Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction between plasma sex hormone-binding globulin (SHBG) and its receptor (SHBG-R) inhibits estradiol-induced proliferation of MCF-7 cells (human estrogen-dependent breast cancer) through cAMP and PKA. Thus, SHBG can modulate estradiol action in breast cancer, but the implications of this require a more detailed knowledge of the SHBG-R. To this end, we have transfected MCF-7 cells with an expression vector carrying the human SHBG cDNA (S-MCF-7) and studied the effects of this on both SHBG-R binding and cell proliferation. Control cells were parental MCF-7 (P-MCF-7) and MCF-7 cells transfected with the beta-galactosidase gene (B-MCF-7). Transfections were mediated by lipofectin followed by selection of transfected cells with G418. The amounts of SHBG in culture medium were evaluated by IRMA assay, with only S-MCF-7 cells shown to secrete SHBG; SHBG-R levels were evaluated by tracer binding technique. In P-MCF-7 and B-MCF-7 cells, SHBG-R was detectable as a two-binding site receptor, but no binding of SHBG was observed in S-MCF-7 cells. Proliferation of cells treated with estradiol was evaluated by [3H]thymidine incorporation in the three cell lines and in cells pretreated with SHBG (1 nM) purified from human serum or with conditioned medium from S-MCF-7 cells (medium S). In all three lines, cell proliferation increased after estradiol treatment. Preincubation with purified SHBG was effective in reducing estrogen-induced cell proliferation to basal levels in P-MCF-7 and B-MCF-7 but not in S-MCF-7 cells. The estradiol effect was also inhibited in P-MCF-7 cells treated with medium S. In conclusion, 1) SHBG inhibits estradiol-induced proliferation in cells containing a functional SHBG-R, whereas it has no detectable effect in cells in which the SHBG-R is either absent or not available to bind SHBG; and 2) S-MCF-7 cells are insensitive to SHBG (locally produced or exogenous) because their SHBG-R is occupied by SHBG.
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PMID:Control of the membrane sex hormone-binding globulin-receptor (SHBG-R) in MCF-7 cells: effect of locally produced SHBG. 961 86

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 microgram/ml), PKA blockers KT5720 (100 ng/ml) and adenosine-3',5'-monophosphothiodate (Rp-cAMPS) (1 micromol), 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 microgram GH/ml medium), IGFBP-3 (0.001-1 microgram GH/ml) and oxytocin (0.01-10 microgram GH/ml) secretion. Low concentrations (1-100 ng/ml) of GH stimulated, whilst a higher concentration (10 microgram/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 microgram 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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PMID:GH regulates secretory activity and apoptosis in cultured bovine granulosa cells through the activation of the cAMP/protein kinase A system. 1055 82

The action of growth hormone (GH) on the production of hormones, growth factors, growth factor binding protein and the occurrence of apoptosis in porcine ovarian granulosa cells, as well as the role of cAMP-stimulated protein kinase A (PKA) in the mediation of these effects, were studied. For this purpose, the effects of exogenous pGH (1-10,000 ng/ml), PKA blockers KT5720 (100 ng/ml) and Rp-cAMPS (1micromol), alone and in combination, on insulin-like growth factor type I (IGF-I), insulin-like binding protein 3 (IGFBP-3), oxytocin (OT) and prostaglandin F alpha (PGF) secretion, PKA and cAMP response element binding transcription factor (CREB) content and the occurrence of apoptosis were investigated. It was found (using RIA/IRMA) that GH addition to culture medium significantly stimulated IGF-I and PGF release and inhibited IGFBP-3 and OT secretion. GH significantly decreased the incidence of apoptosis (TUNEL method) in cultured cells. Immunocytochemical study and Western immunoblotting showed, that addition of GH caused a dramatic increase in the accumulation of immunoreactive PKA within the cells, whilst Western blotting did not reveal marked influence of GH on content of CREB in cell lysates. PKA blockers, given alone, were able to decrease IGFBP-3 output (Rp-cAMPS, but not KT5720), reduce basal OT release (either Rp-cAMPS and KT5720) and increase PGF accumulation (KT5720, but not Rp-cAMPS). Furthermore, PKA blockers were able to prevent stimulatory effects of GH on IGF-I and PGF release, and inhibitory effect of GH on IGFBP-3, OT output and on apoptosis. These observations suggest the involvement of GH and a PKA-dependent intracellular mechanism in the control of IGF-I, IGFBP-3, OT, PGF, cAMP and apoptosis in porcine ovarian granulosa cells. Stimulation of PKA by GH and the prevention of GH-induced effects by PKA blockers suggest that both stimulatory and inhibitory effects of GH on porcine ovarian cells are probably mediated by the cAMP/PKA system.
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PMID:Growth hormone can regulate functions of porcine ovarian granulosa cells through the cAMP/protein kinase A system. 1184 11