Crustacean cardioactive peptide

Crustacean cardioactive peptide (CCAP) is a highly conserved, amidated cyclic nonapeptide with the primary structure PFCNAFTGC-NH₂ (ProPheCysAsnAlaPheTyrGlyCys-NH₂) and a disulfide bridge between Cys3 and Cys9. It is found in crustaceans and insects where it behaves as a cardioaccelerator, neuropeptide transmitter for other areas of the nervous system and a hormone. CCAP was first isolated from the pericardial organs of the shore crab Carcinus maenas, where it has a role in regulating heartbeat. It was assumed that this was the peptide's main function and its name reflects this.

Function

As well as C. maenas, CCAP has cardioacceleratory properties in Manduca sexta and Drosophila melanogaster;^[1] it is a highly conserved protein found in species as diverse as moths and fruit flies in addition to the crustacean it was originally identified in. Interestingly, under specific conditions, CCAP has also been shown to induce cardiac reversal in M. sexta and D. melanogaster.^[2][3][4]

Since CCAP was first identified and its possible role suggested, it has been proven it serves many other functions. It regulates release of adipokinetic hormone during sustained flight in L. migratoria. It is also important in metabolism and digestion in other species; CCAP is involved as a hormone in the cockroach Periplaneta americana ^[5][6][7] by upregulating digestive hormones after the insect has fed on nutritional matter. In the crab Cancer borealis CCAP controls passage of food through the forgut by modulating the stomatogastric ganglion's pyloric rhythm.^[8] This suggests CCAP is involved primarily in movement of food along the gut, facilitating digestion by secretion of digestive hormones and increasing flow of blood.

The effects of CCAP on the reproductive organs of females of the species L. migratoria have also been studied. The peptide stimulates the contraction of the oviducts and spermatheca.^[9] There is no CCAP or CCAP-like immunoreactivity shown in the oviduct or the nerves innervating the oviduct so it is probable that CCAP acts as a neurohormone to perform these functions.

CCAP is one of several peptides and hormones to be involved in the moulting process of crustaceans ^[10] and insects.

Effects of lack of CCAP

There have been no mutant individuals of any species found to possess CCAP who have a genetic defect meaning they are not able to produce the peptide. It is likely any such mutation would be lethal. In Drosophila the destruction of CCAP-containing neurons during development causes major changes in and disruptions to timing and behaviour of moulting.^[11]

References

1. ^ R. Nichols, S. Kaminski, E. Walling & E. Zornik (1999). "Regulating the activity of a cardioacceleratory peptide". Peptides 20 (10): 1153–1158. doi:10.1016/S0196-9781(99)00118-7. PMID 10573286. 
2. ^ Dulcis et al., 2001
3. ^ Davide Dulcis, Richard B. Levine & John Ewer (2005). "Role of the neuropeptide CCAP in Drosophila cardiac function". Journal of Neurobiology 64 (3): 259–274. doi:10.1002/neu.20136. 
4. ^ Davide Dulcis & Richard B. Levine (2003). "Innervation of the heart of the adult fruit fly, Drosophila melanogaster". Journal of Comparative Neurology 465 (4): 560–578. doi:10.1002/cne.10869. 
5. ^ J. Stangier, C. Hilbich & R. Keller (1989). "Occurrence of crustacean cardioactive peptide (CCAP) in the nervous system of an insect, Locusta migratoria". Journal of Comparative Physiology B 159 (1): 5–11. doi:10.1007/BF00692677. 
6. ^ Andrew Donini, Hans-Jürgen Agricola & Angela B. Lange (2001). "Crustacean cardioactive peptide is a modulator of oviduct contractions in Locusta migratoria". Journal of Insect Physiology 47 (3): 277–285. doi:10.1016/S0022-1910(00)00112-8. 
7. ^ A. Lange & K. Patel (2005). "Crustacean cardioactive peptide is an important modulator in the stick insect Extradentatum baculum". Regulatory Peptides 129: 191–201. 
8. ^ Heinzel et al., 1997
9. ^ Rosa da Silva & Angela B. Lange (2006). "The association of crustacean cardioactive peptide with the spermatheca of the African migratory locust, Locusta migratoria". Journal of Insect Physiology 52 (4): 399–409. doi:10.1016/j.jinsphys.2006.01.006. PMID 16516227. 
10. ^ J. Sook Chung & Heinrich Dircksen & Simon G. Webster (1999). "A remarkable, precisely timed release of hyperglycemic hormone from endocrine cells in the gut is associated with ecdysis in the crab Carcinus maenas". Proceedings of the National Academy of Sciences 96 (23): 13103–13107. doi:10.1073/pnas.96.23.13103. PMC 23907. PMID 10557280. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=23907. 
11. ^ Park et al., 2003

Further reading

• D. R. Nässel (2002). "Neuropeptides in the nervous system of Drosophila and other insects: multiple roles as neuromodulators and neurohormones". Progress in Neurobiology 68 (1): 1–84. doi:10.1016/S0301-0082(02)00057-6. PMID 12427481.