|Nachman, Ronald - Ron|
|Vanden Broeck, Jozef|
Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2009
Publication Date: 3/10/2010
Citation: Poels, J., Birse, R.T., Nachman, R.J., Fichna, J., Janecka, A., Vanden Broeck, J., Nassel, D.R. 2010. Characterization and distribution of NKD, a receptor for Drosophila tachykinin-related peptide 6. Peptides. 30:545-556. 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 insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. Nevertheless, these neuropeptides in and of themselves hold little promise as pest control agents because of susceptibility to being degraded in the target pest, and inability to pass through the outside skin (cuticle) and/or digestive tract. We must design neuropeptide mimics that resist degradation by enzymes in the digestive tract and blood of pest insects, and that interact with the active site within the agricultural pest in such a way as to either over-activate or block critical, neuropeptide-regulated life functions. We report on the characterization and distribution of the active site called ‘NKD’ for a member of the ‘tachykinin-related’ class of neuropeptides from Drosophila melanogaster, a model for important pest flies. The spatial distribution of the ‘NKD’ active site within the fly nervous system is quite different from another ‘tachykinin-related’ active site known as ‘DTKR’, and the former responds only to a specific, unusual member of this class of hormones. The results indicate the two active sites each regulate different systems of nerve circuits. This discovery will aid in the design of neuropeptide-like compounds capable of disrupting the locomotory, olfactory, and diuretic functions of these and other flies. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.
Technical Abstract: Neuropeptides related to vertebrate tachykinins have been identified in Drosophila and are referred to as drosotachykinins, or DTKs. Two Drosophila G protein-coupled receptors, designated NKD (neurokinin receptor from Drosophila; CG6515) and DTKR (Drosophila tachykinin receptor; CG7887), display sequence similarities to mammalian tachykinin receptors. Whereas DTKR was shown to be activated by DTKs [2,24] and was localized by immunocytochemistry in Drosophila central nervous system (CNS), agonist-dependent activation and distribution of NKD have not yet been investigated in depth. In the present study, we have challenged NKD-expressing mammalian and insect cells with a library of Drosophila neuropeptides and discovered DTK-6 as a specific agonist that can induce a calcium response in these cells. In addition, we have produced antisera to sequences from NKD protein to analyze receptor distribution. We found that NKD is less abundantly distributed in the central nervous system than DTKR, and only NKD was found in the intestine. In fact, the two receptors are distributed in mutually exclusive patterns in the CNS. The combined distribution of the receptors in brain neuropils corresponds well with the distribution of DTKs. Most interestingly, NKD appears to be activated only by DTK-6, known to possess an Ala-substitution in an otherwise conserved C-terminal core motif. Our findings suggest that NKD and DTKR provide substrates for two functionally and spatially separated peptide signaling systems.