Stimulation of extracellular signal-regulated kinase by pituitary adenylate cyclase-activating polypeptide in alpha T3-1 gonadotrophs

Fowkes, Robert C.; Burch, John C.; Burrin, JM

doi:10.1677/joe.0.171r005

Cited by 23 publications

(17 citation statements)

References 24 publications

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“…It is now well established that not just cytokine and growth factor receptors but also G protein-coupled receptors can stimulate the MAPK pathway (26). We have, for example, shown that pituitary adenylate cyclase-activating polypeptide can stimulate ERK 1/2 via its G protein-coupled receptor (GPCR), stimulating phospholipase C and PKC (27), and similar effects have been demonstrated for other Gq-coupled receptors such as gonadotrophin-releasing hormone and thyrotrophin-releasing hormone (28,29). Interestingly, it has recently been demonstrated that peptides with receptors primarily working via the cAMP pathway can also activate the PKC pathway and cause activation of MAPK (30).…”

Section: Discussionmentioning

confidence: 99%

Ghrelin exerts a proliferative effect on a rat pituitary somatotroph cell line via the mitogen-activated protein kinase pathway

Nanzer

Khalaf

Mozid

et al. 2004

European Journal of Endocrinology

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127

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Objectives: Ghrelin is a brain-gut peptide with GH-releasing and appetite-inducing activities and a widespread tissue distribution. Ghrelin is the endogenous ligand of the GH secretagogue receptor type 1a (GHS-R1a), and both ghrelin and the GHS-R1a are expressed in the pituitary. There are conflicting data regarding the effects of ghrelin on cell proliferation. A positive effect on proliferation and activation of the mitogen-activated protein kinase (MAPK) pathway has been found in hepatoma, adipose, cardiomyocyte and prostate cell lines. However, ghrelin has also been shown to have antiproliferative effects on breast, lung and thyroid cell lines. We therefore examined the effect of ghrelin on the rat pituitary cell line GH3. Methods: RT-PCR was used for the detection of GHS-R1a and pre-proghrelin mRNA expression in GH3 cells. The effect of ghrelin on cell proliferation was studied using [ 3 H]thymidine incorporation; cell counting and the activation of the MAPK pathway were studied using immunoblotting and inhibitors of the extracellular signal-regulated kinase 1 and 2 (ERK 1/2), protein kinase C (PKC) and tyrosine phosphatase pathways. Results: GHS-R1a and ghrelin mRNA expression were detected in GH3 cells. Ghrelin 29 M compared with control), as well as on the cell count (control 6.8 £ 10 4^8 .7 £ 10 3 cells/ml vs desoctanoyl ghrelin (10 29 M) 1.04 £ 10 5^7 .5 £ 10 3 cells/ml; P , 0.01). Ghrelin caused a significant increase in phosphorylated ERK 1/2 in immunoblotting, while desoctanoyl ghrelin showed a smaller but also significant stimulatory effect. The positive effect of ghrelin and desoctanoyl ghrelin on [ 3 H]thymidine incorporation was abolished by the MAPK kinase inhibitor U0126, the PKC inhibitor GF109203X and the tyrosine kinase inhibitor tyrphostin 23, suggesting that the ghrelin-induced cell proliferation of GH3 cells is mediated both via a PKC-MAPK-dependent pathway and via a tyrosine kinase-dependent pathway. This could also be clearly demonstrated by Western blot analysis, where a transient increase in ERK 1/2 phosphorylation by ghrelin was attenuated by all three inhibitors. Conclusion: We have shown a novel role for ghrelin in stimulating the proliferation of a somatotroph pituitary tumour cell line, suggesting that ERK activation is involved in mediating the effects of ghrelin on cell proliferation. Desoctanoyl ghrelin showed a similar effect. As ghrelin has been shown to be expressed in both normal and adenomatous pituitary tissue, locally produced ghrelin may play a role in pituitary tumorigenesis via an autocrine/paracrine pathway.European Journal of Endocrinology 151 233-240

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Section: Discussionmentioning

confidence: 99%

Ghrelin exerts a proliferative effect on a rat pituitary somatotroph cell line via the mitogen-activated protein kinase pathway

Nanzer

Khalaf

Mozid

et al. 2004

European Journal of Endocrinology

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127

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“…In the T3-1 cell line, PACAP continues to stimulate GSU mRNA levels in the presence of PKC depletion (Tsujii et al 1995), pharmacological blockade of calcium entry (Burrin et al 1998) and inhibition of MAPK signalling (Fowkes et al 2001), all evidence that supports a role for the cAMP pathway in mediating the stimulatory transcriptional effects of PACAP on the GSU promoter. In addition, previous studies have shown that the PKA inhibitor, H-89, can attenuate the effect of PACAP on the mouse GSU promoter, albeit when used at concentrations in excess of the K i for this compound (Attardi & Winters 1998).…”

Section: Discussionmentioning

confidence: 99%

“…As such, PAC 1 -R activation results in coupling to both G q and G s to stimulate the DAG/IP/Ca 2+ /PKC pathway and also to adenylyl cyclase, resulting in cAMP production. Most recently, we have shown PACAP to stimulate the activity of a member of the MAPK family, extracellular signal-regulated kinase 1/2 (ERK1/2), in T3-1 cells in a PKC-dependent manner (Fowkes et al 2001). This appears to regulate the proliferative effects of PACAP in these cells.…”

Section: Introductionmentioning

confidence: 99%

Absence of pituitary adenylate cyclase-activating polypeptide-stimulated transcription of the human glycoprotein alpha-subunit gene in LbetaT2 gonadotrophs reveals disrupted cAMP-mediated gene transcription

