A Database for Insect Neuropeptide Research

Search the database for information about the various species and neuropeptides of interest

Insect Neuropeptides - Capability/CAP2b


The first CAPA peptide was isolated from Manduca sexta based on its ability to increase heart contractions in vitro (Huesmann et al, 1995). It was originally named CAP2b but these peptides are now referred to as CAPA following the discovery of the gene, capability (capa) in Drosophila (see below). Soon after the discovery of the M. sexta peptide, a Drosophila melanogaster CAPA peptide was isolated and shown to stimulate fluid secretion by Malpighian tubules (Davies et al, 1995). The first CAPA-encoding gene (CG15520) was discovered following a BLAST search of the D. melanogaster genome (Kean et al, 2002). Interestingly, the CAPA precursor contains two CAPA peptides (CAPA-1 and CAPA-2), which have a characteristic AFPRVamide C-terminus and one pyrokinin peptide (CAPA-PK or PK-1) with a characteristic FXPRLamide C-terminus. CAPA peptides and pyrokinins activate two distinct receptors and, thus, represent distinct signaling systems. The first CAPA receptor (GPCR) was deorpohanized in D. melanogaster (Iversen et al, 2002; Park et al, 2002). Insect CAPA receptors are evolutionary related to vertebrate neuromedin U receptors (Terhzaz et al, 2012). Pyrokinin type neuropeptides, including CAPA-PK and their receptors are discussed under a separate heading.


The distribution of CAPA peptides is well conserved in insects: they are produced by six large neurosecretory cells in the first three neuromeres of the abdominal ganglia (Kean et al, 2002; Paluzzi and Orchard, 2006). These cells send processes to the perisympathetic organs and peptides are likely released into the circulation from these sites. Hence, these peptides are also referred to as periviscerokinins (PVKs) (Wegener et al, 2002). CAPA is also expressed in neurons of the brain and subesophageal ganglion (Paluzzi and Orchard, 2010; Loi and Tublitz, 2004).


CAPA peptides have been shown to stimulate secretion in Malpighian tubules of several insects (Halberg et al, 2015). This secretion impacts desiccation and cold stress tolerance in D. melanogaster (Terhzaz et al, 2015). Interestingly, Rhodnius prolixus CAPA peptides are anti-diuretic (Paluzzi et al, 2008). Aside from their role in osmoregulation, CAPA peptides are known to be myotropic (Wegener et al, 2002). The function of the CAPA-PK is not known.

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Suggested Reviews

  • Schooley, D. A., Horodyski, F.M., Coast, G.M., 2012. Hormones Controlling Homeostasis in Insects, Insect Endocrinology. Elsevier.
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  • Nässel, D.R., Winther, Å.M.E., 2010. Drosophila neuropeptides in regulation of physiology and behavior. Prog. Neurobiol. 92, 42–104.
    View Review
  • Paluzzi, J.P., 2012. Anti-diuretic factors in insects: the role of CAPA peptides. Gen. Comp. Endocrinol. 176, 300–308.
    View Review


  • Davies, S. A, Huesmann, G.R., Maddrell, S.H., O’Donnell, M.J., Skaer, N.J., Dow, J. A. T., Tublitz, N.J., 1995. CAP2b, a cardioacceleratory peptide, is present in Drosophila and stimulates tubule fluid secretion via cGMP. Am. J. Physiol. 269, R1321–R1326.
  • Halberg, K. A., Terhzaz, S., Cabrero, P., Davies, S. A., Dow, J. A. T., 2015. Tracing the evolutionary origins of insect renal function. Nat. Commun. 6, 6800.
  • Huesmann, G.R., Cheung, C.C., Loi, P.K., Lee, T.D., Swiderek, K.M., Tublitz, N.J., 1995. Amino acid sequence of CAP2b, an insect cardioacceleratory peptide from the tobacco hawkmoth Manduca sexta. FEBS Lett. 371, 311–4.
  • Iversen, A., Cazzamali, G., Williamson, M., Hauser, F., Grimmelikhuijzen, C.J.P., 2002. Molecular cloning and functional expression of a Drosophila receptor for the neuropeptides capa-1 and -2. Biochem. Biophys. Res. Commun. 299, 628–633.
  • Kean, L., Cazenave, W., Costes, L., Broderick, K.E., Graham, S., Pollock, V.P., Davies, S.A., Veenstra, J.A., Dow, J.A.T., 2002. Two nitridergic peptides are encoded by the gene capability in Drosophila melanogaster. Am J Physiol Regul Integr Comp Physiol. 282(5)1297–1307.
  • Loi, P.K., Tublitz, N.J., 2004. Sequence and expression of the CAPA/CAP2b gene in the tobacco hawkmoth, Manduca sexta. J. Exp. Biol. 207, 3681–91.
  • Paluzzi, J.-P., Orchard, I., 2006. Distribution, activity and evidence for the release of an anti-diuretic peptide in the kissing bug Rhodnius prolixus. J. Exp. Biol. 209, 907–915.
  • Paluzzi, J.P., Orchard, I., 2010. A second gene encodes the anti-diuretic hormone in the insect, Rhodnius prolixus. Mol. Cell. Endocrinol. 317, 53–63.
  • Paluzzi, J.P., Russell, W.K., Nachman, R.J., Orchard, I., 2008. Isolation, cloning, and expression mapping of a gene encoding an antidiuretic hormone and other CAPA-related peptides in the disease vector, Rhodnius prolixus. Endocrinology 149, 4638–4646. d
  • Park, Y., Kim, Y.-J., Adams, M.E., 2002. Identification of G protein-coupled receptors for Drosophila PRXamide peptides, CCAP, corazonin, and AKH supports a theory of ligand-receptor coevolution. Proc. Natl. Acad. Sci. U. S. A. 99, 11423–11428.
  • Terhzaz, S., Cabrero, P., Robben, J.H., Radford, J.C., Hudson, B.D., Milligan, G., Dow, J. A. T., Davies, S.-A., 2012. Mechanism and function of Drosophila capa GPCR: a desiccation stress-responsive receptor with functional homology to human neuromedinU receptor. PLoS One 7, e29897.
  • Terhzaz, S., Teets, N.M., Cabrero, P., Henderson, L., Ritchie, M.G., Nachman, R.J., Dow, J. a. T., Denlinger, D.L., Davies, S.-A., 2015. Insect capa neuropeptides impact desiccation and cold tolerance. Proc. Natl. Acad. Sci. 201501518.
  • Wegener, C., Herbert, Z., Eckert, M., Predel, R., 2002. The periviscerokinin (PVK) peptide family in insects: evidence for the inclusion of CAP(2b) as a PVK family member. Peptides 23, 605–11.