Purification of the Drosophila Kc cell juvenile hormone binding protein

Larva lights: a decade of photoaffinity labeling with juvenile hormone analogues

The introduction of photoaffinity labeling into the mode of action of insect hormones and pheromones started 12 yr ago with the photoaffinity labeling of juvenile hormone binding proteins (JHBPs) from cockroaches in the laboratory of the late John K. Koeppe. Applying this technique to Manduca sexta led ultimately to a three-laboratory collaborative project that has begun to dissect the molecular basis for JH transport, metabolism, and nuclear binding and gene activation in Lepidoptera. This review provides (1) a history of the first experiments; (2) an idea of the breadth of the technique in the arthropod classes Insecta, Crustacea, and Arachnida; and (3) evidence for the depth of the technique in unearthing key details about three different types of the molecular action of JH in M. sexta.

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.

Yolk polypeptide gene expression in cultured Drosophila cells

The transfer of chimaeric plasmids to Drosophila melanogaster cell lines has been examined as a system for investigation of the hormonal regulation of the genes coding for D. melanogaster yolk polypeptide 1 (YP1) and Locusta migratoria vitellogenin B (VgB). Constructs containing promoters and putative 5'-regulatory sequences from these genes, ligated to bacterial chloramphenicol acetyltransferase (CAT) coding DNA, were transfected into Drosophila Kc (Kc-H) and S3 cells, and transient expression of CAT was assayed. Activity was expressed both from the homologous promoter of pYP1CAT and from the heterologous locust promoter of pVgCAT at comparable levels. In S3 cells, with calcium phosphate-mediated transfer of pYP1CAT there was a twofold induction of CAT activity after the addition of 10(-6) M ecdysterone, but no hormonal stimulation was noted when the polycation polybrene was used to achieve transfection. For Kc cells, calcium phosphate was ineffective for transfection, and after transfection with polybrene neither pYP1CAT nor pVgCAT was induced by the juvenile hormone (JH) analog methoprene. It is concluded that S3 cells may be useful for investigating the molecular basis of gene regulation by ecdysteroids, but conditions suitable for the analysis of JH action have not yet been established.

Binding proteins for methyl farnesoate in lobster tissues: detection by photoaffinity labeling

Methyl farnesoate (MF) is secreted by the mandibular organs of crustaceans, but its physiological role and biochemical distribution are only partially known. Characterization of specific MF binding proteins (MFBP) in homogenates of tissues of the American lobster, Homarus americanus, was achieved by photoaffinity labeling with tritium-labeled farnesyl diazomethyl ketone (3H-FDK). The tissues selected include epidermis, tail muscle, central nervous system, eyestalk, hemolymph, hepatopancreas, ovaries, testes, and Y-organ. Both high-speed pellets and supernatants were tested. Competing ligands employed to verify specificity of light-induced covalent modification included MF, methoprene, and unlabeled FDK. A 40-kDa band was labeled strongly in the hemolymph; the labeling was displaced in the presence of a 100-fold excess of unlabeled MF. Although many other tissues had proteins which labeled with 3H-FDK, none of these showed competition by MF. This MFBP is thus functionally analogous to the hemolymph JH-binding proteins of insects.