 2-iodomelatonin induced elevation of adenosine-3',5'-cyclic monophosphate (cAMP) in 22Rv1 and RWPE-1 cells. The effects of 2-iodomelatonin on cAMP were blocked by the nonselective MTNR1A/MTNR1B receptor antagonist luzindole but were not affected by the selective MTNR1B receptor antagonist 4-phenyl-2-propionamidotetraline (4-P-PDOT). Furthermore, knockdown of Gα(s) mitigated the stimulatory effects of 2-iodomelatonin on cAMP. Collectively, the data demonstrated, for the first time, functional coupling of MTNR1A receptor to Gα(s) in cancerous or transformed human cells expressing endogenous melatonin receptors. Our results also showed that dual activation of Gα(s) and Gα(q) proteins is involved in the signal transduction of MTNR1A receptor-mediated antiproliferative action of melatonin on human prostate epithelial cells.
Shiu
Stephen Y W
SY
Department of Physiology, The University of Hong Kong, Hong Kong, China. sywshiu@hkucc.hku.hk
Pang
Bo
B
Tam
Chun W
CW
Yao
Kwok-Ming
KM
D000975:Antioxidants / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics / Q000378:metabolism*; D052161:Human papillomavirus 18 / Q000235:genetics; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D034622:RNA Interference; D011863:Radioimmunoassay; D044094:Receptors, Melatonin / Q000037:antagonists & inhibitors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014363:Tryptamines / Q000494:pharmacology
C114459:4-phenyl-2-propionamidotetraline; D000975:Antioxidants; D044094:Receptors, Melatonin; D013764:Tetrahydronaphthalenes; D014363:Tryptamines; C057154:luzindole; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051960:GTP-Binding Protein alpha Subunit, Gi2; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019205:GTP-Binding Protein alpha Subunits, Gs; D008550:Melatonin