Submitted to: Regulatory Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 1994
Publication Date: N/A
Interpretive Summary: Neuropeptides are short chains of amino acids (the building blocks of proteins) that are made by cells in the nervous system of all animals. The function of neuropeptides in the animal is to provide communication between cells and tissues in order to cause a response. They are often called hormones and are considered to be the master regulators of most body functions, both in insects and higher animals. They tend to be present in tiny amounts in the animal. Usually the insect neuropeptides are of different structure than those found in higher animals. This report describes the partial structural characterization of a new neuropeptide from brain extracts of the locust. Synthesis of a fragment peptide composed of the last nine amino acids showed the core sequence required for biological activity was within the fragment. Distribution of the peptide within the nervous system of the locust suggest that this peptide functions sas a neurotransmitter and not a neurohormone. Structural characterization of neuropeptides is the first step necessary in devising new chemical and molecular biology strategies for insect management.
A blocked neuropeptide that suppresses the motility of the cockroach hindgut has been isolated from an extract of 9000 brain-corpora cardiaca- corpora allata-suboesophageal ganglion complexes of Locusta migratoria. Biological activity was monitored during HPLC purification by observing the myoinhibiting activity of column fractions on the isolated hindgut of Leucophaea maderae. Due to the low amount of material left after deblocking, this myoinhibiting peptide--designated as locustamyoinhibin or Lom-MIH--could only be partially sequenced: pGlu-X-Tyr-X'-Lys-Gln-Ser-Ala- Phe-Asn-Ala-Val-Ser-NH2. Nevertheless, the carboxy-terminal nonamer sequence (Lom-MIH**5-13) was synthesized and also displayed myoinhibiting activity, indicating that the biologically active core lies in the carboxy- terminal sequence. Lom-MIH shows no sequence similarities with other peptides from vertebrate or invertebrate sources and is the third myoinhibiting peptide identified in Locusta migratoria. A polyclonal antiserum was raised against Lom-MIH**5-13 and used to investigate the distribution of immunoreactive peptide in the central nervous system and its associated neurohaemal structures. Two groups of neurons with somata in the optic lobes show locustamyoinhibin (Lom-MIH)-like immunoreactivity. These groups have somata at the dorsal and ventral edge of the lamina ganglionaris. The neurons have dense ramifications in the lamina, with processes extending into the first optic chiasma and into the accessory medulla. Four cell bodies were detected in the protocerebrum, and two cells were found at the externo-lateral edge of the tritocerebrum. No immunoreactive perikarya could be observed in the suboesophageal ganglion nor in the ganglia of the ventral nerve cord.