GnRH-mediated DAN production regulates the transcription of the GnRH receptor in gonadotrope cells.
The primary function of gonadotropin-releasing hormone (GnRH) is the regulation of pituitary gonadotropin hormone gene transcription, biosynthesis and release. These effects are mediated through intracellular mobilization of Ca2+ and activation of PKC isoforms and MAP kinases. We show here that DAN (differential screening-selected gene aberrative in neuroblastoma) which is a secreted bone morphogenic protein (BMP) antagonist belonging to the TGFbeta protein superfamily, is controlled by GnRH in murine gonadotrope cells. Acute GnRH stimulation induced a rapid, 27-fold, elevation of DAN mRNA, accompanied by an approximate 3-fold increase in the amount of mature DAN glycoprotein in the cell cytoplasm and in DAN secretion into the culture medium. Incubation of L beta T2 cells in DAN-containing medium altered the levels of a number of cellular proteins. Two of these were identified as the steroidogenic acute regulatory protein (StAR) and the actin-related protein 2/3 complex subunits 2 (p34-ARC) which are primarily involved in steroidogenesis and cytoskeleton remodelling, respectively. DAN caused an approximate 2-fold specific elevation in the cytoplasmic levels of both these proteins in L beta T2 cells. We further tested the effects of DAN on classical GnRH effects viz. gonadotropin and GnRH receptor gene expression. Co-transfection of L beta T2 cells with DAN and gonadotropin subunit promoter luciferase reporter genes had no effect on GnRH stimulation of alpha GSU and LH beta or on the additive GnRH and activin induction of FSH beta subunit transcription. However, co-transfection of DAN markedly inhibited the synergistic activation of GnRH and activin on GnRH receptor gene expression thus implicating DAN as a novel autocrine/paracrine factor that modulates GnRH function in pituitary gonadotropes.
López de Maturana
Rakel
R
MRC Human Reproductive Sciences Unit, Centre for Human Reproductive Biology, Edinburgh, EH16 4SB, UK.
Martin
Bronwen
B
Millar
Robert P
RP
Brown
Pamela
P
Davidson
Lindsay
L
Pawson
Adam J
AJ
Nicol
Moira R
MR
Mason
J Ian
JI
Barran
Perdita
P
Naor
Zvi
Z
Maudsley
Stuart
S
D051376:Actin-Related Protein 2-3 Complex / Q000096:biosynthesis; D028341:Activins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019898:Autocrine Communication; D019556:COS Cells; D018797:Cell Cycle Proteins; D002460:Cell Line; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D019899:Paracrine Communication; D010750:Phosphoproteins / Q000096:biosynthesis; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000096:biosynthesis; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011966:Receptors, LHRH / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D000098682:Steroidogenic Acute Regulatory Protein
D051376:Actin-Related Protein 2-3 Complex; D018797:Cell Cycle Proteins; C490089:Nbl1 protein, mouse; D010750:Phosphoproteins; D021122:Protein Subunits; D011506:Proteins; D012333:RNA, Messenger; D011966:Receptors, LHRH; D000098682:Steroidogenic Acute Regulatory Protein; D028341:Activins; D007987:Gonadotropin-Releasing Hormone