cAMP Stimulation of CFTR-expressing Xenopus oocytes activates a chromanol-inhibitable K+ conductance

1996 ◽  
Vol 432 (3) ◽  
pp. 516-522 ◽  
Author(s):  
M. Mall ◽  
K. Kunzelmann ◽  
A. Hipper ◽  
R. Greger ◽  
A. E. Busch
Keyword(s):  
Xenopus Oocytes ◽  
Camp Stimulation ◽  
Stimulation Of

scholarly journals cAMP induces a rapid and reversible modification of the chemotactic receptor in Dictyostelium discoideum.

1985 ◽  
Vol 100 (3) ◽  
pp. 715-720 ◽  
Author(s):  
C Klein ◽  
J Lubs-Haukeness ◽  
S Simons
Keyword(s):  
Dictyostelium Discoideum ◽  
Concentration Dependence ◽  
Time Course ◽  
Camp Synthesis ◽  
Sds Page ◽  
Reversible Modification ◽  
Camp Receptor ◽  
Camp Stimulation ◽  
Stimulation Of

Stimulation, within 1 min after cAMP stimulation, of aggregation-competent Dictyostelium discoideum amebae was found to cause a rapid (within 1 min) modification of the cell's surface cAMP receptor. The modified receptor migrated on SDS PAGE as a 47,000-mol-wt protein, as opposed to a 45,000-mol-wt protein labeled on unstimulated cells. The length of time this modified receptor could be detected depended upon the strength of the cAMP stimulus: 3-4 min after treatment with 10(-7) M cAMP, cells no longer possessed the 47,000-mol-wt form of the cAMP receptor. Instead, the 45,000-mol-wt form was present. Stimulation of cells with 10(-5) M cAMP, however, resulted in the persistent (over 15 min) expression of the modified receptor. The time course, concentration dependence, and specificity of stimulus for this cAMP-induced shift in the cAMP receptor were found to parallel the cAMP-stimulated phosphorylation of a 47,000-mol-wt protein. In addition, both phenomena were shown to occur in the absence of endogenous cAMP synthesis. The possibility that the cAMP receptor is phosphorylated in response to cAMP stimulation, and the role of this event in cell desensitization, are discussed.

Early stimulation of phospholipid methylation in Xenopus oocytes by progesterone

1985 ◽  
Vol 16 (1) ◽  
pp. 35-41 ◽  
Author(s):  
Francois Godeau ◽  
Teruko Ishizaka ◽  
S.S. Koide
Keyword(s):  
Xenopus Oocytes ◽  
Early Stimulation ◽  
Stimulation Of

ACTH and cAMP Stimulation of Adrenal Ribosomal Protein Phosphorylation1

Endocrinology ◽  
1973 ◽  
Vol 93 (6) ◽  
pp. 1287-1293 ◽  
Author(s):  
BERNARD A. ROOS
Keyword(s):  
Ribosomal Protein ◽  
Camp Stimulation ◽  
Stimulation Of

scholarly journals Glucose stimulates and insulin inhibits release of pancreatic TRH in vitro

2000 ◽  
pp. 60-65 ◽  
Author(s):  
J Benicky ◽  
V Strbak
Keyword(s):  
B Cells ◽  
Pancreatic Islets ◽  
High Glucose ◽  
Adenosine Monophosphate ◽  
Isolated Pancreatic Islets ◽  
Glucose Addition ◽  
Adult Rat ◽  
Camp Stimulation ◽  
Stimulation Of

