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Published on: August 22, 2019
G protein-coupled receptor for diapause hormone, an inducer of Bombyx embryonic diapause
Takashi Homma1, Ken Watanabe, Shuichiro Tsurumaru
1Sericulture and Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Abstract:
Bombyx diapause hormone was the first chemical substance identified as a maternal control factor that arrests offspring development. However, the molecular mechanisms by which the hormone transduces the signal to the oocyte that induces embryonic diapause immediately after mesoderm segmentation are not fully understood. Here, we describe a cDNA for a G protein-coupled diapause hormone receptor with seven transmembrane domains. Its amino-acid sequence shows a high level of similarity to the receptors of mammalian neuromedin U and insect regulatory peptide, an FXPRL-amide C-terminus. When expressed in a Xenopus oocyte system, the receptor exhibited the highest affinity (EC(50), approximately 70nM) for diapause hormone, when compared with other Bombyx FXPR/KL-amide peptides. Diapause hormone without amidation at the C-terminus, which never induces embryonic diapause in vivo, had no effect in this heterologous expression system. The mRNA is expressed in the ovaries during Bombyx pupal-adult development. These results strongly indicate that the cDNA encodes the diapause hormone receptor.
Insights
Scientists identified a G protein-coupled receptor for Bombyx diapause hormone, crucial for insect development arrest. This discovery sheds light on the maternal control factor
Area of Science:
- Molecular Endocrinology
- Insect Physiology
- Developmental Biology
Background:
- Bombyx diapause hormone is the first identified maternal factor controlling offspring development arrest.
- Molecular mechanisms of diapause hormone signal transduction to oocytes remain unclear.
- Embryonic diapause occurs immediately after mesoderm segmentation in Bombyx.
Purpose of the Study:
- To identify and characterize the receptor for Bombyx diapause hormone.
- To elucidate the molecular basis of diapause hormone signaling in oocytes.
Main Methods:
- Cloning and expression of a G protein-coupled receptor (GPCR) cDNA in a Xenopus oocyte system.
- Ligand binding assays to determine receptor affinity for diapause hormone and related peptides.
- Analysis of receptor mRNA expression in Bombyx ovaries.
Main Results:
- A cDNA encoding a seven-transmembrane domain GPCR, homologous to neuromedin U receptors, was identified.
- The expressed receptor showed high affinity for amidated diapause hormone (EC50 ≈ 70 nM).
- Non-amidated diapause hormone did not activate the receptor, mirroring in vivo observations.
- Receptor mRNA is expressed in ovaries during Bombyx pupal-adult development.
Conclusions:
- The identified cDNA likely encodes the Bombyx diapause hormone receptor.
- This receptor plays a critical role in mediating maternal control of embryonic diapause.
- The findings provide a molecular basis for understanding diapause induction.
