Protein Kinase C (PKC)-Mediated Growth Hormone (GH) Actions

Wakai, Kae; Tsushima, Takahiro; Murakami, H.; Isozaki, Osamu; Demura, Hiroshi; Nozoe, Yasuko; Yamada, Hiroki

doi:10.1507/endocrj.45.suppl_s97

Cited by 2 publications

(2 citation statements)

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“…Part of the GH effect on ovarian secretory activity, apoptosis and oogenesis (sheep: Wathes et al 1995, rodents: Apa et al 1994, 1996, cow: Kirby et al 1996, Izadyar et al 1997b, human: Ovesen 1998, pig: Sirotkin et al 1998a) are probably not mediated by IGF-I, but directly through ovarian GH receptors (see above). In non-ovarian tissues, GH receptors are associated with intracellular tyrosine or serine-threonine mitogenactivated protein (MAP), PI3, JAK2 kinases, protein kinase C, activators of transcription Stat, adapter protein Shc, insulin receptor substrates, and second messengers diaglycerol, calcium and nitric oxide (Rotwein et al 1994, Campbell 1997, Carter-Su & Smith 1998, Sekine et al 1998, Wakai et al 1998. There are indications that cAMP and cAMP-dependent protein kinase A (PKA) may also be involved in the mediation of GH action on some nonovarian cells: GH was able to stimulate cAMP production by adipocytes (Yip & Goodman 1999), whilst regulators of PKA prevented the effect of GH on adipocytes (Eriksson & Tornqvist 1997) and pancreatic cells (Sekine et al 1996(Sekine et al , 1998.…”

Section: Introductionmentioning

confidence: 99%

GH regulates secretory activity and apoptosis in cultured bovine granulosa cells through the activation of the cAMP/protein kinase A system

Sirotkin

Makarevich²

1999

Journal of Endocrinology

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We have studied the action of GH on the production of hormones, growth factors, growth factor-binding protein and the occurrence of apoptosis in bovine ovarian granulosa cells, as well as the role of cAMP-stimulated protein kinase A (PKA) in the mediation of these effects. For this purpose we investigated the effects of exogenous bovine GH (0·001-10 µg/ml), PKA blockers KT5720 (100 ng/ml) and adenosine-3 ,5 -monophosphothiodate (Rp-cAMPS) (1 µmol), alone and in combination, on IGF-I, IGF-binding protein (IGFBP)-3, oxytocin, progesterone and estradiol secretion, cAMP and PKA content and the occurrence of apoptosis.The secretion of hormones, IGF-I and IGFBP-3 into the culture medium was measured using RIA/IRMA. The presence of PKA was detected using immunocytochemistry and Western immunoblotting. The presence of cAMP in cells was demonstrated using immunocytochemistry, whilst the proportion of apoptotic cells was determined by the TUNEL method.It was found that the addition of GH to the culture medium strongly (P<0·05) stimulated IGF-I (at a concentration of 0·001-10 µg GH/ml medium), IGFBP-3 (0·001-1 µg GH/ml) and oxytocin (0·01-10 µg GH/ml) secretion. Low concentrations (1-100 ng/ml) of GH stimulated, whilst a higher concentration (10 µg/ml) inhibited estradiol output. GH slightly (P<0·05) inhibited progesterone (1-100 ng GH/ml) secretion and significantly (P<0·05) decreased the incidence of apoptosis (0·01-1 µg GH/ml) in cultured cells. The addition of GH (100 ng/ml) caused a dramatic (P<0·05) increase in the proportion of cells possessing the immunoreactive catalytic subunit of PKA and a slight decrease in the proportion of cells containing the regulatory PKA subunit.PKA blockers KT5720 and Rp-cAMPS significantly (P<0·05) reduced the proportion of granulosa cells containing cAMP, and the catalytic and (in the case of KT5720) regulatory subunits of PKA. KT5720 given alone significantly (P<0·05) inhibited the secretion of IGFBP-3, but not that of IGF-I or progesterone. Rp-cAMPS decreased (P<0·05) the secretion of oxytocin but not that of estradiol output or the occurrence of apoptosis. KT5720 and Rp-cAMPS fully or partially prevented the GH effect on IGF-I, IGFBP-3, oxytocin, progesterone, estradiol and apoptosis.These observations suggest the involvement of GH and a cAMP/PKA-dependent intracellular cascade in the control of IGF-I, IGFBP-3, oxytocin, progesterone, estradiol, cAMP and apoptosis in bovine ovarian granulosa cells. The stimulation of PKA by GH and the prevention of GH-induced effects by PKA blockers suggest that the observed GH effects on bovine ovarian cells are probably mediated by the cAMP/PKA system.

