Grass carp activin : molecular cloning and functional role in regulating growth hormone gene expression in grass carp pituitary cells

2004 ◽  
Author(s):  
Sai-kit Fung
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Molecular Cloning ◽  
Grass Carp ◽  
Functional Role ◽  
Growth Hormone Gene ◽  
Pituitary Cells

scholarly journals Paracrine regulation of growth hormone gene expression by gonadotrophin release in grass carp pituitary cells: functional implications, molecular mechanisms and signal transduction

2005 ◽  
Vol 34 (2) ◽  
pp. 415-432 ◽  
Author(s):  
Hong Zhou ◽  
Yonghua Jiang ◽  
Wendy K W Ko ◽  
Wensheng Li ◽  
Anderson O L Wong
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Adenylate Cyclase ◽  
Mrna Expression ◽  
Grass Carp ◽  
Janus Kinase ◽  
Growth Hormone Gene ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Gh Gene

Growth hormone (GH) is known to stimulate luteinizing hormone (LH) release via paracrine interactions between somatotrophs and gonadotrophs. However, it is unclear if LH can exert a reciprocal effect to modulate somatotroph functions. Here we examined the paracrine effects of LH on GH gene expression using grass carp pituitary cells as a cell model. LH receptors were identified in grass carp somatotrophs and their activation by human chorionic gonadotropin (hCG) increased ‘steady-state’ GH mRNA levels. Removal of endogenous LH by immunoneutralization using LH antiserum inhibited GH release and GH mRNA expression. GH secretagogues, including gonadotrophin releasing hormone (GnRH), pituitary adenylate cyclase-activating polypeptide (PACAP) and apomorphine, were effective in elevating GH mRNA levels but these stimulatory actions were blocked by LH antiserum. In pituitary cells pretreated with actinomycin D, the half-life of GH mRNA was not affected by hCG but was enhanced by LH immunoneutralization. Treatment with LH antiserum also suppressed basal levels of mature GH mRNA and primary transcripts. hCG increased cAMP synthesis in carp pituitary cells and hCG-induced GH mRNA expression was mimicked by forskolin but suppressed by inhibiting adenylate cyclase and protein kinase A. Similarly, the stimulatory actions of hCG and forskolin on GH mRNA expression were blocked by inhibiting Janus kinase 2 (JAK2) and MAP kinase (MAPK), including P42/44MAPK and P38 MAPK. These results suggest that LH is essential for the maintenance of GH release, GH gene expression, and somatotroph responsiveness to GH-releasing factors. The paracrine actions of LH on GH mRNA expression are mediated by a concurrent increase in GH gene transcription and GH mRNA turnover, probably through JAK2/MAPK coupled to the cAMP-dependent pathway.

scholarly journals Endogenous retinoid X receptors can function as hormone receptors in pituitary cells.

1994 ◽  
Vol 14 (11) ◽  
pp. 7105-7110 ◽  
Author(s):  
K D Davis ◽  
T J Berrodin ◽  
J E Stelmach ◽  
J D Winkler ◽  
M A Lazar
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Ligand Binding ◽  
Hormone Receptors ◽  
Nuclear Hormone Receptors ◽  
Growth Hormone Gene ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Retinoid X Receptors ◽  
X Receptors

Retinoids regulate gene transcription by interacting with both retinoic acid (RA) receptors (RARs) and retinoid X receptors (RXRs). Since unliganded RXRs can act as heterodimerization partners for RARs and other nuclear hormone receptors, it is unclear whether ligand binding by RXRs actually regulates the expression of naturally occurring genes. To address this issue, we synthesized the RXR-selective retinoid SR11237 and confirmed its specificity in transient transfection and proteolytic susceptibility assays before using it to assess the contribution of ligand-activated RXRs to retinoid action. Unlike RAR ligands, SR11237 did not increase endogenous RAR beta mRNA levels in F9 embryonal carcinoma cells, even though it activated transcription of an RXR-responsive reporter gene in these cells. Thus, it is likely that RARs mediate the induction of RAR beta gene expression by RA. In contrast, the RXR-specific ligand induced rat growth hormone mRNA in GH3 pituitary cells, indicating that the effects of RA on growth hormone gene expression at least in part involve ligand binding to endogenous RXRs in vivo. Our results indicate that in addition to serving as cofactors for other nuclear hormone receptors, endogenous RXRs can function as ligand-dependent regulators of gene expression, i.e., classical nuclear hormone receptors.

