Urotensin-II (U-II) is a vasoactive 'somatostatin-like' cyclic peptide which was originally isolated from fish spinal cords, and which has recently been cloned from man. Here we describe the identification of an orphan human G-protein-coupled receptor homologous to rat GPR14 and expressed predominantly in cardiovascular tissue, which functions as a U-II receptor. Goby and human U-II bind to recombinant human GPR14 with high affinity, and the binding is functionally coupled to calcium mobilization. Human U-II is found within both vascular and cardiac tissue (including coronary atheroma) and effectively constricts isolated arteries from non-human primates. The potency of vasoconstriction of U-II is an order of magnitude greater than that of endothelin-1, making human U-II the most potent mammalian vasoconstrictor identified so far. In vivo, human U-II markedly increases total peripheral resistance in anaesthetized non-human primates, a response associated with profound cardiac contractile dysfunction. Furthermore, as U-II immunoreactivity is also found within central nervous system and endocrine tissues, it may have additional activities.

Uridine 5-diphosphoglucose (UDP-glucose) has a well established biochemical role as a glycosyl donor in the enzymatic biosynthesis of carbohydrates. It is less well known that UDP-glucose may possess pharmacological activity, suggesting that a receptor for this molecule may exist. Here, we show that UDP-glucose, and some closely related molecules, potently activate the orphan G protein-coupled receptor KIAA0001 heterologously expressed in yeast or mammalian cells. Nucleotides known to activate P2Y receptors were inactive, indicating the distinctly novel pharmacology of this receptor. The receptor is expressed in a wide variety of human tissues, including many regions of the brain. These data suggest that some sugar-nucleotides may serve important physiological roles as extracellular signaling molecules in addition to their familiar role in intermediary metabolism.

and 6 GlaxoSmithKline, Screening and Compound Profiling, Harlow, UK Background and purpose: Atypical cannabinoids are thought to cause vasodilatation through an as-yet unidentified 'CBx' receptor. Recent reports suggest GPR55 is an atypical cannabinoid receptor, making it a candidate for the vasodilator 'CBx' receptor. The purpose of the present study was to test the hypothesis that human recombinant GPR55 is activated by atypical cannabinoids and mediates vasodilator responses to these agents. Experimental approach: Human recombinant GPR55 was expressed in HEK293T cells and specific GTPgS activity was monitored as an index of receptor activation. In GPR55-deficient and wild-type littermate control mice, in vivo blood pressure measurement and isolated resistance artery myography were used to determine GPR55 dependence of atypical cannabinoidinduced haemodynamic and vasodilator responses. Key results: Atypical cannabinoids O-1602 and abnormal cannabidiol both stimulated GPR55-dependent GTPgS activity (EC 50 approximately 2 nM), whereas the CB 1 and CB 2 -selective agonist WIN 55,212-2 showed no effect in GPR55-expressing HEK293T cell membranes. Baseline mean arterial pressure and heart rate were not different between WT and GPR55 KO mice. The blood pressure-lowering response to abnormal cannabidiol was not different between WT and KO mice (WT 2072%, KO 2675% change from baseline), nor was the vasodilator response to abnormal cannabidiol in isolated mesenteric arteries (IC 50 approximately 3 mM for WT and KO). The abnormal cannabidiol vasodilator response was antagonized equivalently by O-1918 in both strains.Conclusions: These results demonstrate that while GPR55 is activated by atypical cannabinoids, it does not appear to mediate the vasodilator effects of these agents. (2007) British Journal of Pharmacology

dehydrogenase by phosphorylation involves no long-range conformational change in the free enzyme.

1 Urotensin-II (U-II) and its G-protein-coupled receptor, GPR14, are expressed within mammalian cardiac and peripheral vascular tissue and, as such, may regulate mammalian cardiovascular function. The present study details the vasoconstrictor pro®le of this cyclic undecapeptide in di erent vascular tissues isolated from a diverse range of mammalian species (rats, mice, dogs, pigs, marmosets and cynomolgus monkeys). 2 The vasoconstrictor activity of human U-II was dependent upon the anatomical origin of the vessel studied and the species from which it was isolated. In the rat, constrictor responses were most pronounced in thoracic aortae and carotid arteries: 7log[EC 50 ]s 9.09+0.19 and 8.84+0.21, R max s 143+21 and 67+26% 60 mM KCl, respectively (compared, for example, to 7log[EC 50 ] 7.90+0.11 and R max 142+12% 60 mM KCl for endothelin-1 [ET-1] in thoracic aortae). Responses were, however, absent in mice aortae (7log [EC 50 ] 56.50). These ®ndings were further contrasted by the observation that U-II was a`coronary-selective' spasmogen in the dog (7log [EC 50 ] 9.46+0.11, R max 109+23% 60 mM KCl in LCX coronary artery), yet exhibited a broad spectrum of vasoconstrictor activity in arterial tissue from Old World monkeys (7log [EC 50 ]s range from 8.96+0.15 to 9.92+0.13, R max s from 43+16 to 527+135% 60 mM KCl). Interestingly, signi®cant di erences in reproducibility and vasoconstrictor e cacy were seen in tissue from pigs and New World primates (vessels which responded to noradrenaline, phenylephrine, KCl or ET-1 consistently). 3 Thus, human U-II is a potent, e cacious vasoconstrictor of a variety of mammalian vascular tissues. Although signi®cant species/anatomical variations exist, the data support the hypothesis that U-II in¯uences the physiological regulation of mammalian cardiovascular function. British Journal of Pharmacology (2000) 131, 1262 ± 1274 Keywords: Urotensin-II; GPR14; SENR; endothelin-1; somatostatin; vascular reactivity; spasmogen; coronary artery; endothelium; vasoconstriction Abbreviations: FLIPR,¯uorescent imaging plate reader; GPCR, guanosine triphosphate-binding protein [G-protein]-coupled receptor; LAD coronary artery, left anterior descending coronary artery; LCX, left circum¯ex coronary artery; SENR, sensory epithelial neuropeptide-like receptor; U-II, Urotensin-II IntroductionThe integrated control of cardiovascular homeostasis is achieved through a combination of direct neuronal control and systemic activation of the neurohumoral axis. The principal mammalian vasoactive factors of this axis (angiotensin-II, endothelin [ET]-1, noradrenaline) exert their haemodynamic e ects exclusively via interactions with speci®c seven transmembrane heterotrimeric G-protein-coupled receptors (GPCRs). Drugs which antagonize such interactions constitute one of the most successful classes of therapeutic agents identi®ed to date (Stadel et al., 1997; Wilson et al., 1998). Nowhere is this more evident than within the vasculature where numerous agents have been developed successfully for the clinical ...