Title: Molecular cloning and functional characterization of the diapause hormone receptor in the corn earworm Helicoverpa zea Authors
Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2014
Publication Date: March 15, 2014
Citation: Jiang, H., Wei, Z., Nachman, R.J., Park, Y. 2014. Molecular cloning and functional characterization of the diapause hormone receptor in the corn earworm Helicoverpa zea. Peptides. 53:1-2. Interpretive Summary: Insect pests have developed resistance to several conventional pesticides, and new approaches are needed for pest management. Although neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions, the neuropeptides hold little promise as pest control agents because they can be degraded in the target pest. New, selective control agents may be developed by designing mimics of these neuropeptides that resist degradation and either inhibit or over-stimulate critical neuropeptide-regulated life functions. We report on the isolation, identification and characterization of the active site for the diapause hormone in the corn earworm, an important agricultural pest. In moths, this hormone regulates the entry into a protective state of dormancy that is critical for winter survival. The work identified several synthetic, stable mimics that are either more active than, or are able to block, the natural hormone. This discovery, and the new information gained from it, will aid in the design of neuropeptide-like compounds capable of disrupting the survival mechanisms of these and related moths. This may eventually lead to development of practical neuropeptide-like substances that can effectively control crop pest insects in an environmentally friendly fashion.
Technical Abstract: The diapause hormone (DH) in the heliothine moth has shown its activity in termination of pupal diapause, while the orthology in the silkworm is known to induce embryonic diapause. In the current study, we cloned the diapause hormone receptor from the corn earworm Helicoverpa zea (HzDHr) and tested its ligand specificities in a heterologous reporter system. HzDHr expressed in Chinese Hamster Ovary (CHO) cells, which were co-transfected with the aequorin reporter, was used to measure the ligand activities. A total of 68 chemicals, including natural DH analogs and structurally similar peptide mimetics, were tested for agonistic and antagonistic activities. Several peptide mimetics with a 2-amino-7-bromofluorene-succinoyl (2Abf-Suc) N-terminal modification showed strong agonistic activities; these mimetics included 2Abf-Suc-F[dA]PRLamide, 2Abf-Suc-F[dR]PRLamide, 2Abf-Suc-FKPRLamide and 2Abf-Suc-FGPRLamide. Drosophila melanogaster ecdysis triggering hormone (FFLKITKNVPRLamide), which shares a C-terminal PRLamide with DH, was found to exhibit antagonistic activity against native DH. Interestingly, HzDHr does not discriminate between DH (WFGPRLamide C-terminal motif) and another closely related endogenous peptide, pyrokinin 1 (a pyrokinin superfamily sub-class that features a FXPRXamide C-terminal motif as opposed to WFGPRLamide). We provide large-scale in vitro data that serve as a reference for the development of agonists and antagonists to disrupt the DH signaling pathway.