Molecular cloning and characterization of cDNAs encoding dopamine receptor‐1 and ‐2 from brain‐suboesophageal ganglion of the silkworm, Bombyx mori

Abstract

In order to better understand the relationship between dopamine and the release of diapause hormone into the blood, we cloned and characterized cDNAs encoding Bombyx mori dopamine receptor-1 and -2 (BmDopR1 and 2) from the pupal brain-suboesophageal ganglion. BmDopR1 and 2 had high similarities to group 1 (Drosophila melanogaster DOP1 and Apis mellifera DOP1) and group 2 (D. melanogaster DopR99B, A. mellifera DOP2 and Papilio xuthus DOP1), respectively. When BmDopR1 and 2 were expressed in human embryonic kidney (HEK) cells, they responded to dopamine by increasing intracellular cAMP levels, thus indicating the presence of D1-like receptors. There were no clear differences in BmDopR1 and 2 mRNA levels between brain-suboesophageal ganglion complexes of diapause and nondiapause egg producers during pupal-adult development. BmDopR1 and 2 mRNAs were concentrated in the mushroom body calyx rather than in the suboesophageal ganglion. Taking into account the results of earlier experiments on excised regions corresponding to mushroom bodies, BmDopR1 and 2 in the mushroom body apparently play a role in the release of diapause hormone.

Comparative pharmacology of two D1-like dopamine receptors cloned from the silkworm Bombyx mori

“…The identified agonist-binding sites, an aspartic acid residue in TM3 (which forms an ion-pair with the protonated amino group of DA) and several serine residues in TM5 (which form hydrogen bonds with the m-and p-hydroxyl groups of DA), are conserved across all human catecholamine-binding GPCRs and insect phenolamine receptors, where similar agonist-binding modes are speculated for receptor-ligand interactions (Ohta et al, 2004;Xhaard et al, 2006;Huang et al, 2007). Such residues are also conserved in cloned insect D1-like receptors Mitsumasu et al, 2008), suggesting that the residues are arranged in the agonist-binding pocket and interact with DA and agonists such as ADTN. Although SKF is thought to interact with these conserved residues in vertebrate DA receptors (Pollock et al, 1992), other residues may be crucial to SKF binding.…”

“…AB362162 and AB162716) were cloned in our previous study (Mitsumasu et al, 2008). The open reading frames (ORFs) were amplified by PCR using DNA polymerase Ex Taq (Takara Shuzo Co., Ltd., Shiga, Japan), with the plasmid clones as templates.…”

“…We recently cloned orthologs of the two D1-like receptors from the silkworm Bombyx mori and named them BmDopR1 and BmDopR2 (Mitsumasu et al, 2008). Although the amino acid homology score between them was low (30%), both receptors showed an identical function, i.e., remarkable cAMP production by DA application in a heterologous system.…”

G Protein-Coupled Receptors as Target Sites for Insecticide Discovery

“…Activation of D1-like receptors stimulates cAMP synthesis via Gs protein alpha subunit (G a s), while activation of D2-like receptors inhibits cAMP formation via Gi protein alpha subunit (G a i) (Clark and Baro 2007 ) . Several dopamine receptors have been identi fi ed and characterized in D. melanogaster (Gotzes et al 1994 ;Sugamori et al 1995 ;Feng et al 1996 ;Han et al 1996 ;Hearn et al 2002 ;Draper et al 2007 ) , A. mellifera (Blenau et al 1998 ;Beggs et al 2005 ;Ebert et al 1998 ) , B. mori Mitsumasu et al 2008 ) and Papilio xuthus (Ono and Yoshikawa 2004 ) . A recent study identi fi ed a GPCR (DmDopEcR) from D. melanogaster , which can be activated by both dopamine and ecdysteroids.…”

Characterization of neuronal apoptosis in the ventral ganglia of postembryonic silkworms Bombyx mori (Lepidoptera: Bombycidae)

“…A reduction in the length of the connections between ganglia in B. mori leads to ganglionic fusion in the pupal stages: fusion of SOG into the brain, fusion of AG1 and AG2 into TG1 and TG2, and incorporation of AG6 into AG7/8 (Sato, 1998;Yamanaka et al, 2000;Hirashima et al, 2007;Mitsumasu et al, 2008). These ganglionic fusions are complete by day-4 of pupation.…”