scholarly journals Activation of adenylate cyclase in bovine corpus-luteum membranes by human choriogonadotropin, guanine nucleotides and NaF

1981 ◽  
Vol 198 (3) ◽  
pp. 631-638 ◽  
Author(s):  
Nicholas B. Lydon ◽  
John L. Young ◽  
David A. Stansfield
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Guanine Nucleotides ◽  
Lag Phase ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Human Choriogonadotropin ◽  
Activated State ◽  
Cyclic Amp Synthesis

1. Preincubation of luteal membranes with human choriogonadotropin results in the formation of an activated state of adenylate cyclase which is not reversed by washing and which is limited only by the absence of guanine nucleotides, whereas preincubation with GTP yields only a partially activated adenylate cyclase which requires the presence of both GTP and human choriogonadotropin during assay to demonstrate maximal activity. 2. Preincubation of luteal membranes with GTP and human choriogonadotropin does not lead to a synergistic increase in wash-resistant activity. 3. Luteal membranes that had been preincubated with GTP and hormone exhibited a decreasing rate of cyclic AMP synthesis during the adenylate cyclase assay incubation; addition of GTP during the assay incubation reversed the decrease. 4. Membranes that had been preincubated in the absence of guanine nucleotide and hormone showed a ‘burst’ phase of cyclic AMP synthesis when GTP was present in the assay incubation and a ‘lag’ phase with p[NH]ppG (guanosine 5′-[β,γ-imido]triphosphate) present in the assay. The presence of human choriogonadotropin with either nucleotide in the assay incubation eliminated the curvatures in plots observed with guanine nucleotides alone. 5. Luteal adenylate cyclase was persistently activated by preincubation with p[NH]ppG alone or in combination with human choriogonadotropin; the activation caused by p[NH]ppG alone was still increasing after 70min of preincubation, whereas that caused by p[NH]ppG in the presence of hormone was essentially complete within 10min of preincubation. 6. Luteal adenylate cyclase that had been partially preactivated by preincubation with p[NH]ppG was slightly increased in activity by the inclusion of further p[NH]ppG in the adenylate cyclase assay incubation, but more so with p[NH]ppG and hormone. Human choriogonadotropin alone caused no further increase in the activity of the partially stimulated preparation unless p[NH]ppG was also added to the assay incubation. 7. GTP decreased the activity of adenylate cyclase in membranes that had been partially preactivated in the presence of p[NH]ppG; the decrease in activity was greater when GTP and hormone were present simultaneously in the assay. 8. The results indicate that stable activation states of adenylate cyclase can be induced by preincubation of luteal membranes in vitro with human choriogonadotropin or p[NH]ppG, and that in the presence of p[NH]ppG the hormone may accelerate events subsequent to guanine nucleotide binding. Stable activation of luteal adenylate cyclase by prior exposure to GTP is not achieved. The involvement of GTPase activity and of hormone-promoted guanine nucleotide exchange in the modulation of luteal adenylate cyclase activity is discussed.

scholarly journals Interactions between adenylate cyclase and the yeast GTPase-activating protein IRA1.

1991 ◽  
Vol 11 (9) ◽  
pp. 4591-4598 ◽  
Author(s):  
M R Mitts ◽  
J Bradshaw-Rouse ◽  
W Heideman
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Adenylate Cyclase System ◽  
Gtpase Activating Protein ◽  
Yeast Saccharomyces Cerevisiae ◽  
Strong Candidate ◽  
Sepharose 4B ◽  
Stimulation Of ◽  
Cyclic Amp Synthesis

The adenylate cyclase system of the yeast Saccharomyces cerevisiae contains many proteins, including the CYR1 polypeptide, which is responsible for catalyzing the formation of cyclic AMP from ATP, RAS1 and RAS2 polypeptides, which mediate stimulation of cyclic AMP synthesis by guanine nucleotides, and the yeast GTPase-activating protein analog IRA1. We have previously reported that adenylate cyclase is only peripherally bound to the yeast membrane. We have concluded that IRA1 is a strong candidate for a protein involved in anchoring adenylate cyclase to the membrane. We base this conclusion on the following criteria: (i) a disruption of the IRA1 gene produced a mutant with very low membrane-associated levels of adenylate cyclase activity, (ii) membranes made from these mutants were incapable of binding adenylate cyclase in vitro, (iii) IRA1 antibodies inhibit binding of adenylate cyclase to the membrane, and (iv) IRA1 and adenylate cyclase comigrate on Sepharose 4B.

