Modification of the amounts of G proteins and of the activity of adenylyl cyclase in human benign thyroid tumours

ABSTRACT The possibility that a TSH post-receptor-binding defect is responsible for the pathogenesis of benign thyroid tumours was studied. Thus, we attempted to determine in hyperfunctioning (hot) nodules and non-functioning (cold) nodules whether the functional activity or the amount of G proteins were modified in comparison with surrounding normal tissues. The adenylyl cyclase response to agonists that bypass the TSH–receptor complex (forskolin, guanosine 5′- (β.γ-imido)triphosphate (Gpp(NH)p) or [A1F4]−) was studied on membranes from tumorous and adjacent normal thyroid tissues. We also examined the ability of G proteins to be ADP-ribosylated by cholera toxin (CT) or pertussis toxin (PT), and quantified G proteins by Western blot analysis with specific antisera directed against Gsα and Giα subunits. Basal adenylyl cyclase activity was unchanged in hot tumours compared with normal tissue whereas the stimulation of adenylyl cyclase by Gpp(NH)p or [A1F4]− (which act directly on Gs) as well as by forskolin (which acts on the catalyst) was significantly (P<0·05) decreased in five of seven nodules studied. Two types of response were found in cold nodules, depending upon whether they were microfollicular or macrofollicular tumours. Basal as well as stimulated adenylyl cyclase activity was increased (0·02<P<0·05) in microfollicular tumours. In contrast, in macrofollicular tumours basal adenylyl cyclase was unchanged whereas stimulated adenylyl cyclase activity was decreased (0·02<P<0·05). The ability of Gs or Gi to be ADP-ribosylated by CT or PT respectively was maintained in tumorous tissue. Quantification of Gs revealed a 30% decrease (P<0·05) in the level of Gs in hot tumours and either an increase or a decrease in cold tumours compared with their respective normal tissue. Quantitative or qualitative changes in Gi protein were also observed, but there was no clear difference between the patients with hot and cold thyroid tumours. A decrease or an increase in adenylyl cyclase activity can therefore be explained by an alteration in the amounts of G proteins, at least in some benign thyroid tumours. Journal of Endocrinology (1992) 132, 477–485

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Altered expression of Gi-protein and adenylyl cyclase activity in hearts from one kidney one clip hypertensive rats

Journal of Hypertension ◽

10.1097/00004872-199917110-00016 ◽

1999 ◽

Vol 17 (11) ◽

pp. 1617-1626 ◽

Cited By ~ 17

Author(s):

Chang Ge ◽

Raul Garcia ◽

Madhu B. Anand-Srivastava

Keyword(s):

Adenylyl Cyclase ◽

Cyclase Activity ◽

Adenylyl Cyclase Activity ◽

Hypertensive Rats ◽

Altered Expression ◽

Gi Protein

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Postnatal Changes in the G-Proteins, Cyclic Nucleotides and Adenylyl Cyclase Activity in Rabbit Heart Cells

Journal of Molecular and Cellular Cardiology ◽

10.1006/jmcc.1994.1174 ◽

1994 ◽

Vol 26 (12) ◽

pp. 1537-1550 ◽

Cited By ~ 24

Author(s):

R. Kumar ◽

R.W. Joyner ◽

H.C. Hartzell ◽

D. Ellingsen ◽

F. Rishi ◽

...

Keyword(s):

Adenylyl Cyclase ◽

G Proteins ◽

Cyclic Nucleotides ◽

Rabbit Heart ◽

Cyclase Activity ◽

Heart Cells ◽

Adenylyl Cyclase Activity

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Developmental expression of G proteins that differentially modulate adenylyl cyclase activity in mouse brain

FEBS Letters ◽

10.1016/0014-5793(91)81001-o ◽

1991 ◽

Vol 288 (1-2) ◽

pp. 51-54 ◽

Cited By ~ 21

Author(s):

R.Adrian Rius ◽

Richard A. Streaty ◽

Y.Peng Loh ◽

Werner A. Klee

Keyword(s):

Adenylyl Cyclase ◽

G Proteins ◽

Mouse Brain ◽

Cyclase Activity ◽

Developmental Expression ◽

Adenylyl Cyclase Activity

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Liver beta-adrenergic receptors, G proteins, and adenylyl cyclase activity in obesity-diabetes syndromes

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.6.c1664 ◽

1994 ◽

Vol 266 (6) ◽

pp. C1664-C1672 ◽

Cited By ~ 18

Author(s):

N. Begin-Heick

Keyword(s):

