Regulation of OX1 orexin/hypocretin receptor-coupling to phospholipase C by Ca2+ influx
2007 (English)In: British Journal of Pharmacology, ISSN 0007-1188, E-ISSN 1476-5381, Vol. 150, no 1, 97-104 p.Article in journal (Refereed) Published
Background and purpose: Orexin (OX) receptors induce Ca2+ elevations via both receptor-operated Ca2+ channels (ROCs) and the "conventional" phospholipase C (PLC)-Ca2+ release-store-operated Ca2+ channel (SOC) pathways. In this study we assessed the ability of these different Ca2+ influx pathways to amplify OX, receptor signalling to PLC in response to stimulation with the physiological ligand orexin-A.
Experimental approach: PLC activity was assessed in CHO cells stably expressing human OX1 receptors.
Key results: Inhibition of total Ca2+ influx by reduction of the extracellular [Ca2+] to 1 mu M effectively inhibited the receptor-stimulated PLC activity at low orexin-A concentrations (by 93% at 1 nM), and this effect was gradually reduced by higher orexin-A concentrations. A similar but weaker inhibitory effect (84% at 1 nM) was obtained on depolarization to similar to 0 mV, which disrupts most of the driving force for Ca2+ entry. The inhibitor of the OX, receptor-activated ROCs, tetraethylammonium chloride (TEA), was somewhat less effective than the reduction in extracellular [Ca2+] at inhibiting PLC activation, probably because it only partially blocks ROCs. The partial inhibitor of both ROCs and SOCs, Mg2+, and the SOC inhibitors, dextromethorphan, SKF-96365 (1-[beta-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenethyl]-1H-imidazole HCl) and 2-APB (2-aminoethoxydiphenyl borate), inhibited PLC activity at low concentrations of orexin-A, but were not as effective as TEA.
Conclusions and implications: Both ROCs and SOCs markedly amplify the OX1 receptor-induced PLC response, but ROCS are more central for this response. These data indicate the crucial role of ROCs in orexin receptor signalling.
Place, publisher, year, edition, pages
2007. Vol. 150, no 1, 97-104 p.
Orexin, hypocretin, receptor, G-protein-coupled receptor, calcium, calcium influx, phospholipase C
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-96994DOI: 10.1038/sj.bjp.0706959ISI: 000243528000013PubMedID: 17115071OAI: oai:DiVA.org:uu-96994DiVA: diva2:171753