scholarly journals Differential Effects of Protein Kinase A on Ras Effector Pathways

1998 ◽  
Vol 18 (7) ◽  
pp. 3718-3726 ◽  
Author(s):  
Marsha J. Miller ◽  
Lise Rioux ◽  
Gregory V. Prendergast ◽  
Sarah Cannon ◽  
Michael A. White ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Critical Role ◽  
Mitogen Activated Protein Kinase ◽  
Thyroid Cells ◽  
Mapk Phosphorylation ◽  
Differential Effects ◽  
Effector Pathways ◽  
Rat Thyroid ◽  
Kinase A

ABSTRACT Ras mutants with the ability to interact with different effectors have played a critical role in the identification of Ras-dependent signaling pathways. We used two mutants, RasS35 and RasG37, which differ in their ability to bind Raf-1, to examine Ras-dependent signaling in thyroid epithelial cells. Wistar rat thyroid cells are dependent upon thyrotropin (TSH) for growth. Although TSH-stimulated mitogenesis requires Ras, TSH activates protein kinase A (PKA) and downregulates signaling through Raf and the mitogen-activated protein kinase (MAPK) cascade. Cells expressing RasS35, a mutant which binds Raf, or RasG37, a mutant which binds RalGDS, exhibited TSH-independent proliferation. RasS35stimulated morphological transformation and anchorage-independent growth. RasG37 stimulated proliferation but not transformation as measured by these indices. TSH exerted markedly different effects on the Ras mutants and transiently repressed MAPK phosphorylation in RasS35-expressing cells. In contrast, TSH stimulated MAPK phosphorylation and growth in cells expressing RasG37. The Ras mutants, in turn, exerted differential effects on TSH signaling. RasS35 abolished TSH-stimulated changes in cell morphology and thyroglobulin expression, while RasG37 had no effect on these activities. Together, the data indicate that cross talk between Ras and PKA discriminates between distinct Ras effector pathways.

scholarly journals TSH Regulates Pendrin Membrane Abundance and Enhances Iodide Efflux in Thyroid Cells

Endocrinology ◽  
2012 ◽  
Vol 153 (1) ◽  
pp. 512-521 ◽  
Author(s):  
Liuska Pesce ◽  
Aigerim Bizhanova ◽  
Juan Carlos Caraballo ◽  
Whitney Westphal ◽  
Maria L. Butti ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Phosphorylation Site ◽  
Physiological Role ◽  
Thyroid Cells ◽  
Hormone Synthesis ◽  
Iodide Transport ◽  
Rat Thyroid ◽  
Kinase A

Thyroid hormones are essential for normal development and metabolism. Their synthesis requires transport of iodide into thyroid follicles. The mechanisms involving the apical efflux of iodide into the follicular lumen are poorly elucidated. The discovery of mutations in the SLC26A4 gene in patients with Pendred syndrome (congenital deafness, goiter, and defective iodide organification) suggested a possible role for the encoded protein, pendrin, as an apical iodide transporter. We determined whether TSH regulates pendrin abundance at the plasma membrane and whether this influences iodide efflux. Results of immunoblot and immunofluorescence experiments reveal that TSH and forskolin rapidly increase pendrin abundance at the plasma membrane through the protein kinase A pathway in PCCL-3 rat thyroid cells. The increase in pendrin membrane abundance correlates with a decrease in intracellular iodide as determined by measuring intracellular 125iodide and can be inhibited by specific blocking of pendrin. Elimination of the putative protein kinase A phosphorylation site T717A results in a diminished translocation to the membrane in response to forskolin. These results demonstrate that pendrin translocates to the membrane in response to TSH and suggest that it may have a physiological role in apical iodide transport and thyroid hormone synthesis.

scholarly journals Adrenergic Regulation of Mitogen-Activated Protein Kinase in Rat Pinealocytes: Opposing Effects of Protein Kinase A and Protein Kinase G**This work was supported by grants from the Medical Research Council of Canada.

Endocrinology ◽  
2000 ◽  
Vol 141 (12) ◽  
pp. 4496-4502 ◽  
Author(s):  
A. K. Ho ◽  
C. L. Chik
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Kinase Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Protein Kinase G ◽  
Adrenergic Stimulation ◽  
Mapk Activation ◽  
Mapk Phosphorylation ◽  
Mitogen Activated Protein ◽  
Kinase A

Abstract The role of adrenergic stimulation in the regulation of mitogen-activated protein kinase (MAPK) in rat pinealocytes was investigated by measuring phosphorylated MAPK using Western blot analysis and a MAPK enzymatic assay. Stimulation with the endogenous neurotransmitter, norepinephrine (NE; a mixed α- and β-adrenergic agonist), concentration dependently increased the phosphorylation of both p44 and p42 isoforms of MAPK. This effect of NE was blocked by PD98059 and UO126 (two inhibitors of MEK). Treatment with prazosin or propranolol significantly reduced the effect of NE on MAPK phosphorylation, suggesting the involvement of both α- andβ -adrenergic receptors. Investigation into the intracellular mechanisms of NE action revealed that the increase in MAPK phosphorylation was blocked by KT5823 (a protein kinase G inhibitor), but was enhanced by H89 (a protein kinase A inhibitor). Calphostin C (a protein kinase C inhibitor) and KN93 (a Ca2+/calmodulin-dependent protein kinase inhibitor) also attenuated NE-mediated MAPK activation, but to a lesser degree. Furthermore, inhibition of MAPK phosphorylation by (Bu)2cAMP was effective in reducing MAPK activation by (Bu)2cGMP, an active phorbol ester or ionomycin. These results indicate that the effect of NE on MAPK phosphorylation represents mainly the integration of two signaling mechanisms, protein kinase A and protein kinase G, each having an opposite effect on MAPK phosphorylation.

