|Title: ||Signalling peptides in locusts: an overview|
|Authors: ||De Loof, Arnold|
Vanden Broeck, Jozef
|Issue Date: ||1997 |
|Series Title: ||Metalaptea vol:17 issue:2 pages:19|
|Abstract: ||Proctolin was the very first neuropeptide identified in an invertebrate. It was isolated from the cockroach, Periplaneta americana by Brown and Starrat (1975). Later, it was also found in other insect species, including locusts. The first peptide isolated from a locust was adipokinetic hormone I (AKH I), a neurohormone that mobilizes lipids from the fat body. No other insect neuropeptides were isolated until 1986 (AKH II). As the result of improvements in extraction procedures, HPLC- and protein sequencing equipment, and in immunological procedures, signalling peptide purification started to boom at a tremendously fast rate from the mid-1980s onwards. Currently, the locusts Locusta migratoria and Schistocerca gregaria are the two insect species from which the largest number of signalling peptides have been isolated and sequenced (approximately 60).
In fact, the study of locust neuropeptides has greatly contributed to the insight that the endocrine systems of vertebrates and invertebrates have more elements in common than could have been imagined a decade ago. Locusts have peptides belonging to the insulin-, tachykinin-, CRF-, gastrin/CCK-, and vasopressin families. In addition, they have numerous peptides which do not as yet have counterparts in vertebrates. Myotropic assays have played a major role in the isolation and subsequent structural characterization of locust signalling peptides. They have been responsible for the discovery of locustamyotropins (4), locustapyrokinins (2), locustatachykinins (5), locustakinin (1), Locusta accessory gland myotropins (2), locustasulfakinin (1), Locusta cardioactive peptide (1), and a whole series of Locusta myoinhibiting peptides which incude ten allatostatins (schistostatins). Members of myotropic peptide families have been associated with a variety of physiological activities such as myotropic-, allatostatic-, and pheromonotropic ones, diapause induction, stimulation of cuticular melanization, and diuresis. Some of the members appear to be important neurotransmitters present in the nerves innervating the locust oviduct, the salivary glands, the male accessory glands, and the heart, whereas others are stored in neurohemal organs until release into the hemolymph. Crustacean cardiactive peptide (CCAP) has been identified in locusts as well. It has been found that this peptide is a potent relaxing factor for adipokinetic hormone from the corpus cardiacum.
The purification of a peptide from ovarian extracts which inhibits chymotrypsin biosynthesis in the gut is in progress. This is the equivalent of TMOF-peptides of dipteran insects. In addition, six different protease inhibitors of peptidic nature have been identified from ovarian extracts. With respect to reproduction, several peptides have been identified from extracts of corpora cardiaca of both Locusta and Schistocerca: the different neuroparsins and the Ovary Maturating Parsin (OMP). Finally, a locust ion transport peptide and a salivation stimulating peptide in Schistocerca can be added to this extensive, ever increasing list.
|Publication status: ||published|
|KU Leuven publication type: ||DI|
|Appears in Collections:||Animal Physiology and Neurobiology Section - miscellaneous|