A 28-kDa cerebral neuropeptide fromManduca sexta: Relationship to the insect prothoracicotropic hormone

Abstract

1. A 28-kDa peptide from the brain of the tobacco hornworm, Manduca sexta, was purified via HPLC. The peptide copurified with the insect neurohormone, prothoracicotropic hormone (PTTH), through two HPLC columns. 2. Immunocytochemistry using polyclonal antibodies against the 28-kDa peptide revealed that the peptide was produced in the same protocerebral neurons that produce PTTH. Western blot analysis demonstrated that the 28-kDa peptide and big PTTH are different molecules. 3. A PTTH in vitro bioassay indicated that despite having chromatographic properties similar to those of big PTTH and being produced by the same neurons, the 28-kDa peptide did not have PTTH activity. 4. Amino acid sequence analysis yielded a 27 N-terminal amino acid sequence that had no similarity with known peptides. 5. Immunocytochemical studies revealed that the 28-kDa peptide is present as early as 30% embryonic development and is absent by adult eclosion. This is in contrast to big PTTH, which is expressed throughout the Manduca life cycle. 6. These data suggest that the 28-kDa peptide is another secretory phenotype of the lateral neurosecretory cell group III (L-NSC III) which may have functions distinct from those for big PTTH or may act synergistically with big PTTH.

Nervous control of juvenile hormone biosynthesis in Locusta migratoria.

“…PTTH itself may play this role (23,26) or other small peptides produced during the processing of the big PTTH precursor molecule (prepro-PTTH) might be involved (23,39). In Manduca sexta an additional 28-kDa peptide unrelated to big PTTH is also produced by the prothoracicotropes and packaged into neurosecretory vesicles, although its function is as yet unclear (40).…”

Regulation of ecdysone production in Drosophila by neuropeptides and peptide hormones

“…An advantage of Manduca is that it has paired prothoracic glands which produce ecdysone at the same rate, which means that experimental manipulation can be conducted on one gland, with the other serving as a control [55]. Studies in Manduca found that PTTH was also synthesized in this species, but the peptide was produced in two different sizes; big PTTH and small PTTH [56,57]. Both of these peptides have been shown to stimulate Manduca prothoracic glands to produce ecdysone in vitro [58].…”