Title: Evaluation of insect CAP2b analogs with either an (E)-alkene, trans- or a (Z)-alkene, cis- Pro isostere identifies the Pro orientation for antidiuretic activity in the stink bug Authors
|Lopez, Juan DE Dios|
Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 24, 2012
Publication Date: March 15, 2013
Citation: Nachman, R.J., Wang, X.J., Etzkorn, F.A., Kaczmarek, K., Zabrocki, J., Lopez, J., Coast, G.M. 2013. Evaluation of insect CAP2b analogs with either an (E)-alkene, trans- or a (Z)-alkene, cis- Pro isostere identifies the Pro orientation for antidiuretic activity in the stink bug. Peptides. 41:101-106. 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 development of a new analog mimic of the ‘CAP2b’ neuropeptide class that clearly identifies the 3-D structure adopted by the natural hormones at the active site from the Green stink bug Acrosternum hilare, an important agricultural pest. In stink bugs, CAP2b regulates water balance by specifically preventing the insect from entering a debilitating state of dehydration. The work further identifies a new scaffold with which to design and develop mimics with enhanced biostability. This discovery will aid in the design of neuropeptide-like compounds capable of disrupting the water balance of these and related stink bugs and potentially synergize the effectiveness of traditional insecticides used to control these pests. This information will aid in the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.
Technical Abstract: The CAP2b neuropeptide family plays an important role in the regulation of the processes of diuresis and/or antidiuresis in a variety of insects. While Manse-CAP2b (pELYAFPRVamide) and native CAP2bs elicit diuretic activity in a number of species of flies, native CAP2b sequences have been shown to elicit antidiuretic activity in the kissing bug Rhodniius prolixus and the green stink bug Acrosternum hilare, the latter being an important pest of cotton and soybean in the southern United States. Analogs of CAP2b containing either a (Z)-alkene, cisPro or an (E)-alkene, transPro isosteric component were synthesized and evaluated in an in vitro stink bug diuretic assay, which involved measurement of fluid secretions of Malpighian tubules isolated from A. hilare. The conformationally constrained transPro analog demonstrated statistically significant antidiuretic activity, whereas the cisPro analog failed to elicit any activity. The results provide strong evidence for adoption of a trans orientation for the Pro in CAP2b neuropeptides during interaction with receptors associated with the antidiuretic process in the stink bug. In addition, the results provide further evidence for a theory of ligand-receptor coevolution between the CAP2b and pyrokinin/PBAN neuropeptide classes, both members of the ‘-PRXamide’ superfamily. The work further identifies a scaffold with which to design mimetic CAP2b analogs as potential leads in the development of environmentally favorable pest management agents capable of disrupting CAP2b-regulated diuretic systems.