scholarly journals Interactions between adenylate cyclase and the yeast GTPase-activating protein IRA1

1991 ◽  
Vol 11 (9) ◽  
pp. 4591-4598
Author(s):  
M R Mitts ◽  
J Bradshaw-Rouse ◽  
W Heideman
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Adenylate Cyclase System ◽  
Gtpase Activating Protein ◽  
Yeast Saccharomyces Cerevisiae ◽  
Strong Candidate ◽  
Sepharose 4B ◽  
Stimulation Of ◽  
Cyclic Amp Synthesis

The adenylate cyclase system of the yeast Saccharomyces cerevisiae contains many proteins, including the CYR1 polypeptide, which is responsible for catalyzing the formation of cyclic AMP from ATP, RAS1 and RAS2 polypeptides, which mediate stimulation of cyclic AMP synthesis by guanine nucleotides, and the yeast GTPase-activating protein analog IRA1. We have previously reported that adenylate cyclase is only peripherally bound to the yeast membrane. We have concluded that IRA1 is a strong candidate for a protein involved in anchoring adenylate cyclase to the membrane. We base this conclusion on the following criteria: (i) a disruption of the IRA1 gene produced a mutant with very low membrane-associated levels of adenylate cyclase activity, (ii) membranes made from these mutants were incapable of binding adenylate cyclase in vitro, (iii) IRA1 antibodies inhibit binding of adenylate cyclase to the membrane, and (iv) IRA1 and adenylate cyclase comigrate on Sepharose 4B.

Cytochemical Evidence for Presynatic β-Adrenergic Regulation of Secretion in the Developing Rat Submandibular Gland

1977 ◽  
Vol 35 ◽  
pp. 430-431
Author(s):  
L.S. Cutler
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Submandibular Gland ◽  
Neonatal Rat ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Parotid Glands ◽  
Adrenergic Agonist ◽  
Rat Submandibular Gland

Many studies previously have shown that the B-adrenergic agonist isoproterenol and the a-adrenergic agonist norepinephrine will stimulate secretion by the adult rat submandibular (SMG) and parotid glands. Recent data from several laboratories indicates that adrenergic agonists bind to specific receptors on the secretory cell surface and stimulate membrane associated adenylate cyclase activity which generates cyclic AMP. The production of cyclic AMP apparently initiates a cascade of events which culminates in exocytosis. During recent studies in our laboratory it was observed that the adenylate cyclase activity in plasma membrane fractions derived from the prenatal and early neonatal rat submandibular gland was retractile to stimulation by isoproterenol but was stimulated by norepinephrine. In addition, in vitro secretion studies indicated that these prenatal and neonatal glands would not secrete peroxidase in response to isoproterenol but would secrete in response to norepinephrine. In contrast to these in vitro observations, it has been shown that the injection of isoproterenol into the living newborn rat results in secretion of peroxidase by the SMG (1).

Effects of cations on binding of human choriogonadotropin

1988 ◽  
Vol 66 (12) ◽  
pp. 1258-1264
Author(s):  
Patrick J. McIlroy
Keyword(s):  
Binding Sites ◽  
Regulatory Protein ◽  
Guanine Nucleotides ◽  
Guanine Nucleotide ◽  
Human Choriogonadotropin ◽  
Receptor Sites ◽  
Number Of Binding Sites ◽  
Receptor Number ◽  
Guanine Nucleotide Regulatory Protein ◽  
Low Ionic Strength

