Adenylate cyclase stimulation and luteinizing hormone-receptor interaction in plasma membranes from rat testicular interstitial cells in relation to the chemical structure of the hormone. Role of Mg2+

1988 ◽  
Vol 118 (3) ◽  
pp. 399-406
Author(s):  
M. P. de la Llosa-Hermier ◽  
D. Saltarelli ◽  
H. Jammes ◽  
P. de la Llosa ◽  
C. Hermier
Keyword(s):  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Maximal Activity ◽  
Interstitial Cells ◽  
Luteinizing Hormone Receptor ◽  
Receptor Interaction ◽  
Camp Accumulation ◽  
Intact Cells ◽  
Natural Analogues

Abstract. To understand more closely the structural requirements of the LH molecule necessary to stimulate adenylate cyclase, we studied the modulation of this enzyme in partially purified plasma membranes prepared from isolated interstitial cells of rat testis submitted to oLH and to some oLH derivatives and natural analogues. The role of Mg2+ was also investigated in relation to the structural modifications of oLH. Some new facts appeared in this study: 1. Methyl oLH, which exhibited the same ability as native oLH to stimulate cAMP accumulation and steroidogenesis in isolated cells, cannot induce the same level of maximal stimulation of adenylate cyclase as native oLH in plasma membranes. This phenomenon is related to the Mg2+ concentration, and the differences between maximal activation induced by methyl oLH and oLH were more apparent at a free Mg2+ concentration of 3.3 mmol/l than at lower concentrations. The maximal activity (in terms of native oLH) of other alkyl derivatives, such as ethyl or isopropyl oLH, on the contrary, was similar in isolated plasma membranes and in intact cells suggesting that the differential behaviour of the membranes specifically concerns the methyl derivative. 2. Guanidyl oLH and guanidyl porcine LH, which were able to induce cAMP accumulation in intact cells, did not exhibit any stimulating activity in plasma membranes. 3. Among the natural analogues, hCG and pLH are distinguished by a lower maximal activity (by comparison with oLH) particularly at high Mg2+ concentration. This work shows that changes in the LH structure have an impact not only on the parameters of the adenylate cyclase complex but also on the transduction of the hormone signal and its modulation by Mg2+.

Effect of acidosis on PTH-dependent renal adenylate cyclase in phosphorus deprivation: role of G proteins

1990 ◽  
Vol 258 (6) ◽  
pp. F1640-F1649
Author(s):  
E. Bellorin-Font ◽  
R. Starosta ◽  
C. L. Milanes ◽  
C. Lopez ◽  
N. Pernalete ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Adenylate Cyclase ◽  
Maximal Activity ◽  
Phosphate Deprivation ◽  
Adp Ribosylation ◽  
Phosphate Depletion ◽  
Cortical Membranes ◽  
And Function ◽  
Gs Alpha

These studies examine the regulation of adenylate cyclase in renal cortical membranes from phosphate-deprived and phosphate-deprived acidotic dogs. Enzyme stimulation by parathyroid hormone (PTH) was decreased in phosphate deprivation [Vmax 1,578 +/- 169 vs. 2,581 +/- 219 pmol adenosine 3',5'-cyclic monophosphate (cAMP).mg protein-1 x 30 min-1 in controls, P less than 0.01]. Metabolic acidosis further decreased PTH-stimulated activity. Membranes from phosphate-deprived dogs showed a decrease in Gs alpha-content by cholera toxin-dependent ADP-ribosylation (174 +/- 18 arbitrary units vs. 266.4 +/- 13.6 in controls, P less than 0.01). Metabolic acidosis further decreased Gs alpha-content, P less than 0.01. Gi content by pertussis-dependent ADP-ribosylation was also lower in phosphate-deprived and phosphate-deprived acidotic animals. Gs function was examined by its property to protect the catalytic unit from inactivation by N-ethylmaleimide when preincubated with GTP gamma S. In controls, protection of inactivation was 80% of the maximal activity, whereas in phosphate deprivation protection was less than 50%. In conclusion, metabolic acidosis enhances adenylate cyclase resistance to PTH in phosphate deprivation. These alterations are associated with a decrease in the content and function of Gs alpha, suggesting a role of Gs in the renal adaptation to phosphate depletion and acidosis.