Adenylyl Cyclase ◽

G Proteins ◽

Binding Sites ◽

Adrenergic Receptor ◽

Cyclase Activity ◽

Adenylyl Cyclase Activity ◽

Beta Adrenergic Receptor ◽

Beta Adrenergic ◽

Obesity And Diabetes ◽

Liver Membranes

The ob and db genes produce similar hormonal anomalies in mice. Although the expression of the syndromes diverges with age, at 8-12 wk both ob/ob and db/db mice are hyperglycemic and hyperinsulinemic and show evidence of hypercorticoidism. Nevertheless, membranes isolated from livers of ob/ob and db/db mice behave differently in terms of adenylyl cyclase activity and beta-adrenergic receptor function. There are three times as many beta 2-adrenergic receptor binding sites and a threefold increase in the response to catecholamines in ob/ob mouse liver membranes than in comparable preparations from normal controls or db/db mice. By contrast, the two main G proteins of liver membranes (Gs alpha and Gi alpha 2) are less abundant in the mutants, ob/ob and db/db, than in their respective lean controls. Adrenalectomy normalizes the exaggerated response to beta-adrenergic agonists and the number of beta-adrenergic binding sites in the ob/ob mouse. This shows that the enhanced beta-adrenergic receptor response is linked to hypercorticoidism. Cellular maturation and differentiation (D. C. Watkins, J. K. Northrup, and C. C. Malbon, J. Biol. Chem. 262: 10651-10657, 1987) and diseases such as obesity and diabetes (cf. N. McFarlane-Anderson, J. Bailly, and N. Begin-Heick, Biochem. J. 282: 15-23, 1992) have been associated with modifications in the complement of G proteins detected in cells. However, the relationship among levels, types, and intracellular localization of G proteins in tissues and their influence on the transduction of the message to an effector system, such as adenylyl cyclase, are not yet well understood.

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Interaction of Halothane with Inhibitory G-proteins in the Human Myocardium

Anesthesiology ◽

10.1097/00000542-199508000-00016 ◽

1995 ◽

Vol 83 (2) ◽

pp. 353-360. ◽

Cited By ~ 16

Author(s):

Ulrich Schmidt ◽

Robert H. G. Schwinger ◽

Michael Bohm

Keyword(s):

Adenylyl Cyclase ◽

G Proteins ◽

Pertussis Toxin ◽

Adenosine Diphosphate ◽

Human Myocardium ◽

Cyclase Activity ◽

Laboratory Animals ◽

Adenylyl Cyclase Activity ◽

Gamma Subunits ◽

Sensitizing Effect

Background Halothane has been reported to possess a catecholamine-sensitizing effect in laboratory animals and in anesthetized patients and to enhance the positive inotropic effect of isoproterenol in human papillary muscle strips. The current study was designed to investigate further the underlying subcellular mechanisms on human myocardium, in particular the mechanism of action of halothane on G-proteins. Methods To investigate the effect of halothane on adenylyl cyclase activity, isoproterenol-, guanylylimidodiphosphate (Gpp(NH)p)-, and forskolin-activated enzyme activities were studied alone and in the presence of halothane in native and manganese-treated membranes. The mechanisms of halothane interaction with inhibitory G-proteins (G1) were studied in adenosine diphosphate-ribosylation studies with pertussis toxin and immunochemical techniques. Results Halothane (1%) augmented isoproterenol- and Gpp(NH)p-stimulated adenylyl cyclase activity but had no effect on forskolin-stimulated enzyme activity. Manganese ions inhibited the stimulating effect of isoproterenol and Gpp(NH)p on adenylyl cyclase activity, but the effect of forskolin remained unchanged in control and halothane-treated membranes. In the presence of pertussis toxin, the effect of isoproterenol and Gpp(NH)p on adenylyl cyclase activity was enhanced, but further stimulation by halothane was abolished. Halothane did not influence the attachment of Gi alpha to the membrane. No effect of halothane on adenosine diphosphate-ribosylation of Gi alpha by pertussis toxin was observed. Conclusions Halothane stimulates adenylyl cyclase activity by inhibiting the function of the inhibitory G-proteins by interfering with the effects of the alpha subunits or beta gamma subunits with the effector. Decreased membrane attachment of Gi alpha in the presence of halothane does not occur. The interaction of alpha and beta gamma subunits is not affected by halothane. Halothane does not impair the binding of pertussis toxin to the Gi alpha-protein.

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Effects of dexamethasone on G protein levels and adenylyl cyclase activity in rat vascular smooth muscle cells

Journal of Molecular Endocrinology ◽

10.1677/jme.0.0090237 ◽

1992 ◽

Vol 9 (3) ◽

pp. 237-244 ◽

Cited By ~ 11

Author(s):

A. R. McLellan ◽

S. Tawil ◽

F. Lyall ◽

G. Milligan ◽

J. M. C. Connell ◽

...

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Adenylyl Cyclase ◽

G Proteins ◽

Vascular Smooth Muscle Cells ◽

Muscle Cells ◽

Cyclase Activity ◽

Adenylyl Cyclase Activity ◽

Catalytic Unit

ABSTRACT Dexamethasone administration in vitro has been shown to increase adenylyl cyclase activity in vascular smooth muscle cells (VSMC) from renal arteries and in non-vascular cell lines. To investigate whether G proteins are involved in this response, cultured VSMC from mesenteric arteries of Sprague—Dawley rats were incubated in the presence and absence of 10 nm dexamethasone for 24 and 48 h. Basal and stimulated adenylyl cyclase activities were increased by approximately 50% after treatment with dexamethasone. The changes were neither specifically associated with ligands which stimulate adenylyl cyclase catalytic unit via Gs (isoproterenol and prostaglandin E1) nor with guanylylimidodiphosphate (0·1 nm), which inhibits the catalytic unit via Gi. This suggests that dexamethasone enhances adenylyl cyclase activity through changes at the level of the catalytic unit, rather than through the G proteins which modulate its activity. No differences were seen in immunoblotting studies of the levels of Giα2, Gsα, Giα3 and β subunits. Similarly, dexamethasone had no effect on the expression of mRNA for Giα2 and Gsα. The results indicate that glucocorticoid-induced increases of adenylyl cyclase activity are due to changes at the level of the adenylyl cyclase catalytic unit rather than alteration of the levels or turnover of Gsα, Giα2, Giα3 and β subunits in the membranes of VSMC.

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