Fowkes¹,

Sidhu²,

Sosabowski³

et al. 2003

Journal of Molecular Endocrinology

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Hormone regulation of anterior pituitary expression of the common glycoprotein hormone -subunit ( GSU) is mediated by multiple response elements residing in the first -435 bp of the human promoter. In rat pituitary cells and mouse T3-1 precursor gonadotrophs, the human GSU promoter is strongly responsive to activators of the adenylyl cyclase/cAMP pathway, such as the hypothalamic releasing hormone, pituitary adenylate cyclase-activating polypeptide (PACAP) and forskolin (an adenylyl cyclase activator). However, the role of PACAP and cAMP in regulating GSU transcription in the more differentiated L T2 gonadotroph is unclear. Here, we investigate the regulation of the human GSU promoter by PACAP and forskolin in L T2 and T3-1 gonadotrophs. PACAP failed to stimulate GSU promoter activity or cAMP production in L T2 cells, in marked contrast to T3-1 cells. L T2 gonadotrophs expressed extremely low levels of any PACAP type 1 receptors (PAC 1 -R) isoform by RT-PCR and lacked PAC 1 -R by radioligand binding. Forskolin stimulated the GSU promoter in L T2 cells, but by less than 30% of the response seen in T3-1 gonadotrophs. This blunted cAMP transcriptional effect was not due to different levels of cAMP generation, or altered expression of the cAMP target proteins CREB, Akt, CBP or ICER. However, only L T2 cells showed detectable expression of the protein kinase A type II regulatory subunit. Binding of activating transcription factor-2 and phosphorylated CREB to the consensus CRE was observed in both L T2 and T3-1 gonadotrophs, yet forskolin failed to stimulate either CRE-or CREB-mediated transcription in L T2 cells. Collectively, these data demonstrate the lack of functional PACAP receptors in L T2 gonadotrophs, and a pronounced attenuation in the responsiveness of this differentiated gonadotroph cell line to cAMP stimulus.

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“…Following this pretreatment period, the cells were treated for 10 min with serum-free medium alone, 10 nM T 3 or 100 nM T 4 , in the continued presence or absence of 1 mM U0126 or the monoclonal blocking antibody to a V b 3 . Total proteins were then extracted in the presence of phosphatase inhibitors as described previously and ERK activity was measured using the p44/42 MAP Kinase Assay kit (New England Biolabs, Hitchin, UK) as described previously (Fowkes et al 2001). Briefly, active MAPK was immunoprecipitated from cell lysates with an immobilised phosphop44/42 MAP kinase (ERK; Thr202/Tyr204) monoclonal antibody.…”

Section: Total Protein Extractions and Measurement Of Erk Activitymentioning

confidence: 99%

Thyroid hormone stimulation of extracellular signal-regulated kinase and cell proliferation in human osteoblast-like cells is initiated at integrin αVβ3

Scarlett¹,

Parsons²,

Hanson³

et al. 2008

Journal of Endocrinology

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The aim of the present study was to examine whether triiodo-L-thyronine (T 3 ) or L-thyroxine (T 4 ) rapidly activated the mitogen-activated protein kinase (MAPK) intracellular signalling cascade in osteoblast-like cells and investigate whether this activation was initiated at the integrin a V b 3 cell surface receptor. Using PCR and western blotting, the expression of integrin a V b 3 mRNA and protein was demonstrated in the human osteoblast-like cell lines MG-63 and SaOS-2. The treatment of MG-63 cells with T 3 (10 nM) or T 4 (100 nM) for 10 min stimulated extracellular signal-regulated kinase activity (ERK, a component of the MAPK pathway) as determined by fluorescent immunocytochemistry and an immunocomplex activity assay (T 3 by 10 . 7-fold, P!0 . 01 and T 4 by 10 . 4-fold, P!0 . 01 compared with control). T 3 (10 nM) and T 4 (100 nM) also significantly stimulated thymidine incorporation into MG-63 cells by 2 . 3G0 . 7-fold (P!0 . 01) and 2 . 1G0 . 1-fold (P!0 . 05) respectively. To establish whether transient ERK activation via the integrin a V b 3 cell surface receptor mediated these effects, MG-63 cells were pretreated for 30 min with the specific MAPK kinase inhibitor, U0126 (1 mM), or an antiintegrin a V b 3 -blocking antibody. Both pretreatments significantly inhibited T 3 -and T 4 -stimulated ERK activation and abolished T 3 -stimulated thymidine incorporation (P!0 . 01).T 4 -stimulated incorporation was significantly inhibited from 2 . 1-to 1 . 3-fold above control (P!0 . 05). Thus, our results suggest that T 3 and T 4 rapidly stimulate ERK activation in MG-63 cells via integrin a V b 3 and that one functional effect of this ERK activation is increased DNA synthesis.

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Stimulation of extracellular signal-regulated kinase by pituitary adenylate cyclase-activating polypeptide in alpha T3-1 gonadotrophs

Cited by 23 publications

References 24 publications

Ghrelin exerts a proliferative effect on a rat pituitary somatotroph cell line via the mitogen-activated protein kinase pathway

Ghrelin exerts a proliferative effect on a rat pituitary somatotroph cell line via the mitogen-activated protein kinase pathway

Absence of pituitary adenylate cyclase-activating polypeptide-stimulated transcription of the human glycoprotein alpha-subunit gene in LbetaT2 gonadotrophs reveals disrupted cAMP-mediated gene transcription

Thyroid hormone stimulation of extracellular signal-regulated kinase and cell proliferation in human osteoblast-like cells is initiated at integrin αVβ3

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