Regulation of spontaneous and induced resumption of meiosis in mouse oocytes by different intracellular pathways

Reproduction ◽  
2000 ◽  
pp. 377-383 ◽  
Author(s):  
L Leonardsen ◽  
A Wiersma ◽  
M Baltsen ◽  
AG Byskov ◽  
CY Andersen
Keyword(s):  
Signal Transduction ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Mitogen Activated Protein Kinase ◽  
Meiotic Maturation ◽  
Mouse Oocytes ◽  
Mitogen Activated Protein ◽  
Dependent Signal ◽  
Kinase Pathway ◽  
Kinase A

The mitogen-activated protein kinase-dependent and the cAMP-protein kinase A-dependent signal transduction pathways were studied in cultured mouse oocytes during induced and spontaneous meiotic maturation. The role of the mitogen-activated protein kinase pathway was assessed using PD98059, which specifically inhibits mitogen-activated protein kinase 1 and 2 (that is, MEK1 and MEK2), which activates mitogen-activated protein kinase. The cAMP-dependent protein kinase was studied by treating oocytes with the protein kinase A inhibitor rp-cAMP. Inhibition of the mitogen-activated protein kinase pathway by PD98059 (25 micromol l(-1)) selectively inhibited the stimulatory effect on meiotic maturation by FSH and meiosis-activating sterol (that is, 4,4-dimethyl-5alpha-cholest-8,14, 24-triene-3beta-ol) in the presence of 4 mmol hypoxanthine l(-1), whereas spontaneous maturation in the absence of hypoxanthine was unaffected. This finding indicates that different signal transduction mechanisms are involved in induced and spontaneous maturation. The protein kinase A inhibitor rp-cAMP induced meiotic maturation in the presence of 4 mmol hypoxanthine l(-1), an effect that was additive to the maturation-promoting effect of FSH and meiosis-activating sterol, indicating that induced maturation also uses the cAMP-protein kinase A-dependent signal transduction pathway. In conclusion, induced and spontaneous maturation of mouse oocytes appear to use different signal transduction pathways.

scholarly journals Protein Kinase A Operates a Molecular Switch That Governs Yeast Pseudohyphal Differentiation

2002 ◽  
Vol 22 (12) ◽  
pp. 3981-3993 ◽  
Author(s):  
Xuewen Pan ◽  
Joseph Heitman
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Pathogenic Fungi ◽  
Mitogen Activated Protein Kinase ◽  
Signaling Cascades ◽  
Mitogen Activated Protein ◽  
Eukaryotic Organisms ◽  
Pseudohyphal Differentiation ◽  
Developmental Switch ◽  
Kinase A

ABSTRACT The yeast Saccharomyces cerevisiae undergoes a dimorphic filamentous transition in response to nutrient cues that is affected by both mitogen-activated protein kinase and cyclic AMP-protein kinase A signaling cascades. Here two transcriptional regulators, Flo8 and Sfl1, are shown to be the direct molecular targets of protein kinase A. Flo8 and Sfl1 antagonistically control expression of the cell adhesin Flo11 via a common promoter element. Phosphorylation by the protein kinase A catalytic subunit Tpk2 promotes Flo8 binding and activation of the Flo11 promoter and relieves repression by prohibiting dimerization and DNA binding by Sfl1. Our studies illustrate in molecular detail how protein kinase A combinatorially effects a key developmental switch. Similar mechanisms may operate in pathogenic fungi and more complex multicellular eukaryotic organisms.

patched overexpression alters wing disc size and pattern: transcriptional and post-transcriptional effects on hedgehog targets

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 4161-4170 ◽  
Author(s):  
R.L. Johnson ◽  
J.K. Grenier ◽  
M.P. Scott
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Target Genes ◽  
Critical Role ◽  
Wing Disc ◽  
Wing Vein ◽  
Anterior Compartment ◽  
Protein Levels ◽  
Anterior Posterior ◽  
Kinase A

The membrane protein, Patched, plays a critical role in patterning embryonic and imaginal tissues in Drosophila. patched constitutively inactivates the transcription of target genes such as wingless, decapentaplegic, and patched itself. The secreted protein, Hedgehog, induces transcription of target genes by opposing the Patched signaling pathway. Using the Gal4 UAS system we have overexpressed patched in wing imaginal discs and found that high Patched levels, expressed in either normal or ectopic patterns, result in loss of wing vein patterning in both compartments centering at the anterior/posterior border. In addition, patched inhibits the formation of the mechanosensory neurons, the campaniform sensilla, in the wing blade. The patched wing vein phenotype is modulated by mutations in hedgehog and cubitus interruptus (ci). Patched overexpression inhibits transcription of patched and decapentaplegic and post-transcriptionally decreases the amount of Ci protein at the anterior/posterior boundary. In hedgehogMrt wing discs, which express ectopic hedgehog, Ci levels are correspondingly elevated, suggesting that hedgehog relieves patched repression of Ci accumulation. Protein kinase A also regulates Ci; protein kinase A mutant clones in the anterior compartment have increased levels of Ci protein. Thus patched influences wing disc patterning by decreasing Ci protein levels and inactivating hedgehog target genes in the anterior compartment.

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