Signaling mechanisms for α2-adrenergic inhibition of PACAP-induced growth hormone secretion and gene expression grass carp pituitary cells

2007 ◽  
Vol 292 (6) ◽  
pp. E1750-E1762 ◽  
Author(s):  
Xinyan Wang ◽  
Mable M. S. Chu ◽  
Anderson O. L. Wong
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Adenylate Cyclase ◽  
Grass Carp ◽  
Promoter Activity ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Gh Gene

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a potent growth hormone (GH)-releasing factor in lower vertebrates. However, its functional interactions with other GH regulators have not been fully characterized. In fish models, norepinephrine (NE) inhibits GH release at the pituitary cell level, but its effects on GH synthesis have yet to be determined. We examined adrenergic inhibition of PACAP-induced GH secretion and GH gene expression using grass carp pituitary cells as a cell model. Through activation of pituitary α2-adrenoreceptors, NE or the α2-agonist clonidine reduced both basal and PACAP-induced GH release and GH mRNA expression. In carp pituitary cells, clonidine also suppressed cAMP production and intracellular Ca2+ levels and blocked PACAP induction of these two second messenger signals. In GH3 cells transfected with a reporter carrying the grass carp GH promoter, PACAP stimulation increased GH promoter activity, and this stimulatory effect could be abolished by NE treatment. In parallel experiments, clonidine reduced GH primary transcript and GH promoter activity without affecting GH mRNA stability, and these inhibitory actions were mimicked by inhibiting adenylate cyclase (AC), blocking protein kinase A (PKA), removing extracellular Ca2+ in the culture medium, or inactivating L-type voltage-sensitive Ca2+ channels (VSCC). Since our recent studies have shown that PACAP can induce GH secretion in carp pituitary cells through cAMP/PKA- and Ca2+/calmodulin-dependent mechanisms, these results, taken together, suggest that α2-adrenergic stimulation in the carp pituitary may inhibit PACAP-induced GH release and GH gene transcription by blocking the AC/cAMP/PKA pathway and Ca2+ entry through L-type VSCC.

PKC and ERK are differentially involved in gonadotropin-releasing hormone-induced growth hormone gene expression in the goldfish pituitary

2005 ◽  
Vol 289 (6) ◽  
pp. R1625-R1633 ◽  
Author(s):  
Christian Klausen ◽  
Takeshi Tsuchiya ◽  
John P. Chang ◽  
Hamid R. Habibi
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Primary Cultures ◽  
Gonadotropin Releasing Hormone ◽  
Growth Hormone Gene ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Releasing Hormone ◽  
Gh Secretion ◽  
Gh Gene

Gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus and stimulates the synthesis and secretion of gonadotropin hormones. In addition, GnRH also stimulates the production and secretion of growth hormone (GH) in some fish species and in humans with certain clinical disorders. In the goldfish pituitary, GH secretion and gene expression are regulated by two endogenous forms of GnRH known as salmon GnRH and chicken GnRH-II. It is well established that PKC mediates GnRH-stimulated GH secretion in the goldfish pituitary. In contrast, the signal transduction of GnRH-induced GH gene expression has not been elucidated in any model system. In this study, we demonstrate, for the first time, the presence of novel and atypical PKC isoforms in the pituitary of a fish. Moreover, our results indicate that conventional PKCα is present selectively in GH-producing cells. Treatment of primary cultures of dispersed goldfish pituitary cells with PKC activators (phorbol ester or diacylglycerol analog) did not affect basal or GnRH-induced GH mRNA levels, and two different inhibitors of PKC (calphostin C and GF109203X) did not reduce the effects of GnRH on GH gene expression. Together, these results suggest that, in contrast to secretion, conventional and novel PKCs are not involved in GnRH-stimulated increases in GH mRNA levels in the goldfish pituitary. Instead, PD98059 inhibited GnRH-induced GH gene expression, suggesting that the ERK signaling pathway is involved. The results presented here provide novel insights into the functional specificity of GnRH-induced signaling and the regulation of GH gene expression.

Endogenous retinoid X receptors can function as hormone receptors in pituitary cells

1994 ◽  
Vol 14 (11) ◽  
pp. 7105-7110
Author(s):  
K D Davis ◽  
T J Berrodin ◽  
J E Stelmach ◽  
J D Winkler ◽  
M A Lazar
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Ligand Binding ◽  
Hormone Receptors ◽  
Nuclear Hormone Receptors ◽  
Growth Hormone Gene ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Retinoid X Receptors ◽  
X Receptors

Retinoids regulate gene transcription by interacting with both retinoic acid (RA) receptors (RARs) and retinoid X receptors (RXRs). Since unliganded RXRs can act as heterodimerization partners for RARs and other nuclear hormone receptors, it is unclear whether ligand binding by RXRs actually regulates the expression of naturally occurring genes. To address this issue, we synthesized the RXR-selective retinoid SR11237 and confirmed its specificity in transient transfection and proteolytic susceptibility assays before using it to assess the contribution of ligand-activated RXRs to retinoid action. Unlike RAR ligands, SR11237 did not increase endogenous RAR beta mRNA levels in F9 embryonal carcinoma cells, even though it activated transcription of an RXR-responsive reporter gene in these cells. Thus, it is likely that RARs mediate the induction of RAR beta gene expression by RA. In contrast, the RXR-specific ligand induced rat growth hormone mRNA in GH3 pituitary cells, indicating that the effects of RA on growth hormone gene expression at least in part involve ligand binding to endogenous RXRs in vivo. Our results indicate that in addition to serving as cofactors for other nuclear hormone receptors, endogenous RXRs can function as ligand-dependent regulators of gene expression, i.e., classical nuclear hormone receptors.

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