Molecular and Cellular Endocrinology 273 (2007) 51–58 FXPRL-amide peptides induce ecdysteroidogenesis through a G-protein coupled receptor expressed in the prothoracic gland of Bombyx mori Ken Watanabe a , J. Joe Hull b , Teruyuki Niimi c , Kunio Imai d , Shogo Matsumoto b , Toshinobu Yaginuma c , Hiroshi Kataoka a,∗ a Department of Integrated Biosciences, Room 201, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan b The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako, Saitama 351-0198, Japan c Sericulture & Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan d Faculty of Bioresources, Mie University, Tsu 514-0008, Japan Received 6 July 2006; received in revised form 8 May 2007; accepted 8 May 2007 Abstract The FXPRL-amide peptide family (pyrokinin/PBAN family) consists of insect peptides that function broadly in insect life processes and are characterized by a conserved C-terminal motif. In the silkworm, Bombyx mori, sex pheromone biosynthesis and induction of embryonic diapause are regulated by peptides from this family. To elucidate other functions of Bombyx FXPRL-amide peptides, we analyzed the tissue expression patterns of two known Bombyx G-protein coupled receptors for these peptides. We found that the Bombyx diapause hormone receptor (BmDHR), is expressed in the prothoracic gland (PG), the organ which synthesizes and releases the insect molting hormones, ecdysteroids. Furthermore, diapause hormone (DH), a member of the Bombyx FXPRL-amide peptides, increases both intracellular Ca 2+ and cAMP concentrations and induces ecdysteroidogenesis in late fifth instar PGs coincident with BmDHR expression in the PGs. DH also has the highest prothoracicotropic activity among the FXPRL-amide peptides, which corresponds well to the ligand specificity of heterologously expressed BmDHR. These results demonstrate that FXPRL-amide peptides can function as prothoracicotropic factors through the activation of BmDHR and may play an important role in controlling molting and metamorphosis. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: FXPRL-amide peptide; Diapause hormone; PBAN; Pyrokinin 1. Introduction Most life processes of insects such as metamorphosis, repro- duction, and diapause, as well as numerous other behaviors, are controlled by various neuropeptides. Several insect neuropep- tides are multifunctional affecting numerous target organs, such as the FXPRL-amide peptide family (pyrokinin/PBAN fam- ily) that comprises several peptides from various insect species and which is characterized by a conserved C-terminal FXPRL- amide motif (Table 1). FXPRL-amide peptides mediate various functions such as muscle contractions (Holman et al., 1986), activation of sex pheromone biosynthesis (Kitamura et al., 1989; Raina et al., 1989), cuticle melanization (Matsumoto et al., ∗ Corresponding author. Tel.: +81 4 7136 3622; fax: +81 4 7136 3623. E-mail address: kataoka@k.u-tokyo.ac.jp (H. Kataoka). 1990), induction of embryonic diapause (Imai et al., 1991), and breaking of pupal diapause (Zhang et al., 2004; Zhao et al., 2004). In the silkworm, Bombyx mori, two FXPRL-amide peptides, diapause hormone (DH) and pheromone biosynthesis activat- ing neuropeptide (PBAN) have been isolated (Kitamura et al., 1989; Imai et al., 1991). DH is synthesized in the female sube- sophageal ganglion (SOG) and induces embryonic diapause by acting on developing oocytes during pupal–adult development (Yamashita, 1996). PBAN is also synthesized in the female SOG and stimulates sex pheromone synthesis in the pheromone glands of adult females (Teal et al., 1996). These peptides are encoded by a single gene (DH-PBAN gene) along with three other FXPRL-amide peptides, -, - and -SGNP (Sato et al., 1993). All of these peptides, with the exception of -SGNP, can activate pheromone biosynthesis as well as induce the pro- duction of diapause eggs; -SGNP has no effect on diapause 0303-7207/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.mce.2007.05.008