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United States Department of Agriculture

Agricultural Research Service

Title: Potent Pheromonotropic/myotropic Activity of a Carboranyl Pseudotetrapeptide Analog of the Insect Pyrokinin/pban Neuropeptide Family Administered Via Injection Or Topical Application

Authors
item Nachman, Ronald
item Teal, Peter
item Radel, Peggy - UNIV. OF CA/SAN FRANCISCO
item Holman, G
item Abernathy, Rella - UNIV. OF CA/SAN FRANCISCO

Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 1996
Publication Date: N/A

Interpretive Summary: Neuropeptides are small chains of amino acids (the building blocks of proteins). In insects as well as other higher forms of animal life, neuropeptides act as hormones to control a wide variety of life processes such as digestion, muscular movement, excretion, etc. Because neuropeptides are so important in regulating life processes in insects, it is possible to exploit these chemicals to develop more effective methods o controlling pest insects. However, the neuropeptides themselves will not work as insecticides because they are very unstable, because they degrade easily when acted upon by enzymes in insects, and because it would be difficult and likely impossible to develop acceptable methods for their application (they do not penetrate the outside skin or cuticle of insects). These studies were designed to develop neuropeptide-like compounds that retain appropriate biological activity but that overcome the problems associated with neuropeptides themselves. We have developed such a compound that, when injected into the tobacco budworm moth, has effects on reproduction that are more pronounced than even the original neuropeptide itself. This work is very important in efforts to exploit neuropeptide technology in the development of a new class of pest insect control agents that will be more effective, more selective, and more environmentally friendly than the conventional pesticides that are currently used to control many pest insects. 

Technical Abstract: A pseudotetrapeptide analog of the pyrokinin/PBAN or FXPRLamide family (Cbe-Thr-Pro-Arg-Leu-NH2; Cbe=2-o-carboranylethanoyl-), in which the phenyl ring of the Phe sidechain is replaced with the hydrophobic cage-like o- carborane moiety, was synthesized and found to be 10 fold more potent than leucopyrokinin on an isolated cockroach hindgut bioassay system. In contrast with the naturally occuring peptide, the myostimulatory activity could not be reversed following a saline rinse, providing evidence that the pseudopeptide analog binds irreversibly to the receptor. Once the analog reaches the receptor, strong receptor binding characteristics may allow it to avoid inactivation by haemolymph peptidases. Although it has an 8 fold smaller sequence than the endogenous 33-membered pheromone biosythesis activating neuropeptide (PBAN), the carboranyl analog is 10 fold more potent in an in vivo pheromonotropic bioassay of the female tobacco budworm mmoth Helicoverpa virescens. In contrast with PBAN, the amphiphyllic carboranyl analog elicits pheromone production following topical application in aqueous solution to the lateral abdominal surface of H. virescens, providing a noninvasive means of inducing pheromone production in moths. The analog can potentially serve as a useful tool to insect researchers studying, and/or attempting to disrupt, normal reproduction and behavior in Helicoverpa and related insects.

Last Modified: 10/21/2014
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