POTENT PHEROMONOTROPIC MYOTROPIC ACTIVITY OF A CARBORANYL PSEUDOTETRAPEPTIDE ANALOG OF THE INSECT PYROKININ/PBAN NEUROPEPTIDE FAMILY ADMINISTERED VIA INJECTION OR TOPICAL APPLICATION/
Rj. Nachman et al., POTENT PHEROMONOTROPIC MYOTROPIC ACTIVITY OF A CARBORANYL PSEUDOTETRAPEPTIDE ANALOG OF THE INSECT PYROKININ/PBAN NEUROPEPTIDE FAMILY ADMINISTERED VIA INJECTION OR TOPICAL APPLICATION/, Peptides, 17(5), 1996, pp. 747-752
A pseudotetrapeptide analogue of the pyrokinin/PBAN or FXPRLamide fami
ly (Cbe-Thr-Pro-Arg-Leu-NH2; Cbe = 2-o-carboranylethanoyl-), in which
the phenyl ring of the Phe side chain is replaced with the hydrophobic
cage-like o-carborane moiety, was synthesized and found to be 10-fold
more potent than cockroach leucopyrokinin on an isolated cockroach hi
ndgut bioassay system. In contrast with the naturally occurring peptid
e, the myostimulatory activity could not be immediately reversed follo
wing a saline rinse, providing evidence that the pseudopeptide analogu
e binds very strongly to the receptor. Once the analogue reaches the r
eceptor, strong receptor binding characteristics may allow it to avoid
inactivation by hemolymph peptidases. Although it has an eightfold sm
aller sequence than the endogenous 33-membered pheromone biosynthesis
activating neuropeptide (PBAN), the carboranyl analogue is 10-fold mor
e potent in an in vivo pheromonotropic bioassay of the female tobacco
budworm moth Heliothis virescens, demonstrating that the small, C-term
inal pentapeptide pyrokinin core analogue contains all the structural
information necessary to fully activate pyrokinin receptors. In contra
st with PBAN, the amphiphylic carboranyl analogue elicits pheromone pr
oduction following topical application in aqueous solution to the late
ral abdominal surface of H. virescens. providing a noninvasive means o
f inducing pheromone production in moths. The analogue can potentially
serve as a useful tool to insect researchers studying, and/or attempt
ing to disrupt, physiological processes regulated by pyrokinin-like ne
uropeptides in insects. A possible role for this and related pyrokinin
analogues in future pest insect management strategies is briefly disc
ussed.