Investigating Opioid-Like Signaling Pathways in the Tobacco Hornworm, Manduca sexta
Gurleen Kaur, Tarnampreet Kaur
Department of Biology
Faculty Supervisor: Megumi Fuse
Leucopyrokinin (LPK) is a neuropeptide initially isolated from the cockroach but is part of the larger PBAN/pyrokinin peptide family in insects that have numerous roles including pheromone biosynthesis and muscle contraction. When injected into mice, LPK has been shown to induce antinociception (analgesia) mediated through opioid receptors, even though it has a different structure and sequence from opioid peptides in vertebrates. We have shown the effects of LPK on antinociception in the hornworm, Manduca sexta. The active fragment of LPK reduced sensitization of the defensive strike response in M. sexta, in a dose-dependent manner, using a touch assay with von Frey filaments. The response, however, was not blocked by the opioid-receptor inhibitor, Naloxone, as it was in mice. To explore the molecular basis of these findings, we are assessing whether insects have opioid receptors through a bioinformatics approach looking at insect genomes. This analysis includes retrieving vertebrate opioid receptor sequences from databases as reference queries, and conducting Basic Local Alignment searches against the annotated genomes of various insects including M. sexta. Our preliminary results coupled with the bioassay results suggest that when administered in insects, LPK may use an alternate pain-inhibiting pathway other than the opioid pathway noted in mice.