|Coast, Geoffrey - BIRBECK COLLEGE, UK|
|Schooley, David - UNIV OF NEVADA/RENO|
Submitted to: Journal of Experimental Biology Online
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 2007
Publication Date: November 2, 2007
Citation: Coast, G.M., Nachman, R.J., Schooley, D.A. 2007. An antidiuretic peptide (Tenmo-ADFb) with kinin-like diuretic activity on Malpighian tubules of the house cricket, Acheta domesticus. Journal of Experimental Biology Online. 210:3979-3989. 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. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. We report that a neuropeptide known as Tenmo-ADFb regulates diuretic activity in a model insect, the house cricket, and provide information on its mechanism of action. The above results suggest that development of metabolically stable versions of this neuropeptide could lead to agents capable of disrupting water balance and digestion in this insect, as well as other insects that pose as pests of agriculture. 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: A. domesticus has anantidiuretic hormone that acts to reduce Malpighian tubule secretion. Identified peptides know to reduce secretion of primary urine (Tenmo-ADFa and ADFb, and Manse-CAP2b) were tested as candidates for this unidentified hormone, along with their second messenger cyclic GMP. Only Tenmo-ADFb activity was comparable to that of a kinin, Achdo-Kll, but much less potent. Its activity was unaffected by deleting either the six N-terminal residues or the C-terminal phenylalanine. At high concentrations, tubule secretion is doubled by Tenmo-ADFb amd Achdo-Kll, but their actions are non-additive, suggesting they target the same transport process. Both stimulate a non-selective KCl and NaCl diuresis, which is consistent with the opening of a transepitheliam Cl- conductance. In support of this, diuresis was prevented by a 10-fold reduction in bathing fluid (Cl-), and both peptides caused the lumen-positive transepithelial voltage to collapse. The Cl- conductance could be either paracellular or transcellular, although the latter appears unlikely because changes in transepithelial voltage are not accompanied changes in basal membrane voltage. Moreover, the Cl- channel blockers DPC and NPPB do not prevent diuresis, eventhough the former reduced the absolute rate of secretion. This is the first report of an antidiuretic factor (Tenmo-ADFb) having diuretic activity. Although their actions are indistinguishable, Tenmo-ADFb is unlikely to act at a kinin receptor, because its core sequence (residues 7-12) lacks the Phe and Trp residues critical for kinin activity.