1. Crustacean cardioactive peptide (CCAP) of the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae): Molecular characterization, distribution and its potential roles in larva-pupa ecdysis
Yu-Xia Pei, Jin-Jun Wang, Wei Dou, Yan Shi, Tian-Yuan Liu, Guy Smagghe, Hong-Bo Jiang Peptides . 2019 Dec;122:169929. doi: 10.1016/j.peptides.2018.02.007.
Insects must undergo ecdysis for successful development and growth, and the crustacean cardioactive peptide (CCAP) is one of the most important hormone in this process. Here we reported a cDNA encoding for the CCAP precursor cloned from the oriental fruit fly, Bactrocera dorsalis, a most destructive insect pest of agriculture. The CCAP mature peptide (PFCNAFTGC-NH2) of B. dorsalis was generated by post-translational processing and found to be highly comparable with other insects. RT-qPCR showed that mRNA of CCAP in B. dorsalis (BdCCAP) was predominantly expressed in the central nervous system (CNS) and midgut of 3rd-instar larvae. By using immunohistochemical analysis, we also localized the endocrine cells that produce CCAP in the CNS, ring gland and midgut of 3rd-instar larvae of B. dorsalis. The synthetic CCAP mature peptide could induce the expression of mRNA of adipokinetic hormone (AKH), the metabolic neuropeptides in insects. The expression of BdCCAP mRNA in the CNS, but not in the midgut, could be upregulated in the response to the challenge of insect molting hormone, 20-hydroxyecdysone.
2. Identification and developmental expression of mRNAs encoding crustacean cardioactive peptide (CCAP) in decapod crustaceans
N Zmora, S G Webster, Y Zohar, D C Wilcockson, H Dircksen, J S Chung J Exp Biol . 2006 Oct;209(Pt 19):3862-72. doi: 10.1242/jeb.02425.
Full-length cDNAs encoding crustacean cardioactive peptide (CCAP) were isolated from several decapod (brachyuran and astacuran) crustaceans: the blue crab Callinectes sapidus, green shore crab Carcinus maenas, European lobster Homarus gamarus and calico crayfish Orconectes immunis. The cDNAs encode open reading frames of 143 (brachyurans) and 139-140 (astacurans) amino acids. Apart from the predicted signal peptides (30-32 amino acids), the conceptually translated precursor codes for a single copy of CCAP and four other peptides that are extremely similar in terms of amino acid sequence within these species, but which clearly show divergence into brachyuran and astacuran groups. Expression patterns of CCAP mRNA and peptide were determined during embryonic development in Carcinus using quantitative RT-PCR and immunohistochemistry with whole-mount confocal microscopy, and showed that significant mRNA expression (at 50% embryonic development) preceded detectable levels of CCAP in the developing central nervous system (CNS; at 70% development). Subsequent CCAP gene expression dramatically increased during the late stages of embryogenesis (80-100%), coincident with developing immunopositive structures. In adult crabs, CCAP gene expression was detected exclusively in the eyestalk, brain and in particular the thoracic ganglia, in accord with the predominance of CCAP-containing cells in this tissue. Measurement of expression patterns of CCAP mRNA in Carcinus and Callinectes thoracic ganglia throughout the moult cycle revealed only modest changes, indicating that previously observed increases in CCAP peptide levels during premoult were not transcriptionally coupled. Severe hypoxic conditions resulted in rapid downregulation of CCAP transcription in the eyestalk, but not the thoracic ganglia in Callinectes, and thermal challenge did not change CCAP mRNA levels. These results offer the first tantalising glimpses of involvement of CCAP in environmental adaptation to extreme, yet biologically relevant stressors, and perhaps suggest that the CCAP-containing neurones in the eyestalk might be involved in adaptation to environmental stressors.
3. Prothoracicostatic Activity of the Ecdysis-Regulating Neuropeptide Crustacean Cardioactive Peptide (CCAP) in the Desert Locust
Elisabeth Marchal, Jozef Vanden Broeck, Cynthia Lenaerts, Lina Verbakel, Rania Abou El Asrar, Caroline Zandecki, Emilie Monjon, Evert Bruyninckx Int J Mol Sci . 2021 Dec 15;22(24):13465. doi: 10.3390/ijms222413465.
Accurate control of innate behaviors associated with developmental transitions requires functional integration of hormonal and neural signals. Insect molting is regulated by a set of neuropeptides, which trigger periodic pulses in ecdysteroid hormone titers and coordinate shedding of the old cuticle during ecdysis. In the current study, we demonstrate that crustacean cardioactive peptide (CCAP), a structurally conserved neuropeptide described to induce the ecdysis motor program, also exhibits a previously unknown prothoracicostatic activity to regulate ecdysteroid production in the desert locust,Schistocerca gregaria. We identified the locust genes encoding the CCAP precursor and three G protein-coupled receptors that are activated by CCAP with EC50values in the (sub)nanomolar range. Spatiotemporal expression profiles of the receptors revealed expression in the prothoracic glands, the endocrine organs where ecdysteroidogenesis occurs. RNAi-mediated knockdown of CCAP precursor or receptors resulted in significantly elevated transcript levels of severalHalloweengenes, which encode ecdysteroid biosynthesis enzymes, and in elevated ecdysteroid levels one day prior to ecdysis. Moreover, prothoracic gland explants exhibited decreased secretion of ecdysteroids in the presence of CCAP. Our results unequivocally identify CCAP as the first prothoracicostatic peptide discovered in a hemimetabolan species and reveal the existence of an intricate interplay between CCAP signaling and ecdysteroidogenesis.
