Abstract
Dopamine is widely distributed in metazoans and is implicated in many physiological functions. Dopaminergic signaling is mediated through two classes of dopamine receptors, D1-like and D2-like. Phylogeny analysis reveals that, the dopamine receptors probably appeared ahead of the cnidarian divergence, two distinct classes of dopamine receptors likely formed prior to the separation of deuterostomes and protostomes, and INDRs probably split from its ancestor before the emergence of nematodes. Two D2-like genes are closely linked on the same scaffold, and the chromosome region around D2-like gene loci show colinearity among different species within Lepidoptera. These indicate two D2-like and their adjunction genes are likely Lepidoptera-specific orthologs, and occur by gene duplication event taken place after Lepidoptera ancestor split from the common ancestor of Lepidoptera and Diptera. In silkworm, two D2-like genes were expressed in examined tissues, and encoded BmDop2R2 having all the features of D2-like receptors and BmDop2R1 being a truncated variant without the region of N-terminal to TM II. Only dopamine distinctly lowered cAMP levels in BmDop2R2-expressing cells, whereas all tested amines for BmDop2R1 had not markedly effect in pharmacological test. These suggest there is functional difference between the two genes, which are likely resulted from subfunctionalization of gene duplication.
Highlights
Dopamine is widely distributed in metazoans and is implicated in many physiological functions[1,2,3]
Abiding by the nomenclature of D1-like subclass of arthropod (Dop1R1 and Dop1R2), in this report, one gene having higher homology with the gene of D2-like receptor of other animal was designated as BmDop2R1, while the other was designated as BmDop2R2
By RT-PCR and the RACE technique we cloned the 1406 bp long BmDop2R1 cDNA sequence containing a 1323 bp long ORF that encoded a protein with 440 amino acids and a predicted molecular mass of 46.29 kDa
Summary
Dopamine is widely distributed in metazoans and is implicated in many physiological functions[1,2,3]. D1-like receptors including D1 (D1A) and D5 (D1B) receptors, are coupled to the Gs/Golf class of Gα proteins and thereby activate adenylyl cyclase to increase intracellular cAMP levels. D2-like receptors including D2, D3, and D4 are coupled to Gαi/Go proteins, which inhibit adenylyl cyclase decreasing the intracellular cAMP levels. Like the mammalian D1-like receptors, DOP1 (Dop1R1) and DOP2 (Dop1R2) upregulate cAMP levels when stimulated with dopamine and function like D1-like receptors. Their sequence structure has relatively short third cytoplasmic loops and relatively long carboxyl tails. We cloned D2-like receptor genes from the silkworm, Bombyx mori, a Lepidopteran model, analyzed their evolutionary relationship to metazoan homologs, and identified their function in human embryonic kidney (HEK) 293 cells
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