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Abstract
Three genomic clones encoding dopamine D1-like receptors were isolated from the avian species Gallus domesticus. Two of these genes encode proteins of 451 and 488 amino acids, which, based on deduced amino acid sequence identity and homology of exhibited pharmacological profiles, appear to be species homologs of mammalian and vertebrate D1/D1A and D5/D1B receptors, respectively. The third genomic clone, termed D1D, encodes a protein of 445 amino acids displaying a deduced amino acid sequence identity within putative transmembrane domains of 75% to mammalian D1/D1A and 77% to D5/D1B receptors with overall sequence homologies of only 49% and 46%, respectively. Membranes from COS-7 cells transfected with D1D DNA bound [3H]SCH-23390 in a saturable manner with high affinity (approximately 300 pM) and with a pharmacological profile clearly indicative of a dopamine D1-like receptor. The D1D receptor exhibited affinities for 6,7-dihydroxy-2-aminotetralin and dopamine 10-fold higher than D1/D1A receptors, characteristic of the D5/D1B receptor subfamily. In contrast, the D1D receptor bound dopaminergic agents, such as SKF-38393, apomorphine, pergolide, and lisuride, with affinities 10-fold higher than other cloned mammalian or vertebrate D1A/D1B receptor subtypes, while both clozapine and haloperidol displayed considerably lower affinity for the D1D receptor. Based on the low overall amino acid sequence identity (54%) and unique pharmacological profile, the avian dopamine D1D receptor does not appear to be a species homolog of the recently cloned vertebrate D1C receptor (Sugamori, K.S., Demchyshyn, L. L., Chung, M., and Niznik, H. B. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 10536-10540). As with all cloned mammalian and vertebrate D1-like receptors, the D1D receptor stimulates adenylate cyclase activity in the presence of dopamine or SKF-82526. Northern blot analysis reveals the selective expression of both avian D1D and D1A receptor mRNAs only in brain with the D1B receptor more widely distributed and localized in tissues such as brain, kidney, and spleen. The isolation of four distinct vertebrate dopamine D1 receptor subtypes suggests the existence of additional mammalian D1 like receptor genes that may account for the observed pharmacological and biochemical multiplicity of dopamine D1-like receptor mediated events.
Highlights
Three genomic clones encoding dopamine Dl-like reo ceptors were isolated from the avian species Gallus domesticus, Two of these genes encode proteins of 451 and 488 amino acids, which, based on deduced amino acid sequence identity and homology of exhibited pharmacological profiles, appear to be species homologs of mammalian and vertebrate DIIDIA and D5IDIB receptors, respectively
Membranes from COS·7 cells transfected with DID DNA bound [3H]SCH23390 in a saturable manner with high affinity (~300 pst) and with a pharmacological profile clearly indicative of a dopamine Dl-like receptor
Using a strategy based on low stringency homology screening, we report here on the isolation and characterization of an additional member of the vertebrate Dl receptor subfamily, termed DID, from the avian species Gallus domesticus
Summary
CLONING AND CHARACTERIZATION OF THREE PHARMACOLOGICALLY DISTINCT Dl-LIKE RECEPTORS FROM Gallus domesticus*. Three genomic clones encoding dopamine Dl-like reo ceptors were isolated from the avian species Gallus domesticus, Two of these genes encode proteins of 451 and 488 amino acids, which, based on deduced amino acid sequence identity and homology of exhibited pharmacological profiles, appear to be species homologs of mammalian and vertebrate DIIDIA and D5IDIB receptors, respectively. Based on the low overall amino acid sequence identity (54%) and unique pharmacological profile, the avian dopamine DID receptor does not appear to be a species homolog of the recently cloned vertebrate DIC receptor As with all cloned mammalian and vertebrate Dl-like receptors, the DID receptor stimulates adenylate cyclase activity in the presence of dopamine or SKF·82526. The isolation of four distinct vertebrate dopamine Dl receptor subtypes suggests the existence of additional mammalian Dl like receptor genes that may account for the observed pharmacological and biochemical multiplicity of dopamine Dl-like receptor mediated events. Using a strategy based on low stringency homology screening, we report here on the isolation and characterization of an additional member of the vertebrate Dl receptor subfamily, termed DID, from the avian species Gallus domesticus (chicken)
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