Cloned receptor

The human oxytocin receptor gene was isolated and characterised in 1994 [122], heralding the development of modern cloned receptor screening. The oxytocin receptor belongs to the Family A series of G-protein coupled 7-transmembrane receptors (GPCRs). A schematic representation of the generic structure of 7TM receptors is shown in Figure 7.3. 

The pharmacological properties of the cloned opiate receptors are similar to the characteristics of the endogenously expressed receptors [9, 36, 45]. The binding of opiates to the cloned receptors is stereoselective and the antagonist naloxone interacts with all three of the cloned receptors, although naloxone had much lower af-... 

Changing the amino acid sequence of the cloned receptors by mutating nucleotides within the receptor cDNAs has proven to be an effective mechanism by which to identify structural features of the receptors responsible for their unique functional properties. In particular, site-directed mutagenesis has been employed to determine the ligand binding domains of each opiate receptor. 

Expression of the cloned receptors in Chinese hamster ovary cells, other mammalian cells and Xenopus oocytes has demonstrated differential coupling of these receptors to cellular responses. In general the Mb M3 and M5 receptors regulate phosphoinositide hydrolysis by stimulating PLC. This occurs through selective coupling of the receptor to the pertussis-toxin-insensitive G protein Gq/11,... 

Scientists at the Harvard Medical School have prepared a recombinant form of a receptor. The idea is to use this cloned receptor as a decoy and mop up the anthrax molecules in circulation. This has been confirmed in laboratory experiments, but ongoing studies are needed. 

Using directed mutation of the cloned receptor gene, Lys 1018 in the ATP-binding part of the tyrosine kinase domain was replaced by alanine. This caused a loss both of kinase activity and of biologic response to insulin.362 Thus, both the tyrosine kinase activity and autophosphorylation appear essential. If so, aggregation of two or more receptors may increase the extent of autophosphorylation and initiate a response. 

The cloned receptor cDNA encodes for a protein of 491 amino adds with all the characteristics of a typical GPCR, as there are 7 putative transmembrane domains, N-terminal glycosylation sites and phosphorylation sites for protein kinase A and C (resp PKA and PKC) [11],... 

Hamdan et al. (2002) describe another biogenic amine-responsive GPCR in the tegument of S. mansoni, which specifically binds to and is activated by histamine. This cloned receptor shares approximately 30% amino acid sequence homology with other major amine GPCRs, and, when transfected into mammalian cells exhibited the following characteristics ... 

Receptor binding (example -adrenoceptors) Cell membrane fractions from organs or cultured cells cloned receptors In vitro Receptor affinity and selectivity... 

Hamblin MW, McGuffin RW, Metcalf MA, Dorsa DM, Merchant KM. Distinct 5-HT1B and 5-HT1D serotonin receptors in rat structural and pharmacological comparison of the two cloned receptors. Mol Cell Neurosci 1992 3 578-587. 

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