Biomaterial Database

Corticotropin-releasing factor binding to the anterior pituitary receptor is modulated by divalent cations and guanyl nucleotides. 1986

M H Perrin, and Y Haas, and J E Rivier, and W W Vale

The binding of ovine CRF to bovine anterior pituitary membranes was characterized with the radioligand [Nle21, m-125I Tyr32]ovine CRF. The specific binding of CRF was increased by millimolar concentrations of the divalent cations Mg2+, Ca2+, and Mn2+, but was unaffected by the monovalent cations Na+, Ki+, and Li+. The increase in specific binding was not caused by a change in the affinity, but resulted from an apparent increased number of high affinity binding sites. In the presence of 10 mM Mg2+, CRF binding was saturable, specific, and of high affinity. At room temperature, under optimum conditions, binding reached equilibrium within 70 min, remained stable for at least 4 h, was reversible by excess unlabeled peptide, and was characterized by a Kd of 1.3 nM (0.74-2.4) and a total number of sites, R degree, of 90 fmol/mg protein (55-145). The affinity for the bovine membranes was the same as that for rat anterior pituitary membrane homogenates, and the concentrations of sites were similar. The relative binding affinities for the CRF receptor of selected agonists and antagonists in the bovine and rat systems were similar, and both showed good correlation with the relative in vitro potencies at stimulating or antagonizing, respectively, ACTH release from cultured rat anterior pituitary cells. The nonhydrolyzable GTP analog 5'-guanylylimidodiphosphate [Gpp(NH)p], caused a dose-dependent inhibition of bound radioligand, with an EC50 of about 0.5 microM. In the presence of 1 microM Gpp(NH)p, the number of high affinity CRF-binding sites was reduced, but the affinity was unchanged. In the presence of 5 microM Gpp(NH)p, there was no detectable high affinity binding, and the rate of dissociation of previously bound radioligand was increased. The other guanyl nucleotides, GTP and GDP, inhibited binding but to a lesser extent, whereas GMP and (Bu)2cGMP were ineffective. The inhibition was specific for guanyl nucleotides. In view of the established effects of guanyl nucleotides and divalent cations on adenylate cyclase-linked receptors, these data support the involvement of the adenylate cyclase system in the mechanism of action of CRF on the anterior pituitary.

UI	MeSH Term	Description	Entries
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D010903	Pituitary Gland, Anterior	The anterior glandular lobe of the pituitary gland, also known as the adenohypophysis. It secretes the ADENOHYPOPHYSEAL HORMONES that regulate vital functions such as GROWTH; METABOLISM; and REPRODUCTION.	Adenohypophysis,Anterior Lobe of Pituitary,Anterior Pituitary Gland,Lobus Anterior,Pars Distalis of Pituitary,Adenohypophyses,Anterior Pituitary Glands,Anterior, Lobus,Anteriors, Lobus,Lobus Anteriors,Pituitary Anterior Lobe,Pituitary Glands, Anterior,Pituitary Pars Distalis
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D011869	Radioligand Assay	Quantitative determination of receptor (binding) proteins in body fluids or tissue using radioactively labeled binding reagents (e.g., antibodies, intracellular receptors, plasma binders).	Protein-Binding Radioassay,Radioreceptor Assay,Assay, Radioligand,Assay, Radioreceptor,Assays, Radioligand,Assays, Radioreceptor,Protein Binding Radioassay,Protein-Binding Radioassays,Radioassay, Protein-Binding,Radioassays, Protein-Binding,Radioligand Assays,Radioreceptor Assays
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002413	Cations, Divalent	Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.	Divalent Cations
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D003346	Corticotropin-Releasing Hormone	A peptide of about 41 amino acids that stimulates the release of ADRENOCORTICOTROPIC HORMONE. CRH is synthesized by neurons in the PARAVENTRICULAR NUCLEUS of the HYPOTHALAMUS. After being released into the pituitary portal circulation, CRH stimulates the release of ACTH from the PITUITARY GLAND. CRH can also be synthesized in other tissues, such as PLACENTA; ADRENAL MEDULLA; and TESTIS.	ACTH-Releasing Hormone,CRF-41,Corticotropin-Releasing Factor,Corticotropin-Releasing Hormone-41,ACTH-Releasing Factor,CRF (ACTH),Corticoliberin,Corticotropin-Releasing Factor-41,ACTH Releasing Factor,ACTH Releasing Hormone,Corticotropin Releasing Factor,Corticotropin Releasing Factor 41,Corticotropin Releasing Hormone,Corticotropin Releasing Hormone 41
D006150	Guanine Nucleotides		Guanine Nucleotide,Guanosine Phosphates,Nucleotide, Guanine,Nucleotides, Guanine,Phosphates, Guanosine