|Nachman, Ronald - Ron|
Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2006
Publication Date: 6/16/2006
Citation: Taneja-Bageshwar, S., Strey, A.A., Zubrzak, P., Pietrantonio, P.V., Nachman, R.J. 2006. Comparative structure-activity analysis of insect kinin core analogs on recombinant kinin receptors from southern cattle tick Boophilus microplus (Acari: Ixodidae) and mosquito Aedes aegypti (Diptera: Culicidae). Archives of Insect Biochemistry and Physiology. 62:128-140. Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling invertebrate pests such as insects and ticks. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in invertebrates such as ticks and insects to regulate vital functions. Nevertheless, neuropeptides in and of themselves hold little promise as pest control agents because of susceptibility to being degraded in the target pest. We must design neuropeptide mimics that resist degradation by enzymes in the digestive tract and blood of pest invertebrates and interact with the active site within the agricultural or medical pest in such a way as to either over-activate or block critical, neuropeptide-regulated life functions. We report on a comparison of the molecular characteristics required for neuropeptides of the insect kinin class to interact with active sites in a mosquito and a tick, medical pests that plague man and livestock. Included in this study is the identification of a potent modified neuropeptide with enhanced resistance to degradation within the target pest. This biostable version of the neuropeptide can serve as a tool to further understand the role of this neuropeptide class in regulating water balance in the mosquito; and to understand their function in ticks, for which nothing is known. This discovery will aid in the design of neuropeptide-like compounds capable of disrupting critical life functions in insects and ticks. This work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling invertebrate pests, including ticks and insects,in an environmentally friendly fashion.
Technical Abstract: The systematic analysis of structure-activity relationships of insect kinins on two heterologous receptor-expressing systems is described. Previously, kinin receptors from the southern cattle tick, Boophilus microplus (Canestrini, 1888) (Holmes et al 2001; Holmes et al., 2003) and the dengue vector, the mosquito Aedes aegypti (L.) (Pietrantonio et al., 2005) were functionally and stably expressed in CHO-K1 cells. In order to determine which kinin residues are critical for the peptide-receptor interaction, kinin core analogs were synthesized as an Ala-replacement series of the peptide FFSWGa and tested by a calcium bioluminescence plate assay. The amino acids Phe1 and Trp4 were essential for activity of the insect kinins in both receptors. It was confirmed that the pentapeptide kinin core is the minimum sequence required for activity and that the C-terminal amide is also essential. In contrast to the tick receptor, a large increase in efficacy is observed in the mosquito receptor when the C-terminal pentapeptide is N-terminally extended to a hexapeptide. The aminoisobutyric acid (Aib)-containing analog, FF[Aib]WGa, was as active as superagonist FFFSWGa on the mosquito receptor in contrast to the tick receptor where it was statistically more active than FFFSWGa by an order of magnitude. This restricted conformation Aib analog provides information on the conformation associated with interaction of the insect kinins with these two receptors. Furthermore, the analog FF[Aib]WGa has been previously shown to resist degradation by the peptidases ACE and nephrilysin and represents an important lead in the development of biostable insect kinin analogs that ticks and mosquitoes cannot readily deactivate.