Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In isolated hepatocytes of rats with advanced phosphate depletion (serum Pi in controls: 8.79 +/- 0.16 mg/dl; Pi depletion: 2.79 +/- 0.18 mg/dl), diminished gluconeogenesis is observed [controls: 247 +/- 21 nmol X (mg protein)-1 X (30 min)-1; Pi depletion: 174 +/- 15]. In vitro stimulation with glucagon (28 nmol/l) caused a significant rise of glucose production, fall in lactate production, and increase in cAMP content in controls, but did not change glucose or lactate production in Pi depletion despite significant stimulation of cAMP content. This defect was not corrected by pretreating Pi-depleted animals with somatostatin. Impaired basal and glucagon-stimulated glucose production by hepatocytes of Pi-depleted animals was not reversed by incubation in a medium with high Pi content. Insulin (17 nmol/l) did not influence glucose or lactate production in hepatocytes of control or Pi-depleted animals. Epinephrine (10(-6) M) caused a significant stimulation of glucose production in control animals which was inhibited both by phenoxybenzamine (10(-4) M) and propranolol (10(-3) M). Epinephrine-mediated increase of glucose production with pyruvate (10 mM) as substrate was reduced but still demonstrable in hepatocytes of phosphate-depleted animals in parallel with a significant rise of hepatocellular cAMP concentration. Various concentrations of bovine PTH1-34 failed to affect cAMP concentration, glucose or lactate production in Pi-depleted animals and glucose or lactate production in controls. Impaired basal and stimulated (glucagon and epinephrine) glucose production despite adequate cellular cAMP generation points to steps distal to adenylate cyclase as the cause of disturbed hepatic gluconeogenesis in phosphate depletion.
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PMID:Effect of phosphate depletion on gluconeogenesis in isolated rat hepatocytes. 614 23

The development of refractoriness of the cAMP response to PTH in primary cultures of chick kidney cells and recovery from the refractory state was investigated. When cells were preincubated with bovine PTH1-34, complete refractoriness to a subsequent challenge with the hormone developed within 2 h and at hormone concentrations as low as 5 ng/ml. The ability of PTH to stimulate activation of cAMP-dependent protein kinase was also abolished by preincubation with the hormone. When cells were desensitized and then incubated in hormone-free medium, recovery of the cAMP response began within an hour and was maximal, but not complete (80%) after 16 h. Cycloheximide did not affect either desensitization or the rate or extent of recovery from the refractory state. Low concentrations of forskolin (2.5 X 10(-7) M) greatly enhanced cAMP production stimulated by PTH and higher concentrations (10(-6) - 10(-4) M) stimulated rates of cAMP production 50 times those obtained with PTH alone. Preincubation with forskolin did not bring about desensitization to PTH nor did preincubation with PTH affect the subsequent response to forskolin. The half-life of biologically active bovine PTH1-34 in chick kidney cell culture was approximately 12 h and the rate of its removal was not significantly altered during a 20-h incubation period. The results suggest that desensitization of chick kidney cells to PTH is not suggest that desensitization of chick kidney cells to PTH is not brought about by cAMP generation itself, is not primarily dependent on protein synthesis, and does not involve a change in the rate of removal of biologically active hormone from the medium. In addition, recovery of the cAMP response to PTH also does not require new protein synthesis. These results are compatible with a mechanism of desensitization which occurs at the level of the receptor or hormone-receptor coupling to adenyl cyclase.
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PMID:Homologous desensitization of cultured chick kidney cells to parathyroid hormone. 631 38

The receptor activity-modifying proteins (RAMPs) comprise a family of three accessory proteins that heterodimerize with the calcitonin receptor-like receptor (CL receptor) or with the calcitonin receptor (CTR) to generate different receptor phenotypes. However, RAMPs are more widely distributed across cell and tissue types than the CTR and CL receptor, suggesting additional roles for RAMPs in cellular processes. We have investigated the potential for RAMP interaction with a number of Class II G protein-coupled receptors (GPCRs) in addition to the CL receptor and the CTR. Using immunofluorescence confocal microscopy, we demonstrate, for the first time, that RAMPs interact with at least four additional receptors, the VPAC1 vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating peptide receptor with all three RAMPs; the glucagon and PTH1 parathyroid hormone receptors with RAMP2; and the PTH2 receptor with RAMP3. Unlike the interaction of RAMPs with the CL receptor or the CTR, VPAC1R-RAMP complexes do not show altered phenotypic behavior compared with the VPAC1R alone, as determined using radioligand binding in COS-7 cells. However, the VPAC1R-RAMP2 heterodimer displays a significant enhancement of agonist-mediated phosphoinositide hydrolysis with no change in cAMP stimulation compared with the VPAC1R alone. Our findings identify a new functional consequence of RAMP-receptor interaction, suggesting that RAMPs play a more general role in modulating cell signaling through other GPCRs than is currently appreciated.
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PMID:Novel receptor partners and function of receptor activity-modifying proteins. 1244 22

Parathyroid hormone (PTH) is the primary regulator of serum calcium homeostasis and plays a major role in bone metabolism. Its actions are mediated via the PTH1 receptor (PTH1R) resulting in adenylate cyclase activation and consequently production of cyclic adenosine mono-phosphate (cAMP). The latter stimulates cellular metabolic pathways. This study describes the development, validation and applications of a novel cell-based potency assay for PTH using HEK293 cells over-expressing PTH1R. PTH concentration-dependent cAMP formation in these cells was quantitatively analyzed employing time-resolved fluorescence technology (TR-FRET). The optimized assay was precise, reproducible and exhibited a high sensitivity to PTH with a limit of quantification in the low picogram range. The potencies of differently manufactured PTH1-34 peptides, as well as a full-length variant (PTH1-84), were all accurately measured. Since PTH activity is inhibited by neutralizing antibodies against PTH, the assay was adapted to detect and measure neutralizing antibodies in human serum. Thus, applications of this novel cell-based PTH potency assay were extended to immunogenicity testing of PTH preparations in non-clinical and clinical settings.
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PMID:Development and validation of a novel cell-based assay for potency determination of human parathyroid hormone (PTH). 2499 7