Juvenile-hormone-binding protein from silk gland of Galleria mellonella

Juvenile hormone regulation of Drosophila Epac--a guanine nucleotide exchange factor

Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to characterize the effects of juvenile hormone (JH) on Epac (Exchange Protein directly Activated by Cyclic AMP; NM_001103732), a guanine nucleotide exchange factor for Rap1 in Drosophila S2 cells. JH treatment led to a rapid, dose-dependent increase in Epac relative expression ratio (RER) when compared to treatment with methyl linoleate (MLA) that lacks biological activity. The minimal level of hormone needed to elicit a response was 100 ng/ml. Time-course studies indicated a significant rise in the RER 1h after treatment. S2 cells were challenged with 20-hydroxyecdysone and a series of compounds similar in structure to JH to determine the specificity of the response. Methoprene and JH III displayed the greatest increases in RER. Late third instar (96 h) Drosophila were exposed to diet containing methoprene (500 ng/g diet); significantly higher RERs for Epac were observed 12h after exposure. JH had no effect on Epac RERs in the human cell line HEK-293.

The presence of estradiol-17beta and its specific binding sites in posterior silk gland of Bombyx mori

Although estradiol-17beta (E2) is known to be a vertebrate sex steroid, its presence in insects, particularly in Bombyx mori, has recently created considerable sensation regarding its significance in insect life. The specificity of estradiol action on the posterior silk gland (PSG) of B. mori has been previously assessed by the use of ICI-182780 as a specific receptor antagonist for estradiol. The present study provides evidence for systematic changes in the titer of estradiol-17beta in B. mori and its specific binding sites in the posterior silk gland according to the physiological age of fifth instar larvae. The changes in the estradiol level in the PSG after E2 treatment have also been determined to assess whether the administered estradiol has been taken up by the silk gland cells and whether the effect of exogenously administered E2 on the PSG is direct. The correlation in the profile of E2 binding sites with the endogenous estradiol level of PSG on different days of fifth instar larvae suggests that the level of binding sites in the PSG is regulated by the estradiol titer and that E2 may have some biological function in B. mori. Scatchard analysis of E2 binding sites in the PSG on 9th day of fifth instar larvae reveals that it consists of only one type of binding component. The dissociation constant (Kd) and maximum binding capacity (Bmax) of this putative E2 receptor have been found to be 8.98 +/- 0.744 nM and 55.8 +/- 5.53 fmol/mg cytosolic protein, respectively. The study thus indicates an involvement of the putative receptor in E2-mediated action on the silk gland of B. mori and paves a pathway for further evaluation of the physiological relevance of the presence of vertebrate steroids in insects.

The juvenile hormone analogue, methoprene, inhibits ecdysterone induction of small heat shock protein gene expression

The small heat shock protein (hsp) genes of Drosophila are expressed in cultured cells in response to the moulting hormone, ecdysterone. We show here that juvenile hormone (JHIII) and the juvenile hormone analogue, methoprene, inhibit that induction in a dose-dependent manner. Heat shock induction is not inhibited. In transient expression studies using S3 line cells transfected with EcRE-CAT constructs, methoprene inhibition was found to require a 2-hr pretreatment (before ecdysterone addition), and methoprene's continued presence was essential. Farnesol, farnesyl acetate, and retinoic acid did not cause inhibition. Several models of methoprene inhibition are discussed.

Effects of juvenile hormone on the ecdysone response of Drosophila Kc cells

Drosophila Kc cells are ecdysone-responsive: hormone treatment leads rapidly to increased synthesis of several ecdysone-inducible polypeptides (EIPs) and to commitment to eventual proliferative arrest. Later, the treated cells undergo morphological transformation, cease to proliferate, and develop new enzymatic activities, notably, acetylcholinesterase (AChE) activity. These responses have proven useful as models for studying ecdysone action. Here we report the sensitivity of Kc cells to another important insect developmental regulator--juvenile hormone (JH). We find that JH inhibits some, but not all, aspects of the ecdysone response. When Kc cells are treated with ecdysone in the presence of either natural JHs or synthetic analogues, the morphological and proliferative responses are inhibited and AChE induction is blocked. Most striking is that JHs protect the cells from the rapid proliferative commitment induced by ecdysone alone. The JH effects exhibit reasonable dose-response curves with half-maximal responses occurring at very low JH concentrations. Nonetheless, even at high JH concentrations the inhibitory effects are incomplete. It is interesting that EIP induction appears to be refractory to JH. It seems clear that JH is not simply a generalized inhibitor of ecdysone-induced responses.

Juvenile-hormone-binding protein from the hemolymph of Galleria mellonella (L). Isolation and characterization

A juvenile-hormone-binding protein (JHBP) has been isolated from Galleria mellonella hemolymph by gel filtration, phosphocellulose chromatography, and by chromatofocusing. The isolated protein is homogeneous as judged by column chromatography and gel electrophoresis in the presence and absence of denaturing agent. It has a relative molecular mass of 32,000, Stokes radius 2.4 nm, sedimentation coefficient of 2.3 S, molar absorption coefficient at 280 nm epsilon = 2.34 X 10(4) M-1 cm-1, and is composed of a single polypeptide chain. Chromatofocusing analysis (pI 8.6) and isoelectric focusing (pI 8.1) indicate that the JHBP is an alkaline protein. Its amino acid composition and fluorescence absorption spectra indicate that the protein does not contain tryptophan residues. The protein exhibits one class of binding sites for juvenile hormone (JH), 0.8 per molecule, with the following dissociation constants: JH I, 8.5 X 10(-8) M; JH II, 7.2 X 10(-8) M; JH III, 47 X 10(-8) M. The JHBP binds (10R, 11S)-JH II enantiomer with 2.3-times higher affinity then (10S, 11R)-JH II enantiomer. The pH optimum of binding is 7.0.