The biological activity of glucagon–phospholipid complexes

1983 ◽  
Vol 61 (7) ◽  
pp. 688-691 ◽  
Author(s):  
J. J. Liepnieks ◽  
P. Stoskopf ◽  
E. A. Carrey ◽  
C. Prosser ◽  
R. M. Epand
Keyword(s):  
Biological Activity ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Bovine Brain ◽  
Water Soluble ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Dimyristoyl Phosphatidylcholine ◽  
Lipoprotein Complex ◽  
Stimulation Of

Glucagon can form water-soluble complexes with phospholipids. The incorporation of glucagon into these lipoprotein particles reduces the biological activity of the hormone. The effect is observed only at temperatures below the phase transition temperature of the phospholipid and results in a decreased stimulation of the adenylate cyclase of rat liver plasma membranes by the lipoprotein complex as compared with the hormone in free solution. Two- to five-fold higher concentrations of glucagon are required for half-maximal stimulation of adenylate cyclase when the hormone is complexed with dimyristoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine, or bovine brain sphingomyelin. A possible role of lipoprotein-associated hormones in the development of insulin resistance is discussed.

Pituitary adenylate cyclase-activating peptide stimulates cyclic AMP accumulation in UMR 106 osteoblast-like cells

1996 ◽  
Vol 149 (2) ◽  
pp. 287-295 ◽  
Author(s):  
C S Kovacs ◽  
C L Chik ◽  
B Li ◽  
E Karpinski ◽  
A K Ho
Keyword(s):  
Adenylate Cyclase ◽  
Bone Cells ◽  
Tumor Cell Line ◽  
Camp Accumulation ◽  
Kinase C ◽  
Cyclic Amp Accumulation ◽  
Pituitary Adenylate Cyclase ◽  
And Function ◽  
Umr 106

Abstract Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) share 68% homology and function as neurotransmitters or neuroendocrine factors. Although VIP immunoreactivity has been detected in bone cells, the presence of PACAP or PACAP receptors in bone has not been determined. In this study, we investigated the role of PACAP and VIP in regulating cAMP accumulation in the UMR 106 osteoblast-like tumor cell line. PACAP 27 (10−9 to 3 × 10−7 m), PACAP 38 (10−9 to 3 × 10−7 m) and VIP (10−8 to 10−6 m) stimulated cAMP accumulation up to eightfold. PACAP 27 was slightly more potent than PACAP 38, and both were tenfold more potent than VIP. Both PACAP- and VIP-stimulated cAMP accumulation were potentiated by 4β-phorbol 12-myristate 13-acetate, an activator of protein kinase C. Two PACAP antagonists, PACAP 6–27 (3 × 10−6 m) and PACAP 6–38 (3 × 10−6 m), blocked PACAP- and VIP-stimulated cAMP accumulation. Two VIP antagonists ([Lys1,Pro2,5,Arg3,4,Tyr6]-VIP, and 4 Cl-d-Phe6,Leu17]-VIP) did not reduce the PACAP-or VIP-stimulated cAMP accumulation. Pretreatment with PACAP 27, PACAP 38 or VIP equally blocked PACAP- and VIP-stimulated cAMP accumulation. These results suggest that PACAP is a more potent stimulator of cAMP accumulation than VIP in UMR 106 cells. PACAP and VIP may share a role in the paracrine or neuroendocrine regulation of bone metabolism. Journal of Endocrinology (1996) 149, 287–295

scholarly journals Consequences of hormone-induced desensitization of adenylate cyclase in intact cells

1980 ◽  
Vol 188 (1) ◽  
pp. 169-174 ◽  
Author(s):  
S Swillens ◽  
E Lefort ◽  
R Barber ◽  
R W Butcher ◽  
J E Dumont
Keyword(s):  
Energy Consumption ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Large Energy ◽  
Intact Cells ◽  
Amp System ◽  
Good Compromise ◽  
Highly Efficient ◽  
Theoretical Considerations

A hypothesis on the role of the hormone-induced desensitization of adenylate cyclase is proposed. It is suggested that the desensitization process could provide the cell with a highly efficient cyclic AMP system for transmitting hormone stimulus without requiring a large energy consumption. Theoretical considerations show that in fact the desensitization phenomenon allows the cyclic AMP system to present a good compromise between the efficiency and economy requirements of the cells.

Adenylate cyclase activity in Y1 mouse adrenocortical tumor cells: some properties of the enzyme associated with purified plasma membrane fractions

1983 ◽  
Vol 61 (7) ◽  
pp. 547-552 ◽  
Author(s):  
Bernard P. Schimmer
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Tumor Cell Line ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Adrenocortical Tumor ◽  
Intact Cells ◽  
Order Of Magnitude

Fractions enriched in plasma membranes were prepared from the Y1 mouse adrenocortical tumor cell line and were characterized with respect to adenylate cyclase activity. Optimal requirements of the adenylate cyclase system for guanyl nucleotides, Mg2+, ATP, and corticotropin (ACTH) were determined. The sensitivity of the adenylate cyclase system to ACTH1–24 in plasma membrane fractions was comparable with that observed in isolated intact cells. Polycations such as poly-L-arginine and histone competitively inhibited the action of ACTH1–24, supporting the view that the affinity of ACTH for the adenylate cyclase system is determined by the basic core of amino acids at residues 15–18. ACTH1–24 was at least one order of magnitude more potent than ACTH1–39 in stimulating adenylate cyclase activity in plasma membrane fractions.