The effect of various salts on the binding of human choriogonadotropin to rat luteal membranes has been examined. Increasing salt concentrations had biphasic effects, initially increasing binding, then decreasing it. With NaCl, these effects were on both the affinity and the number of receptor sites. The affinity increased with increasing NaCl concentrations, to a maximum at 40 mM, and then decreased. Above 40 mM NaCl, the number of binding sites increased. NaCl also altered the effects of Mg2+ and guanyl nucleotides. At low ionic strength, Mg2+ was necessary to observe binding. Guanine nucleotides modulated this binding by decreasing the affinity. At 40 mM NaCl, Mg2+ increased receptor number without altering affinity. Guanyl nucleotides modulated this binding by reducing the number of sites to that observed in the absence of Mg2+. At 150 mM NaCl, Mg2+ and guanine nucleotides had no effect. The results suggest the presence of two pools of human choriogonadotropin receptor in rat corpus luteum, one coupled to the guanine nucleotide regulatory protein (Ns) and being Mg2+ dependent and guanine nucleotide sensitive, and the other not coupled to Ns and being Mg2+ independent and guanine nucleotide insensitive.

scholarly journals Essential Role of Vav Family Guanine Nucleotide Exchange Factors in EphA Receptor-Mediated Angiogenesis

2006 ◽  
Vol 26 (13) ◽  
pp. 4830-4842 ◽  
Author(s):  
Sonja G. Hunter ◽  
Guanglei Zhuang ◽  
Dana Brantley-Sieders ◽  
Wojciech Swat ◽  
Christopher W. Cowan ◽  
...  
Keyword(s):  
Guanine Nucleotide Exchange Factors ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rac1 Gtpase ◽  
Rho Family ◽  
Epha Receptor

ABSTRACT Angiogenesis, the process by which new blood vessels are formed from preexisting vasculature, is critical for vascular remodeling during development and contributes to the pathogenesis of diseases such as cancer. Prior studies from our laboratory demonstrate that the EphA2 receptor tyrosine kinase is a key regulator of angiogenesis in vivo. The EphA receptor-mediated angiogenic response is dependent on activation of Rho family GTPase Rac1 and is regulated by phosphatidylinositol 3-kinase. Here we report the identification of Vav2 and Vav3 as guanine nucleotide exchange factors (GEFs) that link the EphA2 receptor to Rho family GTPase activation and angiogenesis. Ephrin-A1 stimulation recruits the binding of Vav proteins to the activated EphA2 receptor. The induced association of EphA receptor and Vav proteins modulates the activity of Vav GEFs, leading to activation of Rac1 GTPase. Overexpression of either Vav2 or Vav3 in primary microvascular endothelial cells promotes Rac1 activation, cell migration, and assembly in response to ephrin-A1 stimulation. Conversely, loss of Vav2 and Vav3 GEFs inhibits Rac1 activation and ephrin-A1-induced angiogenic responses both in vitro and in vivo. In addition, embryonic fibroblasts derived from Vav2−/− Vav3−/− mice fail to spread on an ephrin-A1-coated surface and exhibit a significant decrease in the formation of ephrin-A1-induced lamellipodia and filopodia. These findings suggest that Vav GEFs serve as a molecular link between EphA2 receptors and the actin cytoskeleton and provide an important mechanism for EphA2-mediated angiogenesis.

scholarly journals Neutralizing monoclonal antibody against ras oncogene product p21 which impairs guanine nucleotide exchange.

1987 ◽  
Vol 7 (5) ◽  
pp. 1999-2002 ◽  
Author(s):  
S Hattori ◽  
D J Clanton ◽  
T Satoh ◽  
S Nakamura ◽  
Y Kaziro ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Exchange Reaction ◽  
Dissociation Rate ◽  
Guanine Nucleotides ◽  
Guanine Nucleotide ◽  
Ras Oncogene ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Neutralizing Monoclonal Antibody ◽  
Ras P21

The neutralizing monoclonal antibody Y13-259 severely hampers the nucleotide exchange reaction between p21-bound and exogenous guanine nucleotides but does not interfere with the association of GDP to p21. These results suggest that the nucleotide exchange reaction is critical for p21 function. Interestingly, the v-ras p21 has a much faster dissociation rate than the p21 of the c-ras proto-oncogene.

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