OBJECTIVE: Pancreatic TRH is present in insulin-producing B-cells of the islets of Langerhans. There is fragmentary evidence that it may be involved in glucoregulation. The aim of our present study was to analyze how glucose and insulin affect TRH secretion by the pancreatic islets. DESIGN: Isolated pancreatic islets were incubated with different concentrations of glucose, insulin and glucagon, and TRH release was measured. RESULTS: In the present study, 6 and 12mmol/l d-glucose caused significant TRH release from isolated adult rat pancreatic islets when compared with that in the presence of the same concentrations of biologically ineffective l-glucose. Thirtymmol/l d-glucose was also ineffective, but this was not due to depression of secretion by hyperosmolarity since isosmotic compensation for the high glucose addition did not restore its stimulatory effect. Five micromol/l dibutyryl cyclic 3',5'-adenosine monophosphate (db-cAMP) increased both basal and glucose-stimulated TRH release, but this effect was not seen with 50micromol/l db-cAMP. Stimulation of phosphodiesterase by imidazole resulted in decreased basal but not glucose-stimulated release of TRH. Glucagon (10(-7)mol/l) did not affect either basal or glucose-stimulated release of TRH, while insulin (10(-7) and 10(-6)mol/l) inhibited both. CONCLUSION: Our present data showing that glucose stimulates and insulin inhibits pancreatic TRH release are compatible with the possibility that this substance may play a role in glucoregulation.

scholarly journals Stimulation of Vitellogenin Uptake in Stage IV Xenopus Oocytes by Treatment with Chorionic Gonadotropin in vitro

1978 ◽  
Vol 18 (5) ◽  
pp. 762-771 ◽  
Author(s):  
H. Steven Wiley ◽  
James N. Dumont
Keyword(s):  
Chorionic Gonadotropin ◽  
Xenopus Oocytes ◽  
Stage Iv ◽  
Stimulation Of

scholarly journals Transforming ras proteins accelerate hormone-induced maturation and stimulate cyclic AMP phosphodiesterase in Xenopus oocytes.

1990 ◽  
Vol 10 (4) ◽  
pp. 1689-1696 ◽  
Author(s):  
S E Sadler ◽  
J L Maller ◽  
J B Gibbs
Keyword(s):  
Enzyme Activity ◽  
Time Course ◽  
Xenopus Oocytes ◽  
Insulin Treatment ◽  
Ras Oncogene ◽  
Ras Proteins ◽  
Phosphodiesterase Activity ◽  
Oncogene Products ◽  
Stimulation Of

Transforming Harvey (Ha) ras oncogene products accelerated the time course of Xenopus oocyte maturation induced by insulin, insulinlike growth factor 1, or progesterone. The transforming constructs, [Val-12]Ha p21 and [Val-12, Thr-59]Ha p21, displayed equal potency and efficacy in their abilities to accelerate the growth peptide-induced response. Normal Ha p21 was only 60% as powerful and one-fifth as potent as the mutants containing valine in the 12 position. In contrast, two nontransforming constructs, [Val-12, Ala-35, Leu-36, Thr-59]Ha p21 and [Val-12, Thr-59]Ha(term-174) p21, had no effect on the time course of hormone-induced maturation. Effects of the transforming ras proteins on hormone-induced maturation correlated with their abilities to stimulate in vivo phosphodiesterase activity measured after microinjection of 200 microM cyclic [3H] AMP. When p21 injection followed 90 min of insulin treatment, there was no increase in phosphodiesterase activity over that measured after hormone treatment or p21 injection alone, but additive effects of p21 and insulin on enzyme activity were observed during the first 90 min of insulin treatment. Even though normal Ha p21 and transforming [Val-12, Thr-59]Ha p21 stimulated oocyte phosphodiesterase to equal levels when coinjected with substrate at the initiation of the in vivo assay, the transforming protein elicited a more sustained stimulation of enzyme activity. These results suggest that stimulation of a cyclic AMP phosphodiesterase activity associated with insulin-induced maturation is involved in the growth-promoting actions of ras oncogene products in Xenopus oocytes.

scholarly journals Reversible Ca Gradients between the Subplasmalemma and Cytosol Differentially Activate Ca-dependent Cl Currents

