Transforming growth factor beta-activated kinase 1 is a key mediator of ovine follicle-stimulating hormone beta-subunit expression.
FSH, a key regulator of gonadal function, contains a beta-subunit (FSHbeta) that is transcriptionally induced by activin, a member of the TGFbeta-superfamily. This study used 4.7 kb of the ovine FSHbeta-promoter linked to luciferase (oFSHbetaLuc) plus a well-characterized activin-responsive construct, p3TPLuc, to investigate the hypothesis that Smad3, TGFbeta-activated kinase 1 (TAK1), or both cause activin-mediated induction of FSH. Overexpression of either Smad3 or TAK1 induced oFSHbetaLuc in gonadotrope-derived LbetaT2 cells as much as activin itself. Induction of p3TPLuc by activin is known to require Smad3 activation in many cell types, and this was true in LbetaT2 cells, where 10-fold induction by activin (2-8 h after activin treatment) was blocked more than 90% by two dominant negative (DN) inhibitors of Smad3 [DN-Smad3 (3SA) and DN-Smad3 (D407E)]. By contrast, 6.5-fold induction of oFSHbetaLuc by activin (10-24 h after activin treatment) was not blocked by either DN-Smad inhibitor, suggesting that activation of Smad3 did not trigger induction of oFSHbetaLuc. By contrast, inhibition of TAK1 by a DN-TAK1 construct led to a 50% decrease in activin-mediated induction of oFSHbetaLuc, and a specific inhibitor of TAK1 (5Z-7-Oxozeanol) blocked induction by 100%, indicating that TAK1 is necessary for activin induction of oFSHbetaLuc. Finally, inhibiting p38-MAPK (often activated by TAK1) blocked induction of oFSHbetaLuc by 60%. In conclusion, the data presented here indicate that activation of TAK1 (and probably p38-MAPK), but not Smad3, is necessary for triggering induction of oFSHbeta by activin.
Safwat
Nedal
N
Department of Molecular and Structural Biochemistry, Box 7622, North Carolina State University, Raleigh, North Carolina 27695-7622, USA.
Ninomiya-Tsuji
Jun
J
Gore
A Jesse
AJ
Miller
William L
WL
D028341:Activins / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D037201:Follicle Stimulating Hormone, beta Subunit / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D028322:Inhibin-beta Subunits / Q000494:pharmacology*; D007700:Kinetics; D007783:Lactones / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000494:pharmacology; D012118:Resorcinols / Q000494:pharmacology; D012756:Sheep; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099151:MAP Kinase Kinase Kinase 7; D015025:Zearalenone / Q000008:administration & dosage
D028341:Activins; D037201:Follicle Stimulating Hormone, beta Subunit; D028322:Inhibin-beta Subunits; D007783:Lactones; D008156:Luciferases; D020930:MAP Kinase Kinase Kinases; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012118:Resorcinols; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C505734:7-oxozeanol; D015025:Zearalenone; C422405:activin A; C505733:p3TPLuc protein