scholarly journals Cells retrovirally transfected with fibroblast growth factor-2 isoforms exhibit altered adenylate cyclase activity and G-protein functionality

1996 ◽  
Vol 315 (2) ◽  
pp. 619-624 ◽  
Author(s):  
Agnes ESTIVAL ◽  
Patrick ROBBERECHT ◽  
Marjorie FANJUL ◽  
Bruno ROUOT ◽  
Etienne HOLLANDE ◽  
...  
Keyword(s):  
Growth Factor ◽  
Adenylate Cyclase ◽  
Molecular Mass ◽  
Fibroblast Growth Factor ◽  
G Proteins ◽  
Signalling Pathway ◽  
Peptide Sequence ◽  
Fibroblast Growth ◽  
Intact Cells

Basic fibroblast growth factor (FGF-2) is synthesized as different molecular mass isoforms all lacking the signal-peptide sequence. The high molecular-mass isoforms (21–24 kDa) possess a signal sequence directing their nuclear translocation. The role of each isoform is still poorly understood, however, modifications in intracellular signalling pathways could explain some effects of these peptides. In order to evaluate the role of FGF-2 isoforms on the adenylate cyclase (AC) signalling pathway, we retrovirally infected a rat pancreatic cell line (AR4-2J) with point-mutated FGF-2 cDNAs, allowing the expression of the 18 (A5 cells) or 22.5 kDa isoform (A3 cells) at a low level. In membrane preparations of A3 cells, unscheduled expression of the 22.5 kDa FGF-2 isoform induced a 2-fold decrease in both basal and forskolin-stimulated AC activity. Studies carried out on intact cells also showed decreased accumulation of cAMP in A3 cells in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Both FGF-2 peptides also induced functional modifications of G-proteins without affecting their levels. The 22.5 kDa peptide led to enhanced ADP-ribosylation of both αs-subunits in vitro, whereas the expression of the low molecular-mass 18 kDa peptide resulted in a 2-fold increase in αi2 and α0 ADP-ribosylations. Furthermore, control CAT cells (AR4-2J cells transfected with the retrovirus containing the chloramphenicol acetyltransferase gene) and A5 cells were growth-inhibited by 8-Br-cAMP, in contrast to A3 cells. These data provide evidence that the expression of FGF-2 peptides could play a role in cell functions by modifying the AC signalling pathway. FGF-2 peptides are able to modulate both AC activity and the regulatory G-proteins. Finally FGF-2 expression may interfere with cAMP-regulated cell proliferation.

G protein expression and adenylate cyclase regulation in ventricular cardiomyocytes from STZ-diabetic rats

1994 ◽  
Vol 267 (2) ◽  
pp. H548-H555 ◽  
Author(s):  
A. Wichelhaus ◽  
M. Russ ◽  
S. Petersen ◽  
J. Eckel
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
Plasma Membranes ◽  
Intact Cell ◽  
Streptozotocin Diabetes ◽  
Immunoblot Analysis ◽  
Diabetic Rats ◽  
Heart Cells ◽  
Camp Accumulation ◽  
Ventricular Cardiomyocytes

Isolated adult ventricular cardiomyocytes have been used to study the effects of insulin-deficient diabetes on the expression of cardiac G protein alpha-subunits. Immunoblot analysis of plasma membranes revealed the presence of three different Gs proteins with molecular masses of 45, 47, and 52 kDa. Furthermore, cardiomyocytes were found to contain Gi-2 (41 kDa) and G(o) (39 kDa). Heart cells from streptozotocin-diabetic rats exhibited an unaltered expression of the Gs proteins, whereas Gi-2 and G(o) were reduced by 58 +/- 2 and 27 +/- 11%, respectively. In cells from diabetic rats, adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in response to isoproterenol decreased by approximately 30% at agonist concentrations of 10(-7) to 10(-5) M, with an unaltered maximum stimulation by forskolin. Treatment of cardiomyocytes with pertussis toxin resulted in an incremental increase of isoproterenol-stimulated cAMP formation, which was significantly lower in cardiac myocytes from streptozotocin-diabetic animals (19.2 +/- 1.7 vs. 11.5 +/- 2.4 pmol cAMP.5 x 10(4) cells-1 times 10 min-1). The inhibition of the isoproterenol-induced cAMP accumulation by carbachol in the intact cell was not altered in streptozotocin-diabetes. In conclusion, our data show that insulin-deficient diabetes is associated with a reduced expression and concomitant functional loss of Gi in ventricular cardiomyocytes. Receptor-mediated inhibition of adenylate cyclase remains unaffected by this process, whereas the beta-adrenergic stimulatory pathway involves an additional defect upstream of the adenylate cyclase/G protein system.

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