1999 ◽  
Vol 113 (2) ◽  
pp. 249-266 ◽  
Author(s):  
Khaled Machaca ◽  
H. Criss Hartzell
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Confocal Microscopy ◽  
Driving Force ◽  
Xenopus Oocytes ◽  
Biophysical Properties ◽  
Temporal Features ◽  
Cl Channels ◽  
Spatio Temporal ◽  
Stimulation Of

Xenopus oocytes express several different Ca-activated Cl currents that have different waveforms and biophysical properties. We compared the stimulation of Ca-activated Cl currents measured by two-microelectrode voltage clamp with the Ca transients measured in the same cell by confocal microscopy and Ca-sensitive fluorophores. The purpose was to determine how the amplitude and/or spatio-temporal features of the Ca signal might explain how these different Cl currents were activated by Ca. Because Ca release from stores was voltage independent, whereas Ca influx depended upon the electrochemical driving force, we were able to separately assess the contribution of Ca from these two sources. We were surprised to find that Ca signals measured with a cytosolic Ca-sensitive dye, dextran-conjugated Ca-green-1, correlated poorly with Cl currents. This suggested that Cl channels located at the plasma membrane and the Ca-sensitive dye located in the bulk cytosol were sensing different [Ca]. This was true despite Ca measurement in a confocal slice very close to the plasma membrane. In contrast, a membrane-targeted Ca-sensitive dye (Ca-green-C18) reported a Ca signal that correlated much more closely with the Cl currents. We hypothesize that very local, transient, reversible Ca gradients develop between the subplasmalemmal space and the bulk cytosol. [Ca] is higher near the plasma membrane when Ca is provided by Ca influx, whereas the gradient is reversed when Ca is released from stores, because Ca efflux across the plasma membrane is faster than diffusion of Ca from the bulk cytosol to the subplasmalemmal space. Because dissipation of the gradients is accelerated by inhibition of Ca sequestration into the endoplasmic reticulum with thapsigargin, we conclude that [Ca] in the bulk cytosol declines slowly partly due to futile recycling of Ca through the endoplasmic reticulum.

scholarly journals Protein kinase B/Akt is essential for the insulin- but not progesterone-stimulated resumption of meiosis in Xenopus oocytes

2003 ◽  
Vol 369 (2) ◽  
pp. 227-238 ◽  
Author(s):  
Carsten B. ANDERSEN ◽  
Hiroshi SAKAUE ◽  
Taku NEDACHI ◽  
Kristina S. KOVACINA ◽  
Carol CLAYBERGER ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Cell Cycle Progression ◽  
Time Course ◽  
Xenopus Oocytes ◽  
Northern Blotting ◽  
Dominant Negative ◽  
Cycle Progression ◽  
Reverse Transcription Pcr ◽  
Rapid Activation ◽  
Stimulation Of

In the present study, we have characterized the Xenopus Akt expressed in oocytes from the African clawed frog Xenopus laevis and tested whether its activity is required for the insulin- and progesterone-stimulated resumption of meiosis. A cDNA encoding the Xenopus Akt was isolated and sequenced, and its expression in the Xenopus oocyte was confirmed by reverse transcription PCR and Northern blotting. Using phosphospecific antibodies and enzyme assays, a large and rapid activation of the Xenopus Akt was observed upon insulin stimulation of the oocytes. In contrast, progesterone caused a modest activation of this kinase with a slower time course. To test whether the activation of Akt was required in the stimulation of the resumption of meiosis, we have utilized two independent approaches: a functional dominant negative Akt mutant and an inhibitory monoclonal antibody. Both the mutant Akt, as well as the inhibitory monoclonal antibody, completely blocked the insulin-stimulated resumption of meiosis. In contrast, both treatments only partially inhibited (by approx. 30%) the progesterone-stimulated resumption of meiosis when submaximal doses of this hormone were utilized. These data demonstrate a crucial role for Akt in the insulin-stimulated cell cycle progression of Xenopus oocytes, whereas Akt may have an ancillary function in progesterone signalling.

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