A novel G protein-coupled receptor was cloned by PCR and homology screening. Its deduced amino acid sequence is 47% identical overall to the p, 6 and rc opioid receptors and 64% identical in the putative transmembrane domains. When transiently expressed in COS-7 cells this receptor did not bind any of the typical p, 6 or K opioid receptor ligands with high affinity. In situ hybridization analysis revealed that LC132 mRNA is highly expressed in several rat brain areas, including the cerebral cortex, thalamus, subfornical organ, habenula, hypothalamus, central gray, dorsal raphe, locus coeruleus and the dorsal horn of the spinal cord. Based on this distribution and its high homology with the ,u, S and K opioid receptors, it is proposed that LC132 is a new member of the opioid receptor family that is involved in analgesia and the perception of pain.
The dopamine receptors are integral membrane proteins that interact with guanine nucleotide-binding proteins (G proteins) to transduce dopamine stimulation into intracellular responses. The majority of dopamine receptors are concentrated in the mesocortico-mesolimbic, nigrostriatal, and tuberoinfundibular pathways. These neuronal circuits are known to influence mood, behavior, initiation of movement, and prolactin secretion. Prior to the cloning of the rat D2 dopamine receptor gene (1) only D1 and D2 receptors were generally acknowledged to account for the diverse physiological effects of dopamine (2-4), although some pharmacological evidence was inconsistent with this view (5).With nucleic acid probes based on the sequence of the cloned rat D2 receptor gene it was quickly revealed that at least four dopamine receptor genes exist in humans and rats (6-15). Based on their genomic organization these genes can be divided into two types: those with (D2, D3, and D4) and those without (D1) introns in their coding regions. During a structural analysis of the human D1 dopamine receptor gene we obtained evidence that the human genome contains a sequence that is similar but not identical to the D1 gene. To determine whether or not this sequence encoded a dopamine receptor, we undertook its cloning and characterization
We have cloned and expressed a rat brain cDNA, TS11, that encodes a p-opioid receptor based on pharmacological, physiological, and anatomical criteria . Membranes were prepared from COS-7 cells transiently expressing TS11 bound [3 H]diprenorphine with high affinity (Kp = 0.23 -0.04 nM) . The rank order potency of drugs competing with [3 H]diprenorphine was as follows: levorphanol (K, = 0.6 -!-0 .2 nM)~ß-endorphin (K, = 0.7 0.5 nM)~morphine (K ; = 0.8 ± 0.5 nM) -[D-Ala2, N-Me-Phe 4 ,Gly-ol 5 ]-enkephalin (DAMGO ; K; = 1 .6 ± 0.5 nM) > U50,488 (K, = 910 ± 0.78 nM) > [D-Pen 2 .5]enkephalin (K, = 3,170 ± 98 nM) > dextrorphan (K, 4,100 --68 nM) . The rank order potencies of these ligands, the stereospecificity of levorphanol, and morphine's subnanomolar K ; are consistent with a p-opioid binding site. Two additional experiments provided evidence that this opioid-binding site is functionally coupled to G proteins: (a) In COS-7 cells 50 pM 5'-guanylylimidodiphosphate shifted a fraction of receptors with high affinity for DAMGO (IC5n = 3.4 ± 0 .5 nM) to a loweraffinity state (IC5o = 89 .0 ± 19 .0 nM), and (b) exposure of Chinese hamster ovary cells stably expressing the cloned p-opioid receptor to DAMGO resulted in a closedependent, naloxone-sensitive inhibition of forskolinstimulated cyclic AMP production . The distribution of mRNA corresponding to the p-opioid receptor encoded by TS11 was determined by in situ hybridization to brain sections prepared from adult female rats . The highest levels of p-receptor mRNA were detected in the thalamus, medial habenula, and the caudate putamen ; however, significant hybridization was also observed in many other brain regions, including the hypothalamus .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.