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Section: Introductionmentioning

confidence: 99%

GH regulates secretory activity and apoptosis in cultured bovine granulosa cells through the activation of the cAMP/protein kinase A system

Sirotkin

Makarevich²

1999

Journal of Endocrinology

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“…The PKC pathway is induced by an increase in diacylglycerol (DAG) caused by phospholipase C (PLC) activation (Sjoholm et al, 2000). The activated PLC then hydrolyses inositol phospholipids to generate inositol phosphates and DAG, activator of PKC (Wakai et al, 1998). The PKC pathway is implicated in cellular growth and differentiation as well as lipogenesis and metabolism (Bergan et al, 2013).…”

Section: Protein Kinase C Activationmentioning

confidence: 99%

The growth hormone receptor mediated oncogenesis

Chhabra¹

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Growth hormone (GH) is a major regulator of postnatal growth, cellular proliferation and differentiation, as well as of metabolism. All actions of GH are mediated via its cognate Growth Hormone Receptor (GHR). It is now clear that the role of GH extends well beyond the conventional notions of longitudinal growth and childhood development. A substantial body of evidence supports a role for the GH/IGF-1 axis in cancer incidence and progression in animals and humans and because of widespread clinical application of GH, there has been considerable interest in the mechanism of activation of its receptor. It was originally thought that GH initiated its actions by sequentially binding two GHR monomers, resulting in receptor dimerisation and initiation of intracellular signalling cascades, including Jak/STAT and MAPK pathways. However, recent evidence by our group and others has indicated that the GHR is constitutively dimerised, and that dimerisation alone is not sufficient for GHR activation.To this end the main objective of this thesis was to evaluate the role of GH-mediated signalling via its GHR in mediating oncogenesis. We have taken a multi-disciplinary approach by first determining how the GHR is activated via its transmembrane domain (TMD) and the nature of its interaction with Src family of tyrosine kinase (Lyn). We have determined the basis of the contrasting actions of autocrine GH from independent publications and sought to evaluate the effect of various constitutively active GHR constructs in cancer promotion in vitro and in vivo by establishing a tissue-specific delivery system (TVA system) for introducing multiple genes in a spatial and temporally controlled manner. We have provided the molecular basis of increased cancer susceptibility of the first reported GHR variant from two independent epidemiological studies. Finally, we have evaluated cancer resistance and anti-aging pathways in various GHR knockin and knockout mice models.In order to determine the role of GHR transmembrane domain (TMD) and upper juxtamembrane domain (JMD) in signalling, cysteine-scanning mutagenesis was employed with truncated and full length receptors in a thiol-free background. Using these GHR constructs and sequentially substituting residues along the GHR JMD and TMD with cysteine we observed a ligandindependent spontaneous dimerisation pattern of upper JMD and TMD residues with evidence for a 'tilt and twist' movement for this region of GHR during activation. By using Cu-o-phenanthroline we were able to show that GHR activation could occur following disulfide bond formation at the upper TMD boundary resulting in constitutive activation. Finally we were able to conclude that GHR activation requires the JMD residues to come in close proximity which results in separation of iii the lower TMD residues and activation. Another outcome of this study was the generation of the first full-length constitutively active receptor.GHR has been shown to activate numerous pathways and one such pathway involves Src Family Kinase (SFK),...

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Protein Kinase C (PKC)-Mediated Growth Hormone (GH) Actions

Cited by 2 publications

References 13 publications

GH regulates secretory activity and apoptosis in cultured bovine granulosa cells through the activation of the cAMP/protein kinase A system

GH regulates secretory activity and apoptosis in cultured bovine granulosa cells through the activation of the cAMP/protein kinase A system

The growth hormone receptor mediated oncogenesis

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