Agonist potency differentiates G protein activation and Ca2+ signalling by the orexin receptor type 1.
The G protein coupling characteristics of a flag epitope-tagged orexin receptor type 1 (OX1R) was investigated in HEK293 cells. Immunoprecipitation of the OX1R and immunoblotting revealed interactions with Gq/G11 proteins as well as with Gs and Gi proteins. Stimulation with orexin-A did not affect the ability of the OX1R to coprecipitate Gq/G11 proteins, but it robustly elevated the intracellular concentration of Ca2+, [Ca2+]i. No changes in cAMP levels could be detected upon receptor stimulation. To get further insight into the functional correlation of G protein activation and Ca2+ signalling, we used baculovirus transduction to express chimeric G proteins, containing the Galphas protein …
The Concise Guide To Pharmacology 2021/22: G Protein-Coupled Receptors
The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will s…
Azulene as a biphenyl mimetic in orexin/hypocretin receptor agonists
Azulene is a rare ring structure in drugs, and we investigated whether it could be used as a biphenyl mimetic in known orexin receptor agonist Nag 26, which is binding to both orexin receptors OX1 and OX2 with preference towards OX2. The most potent azulene-based compound was identified as an OX1 orexin receptor agonist (pEC50 = 5.79 +/- 0.07, maximum response = 81 +/- 8% (s.e.m. of five independent experiments) of the maximum response to orexin-A in Ca2+ elevation assay). However, the azulene ring and the biphenyl scaffold are not identical in their spatial shape and electron distribution, and their derivatives may adopt different binding modes in the binding site. Peer reviewed
Involvement of cyclin-dependent kinase-5 in the kainic acid-mediated degeneration of glutamatergic synapses in the rat hippocampus
Increased levels of glutamate causing excitotoxic damage accompany neurological disorders such as ischemia/stroke, epilepsy and some neurodegenerative diseases. Cyclin-dependent kinase-5 (Cdk5) is important for synaptic plasticity and is deregulated in neurodegenerative diseases. However, the mechanisms by which kainic acid (KA)-induced excitotoxic damage involves Cdk5 in neuronal injury are not fully understood. In this work, we have thus studied involvement of Cdk5 in the KA-mediated degeneration of glutamatergic synapses in the rat hippocampus. KA induced degeneration of mossy fiber synapses and decreased glutamate receptor (GluR)6/7 and post-synaptic density protein 95 (PSD95) levels in…
Origin of the prolactin-releasing hormone (PRLH) receptors: evidence of coevolution between PRLH and a redundant neuropeptide Y receptor during vertebrate evolution.
We present seven new vertebrate homologs of the prolactin-releasing hormone receptor (PRLHR) and show that these are found as two separate subtypes, PRLHR1 and PRLHR2. Analysis of a number of vertebrate sequences using phylogeny, pharmacology, and paralogon analysis indicates that the PRLHRs are likely to share a common ancestry with the neuropeptide Y (NPY) receptors. Moreover, a micromolar level of NPY was able to bind and inhibit completely the PRLH-evoked response in PRLHR1-expressing cells. We suggest that an ancestral PRLH peptide started coevolving with a redundant NPY binding receptor, which then became PRLHR, approximately 500 million years ago. The PRLHR1 subtype was shown to have…