| Autor: |
Ulsund AH; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.; Center for Heart Failure Research, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway., Dahl M; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.; Center for Heart Failure Research, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway., Frimurer TM; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark; and., Manfra O; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.; Center for Heart Failure Research, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway., Schwartz TW; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark; and.; Department for Biomedical Research, Laboratory for Molecular Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark., Levy FO; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.; Center for Heart Failure Research, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway., Andressen KW; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.; Center for Heart Failure Research, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway. |
| Abstrakt: |
According to early models of GPCR signaling, G proteins only interact with activated receptors. However, some GPCRs were shown to assemble with G proteins before receptor activation, in accordance with more recent models. Previously, we found that the 5-HT 7 receptor, as opposed to the 5-HT 4 receptor, was preassociated with G s , but the molecular determinants for this interaction are still elusive. In a series of chimeric 5-HT 7 receptors with intracellular segments from 5-HT 4 , we determined the receptor-G protein interaction by performing antibody-immobilized fluorescence recovery after photobleaching and fluorescence resonance energy transfer. We identified the intracellular loop 3 and C-tail of the 5-HT 7 receptor to be responsible for the preassociation with G s , and we further delineated the TM5 extension in the intracellular loop 3 and helix 8 in the C-tail as the molecular determinants. These chimeric exchanges converted the 5-HT 7 receptor into a collision-coupled receptor that recruited G proteins only upon agonist activation, whereas reciprocal exchanges converted 5-HT 4 to a preassociated receptor. The 5-HT 7 receptor displayed 2-component agonist-induced G s signaling with high and low potency. In addition, the same segments were involved in low-potency signaling and preassociation. The correspondence between G s preassociation and low-potency G s signaling is a novel aspect of GPCR pharmacology.-Ulsund, A. H., Dahl, M., Frimurer, T. M., Manfra, O., Schwartz, T. W., Levy, F. O., Andressen, K. W. Preassociation between the 5-HT 7 serotonin receptor and G protein G s : molecular determinants and association with low potency activation of adenylyl cyclase. |
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