Biochemical and functional characterization of high‐affinity urotensin II receptors in rat cortical astrocytes

• Published in: Journal of neurochemistry Vol. 99; no. 2; pp. 582 - 595
• Main Authors: Castel, Hélène, Diallo, Mickaël, Chatenet, David, Leprince, Jérôme, Desrues, Laurence, Schouft, Marie‐Thérèse, Fontaine, Marc, Dubessy, Christophe, Lihrmann, Isabelle, Scalbert, Elisabeth, Malagon, Maria, Vaudry, Hubert, Tonon, Marie‐Christine, Gandolfo, Pierrick
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.10.2006; Blackwell; Wiley
• Subjects: Animals; Animals, Newborn; Astrocytes; Astrocytes - drug effects; Astrocytes - metabolism; Bacterial diseases; Binding sites; Binding, Competitive; Binding, Competitive - drug effects; Binding, Competitive - physiology; Biochemistry; Biological and medical sciences; Calcium; Calcium - metabolism; Calcium Signaling; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cell Behavior; Cell Membrane; Cell Membrane - drug effects; Cell Membrane - metabolism; Cells; Cells, Cultured; Cellular Biology; Cerebral Cortex; Cerebral Cortex - cytology; Cerebral Cortex - metabolism; Chemical Sciences; Dose-Response Relationship, Drug; Ent and stomatologic bacterial diseases; Enzyme Inhibitors; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Gene expression; Genes; Guanosine Triphosphate; Guanosine Triphosphate - analogs & derivatives; Guanosine Triphosphate - metabolism; G‐protein‐coupled receptor; Human bacterial diseases; Infectious diseases; Inositol; Inositol - metabolism; Iodine Radioisotopes; Isolated neuron and nerve. Neuroglia; Life Sciences; Medical sciences; Medicinal Chemistry; Neurobiology; Neurons and Cognition; Neurosciences; Pharmaceutical sciences; Pharmacology; Phosphatidylinositol Phosphates; Phosphatidylinositol Phosphates - metabolism; Proteins; Radioligand Assay; Rats; Rats, Wistar; Receptors, G-Protein-Coupled; Receptors, G-Protein-Coupled - metabolism; Rodents; Type C Phospholipases; Type C Phospholipases - antagonists & inhibitors; Type C Phospholipases - metabolism; Urotensins; Urotensins - metabolism; Urotensins - pharmacokinetics; Urotensins - pharmacology; urotensin II; urotensin II receptor; Vertebrates: nervous system and sense organs; Calcium; Rat; Neuroglia; Central nervous system; G-protein-coupled receptor; Esterases; Binding site; Phosphoric diester hydrolases; Neuropeptide; urotensin II; Encephalon; Somatostatin; Biological receptor; Urotensin II receptor; Human; Inositol; Respiratory disease; Enzyme; Saturation; Rodentia; Astrocyte; Gene expression; Whooping cough; Phospholipase C; Infection; Vertebrata; Mammalia; Bacteriosis; Hydrolases; Intracellular; astrocytes
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2006.04130.x

The urotensin II (UII) gene is primarily expressed in the central nervous system, but the functions of UII in the brain remain elusive. Here, we show that cultured rat astrocytes constitutively express the UII receptor (UT). Saturation and competition experiments performed with iodinated rat UII ([125I]rUII) revealed the presence of high‐ and low‐affinity binding sites on astrocytes. Human UII (hUII) and the two highly active agonists hUII4‐11 and [3‐iodo‐Tyr9]hUII4‐11 were also very potent in displacing [125I]rUII from its binding sites, whereas the non‐cyclic analogue [Ser5,10]hUII4‐11 and somatostatin‐14 could only displace [125I]rUII binding at micromolar concentrations. Reciprocally, rUII failed to compete with [125I‐Tyr0,D‐Trp8]somatostatin‐14 binding on astrocytes. Exposure of cultured astrocytes to rUII stimulated [3H]inositol incorporation and increased intracellular Ca2+ concentration in a dose‐dependent manner. The stimulatory effect of rUII on polyphosphoinositide turnover was abolished by the phospholipase C inhibitor U73122, but only reduced by 56% by pertussis toxin. The GTP analogue Gpp(NH)p caused its own biphasic displacement of [125I]rUII binding and provoked an affinity shift of the competition curve of rUII. Pertussis toxin shifted the competition curve towards a single lower affinity state. Taken together, these data demonstrate that rat astrocytes express high‐ and low‐affinity UII binding sites coupled to G proteins, the high‐affinity receptor exhibiting the same pharmacological and functional characteristics as UT.