Introduction

The first member of the ACP family was isolated from corpora cardiaca extracts of Locusta migratoria (Siegert, 1999). Related peptides were later isolated or identified in Tribolium castaneum (Li et al., 2008), Bombyx mori (Roller et al., 2008), Anopheles gambiae (Kaufmann and Brown, 2006) and Aedes aegypti (Kaufmann et al., 2009); however, these peptides were referred to as adipokinetic hormone (AKH) due to sequence similarity between these peptides. But unlike the classical AKHs which are produced in corpora cardiaca and mobilize lipids from the fat body, ACP are synthesized in the brain and do not produce an adipokinetic effect (Patel et al., 2014; Siegert, 1999). The identification of the first ACP receptors (GPCR) in A. gambiae and T. castaneum revealed that ACP and its receptor comprised an independent signaling system that is related to two other neuropeptide signaling systems, namely AKH and corazonin (Hansen et al., 2010). The ACP signaling system has been lost in Drosophila and Apis mellifera.

Location

ACP-like immunoreactivity has been localized to one pair of large neurons and two pairs of smaller neurons in the brains of T. castaneum and Rhodnius prolixus (Hansen et al., 2010; Patel et al., 2014). ACP seems to have a broader distribution in mosquitoes where AKH/ACP-like immunoreactivity was also detected in neurons in thoracic ganglia.

Function

ACP might function as a neurotransmitter or local neuromodulator, as opposed to a hormone, based on the fact that its receptor is predominantly found in the central nervous system (Hansen et al., 2010; Zandawala et al., 2015). The function of this signaling system in insects is unknown; however, expression analysis suggests that it may play a part in development and/or ecdysis (Hansen et al., 2010; Zandawala et al., 2015).

SeqLogo and Cladogram

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Suggested Reviews

• Hauser, F., Grimmelikhuijzen, C.J.P., 2014. Evolution of the AKH/corazonin/ACP/GnRH receptor superfamily and their ligands in the Protostomia. Gen. Comp. Endocrinol. 209, 35–49. doi:10.1016/j.ygcen.2014.07.009
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References

• Hansen, K.K., Stafflinger, E., Schneider, M., Hauser, F., Cazzamali, G., Williamson, M., Kollmann, M., Schachtner, J., Grimmelikhuijzen, C.J.P., 2010. Discovery of a novel insect neuropeptide signaling system closely related to the insect adipokinetic hormone and corazonin hormonal systems. J. Biol. Chem. 285, 10736–10747. doi:10.1074/jbc.M109.045369
• Kaufmann, C., Brown, M.R., 2006. Adipokinetic hormones in the African malaria mosquito, Anopheles gambiae: Identification and expression of genes for two peptides and a putative receptor. Insect Biochem. Mol. Biol. 36, 466–481. doi:10.1016/j.ibmb.2006.03.009
• Kaufmann, C., Merzendorfer, H., Gäde, G., 2009. The adipokinetic hormone system in Culicinae (Diptera: Culicidae): Molecular identification and characterization of two adipokinetic hormone (AKH) precursors from Aedes aegypti and Culex pipiens and two putative AKH receptor variants from A. aegypti. Insect Biochem. Mol. Biol. 39, 770–781. doi:10.1016/j.ibmb.2009.09.002
• Li, B., Predel, R., Neupert, S., Hauser, F., Tanaka, Y., Cazzamali, G., Williamson, M., Arakane, Y., Verleyen, P., Schoofs, L., Schachtner, J., Grimmelikhuijzen, C.J.P., Park, Y., 2008. Genomics, transcriptomics, and peptidomics of neuropeptides and protein hormones in the red flour beetle Tribolium castaneum. Genome Res. 18, 113–122. doi:10.1101/gr.6714008
• Patel, H., Orchard, I., Veenstra, J. a., Lange, a. B., 2014. The distribution and physiological effects of three evolutionarily and sequence-related neuropeptides in Rhodnius prolixus: Adipokinetic hormone, corazonin and adipokinetic hormone/corazonin-related peptide. Gen. Comp. Endocrinol. 195, 1–8. doi:10.1016/j.ygcen.2013.10.012
• Roller, L., Yamanaka, N., Watanabe, K., Daubnerová, I., Žitňan, D., Kataoka, H., Tanaka, Y., 2008. The unique evolution of neuropeptide genes in the silkworm Bombyx mori. Insect Biochem. Mol. Biol. 38, 1147–1157. doi:10.1016/j.ibmb.2008.04.009
• Siegert, K.J., 1999. Locust corpora cardiaca contain an inactive adipokinetic hormone. FEBS Lett. 447, 237–240. doi:10.1016/S0014-5793(99)00299-9
• Zandawala, M., Haddad, A.S., Hamoudi, Z., Orchard, I., 2015. Identification and characterization of the adipokinetic hormone/corazonin-related peptide signaling system in Rhodnius prolixus. FEBS J. n/a–n/a. doi:10.1111/febs.13366